World Bank assisted National Agricultural Research Project (NARP) - University of Port Harcourt
Abstract
Shea butter extraction involves the generation of waste of
environmental concern. To help find a solution to the management of
this waste, and to search for an alternative source of energy, this
study was carried out to investigate the potential of shea waste in
generating methane gas through anaerobic digestion. At high
concentrations, volatile fatty acids produce a low pH, which may
inhibit hydrolysis, thereby affecting the stability of the anaerobic
digestion process. The influence of pH changes on process stability (or
otherwise) was also investigated. The study involved two fermentation
processes: mono-fermentation and co-fermentation involving a mix of
shea waste and cattle dung. The mono-fermentation investigations
comprised six treatments - three organic dry matter concentrations of
7%, 5% and 3%, combined with two hydraulic retention times of 30 and 60
days. The co-fermentation investigations comprised three treatments of
shea waste and cattle manure mix in proportions (by volume) of 50:50,
75:25 and 90:10. The results showed that changes in pH were a good
parameter for indicating process instability. The results also showed
that monofermentation of shea waste was not a viable option in
anaerobic digestion for biogas production, whilst only the substrate
with 50% cattle manure in the co-fermentation trials showed process
stability, producing biogas with adequate methane content