Life-cycle inventory of toner produced for xerographic processes

Journal of Cleaner Production 11 (2003) 573–582www.cleanerproduction.net

Life-cycle inventory of toner produced for xerographic processes

A. Ahmadia,∗, B.H. Williamsonb, T.L. Theisc ,†, S.E. Powersd

a Environmental Manufacturing Management; Department. of Civil and Environmental Engineering, Clarkson University, Potsdam,NY 13699, USA

b Environmental Manufacturing Management; Department. of Chemical Engineering, Clarkson University, Potsdam, NY 13699, USAc Center for Environmental Management; Department. of Civil and Environmental Engineering, Clarkson University, Potsdam, NY 13699, USA

d Department of Civil & Environmental Engineering, Clarkson University, Potsdam, NY 13699, USA

Received 27 November 2001; accepted 5 July 2002

Abstract

This paper reports on the methodology and results of a baseline life-cycle inventory (LCI) performed on toner used in thexerographic process. Toner is the dry ink that creates the image on paper and is used in most copiers and some large printers. Thegoal is to perform an LCI on a system that encompasses the life-cycle of toner in order to determine the environmental effectsrelated to the product. The findings of the study show that the system is mainly a classical “cradle to grave” model, althoughrecycle streams within the system improve the overall environmental performance. The majority of the solid process waste produced(95%) is associated with post-toner production processes, and the majority of the air emissions in the system resulted from energyuse. Post-production processes combine for just over 85% of the total energy used in the system, with customer use accountingfor 58% of the total. 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Life-cycle inventory; Xerography; Toner

1. Introduction

The xerographic industry has seen remarkableadvances in speed and quality of image production inthe past few decades. This technology is still improvingtoday with many companies competing for the future incopy and print technology. One of the main componentsin the xerographic process is the marking material, ortoner. Toner is dry ink that creates the image on paperduring the xerographic process used in most copiers andsome large printers. It consists of small particles in thesize range of 8–13 micrometers, and is composed ofthree basic raw materials—polymer, colorant (pigments),and small amounts of additives that help to control theimage quality. A diagram of a general toner particle is

∗ Corresponding author.E-mail address: [email protected] (A. Ahmadi).

† Present address: Institute for Environmental Science and Policy,University of Illinois at Chicago, 2121 West Taylor Street, Chicago,IL 60657, USA.

0959-6526/03/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved.doi:10.1016/S0959-6526(02)00090-2

shown in Fig. 1. The specific toner for this analysis waschosen due to its high production volume and its use inmany of the xerographic machines with high throughput.

Working in conjunction with an imaging technologycorporation, it was requested by toner plant engineers

Fig. 1. Composition of toner particles.

574 A. Ahmadi et al. / Journal of Cleaner Production 11 (2003) 573–582

and upper management that the conventional manufac-turing process of toner be evaluated to determine wherethe greatest environmental concerns lie. Quantifying theimprovements associated with recent recycling initiat-ives was also desired. The conventional method of tonerproduction is a process by which particles are mechan-ically fractured to the desired size distribution. Therewere specific industrial concerns regarding energy usedand solid waste generated within this process. However,the manufacturing process for toner production is pro-gressing as the industry advances and as environmentalconsiderations become more important. To evaluate theenvironmental performance of future technologies, thecurrent technology must be evaluated as a baseline. Thetool chosen to carry out the baseline evaluation is thelife-cycle assessment (LCA). This paper focuses on theinventory phase of the LCA, specifically the material andenergy inputs into the system, along with the wastes pro-duced and by-products leaving the system. These resultswould determine if the concerns over energy uses andsolid waste generated during the manufacturing and useof toner are valid. Therefore, the objectives of the studywere to:

1. Establish the boundaries of the life-cycle of toner par-ticles, including all materials and energy required,along with the wastes and by-products produced.

2. Determine areas within the system that have highemissions, material consumption, or energy use lev-els.

3. Present the resulting data as a baseline in a mannerthat it could be used to compare the current systemto alternative systems and technologies.

