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Recycled Paper
Broke: Paper recycled internally within a single mill and is typically trimmings and paper that does not meet the specification of the grade (type of paper) being made.
From: Waste (Second Edition) , 2019
Related terms:
- Contaminant
- Raw Material
Energy and Environmental Implications
Ravi Jain Ph.D., P.E. , ... M. Diana Webb M.L.A. , in Handbook of Environmental Engineering Assessment , 2012
Recycled paper can be manufactured relatively easily, with end products competitive in quality to those made from virgin materials. Some difficulties arise from the economics of collection and transportation of waste paper products to centers for reprocessing. However, in 2009 the EPA reported that paper accounted for more than one-third of all of the recyclables collected in the United States with a recycling rate of more than 60 percent.
Shredded wastepaper and other forms of wastepaper products may be utilized as packaging material or as mulches for erosion control, or may form a portion of compost material for soil enrichment. When solid waste is utilized for incineration and heat recovery, the paper and cardboard content provide much of the energy content that is converted to heat.
Estimates of energy savings that can be realized due to recycling of paper products vary greatly. Most studies indicate that energy savings of 7 to 57 percent are possible for paper products such as newsprint, printing paper, packaging paper, and tissue paper. On the other hand, paperboard products require more energy (40 to 150 percent more) when manufactured from recycled material (Office of Technology Assessment [OTA], 1989).
Recovered Paper
Gary M. Scott , in Waste , 2011
3.2 Paper to Other Products
The various processes used to recycled paper into other products are too numerous to describe in detail in a survey article such as this. However, the varieties of products that can be produced are summarized in Table 10.7 . In addition, the processing of recovered paper into usable fiber for papermaking often results in a secondary stream typically termed sludge. Although considered a waste product of the recycling process, this stream often can also be used to produce a number of different products [20] . Paper can also be converted to energy through the use of various combustion technologies that are available. Paper, being an organic material, has a relatively high energy value and can make an excellent fuel. In many cases, the paper (or the sludge from the recycling operation) can be co-fired with other fuels in power boilers and can also be processed as fuel for small-scale (e.g., residential) burners.
TABLE 10.7 . Non-Paper Products from Recovered Paper and Recovered Paper Sludge
Control of Stickies*
Pratima Bajpai , in Recycling and Deinking of Recovered Paper , 2014
13.3.5 Flotation
The removal of stickies from recycled papers by flotation has been reported by several researchers ( Chin, Hipolit, & Longhini, 1996; Chou, 1993; Delagoutte, Brun, & Galland, 2003; Doshi et al., 2000a,b, 2003 ; Hsu & Dauplaise, 1996; Johansson, Wikman, Lindström, & Österberg, 2003; Li, Hipolit, & Longhini, 1996; Ling, 1993a; Nerez, Johnson, & Thompson, 1997 ) . For efficient flotation there is a need to select a flotation aid that minimises any reduction in the surface hydrophobicity of the stickies but still generates a sufficiently stable froth for their flotation ( Ling, 1994 ).
Johansson et al. (2003) have reported that flotation may remove over 70% of micro-stickies in a pulp. A study in a deinking mill showed 66% efficiency for micro-stickies removal ( Delagoutte & Brun, 2005 ). Flotation efficiency depends on the shape, size and surface properties of the stickies and on the hydrodynamic parameters of the flotation. Its main advantage, especially compared with screening, is its ability to remove micro-stickies from the pulp suspension ( Glover, Fitzhenry, & Hoekstra, 2001; Heise et al., 2000; Lee & Kim, 2007 ).
Doshi et al. (2000a,b) and Hsu and Dauplaise (1996) have reported that the nature of the stickies plays an important role. Wax and hot-melt adhesives are quite well removed by flotation, whereas waterborne PSAs are not. This is because these two types of adhesive present different surface properties. The waterborne PSA has a more hydrophilic character than the hot-melt adhesive. Chemical additives may significantly change the ability of flotation to remove stickies. The removal of waterborne PSAs may be improved by the addition of cationic polymers ( Hsu & Dauplaise, 1996 ). These polymers may induce aggregation of the PSA particles into a size range more favourable for flotation removal. Polymer fixation may modify the surface properties, which could also favour interaction between the sticky particles and the air bubbles. Heise et al. (2000) reported that the concentration of surfactant also plays an important role. High surfactant concentration can decrease stickies removal because the initial hydrophobicity of the stickies is reduced owing to high amounts of surfactant, which decrease the attachment force of stickies to air bubbles.
Doshi et al. (2003) studied froth flotation to remove wax and stickies from re-pulped old corrugated container (OCC). Trials at a pilot plant used a conventional OCC stock preparation process with and without froth flotation. Additional washing and DAF were also evaluated. Including flotation in the OCC stock preparation system significantly improved stickies removal and promoted a decrease in the area of wax spots in handsheets. Flotation was more effective in removing wax and stickies than through-flow cleaners. Analysis revealed that three stages of flotation in an OCC system was sufficient and there was no significant loss of yield. Efficient water clarification was achievable using an effective polymer programme and DAF.
Environmental Aspects of Recycling
15.4 health dangers caused by the use of recycled paper.
The German Federal Environmental Office started a project in 1981 to evaluate the applicability of recycled paper in modern office use. No significant differences were found between paper from primary sources and recycled paper in its use as writing, copying or printing paper. Like paper from primary sources, quality differences among recycled paper depend more on the quality of wastepaper, the production process, the additives used and the finishing process. For very high-quality printing, few problems were observed with recycled paper. Small remaining particles of former glue, lacquer or synthetics were found to affect the printing quality.
Wastepaper can sometimes contain pathogens that are expected to cause diseases. So, there was apprehension that recycled paper might be hygienically intolerable. However, during production of recycled paper, the paper passes through certain stages where it is heated to high temperatures and so it is practically sterilised. Investigations in Germany showed that recycled paper is hygienically acceptable even for food packaging. A few years ago there were some reports that recycled paper contained a higher amount of formaldehyde, which degases during use. Formaldehyde can come from some special paper and board qualities, where it is used during the production process. However, because these papers are very rare in Germany (the situation might be different in other countries) and mixed up with other formaldehyde-free papers during the recycling process, formaldehyde is hardly traceable in recycled paper. Its content is well below any limit set by the environmental legislation. However, contamination of paper by dioxins and furans seems to be more serious ( Vest, 2000 ). During bleaching with chlorine, several organic chlorine compounds are formed which include dioxins and furans. Dioxins in paper can also originate from wood preservation chemicals or certain printing colours apart from bleaching. It was found that some chlorine-bleached papers contain 30–50 ng of toxicity equivalent (TE) per kilogram (ng TE/kg) of dioxins and furans. Chlorine-free bleached paper, on the other hand, often contains less than 1 ng TE/kg. During the recycling of paper, chlorine-bleached paper and chlorine-free bleached paper are mixed. Because no chlorine bleaching is applied during the production of recycled paper, the intake of dioxins from chlorine-bleached paper will be diluted by the other more or less dioxin-free papers. Nowadays, this results in a dioxin content of some 3–4 ng TE/kg for standard recycling paper. This figure is far below any limit given by environmental legislation. The dioxin and furan content in recycled paper has decreased gradually during the past few years since the paper industry has moved over more and more to chlorine-free bleaching processes. At the beginning of paper recycling, sometimes 50–60 ng TE/kg were measured in recycled paper. When the reasons for the contamination were researched, certain sources of dioxins were identified. For example, carbon paper was identified as a major source of chloroparaffins, and some cardboard boxes for exotic fruits contained reasonable amounts of pentachlorophenol (PCP). Both substances may form dioxins and furans during the papermaking process.
In developing countries, the situation may be different from industrialised countries. The paper industry might still use chlorine-bleaching processes. Additionally, environmental control about the use of certain chlorine-containing chemicals – herbicides, fungicides, wood protection chemicals, paper and cardboard, etc. – might not be as severe. So, there are more possibilities for the intake of dioxins and furans into the recycling paper production. However, dioxin and furan contents in the vicinity of 60 ng TE/kg are not dangerous and meet accepted environmental standards. As regards the contamination of recycled paper, heavy metals, in particular lead, has been discussed. During former printing processes that used printing types from lead, traces of lead were deposited together with the ink. There was apprehension that during recycling, in particular, if paper was recycled several times, lead might accumulate in the recycled paper. Studies have shown that the lead content of such recycled paper never exceeded any critical limit. At the same time, deinking technology was developed which removed most of the lead together with the ink. Although enriched in deinking sludges, lead was never a problem. The concentration of lead was far below the limits of, for example, lead allowed in sewage sludge that is suitable as fertiliser on farmland. The heavy metal problem disappeared with the disappearance of old-fashioned printing technologies ( Vest, 2000 ). Nowadays, deinking sludges can be landfilled on normal landfill sites or can be incinerated in normal municipal solid waste incinerators without any special precaution.
Valorization of industrial solid waste through novel biological treatment methods – integrating different composting techniques
Jayeeta Hazarika , Meena Khwairakpam , in Advanced Organic Waste Management , 2022
6.3.1 Composting of paper mill sludge
Literature on composting of paper mill sludge suggests more metabolic activity in mixed (primary, secondary and recycled paper mill sludge) form of sludge indicating attainment of high temperature as compared to the primary sludge alone ( Table 6.1 ). This condition was further improved by the addition of nitrogenous supplements such as chicken litter, slaughter wastes also including ammonium nitrate, ammonium sulphate and certain other nutrients. The main reason behind this distinction is the nitrogen content natively present in secondary and recycled (partially digested) sludge which maintains the balance and C/N ratio to optimum levels. However, in case of primary sludge the levels of recalcitrant cellulosic components are much higher accompanied by very low levels of nitrogen. The cellulosic materials are not self-sufficient as substrates for microbial degradation and witnesses slow decomposition ( Alexander, 1977 ). Therefore, composting of primary sludge solely is pretty difficult and there is a need to devise techniques for efficient composting of such waste products. Degradation is better in combined sludge but as the level of generation of primary sludge is much higher, more importance should be dedicated to it. Though composting of primary sludge as a sole substrate has been experimented in few studies, it was supplemented with nutrients. Addition of nitrogen supplements whereas has been reported to increase electrical conductivity and also suffers high operating costs, odor problems, corrosion. Therefore, previous studies focused on extensive non-sustainable use of chemical fertilizers such as urea, potash, ammonium nitrate and phosphate rock to degrade a potential soil ameliorater. Therefore, the whole sustainable idea of composting wastes to produce organic fertilizers remains elusive. So, there is need for more detailed study on enhancing the degradative capability of primary sludge without incorporation of much chemical supplements. Therefore, in order to achieve good primary paper mill sludge composting characteristics, devising new techniques of biodegradation needs to be explored.
Table 6.1 . Composting of paper mill sludge in the yester years.
Bioseparation Engineering
T. Funazukuri , ... M. Goto , in Progress in Biotechnology , 2000
1 INTRODUCTION
A large amount of cellulosic materials involved in municipal solid wastes have been disposed of by incineration and landfill, although some of them are utilized as recycled paper , fuel, packing materials etc. In order to decrease the environmental impact and increase the recycle rate of cellulosic wastes, the useful conversion process for cellulose to valuable materials has been required. One of the promising processes is hydrolysis of cellulose followed by fermentation to produce ethanol. A large number of studies on hydrolysis of cellulose have been made with various acids or enzymes at low pressures. Recently, Adschiri et al. (1) reported that cellulose was effectively hydrolyzed by contacting subcritical or supercritical water without any additives at extremely short residence time. The results are very attractive, but the engineering problems in both the feed of the sample and the attainability of short residence times have arisen. In this study in order to overcome these, the reaction temperature is decreased by adding the small amount of acids, and then the residence times are increased. The effects of the additives on cellulose conversion and glucose yields are studied.
Gary M. Scott , in Waste (Second Edition) , 2019
2.2 Recovered Paper Collection
Recovered paper collection is done in a number of different ways, depending on the type of paper being collected and the source of the paper. In general, preconsumer recycled paper is easier to collect as it tends to be concentrated in specific manufacturing locations and also tends to be much more homogeneous and less contaminated. These collections, often of the form of cuttings, trimmings, and over issues, are typically baled and packaged directly at the collection site with little additional processing needed [21] .
The recovery of postconsumer recycled paper is more difficult as the sources tend to be less concentrated and the paper is often mixed in terms of the types of paper as well as being mixed with other waste. Some postconsumer waste paper grades, such as sorted office paper (see Table 14.2 ), can be relatively clean as they are collected in dedicated locations, baled, and collected. Often, these collections can be sold to the recycled fiber users directly with little additional processing.
