Ecological Thermodynamic Calculation And Assessment Of Biomass Gasification System

Our society is facing with serious problems of energy lacking,climate change and environmental pollution.As one of important renewable energy,biomass has received great attention and highlight in the world.As one of the foremost ways of utilizing biomass,gasification converts biomass into gaseous fuels by means of partial oxidation of the biomass at high temperatures,with the production of methanol or hydrogen,each of which have the potential as fuels in the future.However,it would cause nonrenewable energy cost and greenhouse emissions during the whole process of biomass gasification.It is profound to assess the environmental and ecological effects of biomass gasification with the rapid development of biomass.Based on the ecological thermodynamical method,a 20MW biomass gasification power generation system is studied.In this study,system model and input-output list of the biomass gasification system throughout its lifetime including agricultural process and transportation of biomass,pants'building,equipment input and waste treatment are established,and then ecological thermodynamical calculation about greenhouse gas emissions,fossil energy consumption,exergy and water footprint are carried out:?1?Systems accounting on nonrenewable energy cost and greenhouse gas emissions of biomass gasification system is conducted in this research.The renewability and greenhouse gas emission intensity are also calculated as 0.07MJ/MJ and 0.12kgCO₂-eq/MJ,respectively.Compared with conventional coal-fired power plants and other biomass utilization systems,results show that the biomass gasification system is renewable but doesn't show a good performance on greenhouse gas reduction.?2?Based on exergy theory,comprehensive ecological effects of biomass gasification system are evaluated.Comparing to biomass direct combustion and biomass pyrolysis system,results indicate that exergy of the products from three systems studied is higher than purchased exergy,which shows good ecological benefits.However,the stability of their development is easily influenced by external factors as their over-dependence on foreign resources.Besides,the utilization degree of renewable energy in biomass gasification system is higher than the other two systems,which means a better performance of sustainability.?3?Systems accounting on water footprint of biomass gasification system is conducted with a comparison with biomass direct combustion and biomass pyrolysis system.Water footprint of biomass gasification system is mainly from the direct water cost during agriculture process and industrial process.Compared with biomass direction combustion and pyrolysis,biomass gasification system performs not so well in water saving.