It takes about three minutes to order a final dissertation for an English literature degree at the UK Essays website. I pick my country, subject and required grade. I go for a 2:1, choose a length – let’s say 5,000 words – a seven-day deadline, and watch the price calculator hit £687 (or £1,236 for a two-day turnaround). Click “next step” and I can enter my topic before being matched with a suitable writer, who will produce an essay “personalised to my requirements”. It would come with a series of promises. “The work we produce is guaranteed to meet the grade you order, or you get your money back.” It will also be “100% free from plagiarism” – and on time.
All of this would be totally legal and, the owners of UK Essays insist, ethical, too – because what its customers are definitely not supposed to do is submit the work as their own. “Our essays … are the best, most useful study aid in the world,” says Daniel Dennehy, chief operating officer at All Answers, the Nottinghamshire company that owns UK Essays. “They increase any student’s understanding of a topic, which subsequently improves their ability to write an excellent, unique answer of their own.”
UK Essays says it sold 16,000 assignments last year, up from 10,000 five years earlier, written by a network of 3,500 researchers. The company’s “fair use policy”, which requires a click away from the order page, spells out the rules. “Even if you did make minor alterations to the researcher’s work, this would still be considered plagiarism,” it warns. But, Dennehy accepts, “I have worked here for nine years and I am not naive enough to think that all our clients use the work correctly.” He declines to estimate what proportion of his customers are cheats.
The growth of these sites, which are known as essay mills, is now troubling the higher levels of government. Jo Johnson, the universities minister, has appealed to student bodies and universities to help tackle so-called “contract plagiarism”, which he sees as a growing threat to academic integrity. New guidelines, to be published in time for the next academic year, are expected to recommend a new sector-wide policy, and the government has not ruled out beefing up the law.
The intervention follows a report published last summer by the Quality Assurance Agency (QAA), which maintains standards in higher education. It found that anti-plagiarism policies were variable across universities, and that fraud law isn’t robust enough to legislate against the misuse of essay mills. It also suggested a ban on advertising, and explored the role of search engines, which present hundreds of results to students looking for essays.
The government believes there are more than 100 mills in operation, churning out anything from B-grade GCSE coursework (£106 on UK Essays) to a 100,000-word PhD in criminal law (£82,238). “But our research suggests it’s more like 1,000 sites,” says Prof Phil Newton, the director of learning and teaching at Swansea University and an expert in academic plagiarism. Previous estimates suggest that more than 20,000 students a year in the UK are paying for essays to get degrees. The true figure may be much higher.
“This is a very fast-moving problem, which the sector and legislation has been slow to address,” Newton adds. “When I started researching it in 2009, I couldn’t believe what was available and how little research had been done. On some sites you can even enter your course code and the name of your lecturer and the writer will tailor an essay to that. To the man on the street,” he adds, “it’s very odd that this sort of thing is legal.”
Universities are equipped to detect old-fashioned, cut-and-paste plagiarism. Software such as Turnitin, which claims 97% of UK universities as customers, flags up passages it identifies in existing sources. But it cannot detect an original essay written by someone else. Even when lecturers suspect foul play, it can be hard to know how to act. “I had one instance recently when a student received a much higher mark than expected,” says a senior lecturer at a London university, who asked not to be named. “His work had a level of fluency and sophistication of thought that hadn’t been seen. But I wasn’t 100% sure, because I think he wrote parts of the essay in his own style to throw me off, so I left it. It’s a minefield.”
Opinion is divided over how to respond, however, and whether tighter rules or laws risk driving would-be cheats to the darker edges of the “model answers industry”, as essay mills prefer to be called. Many students have reported being ripped off with shoddy work, or none at all. But there is also concern that contract plagiarism, while obviously wrong, is a symptom of what critics describe as the commodification of higher education.
International students in the UK now pay between around £15,000 and £40,000 a year in tuition fees. Those from outside the EU paid £4.2bn in fees in 2014-15, almost 30% of universities’ income from fees – and almost 13% of their total income.
Universities depend on foreign students with deep pockets, which is why they are fighting government plans to bring numbers down. Dave Tomar, a former mill writer in the US, says this means universities too often sell places to ill-equipped students, many of whom arrive with limited written English or awareness of British academic norms. “The vast majority of students who cheat aren’t lazy, but struggling,” he says. “They have invested so much that they don’t want to blow it by failing.”
