Running 10% diesel, the process is not a full green conversion for diesel engines, but it does offer a way for certain businesses to hugely reduce their emissions output without wastefully junking existing assets that could still remain useful for a long time.

The retrofit system keeps the diesel injection system, but adds hydrogen injection directly to the cylinder, as well as independent control of injection timing for both the hydrogen and diesel systems. It doesn't require particularly high-purity hydrogen, and the team has demonstrated that its "stratified" hydrogen injection technique, which creates pockets of higher and lower hydrogen concentrations in the cylinder, reduces the incidence of nitrous oxide emissions below that of a straight diesel.

The overall carbon dioxide emissions drop by some 85%, to around 90 grams/kWh of energy – that would certainly represent a solid intermediate step towards total decarbonization for many operations using large fleets of diesel vehicles.

Of course, it relies on hydrogen being available – which, in most areas, is not yet the case. But as the key green vehicle alternative to lithium batteries, hydrogen's time may be coming. Lithium supply shortages look set to rock the battery EV market in the coming few years, right when government regulations start kicking in to seriously accelerate the transition to zero-emissions driving in many jurisdictions. And green hydrogen projects are springing up all over the globe.