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Pollutant control

Pollutant control

Pollutant control is crucial in the modern world as human activities result in worldwide air, water, and soil pollution. You can help with the world's pollution problem by recycling waste instead of putting it in the rubbish bin. This may seem insignificant, but the combined effects of regional recycling initiatives help limit environmental pollution. Today we shall briefly cover the principles of pollution control and then cover some of the methods used to control the release of a variety of dangerous pollutants.

The meaning of pollution control

Pollution control is the limitation or eradication of the release of harmful substances into the environment.

The removal of dangerous substances can be considered pollutant control as well. Pollutant control only tackles waste and emissions released by human activity rather than emissions from natural sources. Harmful substances include greenhouse gases, metal particulates, smoke, carbon monoxide (CO), and oil.

Volcanic activity is a natural method whereby dangerous chemicals are released into the environment; volcanic eruptions can release vast amounts of sulphur dioxide (SO2) and soot.

Effects of pollutants

Polluting substances can damage the environment, ecosystems, and human health. Here are some key examples of how pollution affects our planet:

Greenhouse gases [such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)] released from fossil fuel combustion, industrial activity, and agriculture will contribute to the greenhouse effect and cause global warming. Climatic changes from warming, such as melting ice sheets, rising sea levels, droughts, and increased extreme weather, threaten ecosystems and pressurise low-income countries.

Releasing toxic chemicals like metal compounds, hydrocarbons, and pesticides into watercourses puts aquatic ecosystems at risk. These poisonous substances will bioaccumulate (persist) in ecosystems and eventually undergo biomagnification which involves them becoming present in larger quantities at higher trophic levels.

Carbon monoxide is released as a by-product of the incomplete combustion of fossil fuels in car engines. CO is an extremely dangerous molecule as it binds to haemoglobin (the blood-carrying molecule) and restricts the transportation of blood around the body, which can lead to seizures and heart attacks.

Principles of pollution control

These are the three principles of pollutant control that are used to varying degrees around the world:

  1. Accountability: This principle stresses that whichever individual or company is responsible for releasing pollutants into the environment should be accountable for these.

    Therefore, they should be the ones to implement removal methods and mitigate any further release of pollutants.

  2. Prevention: This principle suggests that any potential pollution released from an operation or activity should be stringently considered before commencing.

    This means considering any pollutant removal, storage, or neutralising methods and having them ready.

  3. Individual responsibility: This principle is more of a widespread plea as it is more challenging to implement strictly. It argues that the Earth is our home and we are lucky enough to have a habitable planet, so we should try our best to protect it.

    This means recycling, reducing vehicle use, and reducing mass consumption.

The importance of pollutant control

Let's take a look at some of the reasons pollutant control is important:

  • Sustainable future: controlling emissions and waste is essential for reducing the degradation of the biologically productive land we depend on.

This includes forests, agroecosystems, and oceans.

  • Climate change: greenhouse gases (GHG) contribute to the greenhouse effect in the atmosphere and warm the planet's system.

    Limiting GHG emissions is pivotal in preventing global warming.

  • Human health: many pollutants, such as smoke, carbon monoxide, and metal particulates, threaten human health.

Air and water pollution cause more death cases worldwide than any other factor.

  • Economic pressure: post-pollution control methods are often expensive and complicated to carry out, so preventing pollution from the source is important in relieving the financial stress of countries.

Methods of pollution control

So now we know what pollution control is and the principles behind it, let's have a look at the methods individuals and companies use to control specific pollutants:

Smoke (PM10)

Often shrouded in black smog, smoke can contain carbon (C), tar, and ash and causes respiratory problems and even cancer in animals and humans.

Smoke refers to the particulate matter released from the incomplete combustion of fossil fuels from vehicle exhaust pipes, industrial factories, and power plants.

Here are some of the methods used to reduce smoke pollution:

  • Clean Air Act 1956: this legislation was passed by the UK government due to London's 1952 'Great Smog'. This included the transition to smoke-free fuels and measures to reduce chimney smoke.

  • Coal treatment: the application of heat to coal removes the majority of tar.

  • Electrostatic precipitators: these devices apply a small electrostatic charge to gas to remove fine particulates like smoke and dust.

