Air pollution from farming: preventing and minimising

How to comply with legal restrictions on burning farm waste and measures you can take to reduce agricultural emissions.

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Agriculture contributes significantly to emissions of greenhouse gases and other pollutants. It is also one of the sectors which any potential climate change will affect the most.

This guide outlines the possible threats and opportunities posed by global warming. It also has advice on measures you can take to reduce emissions of CO2, methane, nitrous oxide, ozone-depleting substances and ammonia.

You will also find details of the legal restrictions on burning farm waste and stubble, as well as guidance on reducing noise and dust pollution.

Agriculture and climate change

Climate change - caused by an increase in greenhouse gases - is the most serious long-term challenge facing the world today. Because of the threat it poses to the natural environment, farming will be one of the first sectors to feel its effects.

The potential threats include:

  • changes in rainfall distribution
  • prolonged and more frequent droughts
  • more storms and other extreme weather events
  • rising sea levels flooding low-lying land
  • changes in soil water balance
  • new pests and diseases, or an increase in existing ones
  • increased risk of heat stress in livestock

Greenhouse gas emissions need to be reduced as a way to protect the environment and its natural systems. The process of reducing greenhouse gas emissions is called mitigation.

There is an urgent need to develop strategies to manage and reduce the effects a changing climate will have on our environment due to the greenhouse gases which have already entered the atmosphere. Taking steps to manage and minimise the effects of these changes is known as adaptation.

Research suggests that climate change won’t threaten the viability of UK agriculture overall but as a farmer, you need to be prepared to adapt to evolving pressures. Climate change will also present opportunities for new crops and markets which you should be ready to seize.

One potential contribution that farming can make to tackle climate change is through producing bioenergy to replace fossil fuels and growing crops to replace other raw materials used in manufacturing. For example, bioethanol and biodiesel can be used to replace transport fuels, while biomass from crops can be used to generate heat and electricity.

Much of the advice in this guide is based on the Department for Environment, Food and Rural Affairs (Defra) publication - Protecting our water, soil and air: a code of good agricultural practice for farmers, growers and land managers (CoGAP). This is not a statutory code, but best practice guidance, which can help you avoid causing pollution.

Download Defra’s CoGAP from the Agricultural Document Library (ADLib) website (PDF, 1.38MB).

Greenhouse gas emissions from agriculture

Greenhouse gases are always present in the atmosphere and absorb the sun’s radiation - preventing that heat from escaping.

Most greenhouse gases occur naturally and are important for maintaining a global average temperature of approximately 15°C - if no greenhouse gases existed in the atmosphere, the global average temperature would be around -6°C. The main greenhouse gases are:

  • water vapour
  • CO2
  • methane
  • nitrous oxide

Other significant greenhouse gases include chlorofluorocarbons (CFCs). These are man-made refrigerants which are thought to be responsible for causing the holes in the ozone layer above the Earth’s poles.

Pollution is thought to be adding to the natural greenhouse effect - causing the temperature of the Earth’s surface to rise. Some of the greenhouse gases can stay in the atmosphere for a long time, so it’s important to take action to reduce such pollution as early as possible.

Agriculture and forestry are the second largest source of greenhouse gases in the UK - accounting for 7% of the UK’s total emissions.

Of the greenhouse gases, CO2 pollution is a concern for everyone - rather than being an issue specific to farmers. CO2 has been responsible for most of the global warming to date, but agriculture contributes to just 1% of the country’s emissions.

Nitrous oxide and methane are the most significant greenhouse gases for farmers. Agriculture is responsible for 66% of the UK’s nitrous oxide emissions and 46% of UK methane emissions.

In many cases, reducing the amount of greenhouse gases your farm produces can also save you money.

Reducing CO2 emissions on farms

CO2 is the greenhouse gas responsible for 70% of the global warming to date. This has been caused by a 37% increase in atmospheric CO2 since 1850. The main causes of this are:

  • burning fossil fuels - eg coal, oil and gas
  • burning/clearing forests
  • draining and degradation of peatlands

Use fossil fuels efficiently

The following techniques can help you reduce your CO2 emissions and farm running costs:

  • regularly servicing engines - this can reduce fuel consumption by 5-15%
  • choosing suitable tractors/machinery - eg using the lowest-powered tractor capable of the task
  • avoiding unnecessary journeys and cultivation passes
  • maintaining the efficiency of fixed equipment - eg grain driers, refrigerated stores and bulk milk tanks

Reduce heat loss

Heated glasshouses, mushroom houses and polythene covered structures use a lot of energy. Installing thermal screens can greatly increase efficiency. These prevent energy being lost through ventilation, infra-red radiation or convection, while allowing use of the sun’s energy to be maximised.