In 10 years, Tomar, 37, says he wrote about 4,000 assignments for customers, including hundreds in Britain. Before he quit in 2013, he says he earned $60,000 (almost £50,000) a year; he says writers generally get about half the essay fee. “Whatever their motivations, this is a symptom, not the illness,” he adds from his home in Philadelphia, where he now writes about education reform after the success of The Shadow Scholar, a book about his former life. “We need a broader conversation about how educational systems are failing these students such that they end up in college way over their heads.”
Now a degree is a commodity, no wonder more students are cheating | Poppy Noor
While studying a language at Cambridge University, Claire (not her real name) wrote essays during her first year, and also understood that most of her customers were not British. “You have a UK system reliant on foreign students while, through the backdoor, companies are devaluing the very degree certificates that attract all that foreign money in the first place,” she says in an email, describing the result as “a wonderful downward spiral of devaluation”.
Newton accepts that, in some places, students arrive without sufficient skills to complete good written work. But he says students know when they are crossing a line, and that penalties for plagiarism are generally tough already (cheats at Swansea are expelled). What has changed, he adds, is the increasing accessibility and slick presentation of many of the sites, which appeal to students who might not otherwise resort to cheating. “The easier it is, the more likely it is to happen,” he says.
Not all essay mills, which began to proliferate over a decade ago, do much to put off would-be cheats. OK Essay, which last year removed adverts from London Underground stations near universities after complaints, claims on its homepage to have more than 10,000 customers. “Looking for experts to ‘Write my essay for me’? Choose us and we won’t disappoint you!” Deep in the terms and conditions, the mill says it will not be liable “for the outcome or consequences of submission [of] the paper to any academic institution”. Nowhere does it explicitly advise against it.
Posing as a struggling history student, I call the customer support line for clarification. “If I want to use the essay as my own work, is that possible?” I ask. “I’m not able to tell you whether it’s possible or not. We just write the paper for you and you can use it for what you want,” the agent says. The company says it is based in Sheffield, but there is no address on the website, which also hides its domain registration details. The terms and conditions say the site is owned by Elabama Inc, a company registered in Panama. “So it would be at my own risk?” I ask. “You can just use it at your own risk – it’s what our disclaimer says on our website. It’s meant to serve as example … You can get it, read it, shake it and if you like it you can use it, if you don’t like it you can fix it to [be] like you want it and use it.” When I call back as a journalist, I am given an email address but none of my questions are answered, and despite further calls and emails, there is no response to the suggestion that the company appears to condone cheating.
Claire wrote for Oxbridge Essays, a prominent site with offices in London. “It was clear to everyone involved what was going on,” she recalls. Yet she found the work stimulating as well as lucrative after quitting a “soul-destroying” temp job. “I didn’t worry too much about the ethics at first because I felt bitter about the fact this was the only way I could find work that was interesting and rewarding,” she says. “I got paid £200 for the first one. I was 19 and that was a lot of money.”
In 2013, the Advertising Standards Authority ruled that Oxbridge Essays had breached its code by guaranteeing “that you will receive at least the grade you order”. The implication of the promise contradicted the company’s terms, which prohibit the submission of its essays, the authority found. Philip Malamatinas, who launched the site in 2006, declines to answer questions. Nor does he respond to Claire’s claim that the company knew what was going on. “We work with thousands of students who come to us having been let down by a system designed to penalise those for whom English is a second language, and who typically pay three or four times as much as UK students in tuition fees,” he writes in a statement. “Sadly, our universities are simply too stretched to provide the same level of support to all and as a result, students are turning to private enterprises to subsidise their educational needs.”
Mills are not the only people making a case for model answers. “I think they’re incredibly valuable, especially for international students,” says Alexander Proudfoot, chief executive of Independent Higher Education (formerly Study UK), which represents more than 130 private institutions. He attended a QAA plagiarism forum before the publication of last year’s report. “We’d be happy for there to be a national database of essays. If you made them accessible then the demand for essay mills goes out the window [see footnote].”
Universities blame others for plagiarism. They need to look at themselves
Newton, who also sat on the forum, is not convinced, preferring “to show students how things are structured and what it looks like to write an essay”. Either way, he adds: “When you can give a precise title and specify the grade and the referencing and sources, that’s something very different.” No essay site I approach will explain why, if their work is only intended to be used as a model, they are so keen to guarantee originality, sometimes two days before a deadline, if not to help students elude plagiarism detection software.
