Fundamentals and overview of pretreatment process
Résumé
Anaerobic digestion has been first developed as a low cost wastewater and sludge treatment process as well as sludge stabilisation process. Since the 1990's pretreatment processes have been studied and applied before anaerobic digestion of sludge to reduce the amount to dispose. At present, because of the climate emergency and the need to free oneself from fossil fuels, anaerobic digestion has become a process to produce renewable energy, while keeping on treating waste and producing organic fertilizer. A larger range of feedstocks are thus considered, mainly solid wastes for which pretreatment processes can enhance anaerobic digestion performance. This presentation will first show how pretreatments can improve biogas production, in which cases they can be applied and what are their consequences. Then the limitations of anaerobic digestion, pretreatment objectives and full-scale pretreatment technologies will be reviewed for main feedstocks : sewage sludge, animal by-products and fatty waste, food waste and organic fraction of municipal solid waste. The part on lignocellulosic biomass will focus on lab-scale studies to improve biomethane production as well as biohydrogen production by dark fermentation.