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How to Write a Research Paper

Writing a research paper is a bit more difficult that a standard high school essay. You need to site sources, use academic data and show scientific examples. Before beginning, you’ll need guidelines for how to write a research paper.

Start the Research Process

Before you begin writing the research paper, you must do your research. It is important that you understand the subject matter, formulate the ideas of your paper, create your thesis statement and learn how to speak about your given topic in an authoritative manner. You’ll be looking through online databases, encyclopedias, almanacs, periodicals, books, newspapers, government publications, reports, guides and scholarly resources. Take notes as you discover new information about your given topic. Also keep track of the references you use so you can build your bibliography later and cite your resources.

Develop Your Thesis Statement

When organizing your research paper, the thesis statement is where you explain to your readers what they can expect, present your claims, answer any questions that you were asked or explain your interpretation of the subject matter you’re researching. Therefore, the thesis statement must be strong and easy to understand. Your thesis statement must also be precise. It should answer the question you were assigned, and there should be an opportunity for your position to be opposed or disputed. The body of your manuscript should support your thesis, and it should be more than a generic fact.

Create an Outline

Many professors require outlines during the research paper writing process. You’ll find that they want outlines set up with a title page, abstract, introduction, research paper body and reference section. The title page is typically made up of the student’s name, the name of the college, the name of the class and the date of the paper. The abstract is a summary of the paper. An introduction typically consists of one or two pages and comments on the subject matter of the research paper. In the body of the research paper, you’ll be breaking it down into materials and methods, results and discussions. Your references are in your bibliography. Use a research paper example to help you with your outline if necessary.

Organize Your Notes

When writing your first draft, you’re going to have to work on organizing your notes first. During this process, you’ll be deciding which references you’ll be putting in your bibliography and which will work best as in-text citations. You’ll be working on this more as you develop your working drafts and look at more white paper examples to help guide you through the process.

Write Your Final Draft

After you’ve written a first and second draft and received corrections from your professor, it’s time to write your final copy. By now, you should have seen an example of a research paper layout and know how to put your paper together. You’ll have your title page, abstract, introduction, thesis statement, in-text citations, footnotes and bibliography complete. Be sure to check with your professor to ensure if you’re writing in APA style, or if you’re using another style guide.


research on recycling of paper

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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:

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


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.


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.

research on recycling of paper

FIGURE 5.9 . Schematic drawing of paper pulping (beater) machine

research on recycling of paper

FIGURE 5.10 . Schematic drawing of air injection flotation cell

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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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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).

research on recycling of paper

European paper recycling 1995-2009 in million tonnes (European Declaration on Paper Recycling 2006 – 2010, Monitoring Report 2009 (2010) (

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.

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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.

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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 ).

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Changes in fiber wall structure ( Weise &Paulapuro 1996 )

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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.

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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.

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Influence of recycling number and drying temperature on length of softwood pulps

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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).

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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

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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.


This work was financed by the Slovak Grant Agency VEGA (project number 1/0490/09).

© 2011 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike-3.0 License , which permits use, distribution and reproduction for non-commercial purposes, provided the original is properly cited and derivative works building on this content are distributed under the same license.

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Recycling the waste of paper into usable board

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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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Does Paper Actually Get Recycled? The Industry Answers.

You put your recycling in the bin and drop it at the curb. Does it actually get recycled?

Yes! At paper mills across the country, recycled paper is used to make the essential products millions of people rely on.  

How Paper Recycling Works

After your local recycling hauler picks up your recycling, it’s taken to a materials recovery facility (MRF) where it’s sorted into like things.

Workers remove items that shouldn’t be there, also called contaminants. That includes things like plastic bags, holiday lights, diapers and even bowling balls. 

Paper is often separated first and sorted into groups for cardboard, mixed paper, office paper, etc. Then, the paper is baled and shipped to a paper mill where it’s turned into new paper products . 

Paper Recycling is a Success Story

A pie chart showing where recycled paper goes with containerboard being 41.1%.

In 2021, the paper recycling rate was 68% - a rate on par with the highest rate previously achieved. Nearly half of recycled paper went into manufacturing containerboard – the material used to make cardboard boxes.

Recycled paper is also used to make boxes for dry foods like cereal or pasta, tissue products like toilet paper and paper towels, as well as newspapers.  

80% of U.S. paper mills use some recycled paper to make new and innovative products!

As the most recycled material in the U.S., paper is a practical and sustainable choice.

What Can You Do?

Doing your part – recycling dry and clean paper products – ensures this process keeps going.

A key to this process is making sure you’re recycling properly. Check your local municipality’s website to understand what’s accepted in your area.

And when it comes to paper items: keep them dry and clean, then put them in the recycling bin!