  • Cyclone separators: these work much like a centrifuge and spin air particles at high speeds to separate particles of heavier densities.

Smoke in Cape TownFigure 1: Smoke in Cape Town, South Africa, Wikimedia Commons.

Acid precipitation

Acid rain is precipitation exhibiting a pH of 5.2 or less. Nitrous oxide and sulphur dioxide emissions will react with water vapour in clouds to form nitric acid (HNO3) and sulphuric acid (H2SO4), which then fall as acid rain. Nitrous oxide will also initiate the formation of ground-level ozone (O3), which is a greenhouse gas.

These emissions are by-products of industrial processes and fossil fuel combustion.

Acid rain is limited in the following ways:

  • Sulphur dioxide:

    • Wet flue gas desulphurisation (FDL): this involves the wet scrubbing of gases using an alkaline slurry (made of limestone or seawater).

    • Dry FDL: dry desulphurisation involves spray towers and injection systems that inundate the gas with the alkaline sorbent to remove sulphur (S) molecules.

A sorbent is a substance which successfully adsorbs other molecules. They are extremely useful in removing impurities in industrial processes.

  • Nitrous oxide:

    • Catalytic converters: catalytic converters are attached to vehicle exhaust pipes and form a ceramic honeycomb made up of platinum (Pt), palladium (Pd), and rhodium (Rh). They will reduce nitrous oxides to harmless nitrogen (N) and oxygen (O2) gas.

A catalyst is a molecule that speeds up the rate of a reaction by offering an alternative reaction pathway.

Carbon monoxide and hydrocarbons

Carbon monoxide is a dangerous gas released from the incomplete combustion of fossil fuels and can cause fatal respiratory problems by binding to haemoglobin molecules. Hydrocarbons are released in the same way and can sometimes form volatile organic compounds (VOCs) in the air, which contribute to the formation of ground-level ozone. Oxidative catalysts in catalytic converters will oxidise carbon monoxide and hydrocarbons to carbon dioxide and water.

Oxidative catalysts contain platinum and palladium, whereas reductive catalysts contain platinum and rhodium.

Oil pollution

Oil spills from tanker accidents, pipeline leaks, and waste lubricating oil can pollute oceans and lakes. This can be very dangerous for marine organisms because they can become trapped and suffer hypothermia. The migration and reproduction of wildlife are affected, as well as sunlight availability for aquatic producers.

Oil pollution can be reduced in the following ways:

  • Recycling oil: lubricants and other recyclable oils must not be disposed of carelessly because they are tough to remove from the environment and can devastate aquatic ecosystems.

  • Tanker design: tankers with spill-proof designs must be used. This could be the implementation of a double hull, twin engines, and containment booms to limit the effects of leaks.

  • Improved navigation: any potentially environmentally endangering spots must be identified and avoided on oil tanker routes.

  • Oil spill clean-up: skimmers can manually remove oil from the surface, so can absorbent and polymerising materials.

Bioremediation is a method where oil is removed by increasing the productivity of naturally occurring microorganisms that break down hydrocarbons in oil. This is done by adding 'fertiliser', which will contain iron (Fe), nitrates (NO3-), and phosphates (PO43-) that will be deficient because of the faltering ecosystem. With access to these nutrients, the microorganisms can break down vast amounts of hydrocarbons and release inorganic ions into the water to rebuild the ecosystem.

Oil pollution in wetlandsFigure 2: Oil pollution in wetlands, Wikimedia Commons.

Pesticides

Polluting pesticides are synthetic mixtures sprayed directly on crops or over a general area to deter or exterminate 'pests' (e.g. locusts, aphids, caterpillars). These substances often contain toxic chemicals that can negatively affect non-target organisms and bioaccumulate in the ecosystem.

Pesticide pollution is reduced by introducing regulations on the quantities and types (most poisonous) of pesticides that farmers can use. Shifting to sustainable agricultural methods is essential in improving the gene pool in the agroecosystem and slowing the spread of disease.

Nutrients

The overuse of fertilisers in agriculture can result in soils becoming overloaded with nitrates and phosphates, which can leach into nearby waters. Sewage treatment plants focus on removing toxic substances, so masses of nutrients may be flushed into water sources. Urban waste contains lots of nutrients as well and is often improperly disposed of.

