Paper pollution
Encyclopedia
The production and use of paper
has a number of adverse effects on the environment
which are known collectively as paper pollution. Pulp mill
s contribute to air
, water
and land pollution. Discarded paper is a major component of many landfill
sites, accounting for about 35 percent by weight of municipal solid waste (before recycling). Even paper recycling
can be a source of pollution due to the sludge produced during deinking.
According to a Canadian citizens organization, "People need paper products and we need sustainable, environmentally safe production." The amount of paper and paper products is enormous, so the environmental impact is also very significant. It has been estimated that by 2020 paper mills will produce almost 500,000,000 tons of paper and paperboard per year, so great efforts are needed to ensure that the environment is protected during the production, use and recycling/disposal of this enormous volume of material.
Pulp and paper is the third largest industrial polluter to air, water, and land in both Canada and the United States, and releases well over 100 million kg of toxic pollution each year.
Worldwide, the pulp and paper industry is the fifth largest consumer of energy, accounting for four percent of all the world's energy use. The pulp and paper industry uses more water to produce a ton of product than any other industry.
and compounds of chlorine are used in the bleaching of wood pulp
, especially chemical pulps produced by the kraft process
or sulfite process
. Plants using elemental chlorine produced significant quantities of dioxins. Dioxins are persistent organic pollutants that are generally recognized among the most toxic human-released pollutants in existence. Elemental chlorine has largely been replaced by chlorine dioxide
and dioxin production very significantly reduced. The promise of complete removal of chlorine chemistry from bleaching processes to give a TCF (totally chlorine-free) process, which peaked in the mid-1990s, did not become reality. The economic disadvantages of TCF (according to a chemical industry association), the lack of stricter government regulation and consumer demand meant that as of 2005 only 5 to 6 percent of kraft pulp was bleached without chlorine chemicals. A study based on U.S. Environmental Protection Agency (EPA) data concluded that "Studies of effluents from mills that use oxygen delignification and extended delignification to produce ECF (elemental chlorine free) and TCF pulps suggest that the environmental effects of these processes are low and similar."
The used process water from a pulp mill contains a lot of organic material such as lignin
and other organic material from the trees (including chlorinated organic material) resulting in high biological oxygen demand
(BOD) and dissolved organic carbon (DOC). It also contains alcohol
s, and chelating
agents and inorganic materials like chlorate
s and transition metal
compounds. Recycling the effluent (see black liquor
) and burning it, using bioremediation
ponds and employing less damaging agents in the pulping and bleaching processes can help reduce water pollution.
-based compounds are used in both the kraft process
and the sulfite process
for making wood pulp. Sulfur is generally recovered, with the exception of ammonia-based sulfite processes, but some is released as sulfur dioxide during combustion of black liquor
, a byproduct of the kraft process, or "red liquor" from the sulfite process. Sulfur dioxide
is of particular concern because it is water soluble and is a major cause of acid rain
. In 2006 the pulp and paper industry in Canada released about 60,000 tonnes of sulfur oxides (SOx) into the atmosphere, accounting for just over 4% of the total SOx emission from all Canadian industries.
A modern kraft pulp mill is more than self-sufficient in its electrical generation and normally will provide a net flow of energy to the local electrical grid. Additionally, bark and wood residues are often burned in a separate power boiler to generate steam. If the harvested trees are replanted a kraft mill can be carbon-neutral, but reforestation
has been criticized for reducing biodiversity
.
Air emissions of hydrogen sulfide
, methyl mercaptan, dimethyl sulfide
, dimethyl disulfide
, and other volatile sulfur compounds are the cause of the odor characteristic of pulp mills utilizing the kraft process.
Other chemicals that are released into the air and water from most paper mills include the following:
produced primarily by grinding wood is known as "mechanical pulp" and is used mainly for newsprint
. These mechanical processes use fewer chemicals than either kraft or sulfite mills. The primary source of pollution from these mills is organic material such as resin acids released from the wood when it is processed. Mechanical wood pulp is "brightened," as opposed to bleached, using less toxic chemicals than are needed for chemical pulps.
