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Report RSE 17001923

Life Cycle Assessment of bio-waste to energy: a review


The European Energy 2050 roadmap foresees an amount of biomass based produced energy of around 230 TWh in 2020 and of 360 to 494 TWh by 2050, depending on the different scenario considered. According to this figures, the most important increase in electric energy production from biomass is supposed to belong to waste-to-electricity energy pathway, giving that the 2050 production will be twice the 2012 production.

In the Italian scenario, the energy pathway “waste - mechanical/biological treatment (MBT) - Refuse Derived Fuel (RFD) - electric energy” is of particular interest. This energy pathway already contributes for almost the 13% of the electric energy produced by waste combustion.

In the described scenario, the goal of the present work is to carry out a literature review of waste-toenergy Life Cycle Assessment studies. LCA is a technique to assess environmental impacts associated with all the stages of a product's life from raw materials extraction through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling. LCA in fact considers different environmental compartment and all the life cycle of a product/service.

In other words, it allows an holistic valuation of the environmental performance of a product/service. The review helped in clarify some key aspects of LCA - issue such as the functional unit, the system boundaries or the impact categories. In other words, it has been possible to define a methodological framework for the LCA of electric energy from residual biomass.

The main results are:

• It is important to include all the involved processes in the system boundaries as far relevant environmental impact may occur during biomass pre-treatment and after the electricity generation.
• It is useful to compare biomass based processes with similar fossil fuel processes, in order to better understand the biomass based sustainability.
• It is important to take into account all the co-product and sub-product of the process and to carefully allocate impacts.
• As regards Environmental Impact categories, the most important to be considered seem to be Climate Change, Photochemical Oxidant Formation, Air Acidification, Freshwater Eutrophication, Human Toxicity, Freshwater Eco-toxicity. Relevant environmental Impact Categories are Ozone Depletion, Particulate Matter, and Primary Energy Use. Other categories can be considered as optional.

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