Milieulevenscyclusanalyse ter ondersteuning van beslissingen bij de ontwikkeling van geavanceerde biobrandstoffen

The transport sector contributes to a quarter of Europe's greenhouse gas (GHG) emissions. Although electrification of the light-duty segment is progressing, renewable fuels are essential for decarbonizing harder-to-electrify segments such as heavy-duty transport, aviation, and maritime shipping.. First-generation biofuels derived from edible feedstocks have raised environmental concerns, prompting the European Renewable Energy Directive (RED) to promote the development advanced biofuels from non-edible feedstocks, such as forestry residues, agricultural wastes and other lignocellulosic materials. However, advanced biofuel production technologies have yet to reach commercial maturity, making strategic investments in advanced biofuels essential for rapid climate action. This dissertation explores the environmental sustainability of emerging advanced biofuels in the medium (2030) and long (2050) term, with a particular focus on how sustainability indicators can inform decision-making at the plant, vehicle and national energy system levels. Biofuels are defined as environmentally sustainable in this work if they (1) reduce GHG emissions by at least 65% compared to fossil fuels as mandated by RED, (2) demonstrate lower environmental life cycle impacts for Environmental Footprint (EF) impact categories (e.g., water depletion, acidification, land use), and (3) their production and consumption enable the energy system to maintain an energy return on investment (EROI) of at least 4, the minimum estimated to sustain a developed society. The thesis applies life cycle assessment (LCA) to quantify the climate and other EF environmental impacts of various advanced biofuels, including Fischer-Tropsch diesel for heavy-duty trucks and bionaphtha for use in petrol cars and chemical production. Because these technologies are still under development, a prospective LCA framework is employed to capture potential future impacts. . A scenario-based approach is used to account for uncertainty, exploring a best-case future with strong climate policies and a worst-case future without mitigation efforts. Scenario-specific prospective background databases were constructed, taking into account plausible future developments within the energy and industrial sectors. Primary data was obtained at lab and pilot scales to construct detailed life cycle inventories (LCI), which are then scaled up using manual and proces simulation methods to represent commercial-scale facilities.. The prospective LCA results were integrated in an energy system optimization model to assess how the deployment of biorefineries could affect the broader environmental sustainability and resource demand of Belgium's energy transition. In addition, energy analysis is conducted using a life cycle approach to ensure resource efficiency. Key indicators such as plant efficiency, cumulative energy demand (CED), and EROI are used to assess energy performance. Regardless of the feedstock, the chosen conversion technology, or the decision-context, the results show that advanced biofuel production is associated with low energy efficiency, indicating that their use should be limited to applications where they provide the greatest environmental impact reductions compared to available alternatives. At the plant level, the results show that the climate change impacts of advanced biofuels generally meet RED thresholds, but the results are highly sensitive to the background scenario: worst-case scenarios can lead to 50%-60% higher impacts. Key impact drivers include feedstock choice and energy inputs (electricity, heat, hydrogen),.with the use of biomass-derived hydrogen resulting in lowest impacts and electrolysis-based hydrogen using grid electricity resulting in the highest. At the vehicle level, advanced biofuels outperform fossil fuels, e-fuels, and first-generation biofuels, particularly in terms of climate change, water depletion, and eutrophication. While fuel cell electric trucks may offer lower climate change impacts, they have higher ozone depletion and freshwater eutrophication impacts due to fuel cell production. In the medium term, advanced biofuels perform better than battery electric trucks in several impact categories, but in the long term, battery electric trucks may have comparable or lower environmental impacts. Thus, advanced biofuels are primarily a transitional solution for heavy-duty trucks, which may eventually shift to full electrification. At the system level, optimization results show that, in the medium term, local wood use for bionaphtha production is favored over importing first-generation bioethanol or fossil gasoline. However, in the long term, advanced biofuel production loses relevance as the model shows full electrification of the mobility sector and bionaphtha is redirected for chemicals production. Wood is primarily used for hydrogen production and its derivatives like ammonia. As biorefineries require both wood and hydrogen, their introduction into the energy system increases the need for importing wood, hydrogen, and ammonia, significantly affecting outcomes. As each of these energy carriers are expected to be important for the maritime and aviation sectors, future work will explore the effects of including these sectors into the optimization model. While decarbonization improves many environmental indicators, there are also shifts towards increased water depletion, mineral resource depletion, and land use, mainly due to renewable energy carrier imports. This raises ethical concerns about burdens shifting from Belgium to resource-exporting countries. Future research should explore the social, ethical, and environmental impacts of rising imports for a fair transition. Furthermore, the future availability of constrained resources like wood residues and the impacts of diverting these resources from current applications must be explored. In conclusion, although the advanced biofuels assessed in this thesis can meet GHG reduction targets, they often lead to burden shifts in other impact categories and fail to meet the minimum EROI threshold. A key contribution of this thesis is the application of prospective LCA to advanced biofuels, highlighting areas for further research, including enhancing transparency in prospective scenarios, improving sectoral and impact category coverage, and advancing prospective impact assessment methods.