Newton believes part of the solution must be a requirement for more face-to-face and practical assessment. Proudfoot says institutions should find resources for essay-writing and critical-thinking classes, as well as tutorial support for students who “find themselves backed into a corner”. Claire agrees. She gave up when the demands of her own studies left her too busy to write for other students. “My dad also told me, ‘You might not be thinking about the wider repercussions of this now, but think about later,’ and I thought – you know, you might be right.”
• The following footnote was added on 6 March 2017: after publication, Alexander Proudfoot asked us to clarify that when he said “the demand for essay mills goes out the window”, he meant “the argument for essay mills goes out the window”.
TABLE OF CONTENT
LIST OF TABLES
1.2 Statement of the Problem
2 LITERATUR/ READING
3 Pulp and Paper Manufacturing Processes
3.2.1 Chemical pulping
3.2.2 Mechanical pulping
3.4 Paper Production
4.Environmental Impact Analysis
4.2 General Organic Pollution and Suspended Solids
4.3 Acidic Compounds
4.4 Environmental Impact of Chlorine Compounds
4.5 General Organochlorine Products
4.5.2 Dioxins (PCDD) and Furans (P CDF)
4.5.3 Chloroform and Other Neutral Chlorinated Compounds
4.6 Other Environmental Issues Relating to Effluent Discharge
4.7 Impact on Forest
4.8 Impact on Biodiversity
4.9 Impact on the Atmosphere
4.10 Impact onPoly Culture
4.11 Impact on water
5.1 Alternative processes of pulp and paper production
5.2 Recycled Fiber
5.3.1 Mechanical pulping
5.4 Environmental impacts of the recycling process
5.4.1 Wastewater Emissions
5.4.2 Air Emissions
5.4.3 Solid Waste
5.4.4 Energy use
5.4.5 Water Use
5.4.6 Life Cycle Analyses
5.5 NonWood Fiber Sources
5.6 NonWood Fiber Types
5.7 Environmental Impacts of NonWood Fiber Pulp and Paper
5.7.1 Crop Production
5.8 The Manufacture Process
The complexity of the paper issue means that firm conclusions are hard to draw. All paper manufactures causes harm to the environment and more often than not the determining factors in a paper mills. Environmental performance is not the process, paper type or fiber source but the location, mill practice and mill operator. Hence to try to grade paper products or production techniques into some kind of hierarchy of environmental performance, based solely on the manufacture process, is extremely difficult. Yet, globally however, the environmental impact of paper is significant, which has led to changes in industry and behavior at both business and personal levels. With the use of modern technology such as the printing press and the highly mechanized harvesting of wood, paper has become a cheap commodity everywhere. This has led to a high level of consumption and waste. With the rise in environmental awareness on the pollution of the eco system by the effluent of pulp and paper it became imperative to run a clearer analysis of its environmental impact.
LIST OF TABLES
TABLE 1: Summary of Pulping Characteristics
TABLE 2: Paper Production by Product Category
TABLE 3: Air Emissions from the Pulp and Paper Industry
TABLE 4: Waste Paper Categories
LIST OF PLATES
PLATE 1: Pulp and Paper Cycle
PLATE 2: Paper Making Process
PLATE 3: Environmentally Product Logos
Globally, the environmental impact of paper is significant, which has led to changes in industry and behavior at both business and personal levels. With the use of modern technology such as the printing press and the highly mechanized harvesting of wood, paper has become a cheap commodity everywhere. This has led to a high level of consumption and waste. With the rise in environmental awareness on the pollution of the eco system by the effluent of pulp and paper it became imperative to run a clearer analysis of its environmental impact. The campaigns by environmental organizations has may have yielded a little effort with the increased government regulation in this regard, there is now a trend towards sustainability in the pulp and paper industry ( IIED1996). This environmental anomaly has necessitated the writing of this article, Environmental Impact Analysis of Pulp and Paper Production.
1.2 STATEMENT OF THE PROBLEM
Historically pulp and paper production has ranked among the most resourceintensive and highly polluting of all manufacturing industries. Besides fiber, the primary inputs into the paper making process are water, energy and chemicals. In the United States, the paper industry is the largest user per tonne of product of industrial process water (U.S. EPA 2002) and the third largest industrial consumer of energy (U.S. DOE). Also, papermaking is a very chemically intensive process. The pulp and paper industry ranks fourth among industrial sectors in emissions of Toxics Release Inventory (TRI) chemicals to water, and third in such releases to air. Paper’s impact on the environment continues even after it has been thrown away. As at early 2008 in the United States, paper and paperboard accounted for the largest portion (34 percent) of the municipal waste stream, and 25 percent of discards after recovery of materials for recycling and composting. The problem with all this paper being thrown away is not just about landfill space. Once in a landfill, paper has the potential to decompose and produce methane, a greenhouse gas with 21 times the heattrapping power of carbon dioxide (UNEP). Finally, transportation throughout the system also has significant environmental impacts. Harvested trees or recovered paper are transported to pulp mills, rolls of paper are transported to converters, and finished paper products are transported to wholesale distributors and then on to their retail point of sale. Transportation at each of these stages consumes energy and results in greenhouse gas emissions ( Kerski 1995).
