A chemical found in mushrooms could one day replace the expensive and polluting heavy metals at the heart of fuel cells and conventional batteries, say chemists at Oxford University, boosting the development of clean power.

They have demonstrated that laccase, an enzyme produced by fungi that grow on rotting wood, can be used as a cheaper and more efficient catalyst. Fuel cells use chemical reactions — such as that between hydrogen and oxygen — to produce emissions-free electricity. But current technology is expensive and requires electrodes that contain rare metals such as platinum.

Christopher Blanford, a chemist at Oxford, is working to replace these metals with enzymes, biological molecules that are cheap and abundant. Enzymes are used by living organisms from bacteria to humans to speed up chemical reactions and there are many different types specialised to catalyse specific reactions.

Laccase has now been shown to equal the catalytic performance of platinum when used to speed up the reactions on the electrode of a fuel cell. The fungi, such as Trametes versicolor, use laccase to break down lignin, a component of the cell walls of plants. But Blanford found that it was also highly effective at reacting oxygen with hydrogen to produce water and electricity. Portable power sources from enzyme-coated electrodes could one day replace the batteries in now everyday use, he said.

Around 3 billion batteries are used every year in western countries, which turn into a mountain of 200,000 tonnes of unrecycled waste in the UK, Canada and the US alone. Even the world's supply of one of the crucial ingredients in normal batteries, zinc, is due to run out in 2037 according to the British Geological Survey. And, although countries such as the UK may have no domestic source of zinc and platinum, there are plenty of plants that can be grown to produce laccase.

Blanford's first goal is to produce a fuel cell that works as well as a rechargeable battery, producing about 400 milliamps for around 2,500 hours. This is enough for a portable music player but, in future, he intends to produce mobile-phone sized batteries or fuel cells in the standard AA shape, all using mass-produced enzymes harvested from genetically modified fungi. He says that a single re-fuelling of an enzyme-based fuel cell would last the equivalent of 20 re-charges of a modern battery.

John Loughhead, executive director of the UK Energy Research Centre, welcomed the Oxford group's work. "Much of the benefit, if they make it work, is not necessarily cleaner energy but that we no longer need to exploit scarce mineral resources, produce unpleasant by-products, and consume energy in manufacturing processes if we can grow the things naturally," he said.

Doug Parr, the chief scientist at Greenpeace, also welcomed the research, but added: "I would ask about the scale of production required [for the enzyme] — what's the yield per mushroom? How much area does it take? As a high value product that may not be too much of a barrier, but a GM fungi would need to be contained in some way."

Turning the laccase electrodes into commercial products still requires a number of steps, including finding the best material to fix the enzymes on to an electrode and second to pack enough of the biological catalyst on to it to make the cell work at useful currents.

Materials that can hold the enzymes, such as carbon, are cheap and plentiful. But the second problem could prove a more difficult problem to crack. "This has puzzled scientists for decades, why are enzymes so large?" said Fraser Armstrong, a professor of chemistry at Oxford University. "There are a lot of people trying to work out how to make small molecules do the same thing. If you could do that, you could put a thousand times more enzymes on a surface."

Loughhead said it would be some time before the technology was available commercially. "My gut feel is this is a possibility for the post-2020 world: discovery to deployment is historically around 20 years so I'd put my money on towards 2030 if it works — probably before nuclear fusion."