scientists turns tomato waste into electricity

A team of scientists is exploring an
unusual source of electricity — damaged
tomatoes that are unsuitable for sale at
the grocery store. Their pilot project
involves a biological-based fuel cell that
uses tomato waste left over from
harvests in Florida.
The researchers presented their work
March 16 at the 251st National Meeting
& Exposition of the American Chemical
Society (ACS) in San Diego. It featured
more than 12,500 presentations on a
wide range of science topics.
“We have found that spoiled and
damaged tomatoes left over from harvest
can be a particularly powerful source of
energy when used in a biological or
microbial electrochemical cell,” says
Namita Shrestha, who is working on the
project. “The process also helps purify
the tomato-contaminated solid waste and
associated waste water.”
Shrestha is a graduate student in the lab
of Venkataramana Gadhamshetty, Ph.D.,
P.E., at the South Dakota School of
Mines & Technology. They are
collaborating on this project with Alex
Fogg, an undergraduate chemistry major
at Princeton University. Other project
collaborators include Daniel Franco,
Joseph Wilder and Simeon Komisar,
Ph.D., at Florida Gulf Coast University.
Tomatoes are a key crop in Florida, notes
Gadhamshetty. He stresses that the
project is important to the state because
Florida generates 396,000 tons of tomato
waste every year, but lacks a good
treatment process.
Gadhamshetty began working on the
topic as a professor at Florida Gulf Coast
University. “The project began a few
years ago when Alex visited my lab in
Fort Myers, Florida, and said he was
interested in researching a local problem,
especially local tomatoes grown in our
state and the large waste treatment
issue,” Gadhamshetty says. “We wanted
to find a way to treat this waste that,
when dumped in landfills, can produce
methane — a powerful greenhouse gas —
and when dumped in water bodies, can
create major water treatment problems.”
So, the team developed a microbial
electrochemical cell that can exploit
tomato waste to generate electric
current. Shrestha explains, “Microbial
electrochemical cells use bacteria to
break down and oxidize organic material
in defective tomatoes.”
The oxidation process, triggered by the
bacteria interacting with tomato waste,
releases electrons that are captured in
the fuel cell and become a source of
electricity. The natural lycopene pigment
in tomatoes, the researchers have found,
is an excellent mediator to encourage
the generation of electrical charges from
the damaged fruits.
Some of their results proved to be
counterintuitive. “Typical biotechnological
applications require, or at least perform
better, when using pure chemicals,
compared to wastes,” Gadhamshetty
notes. “However, we found that electrical
performance using defective tomatoes
was equal or better than using pure
substrates. These wastes can be a rich
source of indigenous redox mediators
and carbon, as well as electrons.”
At the moment, the power output from
their device is quite small: 10 milligrams
of tomato waste can result in 0.3 watts
of electricity. But the researchers note
that with an expected scale up and more
research, electrical output could be
increased by several orders of
magnitude.Research presented at American
Chemical Society's annual meeting in
San Diego.