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Hooley Digester, Oregon

"The Hooley Digester, in its current state, is a wonderful addition to Tillamook County."
- Michele Bradley, General Manager

Sustainability leader in:

  • Renewable energy
  • Community digester
  • Salable byproducts

In the late 1980s, the Agricultural & Resource Economics department at Oregon State University (OSU) began studying mechanisms that lessened methane emissions and made additional improvements to Oregon’s dairy industry. The one avenue of inquiry that clearly merited further investigation involved anaerobic digestion of dairy cow manure — to generate energy, to remove weed seeds and pathogens, to improve local water and air quality, and to generate potting soil, cow bedding and other fibrous material. Oregon's Congressional delegation was supportive of this investigation, and secured roughly $1.5 million for further study.

The investment paid off when, several years later, Oregon Congresswoman Darlene Hooley helped the Port of Tillamook Bay (POTB) secure public financing for a small-scale community digester, modeled on the work completed at OSU. Financing provided by the U.S. Department of Energy, in addition to grants from other agencies, helped to complete the Hooley Digester facility in 2001. Today, the facility is up and running with:

  • An entry lagoon where trucked effluent is deposited
  • Three soft-topped concrete-walled containment cells where effluent is heated/digested
  • Two 200-kilowatt (kW) Caterpillar electricity-generation units (gensets)
  • One methane flare for burning excess gas
  • A covered hopper area where fibrous material is deposited and dried

The digester separates the effluent into three streams: fibrous material, methane gas and treated liquid effluent. The liquid effluent, now pathogen-free, is trucked back to contributing farms for field application. The treated solids are sold as potting soil and as animal bedding. The methane gas is converted into electricity and excess gas is flared.

The Hooley Digester processes manure from approximately 3,000 dairy cows. This reduces odor on the farm and results in pathogen-free organic fertilizer that promotes grass growth. It also creates a modest amount of electricity as well as rich potting soil and excellent animal bedding. An unintended benefit is that the digester reduces greenhouse gas (GHG) emissions by capturing and destroying methane.

Photo: Fibrous material as it exits the hopper at the POTB Hooley Digester facility.

POTB is currently working to expand the digester facility with the help of match money from the state of Oregon obtained by State Senator Betsy Johnson. The match money, originating from a $44.6 million FEMA compensation for storm damages in 2007, provides $31.2 million for development of infrastructure.

With more manure to process, and newer and more efficient gensets, POTB has the potential to improve reliability and increase electricity production from current levels between 150 and 200 kW to levels between 750 kW and 1 megawatt (MW).

A proposed 2010 expansion will increase processed effluent from 3,000 to 5,000 cows, increase electricity production 500 percent above current levels, and result in drier, more fibrous material that POTB can sell at a higher price. POTB’s annual revenue from expanded digester activities is expected to jump from its current level of just over $400,000 to roughly $1.5 million per year.

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