2. Background

2.1. Life-cycle assessment

A LCA provides a family of methods for evaluatingmaterials, services, products, processes, and technologiesover their entire life [1]. The main goal of an LCA is toevaluate the environmental impacts of a particular pro-cess or product from the point where raw materials areextracted from the earth, through manufacturing of theproduct, its use, and the disposition of residual materials.There are four main parts to an LCA: scoping, inventoryanalysis, impact analysis, and improvement. Duringscoping, initial boundaries are set and objectives aredefined. Determining the boundaries of the project is acritical step in the LCA, and is based on a number offactors including the goals and scope of the project, theavailability of data, and the time and resources availableto fill in the data gaps. Inventory analysis is usuallyquantitative and consists of thorough mass and energybalances on the system. Developing valid approxi-

mations for gaps in the data is critical in this phase ofthe assessment. Impact analysis involves associatinginventory analysis data with their corresponding poten-tial environmental impacts, and then using quantitativeand qualitative methods to determine the extent of theenvironmental impacts associated with the system. Forexample, is a process with a high-energy consumptionrate better than a process with high material require-ments? The answer may depend on many factors, suchas local environmental issues, types of material used, andsources of power. It is clear that this is a complex pro-cess, thus the impact component of the LCA has alwaysbeen very subjective [2]. Therefore, the focus of thispaper is on the inventory phase, with minimal emphasison the impact. Finally, based on the results, optimizationand improvement of the system are explored and rec-ommendations are made.

It is important to understand that there are limitationswith LCA. The methodology has been described as toocomplex and data-intensive [3]. It is also often difficultto differentiate among the critical environmentalimpacts. However, LCA has emerged as an importanttool to aid decision makers in their choice of future pro-ducts and processes. Among other uses, the LCA assistsin evaluating processes or products with similar func-tions to determine which is environmentally preferred.

2.2. Xerography

At the center of the life-cycle of toner is the actualxerographic process. A schematic of this process isshown in Fig. 2. Xerography begins by imparting a posi-tive charge to a photoconducting belt with a corona wire(#1 in Fig. 2). Photoconducting materials behave likeinsulators when kept in the dark and are more conductivewhen exposed to light. Using this property the imagethat is to be copied is exposed onto the belt such thatlight dissipates the charge on the belt in areas of theimage without print (#2). A “ latent electrostatic image”is now on the belt. The negatively charged toner is thenintroduced to the positively charged image on the belt(#3). Due to the opposite charges, the toner adheres tothe image. This leaves a “ toner image” of the originalon the belt. The paper is then charged with the coronawire and introduced to the belt (#4). The “ toner image”on the belt is then transferred to the paper, again usingthe charge differences as the driving force. The “ tonerimage” that is now on the paper proceeds through thefuser rolls, which fix the toner onto the paper (#5). Thefinal step in this process is cleaning the belt (#6), wherethe remaining toner on the photo-conducting belt isremoved from the belt and transferred to a waste bin inthe xerographic machine.

575A. Ahmadi et al. / Journal of Cleaner Production 11 (2003) 573–582

Fig. 2. The xerographic process.

3. Research methodology

The first step in performing an LCA is to define theboundaries of the system. The system as a whole isshown in Fig. 3. The system boundaries were initiallydrawn around the manufacturing process of the toner.The boundaries were then extended upstream to includeall processes needed to manufacture the raw materialsfor the toner manufacturing process such that thematerial inputs of the system were either by-products ofanother process or were materials from the processingof natural resources. The upstream boundary does notinclude the mining and extraction of the naturalresources (specifically petroleum, natural gas, and rocksalt). The boundaries were then extended downstream toinclude post manufacturing processes such as customeruse, paper recycling, and the toner recovery process. Thesystem was then grouped into six sections and evaluated

Fig. 3. The system: life-cycle of xerographic toner.

for both material and energy demands, along with by-products and wastes produced: carbon black production,magnetite production, resin production, toner manufac-turing, consumer use, and end-of-use processing. Trans-portation of material between these sections was alsoconsidered. The sections are described in detail belowemphasizing data collection methods, assumptions made,and calculations used in producing the final results.

