Jim Pitts stands on walkway overlooking filtration chambers at the King County South Filtration Plant in Renton. Aaron Kunkler/staff photo

Jim Pitts stands on walkway overlooking filtration chambers at the King County South Filtration Plant in Renton. Aaron Kunkler/staff photo

Human waste: Unlikely climate change hero?

King County treatment plant joins effort to counteract effects of carbon dioxide.

Surprisingly, it doesn’t smell that bad.

During a tour on a recent spring afternoon, King County analyst Jim Pitts navigated his way through a network of open-air scaffolds and underground tunnels at one of the county’s wastewater treatment plants in Renton. Despite processing up to 200 million gallons of sewage, runoff and gray water per day, the plant is surprisingly clean and free of offensive odors or waste — even as tons of sludge, garbage and human feces are efficiently processed on the 80-acre site.

On top of cleaning water and returning it to Puget Sound through pipes thousands of feet from shore, the King County South Treatment Plant also produces a product called Loop. Loop is a concentrated and sanitized form of human waste that is used as a highly potent fertilizer for agriculture and forests. It also has the consistency of cake, an observation Pitts was quick to point out as he molded a handful of the treated brown fertilizer into something resembling an animal before dropping it back into a machine.

While this process may seem gross, nearly all pathogens have been removed from the finished Loop, and it is safe to use for many commercial uses across the state, including a collection of farms in Eastern Washington. On top of this, Loop and the wastewater plant are playing a role in a process that is already needed if the planet is to avoid the worst effects of climate change.

Loop is so rich in carbon, it offsets the carbon that’s expended to process the plant’s wastewater. Loop also returns carbon to farmland, allowing crops to grow larger and soak up more carbon.

There are several ways to remove carbon dioxide (CO2) from the atmosphere, many of which are outlined in a report from the Intergovernmental Panel on Climate Change. The report presents a case for keeping global temperatures from rising more than 1.5 degrees Celsius above pre-industrial levels — and if that fails, the need to keep the increase below 2 degrees.

Agriculture, water access and heat-related deaths will be lower at 1.5 degrees. Even still, in areas around the equator, hot days have the potential to be up to 3 degrees Celsius warmer than now with 1.5 degrees of total warming.

In order to stay at or under 1.5 degrees, the world would need to reach net zero emissions by 2050, and for limiting warming below 2 degrees, net zero would need to be met by 2070.

This will require stopping the use of fossil fuels, but also removing carbon from the atmosphere, which will require large investments. James Mulligan is a senior associate with the World Resources Institute, which published a post detailing several techniques to remove carbon from the atmosphere.

“It would be really great to have the technologies available by 2040,” Mulligan said.

Several of these options can be implemented fairly cheaply, but there is a trade-off between cost and effectiveness and feasibility. For example, reforesting is an option. Healthy forests are good at removing CO2 from the atmosphere and storing it in wood and soil. Every acre of restored forestland can rake in around 3 metric tons of CO2 annually.

A recent article in Science Magazine said the U.S. is the largest cumulative emitter of CO2 from fossil fuels, but reforestation has the potential to offset around 20 percent of net annual emissions.

Expanding and enhancing farmland can help store carbon. Farmland is expensive to acquire and maintain and would likely require government subsidies to help landowners. Composting and using products such as Loop can additionally boost carbon storage in farm and forest soils. However, these may not solve global warming on their own, Mulligan said.

“If you think about how much we might be able to get out of those options globally, it’s meaningful,” he said. “It also falls well short of what we need globally.”

Other techniques require more research and development, including using bio-energy like old wood or trash to power energy plants. However, this also requires the plants to actually capture the emissions and store the carbon either underground or use it to make long-lasting products such as concrete.

Other methods can more directly remove large amounts of CO2 from either the air or seawater. Direct air capture involves sucking air into large scrubbers, where it is run through a solution that binds with carbon and removes it. From there, the carbon is turned into pellets and can be stored. Since cleaning units can be stacked, direct air capture provides another major benefit over more natural methods.

“Direct air capture is kind of scalable in a way that none of these other options are,” Mulligan said.