Additional postconsumer recycled paper is collected through municipal collection systems. These papers tend to be the least homogeneous and require the greatest amount of processing and handling to be usable as recovered paper. The collection of these types of paper can be done through a number of different mechanisms including pickup containers, drop-off containers, curbside collection, and other systems. While curbside collection is the most convenient for the consumer, it results in an extremely diffuse source. The effectiveness of curbside recycling in relation to population density can be easily seen with the variation of access across the United States. Heavily populated areas (population greater than 250,000) have much greater access to recycling programs than less populated or unincorporated areas. Overall in the United States in 2015, 73% of the population has access to curbside recycling, 21% has access to drop-off recycling programs, and 94% has access to some type of recycling program [22] . This access has increased over the past 10 years.
These collection methods depend heavily on the final user separating the paper from the MSW stream to be effective. This can be done fairly easily as paper is by far the largest part of the MSW stream before recycling ( Fig. 14.2 ) provided homeowners and businesses separate the recyclable material prior to collection [8] . The recovery of paper after being mixed with other waste is a much more difficult prospect. In this case, the type and amount of contamination can significantly increase the processing costs of using the recovered paper, perhaps beyond economic feasibility. In addition, consideration must also be given to the fate of the balance of the MSW stream. While there is an advantage to remove the paper if the collected MSW is destined for a landfill, separation of paper from MSW that will be incinerated for energy production will reduce the energy value of the material, as paper is a significant portion of the combustible material.
Biotechnology in the Pulp and Paper Industry
Ali R. Esteghlalian , ... John N. Saddler , in Progress in Biotechnology , 2002
1.1. Cellulases in Processing of Natural Fibers
Cellulase enzymes have a wide variety of applications in the bioprocessing of natural fibers, such as the hydrolysis of cellulose to fermentable sugars for ethanol production [ 1 ]; deinking of recycled paper [ 2,3 ]; biopolishing of cotton fabrics to enhance softness and appearance, and treatment of recycled fibers to restore fiber swelling and flexibility lost during operations [ 2–5 ]. It has also been shown that cellulase treatment in combination with physical refining can provide a means for altering the morphology of coarse wood fibers (e.g., Douglas fir) to produce finer paper products [ 6 ].
Enzyme-mediated degradation of cellulose is the core phenomenon in all the aforementioned applications. Depending on the process objective, the extent of cellulose degradation and the properties of the resulting products can be controlled by adjusting the treatment parameters (treatment time, enzyme loading and the composition of cellulase mixture) ( Table 1 ). While relatively high loads of complete cellulases will be required to achieve complete hydrolysis of cellulose in biomass-to-ethanol operations, the papermaking and textile industries take advantage of both complete and individual cellulase components to achieve partial cellulose hydrolysis and improve paper and fabric properties.
Table 1 . The role of major process variables in the treatment of natural fibers with cellulase enzymes
For example, complete cellulase mixtures are used in depilling/cleaning of cotton fabrics, whereas pure endoglucanase (EG) or EG-rich mixtures are used to produce aged and soft fabrics demanded by the fashion market [ 1,7 ]. It is postulated that during depilling, enzymes attack and hydrolyze the microfibrils that hold the pills to the fiber surface, whereas in fabric ageing, the attack occurs on the fiber surface and results in fiber defibrillation [ 7 ]. The accompanying mechanical action removes the dye bound to the surface and imparts an aged appearance [ 7 ]. In both cases, the accessibility of cellulose surface to the enzymes plays a key role. Commercial cellulases have also been shown to enhance the whiteness, brightness and color characteristics of cotton fabrics [ 8 ].
In comparison with crude cellulase preparations, the cellulase mono-components were shown to be more effective in enhancing fiber collapsibility while circumventing the yield and strength losses, although they decreased individual fiber integrity [ 9 ]. The partial hydrolysis of some cell wall components weaken the fibers' natural integrity and “peel off” the cell wall layers, thereby enhancing the swelling and flexibility of the fibers. It has also been shown that cellulase treatment can increase the handsheet density and tensile strength of long, strong subalpine fir fibers, however, improvements in the tensile strength was dependent on the degree of fiber coarseness in the original pulp [ 9 ].
Cellulases have also been used to remove ink from papers and to enhance papermaking properties of recycled fibers. Enzymatic deinking can lower the need for deinking chemicals and reduce the adverse environmental impacts of the paper industry [ 10 ]. While in general, enzymatic deinking results in little or no loss in fiber strength [ 10–14 ], the overall effectiveness of the treatment depends on variables, such as toner quality and type, the type and amount of sizing, and the presence of other contaminants [ 15,16 ]. Although strength properties have not been compromised substantially, the excessive use of enzymes must be avoided [ 14 ], as it has been shown that significant hydrolysis of the fines [ 14,17–21 ] could reduce the bondability of the fibers [ 22–29 ].
Mechanistically, it has been postulated that improvements in dewatering and deinking of various pulps results in the peeling of the individual fibrils and bundles, which have a high affinity for the surrounding water and ink particles [ 30 ]. It appears that cellulase treatments can release ink particles bound to the fines and to the fiber, and enhance the removal of ink by flotation [ 31 ]. While cellulases clearly enhance the deinking process, the mechanical agitation still plays a critical role in the efficiency of ink removal [ 31–33 ]. These claims are consistent with similar findings concerning enzymatic stone washing of cotton fabrics, which indicated that enzymatic treatments in combination with mechanical agitation improve the efficacy of the process [ 34–35 ]. During textile bioprocessing, the small fiber ends protruding from the yarn are weakened by the action of the enzymes [ 36,37 ], while the simultaneous mechanical action completes the process by releasing the short fibers from the surface of the fabric [ 35 ] similar to the phenomenon occurring during deinking.
Refining, a mechanical action necessary for improving the physical properties of primary or secondary fibers, can generate small particles (fines) that can reduce the drainage rate of pulps during papermaking operations. Cellulases seem to preferentially attack and hydrolyze the fines produced during the refining operation, and therefore, improve the pulp's drainage property. For example, one mill trial revealed that the freeness of the refined stock could be increased to allow greater incorporation of the recycled fibers into a corrugating medium [ 38 ]. Other mill trials on recycled kraft fibers and old corrugated container pulp successfully demonstrated savings in refining energy requirements [ 39 ].
The retention of water by fibers during refining reduces the softening temperature of hemicellulose and lignin present between adjacent fibers and weakens inter-fiber bonding, hence improving the separation of fibers from one another and reducing the energy consumption during refining operation [ 40 ]. It ahs been shown that cellobiohydrolase I, a cellulase monocomponent, could selectively reduce the crystallinity of cellulose and subsequently produce more amorphous material with a higher affinity for water. Treatment with CBH I was able to reduce the refining energy demands by 40% [ 40 ].
While applications of cellulases in the textile and pulp and paper industry revolve around low dosage, partial cellulose hydrolysis by full or individual cellulase components, the biomass utilization operations require the use of complete cellulase systems at relatively high loading to achieve complete cellulose hydrolysis. The objective is to maximize the yield of glucose recovery and its fermentation to ethanol. Biomass-derived ethanol, either in pure form or in blend with gasoline, can be used as a renewable fuel by the transportation sector.
Introduction*
1.3 benefits of recycling.
Recycling of waste paper has several benefits, both for humans and the earth ( Bajpai, 2006; Putz, 2006; Sappi, 2011 ).
The process of recycling protects the environment. Using recycled paper to make new paper reduces the number of trees that are cut down, conserving natural resources. Every tonne of recycled fibre saves an average of 17 trees plus related pulping energy. In some instances, recycling services are cheaper than trash-disposal services. Recycling paper saves landfill space and reduces the amount of pollution in the air from incineration. Businesses can promote a positive company and community image by starting and maintaining a paper-recycling programme. Parents can promote a clean environment and a healthy lifestyle to their children by teaching them about the benefits of recycling paper.
By using waste paper to produce new paper, disposal problems are reduced. The savings are at least 30,000 L of water, 3000–4000 kW h of electricity and 95% of air pollution for every tonne of paper used for recycling. Also, 3 yd 3 of landfill space are saved. And in many cases, recovering paper for recycling can save communities money that they would otherwise have to spend for disposal.
Compared with virgin paper, producing recycled paper involves between 28% and 70% less energy consumption. Also, less water is used. This is because most of the energy used in papermaking is the pulping needed to turn wood into paper.
Recycled paper produces fewer polluting emissions to air and water. Recycled paper is not usually re-bleached and, when it is, oxygen rather than chlorine is usually used. This reduces the amount of dioxins that are released into the environment as a by-product of the chlorine bleaching processes.
High-grade papers can be recycled several times, providing environmental savings every time.
Producing recycled paper actually generates between 20% and 50% fewer carbon dioxide emissions than paper produced from virgin fibres.
Because used paper is usually collected fairly near to recycling plants, manufacturing recycled paper reduces transport and carbon dioxide emissions.
Recycling paper reduces the volume of waste while helping to boost the local economy through the collection and sorting of waste paper.
Waste paper pulp requires less refining than virgin pulp and may be co-refined with hardwood pulp or combined hardwood/softwood pulps without significant damage
The kinds of deinked pulp suitable for use in printing papers usually impart special properties to the finished papers compared with papers made from wood pulp, such as increased opacity, less curling tendency, less fuzziness, better formation, etc.
Not all effects of recycling paper are positive ones. Recycling mills are known for producing sludge, which is the runoff that includes ink, adhesives and other unusable material removed from the usable fibre. But according to Conservatree, the materials in sludge would still end up in landfills or incinerator emissions if the paper was not recycled, and recycling mills have developed environmentally controlled methods of handling sludge. In some cases, paper recycling has real environmental and economic benefits and some cases it does not. Depending on the circumstances, paper recycling may use more resources than it saves, or cost too much to be of much benefit, depending on the circumstances. A lot depends upon the type of recovered paper being used and the type of recycled paper being produced. Because wood and recovered paper are excellent fibre sources and because advanced recycling technology allows papermakers to use recycled fibre in new ways, the possibilities for using recycled fibre in today’s paper products are greater than ever. About 38% of the raw material used in US paper mills is recovered paper. In many cases, the quality of recycled paper products is very close to the quality of those made from new fibre. Paper manufacturers must choose the raw materials best suited to make their products. In some cases, new wood fibre is the better choice; in others, recycled fibre is preferable. It is up to the manufacturer to decide how to use the fewest possible resources to make quality products that meet consumers’ needs.
Sustainability of Municipal Solid Waste Management
Dr. Salah M. El-Haggar PE, PhD , in Sustainable Industrial Design and Waste Management , 2007
Recycled paper products
Due to technological developments, there is an increasing variety of new applications for recovered paper both within and outside the paper and board industry such as newsprint as well as printing and writing paper ( Hyvärinen, 2001 ). Recycled paper and cardboards are widely used in Egypt in the manufacture of local craft and cardboard as well as board egg trays ( El-Haggar, 2001a ).
In 1994 the American University in Cairo (AUC) started a paper recycling subprogram within a program called “Industrial/Municipal Waste Management Program, IMWMP”. A model of a paper recycling machine was designed and manufactured at AUC to test different factors affecting the recycling process and quality of produced paper as shown in Figure 5.9 . A deinking system was also incorporated into the design to remove the ink mechanically from the recycled paper pulp as shown in Figure 5.10 . Overall, the system proved to be highly effective in producing quality paper and the focus of the research has turned to optimize the paper recycling process. Different raw materials were tested to optimize the mixing ratio for better product quality.
FIGURE 5.9 . Schematic drawing of paper pulping (beater) machine
FIGURE 5.10 . Schematic drawing of air injection flotation cell
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Recycling the waste of paper into usable board
- 1 Material Engineering, Engineering College, Basrah University , Iraq .
b) [email protected]
- Usama J. Naeem
- Safaa A. S. Almtori
ABSTRACT The recycling of waste paper conserves our natural resources and will retrieve environmental quality. Concentrate on recycling waste paper into the usable board will benefit plants and the environment. This research depends on the investigation of manufacturing of usable board from waste paper. This manufacturing board can use instead of the board which manufactures from ordinary wood. On the other hand, it protected the forest and eliminates waste that harms the environment. This research illustrates the efficiency of our manufacturing board material by using mechanical tests and comparing it with a board manufactured by two types of ordinary wood and Medium-density fiberboard (MDF). Also, comparing the heat isolation between them. In this project, we use three types of waste paper: white, yellow envelope and newspaper. This waste paper produced our new board material. Our samples were manufactured with dimensions of 10*10 cm and 2 cm thickness. Different amount of waste paper and white glue was investigated to produce a batter board. Our study for the manufactured board materials demonstrated that a white paper sample was the battery on hardness and tensile test. However, yellow envelope samples were more efficient in the impact test than other samples. Moreover, yellow envelope samples were the better one between our samples in heat isolation. Mainly, the waste of paper and white glue was the cheapest to manufacture boards than using ordinary wood. false
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Home > Books > Environmental Management in Practice
The Effects of Paper Recycling and its Environmental Impact
Submitted: November 24th, 2010 Published: July 5th, 2011
DOI: 10.5772/23110
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Environmental Management in Practice
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Author Information
Iveta čabalová *.
