Drop-in fuels: how a renewable fuel reaches a road, a ship or an aircraft
A fuel is only useful if an engine can burn it and a regulator lets it be sold. This page explains what "drop-in" means, which specifications road, marine and aviation fuels have to meet, what European law now requires, and the order in which Salacia intends to reach those markets.
What a drop-in fuel is
A drop-in fuel replaces its fossil equivalent directly: same engines, same tanks, same pipelines, no modification. That is different from a fuel that needs a new engine or a new distribution network. The distinction matters because the world's transport runs on engines, storage networks and industrial logistics designed around liquid fuels, and replacing all of that infrastructure overnight is neither feasible nor financeable. A drop-in fuel decarbonises what already exists.
Three markets, three rulebooks
| Market | Fuel specification | How a new renewable fuel gets in |
|---|---|---|
| Road | Diesel to EN 590; paraffinic diesel to EN 15940 | Meets the specification, or is blended into diesel within the limits it sets |
| Marine | Marine fuels to ISO 8217 | Blended with conventional fuels within the standard's provisions for bio-components |
| Aviation | Jet fuel to ASTM D1655; synthetic blends to ASTM D7566 | Each production route is qualified through the ASTM D4054 process, then blended up to the share its annex allows, today 50 % for most routes |
Road and marine markets are the most accessible: their specifications are performance-based and blending is routine. Aviation is the most demanding. Every new route to jet fuel goes through a multi-year qualification with engine and airframe manufacturers before a single litre can be sold, which is why aviation comes last in any credible plan.
What European law requires
Three texts shape the demand. The Renewable Energy Directive, revised in 2023, sets the 2030 target for transport: either a 29 % share of renewable energy or a 14.5 % cut in greenhouse-gas intensity, with a combined sub-target of 5.5 % for advanced biofuels and renewable fuels of non-biological origin. Fuels count only if their sustainability and emission savings are certified under a scheme recognised by the European Commission.
ReFuelEU Aviation, Regulation (EU) 2023/2405, obliges fuel suppliers at European airports to blend a growing minimum share of sustainable aviation fuel: 2 % in 2025, 6 % in 2030, 20 % in 2035, 34 % in 2040, 42 % in 2045 and 70 % in 2050, with a rising sub-share of synthetic fuel from 2030. The audited share reported for 2024 was 0.6 %. The International Energy Agency expects consumption of sustainable aviation fuel to grow from 1 billion litres in 2024 to 9 billion in 2030 in its main case, which would still cover only about 2 % of aviation fuel demand.
FuelEU Maritime, Regulation (EU) 2023/1805, takes a different route: instead of a blending share it caps the greenhouse-gas intensity of the energy used on board ships calling at European ports, with the cap tightening from 2 % below the 2020 reference in 2025 to 80 % below it in 2050.
Salacia's sequence
Salacia's roadmap follows the product pathway rather than a generic claim that every stream can be sold immediately. Sustainability and product certifications are established progressively, moving from technical evaluation to compliant non-aviation sales and, in time, qualified aviation routes. The liquid fractions from the process are refined toward diesel-like, marine and, in time, aviation routes that existing engines already accept. Each status has its own qualification timeline, set out on the Roadmap page.
Read on: Technology Roadmap Glossary Contact