Environmental Engineering Reference
In-Depth Information
Fig. 2.2
Usable biomass potential for biogas production in Germany
variety of crop as biomass. Forage crops are thus mostly suitable for biogas produc-
tion because of small harvesting periods (Weinberg et al.
2003
).
The crop residues and the crops themselves are stored via a process called ensil-
ing. In the biochemical process of ensiling, the soluble carbohydrates in plant crops
are converted into butyrate, acetate, lactic acid and propionate. The production of
these organic compounds inhibits the growth of contagious pathogens by lowering
the pH to 3-4 (Banemann and Nelles
2009
). However one downfall of energy losses
of up to 8-20 % accompanies the process of ensiling. To minimize the energy loss
by biomass degradation, the energy crops are put in silos and wrapped in plastic
wraps (Weiland
2006
).
4
Second Generation Biofuels
4.1
Bio Alcohols
Alcohol is a very important source of energy because it can be produced chemically
and biologically. Alcohol produced by the traditional chemical methods is now be-
ing replaced by the bio alcohols produced by microorganisms and enzymes using
renewable energy sources (Weber et al.
2010
). Out of all the other biofuels, bio
alcohol fuels proposes the most verified and attainable substitute for the gasoline,
which is three fourth of on-road fuel practice, over one-half of all transportation
energy use especially in the USA (Weber et al.
2010
). Main bio alcohols used for
the production of energy are methanol, ethanol, propanol and butanol. The main
reason why bio alcohol based fuels are essential is their advantage to hold a high
