Start-Up Strategy and Process Performance of Semi-Continuous Anaerobic Digestion of Raw Sugarcane Vinasse

Abstract

The sugarcane distillery waste water is generated throughout the sugarcane molasses fermentation and distillation. In Reunion Island, a part of the vinasse production is treated by methanisation process. However, the remaining part is diluted then discharged into the sea. The aim of this work is to study the anaerobic treatment of sugar cane vinasse, with energy recovery. Nonetheless, vinasse pollutant load is difficult to treat. Regarding the experimentations, the biochemical potential (BMP) test is used for the determination of the methanogen potential. The BMP is then modelled with the modified Gompertz and the first order kinetic models. Furthermore, a laboratory study is carried out for studying the methane production of vinasse in semi-industrial scale over a period of 130 days. The start-up strategy of the 16 L pilot is proposed, in particular the gradual increase of organic load. The physico-chemical analysis of the medium is needed to prevent and explain the failure of the process. Indeed, the biogas production and physico-chemical measurements during the digestion are presented and discussed. The maximum methane yield of the BMP is 185 $${\text{NL}}_{{{\text{CH}}_{4} }} \,{\text{kg}}_{{{\text{COD}}}}^{ - 1} ,$$ obtained with I/S ratio in terms of volatile solids of 0.7. The outcomes showed that the first-order kinetic and modified Gompertz models fit well with the BMP test curves. Concerning the pilot, the start-up period lasted 45 days the maximum specific production was 151.00 $${\text{NL}}_{{{\text{CH}}_{4} }} \,{\text{kg}}_{{{\text{COD}}}}^{ - 1}$$ (232.31 $${\text{NL}}_{{{\text{biogas}}}} \,{\text{kg}}_{{{\text{COD}}}}^{ - 1}$$ ). In further studies, different mixing strategies will be studied.