Effect of Leachate Circulation on Biogas Production from Market Waste and Rice Straw

Abstract

The production of biogas from animal waste has been studied and technologies are beingused for the management of animal wastes as well as for the generation of renewable energy.The organic fraction of the market garbage as well as agricultural wastes (organic fraction)can properly be affected for the biogas production through proper physiochemical treatmentsof raw materials.

In this study it was attempted to find out the effect of leachate circulation on biogasproduction from reactors fed with organic fraction of market waste (MW) and rice straw(RS).The laboratory reactor model (20 L) was fabricated using plastic cans. The provisions atthe bottom and top of the reactor were made to circulate the leachate produced duringanaerobic digestion. The leachate circulation was performed using a peristaltic pump. Thereactor was fed with MW & RS (< 1mm particle size) in the ratio of 1:3. The total rawmaterials fed to the digester were 3 kg (dry matter) and total solid level was adjusted to 20%by adding water. Before starting the experiment inoculums (digested material from a biogasdigester running biogas) was added. The experiment was conducted ~ 3 months under once aday circulation. Biogas production, temperature and pressure were measured daily. pH &Chemical Oxygen Demand of leachate were determined once a week. At the middle of theexperiment CH4 was also determined. The C: N ratio of the mixture of raw materials fed forthe study was ~25:1. The consistence biogas production was noted after one week of start ofstudy. Biogas production rate was gradually increased up to ~45 days and it was decreased atthe end of three months period. The total biogas production was ~36 m3/kg and its methanecontent was ~50%. At the beginning of the study pH was neutral and it was reduced to ~4during 6 weeks. Then it has gradually increased due to produced volatile fatty acid bymethanogenic bacteria. COD determined in leachate during the study period graduallydecreased with the increased biogas production. It was concluded that the biogas productionwith leachate circulation was very high than without leachate circulation based on theprevious trials.