However, recent analysis of available data suggests that paper production may not be as harmful as it seems. Paper is known to sequester significant amounts of carbon dioxide
, since it is derived from plants, which sequester carbon dioxide by photosynthesis
. Paper can, even after manufacture, printing, distribution, and eventual disposal, still carry a significant carbon credit, in some cases equal to 200 kilograms (440.9 lb) of carbon dioxide per tonne of paper.
Paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
has a number of adverse effects on the environment
Environment (biophysical)
The biophysical environment is the combined modeling of the physical environment and the biological life forms within the environment, and includes all variables, parameters as well as conditions and modes inside the Earth's biosphere. The biophysical environment can be divided into two categories:...
which are known collectively as paper pollution. Pulp mill
Pulp mill
A pulp mill is a manufacturing facility that converts wood chips or other plant fibre source into a thick fibre board which can be shipped to a paper mill for further processing. Pulp can be manufactured using mechanical, semi-chemical or fully chemical methods...
s contribute to air
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....
, water
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
and land pollution. Discarded paper is a major component of many landfill
Landfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...
sites, accounting for about 35 percent by weight of municipal solid waste (before recycling). Even paper recycling
Paper recycling
Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste. Mill broke is paper trimmings and other paper...
can be a source of pollution due to the sludge produced during deinking.
According to a Canadian citizens organization, "People need paper products and we need sustainable, environmentally safe production." The amount of paper and paper products is enormous, so the environmental impact is also very significant. It has been estimated that by 2020 paper mills will produce almost 500,000,000 tons of paper and paperboard per year, so great efforts are needed to ensure that the environment is protected during the production, use and recycling/disposal of this enormous volume of material.
Pulp and paper is the third largest industrial polluter to air, water, and land in both Canada and the United States, and releases well over 100 million kg of toxic pollution each year.
Worldwide, the pulp and paper industry is the fifth largest consumer of energy, accounting for four percent of all the world's energy use. The pulp and paper industry uses more water to produce a ton of product than any other industry.
Chlorine and chlorine-based materials
ChlorineChlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
and compounds of chlorine are used in the bleaching of wood pulp
Bleaching of wood pulp
Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp, so that it becomes whiter. The main use of wood pulp is to make paper where whiteness is an important characteristic...
, especially chemical pulps produced by the kraft process
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
or sulfite process
Sulfite process
The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites , depending on the pH...
. Plants using elemental chlorine produced significant quantities of dioxins. Dioxins are persistent organic pollutants that are generally recognized among the most toxic human-released pollutants in existence. Elemental chlorine has largely been replaced by chlorine dioxide
Chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2. This yellowish-green gas crystallizes as bright orange crystals at −59 °C. As one of several oxides of chlorine, it is a potent and useful oxidizing agent used in water treatment and in bleaching....
and dioxin production very significantly reduced. The promise of complete removal of chlorine chemistry from bleaching processes to give a TCF (totally chlorine-free) process, which peaked in the mid-1990s, did not become reality. The economic disadvantages of TCF (according to a chemical industry association), the lack of stricter government regulation and consumer demand meant that as of 2005 only 5 to 6 percent of kraft pulp was bleached without chlorine chemicals. A study based on U.S. Environmental Protection Agency (EPA) data concluded that "Studies of effluents from mills that use oxygen delignification and extended delignification to produce ECF (elemental chlorine free) and TCF pulps suggest that the environmental effects of these processes are low and similar."
The used process water from a pulp mill contains a lot of organic material such as lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
and other organic material from the trees (including chlorinated organic material) resulting in high biological oxygen demand
Biochemical oxygen demand
Biochemical oxygen demand or B.O.D. is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The term also refers to a chemical procedure for...
