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.
and operational considerations:
availability or potential
plant already exists and the gas yield is larger than what is already consumed
in other equipment or the yield could be increased.
matter is available and otherwise wasted; the boundary conditions allow for
laws enforce anaerobic treatment of organic waste from municipalities, food
industries, distilleries, etc.
for mechanical power Other fuels are practically not available.
sources of energy or fuels are more expensive or theirsupply is unreliable.
Having a fuel at one's own disposal is of specific advantage.
Possible revenue through selling mechanical power, electric power orrelated
services to other customers (e.g. the public electricity supplycompany).