Portland, Oregon’s reputation for setting itself apart from the pack — and then some — is well deserved.

And while not the first city to capture noxious sewage gas and convert it into vehicle fuel, Portland’s newly approved $9 million "poop-to-power" scheme is certainly ambitious, aiming to cut greenhouse gas emissions by 21,000 tons annually while producing enough homegrown, revenue-generating natural gas to power the equivalent of 154 sanitation trucks for a year.

Portland Environmental Services, the city's wastewater and stormwater management utility, anticipates that capturing methane-rich waste gas produced at the Columbia Boulevard Wastewater Treatment Plant and converting it into renewable natural gas (RNG) will bring in a minimum of $3 million per year through sales of the fuel. The city itself will, of course, also power some its own vehicles with the diesel-replacing poop fuel.

Built in 1952 on Portland's north side, the Columbia Boulevard Wastewater Treatment Plant is the larger of two wastewater treatment facilities, serving 600,000 residential and commercial customers in this Salmon-Safe city of roughly 619,000 residents. Previous to the construction of the plant, raw sewage flowed directly into the Willamette River and floodplain of the Columbia River.

About 2,500 miles of sewage-conveying pipes feed into the plant, which has undergone numerous improvements and expansions over the decades including the addition of a striking, LEED-certified support facility in 2013. The construction of a methane-to-natural-gas conversion facility along with an on-site RNG fueling station is the biggest greenhouse gas-curbing project in the 65-year history of the plant. The scheme is also being heralded as the biggest emissions-reduction project in the history of the entire city although some, including Vivek Shandas, a professor of urban studies at Portland State University, feel that estimation is a touch too generous. "Arguably, we’ve done more with the urban growth boundary, with a number of density policies than we have with any single win, any single project like this," he tells Oregon Public Broadcasting.

Currently, 77 percent of the methane gas generated as a byproduct in the processing of solid human waste at the Columbia Boulevard Wastewater Treatment Plant is harvested and used to generate electricity and heat. But as the Oregonian reports, the remaining 23 percent is flared — or burned and released into air. Along with releasing CO2 into the atmosphere, the wasteful practice of methane flaring has also shown to have other disagreeable impacts on the surrounding environment. Once the new facility is constructed, flaring will cease as Portland achieves full methane recovery status from sewage waste.

A garbage truck in Portland, Oregon By converting methane into renewable natural gas, Portland will produce enough fuel annually to power 154 garbage trucks. (Photo: mike krzeszak/flickr)

Poop gas: Portland's new clean fuel export

Approved unanimously by Portland City Council on Earth Day, the first major components — the conversion facility and the on-site RNG filling station — of the methane-to-renewable-natural-gas scheme are due to be completed and up and running by the end of this year. Initially, the gas will exclusively be used to fuel converted diesel trucks operated by Portland Environmental Services and other city entities. But by the end of 2018, the sewer gas-derived fuel will be connected via pipeline to a natural gas distribution network owned by Portland-based utility NW Natural (née the Northwest Natural Gas Company) and sold both locally and out of state on the renewable energy market.

The Oregonian elaborates:

The city plans to sell the product for credits they will be awarded based on the volume of natural gas they sell to oil companies and other ‘obligated parties’ required to invest in renewable energy or purchase carbon offsets under The Clean Air Act, said Paul Suto, supervising engineer at Portland's environmental services bureau.

The environmental services bureau's natural gas production is expected to bring in $3 million to $10 million of revenue per year, depending on the value of the credits in state and federal energy markets, bureau officials estimated.

While Portland’s buses currently run on biogas, there’s the possibility that the public transit system and other city agencies with sizable fleets could switch over to this special homegrown natural gas at some point down the line.

"We are creating a triple-win for the public in terms of revenue, climate action and cleaner air," says City Commissioner Nick Fish in a press statement. "The renewable natural gas we will produce is truly local and homegrown, a by-product of the waste from every Portland household that we can now repurpose."

With the water flushed by Portlanders soon to be producing a clean source of fuel for diesel trucks, it’s worth noting that in 2015, the city announced plans to tap into its drinking water supply as part of a cutting-edge in-pipe hydroelectricity project that’s been touted as a low-cost, environmentally friendly alternative to conventional hydroelectric projects like dams. That project, powered by the city's drinking water naturally flowing through tiny turbines, harnesses enough juice to keep the lights on and appliances humming in an estimated 150 Portland homes.

As Portland has proved, when you have thousands of miles of pipes running beneath a city, it only makes sense to use these hidden renewable energy goldmines to their fullest advantage — in the end, it doesn’t matter if the water flowing through them is potable or filled with poop.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.