Industry Voices

Brave conversations about diversity in the paper and wood products industry.

“Diversity in any industry creates visible representation,” Gabrielle Evans said. We sat down with her, Marcez Mitchell and Marlon Jones from International Paper to get their candid thoughts on diversity in the paper and wood products industry, how they celebrate Black History Month and more.

Fostering Diversity and Inclusion in the Paper Industry

Procter & Gamble’s Senior Vice President, Product Supply-Family Care, Regina Gray highlights how diversity in skills and in employees can help elevate companies in the paper and wood products industry.

AF&PA Releases January 2023 Printing-Writing Monthly Report

Total printing-writing paper shipments decreased 9% in January compared to January 2022. U.S. purchases of total printing-writing papers increased 3% in January compared to the same month last year.



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Environmental assessment of innovative paper recycling technology using product lifecycle perspectives.

research on recycling of paper

1. Introduction

1.1. innovative paper recycling technology (development of the dry paper recycling technology that realizes a new office papermaking system), 1.1.1. defibration processing, 1.1.2. binding processing, 1.1.3. forming processing, 2. materials and methods, 2.1. scope of evaluation and functional units, 2.2. system boundary, 2.3. database and activity data, 2.3.1. office paper-making machine, 2.3.2. bonding agent, 2.3.3. power consumption at the paper-making stage, 3.1. co 2 emissions, 3.2. water consumption, 4. discussion, 5. conclusions, author contributions, conflicts of interest.

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Ono, Y.; Hayashi, M.; Yokoyama, K.; Okamura, T.; Itsubo, N. Environmental Assessment of Innovative Paper Recycling Technology Using Product Lifecycle Perspectives. Resources 2020 , 9 , 23.

Ono Y, Hayashi M, Yokoyama K, Okamura T, Itsubo N. Environmental Assessment of Innovative Paper Recycling Technology Using Product Lifecycle Perspectives. Resources . 2020; 9(3):23.

Ono, Yuya, Masaaki Hayashi, Koichiro Yokoyama, Takehiko Okamura, and Norihiro Itsubo. 2020. "Environmental Assessment of Innovative Paper Recycling Technology Using Product Lifecycle Perspectives" Resources 9, no. 3: 23.

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paper recycling Recently Published Documents

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Using lignocellulosic materials for producing more value-added bioproducts is an attractive mission. Fiber fines, which represent an important part of the wastes generated by paper recycling mills, have been considered in the current research. Dissolving these lignocellulosic residues in environmentally friendly and inexpensive solvents can be a great achievement. For this purpose, the performance of urea/sodium hydroxide in dissolving printing and writing pulp (RPW) fines was investigated. Although using sodium hydroxide alone had a positive effect on the dissolution of recycled printing and writing pulp (RPWP) fines, the addition of urea increased the dissolution of fines from 23% to 56%. Different levels of urea consumption had no significant effect on the dissolving process. The performance of the urea/sodium hydroxide system in dissolving fines suspensions with different concentration (1, 3 and 5%) showed that reducing the concentration leads to an increase in fines dissolution (56, 36 and 7%, respectively). The results of FTIR confirmed the presence of cellulose without any hemicelluloses and lignin in the dissolving part. The results of X-ray diffraction analysis of soluble cellulose showed that the type-I cellulose structure probably changed to type-II cellulose. No reduction in the DP of dissolved cellulose and the integrated structure of the final cellulosic film confirmed by the FE-SEM images affirmed the successful dissolution of the RPWP fines in this system.

Particle removal optimization in rotating dissolved air flotation used in paper‐recycling wastewater treatment

Biodeinking kertas koran bekas menggunakan ekstrak kasar lakase dari marasmiellus palmivorus.

