Why mercury needs a dedicated abatement strategy.
Mercury entering the cremation process is highly volatile and passes predominantly into the flue-gas stream. Particulate removal alone therefore does not provide a complete mercury-control strategy.
Under the current UK Best Available Techniques guidance, flue-gas treatment targets not only mercury but also dioxins and furans, acid gases and particulate matter. This is why the abatement plant should be engineered as a multifunctional treatment system rather than as a single pollutant-removal device.
The treatment principle: cool, react, capture.
Control the flue-gas temperature
Combustion gases are cooled before treatment. Temperature management is fundamental to reagent performance, filtration and prevention of unwanted dioxin re-formation. The cooling duty can also create a heat-recovery opportunity.
Activated carbon captures mercury
Activated carbon is injected into the flue-gas stream or used in a downstream fixed bed or cartridge. Mercury is adsorbed onto the reagent; activated carbon also contributes to dioxin control.
Alkaline reagent controls acid gases
Sodium bicarbonate or hydrated lime is normally used with the carbon. The alkaline reagent reacts with acid gases, allowing several pollutant families to be treated within the same process chain.
Bag or ceramic filtration retains solids
Spent reagent, particulate matter and pollutant-loaded solids are separated from the gas stream. Barrier filtration also creates a reagent layer that can contribute to pollutant capture.
Two common treatment architectures
Injected reagent + barrier filter
Activated carbon and alkaline reagent are introduced upstream of a bag filter or another suitable dedusting device. Pollutants are captured by the reagent and the loaded solids are then retained by the filter.
Filter + fixed reagent bed
Particulate matter is removed first, after which the cleaned gas passes through a fixed bed or cartridge containing activated carbon and alkaline reagent. The bed must be replaced before pollutant breakthrough occurs.
What determines real-world performance?
Gas temperature
The treatment window must be compatible with the reagent and filtration technology. Cooling cannot be treated independently from the rest of the process.
Reagent dosing and distribution
Correct quantity alone is not enough. Reagent condition, injection stability, dispersion and contact with the flue gas all affect capture performance.
Filter condition and pressure loss
Filter media, cleaning sequences, differential pressure and air leakage affect both emissions performance and electrical consumption of the extraction system.
Maintenance and storage
The UK BAT guidance specifically highlights maintenance of bag filters and reagent injection systems. Adsorbent shelf life also matters because expired material can lose effectiveness.
Draft and extraction control
Adding treatment equipment changes system pressure losses. The extraction fan and control philosophy must maintain stable furnace pressure across changing filter conditions.
Residue management
Captured mercury does not disappear: it is transferred into spent reagent and filtration residues. Those contaminated residues must be managed through the appropriate waste route.
PG5/2(25): what changes for existing crematoria?
The current UK guidance was published on 4 December 2025. Unless a limited exemption applies, all cremators must be fitted with flue-gas treatment including mercury abatement four years after publication; otherwise operation is limited to 100 hours per calendar year. The guidance also states that existing cremators must comply with the emission limit values for new cremators from 4 December 2029.
For mercury, the published emission limit values are 50 µg/Nm³ for existing cremators and 30 µg/Nm³ for new cremators; the new-cremator value therefore becomes particularly important in planning the 2029 transition. Mercury periodic monitoring is specified annually using EN 13211.
Read the full CFI PG5/2(25) technical insight
Mercury abatement is also a retrofit engineering problem.
Installing abatement behind an existing cremator can affect far more than the filter itself. The project may require gas cooling, duct modifications, reagent storage and dosing, additional footprint, residue handling, new extraction capacity, electrical supply, automation changes and integration with the existing stack.
For this reason, the correct question is not simply whether a filter can physically be installed. It is whether the complete existing cremation line can operate reliably with the new pressure, temperature, monitoring and maintenance requirements.
Read PG5/2(25): Retrofit, re-abate or replace? →
Cooling creates an energy-recovery opportunity.
Both principal flue-gas-treatment arrangements require hot combustion gases to be cooled before treatment. The UK guidance explicitly identifies this cooling requirement as an opportunity to recover heat, usually as hot water for building heating or other useful demands.
The engineering objective should be to recover useful energy without compromising the temperature window required by the downstream treatment system.
Explore waste-heat recovery & energy valorisation →
Mercury abatement does not remove NOx.
Conventional mercury/acid-gas/particulate abatement should not be confused with NOx control. The UK guidance treats NOx separately and identifies selective non-catalytic reduction (SNCR) as an available option. Where NOx reduction is required, it therefore needs its own combustion and process-integration strategy.
CFI Systems approach
CFI Systems treats abatement as part of the cremation process, not as a box added at the end of a duct. The engineering review considers the furnace, secondary combustion, cooling, reagent injection, filtration, extraction, monitoring, automation, heat recovery and residue route together.
The objective is stable emissions performance over the real operating cycle — not simply nominal filter capacity.
Frequently asked questions
Why is activated carbon used in crematorium abatement?
Activated carbon adsorbs volatile mercury compounds from the flue gas and also contributes to the removal of dioxins and furans.
Why are sodium bicarbonate or hydrated lime also used?
They are alkaline reagents used to reduce acid gases. Combining them with activated carbon allows mercury, dioxins, acid gases and particulate matter to be addressed within one treatment chain.
Can mercury abatement be retrofitted to an existing cremator?
Often yes, but the complete installation must be assessed. Cooling duty, available space, ductwork, extraction capacity, electrical supply, automation, stack interfaces and remaining furnace life can all affect feasibility.
Does a mercury-abatement filter also remove NOx?
No. Conventional activated-carbon and alkaline-reagent flue-gas treatment does not remove NOx. NOx reduction requires a separate strategy, such as combustion optimisation and potentially SNCR where appropriate.
What happens to the captured mercury?
Mercury is transferred from the gas stream into spent reagent and filtration residues. The residues therefore require appropriate handling and disposal.