The data categories analyzed in this report are: energyuse, which includes fossil fuel use and electricity; CO2

emissions, which is a major contributor to global warm-ing; NOx and SO2 emissions, both of which cause acidrain which is a threat to many lakes and forests; VOCsand particulate emissions, which are local air pollutants;wastewater volume, which must be treated before it isreleased back into the environment; and solid waste,which would enter the local solid waste managementsystem. Air emissions from energy production were cal-


culated using emission factors developed by theEnvironmental Defense Fund [4]. These categoriesencompass the substantial emissions from the systemthat have significant environmental consequences.

The functional unit used in the data calculations wasone metric ton of toner produced. The current state ofthe technology for toner usage is such that one metric tonof toner will produce an average of 22 million imagesassuming standard letter sized paper and a 6% coveragearea [5]. It is important to note that this assessment isonly on the toner that is used as a marking material inthe production of documents, not on the production ofa document. Other materials, most notably the paperused and the xerographic machine, would have to beaccounted for in a life-cycle assessment of a document.

3.1. Toner manufacturing

The toner manufacturing process is summarized inFig. 4, showing mass flows into and out of the process.In toner manufacturing, the raw materials (resin, magnet-ite, and/or carbon black) are pre-blended and transferredinto a compounding process. The compounder has thedual purpose of mixing and heating the material into ahomogeneous polymer melt. The melt is then cooled toform solid pellets that have a size range on the order ofa few millimeters. The pellets are then placed into agrinding process, which resembles a fluidized bed wherethe pellets are constantly colliding with one another andpieces of the pellets become fragmented into themicrometer size range. Following this is the classi-fication process, where the desired size distribution iscreated. Particles that are too large are returned to thegrinding process; particles that are too small are sent toa separate compounding process and are then returnedback to the grinding process or are fed back to the com-pounding process directly. Toner particles are thenscreened, where any left over aggregates are removedand recycled back into the process. Particles within thedesired size distribution are transferred to a packagingline where the bulk toner is packaged and sent to theconsumer [5].

In order to reduce wastes and improve toner manufac-turing, the industry has taken steps to incorporate recyc-ling where possible. There are two key recycling loops

Fig. 4. Toner manufacturing process.

that occur in the manufacturing process. One loop isinternal, where toner waste is recycled from the grinderand classifier/screener to a fines recycling process andback into the system. The other loop is external, wheretoner waste from the consumer is sent to a screeningprocess and then recycled back into the manufacturingprocess to offset some of the raw materials.

A mass balance was performed based on the mainsteps of the toner manufacturing process as shown inFig. 4. Both internal and external recycling streams wereincluded in the analysis. The mass balance was calcu-lated using the process yield information for the individ-ual steps in the production process. Raw materialrequirements and intermediate material flows for the pro-duction of a specified amount of product were determ-ined. The material flows were labeled and normalized tothe functional unit (one metric ton of toner produced).The overall process yield for toner manufacturing wascalculated to be 96–98%, thus the amount of solid wasteproduced was relatively low. Determining the totalamount of energy consumed during toner manufacturingrequired collecting data using the nameplate informationon all pumps and motors used in the process in order toestimate the energy usage rate. This rate, along with thedesign rate (the throughput of each machine), and theresults from the mass balance were used to calculate theamount of energy needed to produce one metric ton oftoner.

3.2. Raw materials processing

The three main raw materials used to produce theparticular toner studied here are the polymeric resin(80%), magnetite (17%), and the carbon black pigment(3%) [6]. The resin makes up the bulk of the toner par-ticle and is the key to the xerographic process. The meltcharacteristics of the resin enable the toner to bond withthe paper in the xerographic machine. The magnetite andcarbon black are both pigment materials, but the magnet-ite also increases the particles’ ability to develop acharge, which is another important aspect in the xero-graphic process. A charge control agent is also used inthis toner, but the weight percent is small (0.2% of total),and the material (a specialty salt) is relatively benign innature thus the material was neglected. The productionprocesses associated with manufacturing each rawmaterial are described separately below.

