As you probably know, from sucking
down cans of Coke and masticating on candy, sugar — glucose, fructose, sucrose,
dextrose — is an excellent source of energy. Biologically speaking, sugar
molecules are energy-dense, easy to transport, and cheap to digest. There is a
reason why almost every living cell on Earth generates its energy (ATP) from
glucose. Now, researchers at Virginia Tech have successfully created a
sugar-powered fuel cell that has an energy storage density of 596 amp-hours per
kilo — or “one order of magnitude” higher than lithium-ion batteries. This fuel
cell is refillable with a solution of maltodextrin, and its only by products are
electricity and water. The chief researcher, Y.H. Percival Zhang, says the
tech could be commercialized in as soon as three years.
Now, it’s not exactly news that
sugar is an excellent energy source. As a culture we’ve probably known about it
since before we were Homo sapiens. The problem is, unless you’re a
living organism or some kind of incendiary device, extracting that energy is
difficult. In nature, an enzymatic pathway is used — a production line of
tailor-made enzymes that meddle with the glucose molecules until they become
ATP. Because it’s easy enough to produce enzymes in large quantities,
researchers have tried to create fuel cells that use artificial “metabolism” to
break down glucose into electricity (biobatteries), but it has historically proven
very hard to find the right pathway for maximum efficiency and to keep the
enzymes in the right place over a long period of time.
A diagram of the enzymatic fuel
cell. The little Pac-Man things are enzymes.
Now, however, Zhang and friends at
Virginia Tech appear to have built a high-density fuel cell that uses an
enzymatic pathway to create a lot of electricity from glucose. There doesn’t
seem to be much information on how stable this biobattery is over multiple
refills, but if Zhang thinks it could be commercialized in three years, that’s
a very good sign. Curiously, the research paper says that the enzymes are
non-immobilized — meaning Zhang found a certain battery chemistry that doesn’t
require the enzymes to be kept in place… or, alternatively, that it will only
work for a very short time.
Energy densities of various battery
types. “15% Maltodextrin”, in dark blue, is the battery being discussed here.
The Virginia Tech biobattery uses 13
enzymes, plus air (it’s an air-breathing biobattery), to produce nearly 24
electrons from a single glucose unit. This equates to a power output of 0.8
mW/cm, current density of 6 mA/cm, and energy storage density of 596 Ah/kg.
This last figure is impressive, at roughly 10 times the energy density of the
lithium-ion batteries in your mobile devices. [Research paper: doi:10.1038/ncomms4026 - "A high-energy-density sugar biobattery based on a
synthetic enzymatic pathway"]
If Zhang’s biobatteries pan out, you
might soon be recharging your smartphone by pouring in a solution of 15%
maltodextrin. That battery would not only be very safe (it produces water and
electricity), but very cheap to run and very green. This seems to fit in perfectly
with Zhang’s homepage, which talks about how his main goals in life are
replacing crude oil with sugar, and feeding the world.
The other area in which biobatteries
might be useful is powering implanted devices, such as pacemakers — or, in the
future, subcutaneous sensors and computers. Such a biobattery could feed on the glucose in your bloodstream, providing an endless supply of safe electricity for the
myriad implants that futuristic technocrats will surely have.
