STUDIES ON ENERGY PRODUCTION FROM ORGANIC WASTE

Abstract

The biogas production and some biochemical parameters of anaerobic digestion under different ratios of fruit & vegetable waste (FVW) and rice hulls (RH) with cow manure were investigated in this study. The digestions were conducted in 5-liter flasks with 2.5 liter of effective volume at 35 ± 2 °C for 65 days. Variables monitored were associated to process stability, consistency and productions. The criteria for judging the success of the co-digestion systems were associated with volatile solid (VS) reduction and total methane yield. In terms of VS reductions (%), there was little difference between the various digestions. In terms of cumulative methane production, co-digestion with fruit and vegetable waste with cow manure were more effective than the digestion with cow manure slurry alone. In terms of the specific methane yield (m3 CI-14/ kg VS removed), the co-digestion. of 25% rice hulls (w/w) with cow manure gave higher value than the 25% FVW and the control digestion with cattle slurry alone. Compared with their control (cow manure slurry alone), both co-digestion with FVW gave higher cumulative biogas yield and the system with the lower concentration of RH gave higher specific methane yield. When increasing the proportion of FVW from 25% to 35% improved the methane yield from 0.254 to 0.333 m3 CI-h4/kg VS added, and caused the VS reduction to decrease slightly. Increasing the proportion of RH from 25% to 35% and P'rther from 35% to 45% in feed slurry, results that the greater reduction in methane yield and also caused a steady deterioration in both the criteria for judging digester performance. I'he overall performance of the digester was measured in terms of VS reductions. It was depressed by changing the feed concentrations (TS), lowering the pH and increasing the loading rates from its optimum values. It might also be affected by ammonia inhibition. Digester performance was restored rapidly with the addition of an alkali to increase reactor pH to around neutral values.