- Technical University in Zvolen,Faculty of Wood Sciences and Technology, Slovakia
František Kačík
Anton geffert *, danica kačíková *.
*Address all correspondence to:
1. Introduction
It is well known the paper production (likewise the other brands of industry) has enormous effects on the environment. The using and processing of raw materials has a variety of negative effects on the environment.
At the other hand there are technologies which can moderate the negative impacts on the environment and they also have a positive economical effect. One of these processes is the recycling, which is not only the next use of the wastes. The main benefit of the recycling is a double decrease of the environment loading, known as an environmental impact reducing. From the first view point, the natural resources conserves at side of the manufacturing process inputs, from the second view point, the harmful compounds amount leaking to the environment decreases at side of the manufacturing process outputs.
The paper production from the recycled fibers consumes less energy; conserves the natural resources viz. wood and decreases the environmental pollution. The conflict between economic optimization and environmental protection has received wide attention in recent research programs for waste management system planning. This has also resulted in a set of new waste management goals in reverse logistics system planning. Pati et al. (2008 ) have proposed a mixed integer goal programming (MIGP) model to capture the inter-relationships among the paper recycling network system. Use of this model can bring indirectly benefit to the environment as well as improve the quality of waste paper reaching the recycling unit.
In 2005, the total production of paper in Europe was 99.3 million tonnes which generated 11 million tonnes of waste, representing about 11% in relation to the total paper production. The production of recycled paper, during the same period, was 47.3 million tonnes generating 7.7 million tonnes of solid waste (about 70% of total generated waste in papermaking) which represents 16% of the total production from this raw material ( CEPI 2006 ).
The consumption of recovered paper has been in continuous growth during the past decades. According to the Confederation of European Paper Industries (CEPI), the use of recovered paper was almost even with the use of virgin fiber in 2005. This development has been boosted by technological progress and the good price competitiveness of recycled fiber, but also by environmental awareness – at both the producer and consumer ends – and regulation that has influenced the demand for recovered paper. The European paper industry suffered a very difficult year in 2009 during which the industry encountered more down-time and capacity closures as a result of the weakened global economy. Recovered paper utilisation in Europe decreased in 2009, but exports of recovered paper to countries outside CEPI continued to rise, especially to Asian markets (96.3%). However, recycling rate expressed as “volume of paper recycling/volume of paper consumption” resulted in a record high 72.2% recycling rate after having reached 66.7% the year before ( Fig. 1 ) ( Hujala et al. 2010 ;CEPI 2006; European Declaration on Paper Recycling 2010; Huhtala& Samakovlis 2002 ; CEPI Annual Statistic 2010).
European paper recycling 1995-2009 in million tonnes (European Declaration on Paper Recycling 2006 – 2010, Monitoring Report 2009 (2010) (www.erpa.info)
Recycling is not a new technology. It has become a commercial proposition since Matthias Koops established the Neckinger mill, in 1826, which produced white paper from printed waste paper. However, there were very few investigations into the effect of recycling on sheet properties until late 1960's. From then until the late 1970's, a considerable amount of work was carried out to identify the effects of recycling on pulp properties and the cause of these effects ( Nazhad 2005 ; Nazhad& Paszner 1994 ). In the late 1980's and early 1990's, recycling issues have emerged stronger than before due to the higher cost of landfills in developed countries and an evolution in human awareness. The findings of the early 70's on recycling effects have since been confirmed, although attempts to trace the cause of these effects are still not resolved ( Howard &Bichard 1992 ).
Recycling has been thought to reduce the fibre swelling capability, and thus the flexibility of fibres. The restricted swelling of recycled fibres has been ascribed to hornification, which has been introduced as a main cause of poor quality of recycled paper ( Scallan&Tydeman 1992 ). Since 1950's, fibre flexibility among the papermakers has been recognized as a main source of paper strength. Therefore, it is not surprising to see that, for over half a century, papermakers have supported and rationalized hornification as a main source of tensile loss due to drying, even though it has never been fully understood ( Sutjipto et al. 2008 ).
Recycled paper has been increasingly produced in various grades in the paper industry. However, there are still technical problems including reduction in mechanical strength for recycled paper. Especially, chemical pulp-origin paper, that is, fine paperrequires a certain level of strength. Howard & Bichard (1992 ) reported that beaten bleachedkraft pulp produced handsheets which were bulky and weak in tensile and burst strengthsby handsheet recycling. This behaviour could be explained by the reduction in re-swelling capability or the reduction in flexibility of rewetted pulp fibers due to fiber hornification and, possibly, by fines loss during recycling processes, which decrease both total bondingarea and the strength of paper ( Howard 1995 ; Nazhad&Paszner 1994 ; Nazhad et al. 1995 ; Khantayanuwong et al.2002 ; Kim et al. 2000 ).
Paper recycling is increasingly important for the sustainable development of the paper industry as an environmentally friendly sound. The research related to paper recycling is therefore increasingly crucial for the need of the industry. Even though there are a number of researches ascertained the effect of recycling treatment on properties of softwood pulp fibres ( Cao et al. 1999 ; Horn 1975 ; Howard&Bichard 1992 ; Jang et al. 1995 ), however, it is likely that hardwood pulp fibres have rarely been used in the research operated with recycling treatment. Changes in some morphological properties of hardwood pulp fibres, such as curl, kink, and length of fibre, due to recycling effects also have not been determined considerably. This is possibly because most of the researches were conducted in the countries where softwood pulp fibres are commercial extensively ( Khantayanuwong 2003 ). Therefore, it is the purpose of the present research to crucially determine the effect of recycling treatment on some important properties of softwood pulp fibres.
2. Alterations of pulp fibres properties at recycling
The goal of a recycled paper or board manufacturer is to make a product that meets customers΄ specification and requirements. At the present utilization rate, using recycled fibres in commodity grades such as newsprint and packaging paper and board has not caused noticeable deterioration in product quality and performance ( Čabalová et al. 2009 ). The expected increase in recovery rates of used paper products will require a considerable consumption increase of recycled fibres in higher quality grades such as office paper and magazine paper. To promote expanded use of recovered paper, understanding the fundamental nature of recycled fibres and the differences from virgin fibres is necessary.
Essentially, recycled fibres are contaminated, used fibres. Recycled pulp quality is, therefore, directly affected by the history of the fibres, i.e. by the origins, processes and treatments which these fibres have experienced.
McKinney (1995) classified the history into five periods:
fibre furnish and pulp history
paper making process history
printing and converting history
consumer and collection history
recycling process history.
To identity changes in fibre properties, many recycling studies have occurred at laboratory. Realistically repeating all the stages ofthe recycling chain is difficult especially when including printing and deinking. Some insight into changes in fibre structure, cell wall properties, and bonding ability is possible from investigations using various recycling procedures, testing methods, and furnishes.
Mechanical pulp is chemically and physically different from chemical pulp then recycling effect on those furnishes is also different. When chemical fibres undergo repeated drying and rewetting, they are hornified and can significantly lose their originally high bonding potential ( Somwand et al. 2002 ; Song & Law 2010 ; Kato & Cameron 1999 ; Bouchard & Douek 1994 ; Khantayanuwong et al. 2002 ; Zanuttini et al. 2007 ; da Silva et al. 2007 ). The degree of hornification can be measured by water retention value (WRW) ( Kim et al. 2000 ). In contrast to the chemical pulps, originally weakermechanical pulps do not deteriorate but somewhat even improve bonding potential during a corresponding treatment. Several studies( Maloney et al. 1998 ; Weise 1998 ; Ackerman et al. 2000 ) have shown good recyclability of mechanical fibres.
Adámková a Milichovský (2002 ) present the dependence of beating degree ( SR –Schopper-Riegler degree) and WRV from the relative length of hardwood and softwood pulps. From their results we can see the WRV increase in dependence on the pulp length alteration is more rapid at hardwood pulp, but finally this value is higher at softwood pulps. Kim et al. (2000 ) determined the WRV decrease at softwood pulps with the higher number of recycling (at zero recycling about cca 1.5 g/g at fifth recycling about cca 1.1 g/g).Utilisation of the secondary fibres to furnish at paper production decrease of the initial need of woody raw (less of cutting tress) but the paper quality is not significantly worse.
2.1. Paper recycling
The primary raw material for the paper production is pulps fibres obtaining by a complicated chemical process from natural materials, mainly from wood. This fibres production is very energy demanding and at the manufacturing process there are used many of the chemical matters which are very problematic from view point of the environment protection. The suitable alternative is obtaining of the pulp fibres from already made paper. This process is far less demanding on energy and chemicals utilisation. The paper recycling, simplified, means the repeated defibring, grinding and drying, when there are altered the mechanical properties of the secondary stock, the chemical properties of fibres, the polymerisation degree of pulp polysaccharidic components, mainly of cellulose, their supramolecular structure, the morphological structure of fibres, range and level of interfibres bonds e.g.. The cause of above mentioned alterations is the fibres ageing at the paper recycling and manufacturing, mainly the drying process.
At the repeat use of the secondary fibres, it need deliberate the paper properties alter due to the fiber deterioration during the recycling, when many alteration are irreversible. The alteration depth depends on the cycle’s number and way to the fibres use. The main problem is the decrease of the secondary pulp mechanical properties with the continuing recycling, mainly the paper strength ( Khantayanuwong et al. 2002 ; Jahan 2003 ; Hubbe & Zhang 2005 ; Garg & Singh 2006 ; Geffertová et al. 2008 ; Sutjipto et al. 2008 ). This decrease is an effect of many alterations, which can but need not arise in the secondary pulp during the recycling process. The recycling causes the hornification of the cell walls that result in the decline of some pulp properties. It is due to the irreversible alterations in the cells structure during the drying ( Oksanen et al. 1997 ; Kim et al. 2000 ; Diniz et al. 2004 ).
The worse properties of the recycled fibres in comparison with the primary fibres can be caused by hornification but also by the decrease of the hydrophilic properties of the fibres surface during the drying due to the redistribution or migration of resin and fat acids to the surface ( Nazhad& Paszner 1994 ; Nazhad 2005 ). Okayama (2002 ) observed the enormous increase of the contact angle with water which is related to the fiber inactivation at the recycling. This process is known as „irreversible hornification“.
Paper recycling saves the natural wood raw stock, decreases the operation and capital costs to paper unit, decrease water consumption and last but not least this paper processing gives rise to the environment preservation (e.g. 1 t of waste paper can replace cca 2.5 m 3 of wood).
A key issue in paper recycling is the impact of energy use in manufacturing.Processing waste paper for paper and board manufacture requires energy that isusually derived from fossil fuels, such as oil and coal. In contrast to the productionof virgin fibre-based chemical pulp, waste paper processing does not yield a thermalsurplus and thus thermal energy must be supplied to dry the paper web. If,however, the waste paper was recovered for energy purposes the need for fossil fuelwould be reduced and this reduction would have a favourable impact on the carbondioxide balance and the greenhouse effect. Moreover, pulp production based onvirgin fibres requires consumption of round wood and causes emissions of air-pollutingcompounds as does the collection of waste paper. For better paper utilization, an interactive model, the Optimal Fibre Flow Model, considersboth a quality (age) and an environmental measure of waste paper recycling was developed ( Byström&Lönnstedt 1997 ).
2.1.1. Influence of beating on pulp fibres
Beating of chemical pulp is an essential step in improving the bonding ability of fibres. The knowledge complete about beating improves the present opinion of the fibres alteration at the beating. The main and extraneous influences of the beating device on pulps were defined.The main influences are these, each of them can be improve by the suitable beating mode, but only one alteration cannot be attained. Known are varieties of simultaneous changes in fibres, such as internal fibrilation, external fibrilation, fiber shortening or cutting, and fines formation ( Page 1989 ; Kang & Paulapuro 2006a ; Kang & Paulapuro 2006c ).
Freeing and disintegration of a cell wall affiliated with strongswelling expressed as an internal fibrilation and delamination. The delamination is a coaxial cleavage in the middle layer of the secondary wall.It causes the increased water penetration to the cell wall and the fibre plasticizing.
External fibrillation and fibrils peeling from surface, which particularly or fully attacks primary wall and outside layers of secondary walls.Simultaneously from the outside layers there arecleavage fibrils, microfibrils, nanofibrils to the macromolecule of cellulose and hemicelluloses.
Fibres shortening in any place in any angle-wise across fibre in accordance with loading, most commonly in weak places.
Concurrently the main effects at the beating also the extraneous effects take place, e.g. fines making, compression along the fibres axis, fibres waving due to the compression. It has low bonding ability and it influences the paper porosity,stocks freeness ( Sinke&Westenbroek 2004 ).
