One of the operators walks through the system that converts hog waste into electricity and creates carbon offset credits. Photo: Google Green Blog
A pilot waste-to-energy system constructed
by Duke University and Duke Energy garnered the
endorsement of Google Inc., which invests in high-quality carbon offsets from
across the nation to fulfill its own carbon neutrality goals.
The system, on a hog finishing facility 25
miles west of Winston-Salem,
converts hog waste into electricity and creates carbon offset credits.
By capturing greenhouse gases from hog
waste and burning them to run a turbine, the system produces enough electricity
to power 35 homes for a year. It is expected to be able to prevent the release
of greenhouse gases equivalent to nearly 5,000 metric tons of carbon dioxide
per year, which is like taking 900 cars off the road.
The $1.2 million prototype system was built
at Loyd Ray Farms, a 9,000-head hog finishing operation northwest of Yadkinville, N.C.
It is intended to serve as a model for other hog farms seeking to manage waste,
reduce greenhouse gas emissions, and develop on-farm renewable power. Though
this is an established farm, the system meets North Carolina’s environmental standards for
new and expanded hog farms.
It was built mostly with off-the-shelf
technology and is an “open source” design that others may freely
adopt. The system includes a lined and covered anaerobic digester and a lined
aeration basin. Methane gas is collected under a thick plastic dome over the
digester. Gas which isn’t burned in the turbine is burned in a flare to prevent
Open waste lagoons currently in use on most
North Carolina hog finishing farms are prolific producers of methane gas, which
is 21 times more potent than carbon dioxide, pound-for-pound, as a greenhouse
“It is exciting to see the system up
and running, and even more exciting that it’s getting recognized by
Google,” says Tatjana Vujic, director of the university’s Duke Carbon
Offsets Initiative. “Completing this full-scale system and getting it
operational is a great testament to its design and the foresight of all of its
Duke University and Duke Energy
have been developing the pilot project for nearly three years, with additional
grant funding from the U.S. Department of Agriculture and the North Carolina
Department of Environment and Natural Resources Lagoon Conversion Program. Duke
Energy and the university will share operational and maintenance costs for the
first 10 years of operation. Google will assume a share of the university’s
portion of the costs in return for a portion of the carbon offsets for a 5-year
The project is expected to yield many
benefits beyond renewable energy production and greenhouse gas reductions,
including improved water and air quality; reduced odors, pathogens and
nutrients; and increased farm productivity.
“It is rewarding to see three years of
hard work come into operation and exciting to have Google as a new partner in
this project,” says Owen Smith, managing director of Duke Energy’s
regulated renewables business. “As North
Carolina continues to explore new ways to generate
renewable energy from hog waste, this site serves as a showcase for what others
can do to capture the energy from hog waste and turn it into usable electricity
Capturing the methane creates carbon offset
credits for Duke University and Google and using it to
generate electricity creates renewable energy credits for Duke Energy. Loyd Ray
Farms will use surplus electricity on-site.
Duke University engineering
professor Marc Deshusses and his students are also studying the system’s
performance. “Now that the system is on the ground, we have an opportunity
to evaluate and quantify all of its benefits, and to work on making it more
efficient and economical to build and operate,” Deshusses says.
“Innovative systems that can reduce greenhouse gases plus take waste and
turn it into energy are the kinds of things Duke University
is anxious to evaluate and promote.”
The utility and the university share the
Duke name for a reason: Both were founded through the foresight and investment
of James Buchanan Duke in the early 20th century. Duke
University’s carbon offsets initiative
was created with support from The Duke Endowment, a non-profit foundation based
in Charlotte, N.C.