Emission Mitigation Assessment
- Feb 11
- 6 min read
An air quality emission mitigation assessment is an increasingly common requirement for planning applications across the UK. Its purpose is to assign a monetary value to emissions generated by new developments and propose mitigation to offset those air quality impacts.
An emission mitigation assessment is usually delivered alongside an air quality impact assessment. They can be requested by local authorities upfront or used to mitigate exceedances discovered in air quality assessments.
This article explains what is emission mitigation assessment, how damage costs are calculated, and what air pollution mitigation is typically considered acceptable by local planning authorities.
The figure below illustrates a step-by-step guide for an emission mitigation assessment looking at road transport emissions.
What is an Emission Mitigation Assessment?
An emission mitigation assessment, also known as an emission mitigation statement, evaluates the emissions generated by a development and identifies air quality mitigation measures to offset those impacts.
Local authorities use emission mitigation assessments to ensure that mitigation measures are proportionate to a development's location and scale.
These assessments can be required when dispersion modelling indicates exceedances of air quality objectives. However, local authorities increasingly recognise that even where an individual development is considered acceptable in isolation, the cumulative effect of multiple schemes can still contribute to a deterioration in air quality. As a result, emission mitigation assessments are now frequently requested upfront.
Damage Cost Calculations
A core component of an emission mitigation assessment is the calculation of damage costs. These costs are published by the Department for Environment, Food & Rural Affairs (Defra) and are periodically updated to reflect new research on health impacts and appraisal methods.
Defra damage costs provide a nationally recognised value (£ per tonne) to the societal cost of emitting key air pollutants such as Nitrogen Oxides (NOx) and Particulate Matter (PM10 and PM2.5). They account for health outcomes such as premature mortality, respiratory hospital admissions, and productivity losses associated with air pollution exposure.
How are Damage Costs Calculated?
Air quality consultants use the Emissions Factors Toolkit to calculate NOx and PM2.5 emissions and the Damage Cost Toolkit to translate these emissions into costs typically over a five-year period.
Local Authorities with Emission Mitigation Assessment Requirements:
The table below lists examples of local authorities who have adopted air quality mitigation policy and summarises the circumstances in which an emission mitigation assessment is required.
Local Authority | Air Quality Policy Link | When is it required? |
Covers all local authorities across East Sussex, West Sussex, and Brighton & Hove involved in the The Sussex Air Quality Partnership. | Provides a screening checklist for when an emission mitigation assessment is required. This includes when the development is classified as major or in proximity to an Air Quality Management Area. | |
Warwick District Council | Contains an Air Quality Assessment and Mitigation Flow Chart to determine what type of assessment and mitigation measures are appropriate for each proposal. | |
Kent County Council and Medway Council in conjunction with the Kent and Medway Air Quality Partnership | Requires damage cost and mitigation for all major developments which are defined by Department for Transport traffic thresholds. | |
Swale Borough Council | Says an emissions mitigation assessment is required for all major developments to determine an appropriate mitigation . | |
Maidstone Borough Council | It uses a 'Screening checklist’ to screen out proposals which are unlikely to have a negative impact on air quality and an ‘Air quality and emission mitigation assessment checklist’ to identify what further action is required. | |
City of Doncaster Council | Mitigation measures are required for all developments. Electric Vehicle (EV) charging provisions are minimum standards. Medium-sized schemes must have additional mitigation identified through an emission mitigation assessment. | |
Newark & Sherwood District Council | Enforces damage cost and mitigation on major developments and emphasises the use of standardised air quality mitigation to provide clarity and consistency for developments up front. | |
Guildford Borough Council | Where an Air Quality Assessment identifies potential significant adverse impacts on sensitive receptors, an emissions mitigation assessment is required. |
Most emission mitigation policy follows a similar methodology; classification of development, calculating damage costs over a five-year period and providing proportionate mitigation measures. The main differences can be seen in classification criteria, when an assessment is required and the preferred mitigation measures.
For example, City of Doncaster Council requires an emission mitigation assessment for medium-classified developments whereas Newark & Sherwood District Council only requires assessments for major developments. Other local authorities such as Guildford Borough Council only specify emission mitigation assessments when an air quality assessment identifies exceedances.
Emission Mitigation Assessment Cost
The cost of an assessment can vary depending on the scale and complexity of the development. Air Quality Solutions provides emission mitigation assessments for £350.00 when undertaken alongside an air quality assessment for planning.
Costs may increase where a scheme is particularly complex or where additional input is required, such as frequent attendance at design team meetings, review of multiple layout iterations, or detailed advice on bespoke mitigation measures.
For a breakdown of air quality assessment pricing, including what influences assessment fees, read our article on Air Quality Assessment Cost.
Air Quality Mitigation Measures
There are a variety of acceptable mitigation measures for air pollution that can be used to offset impacts. The lists below provide categorises for transport and building emissions.
Transport emission mitigation measures:
Electric vehicle charging infrastructure (off-street or on-street)
Designated parking for low-emission vehicles
Support for car clubs and EV car clubs
Differential parking charges based on vehicle emissions
Compliance of commercial vehicles with European Emission Standards
Fleet strategies promoting low-emission fuels and technologies
Walking and cycling infrastructure improvements
Bike and e-bike hire schemes
Low-emission bus or waste collection services
Building emission mitigation measures:
High-efficiency building fabric (enhanced insulation and airtightness)
Zero emission heating systems (e.g. air-source or ground-source heat pumps)
Ultra-Low NOx boilers where combustion cannot be avoided
Mechanical ventilation with heat recovery (MVHR)
Solar photovoltaic (PV) installations
Connection to district heat networks
Use of low-emission fuels for standby generators
Operational energy monitoring and reporting
Incentives to encourage uptake of low-emission technologies by occupants
How to choose the right air quality mitigation?
The starting point should be the damage cost calculation as this indicates the scale of air quality mitigation required.
Where damage costs are derived from transport emissions, it is best to propose mitigation measures that address transport impacts. Aligning mitigation with the source of emissions ensures a clear and defensible link between impact and offset.
Mitigation for air pollution should be proposed after reviewing local policy. Many local authorities publish air quality guidance that contains preferred mitigation measures. Local policy can also contain standard mitigation for all developments, so reviewing it avoids repeating measures.
For example, Sussex Air Quality and Emissions Mitigation Guidance seeks to avoid counting measures that are already secured through building regulations or transport policy. Since Approved Document S is now in force, on-site EV charging is generally expected and should not be relied upon as mitigation unless it goes beyond regulatory requirements or supports off-site EV charging. Similarly, cycle parking and shelters are often policy requirements under local cycling strategies and therefore may not be accepted as mitigation.
In such cases, measures like enhancements to walking infrastructure or contributions to local sustainable transport improvements should be proposed as mitigation strategies for air pollution instead.
Emission Mitigation Assessment Summary
An emission mitigation assessment is an increasingly common requirement for planning applications across the UK, particularly for developments that generate significant traffic and/or located within an AQMA. Its purpose is to quantify the air pollution impacts of a proposal using damage cost methodologies and to identify proportionate mitigation to offset those impacts.
Local planning authorities use damage cost calculations to address both site-specific exceedances and the wider cumulative effects of development on public health. As a result, emission mitigation assessments are now frequently being requested upfront, enabling air quality mitigation to be embedded at an early stage and reducing delays later in the planning process.
Air Quality Solutions supports clients across the UK with emission mitigation assessments. If your development requires an assessment, please request a quote or call us on 0115 857 5801.
