福建欠发达山区沼气运营特征及生态效应

在问卷调查获取福建欠发达山区6种典型沼气运营模式基础上,分别应用能值分析法、温室气体减排量计算及成本效益分析法,比较6种模式沼气运营系统的能值投入与产出结构、系统功能和生态效应差异。结果显示:(1)在系统结构上,集中供气型主要利用不可再生购买能值的大量投入,取得高效的生产效率和经济效益,而自建自用型则以可再生购买能值的大量投入,对自然资源利用率高,环境负荷小;在系统性能上,因净能值产出率和能值交换率高,集中供气型比自建自用型的系统可持续发展性能更佳,其中销售型尤其突出。(2)在生态效益上,以养殖为主的集中供气型和纯养殖型的温室气体减排效应非常突出,而传统种养型、特色种植型和半工半农型的减排作用不明显。(3)在政府补贴下的财务特征上,集中供气型及纯养殖型虽有高效的生态效益但不符合农户财务投资标准;相反,特色种植型与半工半农型则因系统的低生态效益而不能满足政府补贴的社会经济预期,经济预期,仅传统种养型农户完全满足社会经济角度与农户角度的投资标准。针对养殖规模化发展趋势和欠发达山区能源利用现状,对沼气工程正确运营模式的选择提出相应的建议。

Biogas operation characteristics and its ecological effects in different typical modes of the underdeveloped mountainous area in Fujian Province

Biogas is an important renewable energy in underdeveloped mountainous areas. Through questionnaire surveys of biogas users in the underdeveloped mountainous areas in Fujian Province, six typical modes of the biogas operation system were determined, namely, the biogas welfare-supply mode, commodity-producer mode, characteristic-planting mode, working and farming combination mode, traditional farming and breeding mode, and professional-breeding mode. Among these, the first two belong to the supply type, whereas the later four are the self-sufficient type. In this study, based on the emergy theory, we used the emergy indexes analysis system. The six typical modes were first studied to determine differences in their input and output composition, system performance, and system sustainable development ability. Next, by calculating the emission reduction of greenhouse gases, the emission reduction benefits of the six modes were estimated. Finally, differences in the financial investment in government subsidies for the six typical modes were determined by cost-benefit analysis. The study results showed that (1) regarding emergy input-output, supply-type biogas invested large amounts of purchased non-renewable emergy and realized high efficiency and high yields for production. Conversely, self-sufficient biogas was characterized by a high utilization rate of natural resources and low environmental load rates, with a large investment of purchased renewable emergy. In terms of system performance, the high net emergy yield ratio and emergy exchange ratio for supply-type biogas was better than that of the self-sufficient type because the later exhibited insufficient output. With the highest net emergy yield ratio and emergy exchange ratio, the commodity-producer mode had the best system performance among the six modes. (2) Regarding ecological benefits, modes including welfare mode, commodity-producer mode, and professional livestock-raising mode were prominent in the reduction of emission effects of greenhouse gases because their main income was from breeding. The modes including characteristic-planting mode, working and farming-combination mode, and traditional farming and breeding mode were not obvious in the reduction of the emission of greenhouse gases because their main development was planting. (3) From the perspective of government subsidies, the financial investment feasibility of the six modes was demonstrated at two angles, which were the farmer household financial angle and social economic angle. For the farmer household financial angle, welfare mode, commodity-producer mode, and professional-breeding mode could not satisfy the standard of farmer household financial investment. However, because of high ecological benefits from emission reduction of greenhouse gases, they conformed to the financial feasibility standard of the social economic point of view. On the other hand, the characteristic-planting mode and working and farming combination mode could not meet the financial feasibility standard of the social economic point of view, but satisfied the farmer household financial standard. Only traditional farming and breeding mode fully met the needs of social economic perspectives and the perspective of the farmer household financial standard. Based on the above research results, according to the breeding scale developmental trend and the present situation regarding energy utilizing in the underdeveloped mountainous area, some suggestions were proposed for choosing the appropriate development mode of biogas plant construction in the study area.