Straw Cleaning Pretreatment And Biogas Fermentation

There are a lot of corn straw resources in our country.However,the intrinsic properties of compact fiber structures enable corn straw difficult to be degraded and a low utilization rate of it.Pretreatment can destroy the wood fiber structure of the straw and improve the utilization rate of the straw.There are some problems of the existing pretreatment methods including high cost,low treatment safety and easy secondary pollution.In this study,corn straw was taken as the substrate to investigate the enzymolysis efficiency and biogas production based on the effects of calcium hydroxide concentration,solid-liquid ratio,time and temperature.The results as follows:1.The effect of pretreatment of corn straw was significantly improved with the increasing of calcium hydroxide concentration.The content of corn straw enzymatic reducing sugar could reach 0.296-0.552 g/g（DW）with cellulase（65 U）by the pretreatment of using 2%-10%calcium hydroxide at a solid-liquid ratio of 1:3 and 30℃for 7 days.2.The effect of pretreatment of corn straw was properly improved with the increasing of the moisture.The content of corn straw enzymatic reducing sugar could reach 0.547 g/g（DW）with cellulase（65 U）by the pretreatment of using 8%calcium hydroxide at a solid-liquid ratio of 1:3.There was no significant difference between solid-liquid ratio of 1:2,1:3 treatment of straw enzymolysis sugar.3 The effect of pretreatment of corn straw was properly improved with the extending of the processing time.The content of corn straw enzymatic reducing sugar could reach0.542 g/g（DW）with cellulase（65 U）when straw treated for 7 days.4.Treating straw at 30℃and above can achieve good results.The content of corn straw enzymatic reducing sugar could reach 0.546 g/g（DW）with cellulase（65 U）when straw treated at 30℃.5.Through orthogonal optimization,the optimal processing conditions were determined:Ca（OH）₂concentration 8%,solid-liquid ratio 1:3,processing temperature30℃,processing time 7 days,The content of corn straw enzymatic reducing sugar could reach 0.551 g/g（DW）with 65 U cellulose,and the lignin removal rate could reach 25.5%.The surface structure of straw was observed and studied by SEM.The results showed that the straw structure became loose and the surface voids increased after treatment.6.The biogas fermentation potential of straw was studied with high temperature anaerobic fermentation for 15 days.Under the optimal conditions,the methane yield could reach 274.29 m L·g^-1VS,which was 70.76%higher than that of untreated group.