You can also save fuel by ensuring any boilers or burners are correctly maintained. And by insulating the walls, roofs and heating pipes of your buildings.

Use alternative energy sources

Where possible, consider using non-fossil fuel sources of energy. Alternative energy opportunities include:

  • solar power
  • heat pumps
  • straw-burning boilers
  • biogas from manure digestion
  • wind power
  • water power

These techniques are more likely to be cost effective when the amount of energy needed is consistent throughout the year. Before investing in such a project you should first check it’s financially viable by calculating the set-up and running costs.

Use fertilisers efficiently

Manufacturing nitrogen fertilisers uses large amounts of fossil fuels. So it’s important to only use fertilisers at rates and times suitable for the cropping situation. Take into account any organic manures or sewage sludge you have applied when calculating application rates.

Ensure fertiliser spreaders are regularly and properly maintained and the setting you use is appropriate for the type of fertiliser.

Protect the natural environment

Agriculture also contributes to CO2 emissions when uncultivated land or pasture is converted to arable land. Disturbing soil - eg by ploughing - stimulates soil bacteria which release both CO2 and nitrous oxide through respiration. The breakdown of liming materials in the soil also releases fossilised CO2.

These processes can be avoided by preserving uncultivated land. For similar reasons, peat soils should also be protected from degradation caused by drainage and cultivation.

If you receive payments under the Single Payment Scheme (SPS) and certain rural development schemes, you must meet certain standards of good agricultural and environment condition under cross compliance. For more information, see the guide on standards of Good Agricultural and Environment Condition (GAEC). For more information on agricultural funding and support schemes, see the section on SPS, cross compliance and stewardship.

Reducing methane and nitrous oxide emissions on farms

After CO2, methane is the second most significant greenhouse gas - having doubled in concentration since the 1800s. This has mainly been caused by:

  • emissions from livestock
  • rubbish decay in landfill sites
  • leaks from gas fields
  • decomposition of vegetation in rice paddies

Methane is responsible for 24% of global warming to date. Most of the methane produced by agriculture is from the normal digestive processes of livestock - the rest comes from animal excreta.

Direct losses of methane from animals are due to fermentation caused by bacteria in the stomach. Cows produce the most methane per animal - followed by horses, sheep, goats and pigs. Emissions from lactating dairy cows are particularly high.

Poultry don’t produce any methane directly, but a small amount is released from their excreta. However, intensive poultry farms and poultry production facilities - ie those with a capacity exceeding 40,000 birds - must have an environmental permit to operate and show compliance with the proper removal, disposal and/or treatment of waste matter. For more information, see the guide on minimising farm waste, composting and recycling.

You can reduce agricultural methane emissions by:

  • reducing livestock numbers
  • improving productivity and fertility
  • modifying the diets of livestock

A small amount of methane is also released by bacteria in slurry and manure. Ideally, livestock slurry should be treated first using a controlled anaerobic digestion process. This stabilises the slurry while also producing a biogas which can be used for heating or generating electricity. For more information, see Sewage sludge, slurry and silage.

Nitrous oxide

Levels of nitrous oxide in the atmosphere have increased by an estimated 13% due to industrialisation and it is responsible for about 6% of global warming.

The main sources of nitrous oxide emissions are:

  • agriculture
  • industrial processes
  • deforestation

Nitrous oxide pollution from agriculture mainly comes from using inorganic nitrogen fertilisers and from storing manures.

You can reduce nitrous oxide emissions by taking the following steps to ensure your fertiliser use is efficient and nitrogen losses are minimised:

  • regularly testing your fertiliser spreader to ensure accurate application
  • ensuring that any staff applying fertiliser are well trained and only use the minimum necessary
  • crop nutrient management planning
  • carrying out soil analysis to establish how much fertiliser is needed
  • using technology to target nutrient use and cut machinery use
  • incorporating manures to reduce the need for inorganic fertiliser
  • improving slurry handling

You can also reduce levels of nitrogen in your livestock’s excreta by matching the nitrogen in their diet to their specific needs.

Refrigerants and ozone-depleting substances

Ozone-depleting substances (ODSs) are substances which - if allowed to escape - can damage the ozone layer in the upper atmosphere. This allows more of the sun’s ultraviolet-B radiation to reach the Earth’s surface. This could have major consequences for both human health and the economy by:

  • increasing skin cancer
  • damaging crops
  • endangering wildlife/livestock

ODSs are also greenhouse gases. This means they can contribute to global warming by trapping heat in the atmosphere.

