Intensive farming risk assessment for your environmental permit
Source: gov.uk (2025-08-22)

What you must do to carry out a risk assessment if you're a farmer applying for a bespoke permit for intensive farming.

You must follow this guide if you’re applying for a permit or to change (vary) a permit for intensive farming under the Environmental Permitting Regulations.

Read the risk assessment overview (https://www.gov.uk/guidance/risk-assessments-for-your-environmental-permit) first. It explains the other steps to take in risk assessment and whether you need to read this guide.

As part of your risk assessment you must assess the following emissions:
- odour
- noise
- dust and bioaerosols (airborne particles that contain living organisms)
- ammonia
This is to check if they are likely to affect people or parts of the environment that could be harmed by emissions from your farm (called ‘receptors’).

Pre-application discussion

First, you need to fill in and submit the environmental permit pre-application advice form (https://www.gov.uk/government/publications/environmental-permit-pre-application-advice-form) to arrange a pre-application discussion.

In this discussion, the Environment Agency will:
- tell you about the application process
- identify nature conservation sites and neighbours close to your farm who will need to be considered in the environmental risk assessment
The Environment Agency will also tell you what should be included in the permit, for example:
- relevant buildings
- fuel storage
- carcass incinerators
- slurry storage
Odour and noise management

Odour and noise from the farm may affect receptors such as local residents, schools, hospitals, parks or businesses.

You’ll need to submit written odour and noise management plans as part of your application if:
- there are receptors within 400 metres of the site boundary
- the site has been the cause of odour or noise complaints in the past
Read the emissions guide (https://www.gov.uk/guidance/control-and-monitor-emissions-for-your-environmental-permit) to find out what you must do to prevent odour and noise pollution.

Ammonia emissions

You must submit a risk assessment of the impact of ammonia emissions from your site if you’re either:
- applying for a new bespoke permit
- applying to change (vary) an existing environmental permit in a way that will cause an increase of ammonia emissions to air from your farm
Factors that could cause an increase of ammonia emissions include:
- an increase in the number of, or change in the type of animals you keep on the farm
- an increase in the amount of manure or slurry you store
- a change to your site’s design or ventilation that could lead to higher ammonia concentrations
- a change to your site’s design or ventilation that could lead to ammonia settling on a nearby receptor, such as residential housing or a nature conservation site
Activities that release ammonia into water

You generally cannot get a permit for activities that result in releasing ammonia into water.

Contact the Environment Agency (#contact) before starting your application if you expect to release ammonia to water.

Ammonia screening

The Environment Agency will do a ‘distance screening’ on your application to check if your farm is close to nature conservation sites.

At the pre-application discussion, you’ll be asked for information so the Environment Agency can do a ‘simple screening’ of:
- expected ammonia emissions
- potential effects on nearby nature conversation sites
After this, you’ll be told if you need to produce a detailed modelling assessment of ammonia emissions to support your application.

Information you need to give for simple screening

In the pre-application discussion, you’ll be asked to give:
- farm name, address and Ordnance Survey grid reference
- ventilation system type (fan or natural)
- ventilation location (roof or side mounted)
- height of roof vents and the fan airflow speed in metres per second (if fans are roof mounted)
- amount of manure stored on your farm at any one time, in tonnes
- surface area (in square metres) of slurry storage facilities on your site, including lagoons
- type of cover used on slurry storage
- breakdown of animal numbers by type and by housing (for example, number of sows, growers and finishers on fully slatted floorings and partly slatted flooring)
- the most appropriate ammonia emission factors for the livestock and housing type
- site plan (for new applications or variations that include changes to the site layout)
- description of proposed changes (if you are varying your permit)
Ammonia emission factors and standards

At the pre-application discussion, the Environment Agency will work out the most appropriate ‘emission factors’ for your livestock and housing. You can check the standard ammonia emissions factors (https://www.gov.uk/guidance/ammonia-emission-factors-for-pig-and-poultry-screening-modelling-and-reporting) they use.

The Environment Agency will assess your ammonia emissions against 3 standards to check the risk of air pollution:
- ammonia critical level
- nutrient nitrogen critical load
- acidity critical load
The Air Pollution Information System (https://www.apis.ac.uk/critical-loads-and-critical-levels-guide-data-provided-apis) explains critical levels and loads.

Ammonia screening thresholds

The Environment Agency will check if there are any nature conservation sites close to your farm based on the following distances.

Results of simple screening

You will need to do detailed modelling if your result is above these screening thresholds:
- 1% for SPAs, SACs and Ramsar sites
- 50% for SSSIs
- 100% for local nature sites
If you are within 5 kilometres of a SSSI and your result is between the lower and upper screening thresholds, the Environment Agency will check other permitted farms in the area. If the combined emissions are above the upper threshold, you will need to do detailed modelling.

Detailed modelling

The Environment Agency will tell you if you need to do detailed modelling after completing their simple screening.

