太阳能加温和沼液回用沼气工程的生态效益评价

为综合评价新型生态清洁技术应用下的规模沼气工程的综合生态效益,该文以北京市顺义区D沼气工程(同时应用沼液循环回用技术和太阳能-地源热泵增温保温技术)为研究对象,利用能量系统图和能值评价体系,从经济效益、环境效益和可持续性3个方面对该系统进行了综合性能值分析,分析了沼液循环回用和太阳能-地源热泵增温保温清洁技术的应用对规模化沼气工程生态经济效益的影响。结果表明:太阳能-地源热泵增温保温技术在规模化沼气工程中的使用,不可再生购买资源投入减少8.80%,系统可持续性提升18.75%,有效替代了化石能源的使用,生态经济效益明显。同时,沼液循环回用技术的应用,可使地下水投入减少65%,在沼气工程周边土地无法充分消纳该沼气工程产生沼液的条件下,可节省1.77E+05美元/a的农田消纳后的剩余沼液排污处理费,环境负荷率减小68.52%,能值可持续指标由0.03增为0.38,系统自我维持能力提升。因此,沼液循环回用和太阳能-地源热泵技术的应用对该沼气工程系统的经济、环境和生态效益有很大改善作用。

Ecological effect evaluation of biogas project integrated with solar-ground source heat pump system and slurry recirculation

Abstract: Biogas engineering is an effective method for agricultural waste treatment among many methods. It can recycle on multi-layers and dispose wastes. It is an important department of sustainable agricultural development mode to achieve production capacity, and protect environment. There were many methods for evaluating the environmental effect and the sustainability of a biogas engineering such like analytic hierarchy process, cost benefit method and life cycle assessment (LCA) method. Emergy analysis method, established by Odum, could bring a new category and grade of material and energy conversion, and the conversion and quantitative analysis using the unified benchmark. The method considered many factors such like the natural resources, labor and the other factors which were usually neglected by the other methods. For sustainability assessment, biogas system provided a better way of analysis. For the aim of evaluating comprehensive ecological effect of biogas plant with the application of new ecological technologies, we chose "D" Biogas plant as the research object. And we set the traditional biogas engineering operation mode "coal-fired heating and keep warming insulation + biogas slurry discharged directly" as pattern I; "biogas slurry recycling technology" as pattern II; "solar energy-ground source heat pump heating technology" as pattern III; and both techniques used in "D" Biogas plant as pattern IV. Based on energy system diagram and the emergy-based indexes, the system were analyzed in comprehensive performance from economic production efficiency, environmental effect as well as sustainability of the ecological economic effects on biogas plant with the solar-ground source heat pump system and slurry recirculation. The results indicated that due to the application of solar-ground source heat pump system, nonrenewable purchased resources reduced by 8.80%, environmental sustainability index (ESI) increased by 18.75%. The results showed that it was an effective alternative way to the use of fossil energy, which showed obvious ecological economic benefit. At the same time, owing to the application of slurry recirculation, groundwater input fell by 65%, and the fees of treating with the disposal of raw digestate would reduce by 1.77E+05 dollar/a. So the environmental loading ratio decreased by 68.52%, environmental sustainability index (ESI) increased from 0.03 to 0.38, the system sustainability increased. Anyhow, the application of the two typical ecological technologies combined with "biogas slurry recycling in water saving and emission reduction technology" and the "solar energy-ground source heat pump heating in thermal insulation technology" in "D" Biogas plant improved greatly in economic efficiency, environmental and ecological benefits.