During methanization, the decomposition of waste is carried out in the absence of oxygen, without contact with ambient air and therefore without odor. At the end of the process, the volatile fatty acids responsible for odors are destroyed: the digestate produced is practically odorless, even once spread in the fields. Moreover, many farmers use methanization to reduce the odors of agricultural spreading of manure and slurry.

On the other hand, odours may come from waste before methanisation and be emitted during its transport, storage, unloading or loading. Measures can be taken to reduce these nuisances as much as possible:

• Carry out transport in sealed trucks
• Minimize the number of truck trips
• Carry out loading and unloading in a closed and watertight hangar
• Wash or rinse trucks frequently
• Force ventilation of storage buildings and treatment of stale air in a deodorization unit

To enable it to react quickly if unpleasant odours bother local residents, the operator can also set up surveillance on the site and in the surrounding area, by involving local residents in a "nose jury".

AND THE FLIES?

Since organic materials are stored in a closed, sealed area, flies are not attracted and do not proliferate around the methanizer.

Source: https://www.ademe.fr/sites/default/files/assets/documents/guide-pratique-methanisation-en-10-questions.pdf