American boffin touts sugar-fuelled mobile phones

But other boffins poured scorn on the safe, possibly eco-lovely sugar'n'spuds power source. Prof Phil Bartlett of Southampton Uni said the sweetness-powered gear "isn't going to cut it". He calculated that a Minteer yummy-cell unit would need four square metres of electrode to power a two-watt cellphone. Of course, lower outputs might suffice to trickle-charge a device if it was switched off.

Other researchers felt that sugar power wasn't being creative enough. Prof Chris Melhuish of the Bristol robotics lab said he had built a small robot which ran on "unrefined biomass," which turned out to mean - wait for it - dead flies. Yes, that's right: a robot which runs on corpses, albeit tiny ones for now.

Melhuish, worryingly, told The Guardian "The power that you're getting out is relatively small, but so were solar cells thirty years ago." It would seem obvious that he intends to move on to bigger and better things, perhaps powering his planned machine civilisation from farmed humans in vats, Matrix style. (Why is it always the robotics guys?)

There are of course strong incentives to make power industrial without using fossil fuels. Even if you don't believe in global warming, nobody really wants to keep relying on unsympathetic foreign regimes for energy - and even if Western consumers can continue to muscle their way to the head of the global oil and gas queues, and are happy to take the consequences, fossil stocks will eventually run out.

Nonetheless, even radical eco-hippies don't seem to view conventional solar power, hydro, wind, geothermal power etc. as having the potential to replace oil and gas. Greenpeace, for instance, reckon (pdf) that you could only supply 50 per cent of the world's energy by such means by 2050, and even that would require a lot of powersaving.

That boils down to a stark choice between cuddly biofuels or nasty nuclear power to take up the slack. There are other ideas, such as space-based solar collectors etc, but these are largely unproven or unpopular.

So it's easy to see why so many people want biofuels to work. But even at a laptop and mobile-phone level they may be a while off. Prof Peter Bruce at the University of St Andrews said that Minteer's sugar-batteries would yield outputs at least an order of magnitude less than more conventional fuel cells, and low output is already the besetting problem of such kit.

Greenpeace, too, reckon that availability of sustainable biomass is limited, and that it should be used mainly in stationary electric and heating applications already factored into their 50 per cent figure.

All in all, it may be some time before we run our portable gadgetry on a cocktail of dead flies, spuds, Coke and table sugar. ®