BIOGAS PRODUCTION POTENTIAL AND THE SUBSTRATES CONVERSION RATE OF KHAT WASTE AND COW DUNG

Abstract

Anaerobic digestion technology is one of the most environmentally friendly waste-to-energy processes. Khat waste has polluted the environment and created health problems for the community. This study was carried out to characterize the physicochemical properties, biomethane production potential, and substrate conversion with laboratory-scale anaerobic mono-digestion and co-digestion of Khat Waste and Cow Dung using sheep rumen fluid as inoculum. The Khat waste was collected from Dire Dawa city administration in different areas and Cow dung was collected from Southern Nation Nationality People’s Region Gamo zone Arbaminch town. The Physico-chemical parameters of feedstocks such as Total Solid, Volatile Solid, Carbon, Hydrogen, Nitrogen, Oxygen, and Lignocellulosic of the raw sample were determined using the standard method. Anaerobic bench-scale batch reactor used seven samples each sample was repeated three times. Potassium Hydroxide (KOH) was used as a pretreatment reagent. The daily methane production was measured using the water displacement method which continued until the gas production was insignificant. The hydraulic retention time was 27 days at 35±3oC. The result shows that the C/N ratios of Khat waste and Cow dung were 20.99 and 22.22, respectively. The maximum production of methane can be generated from the digester, with the higher proportion of Khat waste in the T-5(66.67% Khat Waste:33.33% Cow Dung) ratio, was 6069±153.39 ml, and the lowest production, in the T-7(0% Khat Waste:100% Cow Dung) ratio was 3048±75.9 ml with cow dung substrate only. The conversion rates of cellulose and hemicellulose components from Khat waste were 44.4 and 47.2%, respectively. Of the total amount of cellulose and hemicellulose components from Cow dung used, 51.7 and 47.7% were converted to methane, respectively. The result can be a demonstration for khat waste and cow dung in cities/towns of developing countries, like Dire Dawa city administration, to use anaerobic treatment and supplement energy option and also advantage for future researchers working in similar work.