Traditional flame cremation is widely chosen by families across the UK, but many people are unaware of the energy required by traditional flame cremation has been used in the UK for generations and remains the most common alternative to burial. But as more families consider the environmental impact of the choices they make, there is growing interest in understanding what happens during cremation — including the energy it requires and the emissions it can produce.
Modern crematoria are carefully regulated, with increasingly sophisticated systems used to control emissions. Nevertheless, traditional cremation remains fundamentally a combustion process.
So, what does flame cremation release into the atmosphere, how are those emissions controlled, and how does this differ from water cremation?
How Does Traditional Cremation Work?
Traditional cremation uses intense heat and combustion to reduce the body and coffin to mineral remains.
According to current UK Government technical guidance, a modern cremator typically contains two combustion chambers: a primary chamber, where the coffin and deceased are placed, and a secondary combustion chamber through which the combustion gases pass.
Most cremators currently operating in the UK are fuelled by natural gas or liquefied petroleum gas (LPG), although a small and growing number of electric cremators are also in operation.
Government guidance requires secondary combustion temperatures of at least 800°C for most cremators and 850°C for unabated cremators, subject to specific operating conditions.
The time required varies. Government guidance indicates that gas-fired cremations can take from around 50 minutes to more than two hours, depending on factors including body size.
This need to achieve and maintain high temperatures is one of the fundamental differences between traditional flame cremation and water cremation.
What Emissions Can Traditional Cremation Produce?
Combustion inevitably creates emissions.
Current UK Government guidance regulates and monitors a number of substances associated with crematoria.
These include:
- Carbon monoxide (CO)
- Particulate matter
- Hydrogen chloride (HCl)
- Mercury
- Nitrogen oxides (NOx)
- Dioxins and furans
Other emissions and environmental considerations can arise from the fuel, coffin and materials involved in the cremation.
The original research material used in preparing this article also identifies carbon dioxide, sulphur dioxide, hydrogen fluoride and various organic compounds among substances potentially associated with flame cremation.
The precise emissions from an individual cremation are not identical in every case. They depend on the type and age of the cremator, fuel source, coffin and other materials, combustion conditions and whether the cremator has flue-gas treatment or other abatement technology.
Why Does Cremation Produce Carbon Emissions?
The fundamental reason is combustion.
Most UK cremators currently use natural gas or LPG. These fuels are burned to generate the temperatures necessary for cremation.
Carbon emissions can therefore arise from several sources, including:
- fuel used by the cremator
- electricity consumed by the facility
- combustion of the coffin
Current Government guidance specifically requires crematoria to consider ways of reducing energy consumption and carbon emissions.
The industry itself is changing. Electric cremators are increasingly being introduced, partly because of the reducing carbon intensity of the UK’s electricity supply. There is also growing interest in alternative fuels, including biogas and hydrogen.
Traditional cremation technology may therefore become more efficient and less carbon intensive.
However, irrespective of the fuel used to heat the cremator, traditional cremation remains a process involving combustion.
What About Mercury?
Mercury has been a particular environmental concern for crematoria because of its historical use in dental amalgam fillings.
During flame cremation, mercury contained within dental amalgam can be released into the flue gases.
This is one reason why modern crematoria use flue-gas treatment systems.
According to current UK Government guidance, approximately 70% of UK cremations in 2023 were carried out in cremators fitted with flue-gas treatment systems.
These systems were originally introduced primarily to reduce mercury emissions.
The technology can also reduce:
- particulate matter
- acid gases
- dioxins
The latest guidance further requires new and replacement cremators, subject to specified exemptions, to be fitted with flue-gas treatment incorporating mercury abatement.
How Are Crematorium Emissions Controlled?
Modern crematoria are regulated facilities.
Current UK technical guidance establishes operating conditions, emissions limits, monitoring requirements and Best Available Techniques (BAT) designed to minimise environmental impact.
Controlling combustion conditions is particularly important.
Government guidance identifies factors including combustion temperature, oxygen levels, residence time within the secondary combustion chamber and carbon monoxide concentrations as important controls.
Flue-gas treatment provides an additional layer of emissions control.
Typically, reagents such as sodium bicarbonate or lime and activated carbon are introduced into the flue gases. These materials can help capture acid gases, mercury and dioxins before the remaining gases are released through the crematorium stack.
Particulate matter can subsequently be captured using filtration systems.
Can All Crematorium Emissions Be Removed?
No combustion process is entirely without environmental consequences.
