In a separate process, the fats can be converted into biodiesel or polyurethane, a kind of plastic used in waterproof fabrics and many other applications. Mayfield says shoes made from algae-based materials are already approaching a similar cost to those made from petroleum-derived substances and have the benefit of being fully biodegradable when disposed of. Turning to algae to create oil makes sense. Many of the natural resources we use today came from extremophile bacteria and algae in the deep past, says Mayfield. "That is where 100 per cent of our petroleum comes from," he says.