Process Condition Optimization For Cassava Residues Anaerobic Fermentation

Cassava residues are the main wastes which produced in the production of fuel ethanol.According to the investigation,the yield ratio of cassava ethanol and cassava residues is about 3:1.Cassava residues is a lignocellulosic material which have high water content and high acidity.The organic matter of cassava residues is difficult to degrade,leading to serious environmental pollution problems.Significant environmental and economic benefit could be obtained by anaerobic fermentation technology that applied in the processing of cassava residues.In this paper,the main characteristics of cassava residues were analysised.The theoretical methane yield of cassava residues was as high as494.81 mL/gVS,which observed good performance in biogas production.Biochemical methane potential of cassava residues and the infllunece of different inoculation ratios on biogas production were determined in this research.The results showed that cassava residues had good performance in biogas production,and thermophilic batch anaerobic fermentation system of cassava residues was stable.When the inoculation ratio was 30%,technical digestion time was 38 days.The methane production of cassava residues reached 192 mL/gVS,while the degradation rate of cassava residues was 38.78%.Because of the high methane content(72%),the quality of biogas is better than others.The performance of cassava residues in semi-continuous digestion at different OLRs(2.3,2.8,3.4,4.0 kg/m~3·d)by mesophilic(37?)acidification-thermophilic(50?)methane formation two-phase and thermophilic(50?)single-phase anaerobic digestion were compared.Results showed that two-phase anaerobic systems exhibited betterperformance than single-phase anaerobic systems.TS biogas yield and volumetric biogas yield of mesophilic acidification-thermophilic methane formation two-phase anaerobic digestion at the appropriate OLRs(3.4 kg/m~3·d)was 383.33 m~3/t and 1.31 m~3/m~3·d with methane content of 64%~68%.The methane production of 269.26 mL/gVS is higher than that of thermophilic batch anaerobic fermentation system.Based on the above research,the efficiency of cassava residues anaerobic fermentation was improved by anaerobic co-digestion.Anaerobic co-digestion were carried out when the ratio of cassava residues andsilage/corncobs were 5:2,1:1 and 2:5respectively.By measuring the index data of acidification fermentation and biogas production in anaerobic fermentation,the corncobs were the best mixed material.This suggested that the acidification fermentation of cassava residues andcorncobs belong to typical acetic acid type at the appropriate ratio of 1:1.Anaerobic co-digestion is stable until the 13th day,and the biogas production is as high as 60 L with methane content of 61.8%.The methane production of 330.04 mL/gVS is higher than that of two-phase anaerobic systems.