Anaerobic Digestion Performance Of Coffee Wastes

As one of the most popular commodities worldwide,coffee generates great amounts of waste in the production process,including used spent coffee grounds(SCG),coffee husks(CH),coffee parchment(CP),and so on.However,these materials are discarded which results in serious problems like waste disposal and environmental pollution.Thus,finding a green and environmental treatment method has become a research hotspot.Anaerobic digestion(AD)of coffee waste(CW)can not only solve this problem but also contribute to the generation of energy,which has significant advantages.In addition,variables such as organic loading(OL),feed/inoculum ratio(F/I)and pH are key factors affecting the methane production in the AD process.Therefore,the optimal AD conditions of SCG,CH and CP were established by using response surface methodology(RSM).The outcomes demonstrated that the highest cumulative methane yield(CMY)of SCG was 253.3 mL/g VS an F/I ratio of 1.9,OL of 28.5 g VS/L and pH of 6.9.For CH,the optimum OL,F/I ratio and pH were 28.7 g VS/L,0.9 and 7.7,respectively,while the methane production was 189.1 mL/g VS.CP’s methane production was 48.0 mL/g VS at 28.7 gVS/L OL,7.7 pH,and 0.9 F/I.Subsequently,the co-digestion experiment of CW combined with livestock manures was carried out in order to improve the biodegradation rate of SCG,CP,and CH.Results showed that when the ratio of SCG and chicken manure(CM)was 1:1,the maximum CMY of 345.3 mL/g VS was accomplished and the biodegradation rate was 69.7%,as well as a significant synergistic effect of the mixture.This study lays a theoretical foundation for the application and process development of AD of CW in the future.