Especially in underdeveloped countries with poor infrastructure

Polluted waters can undergo eutrophication, which involves the formation of 'algal blooms' from an excess of nutrients. When these algal blooms are decomposed, the ecosystem will be starved of oxygen, and life cannot survive.

Here are some ways to reduce nutrient pollution:

  • Regenerative agriculture: innovative farming methods such as intercropping, under-sowing, and cover cropping will improve soil fertility and reduce the need for fertilisers.

  • Primary sedimentation: removes settleable organic solids from the slurry.

  • Secondary sedimentation: separates the waste into organic sludge and effluent after aerobic decomposition by microorganisms.

  • Tertiary sedimentation: involves anaerobic sludge digestion and phosphate materials.

Heavy metals

Lead (Pb) can pollute waters through the corrosion of old lead pipes and the improper disposal of waste containing cosmetics and paints.

Waste can be stored at high pH to decrease the solubility of lead particulates in the water.

Lead can damage the brain and kidneys if it is digested. Regulations to restrict the use of lead in plumbing, cosmetics and paints are put in place to reduce lead pollution.

Human activities like oil refineries, cement production, and incomplete fossil fuel combustion release dangerous mercury (Hg) particulates into the atmosphere. These particulates can be inhaled by humans or make their way into aquatic ecosystems and be consumed by fish.

The transition to renewable sources away from fossil fuels is key to reducing mercury emissions.

Mercury ingestion can cause memory loss and brain damage.

Pollution control type: transitioning to non-release pollution

Many of the types of control covered in this article are reactionary - meaning that they are only implemented once the pollution has been released/emitted. In order to make significant reductions in the amount of pollution we release, we need to shift to pollution prevention methods.

It is straightforward: if we do not release pollution in the first place, it will not damage the environment, and we will not have to expend energy and resources to remove it.

Examples of the types of controls for preventing pollution from the source include shifting to renewable energy (such as wind, solar, and geothermal power) and electric vehicles.

Pollutant control - Key takeaways

  • Pollutant control involves limiting or eradicating pollution in the form of emissions and waste.

  • The three principles of pollutant control are accountability (whoever is responsible should deal with the pollution), prevention (pollution should be prevented before it is released), and individual responsibility (duty to protect and care for our planet).

  • There are a variety of measures taken to control pollutants:

  • The Clean Air Act of 1956 implemented regulations for emissions from vehicles and chimneys.

  • Sorbents are sued in the desulphurisation of flue gases.

  • Catalytic converters in cars reduce nitrous oxides and oxidise hydrocarbons and carbon monoxide.

  • Sedimentation removes the organic content of waste and reduces nutrient pollution.

Frequently Asked Questions about Pollutant control

Pollution control is the prevention of the release of pollution, or the removal of pollution after its release.

There are many methods of pollution control. They include prevention of pollution from the source and removal of pollution by the organisation or individual responsible for its release.

Prevention, removal, and limitation.

Pollution control is essential to maintain the environment we depend on, limit climate change, and prevent impacts to human health.

Prevention, limitation, and removal.

Final Pollutant control Quiz

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What is pollutant control?

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The limitation of eradication of the release of polluting waste or emissions.

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What is the principle of accountability?

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Those responsible for the pollution must clear it up themselves.

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What is the principle of prevention?

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Individuals and organisations must consider any pollution before carrying out an activity or operation.

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What is the principle of individual responsibility?

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We are lucky enough to live on our planet so we have a duty to protect it.

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Which pollutants to catalytic converters remove?

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Answer

Nitrous oxides, carbon monoxide, and hydrocarbons.

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What is bioremediation?

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The addition of fertiliser to a polluted area to provide the conditions for microorganisms to break down the pollutants.

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What are the effects of greenhouse gases on the environment?

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They contribute to the greenhouse effect which causes global warming and climate change.

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What is a sorbent?

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A molecule that successfully adsorbs other molecules onto it.

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Why are volatile organic compounds dangerous?

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Because they initiate the formation of ground-level ozone.

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How can oil pollution directly affect marine organisms?

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They can become trapped in the oil and catch hypothermia.

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How can agricultural workers reduce pesticide pollution?

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By shifting to sustainable methods to increase soil fertility.

