Effect Of Pretreatment On Biogas Production Of Wheat Straw

China is a large agricultural country, large amounts of crop straw has been product every year, the straw has many species, and is widely distributed, which makes it difficult to straw utilization.In recent years, translating the crop residues for clean energy by way of anaerobic biological biogas in rural areas is an important measure, which is also the work of renovating the rural environment, in line with the agricultural cycle and the requirements of sustainable development. Wheat is the third largest food crop in China, in2010, China’s wheat achieve to24.257million hectares, with an annual output1.5million tons of wheat straw, according to collected coefficient of0.7, the annual collection of straw can be105million tons. Wood fiber is the main organic components of the straw, lignin and crystalline fibers undered anaerobic conditions is difficult to anaerobic decomposition, which is the main factors to affect the straw anaerobic biological biogas production. By. pretreatment straw wood fiber to damage its structure, improve its anaerobic biodegradability in Pretreatment we do some research, as follows:Using straw as the raw materials, the three different kinds of post-harvest straw are dealed with different drying process, then we obtain fresh、air-dried for10days and drying sample to study the different drying process on straw nutrients.and in the same fermentation conditions carrying on anaerobic fermentation, by different biogas production to work out the effect on the drying process to improve the straw gas characteristics of the most favorable process. The results showed that different drying process on wheat straw is not conducive to the improvement of the wheat straw anaerobic fermentation gas production, fresh have the highest gas, as followed by dried air-dried for10is the worst; although air-dried for10days is not conducive to straw anaerobic fermentation biogas. there is a certain impact on methane content,increased by5.23%; the cellulose decline by24.06～47.70%, and the hemicellulose decline by19.91～59.07%, the different kinds of the straw divergence is not remarkable, the relative content of lignin increased from38.28-127.22%. Long-term storage of crop straw is very important for biogas plant while pretreatment is always used to improve biogas production of crop straw. Feasibility of integrating storage with pretreatment of baling wheat straw was studied. Changes of physico-chemical properties, biogas productivity of wheat straw obtained before and after120days storage were analyzed. The results showed that it was feasible to directly bale wheat straw for storage (control) and storage treatment had little effect on physico-chemical properties, structure and biogas productivity of wheat straw. After120day’s storage, biogas potential of surface wheat straw of pile was decreased by7.40%. Integrating NaOH pretreatment with straw storage was good for biogas production of wheat straw and total solid (TS) biogas yield was increased by7.02%～8.31%(compared to that of no storage wheat straw) and5.68%～16.96%(compared to that of storage without alkaline pretreatment). Storage with urea treatment was adverse to biogas production of wheat straw and content of cellulose and hemicellulose of wheat straw were decreased by18.25%～27.22%and5.31%～16.15%and TS biogas yield was decreased by2.80%～7.71%after120day’s storage. Exposing wheat straw to the air during storage process was adverse to observing organic matter and biogas utilization of wheat straw, but the influence was very slight and TS biogas yield of wheat straw obtained from pile surface of control and urea treatment were decreased by7.40%and4.25%, respectively.Composting pretreatment can destruct the straw wood fiber structure, improve the anaerobic bio-gas production rate and gas production, but compost with long time will cause significant loss of organic matter, which will affect gas production. An experiment is conduct wheat straw on compost pretreatment, using varying degrees of compost wheat straw as raw materials for anaerobic bio-gas production potential experiments.which shows that compost temperature rose to30℃after6.8h. then in13.5h,19.5h,23.Oh,44.8h reached40℃,50℃,55℃and60℃, the highest temperature of70℃, followed by a slow decline: after compost pretreatment, with the extension of pretreatment time, the organic content of the straw gradually decreased, nitrogen content first decreased and then increased, cellulose and hemicellulose content first increased and then decreased,the lignin content first decreased and then increased, the divergence of the different treat are not remarkable (P>0.05):after the anaerobic biogas, the TS gas production of30℃、40℃、50℃、up to 55℃2days、 up to55℃5days、up to55℃9days are all decline4.16%～21.72%compare to CK,it indicates that the short and long time of the compost time have no advantage to improve the gas production of the straw.55℃treat can promot the gas production,and increased7.56%compare with TO; the content of the methane has no remarkable divergence of different treat,compare to T0,the content methane of up to55℃9days declines3.2%,others increase0.4-1.52%, different treat have no remarkable divergence (P>0.05)To study the internal mechanism of compost pretreatment how to affect straw gas production, using irradiation sterilization straw as the material, based on the pre-composting temperature data, do experiments in the laboratory to exclude micro-organisms straw composting processthe impact of straw compost for the anaerobic biological production of biogas, researching the composting temperature process on the physical and chemical characteristics of wheat straw and anaerobic biological biogas. The results show that after irradiation, the number of three bacteria on straw are greatly reduced, bacteria, actinomycetes and fungi are reduced99.70%,99.22%and99.73%compared with CK; in the simulated composting experiment, as the time going, the carbon content increase, the nitrogen content first increases and then declines, compare CK-F, the cellulose increases9.17%～18.85%, the hemicellulose content declines4.84%-9.06%, the ligin content declines12.84%～23.71%,which Indicate that the temperature treatment has a good effect on the destruction of wood fiber structure, similarly.the cellulose of the up to55℃9days declines7.32%, hemicelluloses declines27.51%, ligin increases27.52%,and difference is Significant (P<0.05), which descript that high temperature is not conducive to the preservation of the three prime. The gas production results showed that50℃ans55℃treat can improve the gas production,and the gas production increase8.10%～9.12%compares with CK-F; the content of the metheane of初始、30℃、40℃、50℃、55℃、up to55℃2days、 up to55℃5days、up to55℃9days all increase compare with CK-F,indicate that temperature treatment can improve the straw anaerobic biotransformation rate. Compared to the results of the different temperature treatments and composting pretreatment, TS gas production decreased in compost pretreated straw,but55℃increases1.22%,the gas production of the different temperature treatments increase8.10～9.12%, Other treatment increase with varying degrees. This shows that in the straw compost pretreatment temperature is an important factor to affect the treatment effect.The decomposition and utilization of the microorganisms in the compost pretreatment of straw organic matter is an important reason to cause straw cumulative gas production to reduce.