Energy, exergy, environmental and economic analysis of an agricultural waste-to-energy integrated multigeneration thermal power plant

This paper presents the energy, exergy, environmental and economic analysis of a proposed agricultural waste to-energy integrated multi-generation power plant. The proposed plant will use agro-wastes composed of selected crops and animals wastes from a farm in Rivers state, Nigeria (latitude 4.44 degrees N, longitude 7.1 degrees E). Combined anaerobic digestion and gasification was used in converting the agro-wastes to synthetic gas, and subsequently converted to electrical energy and refrigeration in an integrated multi-generation plant composed of solid oxide fuel cell stack, gas turbine, steam turbine, organic Rankine and absorption refrigeration cycles. The lower heating value of the syngas is estimated as 23.47 MJ/kg; the proposed plant had a net power of 5.226 MW, energy and exergy efficiencies of 63.62 and 58.46%, respectively. The highest exergy destruction rate was in the combustion chamber with a contribution of 15% to the overall exergy destructed. Life cycle cost of $3.753 million, breakeven point of 7.5 years and unit energy cost of $0.0109 per kWh were obtained. Environmental analysis showed specific emission of CO2 of 141.2 kg/MWh and sustainability exponent of 3.65, with exit flue gas stack temperature of 60.4 degrees C, respectively. The paper introduced energo-environmental sustainability and energo-economic sustainability exponents to holistically assess the sustainability of the proposed plants.