With reference to renewable energy obtained from residual biomass and in relation to the decarbonization targets set for 2020, the largest relative increase in the quantity of biomass destined for this end use is expected to occur in the waste sector, whose quantity in absolute value should double compared to 2012.

The reference framework outlined in brief shows how the promotion of the use of biomass for energy purposes, and in particular those deriving from waste, can contribute to the creation of future energy production that is increasingly independent of fossil sources and, therefore, increasingly climate-friendly. In light of these considerations, it appears essential to evaluate the overall contribution of these supply chains to sustainability, as well as their actual intrinsic environmental sustainability.

Considering the numerous flows in and out of these systems and the numerous variables at play, the Life Cycle Assessment has been identified as the most suitable method of holistic and systematic evaluation of the environmental effects—positive and negative—that these energy conversion processes can produce overall in different environmental sectors and during the different phases of the supply chain.

In general, the analysis and interpretation of these results has revealed that the process associated with the production of energy from SRF has significant negative impacts in different impact categories and especially in POF (with a contribution of around 80%), CC (with a contribution of approximately 75%), AC, TE and ME (with a contribution of approximately 70%), mainly due to direct environmental emissions from the combustion process.

Furthermore, by comparing the two different systems analyzed, we noted that the SRF conversion processes obtained from single-flow systems and from mechanical waste sorting and shredding systems have lower impacts in more than one impact category, compared to the energy conversion of SRF produced in flow differentiation plants. This is particularly evident in the impact categories of toxicity and eutrophication processes and can be traced back to the ‘avoided impacts’ thanks to the reuse of ferrous metals and the co-production of heat during the energy conversion process.

It should also be underlined that the contribution of these processes to the impact category relating to climate change—expressed in kg of CO2 equivalent per kWh of electricity fed into the grid—is always greater than that associated with electricity coming from the Italian energy mix.

Finally, it seems useful to highlight that, among those analyzed, no type of CSS production and its energy conversion is absolutely worse than any other for all the impact categories considered.