Master's thesis and Internship : Integration of Low-Carbon Fuels for Heavy-Duty Transport in the Belgian Energy System toward Carbon Neutrality by 2050

Abstract

Achieving carbon neutrality by 2050 requires profound transformations of national energy systems, particularly in sectors where direct electrification remains technically or economically constrained. Heavy-duty transport, including long-haul road transport, maritime shipping and aviation, is among the most challenging sectors to decarbonize due to high energy density requirements, long operating ranges and limited refueling flexibility. In this context, low-carbon fuels produced through Power-to-X and biogenic pathways are increasingly considered as alternative or complementary solutions to direct electrification.

This thesis investigates the integration of low-carbon fuels into the Belgian energy system by 2050, with a particular focus on their role in decarbonizing hard-to-electrify transport sectors under a strict carbon neutrality constraint. Hydrogen, methane, methanol, ammonia and dimethyl ether (DME) are assessed from a system-level perspective using a multi-energy optimization model developed with the Graph-Based Optimization Modeling Language (GBOML). The model integrates electricity, hydrogen, methane and carbon dioxide flows, while jointly optimizing investment and operational decisions over a full annual horizon.

The results describe an energy system in which combined-cycle gas turbines (CCGT) provide firm and dispatchable generation, as renewable electricity alone is insufficient to ensure supply adequacy and the future role of nuclear power remains uncertain. The system remains strongly dependent on methane and hydrogen imports, while biomethane plays a limited role in energy supply and primarily contributes to carbon dioxide management. In parallel, electrolyzers and direct air capture (DAC) units mainly operate during periods of renewable electricity surplus, allowing excess generation to be valorized instead of curtailed.

From a system-cost perspective, methanol and ammonia emerge as the most economically attractive low-carbon fuels, benefiting from relatively low production costs and good integration within the energy system. However, their direct use as substitutes for diesel in compression-ignition engines remains constrained without blending with a limited share of diesel. Dimethyl ether, by contrast, can directly substitute diesel thanks to its high cetane number, but its large-scale deployment is limited by uncertainties surrounding production costs. The results therefore suggest system configurations in which methanol and ammonia act as central energy carriers, and dimethyl ether is produced at smaller scale through the more mature indirect methanol-based pathway to decarbonize diesel-like transport applications.