The pair from London and Dorset delivered a biodiesel processing unit to MFC, a local charity.
Independent analysts Carbon Aided estimate that the net effect of the expedition will actually save 15 tonnes of carbon emissions making this the first ever carbon negative expedition.
Along the way the duo had to battle with sand storms, corrupt customs officers and narrowly escaped a shoot out with Al-Qaeda.
Their journey wasn’t made easier by their choice of vehicles, all rescued from scrap yards and including a Toyota Landcruiser.
We are always being told that to be green you have to buy the latest gadget”, said Grimshaw.
“But I don’t think we should be so quick to throw things away.
"There’s still plenty of life in these old vehicles.”
As a result the team had to effect daily roadside repairs, from broken headlights, losing second gear, rusty body panels falling off, frozen fuel, rear wheel blow outs, fuel leaks, oil leaks, air leaks, steering fluid leaks, radiator leaks, not to mention the spine and eardrum damage from the four week journey in a 1989 Ford Iveco Cargo.
"We're not environmentalists at all," Pag points out.
“We just wanted to do a trip that wouldn’t have a detrimental effect on the environment, and the more we learnt about biodiesel the more we thought that’s how we can do it.”
The pair successfully arrived in Timbuktu on Boxing Day and next year Pag plans to fly a paramotor to China using carbon neutral fuel made from landfill waste.
Pag said: “My first step: I need to learn to fly.”
Andy Pag (right) and John Grimshaw with the chocolate fueled Landcruiser arriving in Timbuktu.