The retailer has retro-fitted the Dual Fuel system to a Mercedes-Axor truck and will test it until the end of the year, it is understood.
The system supplies the engine with methane gas, which replaces a large amount of the diesel required to power the truck.
The gas is stored in a torpedo-shaped cylinder that is fitted onto the chassis of the truck, with no need to access the vehicle's engine, according to supplier Clean Air Power. The system costs £16,000-18,000 to fit, but with methane costing a third as much as diesel, companies now stand to save £10,000 a year in fuel expenditure, the company claimed.
There were also environmental benefits, said sales director Mike Ellithorn.
"Methane emits much less carbon than diesel. A truck running our system on an average trunking operation of 100,000 miles a year will generate lower emissions equivalent to taking 12 cars off the road."
Installing Dual Fuel technology to a truck would result in no loss of engine power, he added, and the truck would still be able to run on 100% diesel if no methane was available.