基于能值的沼气农业生态系统可持续发展水平综合评价——以恭城县为例

近年来,农村传统的粗放式发展模式对资源和环境造成了巨大的压力,严重阻碍农村的可持续发展进程,为此,国家在农村大力推行以沼气为重点的农村生态建设,加快建立以沼气为纽带的可持续农业发展模式。因此,对沼气农业生态系统的可持续性进行评价对农村能源生态建设和沼气工程的推广具有重要意义。本文选取广西恭城瑶族自治县沼气农业生态系统作为案例,将种植业、养殖业和生态旅游业作为一个复合生态系统,应用能值分析方法将不同能质的能量折算为统一的能值单位,分析了复合农业生态经济系统的可持续发展现状,通过能值分析发现案例区域恭城县沼气农业生态系统具有以下特点:(1)与传统农业生态系统相比,有机肥所占比重较大;(2)水果生产为当地主导产业,生态旅游业有了初步发展;(3)农业的快速发展使人民具有较高物质生活水平;(4)科技水平相对落后,生产率低;(5)沼气替代传统能源,大大减小了环境压力。通过对恭城县农业生态系统发展中的问题进行识别,提出相应政策建议,能够对其未来的发展模式提供参考,对沼气农业生态系统的推广具有重要意义。

Emergy evaluation for sustainability of Biogas-linked agriculture ecosystem: a case study of Gongcheng county

Nowadays, traditional extensive agricultural economic growth mode has exerted great pressure on natural resources and the environment and hindered the sustainable development of rural areas. In this context, the government attempts to promote biogas-based agricultural ecosystem construction and establish a biogas-linked agricultural ecosystem to solve the problems encountered. As the demonstration area, Gongcheng has already formed a "Three in One" biogas-linked agricultural ecosystem, and the industrial chain is expanding to include tourism and manufacturing. Thus, it is of great importance to evaluate the sustainability of Gongcheng biogas-linked agricultural system. The aim of this study is to assess the efficiency and sustainability of the biogas-linked agricultural ecosystem in Gongcheng, Guangxi through emergy-based ecological analysis. The emergy-based indicators of this integrated system are calculated and compared with those of other agro-ecosystems in China. Results show: (1) The total emergy input of biogas-linked agro-ecosystem in 2009 was 2.86×10²¹ sej, in which the proportions of renewable subsidiary resources from economy, nonrenewable resources from free environment, nonrenewable purchases and renewable resources from free environment were 34.8%, 10.3%, 45.5%, 9.33%, respectively; (2) The proportions of cropping, breeding, forestry and eco-tourism of the total emergy output were 45.45%, 23.22%, 4.09%, and 18.29%, respectively; (3)The emergy used per person in 2009 in Gongcheng biogas-linked agro-ecosystem was 1.13×10¹⁶sej/person, much higher than 8.31×10¹⁵sej/person of the whole China in 2000 and 1.28×10¹⁵ sej/person of Jiangxi province in 2005; (4) The emergy intensity of Gongcheng agro-ecosystem in 2009 was 1.33×10¹² sej/m², much higher than 8.99×10¹¹ sej/m² of China in 2000 and 2.44×10¹¹ sej/m² of Jiangxi province in 2005; (5) The emergy yield ratio of Gongcheng biogas-linked agro-ecosystem was 0.94, lower than 2.08 of China in 2000, 4.17 of Jiangsu province in 2001 and 1.25 of Guangdong province in 2003; (6) Emergy load ratio was 1.27 in Gongcheng in 2009, which was lower than the average level of 2.72 in China in the year of 2000; (7) Emergy sustainable index in 2009 was 0.74, which was at the same level with those of China and Guangdong province. By comparison, the biogas-linked agricultural ecosystem is proved to be sustainable with less pressure on the environment. It has the following advantages over the traditional agricultural ecosystems: (1) The organic fertilizer accounts for a larger proportion in biogas-linked agro-ecosystem; (2) Fruit industry has become the leading industry fueling local economic development and ecotourism begins to take off; (3) Rapid agricultural development brings about relatively higher living standards; (4) Science and technology as well as the productivity remain at a relatively backward level; (5) Biogas replaces the role of traditional energy and greatly relieves environmental pressure. According to the results obtained, in order to maintain the existing advantages and take pressures off natural resources and the environment, measures to promote the development of biogas-linked agro-ecosystem are then proposed. Therefore, this study is meaningful in guiding the development of future biogas-linked agricultural ecosystem in Gongcheng.