Abstract:
Biogas can be generated from biomass in an anaerobic
digestion process and used to generate electricity
and heat as an alternative energy source to fossil
fuel-generated electricity. This study investigated
biogas generation from cattle manure dried for periods
up to 40 days. Manure samples were analysed
for gas yield using the biochemical methane production
test. The biogas volume produced by
manure samples aged for periods up to 40 days
after seeding with cattle rumen fluid was measured
as a function of time until there was no further measurable
gas production. The biogas was analysed for
methane and carbon dioxide content using a gas
chromatograph. The corresponding cumulative net
biogas yield ranged from 154 to 369 Nml/g.VS
respectively. The test results showed that an average
of 240 Nml/g.VS of biogas can be produced from
cattle manure that is less than 40 days old, with an
average methane and carbon dioxide percentage of
63% and 31% respectively. Within 3 to 4 days the
manure samples generated 80% of the final biogas
volume. The drying process was found to occur at a
constant rate per unit area, regardless of the manure thickness up to thickness of 200 mm. Biogas formation
closely followed the Gompertz equation. There
was no significant difference in the biogas production
nor biogas production rate for cattle feedlot
manure that was fresh up until aging to 40 days.