PLATE 1: PULP AND PAPER CYCLE
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The aim of this piece of work is to analyze the environmental impact of pulp and paper production, and gain understanding in the production processes. Sequel to this, the following objective will be employed to achieve this aim.
1 To identify the process of paper production
2 To identify the environmental impacts of pulp and paper production
3 To identify the possible alternatives and solutions that exist.
4 To identify the products and processes that is the most environmentally acceptable.
2.1 LITERATURE / READING
The work of Martin (2004) on environmental impact of pulp and paper will be capture in this piece of work. He opined that, worldwide consumption of paper has risen by 400% in the past 40 years, with 35% of harvested trees being used for paper manufacture. Logging of old growth forests accounts for less than 10% of wood pulp, but is one of the most controversial issues. Plantation forest, from where the majority of wood for pulping is obtained, is generally a monoculture and this raises concerns over the ecological effects of the practice. Deforestation is often seen as a problem in developing countries but also occurs in the developed world. Wood chipping to produce paper pulp is a contentious environmental issue in Australia. In the 1990s, the New Zealand government stopped the export of woodchips from native forests after campaigning by environmentalists. In his work, he stressed nitrogen dioxide (NO2) sulfur dioxide (SO2) and carbon dioxide (CO2) are all emitted during paper manufacturing. Nitrogen dioxide and sulfur dioxide are major contributors of acid rain, whereas CO2 is a greenhouse gas responsible for climate change.
He asserted that waste water discharges for a pulp and paper mill contains solids, nutrients and dissolved organic matter, and unless at low levels these are classed as pollutants. Nutrients such as nitrogen and phosphorus can cause or exacerbate eutrophication of fresh water bodies such as lakes and rivers. Organic matter dissolved in fresh water, measured by Biological Oxygen Demand (BOD), changes ecological characteristics, and in worse case scenarios leads to death of all higher living organisms. Waste water may also be polluted with organochlorine compounds. Some of these are naturally occurring in the wood, but chlorine bleaching of the pulp produces far larger amounts. Paper waste accounts for up to 40% of total waste in the United States, which adds up to 71.6 million tons of waste per year in the United States alone. Paper waste like other wastes faces the additional hazard of toxic inks, dyes and polymers that could be potentially carcinogenic when incinerated, or comingled with groundwater via traditional burial methods such as modern landfills. Paper recycling mitigates this impact, but not the environmental and economic impact of the energy consumed by manufacturing, transporting and burying and or reprocessing paper products. Bleaching mechanical pulp is not a major cause for environmental concern since most of the organic material is retained in the pulp, and the chemicals used (hydrogen peroxide and sodium dithionite) produce benign byproducts (water and sodium sulfate (finally), respectively).