3.2.1. Resin productionThe resin used in the production of the toner particles

is a copolymer of styrene and butadiene. The most com-mon manufacturing process for this resin is a batchemulsion polymerization process [7]. The overall pro-cess yield (resin produced / monomer input) is 98%, withthe remainder lost as solid waste. For the energy use ofthe manufacturing process, pump sizes were again used,


along with the energy needed to heat the reaction slurryto the reaction temperature. The total energy used isassumed to be correct for an order of magnitude approxi-mation, which will be shown appropriate when compar-ing these results with other processes within the systemthat have high energy use.

The material needs for the resin manufacturing pro-cess are mainly styrene and butadiene. There are someadditives present in small quantities, but these wereagain assumed to be benign in nature. The styrene andbutadiene required for the production of the resin areboth derived from organic chemical production and sep-aration methods. Both materials start with products fromthe steam cracking of ethane that was separated fromnatural gas [8]. The main product of the cracking processis ethylene, although many other by-products are alsoproduced. One of the by-products from the cracking pro-cess is 1,3-butadiene, which is present in the C4 fraction[9]. The butadiene must be separated from other com-pounds present in the C4 fraction, most notably isomersof butane and butene. The most common method of sep-aration used in industry today is extractive distillation.The resulting material flows through this system showvery little material losses other than fugitive emissions.For all organic processes within the life-cycle, the fugi-tive emissions were calculated as a percentage of thetotal organic material present, according to the boilingpoint of the material, and listed as VOCs [10]. Thebutanes, butenes, and other residual organic materials arealso separated in the process and used as by-products.Energy use for this process is also low since the boilingpoints of the materials involved are all near room tem-perature.

The ethylene produced in the steam cracking of ethaneis one of the two chemicals used in the production ofethylbenzene, which is later converted to styrene. Theother is benzene, which is obtained directly from arefinery. The most common process used for the forma-tion of ethylbenzene is called the Mobile–Badger pro-cess [11]. The main by-product of this process is a mixedhydrocarbon stream, which can be used as fuel for heat-ing the process stream. The energy required in heatingthe reactants to the process temperature was calculatedto estimate energy use in this step. The energy used inthis step was assumed to be derived from the burning offossil fuels, or more specifically from mixed organicwaste streams from the process.

The main use for ethylbenzene is in the production ofstyrene. The most common industrial process for thisconversion is an adiabatic dehydrogenation reaction ofethylbenzene with steam [12]. The elevated temperaturesat which the reaction occurs (540–650 °C), in additionto the endothermic nature of the reaction, require sig-nificant heat inputs. The main by-products of the processare benzene and toluene, which can be separated or con-verted to all benzene, and a residual hydrocarbon stream,

which can be used as a fuel source for the system. Theenergy required for the process was again assumed to bederived from fossil fuels and approximated as the energyneeded in heating the reactants to the reaction tempera-ture and the heat required to compensate for the endo-thermic reaction in the reactors.

3.2.2. Magnetite productionMagnetite (Fe3O4) is a natural occurring form of iron

ore. The purity required to use magnetite as a pigment,however, requires alternative methods of production.One method used to produce pigment grade magnetiteis a precipitation reaction of iron sulfate (FeSO4) withsodium hydroxide [13]. Iron sulfate is a byproduct oftitanium dioxide production that uses ilmenite as the rawmaterial. The wastewater from the process contains largeamounts of residual salts from the precipitation reaction.The material in the wastewater is mainly sodium sulfatefrom the reaction, with some sodium hydroxide andmagnetite fines present. The sodium sulfate in the waste-water is recovered as a by-product of the process [14].On a mass scale, three pounds of sodium sulfate arepresent in the wastewater for every pound of magnetiteproduced by this process. The energy use is approxi-mated as twice the amount of energy needed to heat thereaction slurry to the reaction temperature to account forthe temperature needed to hold the slurry at the reactiontemperature and dry the resulting product.

The sodium hydroxide used in the magnetite pro-duction process is produced as a co-product of the pro-duction of chlorine gas by electrolysis [15,16]. The caus-tic solution produced in the electrolysis process isusually concentrated to 50-wt% NaOH during postpro-duction. The energy requirements for the process havebeen documented as 2850 kW-h/ton of chlorine gas [17].The chlorine and hydrogen gas produced are also soldas products, thus the energy used specifically for produc-ing the caustic solution is assumed to be 50% (theapproximate weight percentage of NaOH in the totalproducts) of the energy used in the electrolysis process.

