水葫芦能源利用的生命周期环境影响评价

水葫芦厌氧发酵能源化利用已成为水葫芦处理与资源化利用的一个重要途径,以江苏省农业科学院水葫芦中试基地与常州市武进区水葫芦综合利用示范工程为案例,利用生命周期评价的方法建立水葫芦厌氧发酵产沼气工程污染物排放的清单,并对系统生命周期环境影响进行评价,以水葫芦能源利用产生1MWh电能为功能单位,评价其对环境产生的影响。研究过程将整个生命周期分成3个阶段：水葫芦厌氧发酵预处理、水葫芦厌氧发酵产沼气发电和沼液沼渣农田应用,重点考虑了3种环境影响类型：全球变暖、环境酸化和富营养化。评价结果为：各类型环境影响指数分别为2.1×10^-3、4.89×10^-2和1.98×10^-1,与能源作物发电及传统火力发电相比较,水葫芦厌氧发酵能源化利用中的CO2、SOx、NOx等污染物排放量均较低,对环境的负面影响最小,但水葫芦能源利用的生命周期效率仅为0.09,低于能源作物热电联用的技术途径（0.119）。降低水葫芦厌氧发酵能源化利用中的石化能源消耗、控制堆肥及沼液沼渣有机肥施用过程中氨挥发损失,对于提高水葫芦能源转化效率与降低环境影响指数至关重要。

Life Cycle Assessment of Electricity Production from Water Hyacinth

The electricity production from anaerobic digestion of water hyacinth is an important technology. According to a case study in the experimental station of Jiangsu Academy of Agricultural Sciences,located in Changzhou,Jiangsu,the methodology of life cycle assessment （LCA）was used to establish inventory of emission,and assess life cycle environmental impacts of electricity generation from water hyacinth based on production of 1 MWh as a functional unit. In this study,three sections were included in life cycle：（1）pretreatment of water hyacinth （including broken to pieces and solid-liquid separation）,（2）anaerobic digestion of liquid and solid residue from water hyacinth and electricity production from biogas,（3）compost of anaerobic digestion residue and utilization of digestrate and compost. The impact indices of global warming,acidification and eutrophication were 2.1×10^-3、4.89×10^-2,1.98×10^-1 respectively. Compared with the electricity production from the conventional fossil fuels and energy crop,fewer pollutants such as CO2、SOx、NOx were released from this alternative technology. However,life-cycle efficiency（0.09） of water hyacinth for producing 1 MWh power was lower than that（0.119） of the energy crop. The results suggested that the decrease of consumption of fossil energy in the processes of anaerobic digestion,and reduction of ammonia volatilization in composting and field utilization of anaerobic digestrate could significantly increase the life-cycle efficiency and decrease the environmental impact indices.