The global demand for energy, particularly for transport fuels, will continue to increase significantly in the future. In addition to other options, like increased technological efficiencies, traffic reduction or modal shift, biofuels are promoted to contribute strongly to the transport sector in the years to come. Biofuels are also promoted as part of the EU strategy for decarbonising the transport sector with the aim of reducing associated GHG emissions. This paper considers some of the most important biofuels. A selection of biofuel options (biodiesel, bioethanol, biomethane, hydrotreated vegetable oils and fats, lignocellulosic-based fuels) were characterised by their conversion technologies and stage of development. They were analysed, concerning technical (overall efficiency), economic (investments and biofuel production costs) and environmental aspects (GHG performance). Additionally, GHG mitigation costs were calculated with regard to the GHG-based biofuel quota.

With the Renewable Energy Directive 2018/2001 (RED II), adopted in December 2018, the EU is continuing the political framework for the use of renewable energy sources in the transport sector for the period from 2021 to 2030. At the same time, the German federal government has set a target of reducing greenhouse gas (GHG) emissions in the transport sector by at least 40% to 42% by 2030 compared to the 1990 GHG level. To investigate the possible effects of the European and national requirements on the German GHG quota, cost-optimal fuel mixes were modelled to achieve the GHG targets of 26 fuel options in each of the nine different scenarios. The results show clear differences between the scenarios that implement the RED II targets (including 14% renewables in transport by 2030) and those that implement the climate protection target (40–42% GHG reduction compared to 1990 by 2030). If only the minimum requirements of RED II are met, the German climate protection target is clearly missed without further measures. In order to achieve the climate protection target, a significant reduction in the final energy consumption in transport is required, as well as a very high GHG quota of 34.5%, meaning a high proportion of renewables of ca. 40% and using almost all the fuel options considered.

The use of sustainable biofuels in the aviation sector with correspondingly high reduction in specific GHG emissions will make an important contribution to reducing GHG emissions from air traffic. It is expected that airports in Europe will be supplied with JET A-1 blends that also contain various types of sustainable aviation fuels (SAF) in variable proportions (“multiblend”). This article presents the results of a study assessing the environmental impact of various sustainable aviation fuels (SAF) and multiblends, including all relevant parts of their value chains, starting from SAF production to mixing of different SAF with conventional JET A-1 and finally the use of the produced multiblend. The results of the life cycle assessment indicated that the production of some SAF caused less GHG emissions than others due to the use of waste or residues as SAF feedstock or the use of by-products to meet the internal process energy demand. A detailed assessment of GHG emissions of the studied multiblend JET A-1 showed a reduction in greenhouse gas emissions of up to 35% compared to fossil JET A-1.

Limited alternative fuels for a CO₂-neutral aviation sector have already been ASTM certified; synthetic paraffinic kerosene from hydrotreated esters and fatty acids (HEFA-SPK) is one of these—a sustainable aviation fuel. With the hypothesis to improve the greenhouse gas (GHG) balance of a HEFA plant by realizing the required hydrogen supply via electrolysis—power to gas (PTG)—an exemplary SynBioPTx approach is investigated in a comprehensive feasibility study, which is, regarding this comparatively new approach, a novelty in its extent. About 10 scenarios are analysed by technical, environmental, and economic aspects. Within the alternative scenarios on feedstocks, electricity supply, necessary hydrogen supply, and different main products are analysed. For different plant designs of the hybrid refinery, mass and energy balances are elaborated, along with the results of the technical assessment. As a result of this environmental assessment, the attainment of at least 50% GHG mitigation might be possible. GHG highly depends on the renewability grade of the hydrogen provision as well as on the used feedstock. One important conclusion of this economic assessment is that total fuel production costs of 1295 to 1800 EUR t⁻¹ are much higher than current market prices for jet fuel. The scenario in which hydrogen is produced by steam reforming of internally produced naphtha proves to be the best combination of highly reduced GHG emissions and low HEFA-SPK production costs.

As one of the renewable resources, biomass is in demand for the transformation of the energy system to achieve climate protection targets. At the same time, the availability of biomass is limited. In this paper, the energy system optimisation model BenOpt is used to determine the optimal use of the limited biomass under different frame conditions (scenario settings) in the future German energy system. Previous energy system studies have summarised available biomass and biomass conversion technologies in a very general way, with little differentiation between biomass types, conversion technology options with their technical parameters, and their applications. In this paper, 20 different groups of biogenic residual and waste materials; 15 types of energy crops grown on limited agricultural land; other biomasses such as algae, paludiculture, and log wood; 111 different bioenergy technologies; and a total of 265 renewable and fossil energy technology options for meeting sector‐specific energy needs are considered. With this focused and differentiated presentation of biomass and biomass conversion technologies in the energy system, the study is a novelty and fills a research gap. In summary, to achieve the climate protection targets, biomass is most cost‐effective in sectors where direct electrification is not possible or only possible on high costs: in high‐temperature industrial applications and in the aviation and shipping sector. In addition, biomass especially biogas is also the cost‐optimal option used in electricity flexibilisation to cover the residual load. In this study, the political decision on the future role on energy crops and thus the availability of biomass has the greatest influence on the results. Depending on whether a sole use of residues and waste biomass or a maximum availability of residues, waste and cultivated biomass is assumed; the bioenergy used comprises a total of approx. 660 PJ to approx. 1,830 PJ.