Dry Fermentation extracts energy from biomass by anaerobic fermentation (biomass gasification) in the form of methane (CH4) and heat. This controlled process is executed in biomass power plants, where the methane is used to run engines generating electrical power. The process also generates heat. The dry fermentation process is not geared towards the production of bio fuel.
Biomass is introduced to the Dry Fermentation plants fermenter chambers in batches. This means there is no continuous flow of materials or liquids to be pumped into the plant via a pumping system but rather a pile of biomass, up to 50% solid, brought into a fermenting chamber and left alone for about 30 days. This type of biomass conversion is run automatically by the biological fermentation phases, given the balanced mix of required substrates and bacteria.
After the batch production period, another batch of biomass will be processed. The processed biomass can be used for composting purposes.
Dry Fermentation units can be “fed” with a variety of different biomass components. These substrates comprise of seasonally and constantly available raw materials.
Seasonally available biomass components:
- whole plant / grass silage
- landscape maintenance materials (eg prunings, cuttings)
- material from flooded areas
- material from biotopes
- material from road sides and parks
Constantly available biomass components:
- municipal solid waste (MSW)
- cow/pig/chicken waste
- market hall waste
- bio waste
- Organic materials from industrial production
All such materials can be processed in a dry fermentation unit and turned into biogas. It is important to define and maintain a sustained mix and quality of raw material in order to ensure efficient biogas production. This requires some knowledge specific to the Dry Fermentation process, as well and constant monitoring and control of the operations of the plant.
The resulting biogas produced would be constituted as follows:
|Methane||40 – 75%|
|Carbondioxyde||25 – 55%|
|Water vapour||0 – 10%|
|Nitrogen||0 – 5%|
|Oxygen||0 – 2%|
|Hydrogen||0 – 1%|
|Ammonia||0 – 1%|
|Hydrogen sulfide||0 – 1%|
This is a mix typical for biogas, regardless of the fermentation process, except that Hydrogen Sulfides are very low.