Study On Rural Households Biogas With Solar And Catalyst Aided Process

The environmental effects of Nansi Lake, which is known as an important waterchannel and storing lake, determines the success or failure of the East Route ofSouth-to-North Water Transfer Project. However, with an annual average totalemission of570000t, organic waste in Nansi Lake areas such as domestic andagricultural waste stacked in the open air unbendingly, which would be a seriouspollution to the soil and water environment. Therefore, only under the effective useand governance on these countryside solid waste can we meet the water qualityrequirements of the project. According to the survey, solid waste in the Nansi LakeArea mainly consists of garbage, manure and crop stalks, which are the good biogasfermentation materials. Through methane fermentation, we can not only make thesewastes transfer into resources but also help reduce solid waste pollution to the NansiLake and improve the water quality.However, as the main method in biogas project, rural households biogas has itsown defects such as immature technologies, uncentralized distribution, diversificationof materials and the short of effective management. Especially in the winter, lowtemperatures lead to the digesters zero gas production, which has seriously affectedthe enthusiasm of the farmers using biogas. In response to these issues, the studyselected the most suitable biogas fermentation materials in the Nansi Lake Area basedon the distinctive natural and cultural conditions, added the solar warming andcatalyst optimizing technologies to the traditional rural households biogasfermentation process, and finally formed a rural households biogas fermentationsystem consisted of installation, charging/discharging, heat preservation and wasteutilization. Research results are as follows:(1)Firstly, the effects of different fermentation temperature (25℃,35℃,45℃)and total solid solubility (8%,12%,16%,20%)to anaerobic digestion are compared.The results showed that the biogas microorganism’s nutritional conditions and gas production performance can be best optimized and improved under the fermentationtemperature35℃and total solid solubility16%, which can provide theoretical basisfor the successive test and parameter selection in the field biogas test.(2)After analyzed and compared the sunshine ratio and all kinds of biogasfermentation materials in the demonstration area, the study selected rabbit manure asnew biogas fermentation material. Besides, the pre-stage tests have also explored theeffects on gas production performance of rabbit manure by adding crushingpretreatment and catalysts. The results are as follows:1)after crushed pretreatment,the daily highest gas production rate of489mL and total gas production rate of2666mL were produced,65.8%and18.1%more improved respectively as comparedto untreated one;2)after added catalysts, we can shorten the starting stage from5d to3d, while a equal gas production rate was obtained. In conclusion, both crushingpretreatment and catalysts can improve the gas production performance.(3)Based on laboratory test results, field test was carried out in the demonstrationarea by adding solar warming and catalyst optimizing technologies to the traditionalrural households biogas fermentation process. The results show that the systemoperated well in winter with a daily average digester pressure of1.2kpa and dailylowest digester pressure of0.7kpa, while untreated group gained no gas. Besides,according to biogas digester heated by circulation of water heated by solar cell, threemodes of hot water cycle (one-stage cycle, multi-stage cycle, and continuouscycle)were proposed to reduce operating costs and optimize the operation. The resultsobtained showed that multi-stage cycle had a clear advantage in improving operatingefficiency, the heat transfer of which was41.57KJ, much higher than7.21KJ ofone-stage cycle and2.20KJ of continuous cycle.According to the results and feasibility verifying, we can further prove that solarwarming and catalyst biogas digestion is a economical and feasible rural householdsbiogas fermentation system which is suitable in the Nansi Lake Area.