The beating causes the fibres shortening, the external and internal fibrillation affiliated with delamination and the fibres plasticizing. The outside primary wall of the pulp fibre leaks water little, it has usually an intact primary layer and a tendency to prevent from the swelling of the secondary layer of the cell wall. At the beating beginning there are disintegrated the fibre outside layers (P and S1), the fibrilar structure of the fibre secondary layer is uncovering, the water approach is improving, the swelling is taking place and the fibrillation process is beginning. The fibrillation process is finished by the weaking and cleavaging of the bonds between the particular fibrils and microfibrils of cell walls during the mechanical effect and the penetration into the interfibrilar spaces, it means to the amorphous region, there is the main portion of hemicelluloses.
Češek& Milichovský (2005 ) showed that with the increase of pulp beating degree the standard rheosettling velocity of pulp decreases more at the fibres fibrillation than at the fibres shortening.
Refining causes a variety of simultaneous changes in the fiber structure, such as internal fibrillation, external fibrillation and fines formation. Among these effects, swelling is commonly recognized as an important factor affecting the strength of recycled paper ( Kang & Paulapuro 2006d ).
Scallan & Tigerstrom (1991 ) observed the elasticity modulus of the long fibres from kraft pulp during the recycling. Flexibility decrease was evident at the beating degree decrease ( SR), and also with the increase of draining velocity of low-yield pulp.
Alteration of the breaking length of the paper sheet drying at the temperature of 80, 100 a 120°C during eightfold recycling
The selected properties of the pulp fibres and the paper sheets during the process of eightfold recycling at three drying temperatures of 80, 100, 120°C.
From the result on Fig. 2 we can see the increase of the pulp fibres active surface takes place during the beating process, which results in the improve of the bonding and the paper strength after the first beating. It causes also the breaking length increase of the laboratory sheets. The secondary fibres wear by repeated beating, what causes the decrease of strength values ( Table 1 ).
The biggest alterations of tear index ( Fig. 3 ) were observed after fifth recycling at the bleached softwood pulp fibres. The first beating causes the fibrillation of the outside layer of the cell wall, it results in the formation of the mechanical (felting) and the chemical bonds between the fibres. The repeated beating and drying dues, except the continuing fibrillation of the layer, the successive fibrils peeling until the peeling of the primary and outside secondary layer of the cell wall. It discovers the next non-fibriled layer S2 (second, the biggest layer of the secondary wall) what can do the tear index decrease. The next beating causes also this layer fibrillation, which leads to the increase of the strength value ( Fig. 3 , Tab. 1 ).Paper strength properties such as tensile strength and Scott bond strength were strongly influenced by internal fibrillation; these could also be increased further by promoting mostly external fibrillation ( Kang & Paulapuro 2006b ).
The course of the breaking length decrease and the tearing strength increase of the paper sheet is in accordance with the results of Sutjipto et al. (2008 ) at the threefold recycling of the bleached (88% ISO) softwood pulps prepared at the laboratory conditions, beated on PFI mill to 25 SR.
Tear index alteration of the paper sheets drying at the temperature of 80, 100 a 120°C, during eightfold recycling
Song & Law (2010 ) observedkraft pulp oxidation and its influence on recycling characteristics of fibres, the found up the fibre oxidation influences negatively the tear index of paper sheets.Oxidation of virgin fibre prior to recycling minimized the loss of WRV and sheet density.
The beating causes the fibres shortening and fines formation which is washed away in the large extent and it endeds in the paper sludges. This waste can be further processed and effective declined.
Within theEuropean Union several already issued and other foreseendirectives have great influence on the waste managementstrategy of paper producing companies. Due to the large quantities ofwaste generated, the high moisture content of the wasteand the changing composition, some recovery methods,for example, conversion to fuel components, are simplytoo expensive and their environmental impact uncertain.The thermal processes, gasification and pyrolysis, seem tobe interesting emerging options, although it is still necessaryto improve the technologies for sludge application.Other applications, such as the hydrolysis to obtain ethanol,have several advantages (use of wet sludge and applicabletechnology to sludges) but these are not welldeveloped for pulp and paper sludges. Therefore, at thismoment, the minimization of waste generation still hasthe highest priority ( Monte et al. 2009 ).
2.1.2. Drying influence on the recycled fibres
Characteristic differences between recycled fibres and virgin fibres can by expected. Many of these can by attributed to drying. Drying is a process that is accompanied by partially irreversible closure of small pores in the fibre wall, as well as increased resistance to swelling during rewetting. Further differences between virgin and recycled fibres can be attributed to the effects of a wide range of contaminating substances ( Hubbe et al. 2007 ). Drying, which has an anisotropic character, has a big influence on the properties of paper produced from the secondary fibres.During the drying the shear stress are formatted in the interfibrilar bonding area. The stresses formatted in the fibres and between them effect the mechanical properties in the drying paper. The additional effect dues the tensioning of the wet pulp stock on the paper machine.
During the drying and recycling the fibres are destructed. It is important to understand the loss of the bonding strength of the drying chemical fibres. Dang (2007 ) characterized the destruction like a percentage reduction of ability of the water retention value (WRV) in pulp at dewatering.
Hornification = [(WRV 0 -WRV 1 )/WRV 0 ]. 100 [%],
WRV 0 –is value of virgin pup
WRV 1 –the value of recycled pulp after drying and reslushing.
According to the prevailing concept, hornification occurs in the cell wall matrix of chemical fibres. During drying, delaminated parts of the fiber wall, i.e., cellulose microfibrils become attached as Fig. 4 shows ( Ackerman et al. 2000 ).
Changes in fiber wall structure ( Weise &Paulapuro 1996 )
Shrinkage of a fiber cross section ( Ackerman et al. 2000 )
Hydrogen bonds between those lamellae also form. Reorientation and better alignment of microfibrils also occur. All this causes an intensely bonded structure. In a subsequent reslushing in water, the fiber cell wall microstructure remains more resistant to delaminating forces because some hydrogen bonds do not reopen. The entire fiber is stiffer and more brittle ( Howard 1991 ). According to some studies ( Bouchard &Douek 1994 ; Maloney et al. 1998 ), hornification does not increase the crystallinity of cellulose or the degree of order in the hemicelluloses ofthe fiber wall.
The drying model of Scallan ( Laivins&Scallan 1993 ) suggests that hornification prevents the dry structure in A from fully expanding to the wet structure in D. Instead, only partial expansion to B may be possible after initial drying creates hydrogen bonds between the microfibrils( Kato & Cameron 1999 )
Weise & Paulapuro (1996 ) did very revealing work about the events during fiber drying. They studied fiber cross section of kraft fibers in various solids by Confocal Laser Scanning Microscope (CLSM) and simultaneously measured hornification with WRV tests. Irreversible hornification of fibers began on the degree of beating. It does not directly follow shrinkage since the greatest shrinkage of fibers occurs above 80 % solids content. In Figs. 4 and 5 , stage A represented wet kraft fiber before drying. In stage B, the drainage has started tocause morphological changes in the fiber wall matrix at about 30 % solids content. The fiber wall lamellae start to approach each other because of capillary forces. During this stage, the lumen can collapse. With additional drying, spaces between lamellae continue shrinking to phase C where most free voids in the lamellar structure of the cell wall have already closed. Toward the end of drying in stage D, the water removal occurs in the fine structure of the fiber wall. Kraft fiber shrink strongly and uniformly during this final phase of drying, i.e., at solid contents above 75-80 %. The shrinkage of stage D is irreversible.
At a repeated use of the dried fibres in paper making industry, the cell walls receive the water again. Then the opposite processes take place than in the Fig. 4 and 5 . It show Scallan´s model of the drying in Fig. 6 .
The drying dues also macroscopic stress applied on paper and distributed in fibres system according a local structure.
2.1.3. Properties of fibres from recycled paper
The basic properties of origin wet fibres change in the drying process of pulp and they are not fully regenerated in the process of slushing and beating.
The same parameters are suitable for the description of the paper properties of secondary fibres and fibres at ageing as well as for description of primary fibres properties. The experiences obtained at the utilisation of waste paper showed the secondary fibres have very different properties from the origin fibres. Next recycling of fibres causes the formation of extreme nonhomogeneous mixture of various old fibres. At the optimum utilisation of the secondary fibres it need take into account their altered properties at the repeated use. With the increase number of use cycles the fibres change irreversible, perish and alter their properties. Slushing and beating causes water absorption, fibres swelling and a partial regeneration of properties of origin fibres. However the repeated beating and drying at the multiple production cycles dues the gradual decrease of swelling ability, what influences a bonding ability of fibres. With the increase of cycles number the fibres are shortened. These alterations express in paper properties. The decrease of bonding ability and mechanical properties bring the improving of some utility properties. Between them there is higher velocity of dewatering and drying, air permeability and blotting properties improve of light scattering, opacity and paper dimensional stability.
The highest alterations of fibres properties are at the first and following three cycles. The size of strength properties depends on fibres type ( Geffertová et al. 2008 ).
Drying influences fibres length, width, shape factor, kinks which are the important factors to the strength of paper made from recycled fibres. The dimensional characteristics are measured by many methods, known is FQA (Fiber Quality Analyser), which is a prototype IFA (Imaging Fiber Analyser) and also Kajaani FS-200 fibre-length analyser. They measure fibres length, different kinks and their angles. Robertson et al. (1999 ) show correlation between methods FQA and Kajaani FS-200. A relatively new method of fibres width measurement is also SEM (Scanning Electron Microscope) ( Bennis et al. 2010 ). Among devices for analyse of fibres different properties and characteristics, e.g. fibres length and width, fines, various deformations of fibres and percentage composition of pulp mixture is L&W Fiber Tester (Lorentzen & Wettre, Sweden). At every measurement the minimum of 20 000 fibres in a sample is evaluated. On Fig. 7 there is expressed the alteration of fibres average length of softwood pulps during the eightfold recycling at the different drying temperature of pulp fibres.
Influence of recycling number and drying temperature on length of softwood pulps
Influence of recycling number and drying temperature on width of softwood pulps
The biggest alteration were observed after first beating (zero recycling), when the fibres average length decrease at the sheet drying temperature of 80°C about 17%, at the temperature of 100°C about 15.6% and at the temperature of 120°C about 14.6%.
After the first beating the fibres average width was markedly increased at the all temperatures dues to the fibrillation influence. The fibres fibrillation causes the fibre surface increase. Following markedly alteration is observed after fifth recycling, when the fibres average width was decreased. We assume the separation of fibrils and microfibrils from the cell walls dues the separation of the cell walls outside layer, the inside nonfibriled wall S2 was discovered and the fibres average width decreased. After the fifth recycling the strength properties became worse, mainly tear index ( Fig. 3 ).
The softwood fibres are longer than hardwood fibres, they are not so straight. The high value of shape factor means fibres straightness. The biggest alterations of shape factor can be observed mainly at the high drying temperatures. The water molecules occurring on fibres surface quick evaporate at the high temperatures and fibre more shrinks. It can result in the formation of weaker bonds between fibres those surfaces are not enough near. At the beginning of wet paper sheet drying the hydrogen bond creates through water layer on the fibres surface, after the drying through monomolecular layer of water, finally the hydrogen bond results after the water removal and the surfaces approach. It results in destruction of paper and fibre at the drying.
Chemical pulp fines are an important component in papermaking furnish. They can significantly affect the mechanical and optical properties of paper and the drainage properties of pulp ( Retulainen et al. 1993 ). Characterizing the fines will therefore allow a better understanding of the role of fines and better control the papermaking process and the properties of paper. Chemical pulp fines retard dewatering of the pulp suspension due to the high water holding capacity of fines. In the conventional method for characterizing the role of fines in dewatering, a proportion of fines is added to the fiber furnish, and then only the drainage time. Fines suspension is composed of heterogeneous fines particles in water. The suspension exhibits different rheological characteristics depending on the degree of interaction between the fines particles and on their hydration ( Kang & Paulapuro 2006b ).
From Fig. 9 we can see the highest formation of fines were after seventh and eight recycling, when the fibres were markedly weakened by the multiple using at the processes of paper making. They are easier and faster beating (the number of revolution decreased by the higher number of the recycling).
Influence of recycling process and drying temperature on pulp fines changes
The macroscopic level (density, volume, porosity, paper thickness) consists from the physical properties very important for the use of paper and paperboard. They indirectly characterize the three dimensional structure of paper ( Niskanen 1998 ). A paper is a complex structure consisting mainly of a fibre network, filler pigment particles and air. Light is reflected at fibre and pigment surfaces in the surface layer and inside the paper structure. The light also penetrates into the cellulose fibres and pigments, and changes directions. Some light is absorbed, but the remainder passes into the air and is reflected and refracted again by new fibres and pigments. After a number of reflections and refractions, a certain proportion of the light reaches the paper surface again and is then reflected at all possible angles from the surface. We do not perceive all the reflections and refractions (the multiple reflections or refractions) which take place inside the paper structure, but we perceive that the paper has a matt white surface i.e. we perceive a diffuse surface reflection. Some of the incident light exists at the back of the paper as transmitted light, and the remainder has been absorbed by the cellulose and the pigments. Besides reflection, refraction and absorption, there is a fourth effect called diffraction. In other contexts, diffraction is usually the same thing as light scattering, but within the field of paper technology, diffraction is only one aspect of the light scattering phenomenon. Diffraction occurs when the light meets particles or pores which are as large as or smaller then the wavelength of the light, i.e. particles which are smaller than one micrometer (μm). These small elements oscillate with the light oscillation and thus function as sites for new light sources. When the particles or pores are smaller than half of the light wavelength the diffraction decreases. It can be said that the light passes around the particle without being affected ( Pauler 2002 ).
