(584i) Methane Production from Crude Solid Residue: A Minimal Organic Waste Strategy

International environmental concerns such as Global warming have forced the scientific community to look beyond the fossil fuels to meet the energy demand and security. To match up with ever increasing energy demand, new technology must be robust and environmentally safe while using the raw material which is inexpensive and easily available. Unlike conventional substrates like coal, municipal solid waste (MSW) is renewable, abundantly available and rich in organic acids for their easy transformation into clean energy. Existing disposal strategies of MSW are not efficient for sustainable energy production processes due to the release of biogas, volatile organic compounds, and leachates that may cause public health hazards. Contrary to this, Thermophilic anaerobic digestion (TAD) of MSW provides endless possibilities for clean, renewable energy production as well as waste management. TAD has endless potential to produce methane (CH₄) and other flammable gasses which can be derivatized to other renewable biofuels viz. methanol, butanol, etc. Classic anaerobic fermentation (AF) can also be combined with TAD to materialize the concept of the release of zero-organic-waste-to-environment.

MSW is mainly constituted by Food (21% w/w) and paper wastes (28% w/w) efficient management of which has become imperative today. Thus, we have combined TAD (using thermophilic methanogenic consortia, TMC) with AF, for efficient breakdown of complex, undefined food and paper waste mixture for methane production. The feedstock for TAD is termed as “secondary waste (SW)” as it is the residual of anaerobic hydrolysis carried out using CRUDE (Conversion of Raw and Untreated Disposal into Ethanol) process. Batch TAD experiments were carried out with SW using TMC at 60 °C, pH 7.5 up to 30 days. Methane yield using SW was 95±7 L kg^–1 VS (volatile solid) after 17 days treatment (60°C; 50 rpm; pH 7.5) compared to 92±11 L kg^–1 VS with primary waste. These data confirms the potentials of SW as feedstock for methane production. After optimizing the substrate to inoculum ratio, more concentrated waste streams could be used and methane yields increased up to ~200±5 L CH₄ Kg^-1 VS. Gas chromatography confirmed the dominance of methane ( 80±6% v/v) in samples analyzed, with traces of CO₂ and H₂.