(BOD) and dissolved organic carbon (DOC). It also contains alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s, and chelating
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....
agents and inorganic materials like chlorate
Chlorate
The chlorate anion has the formula ClO. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by a roman numeral in parentheses, e.g...
s and transition metal
Transition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
compounds. Recycling the effluent (see black liquor
Black liquor
Black liquor is the spent cooking liquor from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers....
) and burning it, using bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...
ponds and employing less damaging agents in the pulping and bleaching processes can help reduce water pollution.
Sulfur, hydrogen sulfide, and sulfur dioxide
SulfurSulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
-based compounds are used in both the kraft process
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...
and the sulfite process
Sulfite process
The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites , depending on the pH...
for making wood pulp. Sulfur is generally recovered, with the exception of ammonia-based sulfite processes, but some is released as sulfur dioxide during combustion of black liquor
Black liquor
Black liquor is the spent cooking liquor from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers....
, a byproduct of the kraft process, or "red liquor" from the sulfite process. Sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
is of particular concern because it is water soluble and is a major cause of acid rain
Acid rain
Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions . It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen...
. In 2006 the pulp and paper industry in Canada released about 60,000 tonnes of sulfur oxides (SOx) into the atmosphere, accounting for just over 4% of the total SOx emission from all Canadian industries.
A modern kraft pulp mill is more than self-sufficient in its electrical generation and normally will provide a net flow of energy to the local electrical grid. Additionally, bark and wood residues are often burned in a separate power boiler to generate steam. If the harvested trees are replanted a kraft mill can be carbon-neutral, but reforestation
Reforestation
Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation....
has been criticized for reducing biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
.
Air emissions of hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
, methyl mercaptan, dimethyl sulfide
Dimethyl sulfide
Dimethyl sulfide or methylthiomethane is an organosulfur compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from cooking of certain vegetables, notably maize,...
, dimethyl disulfide
Dimethyl disulfide
Dimethyl disulfide is an organic chemical compound with the molecular formula CH3SSCH3 which is the simplest disulfide. It is a flammable liquid with an unpleasant odor.DMDS can be produced by the reaction of methanethiol with sulfur:-Uses:...
, and other volatile sulfur compounds are the cause of the odor characteristic of pulp mills utilizing the kraft process.
Other chemicals that are released into the air and water from most paper mills include the following:
- carbon monoxideCarbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
- ammoniaAmmoniaAmmonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
- nitrogen oxideNitrogen oxideNitrogen oxide can refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:* Nitric oxide, also known as nitrogen monoxide, , nitrogen oxide* Nitrogen dioxide , nitrogen oxide...
- mercuryMercury (element)Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
- nitrateNitrateThe nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
s - methanolMethanolMethanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
- benzeneBenzeneBenzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
- volatile organic compoundVolatile organic compoundVolatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and...
s, chloroformChloroformChloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
.
Mechanical pulp mills
Wood pulpWood pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
produced primarily by grinding wood is known as "mechanical pulp" and is used mainly for newsprint
Newsprint
Newsprint is a low-cost, non-archival paper most commonly used to print newspapers, and other publications and advertising material. It usually has an off-white cast and distinctive feel. It is designed for use in printing presses that employ a long web of paper rather than individual sheets of...
. These mechanical processes use fewer chemicals than either kraft or sulfite mills. The primary source of pollution from these mills is organic material such as resin acids released from the wood when it is processed. Mechanical wood pulp is "brightened," as opposed to bleached, using less toxic chemicals than are needed for chemical pulps.
However, recent analysis of available data suggests that paper production may not be as harmful as it seems. Paper is known to sequester significant amounts of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, since it is derived from plants, which sequester carbon dioxide by photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. Paper can, even after manufacture, printing, distribution, and eventual disposal, still carry a significant carbon credit, in some cases equal to 200 kilograms (440.9 lb) of carbon dioxide per tonne of paper.