Backup power without fossil diesel: Rolls-Royce tests INERATEC’s e-Diesel for data centres

Every data centre, every hospital and every airport keeps a row of diesel generators ready for the day the grid fails. They run rarely, but when they run, nothing else matters. That is precisely why operators have been slow to touch them – and why a laboratory result from Friedrichshafen deserves attention. Rolls-Royce Power Systems has completed a laboratory fuel assessment of INERATEC’s MATERA® e-Diesel, a synthetic diesel made from renewable hydrogen and recycled CO₂. INERATEC’s Swiss subsidiary, INERATEC Schweiz AG in Aarau, is a SPIN member.

What was tested – and what was not

Rolls-Royce Power Systems is the maker of mtu engines, the workhorses behind a large share of the world’s emergency power installations. Its laboratory put the synthetic fuel through the chemical and physical tests that decide whether a fuel may be considered for its engines at all. According to INERATEC, MATERA e-Diesel met the selected requirements of EN 15940 – the European standard for paraffinic diesel – and the relevant parameters of the mtu Fluids and Lubricants Specification. In the elastomer compatibility tests, no significant differences from the reference fuels were observed. The fuel remained stable over at least three months of laboratory storage, its sulphur content stayed below 5 mg/kg, and the net calorific value came in at around 44.0 MJ/kg – comparable to fossil diesel.

Both companies are careful about what this does and does not mean. Engine performance, fuel consumption, emissions behaviour and application-specific operating requirements were outside the scope of this laboratory assessment; long-term stability tests are still running, and any use in a specific engine series remains subject to the applicable fuel releases and customer validation. Tobias Ostermaier, who heads the stationary business unit at Rolls-Royce Power Systems, described the result as an encouraging step in a deliberately evidence-based process in which reliability stays the first priority. In other words: the fuel has passed the entrance exam, not the final one.

Why backup power is a Power-to-X case

Emergency generators are an awkward fit for most defossilisation strategies. They are too important to replace on a whim, too rarely used to justify large capital spending, and too long-running in a prolonged outage for batteries to cover on their own. Replacing the fleet means new technology risk in systems where failure is not an option. INERATEC’s CEO Tim Böltken sums up the alternative in four words: fuel transition, not system replacement. A paraffinic synthetic diesel that meets the same standard as the fuels operators already use lets them keep their generators – and their service contracts – while swapping the molecules in the tank.

This matters more every year. Electricity demand from data centres is rising sharply with the spread of AI, and with it the installed base of backup generation. In its latest newsletter, INERATEC says the joint work with Rolls-Royce Power Systems aims at exactly this segment: lowering the fossil footprint of AI data centre operations while increasing their resilience and sovereignty. The same logic applies to hospitals, transport hubs, telecommunications nodes and – a theme SPIN has covered before – armed forces, where fuel that can be made locally from electricity, water and CO₂ is also a security asset.

The Swiss angle

Switzerland is one of Europe’s denser data-centre markets, with a cluster around Zurich that keeps growing, and it has an ageing fleet of stand-by generators in hospitals, banks and public infrastructure – all of it running on fossil diesel. Many operators are already familiar with EN 15940 because HVO, the hydrotreated vegetable oil sold at Swiss filling stations, falls under the same standard. Synthetic diesel from renewable hydrogen and recycled CO₂ sits in that same paraffinic family, with one decisive difference: its carbon does not depend on crop land or waste-fat supply, which is limited and increasingly contested.

Two things would have to happen for Swiss operators to benefit. First, the engine makers’ step-by-step validation must continue through to engine-specific releases – this laboratory assessment is the first rung of that ladder. Second, the fuel must be available in volume and at a cost that an emergency-power budget can bear. Backup generators burn little fuel in normal years, which makes them an unusually forgiving first market for a premium product: a price gap that is prohibitive for a trucking fleet is a rounding error for a stand-by set that runs 50 hours a year. That is one of the rare corners of the fuel market where e-fuels can compete on resilience and compliance today, and on price later.

As always, the climate case stands or falls with the carbon source. A synthetic diesel earns its place only if its CO₂ is recycled from biogenic, atmospheric or unavoidable industrial sources and the hydrogen comes from renewable electricity. Under those conditions, the generator in the basement stops being a fossil liability – without anyone having to replace it.

Source: INERATEC, press release “INERATEC’s MATERA e-Diesel® completes laboratory fuel assessment with Rolls-Royce Power Systems” (2 July 2026) and INERATEC’s “Next Era Letter” No. 5 (September 2026).

🤖 AI transparency: This text and its visual were created using AI, reviewed and approved by a human.