Energy from Waste
County, NRG team up
Carl J. Michaud, Director, Department of Environmental Services, Hennepin County, Minn.
A1,600-ft steam line that is bringing reen energy to downtown Minneapolis buildings and Target
Field – the new ballpark for the Minnesota
Twins – went online in February. Constructed as a joint venture between
Hennepin County and NRG Energy Center
Minneapolis LLC (NRG), the new pipeline
is delivering steam produced at the
Hennepin Energy Recovery Center (HERC),
an energy-from-waste facility in downtown Minneapolis. The result is an
arrangement that provides the county,
NRG and their customers with even
greater energy efficiency and reliability.
Creating Energy From Waste
The county-owned Hennepin Energy
Recovery Center has been burning solid
waste to produce energy since 1989.
Generating energy from waste at HERC
is part of Hennepin County’s compre-
hensive integrated solid waste manage-
ment plan, which includes extensive
waste reduction and recycling efforts.
Hennepin County is the largest
county in Minnesota with a population
of about 1. 1 million. It is home to 45
cities, including Minneapolis and many
of its suburbs, and one township. The
county and the city of Minneapolis
selected the 12.3-acre site for HERC in
the mid-1980s because of its central
proximity to waste sources and the
opportunity to clean up and reuse contaminated land. A bus maintenance
garage had occupied the site previously,
and grease, oil and diesel fuel had contaminated soil and ground water. Restoring
the site was important to area redevelopment plans.
The remediated site became the home
of HERC, which now burns 365,000 tons
of solid waste annually to generate enough
electricity to power 25,000 homes. Garbage
trucks deliver their waste onto HERC’s
tipping floor, and a loader pushes the
waste into a pit. A crane picks up the
waste from the pit and feeds it to the
boilers to produce steam. The steam turns
a 39 MW nameplate turbine to generate
electricity that is sold to Xcel Energy.
A portion of the steam is now diverted
to the new pipeline, which serves the new
ballpark and connects to NRG’s district
heating system that serves more than 100
buildings in 130 square blocks of downtown Minneapolis. HERC’s maximum
steam output is approximately 350,000
lb/hr. In the first three months of operation, around 14,000 lb/hr of steam was
sent to the steam line.
Delivering Multiple Benefits
Even before the steam line was
installed, HERC was helping Minnesota
meet its renewable energy goal of producing 25 percent of energy from renewable sources by 2025. Since it started
Courtesy Hennepin County Public Affairs. Photo Teresa Schafer.
The pipe bridge carrying the steam line from the HERC building to the Seventh Street bridge was
constructed without any alterations to the road or interfering with hauler traffic.