The opacity, brightness, colouring and brilliance are important optical properties of papers and paperboards. For example the high value of opacity is need at the printing papers, but opacity of translucent paper must be lower. The paper producer must understand the physical principles of the paper structure and to determine their characteristics composition. It is possible to characterize nondirect the paper structure. The opacity characterizes the paper ability to hide a text or a figure on the opposite side of the paper sheet. The paper brightness is a paper reflection at a blue light use. The blue light is used because the made fibers have yellowish colour and a human eye senses a blue tone like a white colour.The typical brightness of the printing papers is 70 – 95% and opacity is higher than 90% ( Niskanen 1998 ).
3. Paper ageing
The recycled paper is increasingly used not only for the products of short term consumption (newspaper, sanitary paper, packaging materials e.g.), but also on the production of the higher quality papers, which can serve as a culture heritage medium. The study of the recycled papers alterations in the ageing process is therefore important, but the information in literature are missing.
The recycling is also another form of the paper ageing. It causes the paper alterations, which results in the degradation of their physical and mechanical properties. The recycling causes a chemical, thermal, biological and mechanical destruction, or their combination ( Milichovský 1994 ; Geffertová et al. 2008 ).The effect of the paper ageing is the degradation of cellulose, hemicelluloses and lignin macromolecules, the decrease of low molecular fractions, the degree of polymerisation (DP) decrease, but also the decline of the mechanical and optical properties ( El Ashmawy et al. 1974 ; Valtasaari & Saarela 1975 ; Lauriol et al. 1987a ,b,c; Bansa 2002 ; Havermans 2003 ; Dupont & Mortha 2004 ; Kučerová & Halajová, 2009 ; Čabalová et al. 2011 ).Cellulose as the most abundant natural polymer on the Earth is very important as a renewable organic material. The degradation of cellulosebasedpaper is important especially in archives and museums where ageing in various conditions reduces the mechanical properties and deteriorates optical quality of stored papers, books and other artefacts. The low rate of paper degradation results in the necessity of using accelerating ageing tests. The ageing tests consistin increasing the observed changes of paper properties, usually by using different temperature, humidity, oxygen content and acidity, respectively. Ageing tests are used in studies of degradation rate and mechanism. During the first ageing stages—natural or accelerated—there are no significant variations in mechanical properties: degradation evidence is only provided by measuring chemical processes. Oxidation induced by environmental conditions, in fact, causes carbonyl and carboxyl groups formation, with great impact on paper permanence and durability, even if mechanical characteristics are not affected in the short term ( Piantanida et al. 2005 ). During the degradation two main reactions prevail – hydrolysis of glycosidic bonds and oxidation of glucopyranose rings. As a result of some oxidation processes keto- and aldehyde groups are formed. These groups are highly reactive; they are prone to crosslinking, which is the third chemical process of cellulose decay ( Bansa 2002 , Calvini & Gorassini 2006 ).
At the accelerated paper ageing the decrease of DP is very rapid in the first stages of the ageing, later decelerates. During the longer time of the ageing there was determined the cellulose crosslinking by the method of size exclusion chromatography (SEC) ( Kačík et al. 2009 ). The similar dependences were obtained at the photo-induced cellulose degradation ( Malesic et al. 2005 ).
An attention is pay to the kinetic of the cellulose degradation in several decades, this process was studied by Kuhn in 1930 and the first model of the kinetic of the cellulose chains cleavage was elaborated by Ekenstam in 1936.This model is based on the kinetic equation of first-order and it is used to this day in modifications for the watching of the cellulose degradation in different conditions. Hill et al. (1995 ) deduced a similar model with the
Alterations of DP (degree of polymerisation) of cellulose fibres due to recycling and ageing at the pulp fibres drying temperature of 80°C, 100°C a 120°C.
contribution of the zero order kinetic. Experimental results are often controversial and new kinetic model for explanation of cellulose degradation at various conditions was proposed ( Calvini et al. 2008 ). The first-order kinetic model developed by these authors suggests that the kinetics of cellulose degradation depends upon the mode of ageing. An autoretardant path is followed during either acid hydrolysis in aqueous suspensions or oven ageing, while the production of volatile acid compounds trapped during the degradation in sealed environments primes an autocatalytic mechanism. Both these mechanisms are depleted by the consumption of the glycosidic bonds in the amorphous regions of cellulose until the levelling-off DP (LODP) is reached.
At the accelerated ageing ofnewspaper ( Kačík et al. 2008 ), the cellulose degradation causes the decrease of the average degree of polymerisation(DP). The DP decrease is caused by two factors in accordance with equation
DP = LODP + DP01.e -k1.t + DP02.e -k2.t ,
where LODP is levelling-off degree of polymerisation. There is a first factor higher and quickdecreasing during eight days and a second factor is lower and slow decreasing and dominant aftereight days of the accelerating ageing in the equation. The number of cleavaged bonds can be welldescribed by equation
DP 0 /DP t – 1 = n 0 .(1-e -k.t ),
where n 0 is an initial number of bonds available for degradation. The equation of the regression function is in accordance with Calvini et al. (2007 ) proposal, the calculated value (4.4976) is in a good accordance with the experimentally obtained average values of DP 0 a DP 60 (4.5057). The DP decreased to cca 38% of the initial value and the polydispersity degree to 66% of the initial value. The decrease of the rate constant with the time of ageing was obtained also by next authors ( Emsley et al. 1997 ; Zervos & Moropoulou 2005 ; Ding & Wang 2007 ). Čabalová et al. (2011 ) observed the influence of the accelerated ageing on the recycled pulp fibres, they determined the lowest decrease of DP at the fibres dried at the temperature of 120°C ( Fig. 10 ).
The simultaneous influence of the recycling and ageing has the similar impact at the drying temperatures of 80°C (decrease about 27,5 %) and 100°C (decrease about 27.6%) in regard of virgin pulp, lower alterations were at the temperature of 120°C (decrease about 21.5%). The ageing of the recycled paper causes the decrease of the pulp fiber DP, but the paper remains good properties.
4. Conclusion
The recycling is a necessity of this civilisation. The paper manufacturing is from its beginning affiliated with the recycling, because the paper was primarily manufactured from the 100 % furnish of rag. It is increasingly assented the trend of the recycled fibers use from the European and world criterion. The present European papermaking industry is based on the recycling.
The presence of the secondary fibres from the waste paper, their quality and amount is various in the time intervals, the seasons and the regional conditions. It depends on the manufacturing conditions in the paper making industry of the country.
At present the recycling is understood in larger sense than the material recycling, which has a big importance from view point of the paper recycling. Repeatedly used fibres do not fully regenerate their properties, so they cannot be recycled ad anfinitum. It allows to use the alternative possibilities of the paper utilisation in the building industry, at the soil reclamation, it the agriculture, in the power industry.
The most important aim is, however, the recycled paper utilisation for the paper manufacturing.
Acknowledgments
This work was financed by the Slovak Grant Agency VEGA (project number 1/0490/09).
- 11. CEPI (Confederation of European Paper Industries). 2006 Special Recycling 2005 Statistics- European Paper Industry Hits New Record in Recycling. 27.02.2011, Available from: http://www.erpa.info/images/Special_Recycling_2005_statistics.pdf
- 12. CEPI (Confederation of European Paper Industrie). 2010 Annual Statistic 2009. 27.02.2011, Available from: http://www.erpa.info/download/CEPI_annual_statistics%202009.pdf
- 18. European Declaration on Paper Recycling 2006 2010 , Monitoring Report 2009 (2010), 27.02. 2011, Available from: http://www.erpa.info/images/monitoring_report_2009.pdf
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Recycling of Waste and Used Papers: A Useful Contribution in Conservation of Environment: A Case Study
Article type: Research Article
Authors: Kumar, Vijay ; *
Affiliations: Department of Physics, Graphic Era Hill University, Dehradun (Uttrakhand), India 248001
Correspondence: [*] Corresponding Author. [email protected]
Abstract: The aim of this article is to make people aware about the needs and requirements of the recycling of the waste papers as the traditional papers are made from the wooden pulp of trees. Thus trees are cut for the fulfillment of papers in the whole world. The paper mills are the world’s third largest industry that are responsible for the pollution. The paper industry is responsible not only for air pollution but also land pollution, water pollution etc. If we encourage the people for recycling, we can save the trees and also environment. A waste paper can be recycled seven times for reuse again and again. Thus we should recycle the waste papers whenever it is possible.
Keywords: Waste and used papers, recycling of waste papers, environment, conservation
DOI: 10.3233/AJW-170034
Journal: Asian Journal of Water, Environment and Pollution , vol. 14, no. 4, pp. 31-36, 2017
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Original research article, recycled paper as a source of renewable jet fuel in the united states.
- 1 Process Modeling and Analysis Group, Los Alamos National Laboratory, Los Alamos, NM, United States
- 2 Inorganic, Isotope, and Actinide Chemistry Group, Los Alamos National Laboratory, Los Alamos, NM, United States
- 3 Material Synthesis and Integrated Devices Group, Los Alamos National Laboratory, Los Alamos, NM, United States
- 4 Chemical Process Scale-Up Group, Oak Ridge National Laboratory, Oak Ridge, TN, United States
Converting biomass into jet fuel involves more than the core chemical process. The overall process includes the logistics of harvesting and transporting the biomass, handling and preparing the material for processing, and processing and disposal of waste. All of these activities contribute to cost. Controlling cost involves more than developing efficient process chemistry. Choice of feedstock also has a significant impact on process economics. We consider chemical conversion of paper from municipal solid waste as a feedstock for the production of jet fuel and diesel. Paper has a significantly higher cellulose content than raw lignocellulosic biomass such as corn stover, so it requires less pretreatment to convert it into hydrocarbons than lignocellulosic biomass. Our techno-economic analysis showed that the cost of converting paper waste into jet fuel is about $1.00/gal less than jet fuel produced from corn stover. Although the cost of recycling paper into jet fuel is less than producing it from corn stover, the process is not competitive with petroleum. We estimated a minimum selling price of $3.97/gal for paper-derived jet fuel. Our sensitivity studies indicated that the biggest economic obstacle is the cost of cellulose hydrolysis. Direct hydrogenation of paper to sugar alcohols combined with increased economy of scale could make recycling paper jet fuel competitive.
Introduction
In 2019, the US aviation industry consumed 636 million barrels or 3.8 EJ of fuel ( US Energy Information Agency, 2021a ). Air travel accounts for about 12% of the fuel consumed by the US transportation sector and about 13% of the carbon dioxide emissions ( US Energy Information Agency, 2021a ). The International Air Transport Association is committed to carbon-neutral growth of their industry ( Stalnaker et al., 2016 ). This goal will limit carbon dioxide emissions from air transportation to 2020 levels ( International Air Transport Association, 2015 ). Strategies for meeting this goal include efficiency improvements, but efficiency improvements alone are not sufficient. A bio-based hydrocarbon fuel with low life-cycle carbon dioxide emissions is also needed.
Sustainability encompasses economic and social impacts as well as environmental impact. Use of lignocellulosic biomass addresses, in part, economic and social impacts by avoiding competition with food crops and the social impact of higher food prices. However, a sustainable fuel also must be cost competitive. The average US jet fuel price in 2019 was $1.97/gal ( US Energy Information Agency, 2021a ). The US Energy Information Agency projects only a moderate increase in price to $2.04/gal by 2030 ( US Energy Information Agency, 2021b ). The National Renewable Energy Laboratory (NREL) estimated the cost of producing hydrocarbon fuels from lignocellulosic biomass to be $4.05/gal in 2011 US dollars (USD) ( Davis et al., 2015 ). Wang et al. (2016) report the cost of converting lignocellulosic biomass into jet fuel to be $4.00–$23.30/gal. Currently, producing jet fuel from lignocellulosic biomass is not sustainable because it is not economically competitive.
Producing jet fuel from biomass involves more than the chemistry. It includes the logistics of obtaining the biomass, preparation and pretreatment of the biomass, and processing and disposal of waste. All of these associated processing steps contribute to the overall capital investment and operating costs of the plant. Controlling cost requires more than efficient process chemistry. Choice of feedstock with its associated costs, availability, and logistics has a significant impact on process economics.