3.2.3. Carbon black productionThe carbon black manufacturing process uses high

temperatures (2000 °C) to break down a hydrocarbonfeedstock to elemental carbon [18]. The carbon blackfeedstock, which is obtained directly from a refinery, iscomposed of aromatic hydrocarbons and thus has a highcarbon to hydrogen ratio (8:1). Natural gas is used toheat an air stream and remove the oxygen present. Theair is then directly used to vaporize and decompose thefeedstock to carbon black. Once the process stream hasreacted, the carbon black is removed from the processair and pelletized. Any impurities are removed bothmagnetically and mechanically (screened) before theproduct is finished. The emissions from this process aremainly from the process air, which can be incinerated


for energy recovery. The composition of the incineratedprocess air is mainly CO2, H2O, and N2, with significantamounts of particulate, VOC, NOx and SO2 emissionspresent [19]. The main energy requirement for this pro-cess is in vaporizing the feedstock with the natural gas.The quantity of natural gas used by the process was con-verted to the heat obtained from the combustion of thegas to comply with the units of energy use by the system.

3.3. Post-production processes

The post-production processes begin once the manu-factured toner is sent to the consumer. The boundariesof the life-cycle extend to the point where the productresiduals are disposed or deposited. Post-production pro-cesses therefore include the use of the toner in the xero-graphic machines, the destination of waste toner left inthe machines, and the final destination of the toner thatis transferred onto the paper (Fig. 5).

3.3.1. Consumer useThe internal functions of the xerographic machine

were described previously. The most important factors toconsider in the LCA are the energy usage during imageproduction, the transfer efficiency of the toner to thepaper, and the amount of toner used to produce an aver-age image on a page.

The main energy requirements for the machine arefrom the exposure of the image onto the belt, and fromthe fuser rolls, where heat and pressure are used to fixthe toner to the paper. Most machines have threeoperating modes: running, stand-by, and low power. Theenergy drawn while operating in the three modes (7440,1920, and 360 W, respectively), the designed daily vol-ume (17 500 pages per eight hour work day), and repro-duction rate for an average machine that uses the tonerof interest (135 pages per min) were used in calculatingthe energy used in transferring the toner to the paper[20]. It is also important to note that one metric ton oftoner makes 22 million copies, which would take overthree years on an average machine.

Fig. 5. Post-production processes.

3.3.2. End of use processing—toner wasteThe transfer efficiency of xerographic copying is

approximately 90% [5]; toner that remains on the photo-receptor is cleaned from the belt and collected in a wastebin. The toner that is collected in the waste bins of themachines can be recycled back into the toner manufac-turing process. This recycled toner offsets raw materialneeds for toner manufacturing. Currently 66% of thewaste toner available for recovery is being recovered[21]. Waste toner that is not recovered is assumed toenter the local solid waste stream. Other material mayalso accumulate in the toner waste bin, such as paperfibers, staples, and any other material that could beexposed to the photoreceptor. This prevents the directreuse of the waste material in the machine. Before thewaste toner can be reintroduced into the manufacturingprocess, the impurities must be removed using a screen-ing process. Due to the small size of the toner particles,a screen with a very fine mesh separates the largeimpurities (paper pieces, staples, etc.) from the re-usabletoner. Remanufacturing is a low energy process withmuch of the operations done manually. Once the toneris screened, it can be reintroduced into the process fortoner manufacturing. The screening process is assumedto have a mass efficiency of 95%, although this numbercould not be verified.

