The Research On Regional Differentiation Of Rural Household Biogas In China And The Ratio Of Raw Materials

China is a country with large rural population, which would pose huge challenges to rural energy security. Rural household biogas, as a way of rural biomass energy, not only can alleviate the problem of rural energy shortage, but also is effective to improve the rural ecological environment, which has significant social, economic and ecological benefits. The usage of rural household biogas digester in China increased year by year, but due to the different economic development level, population, education levels, climate conditions, the amount of fermentation raw material, etc., the rural household biogas development level are different in each region. On the basis of collecting, sorting and analyzing a large amount of data, this work studied the regional differentiation of rural household biogas in China by ArcGis10.1 which divided the development of rural household biogas into three regions. Grey correlation analysis analyzed related affecting factors and determined that raw materails and temperature are the primary factors, so combining with the actual situation in local areas to set up the experiment.The fermentation was carried out under 15℃ and 25 ℃using maize, wheat, rice straw and pig, dairy and sheep manure. Through analysis characteristics of biogas production buy raw materials, the optimal ratio of raw materials with best biogas production was combined with the three regions to ensure the best strategy to seclect the raw materials in different rural areas. Finally, the study optimized the fermentation condition for sheep/rice 9:1 under 15℃ and dairy/wheat 7:3 under 25 ℃ to promote biogas production and the sustainable development of rural household biogas. The result of this study as follow:1. Quantitatively, The development of rural household biogas in China has reached a good level, but there were also large differences among different rural areas. It showed the reduced trend from south to north and from east to west. The regional differentiation of rural household biogas showed three significant zones separated by Hebei-Henan-Hubei-Sichuan provincial boundary(abbreviated as Hebei-Sichuan boundary) and Shandong- HenanHubei-Hunan-Guangxi provincial boundary abbreviated as Shandong-Guangxi boundary). Region Ⅰ is in the north of Hebei-Sichuan provincial boundary, in which contains 13 provinces(cites) with sparsely populated, cold climate and the development level of rural household biogas is not high. Region Ⅱ is between in Hebei-Sichuan provincial boundary and Shandong-Guangxi provincial boundary, in which contains 11 provinces(cites) with large rural population, medium level of economic development, the suitable climate and high development level of rural household biogas. Region Ⅲis in the east of Shandong-Guangxi provincial boundary, in which contains 7 provinces with dense rural population, high development level of economic, suitable climate and medium development level of rural household biogas.2. Grey correlation analysis showed that temperature, raw materials, rural population, income and education level were the primary factors to affect the regional differentiation of rural household biogas in China. Among them, temperature and raw materials as the dominant factors, its correlation coefficient is 0.889 and 0.747, respectively. According to characteristics of the two dominant factors in three regions, this work selected six kinds of raw materials which include maize, wheat, rice straw and pig, dairy and sheep manure. These six raw materials are common, easy collection and abundant in rural areas.3. Except wheat straw, the biogas production of all raw materials(single or mixed) under 25 was higher than that of under℃ 15℃. The maximum biogas production was obtained sheep manure under 15℃, and then was maize straw, wheat straw, dairy manure, pig manure and rice straw. Under this fermentation condition, except pig/maize1:9 and pig/sheep 3:7, the biogas production by mixed raw materials fermentation were higher than that of by single raw materials. The cumulative biogas production of sheep /rice 9:1 was 3754 mL that was 2.46 times and 10.72 times as much as the single raw materials fermentation by sheep and rice straw under 15℃. The maximum biogas production was obtained dairy manure under 25℃, and then was maize straw, sheep manure, rice straw, pig manure and wheat straw. Under this fermentation condition, the biogas production by maize/wheat 9:1 was lower than that of by maize. Dairy /wheat7:3 achieved 16199 mL that was 1.88 times and 29.8 times as much as single raw materials fermentation by wheat straw and dairy manure under 25℃.4. The different of ratio of mixed raw material showed that the best performance of biogas production was pig/dairy 7:3, pig/wheat 1:9, pig/rice 9:1, dairy/sheep 7:3, dairy/maize 9:1, dairy/wheat 9:1, dairy/rice 9:1, sheep/maize5:5, sheep/wheat 3:7, sheep/rice 9:1, maize/wheat 9:1, maize/rice 7:3, wheat/rice 1:9, respectively under 15℃. Under the fermentation with 25℃, the optimal proportion of mixed raw material was pig/dairy 5:5,pig/sheep 9:1, pig/maize 9:1, pig/wheat 5:5, pig/rice 5:5, dairy/sheep 9:1, dairy/maize 1:9, dairy/wheat 7:3, dairy/rice 9:1, sheep/maize 1:9, sheep/wheat 7:3, sheep/rice3:7, maize/rice 9:1, wheat/rice 5:5, respectively.5. Combining the ratio of different raw materials and types and quality of raw materials in different regions, a suitable plan scheme for selecting raw materials was set. In region Ⅰ, Inner Mongolia and Xinjiang, dairy and sheep manure are abundant, which suggested using dairy/wheat 9:1 as mixed raw material first or using sheep/wheat 7:3 under 15 ℃and suggested using dairy/wheat 7:3 or dairy/sheep 9:1; In region Ⅱ, Henan and Shandong, pig manure, dairy manure, maize straw and wheat straw are abundant, which suggested using dairy/wheat 9:1 as mixed raw material first or using pig/wheat 1:9 under 15 and suggested ℃using dairy/wheat 7:3 or pig/maize 9:1; In region Ⅲ, Anhui and Jiangsu, pig manure, dairy manure, maize straw and rice straw are abundant, which suggested using dairy/rice 9:1 as mixed raw material first or using dairy/wheat 9:1 under 15 and suggested using dairy/wheat ℃7:3 or pig/dairy 5:5.6. Under 15℃, the best optimal factor combination of sheep/rice 9:1 were that pretreatment time was 10.93 d, concentration of ammonium hydroxide was 18%, and inoculum concentration was 12.84%, and expected maximum biogas yield was 7238.92 mL; Under 25℃, the best optimal factor combination of dairy/wheat7:3 were that pretreatment time was 8.23 d, concentration of ammonium hydroxide was 15.15%, and inoculum concentration was 14.37%, and expected maximum biogas yield was 19651.5 mL.