However he analyzed the bleaching of chemical pulps and concludes that it has the potential to cause significant environmental damage, primarily through the release of organic materials into waterways. Pulp mills are almost always located near large bodies of water because they require substantial quantities of water for their processes. An increased public awareness of environmental issues from the 1970s and 1980s, as evidenced by the formation of organizations like Greenpeace, influenced the pulping industry and governments to address the release of these materials into the environment. Environmental NGO pressure was especially intense on Swedish and Finnish pulp and paper companies. Conventional bleaching using elemental chlorine produces and releases into the environment large amounts of chlorinated organic compounds, including chlorinated dioxins. Dioxins are recognized as a persistent environmental pollutant, regulated internationally by the Stockholm Convention on Persistent Organic Pollutants. Dioxins are highly toxic, and health effects on humans include reproductive, developmental, immune and hormonal problems. They are known to be carcinogenic. Over 90% of human exposure is through food, primarily meat, dairy, fish and shellfish, as dioxins accumulate in the food chain in the fatty tissue of animals. As a result, from the 1990 onwards the use of elemental chlorine in the delignification process was substantially reduced and replaced with ECF (Elemental Chlorine Free) and TCF (Totally Chlorine Free) bleaching processes. In 2005, elemental chlorine was used in 19–20% of kraft pulp production globally, down from over 90% in 1990. 75% of kraft pulp used ECF, with the remaining 5–6% using TCF. Most TCF pulp is produced in Sweden and Finland for sale in Germany, all markets with a high level of environmental awareness. In 1999, TCF pulp represented 25% of the European market. TCF bleaching, by removing chlorine from the process, reduces chlorinated organic compounds to background levels in pulp mill effluent. ECF bleaching can substantially reduce but not fully eliminate chlorinated organic compounds, including dioxins, from effluent. While modern ECF plants can achieve chlorinated organic compounds (AOX) emissions of less than 0.05 kg per tonne of pulp produced, most do not achieve this level of emissions. Within the EU, the average chlorinated organic compound emissions for ECF plants is 0.15 kg per tonne. However, there has been disagreement about the comparative environmental effects of ECF and TCF bleaching. On the one hand, paper and chemical industryfunded studies have generally found that there is no environmental difference between ECF and TCF effluents. On the other hand, independent peerreviewed study has found that, comparing conventional, ECF and TCF effluents before and after secondary treatment, “TCF effluents are the least toxic”.
He opined that some of the effect of the pulp and paper industry can be addressed and there is some change towards sustainable practices. The use of wood solely from plantation forests address concerns about loss of old growth forests. The move to nonelemental chlorine for the bleaching process reduced the emission of the carcinogenic organochlorines. Peracetic acid, ozone and hydrogen peroxide and oxygen are used in bleaching sequences in the pulp industry to produce totally chlorine free (TCF) paper. There are three categories of paper that can be used as feed stocks for making recycled paper: mill broke, preconsumer waste, and postconsumer waste. Mill broke is paper trimmings and other paper scrap from the manufacture of paper, and is recycled internally in a paper mill. Preconsumer waste is material that was discarded before it was ready for consumer use. Postconsumer waste is material discarded after consumer use such as old magazines, old telephone directories, and residential mixed paper. One concern about recycling wood pulp paper is that the fibers are degraded with each and after being recycled four or five times the fibers become too short and weak to be useful in making paper. The United States Environmental Protection Agency has found that recycling causes 35% less water pollution and 74% less air pollution than making virgin paper. Pulp mills can be sources of both air and water pollution, especially if they are producing bleached pulp. Modern mills produce considerably less pollution than those of a few decades ago. Recycling paper decreases the demand for virgin pulp and thus reduces the overall amount of air and water pollution associated with paper manufacture. Recycled pulp can be bleached with the same chemicals used to bleach virgin pulp, but hydrogen peroxide and sodium hydrosulfite are the most common bleaching agents. Recycled pulp, or paper made from it, is known as PCF (process chlorine free) if no chlorinecontaining compounds were used in the recycling process. Three main issues with the environmental impact of printing inks is the use of volatile organic compounds, heavy metals and nonrenewable oils. Standards for the amount of heavy metals in ink have been set by some regulatory bodies. There is a trend toward using vegetable oils rather than petroleum oils in recent years due to a demand for better sustainability. However Martin (2004) fail to chronicle the processes involve in the production of pulp and paper which will be chronicled in this term paper.
3.PULP AND PAPER MANUFACTURING PROCESS
Processes and procedure of making paper is long and tedious, the modus operandi is out lined below.
According to Costello and Link (1989), pulp and paper mills are integrated with all production stages taking place on the same site. However, most mills in the UK produce paper only, relying on imported pulp. The primary raw material in paper manufacture is cellulose fibre. Wood consists of approximately 50 per cent cellulose, 30 per cent lignin (a resinous adhesive which holds the fibres together), and 20 per cent aromatic hydrocarbons and hemicellulose carbohydrates. In order to obtain cellulose in usable form for paper manufacture the wood or plant material must be pulped to separate the fibres and remove impurities. The higher the cellulose content of the pulp, and the longer the fibres, the better quality the paper. Hardwoods generally contain a higher proportion of cellulose but of shorter fibre length than softwoods, which are more resinous.
Outlined below are the principal pulping processes.
3.21 CHEMICAL PULPING
i. Sulphate (Kraft)
Kraft or sulphate pulping is the dominant method of pulp production in the world by virtue of its versatility and the high strength, long fibre, very low lignin content pulp it produces. There are no Kraft mills in the UK and so all Kraft pulp used by UK paper and board manufacturers (1,399,000 tons in 1995) is imported. In fact, the Kraft process was prohibited in several densely populated areas due to the sulphurous smell associated with the mills. Softwood chips are the principal wood source, although the process can be adapted to any tree species.