3.3.3. End of use processing—toner on paperOnce toner is bound to the paper by the fuser rolls,

the fate of the toner and the paper are the same. Paperused by the machines falls under the general categoryof “office paper” , which is one of the highest qualitypapers and a good candidate for recycling. Approxi-mately 43% of office paper consumed is recycled [22].In the recycling of paper, the toner must be removedbefore new products can be made from the recoveredfibers. This process is called “de-inking” and involvesboth chemical and mechanical processing of the paperas it is re-pulped and the ink is dissolved in the washwater. This is energy intensive since the paper must beslurried in a hot water bath to break up the fibers anddissolve the marking material. The product of the dein-king process is pulp, which is used to make recycledpaper. To account for the energy needs to remove thetoner from the paper versus the energy needs to re-pulpthe recycled paper, the energy use for the deinking pro-cess was compared to the energy use in a fiber recoveryprocess. In this process clean scrap paper material fromthe paper making process is repulped for recycle. Thiscomparison showed that 34% more energy is needed inthe deinking process than in the fiber recovery process[23]. Wastewater volumes from the deinking processwere also allocated in this manner. The solid wastereported as resulting from the deinking process, how-ever, was only the toner on the paper that was sent tobe recycled.


The two other destinations for the paper from themachines are indefinite storage (22% of paper produced),where the paper is filed for later use, or the local solidwaste stream (35% of paper produced) [22]. These areboth low energy processes, especially compared to thedeinking process. Solid waste streams usually lead to alandfill, but there are other forms of managing paperwaste, such as incineration or composting. For this reportall of the toner on the paper that enters the solid wastestream is regarded as solid waste.

3.4. Transportation

The movement of materials between processes mustalso be considered as part of the life-cycle. Transpor-tation issues include the movement of raw materialsfrom their source to the manufacturing facility, the distri-bution of the product, and the transportation of allresiduals from the use of the product to their final desti-nation. For the calculation of emissions and energydemands in transportation, energy intensity data [24] andemission factors [25] for freight transported by heavyduty diesel truck were used. For the location of the vari-ous processes, a central geographic region of the UnitedStates was assumed. All organic processing was assumedto take place in the southwest, the resin and magnetitewere manufactured in the midwest, the toner manufac-turing facility is in the northeast, and the remanufactur-ing facility for toner returns is in the southwest. An aver-age distance for the distribution of toner to the customerwas also assumed.

4. Results

Data collected for this report has been split into sevensections: carbon black production, magnetite production,resin production, toner manufacturing, consumer use,end-of-use processing, and transportation. Table 1 showsthe energy needs and emissions for the seven major sec-tions, with subsections included. All of the data has beennormalized to the functional unit. Fig. 6 shows how thedifferent sections of the system compare with oneanother. The dominance of the post-production processes(consumer use and end of use processing) in the emis-sions of the system is readily seen. With the exceptionof VOC emissions and fossil fuel use, post-productionprocessing resulted in greater than 85% of the total valueof all categories. The percent contributions from the sec-tions in Fig. 6 also shows a link between air emissionsand energy use, which results from the much largerquantities of energy related air emissions in relation tomanufacturing process air emissions.

Customer use is the most energy intensive process ofthe system. The energy required to transfer the metricton of toner onto paper (corresponding to 22 million cop-

ies at 135 images per minute [26]) consumes 57% of thetotal energy used during the life-cycle of toner. End-of-use processing also has a significant impact, due mainlyto the removal of toner from paper that is recycled. De-inking requires large amounts of electrical energy toremove the toner via mechanical and chemical methods.It also results in large effluent flows, accounting for 98%of the total wastewater for the system. The solid wasteshown is the quantity of toner that is removed in the de-inking process. The process also results in a large quan-tity of sludge waste (mostly paper waste, which is notincluded) that would also enter the solid waste manage-ment system.

The industrial concerns with the toner manufacturingprocess were shown to be a relatively small contributorto solid waste, air emissions, and energy use over thelife-cycle. Without the recycling initiatives recentlyimplemented at the manufacturing site, however, theproduction of solid waste from the life-cycle would havebeen much larger, as shown in Table 2. The recyclingstreams within the life-cycle are a key factor in reducingboth the amount of waste produced, and the amount ofraw materials introduced in the process. In regards tothe energy use in the toner manufacturing process, thegrinding step had the highest energy usage (approx. 80–90% of the total).

