Enhancing Anaerobic Digestion Of Agricultural Lignocellulosic Materials Through Inorganic Nitrogen Addition And Pretreatment

Biogas production from agricultural waste has large potential for energy demand.However,to enable the optimization of the anaerobic digestion?AD?process with agricultural substrates characteristic must be carefully evaluated.In this study,fresh cornstalk was used to investigate feasibility of agricultural waste as carbon sources and the effect of different nitrogen sources on the anaerobic digestion.The greatest enhancement was observed on methane production yield with high concentration of 240.57 m L/g-TS of ammonia and 250 m L/g-TS of tryptone addition compare to those control tests.The methane production was totality inhibited in overall the nitrogen sources additions excepted nitrate addition.The initial TS?%?and VS?%?of cornstalk were 37.07 m L/g and 35.23 m L/g respectively and sludge initial TS?%?and VS?%?were 9.54 and 2.93,after 40 days incubation the TS?%?and VS?%?were1.56 and 1.14 respectively.Therefore,the evaluation and the feasibility of anaerobic digestion using fresh cornstalk can optimize the nitrogen species supplemented as nitrogen source and the ratio of C/N but need a suitable conversion ratio.In fact,different nitrogen sources promoting different effect.Inhibition of NO₃-N did not affect the bacteria growth in anaerobic digestion in this experiment.However,the addition of ammonia as nitrogen source on AD was optimized the results of biogas production yield in this study compared to others nitrate and tryptone.Anaerobic digestion?AD?is an environmentally sustainable technology to manage agricultural lignocellulosic waste?e.g.,rice straw,peanut straw,sugar cane starw,wheat straw…?.Economic profitability,however,remains a key barrier to widespread implementation of AD for the conversion of specific agricultural lignocellulosic waste to energy.Specifically,high capital and operating costs and reactor instability have continually deterred the use of AD.In order to develop AD systems that are highly efficient and more cost-effective,it was necessary to add ammonia nitrogen to investigate the effect of inorganic nitrogen in anaerobic digestion of different agricultural lignocellulosic waste.AD systems are promising technologies because they allow for separate process optimization of each stage and can enable processing of high-solids content waste.As methanogenesis is one rate limiting step of the process in the conversion of refractory wastes?e.g.,lignocellulosic materials?,optimization of methanogenesis has the potential to radically improve the economic profitability of AD.Various agricultural lignocellulosic waste used for anaerobic digestion have their own advantages and disadvantages,for instance digestion of agricultural lignocellulosic waste may lead to ammonia inhibition due to the high nitrogen content.Due to the lack nitrogen content in the agricultural lignocellulosic waste,high C/N ratios?30:1,75:1and 100:1?were used to investigate the effect of inorganic nitrogen in AD.The specific objectives of this research were to:?a?investigate the promotional effect of NH₄⁺-N addition with agricultural lignocellulosic waste?b?analyzed the improvement of biogas production and optimize C/N ratio for AD using different agricultural lignocellulosic waste.Pretreatment of agricultural lignocellulosic waste is an important step for anaerobic digestion?AD?.Appropriate pretreatment can make the lignocellulosic structure more available by microorganisms,which can accelerate the AD process and enhance the biogas production.In this study,milling,ensiling,alkali?Na OH?and sulfuric acid?H₂SO₄?pretreatments were conducted to investigate the methane production performance of Rice Straw?RS?via anaerobic digestion?AD?.The results of biogas production of the RS pretreatment with H₂SO₄ and NaOH highest cumulative methane production 27.76 m L/g-TS was obtained with combination of Na OH pretreatment.For the control test zero?00 min?,the methane production was only 14.85 m L/g-TS.Fig.4.2.1?a?showed less effect on increasing the methane production,probably due to the accumulation of acids under AD conditions.Fig.4.2.1?b?showed high cumulative methane production with the high value of 32.62 m L/g-TS on the 36 th day with H₂SO₄ 60 min pretreatment time.The cumulative methane production from the control test was estimated at15.67 m L/g-TS and was less than all others samples in the end of the experiment Fig.4.2.1?b?.The finding of this study could provide useful information for pretreatment of RS and the subsequent AD.