We investigated other sources of sustainable jet fuel and concluded that recycle paper is a promising alternative to raw lignocellulosic biomass. Paper is a refined product with significantly higher cellulose content than raw biomass (see Table 1 ); so it requires less handling and pretreatment. It also contains less waste materials than raw biomass. Therefore, producing hydrocarbon fuels from recycle paper instead of raw biomass reduces the capital investment and the operating costs. Cultivated forest biomass, such as the loblolly pine in the Southeastern US, is an important source of wood pulp ( Gonzalez et al., 2011 ) and a possible source of lignocellulosic biomass for fuel production ( US Department of Energy, 2016 ). Figure 1 shows that producing jet fuel from recycled paper is part of a closed carbon cycle similar to other biofuels. The biomass to paper to jet fuel cycle differs from other biofuel cycles in that it involves reuse of a commercially valuable intermediate product.
TABLE 1 . Typical compositions of raw corn stover and recycle paper.
FIGURE 1 . A simple diagram of the carbon cycle for the production of jet fuel from recycle paper.
We considered whether using recycle paper to produce fuels has any economic advantages over processes based on raw lignocellulosic biomass. Therefore, we performed a techno-economic analysis of a process for converting recycle paper into jet fuel. Our conceptual design is based on a process that Blommel and Price (2017) patented for converting sugars into hydrocarbon fuels. The evaluation included the availability of paper for recycling, costs, and lifecycle carbon dioxide emissions and solid waste generation. The time needed to commercialize a new process for a commodity chemical is on the order of 10 years ( Vogel 2005 ), so we have set our target production cost to the projected 2030 jet fuel price of $2.04/gal.
The goal is not to argue that recycling paper to jet fuel is the solution to sustainable air transportation. Instead, we want to show that using recycled paper as a feedstock could be a first step in commercializing technology for producing fuels from cellulosic materials.
Viability of Recycled Paper as a Source of Jet Fuel
Figure 2 shows US paper consumption for 2017 and its ultimate disposition. Overall paper usage in the US is decreasing; but wrapping, packaging, and board, which is the major use of paper products, is increasing as a result of increased e-commerce (Food and Agricultural Organization of the UN, 2015). About 83% of the paper consumed is suitable or available for recycling into paper products. The remaining 17% is used for books and other permanent records or it is contaminated with food and materials that make it unsuitable as a source of paper products. Currently, about 64% of the paper used in the US is collected for recycling ( US Environmental Protection Agency, 2020 ). Of the paper collected, domestic recyclers use 59% and the remainder is exported. When paper is recycled, an average of 12% of the cellulose fibers are rejected because of degradation ( European Integrated Pollution Prevention and Control Bureau, 2001 ).
FIGURE 2 . 2017 US paper consumption and ultimate disposition in million annual tonnes. The diagram is based on information from ( European Integrated Pollution Prevention and Control Bureau, 2001 ), ( Food and Agriculture Organization of the United Nations, 2015 ), and ( US Environmental Protection Agency, 2020 ).
Scrap paper currently being exported, paper currently discarded to landfills, and degraded pulp from recycling plants could be used for jet fuel production without any impact on current domestic recyclers. Thus, the minimum amount of scrap paper available for fuel product would be 36 million tonnes/yr. We estimated that 1 tonne of mixed paper waste could produce about 2.4 bbl of jet fuel. (We will discuss the basis of this estimate in subsequent sections.) The minimum amount scrap paper available for fuel production could yield about 76–83 million bbl of jet fuel per year, which is 13–14% of the annual US demand. The maximum amount of paper that could be converted to jet fuel is the total amount of paper available for recycling plus part of the paper that is currently not recyclable, or 59 million tonne/yr. The maximum jet fuel production would be about 124–136 million bbl/yr or 21–22% of the US demand. We estimated that up to 3 million tonnes/yr of food contaminated waste that is currently considered not recyclable may be suitable for producing an additional 7 million bbl/yr of jet fuel. Although recycle paper cannot be used to replace all US jet fuel needs, the amount of fuel that could be produced from this raw material is not trivial.
Recyclable paper has some logistical advantages over lignocellulosic biomass. First, paper is not a seasonal crop. It is available continually throughout the year, which reduces storage requirements and costs. Second, the largest sources of recyclable paper are large metropolitan areas where the amount of paper available per hectare is much greater than lignocellulosic biomass derived from agricultural waste. If 75% of the rural land in a Midwestern state is available for corn production, and corn stover are harvested from 50% of the available land, the concentration of biomass would be 1.9 tonne/ha which yields 1.0 tonne/ha of sugar ( Aden et al., 2002 ). Based on average US paper consumption per capita, average recycling rates, and population density, we estimated the concentration of recyclable paper in New York City to be 19 tonne/ha, which yields 16 tonne/ha of sugar. New York City is the most concentrated source of recyclable paper, but the concentration of recyclable paper in less densely populated cities is still greater than the concentration of corn stover in a Midwestern farming area ( European Integrated Pollution Prevention and Control Bureau 2001 ). The amount of recyclable paper available in the 10 largest US metropolitan areas is sufficient to produce about 10% of the fuel consumed by the domestic air transport industry. Because of the high concentration of recyclable paper in cities, collection cost per tonne for recycle paper are less than harvesting agricultural waste. Also, plants for converting recycled paper into jet fuels would be best located near large cities serviced by one or more large airports. Thus, jet fuel production would be located near the largest consumers, which would reduce distribution costs.
Process Descriptions
Blommel and Price (2017) patented a process for converting corn syrup into a hydrocarbon mixture encompassing the boiling range of jet fuel and diesel. The National Renewable Energy Laboratory (NREL) developed conceptual design of a process for converting lignocellulosic biomass into naphtha and diesel fuel based on Blommel and Price’s patent and enzymatic hydrolysis of cellulose. We developed two concepts based on Blommel and Price’s patent for converting recycle paper into jet fuel. The first concept is an adaptation of NREL’s process with enzymatic hydrolysis of cellulose. The second concept uses acid hydrolysis to produce the sugar syrup. Both processes require hydrogen, which is assumed to be supplied by an on-site steam reforming planted located on site.
Summary of Process With Enzymatic Hydrolysis
Figure 3 is a simplified block diagram showing the major steps of the paper to jet fuel process with enzymatic hydrolysis. This process is a version of the process developed by Davis et al. (2015) that has been modified to accept paper as the feedstock rather than corn stover. The process consists of eight major steps plus storage and utilities.
• Mechanical Repulping uses technology from the paper recycling industry to convert the recycled paper into a cellulose fiber slurry. The step includes creation of the fiber slurry, removal of filler materials, and deinking. Calcium carbonate is the major component of the filler, and it must be removed to reduce sulfuric acid consumption. The process differs from paper recycling because it does not include fractionation of the fibers or extensive dewatering steps. Because fiber quality is irrelevant, the process can accept paper contaiminate with food and other materials that make it unsuitable for paper products. The process is purely mechanical and uses no heat or chemicals.
• Pretreatment and Conditioning uses a dilute sulfuric acid to hydrolyze hemicellulose into its component sugars and organic acids. The sulfuric acid is neutralized with sodium hydroxide prior to Enzymatic Hydrolysis.
• Enzyme Production is a fermentation for production of the cellulase used for enzymatic hydrolysis of the cellulose fibers.
• Enzymatic Hydrolysis first converts the cellulose to dissolved glucose via an enzymatic hydrolysis. The hydrolysate is filtered to separate lignin and other solids from the aqueous solution.
• Concentration, Filtration, Ion Exchange evaporates excess water from the hydrolysate, it filters out any remaining solids, and it removes dissolved ionic species in a series of ion exchange columns. The product of this step is an aqueous solution that is nearly 50 wt% soluble sugars.
• Catalytic Conversion and Upgrading is based on ( Blommel and Price, 2017 ) process chemistry. The sugars are first hydrogenated to produce sugar alcohols. A sequence of dehydration, hydrogenation, and condensation reactions to covert sugar alcohols into C 1 –C 24+ hydrocarbons. This process step includes distillation to separate a light of hydrocarbons from the heavier distillate product.
• Wastewater Treatment is a combination of anaerobic and aerobic digestion to remove organic materials from the water. Anaerobic digestion produces a CH 4 /CO 2 biogas that can be used as fuel in the boiler. Sludge for aerobic digestion is dewatered and used as fuel. The wastewater treatment process also removes dissolved solids making the treated water suitable for reuse in the process.
• Boiler/Turbogenerator burns biogas, off gas from Catalytic Conversion and Upgrading, solid waste and organic materials from Mechanical Repulping, dewatered sludge for Wastewater Treatment, lignin, and other combustible solids to produce steam. Steam is used for process heat and generating electricity.
FIGURE 3 . A block diagram of a process for converting recycle paper into jet fuel with enzymatic hydrolysis.
Our Catalytic Conversion and Upgrading process is nearly identical to NREL’s ( Davis et al., 2015 ) realization of ( Blommel and Price, 2017 ) process. This process consists of four reaction steps and a distillation. We used the same catalysts and operating conditions for the reactor in our design, but we modified the distillation to produce an off gas (C 1 –C 7 ) and a fraction with the boiling range of jet fuel (C 8+ ). Davis et al. (2015) give the details of the catalysts and operating conditions used for Catalytic Conversion and Upgrading process.
The first step is catalytic hydrogenation to reduce the sugars to sugar alcohols (e.g., sorbitol) or other polyols. The sugar alcohols then undergo catalytic aqueous-phase reforming (APR), which is a complex set of reactions that produce hydrogen, carbon dioxide, light alkanes, oxygenated compounds ( Cortright et al., 2002 ). APRs tend to cleave C-C bonds and C-O bonds. Oxygenated products include alcohols, ketones, aldehydes, furans, diols, triols, and organic acids. Cleavage of aldehyde groups form hydrogen, carbon monoxide, and smaller polyols. In the water rich environment, carbon monoxide undergoes the water-gas shift reaction to form hydrogen and carbon dioxide. Carbon monoxide can also participate in the methanation and Fischer-Tropsch reactions to for light hydrocarbons.
The organic compounds in the APR product stream have an average carbon number less than six. In the condensation reactor, chain length increase to C 8 –C 24 . Multiple reactions occur in this step including dehydration, oligomerization, cyclization, aromatization, and hydrogenation producing normal and iso-paraffins, olefins, ketones, aromatics, and cycloparaffins ( Blommel and Price, 2017 ; Cortright and Blommel, 2013 ) The organic products, which are insoluble in water, are separated from the aqueous phase and fed to hydrotreating reactor where hydrodeoxygenation reactions remove oxygen from condensation products while leaving the carbon chains intact.
Summary of Process With Acid Hydrolysis
Figure 4 is a block diagram of the process with acid hydrolysis. The process is similar in structure to the process with enzymatic hydrolysis. Acid hydrolysis performs the same function as the combined function Pretreatment and Conditioning, Enzyme Production, and Enzymatic Hydrolysis. The processing step takes the repulped fibers and hydrolyzes the cellulose and hemicellulose into simple sugars. Acid Recovery, Concentration, and Ion Exchange removes the sulfuric acid for the hydrolysate and concentrates it for recycling. This step also includes filtering out residual solids, concentrating the hydrolysate, and removing dissolved ionic species from the hydrolysate. The product of these two steps is a syrup containing about 50 wt% dissolve sugars. The sugar solution is converted into jet fuel using the same method as the process with enzymatic hydrolysis.
FIGURE 4 . A block diagram of a process for converting recycle paper into jet fuel with acid hydrolysis.
Acid hydrolysis is based on what the technical literature refers to as the two-step process. It is called the two-step process because it consists of two hydrolysis steps–a dilute acid hydrolysis of hemicellulose followed by a concentrated acid hydrolysis of cellulose ( Kosaric et al., 2011 ). The complete process includes the hydrolysis steps plus separation processes. The process begins with the dilute acid hydrolysis. Sulfuric acid is added to the pulp slurry creating a mixture containing 4.4 wt% sulfuric acid. Dilute acid hydrolysis occurs at 100°C. This step results in complete hydrolysis of the hemicellulose in the paper. The mild operating conditions minimize the conversion of pentoses into furfural and the production furfural oligomers and polymers. After dilute hydrolysis, the remaining solids are filtered out of the slurry, dried, and combined with 85 wt% sulfuric acid. After the solids are mixed with the acid, water is added to reduce the sulfuric acid concentration to 8 wt%. Concentrated acid hydrolysis occurs at 110°C and results in a 90% cellulose conversion. Residual solids are removed from the hydrolysate, and the hydrolysate is combined with the dilute acid hydrolysate.
The first step in purifying and concentrating the hydrolysate is removing the sulfuric acid using resin wafer electrodeionization (RW-EDI) ( Datta et al., 2013 ). RW-EDI is a modified version of electrodialysis that incorporates ion exchange resin beads within the electrodialysis stack. RW-EDI removes 99% of the sulfuric acid from the hydrolysate and concentrates it to 25 wt%. The hydrolysate passes through an ultrafilter prior to RW-EDI to ensure that it contains no fine particles that could foul the membrane. Part of the sulfuric acid is distilled to produce 85 wt% sulfuric acid for concentrated acid hydrolysis. The remainder is recycled to dilute acid hydrolysis. After the sulfuric acid has been removed, the hydrolysate is concentrated using the same process as in the process with enzymatic hydrolysis, and dissolved anionic species are removed in an ion exchange column. The hydrolysate contains no cationic species other than hydrogen ions.
