REGIONAL SCALE
DAIRY PROJECT

DANE COUNTY COMMUNITY DIGESTER - WAUNAKEE, Wl

A SHARED SYSTEM DESIGNED TO REMOVE PHOSPHOROUS

BACKGROUND/OVERVIEW

The Dane County (Wisconsin) Community Digester was buiit
in partnership with the county, the state and three adjoining
family dairy farms. A fourth farm may be added in the future.

The Dane County Community Digester project grew out
of a study committee looking at ways to improve water
quality in the four major lakes in Dane County. The
committee suggested eliminating phosphorous run-off from
surrounding farm fields; the mechanism was a manure
digester using advanced technology to substantially
remove phosphorous. Construction of the digester began in
August 2010 and the facility began operating in early 2011.

THE ANAEROBIC DIGESTION SYSTEM

Approximately 80,000 gallons of manure per day are piped
in from the three adjacent dairy farms. Some food wastes,
restaurant waste grease and glycerin are trucked in to the site.

The Dane County Community Digester is unique in that it
is the first centralized or "community" digester in Wisconsin
accepting manure from multiple farms. In addition, it is the
first digester in Wisconsin built primarily for water quality
reasons to remove phosphorous from the watershed.
Digestate is routed through a high-performance centrifuge
to provide advanced phosphorus removal. This process
isolates approximately 60 percent of the phosphorous in
the solid digestate. Solids are used for bedding on farms
outside the watershed and liquids are piped back to the
farms for land application. The electricity generated is
sold under an advanced renewable tariff to Alliant Energy,
a utility operating in Wisconsin. Captured heat from one
genset is used exclusively to dry separated solids, killing
much of the bacteria and making a better bedding product.



The Dane County Community Digester has resulted in
an estimated 90 metric tons of phosphorus removal
from the watershed since 2012. In addition, odors from
the three farms are greatly reduced, improving the
quality of life on the farms and in their communities.

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•	Digester Type: Complete mix

•	Co-Digestion: Food wastes, restaurant waste
grease and glycerin

•	System Owner/Operator: Clear Horizons, LLC

•	Biogas Generation: 432,000 ft3/day

•	Generating Capacity: 2,200 kW.

•	Biogas Use: Electricity is sold under an advanced
renewable tariff to Alliant Energy.

•	Funding $13 million total project cost -

$4 million tax credit and $3.3 million state water
quality grant

SEPTEMBER 2015

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REGIONAL SCALE
DAIRY PROJECT

CHALLENGES

The system has been successful limiting the amount of
phosphorous entering Dane County's lakes and streams.
Along the way, there have been a series of setbacks that
provide insights for future projects.

First, the digester had manure leaks resulting from a
combination of factors, including an unusually cold winter
that caused above-ground joints to break. The fittings
have all been replaced to avoid this problem in the future.

Another related problem was inadvertent recirculation
of liquid digestate, causing pipeline and vessel
clogging. Additionally, because the influent volume and
characteristics were different from the digester design
criteria, the measurements of phosphorus removal
were initially below expectations. Once this recirculation
problem was addressed, the digester operated within its
design parameters.

Last, the digesters were unable to operate at full capacity
due to sand that built up in the vessels. Beginning in early
2015, operators shut down and cleaned the vessels. All
three digesters should be working at full capacity by the
end of July 2015.

PROJECT BENEFITS

The Dane County Community Digester has resulted in an
estimated 90 metric tons of phosphorus removal from the
watershed since 2012. in addition, odors from the three
farms are greatly reduced, improving the quality of life on
the farms and in their communities. This facility overcame
difficulties to successfully adopt innovative features-
including pipeline delivery of manure from neighboring
farms and centrifugal phosphorus removal—and provide
an example for future projects.

; at'wor!

CLBAB SOJUZONS

SEPTEMBER 20 15

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