Selection of inocula conditioning methodologies for the anaerobic digestion of food waste

Food waste (FW) has a high potential for use in biological processes such as anaerobic digestion (AD), especially due to its high content of biodegradable organic matter. To inoculate the reactors, sludge is usually used. The sludge should ideally have good sedimentation and specific methanogenic activity (SMA), which is typical for granular sludge. However, in a Latin American context, the most available and accessible sludges are flocculants with low sedimentation and SMA. Applying technological surveillance between 1975 and 2017, using multicriteria analysis techniques such as analytical hierarchy process (AHP), and consulting with international and national experts, we observed that there were few studies, compared to published studies on the substrates that focused on improving inoculum quality through conditioning to improve its characteristics and maximize methane production. The inoculum-conditioning methodologies identified were grouped into five categories, being the main strategy the addition of nutrients followed by anaerobic digestion with an easily degradable substrate. However, extension of technological surveillance is recommended by incorporating the results published from significant events in the field of anaerobic digestion, such as the Latin American Workshop and Symposium on Anaerobic Digestion and the World Congress on Anaerobic Digestion.