A life cycle assessment of different fuel alternatives for Gothenburgs public transportation system

Abstract

One of the solutions for implementing a sustainable transport system, is to increase the use of public transportation and replacing fossil fuels with biofuels. In Gothenburg’s public transport system, there are no fuel alternatives that dominate the market yet. Currently, Volvo have stopped manufacturing biogas buses and instead changed focus towards electrified hybrid buses. The decision has concerned the biogas industry that expects a future competition between renewable fuels in Gothenburg. The purpose of this thesis is to assess and investigate the competitiveness of biodiesel (RME), biogas (from sewage sludge) and biodiesel plug-in hybrids for public buses in Gothenburg. Objectives include, a well-to-wheel life cycle assessment (LCA) for the different fuel alternatives that will indicate their environmental performance, and a survey that aims to indicate possible market potentials and barriers. The following environmental impact categories were included in the LCA: Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), Photochemical ozone creation potential (POCP), and Particles (PM). The results indicate that the environmental impacts per MJ fuel of biodiesel plug-in hybrids in the categories GWP, AP, POCP and particles are small compared to petrodiesel. Biodiesel performs well in comparison to petrodiesel in GWP and POCP. Biogas has the best environmental performance in the impact categories EP and PM while plug-in hybrids have the best environmental performance in GWP and POCP. However, if the batteries are included in the LCA plug-in hybrids, they have the highest environmental impacts among the three renewable fuel alternatives. Petrodiesel has the best environmental performance in AP. The survey indicates that cost and policy targets are the driving market barriers, but also that market potentials can be strengthened through introduction of emerging fuel technologies and better cooperation between stakeholders. Based on the Euro IV emission standard, all analyzed fuels have in general lower environmental impacts per MJ fuel compared to petrodiesel. Therefore, the competiveness of renewable fuel alternatives in Gothenburg, isn’t primarily based on their relative environmental performance. Cost and social aspects are potentially important aspects that should be further investigated. It is also recommended to perform more LCA studies, with different scope, functional unit, allocation methods etc., to better understand the environmental performance of different fuel alternatives.