Material and Energy Balances
We determined the material balances for a 3,900 bbl/day jet fuel plant. We included a corn stover to jet fuel process based on the biomass to hydrocarbon process of Davis et al. (2015) . The process was modified to produce a distillate consisting of hydrocarbons with chain-lengths in the jet fuel range. The corn stover composition for this process is given in Table 1 . Material and energy balances for this process were obtained directly from Davis et al. (2015) with slight modifications. Table 2 contains a summary of the material and energy balances for the corn stover to jet fuel process.
TABLE 2 . Overall material and energy balances for corn stover to jet fuel, recycle paper to jet fuel with enzymatic hydrolysis, and recycle paper to jet fuel with acid hydrolysis.
The feedstock for the recycle paper to jet fuel process consists of 80% recyclable paper and 20% unrecyclable paper, which approximates typical municipal solid waste. Table 1 gives the composition of recyclable and unrecyclable paper. Food contamination of unrecyclable paper is represented by a high lipids content. The inorganic content of paper consists of whitening agents and filler. Calcium carbonate and talc constitute the vast majority of these inorganic materials. The metal content consists of staples, fastener, foil, and other metals that were not removed when the paper was discarded or segregated for recycling.
To calculated the material and energy balances for the paper to jet fuel process with enzymatic hydrolysis, we used the same assumptions and models used by Davis et al. (2015) for their biomass to hydrocarbon process. Most of the ink, inorganic filler materials, and metal are removed from the paper during the repulping process using a series of settling and flotation operations. Repulping consumed electricity to drive the mechanical repulping and physical separation processes. We obtained an estimate of the power consumption from an International Energy Agency publication ( Börjessen and Ahlgren, 2015 ). Table 2 contains a summary of the material and energy for the paper to jet fuel process with enzymatic hydrolysis.
For the paper to jet fuel process with acid hydrolysis, we used a ChemCAD model to determine the material and energy balances for acid hydrolysis, acid recovery, hydrolysate concentration, and ion exchange. Power needed for the RW-EDI process was estimated from the current cell, voltage, and cell efficiency ( Patel et al., 2020 ). The paper to jet fuel process with acid hydrolysis produces a concentrated hydrolysate containing about 50 wt% sugars, which is fed to Catalytic Conversion and Upgrading. Assumptions and models used for Chemical Conversion and Upgrading are the same as those used for the process with enzymatic hydrolysis. The assumptions and models for wastewater treatment and the boiler/turbogenerator are the same as used in the process based on corn stover ( Davis et al., 2015 ). Table 2 contains a summary of the material and energy for the paper to jet fuel process with acid hydrolysis.
A key difference among the three processes is yield per tonne of feedstock. The yields of all three processes are about 80% of the theoretical maximum based on carbohydrate content (i.e. cellulose, hemicellulose, and starches), but the carbon hydrate content of corn stover is significantly less than paper. Corn stover contains about 47 wt% carbohydrates while paper contains 63–76 wt% carbohydrates. The lower carbohydrate content means that 1.4–1.5 tonnes of corns stover is required to produce the same volume of jet fuel as 1.0 tonne of recycle paper.
Another key difference is the fuel produced per tonne of feedstock. Corn stover contains more lignin and other organic matter that can be used as fuel than paper. The additional fuel means that the corn stover process is net producer of electricity while recycle paper processes are net electric consumers. Because of the greater volume processed and the chemical form of the inorganic material, burning the corn stover residue produces approximately 3 times the solid waste than burning the residue of a paper to jet fuel process.
A third key difference is the ratio of cellulose to hemicellulose. Paper is a refined bioproduct that contains nearly 5 times more cellulose than hemicellulose. The cellulose to hemicellulose ratio in corn stover is about 1.8. Because the glucose from cellulose constitutes a greater fraction of the total sugars produced, a jet fuel process with enzymatic hydrolysis of paper requires more cellulase than a process based on corn stover as well as the more if the chemical feedstocks needed to produce cellulase.
The hydrolysis process has a significant impact on material and energy balances for the paper to jet fuel processes. The overall yields of both processes are about the same. However, recovery and recycling of sulfuric acid is also energy intensive. A process with acid hydrolysis consumes about twice as much steam as a process with enzymatic hydrolysis. Increased process steam consumption in the process using acid hydrolysis result in approximately 64% less electrical power generation than a process with enzymatic hydrolysis. Use of RW-EDI in for sulfuric acid production results in a process that consumes about twice as much electricity as the process with enzymatic hydrolysis. As a consequence of lower power generation and higher power demand, the net electrical power consumption is about 12 times greater for the process with acid hydrolysis than the process with enzymatic hydrolysis.
Techno-Economic Analysis
Techno-economic analysis consists of three major parts–capital cost estimation to determine the investment required to build the process; operating costs estimate to determine the annual expenses of operating the plant; and a cash flow analysis, which combines capital and operating costs to determine the overall production costs. We use a methodology and assumptions that have been benchmarked against cellulosic ethanol production for the analysis ( Kubic, 2019 ). Cost estimates are based on a US Midwest location. Estimates are in 2020 USD.
Capital Cost Estimates
Capital cost estimates for the recycle paper to jet fuel were based on conceptual designs with a low level of maturity. Given the low level of process definition, the appropriate estimation method should be consistent with an Association for the Advancement of Cost Engineering International Class 5 ( AACE International, 2011 ) estimate with an accuracy range of -20/+30% to 50/+100% or an American National Standards Institute order-of-magnitude estimate ( Institute of Industrial Engineers, 2000 ) with an accuracy of −30/+50%. We used a factor method ( Woods, 2007 ) to determine fixed capital investment (FCI) and total capital investment (TCI) from purchased equipment cost (FOB cost).
We determined FOB costs and installation factors from correlations in Woods (2007) and data in Davis et al. (2015) . FOB costs were converted to 2020 USD using Chemical Engineering Plant Cost Index. Assumptions for estimating additional direct costs, indirect costs, and additional capital costs were based on the recommendations of ( Kubic et al., 2019 ). Contingencies are added to the cost estimate to account for judgment errors in accumulation of the project scope ( Page 1996 ). Contingencies can range from 10 to 80% of direct costs depending on the degree of project definition ( Garrett, 1989 ; Woods, 2007 ). Cost estimates in this study are based on a conceptual design, so large contingencies are appropriate. We assumed a contingency of 30% of direct costs based on ( US Department of Energy, 1997 ) guidance.
Table 3 is a summary of the capital cost estimates. The FCI for the corn stover to jet fuel is 5% greater than the paper to jet fuel with enzymatic hydrolysis. This difference is well withing the estimation errors for a Class 5 estimate. The FCI for the paper to jet fuel process with enzymatic hydrolysis is 10% greater than the process with acid hydrolysis. About 80% of this difference can be attributed to differences in the cost of the hydrolysis process. The installed equipment cost for enzymatic hydrolysis is more than 40% greater than the installed equipment cost for acid hydrolysis. Although the differences in FCI and installed equipment costs of hydrolysis equipment are within the uncertainty of Class 5 estimate, the count of major operations suggest that the difference may be real. Correlations for order-of-magnitude cost estimates have been developed that give FCI as a function of number of processing steps and plant capacity ( Zhang and El-Halwagi, 2017 ). Enzymatic hydrolysis requires 12 processing steps while acid hydrolysis requires 9. Fewer processing steps suggest that the FCI for acid hydrolysis should be less than the FCI for enzymatic hydrolysis.
TABLE 3 . Capital cost estimates for corn stover to jet fuel, recycle paper to jet fuel with enzymatic hydrolysis, and recycle paper to jet fuel with acid hydrolysis in million USD (2020).
Operating Cost Estimates
Operating costs are generally divided into two categories–variable costs, which depend on production volume, and fixed costs, which are independent of production volume. Variable costs include feedstock costs, chemicals, utilities, and waste disposal. We obtained the price of delivered corn stover from Thompson and Tyner (2011) . Price was adjusted for moisture content and converted to a 2020 price using the producer price index for hay from the US Bureau of Labor Statistics. The price of recycle paper depends on its classification, as shown in Table 4 . We used a weighted average of mixed paper, old cardboard, and sorted residential paper for the price of recyclable paper for our cost estimates. Unrecyclable paper is currently sent to landfills for disposal. We assumed a credit for unrecyclable paper equal to the average landfill charge in the US Midwest.
TABLE 4 . Prices of recycle paper in the US Midwest in USD (2020) ( Recycling Today, 2020 ).
We determined 2020 prices for chemicals, catalysts, and utilities from advertised prices, trade journals (e.g., ICIS Chemical Business ), technical journals and reports, commodity trading data, and the US Energy Information Agency. If data was available, we used annual average values. If multiple sources of data were available, we used the median value. If prices for 2020 were not available, we estimated the price using the available data and the appropriate producer price index from the US Bureau of Labor Statistics. We assumed that an onsite natural gas steam reforming plant provides hydrogen, and we estimated the hydrogen prices based on the 2020 industrial natural gas price of $3.29/Mscf. Electricity is purchased at the average 2020 price for the industrial users in the Midwest, which is $66.60/MWh. Excess electricity is exported at the average wholesale price for the Midwest. Makeup water price is based on the 2020 price for the City of Chicago. The only waste produced is ash from the boiler. Table 5 lists the prices for chemicals, catalysts, utilities, and waste disposal.
TABLE 5 . Prices for feedstocks, chemicals, catalysts, utilities, and waste disposal in USD (2020).
To determine variable costs on an annual basis, we assumed a 90% process availability. Repulping is established and reliable technology, so an assumed availability of 90% is reasonable for the paper to jet fuel processes. Current technology for preprocessing corn stover is unreliable and, therefore, has a low availability. To determine the inherent price advantage of recycle paper as a feedstock, we assumed that reliable technology for preprocessing corn stover already exists; and the corn stover to jet fuel process also has a 90% availability.
The number of operators required per shift using Brown’s method ( Brown, 2000 ). We assume that the plant employs five complete crews. Five complete crews provide a sufficient number of operators to ensure process is completely staffed at all times without the need for operators to work overtime. We assumed an operator wage of $26.50 per hour based on the average reported by the US Bureau of Labor Statistics for the Midwest in 2020.
The average maintenance cost for ethanol plants and biotechnology companies is less than the average for the chemical industry because materials tend to be less corrosive and operating conditions are milder than the chemical industry. Based on data from the ethanol industry and biotechnology companies, we estimated the average maintenance cost for a biorefinery to be 2.4% of FCI per year, which is less than average value of 6% for the chemical industry ( Garrett, 1989 ). Corn stover to jet fuel and paper to jet fuel process have characteristics of biorefineries and ordinary chemical plants. For example, enzyme production is a biorefinery-like operation, which should have maintenance costs typical of a biorefinery. Catalytic conversion is petrochemical-like and should have maintenance costs typical of the chemical industry. To account for the mixed nature of the processes, we used a cost weight average to estimate maintenance cost.
We used the cost factors and methods recommended by Kubic et al. (2019) to estimate the remaining fixed operating costs. Table 6 contains a summary of variable and fixed operating cost estimates.
TABLE 6 . Annual Operating Cost in million USD (2020).
Inspection of Table 6 reveals three important differences among the three processes. First, the cost of corn stover is substantially higher than recycle paper. The cost of corn stover per tonne is greater than paper and more corn stover must be processed to produce volume of product because of its lower carbohydrate content. Second, chemical costs for the paper to jet fuel process with acid hydrolysis are less than the other two processes because acid hydrolysis requires no chemicals and nutrients for cellulase production. Electric costs for the paper to jet fuel process with acid hydrolysis are much greater than the other two processes because of the power consumption of RW-EDI.
Cash Flow Analysis
We use a discount cash flow analysis to evaluate the minimum selling price for jet fuel. Minimum selling price is the product price needed to give a 10% real internal rate of return after taxes. The cash flow analysis begins with construction of the plant and continues through the life of the plant. Construction time can be estimated using the following correlation. ( Kubic, 2014 ).
where θ is the construction time in years, α is a constant that depends on the type of project, and TCI is the total capital investment. For a chemical plant with TCI computed in million 2020 USD, α is 0.53. Construction spending as a function of time is approximated by a beta distribution. Working capital and start-up expenses are accrued during the final year of construction. Startup, which is the time from the introduction of feedstock until the process achieves some degree of steady operations, is assumed to be 3 months ( Myers et al., 1986 ). Production is assumed to be zero during the startup period and 80% of nameplate capacity during the first year of operations.
