Biogas production from blends of powdered rice husk with some agro-industrial wastes

Abstract

Biogas production from powdered rice husk (RH) and blends of rice husk with other agro-industrial wastes was investigated. The RH was blended with waste streams such as brewer’s spent grain (SG), cassava waste water (CW) and carbonated soft drink sludge (SL). These wastes were blended in the ratios of SG: RH (1:1), CW: RH (1:2.3) and SL: RH (1: 1.5). The daily mean flammable gas production was 5.5l.When blended with SG or CW, flammable biogas production increased to 18.8 and 19.5l respectively while an increase of 7.7l mean gas yield was obtained for SL: RH combination. There was significant increase in biogas yield at 95% confidence level for all the blends. Flammable gas was obtained from RH alone from the 16th day of the anaerobic digestion process while, SG: RH combination exhibited the shortest lag time of 2 days (CW: RH and SL: RH had lag days of 6 and 10 respectively). Gas analysis from SG: RH blend shows, methane (70.6%), CO2 (23.3%), CO (6.3%) and H2S (2.1%), CW: RH contained methane (77.8%), CO2 (19.5%), CO (2.1%), H2S (0.6%) while SL: RH combination, the values are, methane (73.5%), CO2 (18.9%), CO (7.5%), H2S (0.6%). The overall results indicated fastest onset of flammable biogas production from SG: RH combination. In addition, the relatively low flammable biogas production of RH was shown to be significantly enhanced when it was combined with SG or CW in definite ratios.