This weekend, while you’re finishing up the last of the chocolates in your advent calendar — oh admit it, you ate them all already — Britons Andy Pag and John Grimshaw will be rolling to the end of a chocolate-fueled road trip. The duo claim that their trip from Poole, England through the Sahara desert to Timbuktu, Mali, will be the world’s first carbon-negative voyage, thanks to their fuel: 396 gallons of chocolate discarded by a British manufacturer. “This way we’re doing the chocolate factory a favor by taking away their waste, we’re doing the local government a favor by occupying less space in their landfills, but most importantly, we’re doing the environment a favor by reducing our carbon footprint,” says Chris Elvey of biodiesel maker Ecotec, which developed the chocolate-to-fuel technology. Pag and Grimshaw plan to leave their vehicles and equipment in Timbuktu to be reused — at which point we assume the carbon-negativity will end, unless they plan to walk home.