Experimental tests on commercial sweet product residue (SPR) as suitable feed for anaerobic bioenergy (H2+CH4) production

ABSTRACT: Food stores be found in the need to dispose, different types of products such as snacks, confectionery, prepackaged food, drinks, and others. In this context, Sweet Product Residue (SPR) presents a great potential to produce energy through Anaerobic Digestion (AD), due to its high sugar, carbohidrate and fat content. In this study, the refuse was initially subjected to an extrusion process at 200 atm to remove the packeging, and then tested through a Two-Stage AD (TSAD) process with and without Basic Pretreatment (BP). Experimental results were analyzed through three parameters: Efficiency (ξ), which takes into account the quantity of produced energy as hydrogen plus methane that the bioreaction was able to extract, with reference to the available amount of energy embedded in the substrate; Efficacy (η) which takes into account the efficiency of the actual test, compared with that obtained by a reference test carried out with glucose; Energy Sustainability Index (ESI), which takes into account the total amount of produced energy as H2 plus CH4, and the amount of energy spent to pretreat the refuse. The obtained results put in evidence that the SPR is suitable for energy valorization through TSAD process: ξ= 50% , η= 0.67 and ESI= 24.4, for the refuse without basic pretreatment. Also, the effectiveness of the extrusion process to remove the packaging was very high, in fact about 80% of the organic part present in the SPR was recovered.