How Do Data Centres Affect Air Quality in the UK?
01-09-2026
Why is Data Centre Air Quality Becoming an Environmental Issue?
The UK is in the middle of a data centre boom, driven largely by cloud computing and the rapid growth of AI. As more hyperscale facilities are proposed and built, particularly around London, the M4 corridor and other digital infrastructure hubs, communities and regulators are asking harder questions about their impact.
While effects on energy demand, water use and carbon footprints are often reported, significant impacts on local air quality can occur and are less obvious.
Are Data Centres Really Causing Air Pollution?
Data centres themselves don’t emit pollutants simply by processing data. The air quality concern comes from the backup power infrastructure that supports them, which often comprises diesel generators, installed to keep servers running during power cuts.
When these generators run, whether for genuine emergencies or routine testing, they burn fossil fuels and release pollutants in the same way any diesel combustion source does. Going some way to improve their carbon emissions, diesel-like fuels derived from waste fats and oils (i.e. Hydrotreated Vegetable Oils – or HVOs) are increasingly being used.
The Difference Between Local Air Pollution & Carbon Emissions
It’s easy to conflate a data centre’s carbon footprint with its air quality impact, but they are different issues. Carbon emissions relate to a facility’s contribution to climate change, largely driven by electricity consumption.
Local air pollution is about pollutants released close to the site that can affect the health and amenity of nearby residents, and it’s these local impacts that air quality assessments are undertaken to address.
How do Data Centres Cause Air Pollution?
The primary source of air emissions from a UK data centre is on-site combustion, almost always from backup and standby power generation – typically by diesel, and sometimes gas-fired, generators. Understanding how and when these emissions occur is central to assessing their impact.
Backup Generators & On-Site Combustion
Data centres need constant uptime, so they need a backup source of power to cope with emergency situations when the National Grid might fail.
These emergency backup generators are mostly run periodically, usually monthly, as part of maintenance testing to ensure they will run properly when needed. Each test typically lasts an hour or so. It’s the combustion of fuel from the generators’ operation that emits air pollutants, worsening local air quality.
Particulate Matter & NO2 Emissions
The pollutants of greatest concern from diesel and gas generator emissions are nitrogen dioxide (NO2) and particulate matter (PM10 and PM2.5). Both are linked to respiratory and cardiovascular health effects, and both are subject to national air quality objectives. Because generator emissions are usually short-lived and infrequent, the scale of the impact depends on how many generators a site has, how large they are, and how often and for how long they are run.
What Data Centre Emissions Mean for Nearby Communities
For residents living near a data centre, the pertinent question is whether these periodic emissions could affect their health or quality of life, particularly where a facility sits close to housing, schools or other sensitive locations. Sensitive ecological sites, if located in close proximity to a data centre, may also be adversely affected by generator emissions, through processes such as nitrogen deposition.
Are There Dangers Living Near a Data Centre?
In most cases, because generator testing is infrequent and short in duration, the resulting air quality impact is limited. However, short term emissions can cause acute health effects if concentrations of the emitted pollutants are sufficiently high. This is why detailed assessment of air quality impacts is a requirement of the planning and permitting processes that determine whether data centre designs can be approved and developed.
How the Air Quality Impact of a Data Centre Is Assessed
A data centre air quality impact assessment is a structured, evidence-based process that follows the Environmental Impact Assessment and Environmental Permitting Regulations systems.
Understanding Existing Air Quality Around the Site
The first step is establishing the existing, or ‘baseline’, local air quality, which is typically available free of charge from central and local government websites. However, where data gaps exist, local monitoring can be required.
By establishing a baseline, predicted impacts from the operation of a data centre can be modelled and compared to existing local air quality in order to determine the magnitude and significance of predicted effects.
Identifying Emission Sources & Nearby Receptors
The next step is to identify all relevant emission sources on site, principally the generators, along with their emissions parameters (e.g. pollutant concentrations, volumetric flows, efflux velocities, exhaust temperatures, meteorological conditions and exhaust/stack heights), and the locations of nearby sensitive receptors that might be affected by them (e.g. homes, schools or protected habitats).
Modelling Changes in Local Air Quality
Air dispersion modelling, using the emissions source parameters as inputs, is then carried out to predict how pollutants released from the generators would disperse in the atmosphere and determine what concentrations might result at the identified sensitive receptor locations.
Determining Whether the Predicted Impact Is Significant
The modelled pollutant concentrations are compared against national air quality objectives to determine whether predicted impacts are significant. This judgement considers both the magnitude of any change and the sensitivity of the receptors affected.
The Role of Air Quality Monitoring
While modelling predicts likely impacts, particularly for proposed data centre developments, air quality monitoring provides real, measured data, either to establish an accurate baseline or to verify performance once a data centre is operating.
Monitoring Particulate Matter & NO2
Monitoring will typically focus on the key pollutants from diesel and gas generators – i.e. particulate matter and NO2.
Deciding Where & When Monitoring Is Needed
Not every scheme requires site-specific monitoring; often, existing background data are available from existing sources, such as government websites. Where monitoring is warranted, monitoring locations and durations should be proportionate to the scale of the development and the sensitivity of nearby receptors.
What UK Data Centres Need to Consider for Air Quality Compliance
Data centre operators need to navigate the regulatory frameworks covering both planning and environmental permitting, which can catch developers out if not considered early enough.
UK Air Quality & Atmospheric Emissions Requirements
Due to the large energy demands of data centres, backup generators will typically be of a size and number that exceed the thresholds for requiring an environmental permit from the appropriate environmental regulator (in England, the Environment Agency).
Permitting decisions reference relevant guidance and standards for generator emissions performance, and to minimise impacts, operators are expected to demonstrate that the Best Available Techniques are used when selecting appropriate generators.
How Data Centres Can Reduce Their Impact on Local Air Quality
There are practical steps operators can take, both in equipment choice and site design, to reduce their air quality impacts.
Reducing Reliance on Diesel Backup Generators
Minimising the number of generators, limiting testing to essential maintenance, and fitting effective exhaust abatement (such as selective catalytic reduction) can all significantly cut NO2 and particulate matter emissions.
Hydrogen Fuel Cells & Other Lower-Emission Alternatives
Some operators are exploring alternatives to diesel or HVO altogether, including battery energy storage systems and hydrogen fuel cells, which can reduce or eliminate combustion-related emissions from backup power, although they bring their own technical and infrastructure considerations.
The Role of Renewable Energy
Greater reliance on renewable electricity and improved grid resilience can reduce how often backup generation is needed in the first place, which in turn reduces the frequency of local air quality impacts, alongside the wider carbon benefits.
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