Study On The Effect Of Abrasive Cutting On Anaerobic Fermentation For Rice Straw To Produce Biogas

Rice is the main food and economic crops in Yangtze River Basin.A large number of rice straw is produced every year.The burning of rice straw directly not only pollutes the environment seriously but also wastes the valuable resource.Transforming rice straw into biogas energy through anaerobic fermentation can relieve the rural situation of energy shortage and environment pollution.Because of the complex structure and the silicon on straw surface,the rice straw is difficult to be digested into biogas without any pretreatment.An abrasive cutting pretreatment was put forward to solve the low digestion rate of the straw during anaerobic fermentation.This study focused on the effect of the abrasive cutting pretreatment with the improvement of the physical and chemical properties of the straw.The promoting effect of abrasive cutting pretreatment on alkali pretreatment was also studied.The results were showed as follows:(i)The sludge got from the straw anaerobic fermentation tank was the effective inoculum for the rice straw to be fermented into biogas.The stable working pH was 7.6?7.9.The highest gas production,highest methane production and the fastest gas production rate could be achieved with the mixture of rice straw and the sludge got from the straw anaerobic fermentation tank.The sustaining pH range was confirmed to be 7.6?7.9 for anaerobic fermentation(ii)The pretreatment was an effective way to deal with the silicon on the straw surface and increase the biogas production.Through the pretreatment of abrasive cutting,the physical size of rice straw could be reduced to 2?3cm,and the inner surface of the rice stem was also exposed.There were obvious marks on the surface of rice straw and 31%silica on the surface of rice straw could be removed through the abrasive cutting pretreatment.The biogas production was increased by 33.65%and the biogas production was 98.10 mL/g TS in abrasive cutting pretreatment group.(iii)The effect of alkali pretreatment on rice straw could be enhanced by the abrasive cutting pretreatment.The ligin and hydrophobic silica could be removed by pretreatment of alkali which could destroy the crystal structure of straw effectively.Compared with the outer surface,the destruction of the inner surface of the straw by alkali pretreatment was more serious due to the lack of silicon protection.The destruction effect of alkali pretreatment was enhanced by abrasive cutting pretreatment.Compared to alkali pretreatment alone,the cumulative biogas production was increased by 23.29%through the combination of abrasive cutting and alkali co-pretreatment.(iv)The factors of alkali pretreatment were optimized for abrasive cutting rice straw to anaerobic fermentation to produce biogas.The orthogonal design was used to optimize abrasive cutting and alkali pretreatment.The results showed that the factors affecting the biogas production ranked from high to low were NaOH concentration,water bath time and water bath temperature.A best digestion rate of rice straw and highest biogas production(157.55 mL/g TS)could be achieved under the condition of NaOH concentration at 4%,water bath time at 3 hours and water bath temperature at 80?.The results in this study would be useful to find a better pretreatment.Furthermore they would also provide scientific reference for the development of straw's being turned into energy.