The Optimization Of Fermentation Process Of Manure And Straw By Response Surface Methodology

Anaerobic fermentation, anaerobic digestion, is the process of applying decompositionby a variety of anaerobic bacteria to eventually produce biogas, a mixed gas such as methaneand carbon dioxide from organic matter (manure of cattle and fowl, crop straw, etc.) underoxygen-free conditions.The anaerobic fermentation convert straw and manure into biogas, andmake full use of biomass resources, at the same time kill most of bacteria and parasitic ovumin the feces.There are many report related on the effect of single factor on gas production inratio of raw materials of mixed fermentation, such as the effect of total solids concentration(TS) and mixed anaerobic digestion features of the mixture of animal manure and crop stalksby a certain percentage on anaerobic fermentation gas production, the effect of temperature ongas production characteristics of anaerobic fermentation. However, a few researches of theinteraction of multiple factors and influence degree of various factors on gas production havebeen reported.Under the condition of35℃, the effects of pig dung-cow dung mixing ratio,manure-corn straw ratio, TS and combinations of different factors on the biogas yield ofanaerobic fermentation were studied, with pig dung and cow dung, corn straw, wheat straw,rice straw as raw materials for fermentation. Comparing degree of influence of three factors ofthe ratio of pig dung and cow dung, the proportion of manure mixed with straw and TS on thecumulative gas production, we aimed at discussing the optimal technological conditions ofanaerobic fermentation of mixed raw materials of pig manure, cow manure and corn (wheat orrice) straw. Methods: The effects of mature (pig dung and cow dung) ratio, manure-straw (thetotal amount of pig manure and cow dung with straw) ratio and TS on anaerobic fermentationwere investigated by single factor experiments. Based on the above works, the Box-Behnkendesign experiments and response surface methodology (RSM) were used in the optimizationof anaerobic fermentation technology. Conclusion: ratio of raw materials and total solid weredeterminants of gas yield and production rate of anaerobic fermentation of mixed rawmaterials of pig manure, cow manure and crop stalks. Results:(1) Results of fermentation experiments of mixed materials of pig dung, cow dung andcorn straw Results of single factor experiments: in five different manure mixture ratio, threedifferent manure-stalks ratio and five different TS, respectively, the value of1:1,1.86:1,11%obtained the highest cumulative gas production.Results of optimization experiments: experimental conditions of manure ratio1.06:1,manure and corn straw with a ratio2.94:1and TS10.68%were optimal and the cumulativebiogas yield was17275mL. The degree of influence of various factors on the cumulative gasproduction as follows: manure-straw ratio>TS> manure ratio.(2) Results of fermentation experiments of mixed materials of pig dung, cow dung andwheat strawResults of single factor experiments: the cumulative gas yield of anaerobic digestionwere the highest when the value were1:1,1.86:1, and11%among five different manuremixture ratio, three different manure-stalks ratio and five different TS, respectively.Results of optimization experiments: experimental conditions of pig dung-cow dungratio1.08:1, feces and wheat straw with a ratio2.11:1and TS10.08%were optimal and thecumulative biogas yield was16166mL. The degree of influence of various factors on thecumulative gas production as follows: TS>manure-straw ratio>pig dung-cow dung ratio.(3) Results of fermentation experiments of mixed materials of pig dung, cow dung andrice strawResults of single factor experiments: in five different manure mixture ratio, threedifferent manure-stalks ratio and five different TS, respectively, the value of1:1,1.86:1,11%obtained the highest cumulative gas production.Results of optimization experiments: experimental conditions of manure ratio1.16:1,manure and corn straw with a ratio2.23:1and TS9.84%were optimal and the cumulativebiogas yield was14708mL. The degree of influence of various factors on the cumulative gasproduction as follows: TS>manure-straw ratio>pig dung-cow dung ratio.