基于LCA方法的秸秆沼气发电和制备生物天然气的环境排放评价

为对比特大型沼气工程沼气资源化不同方式所带来的环境影响差异,文章运用生命周期评价方法(Life cycle assessment,LCA),对特大型秸秆沼气发电工程(日均发电量4万kWh)及生物天然气工程(日产气量1.2万方)进行环境影响评价并比较两者的环境影响及敏感性因素分析。其中包括边界划分、清单分析、各生产阶段的能耗、环境排放计算。根据计算结果显示,沼气发电时,对环境排放影响最大的是秸秆沼气发酵阶段,最敏感因素为单位干物质产气率(mL·g^-1 TS);制备生物天然气时以上两个指标分别为:沼气的提纯过程和沼气提纯技术的选择。从进行能源替代减少环境排放影响的角度来看,生物燃气替代民用散煤要优于沼气发电替代燃煤发电。

Environmental Emission Evaluation for Straw Biogas Power Generation and Bio-natural Gas Preparation Based on LCA Method

In this paper,LCA(Life Cycle Assessment)was used for the first time to evaluate the environmental impact of large-scale straw biogas power generation project(set as 40000 kWh per day)and centralized biogas supply project(set as 12,000 m 3 per day of biogas production).Their environmental impact and sensitivity factors were compared including boundary demarcation,inventory analysis,energy consumption and environmental emission calculation in each production stage.According to the calculation results,the most influential stage of biogas power generation was the straw fermentation stage,the most sensitive factor was the unit dry matter gas yield(mL·g^-1 TS).For the biological natural gas,the most influential stage was biogas purification process,and the most sensitive factor was selection of biogas purification technology.From the perspective of energy substitution to reduce the impact of environmental emissions,the substitution of biogas for domestic coal is better than that of biogas for coal-fired power generation.