Rolls-royce confirms all of its current engines can run on 100 percent SAF
Rolls-Royce’s claim that all its current aircraft engines can run on 100% sustainable aviation fuel (SAF) prompts scrutiny of what SAF actually is—typically bio- or waste-derived kerosene substitutes—and whether it meaningfully reduces aviation’s climate impact. Commenters note that while SAF can be a drop‑in, near–carbon‑neutral replacement at the engine level, its large‑scale adoption is constrained by limited feedstocks, land use, cost, and fears of greenwashing. The thread also contrasts aviation with road transport, touching on diesel engines, biofuels from cooking oil, and why such fuels can’t simply replace fossil fuels across the board.
Scope of the Announcement
- Thread clarifies early that this is about Rolls‑Royce aviation engines, not car engines.
- Several comments note this is almost a “non‑story” technically: SAF is designed as a drop‑in replacement for Jet A, so compatibility should be expected, though aviation rightly insists on rigorous testing.
Rolls‑Royce, Cars, and Corporate History
- Rolls‑Royce car engines today are BMW products; the original Rolls‑Royce company now focuses on jet engines, gas turbines, and nuclear reactors.
- Side discussion covers the convoluted brand/ownership history involving Rolls‑Royce, Bentley, VW, Porsche, and others.
Diesel, Kerosene, and Engine Compatibility
- Kerosene and diesel are described as similar; older mechanical diesel engines can run on a wide range of liquids (including vegetable oil and even used motor oil with caveats), but modern diesels are more finicky.
- Military and multi‑fuel engines are cited as partial precedents, but not great for long‑term use.
- Several comments stress that jet engines cannot just run on “whatever”; aviation kerosene has tight specs (freezing point, viscosity, flash point).
What SAF Is
- Defined broadly as jet fuel meeting aviation specs but made via “sustainable” pathways.
- Mention of multiple certified production routes (bio‑based and synthetic), with current practice dominated by used cooking oil and waste fats.
- SAF is promoted as chemically compatible rather than radically different.
Climate Impact and “Sustainability”
- Pro‑SAF view:
- CO₂ released by SAF combustion was recently captured by biomass, unlike fossil carbon; this is argued to be close to carbon‑neutral.
- Seen as especially relevant where batteries are impractical (aviation).
- Critical view:
- Accusations of greenwashing, especially around “net zero by 2050” claims.
- Studies are cited suggesting huge land requirements (e.g., large fractions of national agricultural land) if SAF were scaled to all aviation.
- Concern that we need net removal of CO₂, not just closed short‑term cycles.
Offsets, Taxes, and Funding
- Debate over whether public money should support “clean aviation” versus passing costs through ticket prices.
- Some see customer-paid offsets/SAF options as meaningful when tied to concrete projects; others compare them to medieval indulgences or “greenwashing donations.”
- Note that some airlines currently use SAF at vanishingly small percentages of total fuel.
Other Tangents
- Anecdotes about cars running on vegetable oil and related tax/legality issues.
- Clarification that “autonomy” (from a Brazilian commenter) means vehicle range.
- Question raised but not really answered: why not use SAF widely in cars instead of pushing EVs.