Biodeinking of Old Newspaper using Crude Laccase from Marasmiellus palmivorus   Abstract Enzymatic deinking is receiving growing attention due to the negative environmental impact caused by chemical deinking. Old newspaper (ONP) is one of the materials that can be used in paper recycling. The use of the crude laccase from Marasmiellus palmivorus in biodeinking is due to its capability to remove the ink. The objective of this research was to determine the potential use of laccase in enzymatic deinking to increase the brightness value and reduce ERIC (Effective Residual Ink Concentration) value on old newspapers. Laccase was produced from M. palmivorus by using cultivation in a static Solid State Fermentation (SSF) reactor with lignocellulosic as substrate. The methodology involves the production of crude laccase extract, laccase optimization using variations of dosage, temperatures, and times. The highest laccase activity is 1,142.86 U/L (16 U/mg). Optimization of laccase crude extract enzyme in biodeinking can increase brightness values by 15.22% (54.27 %ISO) to 25.03% (58.89 %ISO) compared to controls (47.09% ISO) and reduce ERIC values by 46.12% (452.1 ppm) to 68.26% (266.4 ppm) compared to control (839.2 ppm). Keywords: biodeinking, Marasmiellus palmivorus, laccase, old newspaper Abstrak Deinking enzimatis semakin mendapat perhatian karena dampak negatif terhadap lingkungan yang disebabkan oleh deinking secara kimia. Kertas koran bekas merupakan salah satu bahan yang dapat didaur ulang. Pemanfaatan ekstrak kasar lakase dari Marasmiellus palmivorus digunakan dalam biodeinking karena memiliki kemampuan untuk menyisihkan tinta. Penelitian ini bertujuan untuk mengetahui potensi ekstrak kasar lakase untuk meningkatkan nilai brightness (derajat cerah) dan menurunkan nilai Effective Residual Ink Concentration (ERIC) dalam proses biodeinking kertas koran bekas. Produksi ekstrak kasar lakase dilakukan dalam reaktor statis Solid State Fermentation (SSF) dengan substrat material lignoselulosik. Produksi ekstrak kasar lakase menghasilkan aktivitas tertinggi 1.142,86 U/L (8,33 U/mg). Perlakuan biodeinking dengan enzim ekstrak kasar lakase dapat meningkatkan nilai derajat cerah 15,22% (54,27 %ISO) sampai 25,03% (58,89 %ISO) dibandingkan dengan kontrol (47,10 %ISO) dan menurunkan nilai ERIC 46,12% (452,1 ppm) sampai 68,26% (266,4 ppm) dibandingkan dengan kontrol (839,2 ppm). Kata kunci:  biodeinking, Marasmiellus palmivorus, lakase, kertas koran bekas

Manual Operated Paper Recycling Machine

The production of enormous quantities of waste papers is evident in any large institution, particularly educational institutions such as schools or universities. It's also feasible to make good use of recycled paper (craft papers, registers etc). So, rather than throwing away the waste papers, recycling them makes sense. A paper-recycling machine that may be operated manually was conceived and built. This was done to allow for the conversion of waste paper into a useful product in the home. The machine unit's design has been created in accordance with all essential component requirements. In addition, the overall cost is minimal, and there is no requirement for power.


Waste paper recycling is an important way to realize the environmental protection development of the papermaking industry. The quality of the pulp will affect the pulp sales of the secondary fiber paper mills. The waste paper pulp can be adjusted by controlling the pulping process working conditions, but the working conditions of the waste paper pulping process have too many parameters. And the parameters are coupled with each other, it is difficult to control. In order to find the best working conditions and improve the quality of the pulp, this study uses the association rules algorithm to optimize the parameters for the waste paper pulping process. These parameters are power of refiner, waste paper concentration of refiner, the volume of slurry that enters deinked process, deinking agent amount, deinking time, deinking temperature, bleaching agent amount, bleaching time, and bleaching temperature. The test results show that the qualified rate of the pulp produced under the improved working conditions is 92.56%, an increase of 6.93%, and the average electricity consumption per ton of pulp is reduced by 5.76 kWh/t. In addition to potential economic benefits, this method can reduce carbon emissions.

Critical study of energy efficient industrial waste-paper recycling process

Paper utilized every day with learning establishments; for example, colleges and schools being the primary users. Because of its single utilization, it winds up being arranged in a large portion of the paper squander. There is a total 8 percent increase in consumption of paper in recent years in India. According to a paper mart survey report, India is producing around 22 million tons of paper per year. This production leads to the demand for recycling the paper waste. In this paper, smart paper recycling process in the industry is discussed. It involves recycling process of paper waste to producing a useful product. The paper gives the management process and the technique that can be used with the new innovative design and production compared with the existing paper recycling machine. The advantages of the device are not just fixated on the benefits of reusing paper but also lead to improvement by technology advancement.

Fermentation-pyrolysis of fibre waste from a paper recycling mill for the production of fuel products

The impact of waste paper recycling on the carbon emissions from china’s paper industry, application of innovative design thinking in product design* intelligent waste paper recycling machine design case.

With the rapid development of society and economy, the level of technology and culture in our country is constantly improving, and the content of product design extends from the product appearance design to the design of a whole system of product function, structure, material, production crafts, marketing, maintenance and recycling. The product innovation design thinking should not only consider a single factor, but also integrate the latest achievements in all aspects of the product design ecosystem. The research on innovative thinking and innovative design methods from all walks of life is also constantly systematized and theorized, but the innovative design thinking of products has different thinking characteristics and methods from other fields. This article combines product design examples of intelligent waste paper recycling machines to explore the application of innovative thinking methods in product design.

Issue paper: recycling of different wastestreams

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