You need to do detailed modelling if:
- the original permit for your farm included instructions on how you must reduce ammonia emissions – an ‘improvement condition’
- your proposed activities are within 250 metres of any nature conservation site
- simple screening shows your emissions could affect nature conservation sites
To do detailed modelling, you need to use computer software that models the passage of a substance as it travels through the atmosphere until it reaches the ground.

Detailed modelling requires specialist knowledge. You can find a consultant to do it for you. They’ll charge for their services.

Contact the Environment Agency (#contact) if you want to do your own detailed modelling.

For guidance on detailed modelling for environmental permitting applications, check environmental permitting: air dispersion modelling reports (https://www.gov.uk/guidance/environmental-permitting-air-dispersion-modelling-reports).

Biomass boilers

You need to assess the environmental impact of nitrogen dioxide and particulate emissions if you:
- add a biomass boiler to an existing permitted site
- propose a biomass boiler in plans for a new site
Contact the Environment Agency (#contact) and ask to speak to your local officer to discuss how to do the assessment.

Poultry farms: when you do not need to do an air emissions assessment for your biomass boiler

You do not need to do an assessment of air emissions if:
- the fuel comes from virgin timber (whole trees and woody parts of trees), clean non-virgin timber (any timber or timber product that has not been treated), straw or miscanthus (also called elephant grass)
- the biomass boiler appliance and its installation are eligible for the Renewable Heat Incentive (https://www.gov.uk/non-domestic-renewable-heat-incentive)
In addition, the aggregate boiler net rated thermal input must be less than 0.5MWth (megawatt thermal), or it must meet all of the following:
- the aggregate boiler net rated thermal input is less than or equal to 4MWth
- no individual boiler has a net thermal input greater than 1MWth
- the stack height is at least 5 metres above the ground and may need to be higher if there are buildings within 25 metres – the stack must extend above the roof level of any building by at least 1 metre
- there are no receptors within 50 metres of the emission points
If your proposed biomass boiler installation does not meet this criteria, then use the following criteria for pig farms. You will not need to do an air emissions assessment if it meets the pig farm criteria.

Pig farms: when you do not need to do an air emissions assessment for your biomass boiler

You do not need to do an assessment of air emissions if:
- the fuel comes from virgin timber (whole trees and woody parts of trees), clean non-virgin timber (any timber or timber product that has not been treated), straw or miscanthus (also called elephant grass)
- the biomass boiler appliance and its installation are eligible for the Renewable Heat Incentive (https://www.gov.uk/non-domestic-renewable-heat-incentive)
In addition, the aggregate boiler net rated thermal input must be less than 0.5MWth, or it must meet all of the following:
- the aggregate boiler net rated thermal input is less than 1MWth
- the stack height is greater than 1 metre above the roof level of buildings within 25 metres (where there are no buildings within 25 metres, the stack height must be a minimum of 3 metres above ground)
- there are no SPAs, SACs, Ramsar sites or SSSIs within 500 metres of the emission points
- there are no National Nature Reserves, Local Nature Reserves, Local Wildlife Sites or Ancient Woodlands within 100 metres of the emission points
Where the aggregate boiler net rated thermal input is greater than 1MWth but less than 2MWth, you do not need to do an assessment of air emissions if, in addition to meeting all of the above criteria (including fuel type and eligibility for the Renewable Heat Incentive), there are no receptors within 150 metres of the emission points.

Net rated thermal input definition

Net rated thermal input means the rate at which fuel can be burned at the maximum continuous rating of the appliance, multiplied by the net calorific value of the fuel. It’s expressed in MWth. Ask the manufacturer of the biomass boiler for this information.

Dust and bioaerosols

You will need to produce and submit a dust and bioaerosol management plan with your application if there are relevant receptors within 100 metres of your farm, such as the farmhouse or farm worker’s houses.

In your dust and bioaerosol management plan, you must give details of control measures you will use to manage the risks from dust and bioaerosols from your farm. Tables 1 and 2 and checklist 1 and 2 in ‘assessing dust control measures on intensive poultry installations (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/297093/geho0411btra-e-e.pdf)’ explain the methods you should use.

The format of your dust and bioaerosol management plan should be similar to your odour and noise management plan (https://www.gov.uk/guidance/risk-assessments-for-your-environmental-permit).

Submit your application

Submit your application within 6 months of your ammonia screening to make sure the data remains current.

If your application requires detailed modelling, you must:
- show that your emissions are at the acceptable levels in the screening thresholds table
- provide plans to show how you will reduce them if they’re not
If you’re unable to propose ways to reduce your emissions below these levels, the Environment Agency will do a detailed assessment of your proposal. For SPAs, SACs, Ramsar sites and SSSIs the Environment Agency will consult with Natural England before they decide whether to approve your permit.

Contact

Contact the Environment Agency if you have queries.

General enquiries

National Customer Contact Centre PO Box 544RotherhamS60 1BY

Email xxx@xxx.xx (mailto:xxx@xxx.xx)

Telephone 03708 506 506

Telephone from outside the UK (Monday to Friday, 8am to 6pm GMT) xx-xxxx-xxxx

Monday to Friday, 8am to 6pm.