A
biomass energy utilization project (Corn stalk→Cattle→Cattle
dung→Biogas digester→Biogas/Digester residues→Soil) was conducted
in a typical temperate agro-village of China from 2005 to 2010. The
present study focused on two key approaches of the ecological loop:
(1) increasing corn stalk use efficiency by improving anaerobic
fermentation technology; and (2)
enhancing biogasproductivity by optimizing fermentation
conditions. Our results showed
that crude proteinand fat of corn stalks significantly
increased, while crude fiber content and pH decreased considerably
during anaerobic fermentation. The cattle digestion rate, forage
consumption and increases in cattle weight were higher in cattle
fed fermented corn stalks than in those fed non-fermented corn
stalks. The rate of biogas productionwas higher (78.4%) by using cattle dung as a
substrate than using crop residues. Heat preservation measures
effectively enhanced the biogas production rate (12.3%). In 2005,
only two cattle were fed in this village, with only 1.1% corn stalk
utilized as forage. No more than three biogas digesters existed,
and the proportion of biogas energy used in total household fuel
was only 1.7%. At the end of the 5-year experiment, the number of
cattle capita reached 169 with 78.9% corn stalk used as forage.
Biogas digesters increased to 130, and the proportion of biogas
energy used in total household fuel was up to 42.3%. A significant
positive correlation was noted between the increasing rate of
farmers’ incomes and the proportion of corn stalks used as forage.
Available nutrients were higher in fermented cattle dung than in
fresh cattle dung. Our findings clearly suggest that anaerobic
fermentation technology is important in enhancing crop residue use
efficiency, biogas productivity and soil fertility. Fermentation
technology may help reduce the use
of fossil fuelsand improve the environment in rural
areas.