Flue-gas treatment can substantially reduce certain pollutants, but different emissions require different control technologies.
For example, current Government guidance states that conventional flue-gas treatment does not remove nitrogen oxides (NOx).
Additional NOx reduction technology is available and is beginning to become more widely used, although its adoption remains limited.
This distinction is important.
Modern crematoria can significantly control their emissions, but controlling pollutants after combustion is different from using a process that avoids combustion in the first place.
Are Dioxins and Furans Produced by Cremation?
Dioxins and furans are among the pollutants addressed by UK crematoria regulation.
Government Best Available Techniques guidance explains that good combustion control is important because reducing carbon monoxide also helps minimise emissions of unburnt organic compounds, including dioxins and furans.
Modern flue-gas treatment incorporating activated carbon can further reduce these emissions.
This is another reason why the environmental performance of a modern regulated crematorium should not simply be compared with much older cremation technology.
Technology and regulation continue to improve.
Is Traditional Cremation Bad for the Environment?
It is more useful to recognise that traditional cremation has an environmental impact rather than simply describing it as environmentally “good” or “bad”.
The process consumes energy and produces emissions, but modern UK crematoria are subject to environmental controls designed to minimise those impacts.
The original source material used for this article also makes an important point: compared with worldwide emissions, crematoria account for only a relatively small proportion of harmful compounds and greenhouse gases.
The environmental discussion is therefore not about suggesting that crematoria are one of society’s largest sources of pollution.
Instead, it raises a different question:
If families could choose a dignified alternative that does not require flame cremation, should that choice be available?
This is where water cremation becomes particularly interesting.
How Is Water Cremation Different?
Water cremation — also known as alkaline hydrolysis, aquamation or resomation — does not cremate the body using flame.
Instead, it uses water, alkaline minerals and carefully controlled conditions to accelerate the natural process that occurs following death.
There is no burning of the body.
And this distinction is recognised explicitly in current UK Government environmental guidance.
The Government’s 2026 crematoria technical guidance states that alkaline hydrolysis does not have emissions to air and therefore does not fall within the scope of Part B air-pollution regulation applying to traditional crematoria.
That represents a fundamental environmental difference between the two processes.
Traditional cremation seeks to control and reduce the emissions produced by combustion.
Water cremation removes the combustion stage itself.
Water, Not Flame
For generations, families in Britain have largely been presented with two choices following a death:
Burial or flame cremation.
Water cremation introduces another possibility.
This doesn’t mean traditional cremation should be portrayed negatively. Modern crematoria are highly regulated, and advances in abatement, energy efficiency, electric cremation and alternative fuels continue to reduce their environmental impact.
The question is about choice.
As our understanding of environmental impact develops, families should be able to make informed decisions about what happens to them or someone they love after death.
At Aquatorium®, we believe that includes the opportunity to choose a process based on water, not flame.
Discover Water Cremation
Water cremation offers a different approach to the end of life — one based on water rather than combustion.
Discover what happens during water cremation, how the process works, what happens to the water afterwards and how the mineral remains are returned to the family.
[Discover How Water Cremation Works →]
Sources & Further Reading
This article draws primarily upon the latest UK Government technical guidance governing crematoria, supplemented by background material on the environmental impact of traditional cremation.
Department for Environment, Food & Rural Affairs — Crematoria: Process Guidance Note (PGN 5/2 (25))
Statutory technical guidance applying across the UK covering the regulation and environmental performance of crematoria. Published December 2025 and updated July 2026.
UK Government — Crematoria: Process, Types of Fuels and Flue Gas Treatment
Explains how modern gas and electric cremators operate, the fuels used and the role of flue-gas treatment in reducing mercury, particulate matter, acid gases and dioxins.
UK Government — Crematoria: Emissions Limits, Monitoring and Other Provisions
Sets out operating controls, emissions monitoring, emission limits and requirements relating to energy consumption and carbon emissions.
UK Government — Crematoria: Best Available Techniques (BAT)
Details the techniques available to crematorium operators for controlling emissions and improving environmental performance.
UK Government — Crematoria Technical Guidance: Who It’s For and How to Use It
Explains the scope of the UK’s crematoria emissions regulations and specifically confirms that alkaline hydrolysis does not produce emissions to air and consequently falls outside the relevant Part B air-emissions regulation.
Calgary Co-operative Memorial Society — More About Cremation and its Impact on the Environment
Background material discussing energy use, combustion and potential emissions associated with traditional flame cremation.