Effectiveness of aerobic pretreatment of municipal solid waste for accelerating biogas generation during simulated landfilling

This study evaluates the effectiveness of aerobic pretreatment of municipal solid waste （MSW） on reducing lag phase and accelerating biogas generation. Aerobic pretreatment degree （APD） was determined on the basis of reduction in volatile solids （VS） on a wet weight basis. In this study, intermittent aeration （IA） was applied to three reactors as a main aeration mode; since a single reactor was operated under continuous aeration mode. However, the purpose of the experiment was to reduce VS content of waste, irrespective of the comparison between aeration modes. Fresh MSW was first pretreated aerobically with different aeration rates （10, 40, 60 and 85 L/min/m3） for the period of 30- 50 days, resulting in VS-loss equivalent to 20%, 27%, 38% and 53q4 on w/w basis for the wastes AI, A2, A3 and A4, respectively. The cumulative biogas production, calculated based on the modified Gompertz model were 384, 195, 353,215, and 114 L/kg VS for the wastes A0, A1, A2, A3 and A4, respectively. Untreated waste （A0） showed a long lag phase; whereas the lag phases of pretreated MSW were reduced by more than 90e/L Aerobically pretreated wastes reached stable methanogenic phase within 41 days compared to 418 days for untreated waste. The waste mass decreased by about 8% to 27% compared to untreated MSW, indicative that even more MSW could be placed in the same landfill. The study confirmed the effectiveness of aerobic pretreatment of MSW prior to landfilling on reducing lag phase and accelerating biogas generation.

Use of additive and pretreatment to control odors in municipal kitchen waste during aerobic composting

The effects of adding a bulking agent and chemically pretreating municipal kitchen waste before aerobic composting were studied using a laboratory-scale system. The system used20-L reactors and each test lasted 28 days. The objective was to decrease NH3 and H2S emissions during composting. The bulking agent, dry cornstalks, was mixed with the kitchen waste to give a mixture containing 15%（wet weight） bulking agent. A combined treatment was also conducted, in which kitchen waste mixed with the bulking agent was pretreated with ferric chloride（FeC l3）. Less leachate was produced by the composted kitchen waste mixed with bulking agent than by the kitchen waste alone, when the materials had reached the required maturity. The presence of cornstalks also caused less H2 S to be emitted, but had little impact on the amount of NH3 emitted. The FeC l3 was found to act as an effective chemical flocculant,and its presence significantly decreased the amounts of NH3 and H2S emitted. Kitchen waste mixed with cornstalks and treated with FeC l3 emitted 42% less NH3 and 76% less H2 S during composting than did pure kitchen waste.