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What elements make up the oxidative catalyst in catalytic converters?

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Platinum and palladium.

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What are the effects of nutrient pollution?

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Eutrophication and anoxia of aquatic ecosystems.

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What emissions cause acid rain?

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Sulphur dioxide and nitrous oxides.

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What is a catalyst?

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A substance that speeds up a reaction by offering an alternative reaction pathway.

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What are the three principles of pollutant control?

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Accountability, prevention, and protection.

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What is environmental pollution?

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Any addition of unwanted chemicals or energy to the environment.

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What is point source pollution?

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Pollution which can be attributed to a certain point.

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What is non-point source pollution?

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Pollution that comes from a general area and is more difficult to attribute and quantify.

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What are the effects of greenhouse gas emissions on the environment?

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They cause global warming, which results in rising sea levels, droughts, and increased precipitation.

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Why is carbon monoxide so dangerous?

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Because it binds to haemoglobin in the body and restricts blood flow.

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What is sustainable agriculture?

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Agriculture which focuses on ecosystem and soil health to reduce the need for fertilisers and pesticides.

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Why is accountability important?

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Individuals and companies must take responsibility for the pollution they cause and act to remove it/ prevent future pollution.

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Why is prevention the most important principle?

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Because principle eradicates any damage to the environment whilst also saving time, money, and effort that would be spent removing pollutants.

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Why is protection important?

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We are fortunate enough to have a suitable home (the Earth) so we must protect it.

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What is an example of a prevention initiative?

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Switching from fossil fuels to renewable resources.

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How can governing bodies reduce pollution?

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By implementing strict laws and legislation that punishes the inappropriate management of waste. 

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How can individuals reduce pollution?

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By reducing energy use, vehicle use, and recycling appropriately.

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What are the impacts of oil pollution?

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Oil pollution suffocates aquatic ecosystems and affects migration and reproduction patterns.

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Why are nitrous oxide emissions dangerous?

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Nitrous oxide reacts with atmospheric water vapour to form acid rain.

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What is bioremediation? 

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Bioremediation is the use of microorganisms to remove polluting chemicals from soil or water. 

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Why is bioremediation important?

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Water and soil pollution is more problematic than ever, and bioremediation is an innovative method that utilises bacteria to remove dangerous pollutants.

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Aerobic microorganisms will produce.......as by-products.

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carbon dioxide and water 

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Anaerobic microorganisms will produce.....as by-products.

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methane and sulphides

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Bioremediation is used for removing...... 


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oil, pathogens, metal compounds, VOCs, ammonia, and nutrients.

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Define bioventing

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the process by which soils, waterbodies, or groundwater storages are aerated to provide decomposing bacteria oxygen for anaerobic respiration.

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What factors effect bioremediation?

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Temperature, oxygen, nutrients, moisture and pH are all factors effecting bioremediation. 


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Give 3 examples of bioremediation

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Oil spill cleanups, soil regeneration and groundwater treatment are all examples of bioremediation.


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Give 4 advantages of bioremediation

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  • Bioremediation relies solely on natural processes (metabolism of microorganisms) so is a fairly cheap process that requires limited machinery and manpower.
  • Bioremediation does not release any harmful chemicals into the atmosphere.
  • When treating polluted groundwater, bioremediation can be carried out ex-situ. This means that the polluted location will not be disturbed. 
  •  Maintenance costs are low.


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Give 4 disadvantages of bioremediation

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  • Only biodegradable substances can be treated.
  • Toxins may be leftover that spread into the surrounding environment.
  • It takes a lot of time for the microbes to break down the contaminant.
  • Very specific conditions are required.


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What does ex-situe mean?

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off site

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Fungi are especially effective at breaking down.....

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fertilisers and metal compounds.

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What is bioaugmentation?

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Bioaugmentation is the addition of novel microorganisms to a polluted area, which are then provided with suitable conditions to break down polluting chemicals.

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What is biostimulation?

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Biostimulation involves the addition of chemicals or substances that activate microorganisms in the area to break down pollutants.

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What is intrinsic bioremediation?

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Intrinsic bioremediation utilises the native microbiota in the polluted area. Suitable conditions are provided (temperature, oxygen, nutrients) for the microorganisms to start breaking down matter.

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