One wonders whether this is going anywhere, however it
is intriguing enough. It would be nice if this could be combined
with methane production to fully reduce a charge of organic waste to
a mineralized sludge that could then be dried and blended with
biochar and some soil to commence the integration. One often forgets
to do that last step, yet is allows greater ease of handling. Black
sludge is otherwise rather unpromising on those terms.
The problem is that it all ends up with vat based
processing. A pond is always cheaper and easier however inefficient.
Someone has to swallow hard and make it all happen and not quit
until it is reasonably perfected.
I think though that it can be done and should be
mastered in all its available variations because it just happens to
impact everyone on Earth every day.
Fuel Cell Treats
Waste water and Harvests Energy
By Katherine
Tweed | July 16, 2012
A new microbial fuel
cell creates energy during wastewater treatment and also vastly
reduces the amount of sludge produced. Israel-based company, Emefcy,
named as a play on the acronym for microbial fuel cell (MFC), starts
with the same principle as most wastewater treatment—water is
aerated so bacteria in the liquid break down organic material in a
closed series of containers known as a bioreactor.
"We didn't
invent anything scientifically new," says Ely Cohen, vice
president of marketing and business development for the
four-year-old company.
The novelty factor:
instead of using electricity to push air into the water, Emefcy
uses a permeable filter that allows air in but doesn't let liquid
out, much like how a diaper works. The polyethylene plastic
membrane, similar to materials used in construction, surrounds the
fuel cell chamber into which wastewater flows.
Inside the fuel cell,
Emefcy coaxes anaerobic bacteria, primarily Shewanella
oneidensis and Geobacter sulfurreducens, to release
electrons in an oxygen-free environment. The electrons flow to an
anode and then into a circuit to cathodes in a separate chamber on
the outside of the membrane. The electrons allow the carbon cathodes
to react with oxygen to form carbon dioxide.
The practical side
of the Emefcy fuel cell relates to the materials engineering: both
the anode and cathode are made of a carbon cloth that acts as a
conductor. Precious metals have long been used as conducting
materials in batteries and other types of fuel cells but are
too expensive to use at a commercial scale in microbial fuel cells.
For a typical
paper-recycling factory, one Emefcy fuel cell module, which is about
the size of a cubic meter, could treat about three cubic meters per
day of wastewater depending on the amount of organic material
present, according to Cohen, and the modules can be scaled to meet
the needs of larger or smaller plants.
The bacteria eat a
lot to produce electricity and live a longer life because the
environment is optimized for their survival, so sludge can be cut
down by 80 percent, Cohen says. Roughly four watts of electricity
are produced for every kilogram of organic material that the
bacteria consume. The amount of electricity generated will not
exactly power the entire town, or even the entire processing
facility, but it can offset the energy used to clean the water.
"The energy we
don't consume is more important than the electricity we might
produce," says environmental engineer Bruce Logan of
Pennsylvania State University, an Emefcy advisor.
Municipal and
industrial wastewater plants comprise about 2 percent of the annual
electrical power used in the U.S., but treatment methods have
remained largely unchanged for decades. In traditional systems, most
of the power goes into pumping air through the water so that
bacteria in the water can grow and consume organic material that
remains after the largest particles have been removed. Another
substantial chunk of energy goes into trucking away the leftover
sludge, which almost always ends up in landfills.
Emefcy's technology
has its limitations. The fuel cell is ideal for wastewater that
is high in organic material, mostly wastewater from agriculture and
food processing rather than municipalities. Logan estimates that
quantities of food and beverage wastewater equal domestic
wastewater, and animal and farm wastewater is more than the other
two markets combined. Cohen said that the food additives industry,
in particular, may become a very attractive market for the
technology.
Sludge reduction and
regulatory compliance are also significant drivers for the food and
beverage industry, which is pushing more companies to process
wastewater on site rather than just sending it directly to municipal
treatment facilities, according to a report from
Global Water Intelligence (GWI), a water industry market
research firm based in England. With increasing regulation, Emefcy's
technology could become appealing for this market as well.
Emefcy is building a
demonstration plant in Israel that will scale up to 16 modules
starting next year, and, in the lab, the company is already testing
wastewater from factories across the globe. Emefcy hopes the scalable
system will be available commercially some time in 2013, with a price
tag of $4,000 to $5,000 per module.
Although Emefcy has
garnered a lot of attention for its progress, the microbial fuel cell
industry as a whole is still trying to prove whether this will really
work, says Zhen He, a microbial fuel cell researcher at University of
Wisconsin–Milwaukee's Environmental Biotechnology and Bioenergy
Lab. He notes that of the nearly 4,000 papers published on
microbial fuel cells, less than 2 percent report on processing
volumes of water larger than one liter. "I don't think
one group can deal with everything." he says. "We need the
whole field to move this to a larger scale." But Emefcy is not
alone. There are some other groups, including a team at the J. Craig
Venter Institute, that are scaling pilots of a microbial fuel cell
for wastewater treatment.
While Emefcy tries to
cut down on sludge, other researchers look for ways to turn sludge
into biofuels, such as BlackGold Biofuels in Philadelphia. Another
start-up, Ostara Nutrient Recovery Technologies in Vancouver, is
harvesting minerals that would usually end up in sludge and turning
them into high-grade fertilizer. Anaerobic digestion is also a
growing trend in the industrial wastewater industry, according to the
GWI report. Other companies, like FuelCell Energy in Danbury, Conn.,
are capturing the gas from anaerobic digesters to be used in combined
heat and powerplants.
About 104 municipal
treatment plants use anaerobic digestion gas capture for a combined
heat and cycle plant, according to the U.S. Environmental Protection
Agency. Municipalities are also taking advantage of the falling price
of solar power to offset the energy needs of wastewater
plants.
Other companies are
looking to harness the flow of wastewater facilities to capture at
least some of the hydropower as electricity. Hydrogen is another
attractive by-product of wastewater, and some of Logan's research at
Penn State involves looking into how to capture hydrogen to run fuel
cells.
"I think there's
still some uncertainty with whether the benefit is to make electrical
power or to have a hydrogen production facility," Logan says.
"Right now, it's a toss-up."
Depending on the
location and type of wastewater, there will likely be a market
opportunity for many different solutions. "We're changing the
economics of wastewater," Cohen says. "It's a tremendous
source of energy."
1 comment:
I saw that in some urban areas, sewage is carried separately in sanitary sewers and runoff from streets is carried in storm drains. I hope your this technique would be so effect-able for this regards.
Post a Comment