Closing the loop between life cycle assessment and low-carbon methanol: A critical review for a sustainable energy alternative
Christos G. Savva, Alexandra V. Michailidou, Maria Tournaviti, Christos Vlachokostas, Dimitrios Makris
Abstract
• 66 studies assessing environmental impacts of low-carbon methanol via LCA reviewed. • Methanol produced from waste or byproducts can promote circular economy. • Global Warming Potential was evaluated in all but one of the reviewed studies. • Most of the reviewed studies exclude the use phase of low-carbon methanol in LCA. • LCA practitioners’ choices and assumptions significantly influence the results. Low-carbon methanol can be considered as an alternative to support the decarbonization of transport, with advantages (e.g., use of existing infrastructure) and disadvantages (e.g., lower volumetric energy density) when compared to alternative fuels (e.g., LNG). Although there has been a great increase in the studies of methanol environmental impacts (EIs) in general by applying the Life Cycle Assessment (LCA) methodology, there is no review study exclusively for the LCA of low-carbon methanol. This is a literature gap considering that low-carbon methanol, among other fuels, is nowadays in the epicentre of the decarbonization discussion. On this basis, a pool of 66 low-carbon LCA studies are analytically and critically reviewed. Based on the findings, methodological choices differ significantly between the studies, while some processes related to some of the methanol production stages are often neglected, leading to significant differences in the results. Conventional methanol is selected the most as benchmark product for comparison. Most of the reviewed studies set their system boundary as “Cradle-to-Gate”, thus the end of life and fuel properties of low-carbon methanol are neglected. In addition, CO 2 hydrogenation or biomass to methanol production route was selected in the vast majority of the studies. A main result is that there is a lack of primary data in the LCA studies of low-carbon methanol, which leads to an increased uncertainty in the final results. The material presented promotes a holistic approach and discussed crucial managerial insights and future trends in the rapidly evolving sector of sustainable energy technological options for decarbonization.