Biogases as alternate fuels

Biogases as alternate fuels

Biogas is the product of fermentation of man and animals' biological activity waste products when bacteria degrade biological material in the absence of oxygen, in a process known as anaerobic digestion. Since biogas is a mixture of methane (also known as marsh gas or natural gas) and carbon dioxide it is a renewable fuel produced from waste treatment. Biogas contains 50% to 70% of CH4, 2 % of H2 and up to 30 % of CO2. After being cleaned of carbon dioxide, this gas becomes a fairly homogeneous fuel containing up to 80 % of methane with the calorific capacity of over 25 MJ/m3. The most important component of biogas, from the calorific point of view, is methane, CH4. The other components are not involved in combustion process, and rather absorb energy from combustion of CH4 as they leave the process at higher temperature than the one they had before the process.

The actual calorific value of biogas is function of the CH4 percentage, the temperature and the absolute pressure, all of which differ from case to case.

Economical and operational considerations:

a) Biogas availability or potential

A biogas plant already exists and the gas yield is larger than what is already consumed in other equipment or the yield could be increased.

Organic matter is available and otherwise wasted; the boundary conditions allow for anaerobic digestion.

Environmental laws enforce anaerobic treatment of organic waste from municipalities, food industries, distilleries, etc.

b) Demand for mechanical power Other fuels are practically not available.

Other sources of energy or fuels are more expensive or theirsupply is unreliable. Having a fuel at one's own disposal is of specific advantage.

c) Possible revenue through selling mechanical power, electric power orrelated services to other customers (e.g. the public electricity supplycompany).