The power's out. But on a street in India, there's a cash machine still happily dispensing banknotes. Thanks, in part, to burnt cotton. For this cash machine has a backup battery inside it a battery that contains carbon from carefully combusted cotton. "The exact process is secret," says Inketsu Okina, chief intelligence officer at PJP Eye, the Japanese firm that made the battery. "The temperature is secret and atmosphere is secret. Pressure is secret," he continues. Okina does say that a high temperature is required, above 3,000C (5,432F). And that 1kg (2.2lbs) of cotton yields 200g (7oz) of carbon " with just 2g (0.07oz) needed for each battery cell. PJP Eye also touts the possibility of improving battery performance as well as making batteries greener. "Our carbon has a bigger surface area than graphite," says Okina, describing how the chemistry of the anode in their Cambrian single carbon battery allows for a battery that charges very quickly, up to 10 times faster than existing lithium ion batteries, he claims. The battery's cathode is made from a "base metal" oxide. Although Okina won't disclose exactly which one, these metals include copper, lead, nickel and zinc. The company claims to be working on a dual carbon electrode battery, where both electrodes are made from plant-based carbon. Other researchers are looking at using materials as diverse as corn waste and melon seed shells to generate new types of electrodes for use in batteries.