Household Biogas Use In China: A Study Of Region Suitability And Sustainability

With the problem of rural energy crisis and the rural environment deterioration, the development of the rural household biogas is becoming more and more important. It has been the main part of rural energy construction and the important content of the new socialist countryside construction. After many years'development of the rural household biogas of China, some industry basis and development advantages have been established. Many problems and difficulties still exist, such as rational distribution of biogas digesters, construction of biogas eco-agricultural Model, improve the efficiency of biogas, etc. Further research is needed to solve these problems. The study of household biogas region suitability and sustainability in China can not only solve the problem of development of rural household biogas in China, but also solve the rural energy deficiency and ecological environment destruction problem.According to the theory of ecology, systems engineering, energy economics, using the methods of theory and practice, qualitative analysis and quantitative analysis, literature survey and social surveys, drawing lessons from the development of rural household biogas at home and abroad, the research analyzes the problem and the strategy of household biogas in rural China from two aspects, region suitability and sustainability. The results of this research have important guidance meanings for sustainable development of household biogas in rural China. The main content of the research is composed of four parts, including twelve chapters: The first part includes chapter one. It is the starting point and the base of the research.The background, the purpose and the significance were introduced. The present research situation of rural household biogas at home and abroad was summarized. The research methods, the main innovation, the technical route and the theory of the research were introduced.The second part includes chapter two to chapter five. It is the one of the core of this research. The first, the analytical hierarchy process (AHP) was used to study the index system of household biogas regional suitability evaluation. The index system was built from climate, energy situation and social and economic factors. MATLAB6.5 was used to confirm the weights of indices. Household biogas regional suitability in Ansai county, long county and in Xixiang county were evaluated by comprehensive evaluation method. According to the analysis results, the suitability classified standard was determined. The assessment result is consistent with the actual situation. Secondly, theoretical biogas production potential estimation model was established in this study. The model was used in this study to estimation of Chinese rural household biogas production in 2007. According to the fermentation materials suitability, the development of household biogas can be divided into four different regions in rural China, optimum region, suitable region, sub-suitable region and unsuitable region. According to the results, biogas fermentation materials zoning map in rural China was made. The third, the relationship between temperature and biogas fermentation, temperature, ground temperature and digester temperature is analyzed. The index for China's rural household biogas fermentation temperature division was built. According to the temperature suitability, the development of household biogas can be divided into four different regions in rural China, optimum region, suitable region, sub-suitable region and unsuitable region. According to the results, drawing biogas fermentation temperature zoning map in rural China. At last, according to the fermentation materials and the temperature suitability, the development of household biogas can be divided into three different regions in rural China, suitable region, sub-suitable region and unsuitable region. It provides a scientific theory base and decision support for reasonable layout of the household biogas.The third part includes chapter six to chapter nine. It is the one of the core of this research. The first, the status of biogas production in Baoji city in Shaanxi Province is stated in this paper. And the operational structure and benefit of three typical eco-agricultural models are analyzed. The three typical models include"biogas digester– bio-toilet - stable - vegetables (fruits, food)","mulberry tree - silkworm– agaricus bisporus - stable - biogas digester"",large-scale biogas engineering of breeding farms of Qinchuan cattle". In addition, the developing countermeasures of biogas ecological agriculture were put forward. Secondly, in order to quantitatively assess the structure, function and benefit of biogas eco-agricultural models, based on the studies of eco-agricultural model evaluation index system, 17 indicators were selected to construct a comprehensive evaluation index system of biogas eco-agricultural model, multilevel averaging weight method was used to confirm the weights of indices, assessment model was constructed by comprehensive evaluation method. We also verified the model with the data of two typical biogas eco-agricultural models (Longxian " biogas digester– toilet - stable - vegetables, fruits, food)" courtyard ecological agriculture model and Qianyang County"mulberry tree - silkworm– agaricus bisporus - stable - biogas digester"eco-agricultural model)in Baoji City, Shanxi Province, and the assessment results were consistent with the actual situation. It is showed that the evaluation index system and the model have adaptability. The third, the objective and quantitative assessment of environmental and economic benefits in the life-cycle of 8 m3 biogas digester was carried out by life-cycle assessment and life-cycle cost methods. The results show that 8 m3 household biogas digester (functional unit is 400 m3 biogas) on the environmental impact load of 1.6418, the main potential environmental factor influence orders are eutrophication, global warming and acidification. Life-cycle cost, net profit per year and cost pay back period values are 3082 Yuan, 835 Yuan, 3.69 years, respectively. Gave the countermeasures and suggestions for reduce environmental emissions, enhance economic efficiency in household biogas industry, and can be of benefit to rural household biogas sustainable development in China. At last, we describe the current status and discuss potential development trends of rural biogas in China in this paper from five aspects, biogas fermentation materials, fermentation technology, development model, comprehensive utilization and management. Straw will replace animal manure as the main raw material of biogas. Dry methane fermentation will become an important method in the large scale production of biogas from agricultural wastes. The central supply pattern introduces a market economy to the village biogas industry. It is with broad market and great potential to produce commercial fertilizer and using biogas to generate electricity. The follow-up services and management expert system of biogas digesters, is a key question of rural household biogas development. The research will promote the sustainable development of household biogas in rural China.The fourth part includes chapter ten. It summarizes the main contents and gives the prospects of the research.