Experimental tests on commercial Sweet Product Residue (SPR) as a suitable feed for anaerobic bioenergy (H_2 + CH_4) production

摘要

Highlights•Post-sale refuses was tested as feed for two-step-Anaerobic Digestion (TSAD).•Extrusion was assessed at pilot plant scale process to remove the packaging.•NaOH Pretreatment was evaluated in order to increase the refuses digestibility.•H2+CH4production via TSAD process was experimentally evaluated.•Energy Sustainability Index were used to evaluate the process: pretreatment+TSAD.AbstractFood stores can find themselves in the position of having to dispose of different types of products, such as snacks, confectionery, prepackaged food, drinks and others, Sweet Product Residue (SPR), which presents a great opportunity to produce energy through Anaerobic Digestion (AD), due to its high sugar, carbohidrate and fat contents. In order to valorise SPR, this paper takes into consideration the all necessary treatments; owing the fact that the refuses are constitute by an organic part and packaging (plastic, paper and their combinations), a pretreatment able to remove the latter is necessary. SPR refuse was initially subjected to novel pretreatment approach: extrusion at 200atm to remove the packaging, and a Basic Pre-treatment (BP) then tested through a Two-Stage AD (TSAD) process, for H2and CH4productions. The experimental results were analysed considering three parameters:Efficiency(ξ), which takes into account the quantity of the energy produced as hydrogen plus methane that the bioreaction is able to extract;Efficacy(η),which takes into account the efficiency of the actual test, compared with that obtained from a reference test carried out with glucose;Energy Sustainability Index(ESI), which takes into account the total amount of energy produced as H2plus CH4, and the amount of energy consumed to pre-treat the refuse. The effectiveness of the extrusion process in removing the packaging was very high: about 80% of the organic part present in the SPR was recovered. The obtained results have pointed out that SPR is suitable for energy valorization process:ξ=50%,η=0.67 andESI=24.4, without the need of basic pre-treatment.