Biofuel production from bio-waste by biological and physical conversion processes

This research is focused on the feasibility of biofuel from water hyacinth mixed with cassava starch sediment by biological and physical conversion processes and the comparison of the gross electricity production in these processes. The biological conversion process produced biomethane by anaerobic digestion. The optimal conditions of biomethane production were a ratio of water hyacinth and cassava starch sediment at 25:75, initial pH of 7.5, thermophilic temperature (55 ± 2°C) and C/N ratio of 30. The maximum biomethane yield measured was 436.82 mL CH₄ g chemical oxygen demand (COD)^-1 and the maximum COD removal was 87.40%. The physical conversion process was bio-briquette. It was found that the ratios of water hyacinth and cassava starch sediment at 10:90, 20:80, 30:70, 40:60 and 50:50 were the best ratio of fuel properties and close to the Thai Community Product Standard, with heating values of 15.66, 15.43, 15.10, 14.88 and 14.58 MJ kg^-1, respectively. Moreover, results showed that the gross electricity production of the biological conversion process (biomethane) was 3.90 kWh and the gross electricity production of the physical conversion process (bio-briquette) from the ratios of water hyacinth and cassava starch sediment at 10:90, 20:80, 30:70, 40:60 and 50:50 were 1.52, 1.50, 1.47, 1.45 and 1.42 kWh, respectively.