Environmental and energetic assessment of the use of Italian maize cultivations for bioethanol production: an LCA case study

This work presents a case study of Life Cycle Assessment (LCA) regarding the production of bioethanol from maize cultivations in Italy. The aim is to evaluate the convenience of using this biomass through the assessment of the environmental and energetic impacts of the entire process: from maize cultivation to production, distribution and final use of the biofuel. The analysis was implemented by resorting to two different approaches: the so-called “Cradle-to-grave” approach, which includes all the production steps, from raw material procurement to the final use and disposal of the product, and the so-called “Cradle-to-gate” approach, which studies, in this case, the supply chain up to the production of the biofuel, without considering its final use. The joint analyses of the individual processes in a production system make it possible to identify its impacts and critical steps, allowing assessments and comparisons with alternative productions systems to be made; in this way, it is possible to choose the more sustainable system from an environmental and energetic point of view. The production system of a traditional fossil fuel was assumed as the reference system which all the impacts of the examined processes relate to. Maize is considered to be one of the less efficient biomasses for biofuel production in terms of energy balance; moreover, it has adverse implications from the socio-economic point of view, due to the use of a food biomass for non-food purposes, which has occasionally caused sudden increases in food commodity prices. Additionally, the development of this supply chain would not be easy due to the limited availability of agricultural soil for non-food purposes, especially in Italy, and owing to high production costs. Despite this, the positive values of the energy balance for all scenarios demonstrate the environmental sustainability of this production system. Compared with petrol, the bioethanol derived from the production cycle under consideration entails a 40% reduction in CO2 emissions; in case bioethanol were to be produced from naturally dried maize, this percentage would rise to 47%; the savings obtained are essentially linked to the decrease in CO2 emissions associated with the petrol combustion process: indeed, in the production, distribution and use of petrol, the largest emissions of greenhouse gases occur during the combustion phase, followed by the production stage and last by the transportation of fuel to petrol stations. In the case of bioethanol, on the contrary, it is the production phase (farming and processing) that causes the largest amount of emissions, followed by the other phases. With reference to energy consumption, a similar trend has been observed, i.e. a 50% and a 66% saving if maize is dried naturally. To this impact category only production, and, to a lesser extent, transportation contribute. In the “Cradle-to-gate” analysis, we limited ourselves to making an energy assessment, only analysing the “Consumption of energy sources” impact category. The results of this analysis show that at equal amounts of energy contained, compared with petrol the production of biofuel requires less energy regardless of the bioethanol scenario analysed.