Study On Biogas Producing Characteristics Of Dry Anaerobic Fermentation With Hybrid Pennisetum

Using crop straw,living garbage,food waste,and energy plant to produce biogas by anaerobic fermentation is one of the main ways to solve the shortage of energy in today’s society.In which dry methane fermentation is an widely used method to treat solid bio-wastes with the great advantages like utilization of wastes in its produced form,high organic loading rate,no liquid effluent and comparable amount of biogas production with wet fermentation.And appropriate pretreatment for those raw materials could further accelerate the biogas generation and improve the gas yield,especially for those materials with high cellulose content.The common applied methods for material treatment in biogas producing include physical,chemical,physical chemical,and biological method.Here we report the study on pretreatment methods of hybrid pennisetum（Pennisetum americanum×P.purpureum）,which is one of the most used materials in biogas industry.The study mainly includes three parts:1.The effect of biological pretreatment on dry anaerobic fermentation of hybrid pennisetumTwo enzymes and the fermentation broth of three fungus,Lentinus edodes,Pleurotus ostreatus,and Oudemansiella radicata,were used for material treatment,and the anaerobic digestion was carried out at 35℃,with mass proportion of total solid（TS）being 20%,vaccination being 20% and the original pH being 7.0.The data showed that biological treatment can efficiently improve the biogas yield.The optimum treating volumes of the three fungus’ broth（according to 150 g material）were 100,100,and 50 mL respectively with biogas yield increases being 51.50%,38.97%,and 46.69%.And the optimum treating amounts（according to 250 g feedstock）were 100 and 75 mg respectively with biogas yield increases being 40.61% and 28.04%.Overall,treating material with fungus requires more moderate condition and has a better application prospect.2.The effect of trace element additives on dry anaerobic fermentation of hybrid pennisetumThe required three additives,including FeCl2,CoCl2,and NiCl2 were added to the reactors separately.The results showed that Fe,Co,Ni additives can efficiently improve the biogas yield.Also the additives can shorten the fermentation time and improve the system stability.The optimum amounts being Fe（20 mg/L）、Ni（1 mg/L）、and Co（2 mg/L）with biogas production increases of 43.9%,50.9%,and 32.6%,respectively,compared with the control group.3.The effect of alkali treatment on dry anaerobic fermentation of hybrid pennisetumNaOH,Ca（OH）₂,and urea solutions with the concentration of 1%,2%,4% and 8% were used for material pretreatment.The data showed that NaOH,Ca（OH）₂ and urea treatment can affect the biogas yield significantly.Optimal concentrations of three kinds of pretreatment solutionasare as follows: NaOH4%,Ca（OH）₂8% andurea2%,with biogas increases of 8.4%,35.6%,and 26.8% compared with the control group.Overall,pretreatment with Ca（OH）₂ displayed the best biogas promoting effect.