ODSs include chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The use of ODSs is tightly regulated - many are already banned or are being phased out.

Fluorinated gases (F-gases) are often used as a replacement for ODSs. Their use is strictly regulated as they are also powerful greenhouse gases.

Common uses for ODSs and F-gases include:

  • refrigeration and air-conditioning equipment
  • firefighting fluids
  • aerosols
  • solvents
  • foam blowing agents
  • high-voltage switchgear

Refrigeration equipment maintenance and disposal

To minimise any leaks of ODSs you should ensure that all of the refrigeration equipment on your farm is properly maintained. You should not allow any unused equipment to deteriorate.

When disposing of commercial refrigeration equipment you must - by law - ensure that any ODSs are safely removed first. This includes fridges, freezers, chiller cabinets or when dismantling cold store rooms. You will need to contact a specialist fridge disposal company to take care of this for you. Your local council’s waste disposal service isn’t obliged to accept such equipment from a business, but they should be able to give you advice on how to dispose of it locally.

You can also find out where you can dispose of refrigeration equipment by using the NetRegs Waste Directory on the NetRegs website.

Reducing ammonia emissions on farms

The main sources of ammonia emissions in the UK are from slurry and manure.

Ammonia is formed by the breakdown of urea in animal manures and slurries, or uric acid in poultry manures. Most of the available nitrogen in manures is in the form of ammonium-nitrogen, which can be used as a direct substitute for inorganic fertiliser.

However, ammonia can easily escape as a gas and cause significant environmental damage when it’s redeposited, by:

  • upsetting the balance for vegetation that relies on low levels of nitrogen in the soil or water - eg heathlands and bogs
  • causing excess soil acidity - which can damage certain types of vegetation

Ammonia can also have a direct toxic effect on trees or other vegetation, for example lichens and mosses, if they grow close to a source of high emissions, as it can damage foliage and slow growth.

Manage animal diets carefully

One of the first steps to reduce levels of ammonia is to ensure that your animals are not fed more protein than is necessary for your target level of milk, meat or egg production. This will reduce the amount of nitrogen excreted as urea in urine and faeces - or uric acid in poultry - which would be mostly converted to ammonia.

Phase feeding is a technique used in pig and poultry farming that closely matches the animals’ diets with the particular requirements of different growth stages. You can also get feeds for pigs which are low in nitrogen but maintain production.

Increasing the efficiency of nitrogen use is more difficult when farming cattle and sheep. High energy, lower protein feed - such as maize silage - may be beneficial.

Keep animal housing clean

High standards of cleanliness can help reduce ammonia emissions - as well as odour - from livestock buildings. Ammonia losses are higher if the walls and floors are constantly covered with urine or layers of faeces. Depth is less important than the surface area when measuring ammonia emissions.

You can also remove slurry by frequently flushing, scraping and washing floors. Solid manure should be removed and transferred to a store as often as possible.

For poultry, ammonia loss can be reduced by ensuring droppings are able to dry rapidly. This can be done by maintaining dry, crumbly litter and managing drinking systems to avoid spillage.

Reduce ammonia loss from slurry stores

Ammonia loss from slurry stores can be reduced by:

  • using a tank with a lid
  • allowing a crust to form
  • covering the slurry with straw or some other floating cover - eg rapeseed oil, plastic or light expanded clay aggregate
  • minimising any stirring
  • avoiding the exposure of fresh slurry by filling and emptying the store below the surface

Apply manures and slurries accurately

You should only use the amount of manure or slurry that is needed to provide the crop nutrient requirements. You must take into account the nutrient requirements provided by the soil and other organic or inorganic fertilisers you have applied.

Before applying manure, slurry or other organic fertilisers you should check if you are in a designated Nitrate Vulnerable Zone (NVZ). There are Regulations which apply to the spreading of fertilisers in NVZs. You can find out more about NVZs in Nitrate Vulnerable Zones (NVZ).

There’s some free software available for farmers called PLANET which can help you plan efficient and environmentally friendly nutrient applications for your crops. Find out more about the PLANET software and how to get hold of a copy on the PLANET website.

Diluting slurries can be a good way to reduce emissions. The application method you choose is also important. The following methods of application are listed in order of effectiveness:

  1. injection - most efficient, however, not all land is suitable
  2. band spreading
  3. splash-plate spreading - least efficient

Rainfall, wind speed and air temperature all have an influence on ammonia emissions from slurries applied to land. The effect of rainfall on ammonia emissions depends on the soil type and wetness.

