Environment, economy benefit from sale of green power to Seattle City Light

An agreement to sell electricity to Seattle City Light (SCL) from a soon-to-come King County waste-to-energy cogeneration system is a win-win collaboration.

Revenues realized from green power sales will help the county’s clean-water utility expand its use of renewable energy and keep rates stable for customers. And the new renewable energy adds to City Light’s growing alternative energy portfolio.

Building on an $8.2 million grant from the Environmental Protection Agency, the county’s Wastewater Treatment Division will invest an estimated $18 million to build the West Point Treatment Plant’s Waste-to-Energy project to replace an aging cogeneration system that was taken offline in 2007 after nearly 23 years of service.

King County and City Light recently came to an agreement on a 20-year contract to sell the new system’s electricity. The county expects the revenue from the sale of energy will begin in January 2012, shortly after the facility is completed in December 2011.

“This agreement is good for King County, good for Seattle City Light, and good for our region’s environment and economy,” said King County Executive Kurt Triplett. “Not only are we turning a waste product into a valuable resource, we’re reducing the county’s need to purchase commercial electrical power. That in turn reduces our operating costs, and contributes to stable monthly rates for our customers.”

“This project fits well in our efforts to increase our new renewable energy portfolio,” added Steve Kern, Power Resource and Environmental Affairs Officer at City Light. “We are committed to meeting our load growth through conservation and new renewables and having this project in our own backyard is an added benefit.”

The EPA grant is expected to cover about 44 percent of the construction cost to install the newer, more efficient cogeneration system that will harness digester gas to generate electricity that can be used on site and sold to the energy utility. In addition to the electricity generated, the cogeneration system will provide most of the heat requirements for plant operations.

Digester gas is a naturally occurring byproduct of the solids treatment process and an excellent source of renewable energy. Because it is a renewable energy source, the new cogeneration system could also become a source of renewable energy certificates that will be sold to offset costs.
“We’re especially grateful for the EPA’s support, because the environmental and economic benefits of this project are remarkable,” said Wastewater Treatment Division Director Christie True.

Project design was finalized in May following a value engineering review and centers on two previously purchased 2.3-megawatt Caterpillar 3612 engine generators that were in storage since 2007. The project at that time had been put on hold because previous construction bids exceeded the county’s planned budget.

With the grant funding secured, King County has moved ahead on soliciting bids. Construction is scheduled expected to begin in early 2010.
When the new cogeneration system begins operating, it will produce about 23,000 Megawatt-hours of electricity each year, which is equivalent to the electricity needed to power for nearly 2,300 homes.