permaculture

["Lawrence F. London, Jr." <lflj@intrex.net>]

November 1, 2007 9:46 AM PDT
Pay dirt: Start-up draws electricity from the ground
Posted by Martin LaMonica

Here's a renewable energy source most of us haven't thought of: dirt.

Living Power Systems, a company being spun out of Harvard University,
has made a microbial fuel cell that is able to tease a trickle of
electricity from garden-variety bacteria in the ground.

The ability to generate a tiny flow of electrons from organic material
has been understood for decades and is a staple at elementary school
science fairs.

Living Power Systems has developed a system that it says can create a
useful amount of power, at least for specialized uses.

A sonar beacon powered by the dirt it sits on.
(Credit: Living Power Systems)

Its technology consists of a material that enco urages microbes in the
ground to grow across the surface of an electrode and specialized
circuitry that siphons off the electricity microbes create during
metabolism.

"There are terawatts moving through our biosphere. Solar energy ends up
in our soil and sediment," Peter Girguis, the founder and chief
scientist of Living Power Systems and professor of microbiology at
Harvard. "Think of it as underground solar energy."

The company, which is now looking for funding, has built prototypes of a
few products for low-wattage applications.

One, called the Light Bucket, will provide enough electricity for an LED
light and a cell phone charger to people in the developing world who are
not connected to an electricity grid. The company is also designing a
power supply for wireless sensors and outdoor lighting.

These devices only need to plug into the ground to operate, according to
Girgui s, who made a presentation along with other clean tech companies
at the Conference on Clean Energy in Boston on Tuesday.

Although the company is targeting a few specific markets initially,
Girguis said that microbial fuel cells have the potential to provide 15
percent to 20 percent of household energy by tapping into the
electricity in people's yards or septic systems. The technology could be
used to power a cell phone tower today, he said.

Right now, its devices can generate about one half a watt per day from a
square meter of ground, or 12 watt-hours per day. In its labs, it's been
able to generate 10 times that amount, according to Michael Keating, the
company's co-founder and acting CEO.

That kind of power generation won't run a refrigerator or even a PC
screen, but it does make sense in the developing world, Keating said.

Company executives call microbial fuel cells the " bicycle of
electricity" because they are simple to operate and can be manufactured
locally in developing countries.

Natural versus designer microbes
Wireless sensors, too, are compelling use for microbial fuel cells
because of the high costs involved in replacing sensor batteries,
company executives said.

A sketch of a planned light and cell phone charger for developing countries.
(Credit: Living Power Systems)

For the past two years, a device using the company's technology has been
drawing electricity from the sediment at the bottom of Monterey Bay in
California. The sonar navigational beacon for nuclear submarines was
deployed as part of a military grant. A device in a lab has been
operating for six years.

"The best implementation of this is to use it in a setting where you
want to deploy a device and leave it alone," Girguis said.

A number of organizations are researching microbial fuel cells,
including universities that are designing microbes specifically to
generate electricity. Synthetic Genomics, headed by genetics pioneer J.
Craig Venter, and other firms are looking to make power from human waste
by manipulating microorganisms.

By contrast, Living Power Systems is focused on trying to harness energy
from naturally occurring bacteria rather than those specially designed
for power generation, said Girguis.

Next year, the company intends to have products for a combined light and
cell phone charger aimed at the developing world. It expects to have its
garden light and wireless sensor power supply next year as well,
according to Keating.
p