Ex ante Life Cycle Assessment and Environmental Cost-Benefit Analysis of an anaerobic digester in Italy

Abstract

The end-use valorisation of food waste (FW) and biowaste is currently being focused on biofuels and bioproducts production through different technologies. This study evaluated the implementation of a new eco-industrial system in Italy that incorporates a micro-scale anaerobic digestion (mAD) and a Solid-State Fermentation (SSF) unit to produce renewable energy (e.g., electricity and heat) from AD biogas and high-quality bio-based products (e.g., bio-pesticides) from digestate. Three scenarios (S0, S1, S2) were modelled. S0 and S1 included only a solid-liquid separation of digestate through a centrifuge, assuming a different fate for the solid fraction (composting in S0 and application on farmland in S1). S2 integrated SSF and reverse osmosis technologies for the treatment and valorisation of digestate with nutrient recovery. The Life Cycle Assessment (LCA) and Environmental Cost-Benefit Analysis (eCBA) methodologies were applied to assess the environmental performances and economic feasibility of the project. The pilot system showed solid environmental performances, especially for S1 and S2, in the five impact categories considered. According to LCA results, the eCBA gives a positive outcome for S2. While the financial and economic analysis showed positive Net Present Values for S2, the project's profitability was not achieved for S0 and S1. If AD plants are implemented at a smaller scale they would represent a favourable investment for the local community; particularly when considering the benefits of nutrient recovery through a complete post-treatment of digestate. The valorisation of organic residues could be better supported through introducing alternative market-based policy tools, as well as removing regulatory barriers and encouraging the implementation of financial schemes to support small-scale renewable production systems and the enhancement of market-based instruments for credits certification from renewable energy production. • Biowaste treatment and valorisation had solid performances in Life Cycle Assessment. • Environmental Cost-Benefit Analysis quantified good revenues for bio-based products. • Nutrient recovery by bio-pesticides and organic fertilizers allow economic benefits. • Limited plans, policies and economic instruments characterize the biowaste sector. • Alternative economic tools can promote biowaste reduction & efficient resources use.