Download City of Gresham Cogen and FOG Receiving Station Expansion project

Biogas Project Profile
City of Gresham Cogen and FOG Receiving
Station Expansion project – Municipal Biogas
Project of the Year
Gresham, OR
Owner: City of Gresham
Developer: City of Gresham
Contact: Alan Johnston, Senior Engineer,
503-618-3454
[email protected]
Using biogas produced from the codigestion of municipal sewage and commercial and food industry fats,
oil and grease (FOG), the City of Gresham Wastewater Treatment Plant (WWTP) recently became the
first energy net zero WWTP in the Pacific Northwest, and one of a handful in the U.S.
Partnering with Energy Trust of Oregon and Oregon Department of Energy, the Cogen and FOG
Receiving Station Expansion Project became operational this year. Since February 2015, the plant is
produces about 10% more energy than it consumes on site, becoming better than energy net-zero.
Renewable energy generation and energy efficiency measures have eliminated $500,000 in annual
electrical costs at the WWTP and generated $250,000 in annual FOG tipping fee revenues.
Organizations involved: City of Gresham (Oregon), Energy Trust of Oregon*, Oregon Department of
Energy, Veolia Water North America*
*ABC Member
Inputs and Outputs
Feedstocks:
13,000,000 gallons per day of municipal sewage and 10,000 gallons
per day of fats, oils, and grease (FOG) from restaurant grease traps,
and food industry waste. Approximately $250,000 in tip fees is
generated annually from receiving FOG. Accepted feedstocks
include grease trap and interceptor waste, DAF waste, and food
manufacturing waste.
Products created:
The plant operates two 400 kW combined heat and power (CHP)
biogas fueled cogen engines which (combined) can produce up to
800 kW of renewable electricity as well as hot water (thermal
energy) used for plant processes and building heat. The biogas can
also be used to operate a hot water boiler on site. Digested liquids
and soilds are also beneficially used.
Digestate management:
Following dewatering, the digestate (biosolids) are spread as
fertilizer on agricultural land. At this time, the City applies all of the
approximately 4,000,000 dry pounds of biosolids per year to
agricultural land at no cost to the farmer.
Biogas generation:
250,000-500,000 SCF/day. Maximum daily energy output from
approximately 280,000 SCF of biogas fed to the two cogen units is
800 kW. The WWTP also operates a ground mounted solar array
which has a peak energy output of 360 kW and provides 7% of the
plants electrical production.
Finances, Beneficiaries, and Expansion
Project financing:
The $3,200,000 project was self financed by the City of Gresham
as part of the capital investment project (CIP) process. Energy
Trust of Oregon provided a $330,000 incentive in exchange for
approximately 15 years worth of Environmental Attributes (RECs)
as well as a $40,000 technical assistance grant. Oregon
Department of Energy provided a transferrable tax credit certificate
of $1,064,775. Approximately 40% of the project cost will be paid
for by the Energy Trust of Oregon and Oregon Department of
Energy.
Customer(s):
The thermal energy is used on site to heat the digesters and
provide hot water for building heat. The renewable electric power is
used on site to power the City of Gresham WWTP plant processes.
Any excess electric power is sent to the utility grid through a net
meter.The net metering agreement with the local electrical utility
(PGE) specifies that any net exported-electrical power production at
the end of the net metering year is donated to the utility’s low
income energy assistance program.
Long term plans?
The City is considering a wider variety of feedstocks for codigestion at this time.
Photos
700
Image 3 (left): Digester building with
2-1,000,000 gallon anaerobic
digesters
Image 1 (above): FOG Receiving
Facility with 30,000 gallons of
storage
Image 2 (above): FOG Hauler
connecting to the FOG Receiving
Facility