Effects Of Pretreatment On The Structure Of Wheat Straw And Biogas Production

Biogas is a kind of cleanly and eco-friendly alternative energy resources which produced by microorganism in anaerobic fermentation.The substrates for fermentation,like straw and waste timber,are abundant of lignocellulose that will lead to a slow start-up,long fermentation period and low utilization efficiency of organic matters.It is necessary to take some measures of pretreatment to improve biogas and fermentation efficiency effectively.Some conventional pretreatment methods,like alkaline and acid pretreatment,have been using into practice and achieving remarkable benefits.Those pretreatment affect the structure and chemical composition of substrates markedly that leads to loss of lots of organic matters(organic carbon)and waste of natural resources.However,this issue is always ignored in biogas production.New pretreatment method need to be proposed and researched in order to improve biogas production meanwhile reduce loss of organic carbon.Main results in this study are listed as follow:(1)Employing different NaOH concentration(0%,4%,6% and 8%wt,respectively)to pretreat wheat straw at 35 oC for 8 days.The results show that lignin reduces with the increase of time and alkaline concentration while enzymatic digestion increases.The biggest enzymatic digestion achieves(48 h digestion)from the wheat straw pretreated by 8%wt NaOH for 8days,and at same time,the greatest loss of organic carbon is 0.2 g/g-wheat straw.Comprehensive factors should be involved into the criterion of one pretreatment method,not only hydrolysis,biogas yield or fermentation time,et al.(2)Employing dilute H2SO4-?valerolactone(GVL)to pretreat wheat straw in two different processes: flowing liquid reactor pretreatment and batch pretreatment at 55 oC.After 35 days fermentation of the substrates pretreated in tube-reactor with flowing liquid(mix of acid and GVL),the results demonstrate that there are no obvious differences of biogas production of the substrates pretreated by different temperature,but it improves biogas production of 85% compared the raw wheat straw.Methane production decreases with the increase of acid.Final methane production of the substrate pretreated by 0.05%wt acid achieves 323 mL/gVS compared with 204 m L/gVS of the substrate pretreated by 0.5%wt acid.Then,pretreated liquid is proved still effective in treating wheat straw.Finally,low concentration of GVL can be digested in fermentation and promote methane production is demonstrated in this study.A metabolic way of GVL in anaerobic digestion is proposed according to the experimental results.