You should also consider how close you are to any nature conservation sites. In particular, you must not apply manure or slurry on any areas where it’s prohibited because of specific management agreements. You can find out more in the guide on sewage sludge, slurry and silage.

Generally, ammonia emissions are reduced if slurry is applied on a cool, still day. Application just before or during rainfall can also be beneficial - if the soil is free-draining and there’s no risk of causing water pollution.

Ammonia emissions from solid manures can be reduced by incorporating it beneath the soil surface. To be most effective, you should incorporate it within four hours and no later than 24 hours.

For more information, download Defra’s guidance on ammonia pollution caused by farming from the ADLib website (PDF, 1.03MB).

Burning wood and vegetation on your farm

It is a criminal offence to burn most farm wastes to dispose of them. Burning wastes to dispose of them pollutes the air with poisonous gases, grit and dust. Harmful chemical residues can also contaminate the soil, groundwater and surface waters.

There are several better alternatives to manage the waste you produce on your farm, for example:

  • changing processes to reduce or eliminate waste
  • reusing and recycling materials - eg silage wrap
  • sending waste for recovery - eg oils and solvents
  • composting biodegradable waste
  • burning waste in an authorised incineration plant, furnace or boiler - preferably to produce alternative energy
  • disposing of waste at an authorised landfill site

Wastes that you can burn on your farm

The waste types that can be disposed of by burning without an environmental permit are restricted to vegetation, untreated wood and untreated timber. You can only burn these wastes at the place where they were produced. For example, you can burn the following types of waste either on a bonfire or in an incinerator:

  • logs and branches from fallen or chopped down trees
  • untreated timber from fence mending
  • untreated timber packaging, eg pallets
  • hedge trimmings
  • crops and vegetation
  • leaves and bark

Before you burn these wastes, you must first register for an exemption from environmental permitting with the Environment Agency. Find out about burning exemptions and how to register for them on the Environment Agency website.

You must not burn any other types of waste you produce on your farm. If you do, you will be committing a criminal offence and you could be prosecuted.

Burning stubble or crop residues

It is illegal to burn cereal stubble or crop residues, eg oil seed rape, except in certain specified circumstances which are listed in in The Crop Residues (Burning) Regulations 1993.

Burning stubble and crop residues releases greenhouse gases into the atmosphere and can cause a nuisance. It can also deprive the soil of valuable organic material.

As an alternative to burning stubble and crop residues it is good practice to bale and cart straw from the fields, or chop the straw and plough it into the soil before establishing the next crop.

Burning animal carcasses on your farm

If you handle or dispose of fallen stock you must comply with the requirements of the Animal By-Products Regulations. You can find out more by reading our guide on fallen stock.

If you operate an on-farm incinerator that burns whole carcasses only it must be approved by Animal Health. Find out about getting approval for whole-carcass incinerators on the Defra website.

If you burn non-agricultural animal carcasses or parts of animal carcasses, in your incinerator you will also need an environmental permit from either your local authority or the Environment Agency, as well as authorisation by Animal Health. You can find out about environmental permits in our guide on environmental permits - who needs one and how to comply.

It is an offence to burn animal carcasses in the open except during disease outbreaks where Animal Health has given authorisation for burning.

Noise and dust pollution from grain dryers

Grain drying and conditioning can cause a nuisance for your neighbours due to the amount of noise and dust it creates. If it is causing a nuisance, your local authority can stop you from working, or can set limits on your work. They can restrict:

  • the type of machinery you are allowed to use
  • your working hours
  • noise levels permitted from your premises

You can be fined if you do not comply with any restrictions imposed.

There is some good practice advice to avoid causing a nuisance, including:

  • using buildings, trees or hedges to shield neighbours from dust and noise
  • keeping windows and doors shut
  • not carrying out noisy operations at night
  • maintaining equipment to prevent it becoming excessively noisy
  • insulating your building with sound-proofing materials

Further information

Environment Agency Helpline

03708 506 506

Defra Helpline

08459 33 55 77

Download the Defra air, soil and water protection guidelines from the Agricultural Document Library website (PDF, 1.38MB).

Nutrient-planning guidance on the PLANET website.

Download Defra’s agricultural ammonia emissions guidance from the ADLib website (PDF, 1.03MB).

NVZ guidance on the NetRegs website.

Ringelmann charts for purchase on the BSI website.

Waste burning exemptions advice on the Environment Agency website.

Published 23 August 2012
Last updated 13 June 2013 + show all updates
  1. Fixing references to specialist guides

  2. First published.