The mass flows into and out of the system are alsofactors in the life-cycle assessment of toner. The materialrequirements for production in the system and the by-products produced by the system are listed in Table 3.The inputs into the system are mainly products from pet-roleum and natural gas refineries. A few very smallinputs are not listed, such as specialty chemicals in resinmanufacturing. In addition, water and air use are notlisted as inputs. By-products are products that are usedin other sectors of industry. Some of the by-products canbe reused directly by the system, such as burning theresidual fuel for heating.

5. Discussion

The overall mass balance of the system shows thatmaterial enters mainly as virgin raw materials and leavesmostly as non-usable waste. The exit points for the wasteare principally through solid waste, such as fines froma dryer. The largest source of waste, as with most “cradleto grave” processes, is the solid waste resulting from theend-of-use processing. The recycle stream from the tonerwaste generated by the customer to the toner manufac-turing process and the in-plant recycling of toner finesdo show the beginning of a move to closed-loop pro-duction, but the system is still far from the desired“cradle to cradle” scenario. A true closed-loop processwould occur when all of the toner is recoverable fromthe paper using low energy methods that would leaveboth the toner and the paper in a usable form.


Table 1Energy use and emissions data for the system processes (per mton of toner). a

Energy Fossil Electricity CO2 NOx SO2 VOCs Particulates Wastewater SolidUse Fuel waste

Units 106 kJ 106 kJ 106 kJ 103 kg kg kg kg kg m3 kg

Carbon black production 1.5 1.5 min 0.06 0.12 1.1 0.10 0.07 min min

Magnetite production 2.9 1.6 1.4 0.17 0.59 0.7 0.08 0.56 1.5 minNaOH 1.2 0.1 1.1 0.08 0.33 0.6 0.06 0.23 min minMagnetite 1.7 1.4 0.3 0.09 0.26 0.1 0.02 0.34 1.5 min

Resin production 4.7 4.0 0.7 0.25 0.71 0.4 22.1 0.17 1.0 14Ethylene 1.4 1.4 min 0.07 0.18 0.0 1.2 min min minEthylbenzene 0.7 0.66 min 0.03 0.09 0.0 7.2 min min minStyrene 1.8 1.8 min 0.10 0.24 0.0 6.5 min min minButadiene 0.1 min 0.1 0.01 0.02 0.0 0.61 0.02 min minResin 0.7 0.11 0.6 0.04 0.19 0.3 6.6 0.15 1.0 14

Toner manufacturing 22 min 22 1.4 6.2 12 1.3 4.9 min 23Consumer use 150 min 150 9.5 43 82 8.7 31 min 34

End of use processing 72 6.5 65 4.4 20 35 3.8 13 140 710Toner Recycle min min min min min min min min min 9.2De-inking of Paper 72 6.5 65 4.4 20 35 3.8 13 140 390Toner on Paper to Landfill min min min min min min min min min 320

Transportation 7.6 7.6 min 0.60 2.3 0.1 0.68 0.33 min minRaw Materials to Toner 3.4 3.4 min 0.27 1.0 0.0 0.31 0.15 min minManufacturer.Toner to Customer 2.6 2.6 min 0.19 0.73 0.0 0.22 0.11 min minToner Waste Recycle 1.6 1.6 min 0.13 0.49 0.0 0.15 0.07 min min

Total 260 21 240 16 73 130 37 51 140 780

a min=minimal to zero use or release

Fig. 6. Energy use and emissions as a percentage of the total for the system processes.


Table 2Life-cycle improvements associated with recycling toner waste

Waste/Material Without With recyling Percentrecyling (kg/mton) reduction

(kg/mton)

Solid waste 1020 780 24%produced in thelife-cycleVirgin materials 2530 1790 29%used in toner life-cycle

Table 3Material requirements and by-products of the system

Material Inputs and Sources Quantity By-product Quantity(kg/mton) (kg/mton)

Ethane from natural gas 240 Light organic 51products

Benzene from refinery 530 Residual organics 95used as fuel

NaCl from rock salt 340 Benzene/Toluene 47mixed stream

FeSO4∗7H2O from TiO2 510 Chlorine gas 210productionCarbon black feedstock 44 Hydrogen gas 5.8from refineryC4 fraction from steam 120 Butanes and C5 36cracking of ethane fractionOther toner fines from 117 Na2SO4 salt 260recovery facilityTotal inputs 1900 Total by-products 700

The results of this study show that the consumer usestage in the life-cycle of toner particles has the highestenergy use, thereby generating significant air emissions.This suggests that efforts to reduce energy consumptionin the photocopier should be the focus of continualefforts to improve xerography. A small percent reductionin emissions from customer use would have a muchlarger effect on the system than a similar, or sometimesmuch larger, percent reduction in any other stage ofthe system.

