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Studies On Dry Anaerobic Digestion Technology Of Straw

Posted on:2010-05-17Degree:MasterType:Thesis
Country:ChinaCandidate:B R GaoFull Text:PDF
GTID:2231330374995273Subject:Environmental Engineering
Abstract/Summary:PDF Full Text Request
Anaerobic biogasification of rice straw is a win-win way for resource utilization and pollution control in rural areas. Household biogas digester has an important role in rural energy development of our country. This dissertation aimed at understanding the effects of composting of rice straw and mixed anaerobic digestion on biogas production, and providing the theoretical basis for the high-efficient energy conversion of rice straw, the improvement of biogas production and the application of biogas residues.Under the laboratory conditions of35℃and total solids (TS) content of20%, the composition changes and the biodegradation rate of rice straw between treatments with composting and anaerobic digestion were studied to determine the effects of the pretreatment of rice straw and the addition of pig manure on biogas production. Results showed that composting pretreatment of rice straw didn’t enhance the biogas production and methane content for reason that this treatment decreased the hemicellulose content by more than12%, consequently reduced the TS biogas production. The decomposition rate of hemicellulose was highest during the anaerobic digestion, which was the main contributor of biogas production. Furthermore, the addition of fermented pig manure by30%(as TS%) stimulated gas production from TS and volatile solids (VS), in which the methane content also increased.In terms of beneficial microorganisms and nutritional components of pig manure, the effects of pig manure and nutrient salts addition on biogas production of rice straw were analyzed. Results showed that the increased biogas production of rice straw with pig manure addition was mainly contributed to the nutrients in pig manure, rather than beneficial microorganism. Result further found that nutrient salts could significantly enhance the methane production per gram TS and VS (151.1and164.7ml/g) of rice straw, respectively, compared with no addition treatment (120.0ml/g in TS and130.8ml/g in VS). Meanwhile, nutrient salt addition could save the cost of biogasification as much as202.9Yuan per ton of rice straw.In order to better use the biogas residue of rice straw, an indoor experiment and a pot experiment were conducted to analyze its hydrolysis conversion characteristics of carbon and nitrogen and the fertilizer use effiency, respectively. Results showed that the cumulative rate of carbon mineralization and microbial biomass carbon in soils for treatment with the biogas residue addition were higher than those in treatment with commercial organic fertilizer addition; while the rate of nitrogen mineralization was lower, which might be due to the competition for nitrogen between soil microorganisms and plants following adding biogas residues with high C/N ratio. Biogas residues addition enhanced the yield, soluble sugar content, Vc content and reduced nitrate content in the vegetable. However, the vegetable yield was lower in treatments with the biogas residue addition than that in treatment with the commercial organic fertilizer addition. This was probably due to the competition for nitrogen between soil microorganisms and plants, which consequently reduced the available nitrogen for plant biomass. Thus, appropriate amount of nitrogen should be added when biogas residues were applicated used for the base manure.
Keywords/Search Tags:Rice Straw, Dry Anaerobic Digestion, Pig Manure, Additives, Mineralization Characteristics, Pot Experiment
PDF Full Text Request
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