Prospect of kitchen wastes for biomaterials and biogas production in a biorefinery approach

A biorefinery approach to obtain biodegradable biomaterials from hospital kitchen wastes (HKW) was proposed before the anaerobic biogas production. Two mixtures corresponding to mixed pre and postconsumption HKW from different diets were used. The lunch+snack (L + S) mixture was rich in proteins (49.8 +/- 2.1 %) whereas that from dinner+breakfast (D + B) was rich in carbohydrates (60.3 +/- 1.9 %). A two-stage hydrothermal processing was proposed for solubilizing first starch (yield 9.8 +/- 0.5 %) and then protein. The recovered starch mixed with the waste solids from the hydrothermal processing and glycerol (mass ratio 8:20:2.5) were used to prepare gelled biomaterials stable for 3 months without microbial contamination. The soluble protein fraction, containing structural and muscle proteins with high nutritional value, was successfully proposed as biostimulant for sunflower. The waste solids exhibited biomethane potential (283.86 +/- 45.02 and 279.34 +/- 50.94 mL CH4/g VS for D + B and L + S) non significantly different from that of the untreated HKW (244.48 and 295.78 mL CH4/g VS for R_D + B and R_L + S). The proposed processing allows the product diversification during the valorization of a model kitchen waste into biomaterials, plant growth stimulants and bioenergy.