Volatile Organic Compounds Emission From Biomass Power Generation System Based On Life Cycle Assessment

The emission of Volatile Organic Compounds(VOCs)has become an important and difficult problem in air pollution control in China.Biomass open burning is one of the most important source of anthropogenic VOCs emission source.At present,the utilization of biomass energy in China is gradually changing from the traditional inefficient utilization to the advanced utilization especially power generation technology.Whether biomass power generation technology could reduce VOCs emissions is a key issue that has not yet been unanimously concluded.From the perspective of life cycle,studying the VOCs emission of advanced biomass power generation technology and pointing out the optimization direction of reducing VOCs emission will have an important reference value for the sustainable development of biomass energy industry.In this paper,three kinds of typical biomass power generation technology advanced utilization of agricultural waste were selected as the research object,including biomass direct combustion power generation system,biomass gasification power generation system and biomass and coal co-fired power generation system.The system are divided into three subprocesses including biomass feedstock supply,power plant construction and equipment operation maintenance,waste disposal based on the process-based life cycle assessment.By establishing a consistent life cycle system boundary,VOCs emission inventory calculation model and the evaluation indicator,life cycle VOCs emission of typical biomass power generation technology in China is comprehensive accounted for the first time.The environmental impact assessment is carried out based on CML 2001 model in the software Gabi5.0.Meanwhile,the alternative emission reduction method is adopted to calculate the VOCs emission reduction potential of biomass power generation technology replacing biomass inefficient combustion.The results are as follow:(1)Among the three biomass power generation technologies,the emission intensity of biomass direct combustion power generation system(5.08E-02 kg/MWh)is higher than the biomass gasification power generation system(3.42E-02 kg/MWh)and the biomass co-fired power generation system(2.07E-02 kg/MWh).The difference of VOCs emission mainly comes from the direct emission of combustion power generation and the indirect emission of wastewater treatment process.(2)Indirect VOCs emissions in biomass direct combustion,biomass gasification power generation and biomass co-fired power generation can’t be ignored with the proportion of40.94%,68.19% and 29.46%,respectively.Wastewater treatment is the main VOCs emission source of the biomass direct combustion and gasification system,while the denitration agent and catalyst used in the operation of pollution control equipment has a greater influence on the VOCs emission in biomass co-fired power generation.The implementation of water management measures and the improvement of the production efficiency of catalysts and denitration agents will effectively reduce the indirect VOCs emissions in the life-cycle system.(3)In the environmental impact assessment,the impact of Human toxicity potential(HTP)is the most important category of life cycle atmospheric VOCs emission which occupying82.18%,91.05% and 72.12% of all environmental impact in biomass direct combustion,biomass gasification power generation and biomass co-fired power generation.This is mainly due to the large HTP environmental impact caused by the usage of fertilizer.And the number fertilizer required of biomass residues used in biomass gasification power generation system is larger than others,the HTP environmental impact contributed the largest percentage of all environmental impact.(4)In the scenario analysis,the straw allocation coefficient at the planting stage of biomass agriculture has little effect on the life-cycle VOCs emission.Sensitivity analysis results show that the factors that have a greater impact on the VOCs emission intensity of the system life cycle are mostly related to the direct emissions of VOCs.Improving the power generation efficiency of the system and the coordinated emission reduction efficiency of pollution control equipment should be the main focus point for effectively reducing the life cycle VOCs emissions.The results of alternative emission reductions show that if biomass gasification power generation technology could replace biomass open burning,the national VOCs emission reduction potential is 8.99E-01 Mt,which accounts 3.16% of anthropogenic VOCs emissions.It is of great significance to complete the 10% VOCs emission reduction target of the 14 th Five-Year Plan.In conclusion,this study constructs a life cycle VOCs emission inventory of three typical biomass power generation technologies in China,and quantifies the emission reduction potential of different biomass straws in the alternative power generation VOCs at the provincial resolution by establishing a consistent life cycle system boundary.The sustainable management of biomass power generation technology and the policy of reducing pollutant emissions provide data support and scientific basis.