The BioTruck team is attempting the first ever carbon-negative driving expedition across the Sahara Desert to the West African city in Mali in a Ford Iveco cargo lorry.

And the whole thing has been made possible by biodiesel producer Ecotec, based on School Lane in Bamber Bridge, near Preston, which turns waste chocolate into fuel by heating it and mixing it with a number of chemicals – including a secret ingredient.

Expedition leader Andy Pag, 34, from London, and co-driver John Grimshaw, 39, from Dorset, left the UK a week ago and were due to board a ferry from Spain to Morocco.

Andy, who has 15 years' experience organising vehicle-based expeditions across the world, said they were making slow but sure progress.

He said: "The headlights weren't working and we couldn't get it in second gear, so that slowed us down a bit.

"The weeks I was supposed to be doing these jobs, I was having to do press stuff.

"I haven't done all the preparation I wanted to so I've been doing it on the road."

But the pair are not worried about their progress and hope to complete the 4,500-mile journey not long after their December 16 target.

Andy said they had met some friendly faces along the way, including an ex-pat who put them up for the night in Malaga.

The expedition's aim is to not only prove that such a trip can be made using biodiesel, but to also deliver a biodiesel processing unit to MFC, a Malian charity.

This will allow biodiesel to be produced locally from sustainable sources and the carbon savings from the Malian fuel will help to make the expedition not just carbon neutral but carbon negative – a world first.

Andy said: "People always think of Timbuktu as a really remote place and if we can show that you can get there on biodiesel then we can show people that there's no reason why you shouldn't be able to get to the supermarket on it."

>> Chocs away!