4. Conclusions
Rice husks (RH) derived from various rice mills in southeast
Nigeria are promising feedstock for biogas production. This study
shows that when rice husks are digested anaerobically, flammable
biogas can be produced. We report that factors such as water
dilution, initial pH, heavy metals (Zn2þ, Ni2
þ and Cu2þ), and
sources of nitrogen affected the digester performance. The best
feed to water dilution ratio was 1:6 w/v, which gave the biogas
yield of 382 mL/day. Excess water dilution discouraged bacterial
cluster formation and hence decrease in biogas production. The
best biogas yields of 357, 279 159 mL/day were reported for pH 7,
Ni2þ (100 ppm) and poultry droppings supplementation, respectively.
None of the parameters tested affected the methane content
of the biogas, although they improved the biogas yields. Thus, the
use of rice husks in biogas production is encouraged and can offer
an alternative source of energy generation especially among the
rural farmers and dwellers. This is expected to provide opportunities
for local rice millers to utilize these wastes which are
generally abandoned in dump sites. It will also bring about an
integrated system with reduced cost of operation and consequent
increased earnings while providing better aesthetics and healthier
environment.