Research On High Effect Anaerobic Fermentation Of Wheat Straw

Biogas technology has developed since rural population increased and energy became shortage. It both provides clean biomass energy and fully utilizes the waste from livestock and agriculture. Not only fertilizer has been made by anaerobic digestion with crops and animal waste, but also economic, ecological value has promoted through biogas technology. Anaerobic digestion is a biological treatment method referring to anaerobic bacteria group decomposes organic matter including crops straw, excrement and urine, industrial and agricultural waste, and produces available energy (biogas). During the process of fermentation, influenced by many factors, such as the combination of raw material, bacteria and fungi, it is a complicated course. There are three major microorganisms: fermentation hydrolysis bacteria, hydrogen and acetic acid produced bacteria and methanogens. Special enzymes have produced in the fermentation. Their function is catalyticing, starting and accelerating the decomposition of organism. It plays an important role in the course of decomposition and transformation. Therefore, the anaerobic fermentation process is actually microbial biochemistry process. It influences significantly the circle of carbon.The key of the research is to study the relationship of gas production with pH and VFA, and to determine the optimal fermentation temperature and material ratio. This experiment was conducted at 25℃～40℃and different mixed ratios of chicken manure, cow manure, pig manure and wheat straw was used as materials, aiming at studying the pH and VFA on biogas production. The results showed that:Chicken manure and wheat straw stalk mix fermentation, producing gas time about 50d. Producing gas rate of high temperature condition is more than low temperature condition. In the fermentation process, the biogas production rate of chicken manure mixed with wheat straw 3:1 is the largest in 35℃, yield up to 467mL/d, while smallest in 25℃, only to 225mL/d. The cumulative biogas production of chicken manure mixed with wheat straw 3:1 is the highest in 40℃; yield up to 11492mL, while lowest in 25℃, only to 6227mL.Cow manure and wheat straw stalk mix fermentation, producing gas time about 39d. Producing gas rate of high temperature condition is more than low temperature condition. In the fermentation process, the biogas production rate of cow manure mixed with wheat straw 2:1 is the largest in 40℃, yield up to 815mL/d, while 1:2 is smallest in 25℃, only to 283mL/d. The cumulative biogas production of cow manure mixed with wheat straw 2:1 is the highest in 40℃; yield up to 12315mL, while 1:2 is lowest in 25℃, only to 5912mL.Pig manure and wheat straw stalk mix fermentation, producing gas time about 56d. Producing gas rate of high temperature condition is more than low temperature condition. In the fermentation process, the biogas production rate of pig manure mixed with wheat straw 3:1 is the largest in 40℃, yield up to 320mL/d, while 2:1 is smallest in 25℃, only to 147mL/d. The cumulative biogas production of pig manure mixed with wheat straw 3: 1 is the highest in 40℃; yield up to 7998mL, while 1:1 is lowest in 30℃, only to 3420mL.At the same temperature, there have some difference of biogas production between the different ratios. Chicken manure and wheat straw stalk mix fermentation, with the increase in the ratio of wheat straw, biogas production increased gradually in 25℃and 30℃, but gradually decreased in 35℃and 40℃during 50d anaerobic digestion. Cow manure and wheat straw stalk mix fermentation, with the increase in the ratio of wheat straw, biogas production increased gradually in 25℃, 30℃,35℃and 40℃during 39d anaerobic digestion. Pig manure and wheat straw stalk mix fermentation, with the increase in the ratio of wheat straw, biogas production increased gradually in 25℃and 30℃, but gradually decreased in 35℃and 40℃during 56d anaerobic digestion.There has a close relationship between the biogas production, pH and VFA. The average daily biogas production is directly proportional with pH, pH below 6.9, methane bacteria activity is restrained, biogas production is lowed; The average daily biogas production reach peak, pH is 7.0~7.4. The temperature Excessive fluctuations and can reduce methane bacteria decomposition VFA speed, cause VFA accumulation, make VFA rise. The average daily biogas production is inversely proportional with VFA.