Comprehensive Evaluation Of Anaerobic Digestion-gasification Coupled Power Generation System Based On Life Cycle Assessment Method

The annual production of biomass represented by straw in China is huge,and its rational utilization plays a positive role in alleviating energy scarcity and reducing environmental pressure.The common methods of straw energy utilization include direct combustion,anaerobic digestion,gasification,solid molding fuel and liquid fuel.To further improve the efficiency of straw energy utilization,the anaerobic digestiongasification coupled technology receives increasing attention in recent years.This study evaluated the anaerobic digestion-gasification coupled power generation system from the perspective of environment,economy and energy.It provided a reference for seeking a reasonable utilization way.The main contents and conclusions are as follows.(1)The traditional biomass energization technologies were summarized.The current research of biomass anaerobic digestion-gasification coupled technologies and the evaluation methods of biomass energization were reviewed.Based on the comprehensive evaluation methods of life cycle,static analysis and cumulative energy analysis,this paper provided a route for comparison between biomass anaerobic digestion-gasification coupled power generation technology and traditional biomass energization technology.(2)According to the applications of various biomass energization technologies,typical engineering cases based on direct combustion power generation system,anaerobic digestion power generation system,gasification power generation system,and anaerobic digestion-gasification coupled power generation system were constructed.System boundaries,functional units,and basic assumptions were specified in detail to provide reliable supports for the subsequent comprehensive evaluation.(3)Relying on the lifecycle assessment software SimaPro,the comprehensive evaluation method of biomass energization was applied to four typical power generation system cases.The main conclusions were as follows: a.In terms of environmental benefits,the main environmental impacts were concentrated in the power generation phase.According to the endpoint damage categories of human health,the ecological quality,the climate change and the resources,it was evident that the anaerobic digestion-gasification coupled power generation system was better than the others.b.In terms of economic benefits,gasification power generation system had the greatest economic advantage,followed by anaerobic digestion-gasification coupled power generation system.Raw material prices accounted for the largest share of production costs.The lowest selling price was most affected by power generation,followed by the price of raw materials.In terms of energy consumption,anaerobic digestion-gasification coupled power generation system had the lowest energy consumption,which was-14.0 GJ(based on the cumulative energy consumption of 1 t straw).In each case,the power generation and energy recovery were the main contributors to cumulative energy demand.This study showed that anaerobic digestion-gasification coupled power generation system was superior in protecting the environment and reducing energy consumption.Further economic benefit evaluation also provided a reference for biomass power generation system.