Table 7 summarizes the financial parameters for the discount cash flow analysis. Plant life is measured from the end of start-up. It is not a true measure of plant life. Rather, it is a time horizon for the cash flow analysis. Depreciation in the analysis is only used to estimate corporate profit taxes. We use a modified accelerated cost recovery system with a 7 years depreciation time. The method and depreciation time are dictated by the US tax code. Both federal and state corporate taxes are included in the analysis. We use a state tax rate of 4.8%, which is the average state tax rate in the US.
TABLE 7 . Financial parameters for discount cash flow analysis.
The minimum selling prices for the three processes that we considered in this study are $5.14/gal for the corn stover to jet fuel process, $3.97/gal for the paper to jet fuel process with enzymatic hydrolysis, and $4.13/gal for the paper to jet fuel process based in acid hydrolysis. Figure 5 shows the cost breakdown for the three processes by expense category. The minimum selling price for jet fuel produced from corn stover is more than $1.00 higher than jet fuel produced from recycle paper. This difference is the result of the high cost of corn stover relative to recycle paper. The minimum selling price for the paper to jet fuel processes within the uncertainty limits of the analysis. Although the total capital investment is less for the process with acid hydrolysis, the operating cost are higher as a result of the high electrical power consumption by RW-EDI.
FIGURE 5 . Cost breakdown by expense category for (A) Corn Stover to Jet Fuel Process, (B) Paper to Jet Fuel Process with Enzymatic Hydrolysis, and (C) Paper to Jet Fuel Process with Acid Hydrolysis.
Meeting the Cost Goal
The proposed paper to jet fuel processes do not meet the target production cost of $2.04/gal. Therefore, it is reasonable to consider possible technological improvements that could make the process competitive with petroleum-derived fuels. We identified six engineering improvements and technological advances that could improve process economics and determined their impact on cost.
• Increase Efficiency of RW-EDI – Figure 5 shows that electricity account for 16% of the cost for the paper to jet fuel process with acid hydrolysis, and RW-EDI accounts for over 60% of the energy consumption. Reducing RW-EDI power consumption and increasing the sulfuric acid concentration in the permeate would reduce power consumption and steam consumption as well as reduce capital costs. These savings would reduce the cost of producing jet fuel with the process with acid hydrolysis.
• Hydrogenation of Cellulose and Hemicellulose in Pulp –Pretreatment and hydrolysis account for over 25% of production costs for both paper to jet fuel processes. Direct hydrogenation of the pulp to produce sugar alcohols would eliminate the capital and operating costs associated with hydrolysis and reduce overall production costs.
• Hydrogenation of Cellulose and Hemicellulose in Paper –The cost of sorting paper in municipal solid waste is estimated to be about $75/tonne and the cost of repulping the paper is not negligible. Hydrogenating unsorted paper to produce sugar alcohols would reduce repulping costs and eliminate hydrolysis costs. By eliminating or substantially reducing sorting costs it could turn recycle paper costs into a credit.
• Increase Plant Capacity – Figure 5 shows that capital costs are the largest single factor in the overall cost of jet fuel. The paper to jet fuel processes scale with capacity to the 0.66 power. Doubling capacity will reduce capital costs relative to operating cost resulting in a reduction in product cost.
• Reduce Catalyst Cost –The catalysts for Catalytic Conversion and Upgrading are expensive. Reducing catalyst cost by a factor of 10 by finding less expensive options and improving catalyst life will reduce operating costs.
• Reduce Excess Hydrogen –In the current process design, about 22% more hydrogen is fed to Catalytic Conversion and Upgrading than is consumed by the process. Reducing excess hydrogen to less than 5%would reduce production costs.
We evaluated the possible cost saving for each of these scenarios considering reductions in capital costs as a result of eliminating processing steps, reduction in variable capital costs as a result of eliminating or reducing chemical feeds, and reducing the required number of operators. Only two of the perturbations could change overall process yields–direct hydrogenation of pulp and paper. For these two perturbations, we assumed yields were equal to those of the process based on acid hydrolysis.
Table 8 contains a summary of the results. The results show that no single innovation reduces the cost of converting recycled paper into jet fuel to the target value of $2.04/gal. The gains from incremental process improvements (i.e., increasing efficiency of RW-EDI, reducing catalyst cost, reducing excess hydrogen, and increasing plant capacity) are not large enough to meet the target price. A major technical innovation is needed.
TABLE 8 . Impact of possible process improvements on minimum selling price.
Pretreatment and hydrolysis account for over 25% of production costs. Direct hydrogenation of cellulose is the subject of current research activities ( Kobayashi et al., 2011 ; Jiang, 2014 ; Liao et al., 2014 ; Negoi et al., 2014 ). Using direct hydrogenation of cellulose and hemicellulose would eliminate the capital and operating costs associated with pretreatment and hydrolysis reducing production costs by $1.09/gal. Direct hydrogenation of pulp combined with a doubling of process capacity reduces costs to $2.44/gal, which still exceeds the target value of $2.04/gal. Additional cost savings could be achieved by developing a process for direct hydrogenation of unsorted paper. This innovation would eliminate repulping costs and sorting costs. Direct hydrogenation of unsorted paper would reduce production costs to $2.31/per gal, which is $1.80/gal reduction from the nominal value. Hydrogenation of unsorted paper combined with increased plant capacity could bring production costs down to $1.71.
Environmental Impact
We performed a lifecycle analysis to determine net carbon dioxide emissions and solid waste generation. The analysis was limited to the combined emissions from jet fuel and paper production assuming current levels of use. We based the analysis on the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model ( Energy Systems Division, 2014 ). Pathways not related to jet fuel production and use were eliminated from the GREET model; and pathways for paper production, use, and disposal were added. GREET was the primary data source supplemented with additional data for emissions and solid waste generation for the paper pathways ( Suhr et al., 2010 ; Bajpai, 2014 ; US Environmental Protection Agency, 2018 ; Kinstrey and White, 2006 ) and solid waste from biomass ( Lizotte et al., 2015 ). Emissions and solid waste associated with the conversion of biomass and recycled paper to jet fuel were based on the material and energy balances discussed in the previous section. Estimates of net solid waste production for the paper to jet processes account the reduction in paper waste currently been disposed of in landfills.
Table 9 gives the carbon dioxide emitted and solid waste generated from the three jet fuel processes evaluated in this study. The paper to jet fuel process with acid hydrolysis emits 2.4 times as much carbon dioxide as the process with enzymatic hydrolysis. The difference is the result of the high electrical power consumption of RW-EDI in the process with acid hydrolysis to recover and recycle sulfuric acid. Because the paper to jet fuel processes consume paper from municipal solid waste, net solid waste generation is negative.
TABLE 9 . Carbon dioxide emissions and solid waste production for corn stover to jet fuel and paper to jet fuel processes.
We analyzed four scenarios to determine the combined carbon dioxide emissions and solid waste generation of commercial air transportation and the paper industry in the US.
• Baseline– The baseline scenario was the current case in which jet fuel is produced from petroleum and paper is produced from a combination of virgin and recycled pulp.
• Scenario 1 –All recyclable paper not currently recycled domestically and degraded pulp from recycling plants are converted into jet fuel and the balance of the US jet fuel demand is obtained from petroleum. Paper is produced from the current combination of virgin paper and recycled pulp.
• Scenario 2 –All discarded paper available for recycle is converted into jet fuel and the balance of the jet fuel demand is obtained from petroleum. All paper is produced in the US from virgin pulp.
• Scenario 3 –The same volume of renewable jet fuel produced in this scenario as produced in Scenario 2, but only paper not recycled domestically is converted into jet fuel. The additional renewable jet fuel is produced from corn stover. The balance of the US jet fuel demand is obtained from petroleum. Paper is produced from the current combination of virgin paper and recycled pulp.
• Scenario 4 –The same volume of renewable jet fuel produced in Scenario 2 is produced from the corn stover biomass. The balance of jet fuel needed domestic demand is obtained from petroleum. Paper is produced from the current combination of virgin and recycled pulp.
The results of the lifecycle analysis for these scenarios are summarized in Table 10 . Because of the high carbon dioxide emissions from the paper to jet fuel process with acid hydrolysis, we only present results from the process with enzymatic hydrolysis. Scenario 4, in which all renewable jet fuel is produced from corn stover, results in the lowest level carbon dioxide emissions. As shown in Table 9 , lifecycle carbon dioxide emissions jet fuel produced from corn stover are less than for jet fuel produced from recycle paper. US paper recycled in other countries also contributes to the reduction in emissions. However, considering the uncertainty in the analysis, carbon dioxide emissions for Scenarios 2, 3, and 4 are not significantly different. Scenario 1, in which domestic paper recycle is maintained at current levels, produces the minimum amount of solid waste. Producing virgin pulp generates significantly more solid waste than repulping recycled paper, and producing jet fuel from corn stover produces more solid waste than recycling paper into jet fuel. Scenarios 2 and 3 also produce significantly less solid waste than the baseline scenario.
TABLE 10 . Results for the lifecycle analysis of jet fuel and paper production and use. The analysis is based on the paper to jet fuel process with enzymatic hydrolysis.
Scenario 3, in which jet fuel is produced from recycled paper and corn stover, is probably the best from an environmental and social perspective. It reduces net carbon dioxide emissions from the US air transportation industry by 15% without increasing logging for virgin paper production or disrupting the domestic paper recycling industry. It also eliminates paper destined for landfills reducing total solid waste destine for landfills by 6%.
Recycle paper has advantages over agricultural residue, such as corn stover, as a cellulosic feedstock for fuel production. Efficient and reliable technology exists in the recycle paper industry for converting paper into fibers suitable for chemical conversion. Unlike equipment for handling and preprocessing of corn stover, industrial experience demonstrates that repulping equipment has high availability. The combination of proven repulping technology, the high cellulose content of paper, and existing supply network gives recycle paper a significant economic advantage over corn stover and other sources of lignocellulosic biomass. Net lifecycle carbon dioxide emissions of paper derived fuels are comparable to corn stover derived fuels, and paper generated significantly less solid waste.
A key disadvantage of producing jet fuel from paper is its limited supply, so it can only satisfy a fraction of the total demand. More importantly, the cost of producing jet fuel from recycle paper is not competitive with petroleum using current technology.
Our sensitivity studies have shown that the key to a competitive paper to jet fuel process is direct hydrogenation of cellulose and hemicellulose to sugar alcohols. Direct hydrogenation of cellulose would reduce capital and operating costs. Several researchers have explored direct catalytic hydrogenation of cellulose, but considerably more work is needed convert this idea into a practical industrial process. Direct hydrogenation of cellulose and hemicellulose combined with greater economy of scale could make paper to jet fuel comparative. In this study we have only considered the paper to jet fuel via sugar alcohols as an intermediate. Another possibility is a process with furfural and 5-methylfurfural or levulinic acid as intermediates. Such a process would eliminate hydrolysis as a separate processing step and reduce hydrogen consumption. This alternative route warrants consideration.
Perhaps the biggest value of developing a process to convert recycle paper into hydrocarbons is its use as a method of jumpstarting a cellulosic biofuels industry. The process chemistry for producing fuels from paper is the same as lignocellulosic biomass. Developing a paper to jet fuel process would provide an opportunity for demonstrating the process chemistry at an industrial scale without the need to develop a new supply chain for lignocellulosic biomass or solve all the current problems involved with handling and preprocessing lignocellulosic biomass. The process would also be useful for reducing municipal solid waste.
Data Availability Statement
The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.
Author Contributions
The concept of converting recycle paper into jet fuel and the technical approach to the problem were the result of discussions among WK, CM, TS, and AS. WK developed idea and executed the analysis including the material and energy balances, the techno-economic analysis, and the life cycle analysis.
This work was supported by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Bioenergy Technologies Office (program Award Number NL0033622). Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218CNA000001).
Conflict of Interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s Note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
Acknowledgments
The authors thank members of the Los Alamos National Laboratory Biomass Conversion Team for their review and suggestion. The author also thanks Travis Moulton of the Process Modeling and Analysis Group at Los Alamos for his review of this manuscript.
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Nomenclature
APR Aqueous-phase reforming
FCI Fixed capital investment
FOB Cost Purchased equipment cost–freight on board
GREET Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation
NREL National Renewable Energy Laboratory
RW-EDI Resin Wafer Electrodeionization
TCI Total Capital Investment.
Keywords: recycled paper, municipal solid waste, cellulosic biomass, renewable jet fuel, renewable hydrocarbons, techno-economic analysis
Citation: Kubic W, Moore C, Semelsberger T and Sutton A (2021) Recycled Paper as a Source of Renewable Jet Fuel in the United States. Front. Energy Res. 9:728682. doi: 10.3389/fenrg.2021.728682
Received: 21 June 2021; Accepted: 23 September 2021; Published: 12 October 2021.
Reviewed by:
Copyright © 2021 Kubic, Moore, Semelsberger and Sutton. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: William L. Kubic Jr., [email protected]
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