[Peter]

If a project is operational and is having issues with gas quality and or getting stable gas production, and is still producing biogas the biological health may be able to recover with some operational optimization looking at factors like feedstock, nutrition, ammonia, sulfide, heating, and mixing.

If a digester is being fed and has stopped producing gas or has become acidified it may have reached a point where the digestate is too toxic for methanogens to recover. In this case the digester may need to be partially or completely emptied and reseeded.

A digester might also need to be cleaned out if a thick crust has accumulated in the digester, if the digester has filled with grit, or if tank walls or submerged mixers need to be repaired.

The seeding and startup process is a very sensitive time for the digester, it can be accomplished in as few as 8 weeks, but only with a clear plan, access to seed biomass, and close bioprocess monitoring to keep the startup on the right track.