Environmental assessment of energy valorisation of residual agrofood industry biomass in Sicily: a life cycle approach

Abstract

Anaerobic digestion (AD) uses biomass to produce biogas to generate heat and/or electricity. Several studies have reported that the adoption of AD may not necessarily lead to sustainable practices. For example, energy crops may cause significant impact due to the requirement of intensive agricultural practices. Then, residual biomasses are starting to be considered as alternative biomass for energy valorisation trough AD. In this context, this study assesses the potential environmental impacts related to the energy valorisation of agro-food industry waste though the Life Cycle Assessment methodology (ISO 14040). The system examined consists of a real anaerobic digester coupled with a combined heat and power plant (AD-CHP) operating in Sicily. The analysis accountsfor all the impacts occurring from the delivery of the biomass to the AD-CHP plant up to the electricity generation in the CHP. The main outcomes of the study include the eco-profile of the energy system providing electricity and the assessment of the contribution of each life cycle phase aimed at identifying the potential improvement area. Specifically, it highlights that direct emissions are responsible for the highest impact in global warming potential (66%) and feedstock transport contributes for the highest impact (64%) in mineral, fossil fuels and renewable depletion. The contribution of the electricity consumption to the different impact categories is in general relevant ranging from a minimum of about 22% for global warming potential up to 82% for freshwater ecotoxicity. The obtained results can provide useful information to improve the sustainability AD-CHP systems.