Call for Evidence : ​Non Waste Anaerobic Digestion over 100 tonnes per day: Permit technical requirements ​

Closes 9 Jan 2026

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BAT 34

In order to reduce channelled emissions to air of dust, organic compounds and odorous compounds, including H2S and NH3, BAT is to use one or a combination of the techniques given below.

Applicable – appropriate abatement techniques must be in place to achieve the emission limits in table 6.7 (only the limits for ‘all biological treatment of waste’ is relevant)

i. adsorption

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ii. biofilter

A pretreatment of the waste gas before the biofilter (e.g. with a water or acid scrubber) may be needed in the case of a high NH3 content (e.g. 5-40 mg/Nm3) in order to control the media pH and to limit the formation of N2O in the biofilter. 


Some other odorous compounds (e.g. mercaptans, H2S) can cause acidification of the biofilter media and necessitate the use of a water or alkaline scrubber for pretreatment of the waste gas before the biofilter.

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iii. fabric filter

The fabric filter is used in the case of mechanical biological treatment of waste


Some other odorous compounds (e.g. mercaptans, H2S) can cause acidification of the biofilter media and necessitate the use of a water or alkaline scrubber for pretreatment of the waste gas before the biofilter.

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iv. thermal oxidation

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v. wet scrubbing. Water, acid or alkaline scrubbers are used in combination with a biofilter, thermal oxidation or adsorption on activated carbon

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Note - Dust and TVOC are not relevant parameters for anaerobic digestion processes (i.e biological processes)
Parameter Unit BAT-AEL (Average over the sampling period) Waste treatment process
NH₃ (¹)(²) mg/Nm³ 0.3 – 20 All biological treatments of waste
Odour concentration (¹)(²) ouE/Nm³ 200 – 1,000 All biological treatments of waste
Dust mg/Nm³ 2 – 5 Mechanical biological treatment of waste
TVOC (³) mg/Nm³ 5 – 40 (³) Mechanical biological treatment of waste

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