沼气农业复合生态系统能值分析

以沼气为纽带的农业综合利用系统对农村和偏远地区可持续发展具有重要意义。本文基于能值流图和指标体系,构建了沼气农业复合生态系统的综合评价框架,并以国家沼气农业示范区广西恭城县为案例,分析养殖-沼气-种植"三位一体"典型沼气农业复合系统的能值投入产出量及其结构,利用能值系统结构功能指标对该系统进行经济生态多元分析,评估其投资率、产出率、环境压力以及可持续性等系统综合表现,并与国内外其他农业系统进行比较分析。系统投入结果表明,恭城县沼气农业复合系统总投入中人类经济反馈在系统中所占比例最大,可更新环境资源次之,其中又以肥料、农药和劳工与管理的投入最大;系统产出表明,目前仍以种植业和养殖业为主导,水产业相对薄弱,而新兴的沼气产业因其低耗高产的特点,发展势头良好;而能值系统结构功能指标表明该农业系统整体具有环境负荷低、产出效率高、可持续性强等优势。依照能值分析各项结果,本文对沼气农业系统优化配置和进一步推广应用提出了参考建议。

Emergy Analysis of Biogas Agricultural Complex Ecosystem

The biogas-linked agricultural comprehensive utilization system plays an important role in sustainable development in rural and remote areas.In this study,we establish an evaluation framework for biogas agricultural complex ecosystem based on the conceptual emergy flow diagram and the emergy indices adopted.We then take Gongcheng,a biogas demonstration County in Guangxi Zhuang Autonomous Region as a case study,and analyze the emergy input and yield of the typical biogas agricultural complex ecosystem "breeding-biogas-planting"and their composition structure.Finally,the emergy-based comprehensive indicators involving environmental investment,environmental yield,environmental loading and sustainability of the integrated agriculture system are calculated and compared to other agricultural systems at home and abroad.The system input results show that non-renewable resources is the largest proportion,followed by renewable resources,in which fertilizers,pesticides and labor & services are the biggest inputs.The system output results indicate that planting subsystem and breeding subsystem still dominate in the biogas system of Gongcheng County,while the aquaculture industry is relatively weak,and the newly-developed biogas industry is promisingly ideal by its low-input and high-yield advantage.And the emergy-based indicator system revealed that the overall system has its superiority with low environmental loading ratio,high environmental yield ratio and sustainability.On basis of these emergy results,recommendations are provided for the optimization and promotion of biogas agricultural ecosystem.