Comparative Study On Anaerobic Digestion Of Vegetable Residue By Hydraulic And Gobar Biogas Digesters

At present,the vegetable wastes in wholesale markets around the world have experienced a rapid growth year after year.These wastes have brought many problems to the environment construction.Concerning with the development of vegetable waste treatment and technological development in Lao PDR,this paper mainly uses the Gobar digester and the hydraulic digester to conduct anaerobic digestion experiments on vegetable wastes.The purpose is to obtain the biogas fermentation pattern of Gobar and Hydraulic digesters for the treatment of vegetable wastes,providing a reference for the treatment of vegetable wastes in Lao PDR.The following results are obtained:(1)In the Gobar digester,the design HRT is 30d,the fermentation TS concentration is 13%,and Chinese cabbage,lettuce,rapeseed,and fresh green shoots are used as the mixed fermentation raw material under the normal temperature condition to adopt the semi-continuous feed technology for continuous five anaerobic digestion cycle tests.The results showed that the gas production rate of the Gobar biogas digester was 66.13 ml/g TS and 88.03 mL/g VS,the gas production capacity within the digester was 0.31m~3/(m~3·d),the methane content was 56.56%,and the raw gas production rate was 9.11 mL/g.The gas production rate in the hydraulic biogas digester was 59.94 mL/g TS and 79.82 mL/g VS.The gas production rate within the digester was 0.28 m~3/(m~3?d)and the methane content was 50.56%.The raw material gas production rate was 8.26 ml/g.(2)Vegetable residue is used as raw material for fermentation,which can produce good-quality biogas in both Gobar and hydraulic biogas digesters through anaerobic fermentation.The efficiency of biogas fermentation in the Gobar digester is higher than in the hydraulic biogas digester.And the leakage parameter of the hydraulic biogas digester is 0.03 L/(L?d).(3)The size of the biogas digesters built in Lao PDR from 1996 to 2003 was mostly 16m~3,and from 2004 to 2006 most biogas digesters were 4m~3.Since 2007,6m~3 biogas digesters have been constructed in large quantities.So far,6m~3 biogas digesters are the most in Lao PDR,accounting for 94.12%of the total biogas digesters.A 6m~3 digester,with a daily gas production of 1.38m~3,is enough for a rural household use.It needs 200kg of vegetable waste every day,requiring a vegetable base with a daily output of 1398.6kg.For livestock,6 pigs,or 1 cattle or 360 broiler chickens are required.