What does the law say about stack emissions?

Prior to the introduction of the Environmental Protection Act (EPA) during 1990, many processes such as those for the cremation of human remains were to all intents and purposes unregulated except as a statutory nuisance under The Control of Pollution Act or The Clean Air Act. This basically prohibited long periods of emissions of black or dark smoke from the chimney, as well as offensive odours, but little else.

Under the EPA Crematoria were designated as a lesser polluting or “Part B” process, regulated by Local Authorities in England and Wales, and by SEPA in Scotland.

As a part of the EPA, Secretary of States Guidance Notes were issued for dozens of processes, with Crematoria being covered by Process Guidance Note PG5/2. The contents of the first version of this note had a profound effect on UK Crematoria to the extent that the entire stock of UK cremators had to be replaced within a short, designated period. Old, pre-EPA cremators fell a long way short of the performance requirements of PG5/2 thus had to be scrapped. PG5/2 is reviewed periodically, with the last, and current issue being PG5/2 (2012). We can expect a review of the note again within the next few years when perhaps the emissions requirements will be updated to tighter limits, or new limits concerning the emissions of NOx for example being introduced for the first time.

A section in PG5/2 covers the continuous monitoring instrumentation and the form of reporting required, and is basically as follows for an abated plant:

Carbon monoxide: less than 100mg/m³ for any 30-minute period when cremating

Oxygen at the outlet of the secondary combustion chamber: a minimum of 3% when cremating

Particulate matter: less than 20mg/m³ for any 60-minute period when cremating when abated, or less than 80mg/m³ when unabated.

Secondary combustion chamber temperature: above 800°C at all times when cremating abated, or above 850°C at all times when cremating unabated.

PG5/2(12) states that recording of emissions should start 2 minutes after loading of a coffin into the cremator, and then average the next 60 minutes readings to give a cycle report. Earlier versions of PG5/2 specified that averages were calculated over the full cremation cycle but this was changed to 60 minutes when DEFRA in their wisdom decided that what happened after 62 minutes of the cycle didn’t matter. Whilst this is probably true for most of the time, it is not true for all the time. Any emissions after 62 minutes of the cycle are measured and logged, but these data will not appear in the summary reports.

A summary report is generated on a monthly basis for submission to the regulator, that sets down how the plant has performed. Other than for the secondary chamber temperature, PG5/2 states that the emissions limits above should be met on a 95th percentile basis, that is to say, 95% of all monthly readings should be below the emissions limit value.

To some extent this recognizes that cremation is a batch process, with potentially very variable loads being charged into the cremator, some of which may cause a problem that you can sometimes do nothing about. If 95% of readings muss pass, then 5% of readings can fail, but none of those that do fail should do so at a level of more than double the emissions limit value.

A 5% failure rate is equivalent to 1 in 20 cremations potentially causing a problem, which is perhaps not unreasonable.

All Crematoria have additional, independent tests carried out annually by an external organisation (such as Davies & Co (Environmental) Ltd), when the measurements of carbon monoxide, oxygen and particulate matter are also made, but in addition there are measurements to confirm emissions of hydrogen chloride, mercury (only for abated cremators) and Volatile Organic Compounds (VOC’s). These additional emissions are not required to be continuously monitored by the plant. A comparison of the results from the annual emissions tests and those generated by the plants own emissions monitoring and recording system should be made to confirm that the on-site system is accurate.

It is worth noting that you can elect to satisfy the emissions limits on either a mass or concentration basis for an unabated cremator, and your best choice will depend to some extent on the type of cremators you have installed. If the cremators you have are modern, well controlled and therefore energy efficient, then electing to meet the emissions limits on a mass basis will probably be the best option. Highly fuel-efficient cremators burn less gas and so the particulate matter emitted is present in a smaller volume of flue gas, and therefore at a higher concentration. The mass emission figure is not influenced by support fuel usage, and is therefore the one you should to elect to meet. The mass emission figure should be fairly consistent irrespective of fuel use.

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