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Environmental Services

Wastewater Treatment Plant

The City’s treatment plant treats an average of 12 million gallons daily and serves approximately 129,000 customers in Gresham, Fairview, and Wood Village. 

Energy Net Zero

In 2015, the treatment plant reached energy net zero. The plant now produces more energy than it uses, saving the City an estimated $500,000 a year in electricity costs.

Fats, oils, and grease (FOG) are trucked to the plant from local food service establishments. The City collects a tipping fee for receiving and recycling this waste. Adding FOG to the digestion process increases biogas production.

 The biogas produced is treated to remove contaminants and moisture and fed into two powerful cogen engines that convert biogas into heat and electricity. 

How the Plant Works
Educational Tours
  • FOG Tanks
  • Large solar array with trees in the distance.

The Net Zero Story

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  • Gresham’s Wastewater Treatment Plant is the first in the Pacific Northwest to reach energy net zero status, meaning the plant produces at least as much energy as it uses. We celebrated the achievement with the next generation of great minds on Earth Day 2015.

  • Fats, oils, and grease collected by regional restaurants and food service establishments come in on trucks from six haulers – about 12,000 gallons a day.  
    FOG is fed into digesters and the natural byproduct, biogas, is captured, treated, and converted into heat and electricity.

  • Gresham earns up to $350,000 a year from fats, oils, and grease collection.

  • The treatment plant got to net zero two ways. It made it’s operations and equipment more efficient (cutting energy consumption), but mostly it got to net zero by producing renewable energy on-site. This is the fats, oils, and grease receiving station.

  • The co-generators are powerful gas engines that convert the biogas into heat and electricity – enough to heat the plant and produce 6.3 million kWh of electricity a year. Gresham saves $500,000 a year on electricity.

  • A solar array made up of 1,904 panels operates 365 days a year, producing 440,000 kWh a year, or 7% of the renewable power produced at the treatment plant. Clean energy is sent to the electrical grid and accounted against plant energy use through net-metering. Excess energy produced is managed by PGE to supply low-rate power to economically-stressed households throughout PGE’s service area.

  • Gresham’s plant is one of only a handful in the United States to achieve net zero status. Discover the ingenuity and collaborative spirit that made possible an environmental achievement at the City – engineering the Pacific Northwest’s first energy net zero wastewater treatment plant. Achieving net zero status means that the plant makes about the same amount of electricity as it consumes in a year, saving tax dollars and protecting the environment.