Improving Biogas Production Of Corn Stalk Through Chemical And Biological Pretreatment

There are about 0.64 billion tons of agricultural stalks produced in China annually, corn stalk is one kind of these major crops. Corn stalk contains high percentage lignocellulose, which is not biodegradable to anaerobic bacteria, leading to low digestion rate and biogas yield.To improve biogas production of corn stalk, biological and chemical pretreatment methods were suggested. In this research, one edible fungus P. Florida and three chemicals (sodium hydroxide, ammonia, and urea) were chosen to biologically and chemically pretreat corn stalk for increasing biogas production. The main chemical compositions such as lignin, cellulose, hemicellulose, total carbon, and total nitrogen were analyzed after pretreatment, and the effects on biogas production were investigated. After pretreated by P. Florida, the main chemical compositions were analyzed and anaerobic digestion experiments on the biologically pretreated corn stalk were then conducted. It was found that P. Florida could degrade lignocellulose obviously, and biogas production from biologically pretreated corn stalk for 30 and 60 days were increased by 42% and 52%, respectively, as compared to the untreated one.Preliminary study was undertaken first to investigate the effect of chemical pretreatment on biogas production. It was found that lignocellulose was decreased remarkably after NaOH-treated and biogas production after sodium hydroxide treatment was 78.3% higher than that of untreated one. Further study was undertaken to study the effect of NaOH on biogas production in detail. The addition of sodium hydroxide were 4%, 6%, 8%, 10% of corn stalk dry matter, the loading rate of anaerobic digestion after sodium hydroxide treatment were 35g/L, 50g/L, 65g/L, 80g/L. The results showed that at the loading rate of 65g/L, the corn stalk pretreated by 6% NaOH achieved the highest biogas yield, and the biogas production of per kilogram dry matter was 61.4% higher than the untreated one. This shows that NaOH chemical pretreatment is one of effective ways to obviously increase biogas production of corn stalk.NaOH chemical pretreatment has some advantages over biological one such as easy operation, easy management, shorter treatment, lower cost, and higher biogas production therefore, is recommended for large scale biogas production of corn stalk.