Portland treatment plant to produce renewable natural gas

By City of Portland | April 14, 2015

The Portland City Council has approved a contract for final design of a facility at the Columbia Boulevard Wastewater Treatment Plant to convert biogas into compressed natural gas vehicle fuel. Biogas is a byproduct of solids treatment. This project would allow the plant to re-use nearly all of the 600 million cubic feet of biogas it produces annually.

An Environmental Services study of re-use alternatives found that the vehicle fuel option is the most economical and has the greatest environmental benefit because it will reduce diesel fuel use and cut greenhouse gas emissions. Environmental Services is exploring several possible uses for the fuel including selling it to a utility company, selling to Portland area garbage haulers to fuel trucks, fueling city vehicles, or fueling trucks that haul biosolids for land application.

It would cost an estimated $10.9 million to design and construct a biogas processing and storage facility and a vehicle fueling station at the CBWTP. Environmental Services is exploring available grants and financial incentives to help reduce project costs. Construction could start early next year and the facility could be operational by 2017.

“Biogas is a sustainable, renewable energy source,” said Portland City Commissioner Nick Fish. “This project will reduce our reliance on fossil fuels, reduce greenhouse gas emissions and save money for our sewer ratepayers.”

The CBWTP has been moving toward 100 percent biogas re-use for years. More than 30 years ago, Malarkey Roofing Products began purchasing biogas to power part of its manufacturing facility, and currently purchases about 20 percent of the CBWTP’s biogas. The CBWTP uses another 20 percent to fuel boilers that produce heat for buildings and the solids treatment process.

In 2009, the CBWTP installed two 850-kW engine-generators that use about 40 percent of the plant’s biogas as fuel to generate electricity for the wastewater treatment process. Converting biogas to vehicle fuel will re-use practically all the biogas the treatment plant produces.