Caterpillar has fueled a hydraulic excavator in the 50-ton class with solar diesel for the first time and sent it for practical testing. The construction equipment manufacturer wants to evaluate whether synthetic fuels (e-fuels) represent a technically and economically viable option for reducing CO₂ emissions during machine operation. The specific model designation, location of use, and duration of the pilot project have not yet been communicated.
Solar diesel is synthesized through a power-to-liquid process from CO₂ and regeneratively produced hydrogen. Compared to fossil diesel, the well-to-wheel CO₂ balance is reduced by up to 90 percent according to the manufacturer's specifications – provided the electricity comes entirely from renewable sources. The fuel is chemically nearly identical to conventional diesel and should therefore be usable without modifications to the engine or fuel system. Whether this also applies to the SCR catalysts and diesel particulate filters typically installed in hydraulic excavators will be tested in the current field trial.
The central question for construction companies is less about technical compatibility than about availability and price. Solar diesel currently costs many times more than fossil diesel – depending on the source, between €2.50 and €4.50 per liter. In addition, there is a lack of widespread infrastructure for refueling at construction sites. As long as there is no government funding or tax incentives in place, the payback period remains mathematically impossible for most businesses. Caterpillar has not yet commented on the planned costs per operating hour compared to standard diesel.
For Caterpillar, the test is another component of its decarbonization strategy. The manufacturer is developing electric excavators and hybrid drives in parallel, but continues to rely on internal combustion engines for heavy machines with high operating hours. Whether solar diesel is positioned as a transitional solution or permanent supplement depends on production scaling and price development. Competitors such as Liebherr and Volvo CE are also testing synthetic fuels – but so far only in the context of isolated pilot projects.
A series launch or binding commitment for the availability of solar diesel as a fueling station option for construction equipment has yet to be announced. Caterpillar's field trial will provide initial operating data on engine performance, fuel consumption, and emissions values under real operating conditions. Until this data is available and compared with conventional diesel, the practical feasibility of solar diesel in earthmoving remains an open question.
