When models outrun politics: Biofuels as a stress test for scenario plausibility

Other text in scientific journal, 2026

Long-term energy scenarios often assign a substantial role to biofuels in net-zero pathways, despite decades of policy support and limited evidence of sustained cost reductions or large-scale diffusion. Using biofuels as a critical case, this paper examines a broader problem in scenario construction: the misalignment between modelled technology pathways and socio-technical feasibility. Drawing on innovation theory, learning-curve evidence, and observed patterns of policy support and investment, it argues that biofuels are constrained by a configuration of mutually reinforcing limitations, including feedstock-dominated costs, weak learning dynamics, and permanent policy dependence. These constraints do not form a simple causal chain, but jointly limit the conditions under which large-scale competitiveness could emerge. Despite this, energy system and integrated assessment models often project extensive biofuel deployment under assumptions that abstract from political volatility and investment risk. The paper argues for greater use of empirical plausibility checks to improve the relevance of long-term energy scenarios.