The process involves boiling wood chips in a sodium hydroxide (caustic soda) and sodium liquor. This separates the lignin and wood resins from the cellulose fibre pulp, which is then washed and, if necessary, bleached. The majority of Kraft mills operate a closed loop system whereby 95 per cent 98 per cent of the chemicals used in the process are recovered and reused. This means that, in comparison with other processes, small amounts of chemicals are needed to produce large amounts of pulp: about 20kg of sodium sulphate and 75kg of calcium carbonate are required per ton of pulp.The waste products from the process are generally burned to provide energy.
Each ton of wood chips used yields about 0.5 tons of pulp (compared to 0.9 0.95 tons for mechanical pulp). Another major disadvantage of Kraft pulp is that, due to its dark colour, it requires strong bleaching agents if it is destined to become white paper.
Sulphite pulping uses similar equipment to Kraft but involves a different chemical process. The resulting pulp is characteristically strong, soft and lighter in colour than Kraft pulp, thus requiring less bleaching. Again there are no sulphite mills in the UK, so all sulphite pulp has to be imported (108,000 tons in 1995), its major end use being tissue products.
Sulphuric acid or hydrogen sulphite is used to 'cook' the raw material in a liquor with a reactive metal base (usually calcium, magnesium or sodium) or ammonium to produce an acid sulphite or bisulphite pulp. Whilst closed loop systems can be applied to sulphite processes, they are dependent on the base metal used. In general terms chemical recovery rates for sulphite pulping are not as high as for Kraft although in terms of energy use sulphite has the slight edge with roughly equivalent pulp yields. Water consumption for both chemical pulping methods is high.
3.22 MECHANICAL PULPING
i. Groundwood Pulping
This is the most basic form of pulping and simply involves the grinding of debarked logs or chips to separate the fibres. There are currently two mechanical pulp mills operating in the UK, producing 548,000 tons of pulp in 1995. The quality of the pulp is low as the fibres produced are broken by the grinding and still surrounded by lignin. This means the paper products produced are weak and turn yellow more quickly. As a consequence, mechanical pulp is largely used for newsprint and paper products which require little tear strength. Whilst the pulp yield per ton of wood is much higher than chemical pulping (around 0.95 tons) the amount of imported energy required is approximately double that required by the chemical process. Water consumption, however, is roughly one third of the amount required by chemical pulp mills.
ii. Thermomechanical pulping (TMP)/Chemo Thermomechanical Pulping (CTMP)
Two variations of the mechanical process are widely used in the pulp industry with the aim of reducing energy consumption by presoftening the wood chips. In thermomechanical pulping, which is used on softwoods only, the chips are steamed prior to grinding. In the chemo thermomechanical process the wood chips are first impregnated with sulphurbased chemicals which extract some resin and lignin from the fibre prior to steam softening. Both these modifications results in a stronger pulp which can be applied to higher quality end uses.
TABLE 1: SUMMARY OF PULPING CHARACTERISTICS
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Note: Figures are approximate; where necessary they have been converted from different units.
The bleaching part of the pulp and paper manufacture process has so far proved to be the most controversial in environmental terms. The process is dependent on the type of pulp involved and the destined end use.
a Hydrogen peroxide brightening
Mechanical pulp, being high in lignin content, is usually 'brightened' using hydrogen peroxide. This alters the chemical structure of the lignin, lightening its colour but leaving it present in the pulp. Lignin removing chemicals such as chlorine are not used because this would result in a large reduction in yield. Hydrogen peroxide is environmentally benign but the process does require quite high levels of energy and is relatively expensive. Other chemicals used to produce brighter mechanical pulps include hypochlorites and sodium bisulphite. It should be noted that approximately half the mechanical pulp produced is used for products which do not require brightening.
b Chlorine bleaching
Chemical pulp is routinely delignified to remove the 5 per cent 10 per cent of lignin remaining after the pulping process. Traditionally chlorine gas has been used for this, followed by several stages of treatment with chlorine dioxide or hyperchlorite to further whiten the pulp.50 to 80 kilograms of elemental chlorine are required to bleach one tonne of pulp. Approximately 10 per cent of this chlorine will combine with organic molecules to form a range of organochlorines in the process effluent. Most notorious amongst these are dioxins and furans.