Kinetic studies of biomethanation by using kitchen waste in a semi-batch reactor

Abstract

A study of the biogas production of kitchen waste (KW) and mixture of kitchen waste with cow dung (KW: CD) in the ratio 1:1 was performed. The two variants were charged into two separate 500 ml biodigesters. 25% (i.e. 125 ml) headspace was left and the rest 75% (i.e. 375 ml) was the working space. 6% substrate volume was mixed with 375 ml water. They were subjected to anaerobic digestion for a retention period of 45-day at around 37 0C. Results obtained showed that only kitchen waste system (KW) had a cumulative gas yield of 5.69 dm3/kg of slurry and the biogas production started on the 5th day even though the biogas production went down drastically. Significant biogas production again resumed after around 7 days and continued till the 34th day and finally stopped till the end of retention period. On the other hand, mixing the cow dung with kitchen waste increased the cumulative gas yield to 10.35 dm3/kg of slurry, which is almost 100% increase. The gas production for this sample (KW:CD) was first observed on the 6thday and it sustained throughout the retention period. Biogas production for the (KW:CD) system was much higher throughout the retention period in comparison to the only kitchen waste (PW) system. The study showed that kitchen waste which can be found everywhere and is either burnt off or thrown away as both domestic and industrial waste, degrades the environment, would be a very good raw material for biogas production. It also indicates that mixing kitchen waste with cow dung or any other animal waste will give sustained gas production throughout the digestion period of the waste. If biogas is produced from kitchen waste, it can be seen with a positive outlook to solutions of environmental issues like this.