Effect Of Different Pretreatments On Biogas Production Characteristics Of Anaerobic Fermentation Of Wheat And Corn Straw

Wheat and corn are the main food and economic crops in north China, there are a lot of straw after harvest every year. Burning straw directly not only waste the resource, but also pollute the environment. By anaerobic fermentation technology, changing straw to biogas energy can relieve rural situation of energy shortage and environment pollution. Because wheat and corn straw are mainly composed by lignocelluloses, so they are difficult to be used by methane microorganism. The physical and chemical structure of the straw can be changed by pretreated technology, which can improve gas production obviously. The aim of this study is to research and explore the influence of different chemical and biological pretreatment methods on anaerobic fermentation of the wheat and corn straw. And also provide the theory basis and technical support for improving the straw and corn straw energy conversion and improving the rural domestic biogas gas production.Selected4kind of biological treatments:complex microbial agent, sugar fermentation enzyme, easy composting agent (Amount:6g/kg、8g/kg、10g/kg), microbe decomposition agent (Amount:0.6g/kg、0.8g/kg、1.0g/kg), and2kind of chemical reagent:NaOH(Amount:60g/kg、80g/kg、100g/kg), ammonia(Amount:10mL/L、20mL/L、30mL/L).The wheat and corn straw were deal with this6kind of treatments for7d. Then under the condition of8%mass fraction of total solid, and the substrate of constant temperature fermentation pool as inoculation substance at25℃,30℃,35℃, researched the anaerobic digestion characteristics of the wheat and corn straw. The main results obtained in this paper were listed as the followings.(1)In25-35℃, different additives of complex microbial agent, sugar fermentation enzyme, easy composting agent, microbe decomposition agent, NaOH and ammonia treatments improved the daily biogas peak of the wheat and corn straw, which improved the wheat daily biogas peak by12.11%～108.97%, and improved the corn daily biogas peak by8.10%～64.72%. At the same time shortened the appearance time of the daily biogas peak.(2)By the results of variance analysis, it was known that the biogas production of the wheat straw increased with the temperature increased. The most significant amounts of improving total biogas production of wheat straw were:8g/kg complex microbial agent achieved maximum12288mL at35℃,8g/kg sugar fermentation enzyme achieved maximum11972mL at35℃,0.8g/kg microbe decomposition agent achieved maximum12288mL at35℃,8g/kg easy composting agent achieved maximum12591mL at35℃,100g/kg NaOH achieved maximum13336mL at35℃,30mL/L ammonia achieved maximum11524mL at35 ℃.(3) By the results of variance analysis, it was known that the most significant amounts of improving total biogas production of corn straw were:8g/kg complex microbial agent achieved maximum11290mL at30℃,8g/kg sugar fermentation enzyme achieved maximum12921mL at35℃,0.8g/kg microbe decomposition agent achieved maximum12225mL at35℃,8g/kg easy composting agent achieved maximum12225mL at35℃,80g/kg NaOH achieved maximum13274mL at35℃,20mL/L ammonia achieved maximum12273mL at35℃.(4)The experimental results indicated that different additives of6kinds of treatments improved TS gas yield and the methane content. The average methane content of biogas of pretreated wheat straw increased, by12.23%～38.24%under25℃, by13.50%～32.59%under30℃, by12.85%～44.02%under35℃, respectively. The average methane content of biogas of pretreated corn straw increased, by19.40%～30.30%under25℃, by19.73%～36.56%under30℃, by22.69%～52.96%under35℃, respectively.(5)At the same temperature conditions, it was different for the influence of the optimal additives of6kinds of treatments. Under25℃, achieving maximum biogas production of the wheat straw was30mL/L ammonia treatment, but which of the corn straw was80g/kg NaOH treatment. Under30℃, achieving maximum biogas production of the wheat straw was100g/kg NaOH treatment, but which of the corn straw was8g/kg sugar fermentation enzyme treatment. Under35℃, achieving maximum biogas production of the wheat straw was100g/kg NaOH treatment, but which of the corn straw was80g/kg NaOH treatment.(6) The best treatment method which got biggest economic benefits from biogas of wheat and corn straw with pretreated was microbe decomposition agent at25℃,30℃,35℃, except it was ammonia, which pretreated corn straw at25℃.