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Original URL: http://www.theregister.co.uk/2007/04/26/bio_fuel_cell_yumyum_batteries/

American boffin touts sugar-fuelled mobile phones

By Lewis Page
Published Thursday 26th April 2007 17:57 GMT

Fuel-cell researchers are working on portable electric power sources running on a wide range of unconventional fuels, but like all academics they disagree.

Many have seen the future of fuel cells as a hydrogen-driven one. Hydrogen-fuelled devices offer at least one big advantage, in that they would emit only water vapour as a waste product. Thus they have been seen as a possible way ahead by some car manufacturers, seeking to replace fossil-fuelled internal combustion engines with fuel-cells driving electric motors. Others have chosen to fuel engines with hydrogen directly.

But hydrogen is dangerous stuff to keep about and takes a lot of power to produce cleanly. It doesn't eliminate the carbon issue of itself; that would require a source of carbon-free electricity.

An alternative approach is the use of biologically-sourced carbohydrate fuels such as alcohol. Using these in a fuel cell emits carbon dioxide into the atmosphere just like burning fossil fuel, but the plants from which the fuel is made absorbed carbon as they grew. Turning plants into fuel uses power, but theoretically at least this power could come from biofuel too.

If this could be achieved while still leaving enough farmland for people to actually eat as well, the power of the sun would be stored as nice portable liquid fuel in a miraculaously carbon-neutral way, largely by lovely growing plants rather than nasty heavy industry. (Actually there would still be a lot of smelly refineries, but pass on, pass on.)

Unsurprisingly, then, many ecologically-concerned scientists see biofuels as the way ahead. Indeed, the Guardian went so far today (http://technology.guardian.co.uk/weekly/story/0,,2065089,00.html?gusrc=rss&feed=20) as to speculate that "sugar-powered batteries could be the renewable, eco-friendly power source the planet is gasping for." The agricultural lobby is of course only too happy at the idea of fresh revenues and subsidies, too, and would be happy to support such thinking.

The Guardian spoke to Shelly Minteer of St Louis University in Missouri, who reckons she's figured out a way to use simple sugar in fuel cells rather than refined alcohol. That should reduce the amount of energy needed to turn plants into fuel, and sugar is safer and easier to store even than alcohol. Minteer is big on safety; she told the Guardian that she'd worked on hydrogen-fuelled cells in the past but found it too worrying.

Minteer's technique involves using a layer of enzymes taken from bacteria and potatoes laid over the surface of her electrodes. The enzymes convert sugar to energy rather as living organisms do, leading Minteer to characterise her kit as a "biological fuel cell." She has apparently tried running it on soft drinks, but it does best on regular table sugar.

According to the Guardian the "main byproduct" of the cell is water, which begs the question of where all the carbon in the glucose is going. El Reg suspects that it might still be getting emitted as horrible old carbon dioxide; though of course this would be biofuel atmo-carbon rather than fossil, and hence righteous.

Minteer reckons she could have a sugar-powered mobile-phone charger out in a few years, though all she's managed to power so far is a calculator.

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) (http://www.greenpeace.org/raw/content/international/press/reports/energy-r-evolutionsummary.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. ®

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