The main engine propelling the truck is subject to the Euro emission standards, but the second engine, keeping the back compartment cold, is subject to significantly weaker regulation.

Because the second engine is classed as Non-Road Mobile Machinery (NRMM), although it is used on roads only, it is eligible to use red diesel. Red diesel is diesel fuel that is dyed red and is mainly for use in registered agricultural or construction vehicles such as tractors, excavators, cranes and some other non-road applications such as boats. Red diesel is a low-sulfur diesel (10 ppm); however, the duty and VAT on red diesel is significantly lower, therefore almost halving the price of diesel that the second engine can use.

The weaker regulation allows the second engine to emit six times as much nitrogen oxide (NO_x) and 29 times as much Particulate Matter (PM) as the main engine of a Euro VI heavy-duty truck, according to Dearman.

Dearman asserts that the combination of weak regulation and cheaper diesel means government is effectively subsidizing air pollution—leaving many drivers asking why they are having to pay £21.50 a day.

Dearman is calling on ministers to end the red diesel subsidy and encourage fleet operators using secondary engines to upgrade to zero-emission equivalents.

The Dearman Engine operates by the vaporization and expansion of cryogenic fluids—specifically, liquid nitrogen. Ambient or low grade waste heat is used as an energy source with the cryogen providing both the working fluid and heat sink. The Dearman Engine process involves the heat being introduced to the cryogenic fluid through direct contact heat exchange with a heat exchange fluid (HEF) inside the engine.

The most advanced application of Dearman technology is as a zero emission transport refrigeration system designed and developed in conjunction with Hubbard Products as a sustainable alternative to the diesel driven units that conventionally keep refrigerated trucks cold. (Earlier post.)