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This article reviews and compares assessments of three biodiesel fuels: (1) transesterified lipids, (2) hydrotreated vegetable oils (HVO), and (3) woody biomass-to-liquid (BTL) Fischer-Tropsch diesel and selected feedstock options. The article attempts to rank the environmental performance and costs of fuel and feedstock combinations. Due to inter-study differences in goal and study assumptions, the ranking was mostly qualitative and intra-study results are emphasized. Results indicate that HVO made from wastes or by-products such as tall oil, tallow or used cooking oil outperforms transesterified lipids and BTL from woody material, both with respect to environmental life cycle impacts and costs. These feedstock options are, however, of limited availability, and to produce larger volumes of biofuels other raw materials must also be used. BTL from woody biomass seems promising with good environmental performance and the ability not to compete with food production. Production of biofuels from agricultural feedstock sources requires much energy and leads to considerable emissions due to agrochemical inputs. Thus, such biodiesel fuels are ranked lowest in this comparison. Production of feedstock is the most important life cycle stage. Avoiding detrimental land use changes and maintaining good agricultural or forestry management practices are the main challenges to ensure that biofuels can be a sustainable option for the future transport sector.

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Upgraded biogas, also known as biomethane, is increasingly being used as a fuel for transport in several countries and is regarded as an environmentally beneficial option. There are, nevertheless, few studies documenting the environmental impacts of biogas as a transport fuel compared with the alternatives on the market. In this study, life cycle assessment (LCA) methodology was applied to compare the environmental performance of biogas used as a fuel for bus transport with natural gas, electricity fueled buses, biodiesel, and fossil diesel. A sensitivity analysis was performed for the biogas alternative to assess the importance of the underlying assumptions. The results show that biogas has a relatively low contribution to the environmental impact categories assessed. Emissions of greenhouse gases are dependent on assumptions such as system boundaries, transport distances and methane leakages.