The deinking process associated with the recycling ofpaper also impacts emission levels. While this result mayappear to suggest that recycling paper is a less desirableoption than landfilling the paper waste, this is only truewith respect to the toner on the paper. Focusing on theenergy requirements over the life-cycle of office paper,the use of virgin material in the production process anddisposal of the resulting paper waste in a landfill requires84% more energy than that needed to produce 100%recycled paper [27].

The manufacturing and sale of toner is highly com-petitive. This study was performed not only to evaluate

the environmental emissions resulting from toner overits life-cycle, but also to suggest improvements thatcould be made within the life-cycle and aid in thedecision of using alternative toner manufacturing tech-nologies. As described previously, the conventional pro-cess conceptually involves creating large particles andbreaking them down mechanically to the desired particlesize range. An alternative to this process, currently indevelopment, is a chemical toner process in which nano-meter-sized particles are grown to the desired particlesize range [28]. A comparison of LCAs of both pro-cesses should be a factor in determining which processthe industry and society would desire. For example whilethe current manufacturing process has high energy use,particularly in the grinding step, chemical toner manu-facturing results in significantly increased water usage.To perform a comparative LCA, the boundaries of thetwo systems must be drawn to include identical stagesin the life cycle. The functional unit must also be chosensuch that a valid comparison can be made. If the newtoner increases the transfer efficiency of toner to paper,a more appropriate functional unit for such a comparisonwould be the toner required to produce a specified num-ber of documents. A comparison of the energy andmaterial needs for the two processes would show theenvironmental costs or savings associated with thenew technology.

The goal of developing a closed-loop system for toneris difficult to achieve, and in the search for sustainablemethods of document storage, the use of toner on paperas a storage medium may not survive. As the digital agecontinues to unfold, new reliable and efficient methodsof document storage and retrieval are evolving. Com-puters and the internet are allowing large volumes ofinformation to be stored, searched, copied, and sharedin a fraction of the time and effort of past methods; how-ever, it is not clear that this new technology is better forthe environment, or is consistent with a sustainablefuture. It is important to remember that manufacturingcomputers and the associated storage media results in asignificant amount of waste that must be compared tothe wastes associated with producing a hard-copy docu-ment. A comparative LCA between storing documentsas hard copies on paper and as digital files on a computerwould highlight the environmental performance of thetwo processes. The issue of sustainability would beaddressed, in part, via the overall mass flows and energydemands in the life-cycles. The usability of the residualsfrom the two systems would also be a factor in the sus-tainability issue. In the final analysis, the comparativelife-cycle assessment of the two systems would be anaid in determining which technology would be optimalfor the management of documents.


Acknowledgements

We gratefully acknowledge personnel from the XeroxCorporation, Webster, NY, specifically Jack Azar, V.P.,Environmental Health and Safety; and Michael Walker,former V.P., Multinational Supplies ManufacturingOperations; also Paul Acquaviva, Frank Di Bisceglie,Tom Peer, Tom Piccirilli, Monica Skerker, Joe Stulb,Mit Turakhia, and George Vianco. Michael Le from theXerox Corporation, Oklahoma City, OK; and Tim Cabotfrom the Cabot Corporation also provided data and infor-mation for this paper. We also acknowledge the supportof the National Science Foundation for the Environmen-tal Manufacturing Management program at ClarksonUniversity, grant DGE 9870646 of the IntegrativeGraduate Education Research and Training (IGERT)program, Wyn Jennings and Larry Goldberg programdirectors.

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Life-cycle inventory of toner produced for xerographic processes

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