| With the development of China's industrial and agricultural production and the expansion of urban scale and the continuous improvement of people's living standards,the demand quantity and consumption quantity for energy continue to increase,large-scale and intensive farms,and sewage treatment plants continue to increase,therefore,the livestock and poultry manure and sewage sludge emissions also will increase.That leads to energy shortages on the one hand and environmental pollution on the other hand.Anaerobic digestion of biological organic wastes can not only solves the environmental problems,but also get the clean energy of methane,and the biogas residue and biogas slurry produced from fermentation both are good organic fertilizer.In order to understand the relationship between the properties of macromolecular organic compounds and cumulative methane production of anaerobic digestion materials,the methane-producing differences among methyl cellulose,peptone,soluble starch,and lignin were studied by anaerobic digestion at medium temperature(45± 1)?.In order to understand the effect of fermentation temperature on anaerobic digestion of different organic wastes,the methane-producing differences between chicken manure,pig manure,and cow dung were studied by anaerobic digestion at both medium temperatures(45±1)? and high temperature(55±1)?.Single organic waste,mixture of two organic wastes,and mixture of three organic wastes of chicken manure,pig manure,cow dung,and sludge were studied by anaerobic digestion at high temperature(55±1)? to understand the effect of different raw materials and their ratio on methane production.Through the results analysis,the main conclusions were as following:(1)The cumulative methane production of the four organic compounds was peptone>methylcellulose>lignin>soluble starch and was 98.6,85.5,75.8,49.8 mL CH4 · g-1 TS Respectively.The total solid content(TS)of the four organic compounds decreased to varying degrees and the decrease was positively correlated with the cumulative methane production after the anaerobic digestion.The concentration of volatile fatty acids(VFA)increased and the NH4+-N concentration decreased in the fermentation liquid and soluble starch and that led to the decrease of pH value in the treatments of methyl cellulose,lignin,and soluble starch.Especially the soluble starch treatment,its pH value of fermentation liquid was 4.70 after anaerobic digestion.Extreme acidification of fermentation liquid suppressed the anaerobic digestion and resulted in the shortest time of gas production and the least cumulative methane production in the soluble starch treatment.The volatile fatty acids(VFA),NH4+-N,and pH value all increased in the fermentation liquid,but the cumulative methane production was the highest in the peptone treatment.it can be conluded that the inhibition of extreme acidification to methane production in the soluble starch treatment is much stronger than that of alkalization to methane production in the peptone treatment.(2)The amount of methane production of chicken manure,pig manure,and cow dung at high temperature was significantly higher than that at medium temperature.The accumulated methane production per unit of TS was pig manure>chicken manure>cow dung at both high temperature and medium temperature.The degradation rate of TS was positively correlated with the cumulative methane production at the same temperature.The contents of NH4+-N and VFA in the fermentation liquid broth increased in the treatments of the 3 livestock and poultry manures after fermentation and the increasing rate were higher at medium temperature than that at high temperature,but the amount of methane production was lower at medium temperature than that at high temperature.The increasing rates of NH4+-N and VFA in fermentation liquid were both the highest,but the accumulated methane production was the lowest at the same temperature in cow dung treatment.It indicated that the high concentrations of NH4+-N and VFA inhibited the production of methane.The pH values of fermentation liquid did not change much after fermentation in the 3 treatments of livestock and poultry manures.The C/N was decreased at different fermentation temperatures after fermentation in the 3 treatments of livestock and poultry manures and the reduction rate of C/N was positively correlated with the cumulative methane production at the medium temperature.(3)The cumulative methane production of the 3 livestock and poultry manures and their mixtures was chicken manure + pig manure>pig manure>chicken manure>chicken manure + cow dung>pig manure+ cow dung>cow dung>chicken manure + pig manure + cow dung.It indicated that chicken manure mixed with pig manure was advantageous to increase methane production of both,adding chicken manure or pig manure into cow dung increased its methane production,but adding cow dung into chicken manure or pig manure decreased methane production of both,and the methane production of mixture of the 3 livestock and poultry manures was the lowest.Sludge mixed with each one of the 3 livestock and poultry manures increased its methane production and the cumulative methane production was pig manure +sludge>chicken manure + sludge>cattle dung + sludge>sludge.Sludge mixed with any two of the 3 livestock and poultry manures also increased its methane production and the promoting effect was much bigger than that of sludge mixed with 1 livestock and poultry manure.It showed that adding livestock and poultry manure into sludge promoted its digestion and methane production. |
PDF Full Text Request