• many biogas units are operated inefficiently;
• many of the existing biogas systems are not used due to minor mistakes;
• biogas users tend to increase energy consumption to the point of wastage, then
requiring additional energy in the form of firewood.
A more serious problem, however, is the fact that a household biogas system program can
only reach the small percentage of farmers who have the investment capital required. The
majority of rural households will continue to use firewood, dried cow dung and harvest
residues as fuel.
Reduction of the greenhouse effect
Last but not least, biogas technology takes part in the global struggle against the greenhouse
effect. It reduces the release of CO2 from burning fossil fuels in two ways. First, biogas is a
direct substitute for gas or coal for cooking, heating, electricity generation and lighting.
Additionally, the reduction in the consumption of artificial fertilizer avoids carbon dioxide
emissions that would otherwise come from the fertilizer producing industries. By helping to
counter deforestation and degradation caused by overusing ecosystems as sources of
firewood and by melioration of soil conditions biogas technology reduces CO2 releases from
these processes and sustains the capability of forests and woodlands to act as a carbon
Methane, the main component of biogas is itself a greenhouse gas with a much higher
"greenhouse potential" than CO2. Converting methane to carbon dioxide through combustion
is another contribution of biogas technology to the mitigation of global warming. However,
this holds true only for the case, that the material used for biogas generation would otherwise
undergo anaerobic decomposition releasing methane to the atmosphere. Methane leaking
from biogas plants without being burned contributes to the greenhouse effect! Of course,
burning biogas also releases CO2. But this, similar to the sustainable use of firewood, does
only return carbon dioxide which has been assimilated from the atmosphere by growing
plants maybe one year before. There is no net intake of carbon dioxide in the atmosphere
from biogas burning as it is the case when burning fossil fuels.