Life cycle assessment (LCA) of end-of-life dairy products (EoL-DPs) valorization via anaerobic co-digestion with agro-industrial wastes for biogas production

BACKGROUND The aim of the present study was to assess the environmental impacts of end-of-life dairy products (EoL-DPs) management via their co-treatment with agro-industrial wastes (AgW) in a centralized biogas facility located in Cyprus using a gate-to-gate life cycle assessment (LCA) approach. Two different scenarios were examined under the framework of this project. In the first one, co-treatment of EoL-DPs with various AgW in a 20:80 (w/w) ratio was evaluated in a one-stage mesophilic anaerobic digestion (AD) process. In the second scenario, the same amount of EoL-DPs were acidified before methanogenesis with AgW in order to improve biogas production. RESULTS Prior acidification of EoL-DPs showed a better environmental performance compared with the results obtained upon direct co-digestion in a mesophilic digester, having a total impact of 52.44 Pt against 57.13 Pt respectively. Biogas production upon acidification, and therefore energy yield, was higher, reaching up to 22.88 m(3) CH4 ton(-1) feed (229.25 kWh ton(-1) feed), compared with 17.45 m(3) CH4 ton(-1) feed (174.85 kWh ton(-1) feed) for the case where no pretreatment was performed. CONCLUSION The acidification of EoL-DPs enhanced the environmental performance of the process by reducing its impact by 8.2% (in Pt equivalents). The energy consumption of the biogas plant mixing equipment was identified as the process hotspot. However, further analysis of the environmental performance of the proposed process is required by extending the system's boundaries towards a cradle-to-grave approach. (c) 2019 Society of Chemical Industry