Experimental Research And Process Optimization Of Dry Fermentation Of Pig Manure And Wheat Straw Mixed Raw Materials

In order to study the utilization way of dry fermentation of pig manure under the large-scale intensive breeding mode and fully realize the resource utilization of agricultural straw waste,this paper carried out a dry fermentation experiment on biogas production with mixed raw materials of pig manure and wheat straw.Biogas slurry reactor was studied retting pretreatment,substrate concentration,inoculation amount and mixing ratio of raw materials and other factors on the pig straw mixed gas dry fermentation performance,the influence of raw material test process regularly records daily volume,pH value,the accumulative gas production and methane content data,and based on the substrate concentration,material and the quantity of dung stem than the response surface optimization test.Finally determining the best process conditions.The main conclusions are as follows:(1)Biogas slurry retting pretreatment of wheat straw can speed up the start-up stage of anaerobic fermentation.Compared with the untreated group,biogas slurry retting pretreatment of wheat straw could shorten the time of biogas fermentation to reach the peak gas production,and could reach the peak gas production on the 7th day,which was 3 days earlier than that of the untreated group.(2)Substrate concentration has a significant effect on the dry fermentation gas production of mixed raw materials.When the substrate concentration is 15%,20%and 25%,the cumulative gas production increases first and then decrease with the increase of substrate concentration.When the substrate concentration is 25%,the fermentation system has a high substrate concentration and there will be some acidification phenomenon.Within 40 days of dry fermentation of mixed raw materials,the maximum cumulative gas production was 23790.5mL when the substrate concentration was 20%,and the 20%substrate concentration was 9%and 15.6%higher than the 15%and 25%cumulative gas production respectively.(3)The inoculation amount could shorten the starting time of dry fermentation.The cumulative gas production increased first and then decreased with the increase of inoculation amount.The order of cumulative gas production of different inoculation amount from high to low was inoculation amount 30%>inoculation amount 40%>inoculation amount 20%.(4)Raw material ratio had a significant effect on dry fermentation gas production of mixed raw materials.Fermentation started faster and cumulative gas production was higher in experimental groups with raw material dung culm ratio of 3:1 and 2:1.When the ratio of feces to culms of raw materials was 3:1,the C/N was about 20,the cumulative gas production within 40 days of fermentation cycle was 29890mL,the volumetric gas production rate was 747.25mL/(L·d),and the methane content was 55.29%.(5)The response surface optimization experiment was carried out by DesignExpert software,and the variable factors were set as three factors and three levels of substrate concentration,inoculation amount and raw material ratio.The study shows that the influence of various factors on the dry fermentation of mixed raw materials for biogas production is from high to low:substrate concentration>raw material ratio>inoculum amount.Optimization analysis shows that the optimal process conditions for mixed raw material dry fermentation are substrate concentration 21.77%and inoculum amount.40%,the ratio of raw manure to straw is 3:1,and the cumulative gas production is 30046.5mL.The relative error between the verified value and the predicted value is less than 1%,indicating that the model is more reliable.