From net-zero to zero-fossil in transforming the EU energy system

The EU climate neutrality goal requires a strong reduction in fossil fuel use by 2050. However, whether a complete phase-out is feasible and desirable remains unclear. Here, using an integrated assessment model, we quantify the additional effort needed to achieve a virtually complete phase-out of fossil fuels in the EU by 2050 compared to a least-cost net-zero scenario. In this least-cost net-zero scenario, fossil fuel use already decreases by 87% from 2020 to 2050, driven by renewable power, direct electrification and some biofuels. However, hard-to-abate oil-based hydrocarbons and natural gas persist and are used primarily for chemicals, aviation and shipping. Phasing-out these remaining 13% of fossil fuels requires the large-scale deployment of costly carbon-neutral e-fuels, which about doubles marginal abatement costs from 300€/tCO2 to 650 €/tCO2 (500-1000 €/tCO2) by 2050. Although a fossil phase-out target could strengthen EU climate policy commitment, it also poses additional transformation challenges.