Biogas is generated by the fermentation of organic matter under oxygen-free conditions. Biogas consists chiefly of methane (55–65%) and carbon dioxide (35–45%) plus small amounts of other substances.

Biogas production reduces atmospheric emissions, due to the fact that the process captures the methane generated from biomass decomposition. Methane is a gas with a greenhouse effect 21 times stronger than that of carbon dioxide. If an identical amount of biomass were treated without control, through unattended composting, for example, the methane would release freely into the atmosphere. A well-functioning composting process produces no methane. However, the amount of the released carbon dioxide is identical to that resulting from the use of biogas while the energy content of biomass remains unexploited.

The decomposition residual from biogas production retains the nutrients contained in the original raw materials, such as nitrogen and phosphorus, making it suitable as a natural fertiliser. Use of the decomposition residual reduces artificial fertiliser requirements, energy consumption and atmospheric emissions all at the same time, because the industrial production of fertiliser consumes great volumes of energy.

Carbon dioxide neutral biogas may be used by combined power plants for electric power and heat production, or refined into vehicle fuels.


The cleanest and most efficient method

Dry fermentation is considered to be the most efficient method to produce renewable energy from organic matter, with the following major benefits:

• Raw materials decompose evenly, which guarantees uninterrupted, stable production of gas.
• Biomass remains within the reactor at a temperature above 55 ⁰C for a period of 15-20 days, which guarantees a hygienic end-product.
• With a dry decomposition process, the dry matter content may be very high, in the raw materials and the decomposition residual alike. This reduces transportation costs and transport-induced atmospheric emissions to a significant degree. The high dry matter content also minimises reject water volumes that must be cleaned.
• The energy yield is high due to the absence of additional heatable liquid.
• The raw material fermentation process is completed efficiently with a maximum volume of biogas produced.
• There will be no need for the long-term storage or post-composting of the final decomposition residual.
• The process is reliable and based on a field-proven technology: More than 15 Kompogas biogas plants have been built over the past 15 years.
  

Reliable bioenergy production

The Kompogas process is based on continuous thermophilic dry fermentation which is suitable for the treatment of all quickly decomposing organic solid matter types. The raw material’s dry matter content should be about 30%. When using a suitable mixture of materials, the dry matter content may be lower.

The biogas reactor is a horizontally installed tube made of steel or concrete containing a large, slowly turning agitator. Biomass travels through the tube in a plug flow while the material is mixed. The total treatment duration in the reactor is 15-20 days. The generated biogas is collected in the upper section of the reactor for subsequent use.

Due to the thermophilic temperature of 55-60°C, weed seeds, pathogens and other detrimental organisms are effectively eliminated. This results in a safe-to-use end product. Raw material with higher hygienic requirements can be pre-treated by using a separate hygienisation step.  Excess heat from the biogas power plant can be used for the hygienisation process.


The biogas process used by Biower is based on the technology developed by Kompogas. For additional information, please visit: www.kompogas.ch