Filtration & abatement

Why crematoria need filtration

Cremation releases pollutants including mercury from dental amalgam, dioxins and furans formed during cooling of combustion gases, particulate matter, carbon monoxide, nitrogen oxides, sulphur dioxide and hydrogen chloride. Many European countries, including the UK, Germany, the Netherlands and the Nordic countries, require abatement on all or most cremators, and the OSPAR Convention recommended mercury reduction across North-East Atlantic states. In North America, requirements vary by state and province.

The typical abatement process

A standard abatement line follows a predictable sequence.

• Flue gas cooling, usually in a heat exchanger or quench, lowers the temperature from around 850 °C to a level suitable for filtration.
• Dosing of activated carbon and hydrated lime or sodium bicarbonate adsorbs mercury, dioxins and acid gases.
• A fabric (bag) filter captures particulates together with the spent reagent.
• An induced draft fan maintains negative pressure through the whole system.
• Continuous emissions monitoring records key pollutants for compliance.

Some systems use fixed-bed carbon adsorbers instead of, or in addition to, dosing. Each approach has different running costs and residue volumes.

Wärmerückgewinnung

The heat removed during cooling is valuable. It can warm chapels and offices, heat water, pre-heat combustion air, or supply district heating networks, as is common in Scandinavia. Heat recovery can significantly reduce a crematorium's overall energy footprint and is increasingly a scoring criterion in public tenders.

Running costs and residues

Filtration adds running costs: reagent consumption, filter bag replacement, fan electricity, residue disposal as hazardous waste, and periodic emissions testing. Ask suppliers for annual consumption figures at your expected volumes and the guaranteed emission values. Also check the space required, since abatement plant can take up as much room as the cremator itself.

Retrofitting existing crematoria

Many operators add abatement to existing cremators. This requires a structural and process assessment: the cremator must provide stable flue gas conditions, the building needs space and access for the filtration plant, and the stack may need modification. Some manufacturers specialise in retrofitting systems to other brands of cremator, which can extend the life of a sound machine.

Questions to ask suppliers

• Which emission limits do you guarantee, and under which test conditions?
• What are reagent and electricity consumption per cremation?
• How long do filter bags last, and what does replacement cost?
• Is continuous monitoring included, and how are records stored?
• What heat recovery options can you offer for our building or network?
• Can you provide references of the same system operating for over five years?

Clear, written answers to these questions make tenders comparable and protect your organisation if emission limits are tightened in the future. Filtration is also a good place to plan ahead: designing space for abatement today can avoid an expensive rebuild later.

Finally, consider who will operate and maintain the system day to day. Filtration plant needs regular inspection, cleaning and reagent handling. Training and an accessible service contract are as important as the hardware.

Monitoring and reporting

Continuous emissions monitoring systems measure parameters such as carbon monoxide, oxygen, dust and temperature in real time, while periodic tests by accredited laboratories verify dioxins and mercury. Data must be stored and reported to regulators. Integrated systems combine cremator and filtration data in one interface, simplifying compliance and enabling operators to optimise the process. Ask how data is exported and how long it is retained.