Sustainability of grape-ethanol energy chain

Abstract

The aim of this work is to evaluate the sustainability, in terms of greenhouse gases emission saving, of a new potential bio-ethanol production chain in comparison with the most common ones. The innovation consists of producing bio-ethanol from different types of no-food grapes, while usually bio-ethanol is obtained from matrices taken away from crop for food destination: sugar cane, corn, wheat, sugar beet. In the past, breeding programs were conducted with the aim of improving grapevine characteristics, a large number of hybrid vine varieties were produced and are nowadays present in the Viticulture Research Centre (CRA-VIT) Germplasm Collection. Some of them are potentially interesting for bio-energy production because of their high production of sugar, good resistance to diseases, and ability to grow in marginal lands. Life cycle assessment (LCA) of grape ethanol energy chain was performed following two different methods: i) using the spreadsheet BioGrace, developed within the Intelligent Energy Europe program to support and to ease the Renewable Energy Directive 2009/28/EC implementation; ii) using a dedicated LCA software. Emissions were expressed in CO₂ equivalent (CO₂eq). These two tools gave very similar results. The overall emissions impact of ethanol production from grapes on average is about 33 g CO₂eq MJ^–1 of ethanol if prunings are used for steam production and 53 g CO₂eq MJ^–1 of ethanol if methane is used. The comparison with other bio-energy chains points out that the production of ethanol using grapes represents an intermediate situation in terms of general emissions among the different production chains. The results showed that the sustainability limits provided by the normative are respected to this day. On the contrary, from 2017 this production will be sustainable only if the transformation processes will be performed using renewable sources of energy.