A methodology for optimising feed composition for anaerobic co-digestion of agro-industrial wastes

An optimisation protocol for maximising methane production by anaerobic co-digestion of several wastes was carried out. A linear programming method was utilised to set up different blends aimed at maximising the total substrate biodegradation potential (L CH4/kg substrate) or the biokinetic potential (L CH4/kg substrate d). In order to validate the process, three agro-industrial wastes were considered: pig manure, tuna fish waste and biodiesel waste, and the results obtained were validated by experimental studies in discontinuous assays.The highest biodegradation potential (321 L CH4/kg COD) was reached with a mixture composed of 84% pig manure, 5% fish waste and 11% biodiesel waste, while the highest methane production rate (16.4 L CH4/kg COD d) was obtained by a mixture containing 88% pig manure, 4% fish waste and 8% biodiesel waste.Linear programming was proved to be a powerful, useful and easy-to-use tool to estimate methane production in co-digestion units where different substrates can be fed.