Exergy and economic analysis of a micro-cogeneration system coupled with a biomass gasifier

Biomass serves as a solution to the energy crisis and aids in lowering greenhouse gas emissions. Residual biomass, a significant portion of total biomass, is abundant globally and can be utilised to produce energy, biofuels and biomaterials, without encroaching upon the food sector. In this paper, an energy, exergy, economic and environmental analysis of a micro-cogeneration system coupled with a wood biomass downdraft gasifier is carried out. The gasification produces syngas, mainly CO, H2 and CH4, used as fuel for internal combustion engines with cogeneration aims. Two types of wood biomass are tested and compared: briquettes from pruning and pine wood chips. The experimental investigation is carried out by instrumenting both the biomass gasifier and the internal combustion engine. The nominal electric and thermal power are 20 kWe and 40 kWth respectively. The results demonstrate the full feasibility of the energy valorisation of residual organic materials. In fact, the whole plant shows energy efficiencies of 47 % and 32 %, and exergy efficiencies of 21 % and 14 %, for the two investigated feedstocks. The economic analysis shows that the main indicators of the micro-cogeneration plant are positive with Profitability Index between 13 %, worst scenario, and 193 %, for the most favorable scenario. The GHG emissions display reductions equal to approximately 60–95 t/y, giving biomasses a decisive role in the challenge of decarbonization and reduction of GHG emissions.