The parameters are:
- Acidity - Anaerobic digestion will occur best within a pH range of 6.8 to 8.0.
- Carbon-nitrogen ration (C/N) - a carbon - nitrogen ratio of about 30 - 1 is ideal for the raw material fed into a biogas plant.
- Temperature control - A temperature between 32°C and 35°C has proven most efficient for stable and continuous production of methane. but the action of the digesting bacteria will decrease sharply below 16°C.
- Percentage of solids - Anaerobic digestion of organics will proceed best if the input material consists of roughly 8 % solids. In the case of fresh cow manure, this is the equivalent of dilution with roughly an equal quantity of water.
- Plant design - above or below ground. There are pros and cons with either types.
- Continuous/batch operation - there are pros and cons with either types.
- Stirring - stirring the slurry in a digester is always advantageous, if not essential.
- Gas collection - A non-return valve here is a valuable investment to prevent air being drawn into the digester, which would destroy the activity of the bacteria and provide a potentially explosive mixture inside the drum.
- The level of carbon dioxide and proportion of methane will give valuable information about the state of the fermentation process as well. Infrared sensors are the best means employed today for this purpose. The need for calibration is minimal or nonexistent and the small size, relatively low cost and minimal power consumption make them ideal for this type of application.
