Hydrotreated vegetable oil as a drop-in renewable diesel: Engine bench assessment and policy implications

The decarbonization of the European transport sector requires the accelerated deployment of renewable fuels. Hydrotreated vegetable oil (HVO) is a promising alternative to fossil diesel due to its paraffinic composition, high cetane number, and compatibility with existing engines and infrastructure. This study provides a comprehensive assessment of HVO from both engineering and policy perspectives. Engine test bench experiments were conducted on a turbocharged common-rail diesel engine over a wide operating range consisting of 169 steady-state operating points. Combustion characteristics, fuel consumption, and nitrogen oxide emissions were analyzed and compared between neat HVO and conventional EN590 B7 diesel. The results indicate that HVO exhibits combustion behavior highly similar to B7, with minor differences primarily related to its higher cetane number. In most operating conditions, HVO provided slight improvements in fuel consumption and modest reductions in NOₓ emissions without negatively affecting engine operation Based on the experimental results, literature findings, and the current European regulatory framework, the study discusses policy mechanisms to support renewable fuel adoption and proposes fiscal and regulatory measures to accelerate their deployment despite current production constraints. The findings confirm that HVO represents a technically viable drop-in fuel and may play an important role in the near-term decarbonization of the existing diesel vehicle fleet. • HVO shows combustion behaviour nearly identical to B7 enabling drop-in use. • Engine tests across 169 points show minor combustion improvements with HVO. • Slight BSFC reduction and lower NOx observed under most conditions. • EU HVO production currently covers ∼6% of RED III transport fuel demand. • Fiscal and regulatory measures are needed to scale renewable diesel use.