Waitrose has begun a six- month trial in which five of its lorries will be powered by rapeseed oil.

The retailer said it would assess the impact of the fuel on the environment and its technical performance in powering vehicles before deciding whether to roll it out.

Waitrose said it had opted to test rapeseed oil in preference to biodiesel, which is favoured by some other retailers, because of its cleaner production process. Unlike biodiesel, rapeseed oil did not undergo a chemical process to change its molecular structure to diesel-like properties and consequently had a carbon footrpint 20% lower, it claimed.

The trials are using fuel from Germany and the UK. Waitrose said it would seek UK sources for all the fuel in the event of a roll-out, potentially growing the crop on its own farm at Leckford in Hampshire.