The technology to do this is still expensive. But three companies have already developed systems, and as more join, the price should begin to drop. One recent study cited in the World Resourses Institute’s post found it would cost between $92 to $232 per metric ton to operate direct air capture, and to work as it’s supposed to, it would require using green energy for power. This is still much lower than the $1,000 per cubic ton that was projected around eight years ago, Mulligan said.

It would also require a lot of energy. One of the existing types of direct air capture was estimated to require around 7 percent of all energy in the U.S. But deep decarbonization will require massive penetration of the global energy grid, Mulligan said. Another form of the same idea would scrub seawater of CO2, allowing it to soak up even more from the air. This would require more energy than air scrubbing, but the U.S. Navy already has a prototype in hopes that the captured CO2 could be turned into hydrogen and fuel for vessels.

Some effort like this will likely be necessary in coming years unless the world somehow transitions entirely to clean energy and does away with industries like raising cattle for beef, Mulligan said.

“It would be really great to have the technologies available by 2040,” Mulligan said.

This would allow them to be scaled up by 2050. While a rollout date of 2040 may feel distant, investments should be made now into research and development because there’s up to a 15-year lag between those initial investments and rollout for not only direct air capture, but for forest and soil alternatives as well as seawater capture.

“You’ve got to start doing those now,” Mulligan said.

Air capture alone would require up to $70 million in investments each year, which would scale up to around $250 million annually, according to the institute. This would allow the development and testing of direct air capture systems. Once research and development is done, then it would require public investment to build the required amount of scrubbers.

And unlike other green technology, such as solar panels, which provide a distinct benefit to the private companies building them, technologies like direct air capture of CO2 likely won’t be rolled out en masse by the private sector, according to the institute, because they provide a global public good.


In consideration of how we voice our opinions in the modern world, we’ve closed comments on our websites. We value the opinions of our readers and we encourage you to keep the conversation going.

Please feel free to share your story tips by emailing editor@valleyrecord.com.

To share your opinion for publication, submit a letter through our website https://www.valleyrecord.com/submit-letter/. Include your name, address and daytime phone number. (We’ll only publish your name and hometown.) We reserve the right to edit letters, but if you keep yours to 300 words or less, we won’t ask you to shorten it.

Jim Pitts, King County system analyst holds a handful of Loop, a powerful fertilizer derived from wastewater which the county sells to commercial buyers. The carbon-rich product offsets the carbon expended in operating the plant. Aaron Kunkler/staff photo

Jim Pitts, King County system analyst holds a handful of Loop, a powerful fertilizer derived from wastewater which the county sells to commercial buyers. The carbon-rich product offsets the carbon expended in operating the plant. Aaron Kunkler/staff photo

More in News

King County could be in Phase 2 in two weeks

The county is also hoping the state lets them reopen several businesses by Friday.

Protesters gathered in downtown Snoqualmie on May 30 to voice their opposition to police violence against people of color. Aaron Kunkler/staff photo
Snoqualmie holds peaceful police violence protest

The protest attracted around two dozen people who held signs in downtown Snoqualmie.

File photo
Rates of COVID-19 lower in the Valley

East King County has lower rates than much of the rest of the county.

Kabal Gill, owner of East India Grill in Federal Way, wears gloves to hand over take-out orders at his restaurant on March 23. File photo
New guidelines for Phase 2 reopenings in King County

All workers will need to wear masks as restaurants, retail shops and other businesses reopen.

This undated file photo provided by U.S. Centers for Disease Control and Prevention shows CDC’s laboratory test kit for the new coronavirus. Courtesy photo
Inslee wants nursing home residents and staff tested by June 12

Governor says state will pay for test kits and personal protective equipment.

Stock image
Campgrounds to reopen in 22 Washington counties

Campgrounds in counties actively in Phase 2 of the reopening plan will begin to welcome visitors June 1, state says.

King County Sheriff Mitzi Johanknecht. FILE PHOTO
King County sheriff releases message about Minneapolis Police officer

Mitzi Johanknecht calls video of officer kneeling on neck of George Floyd ‘heartbreaking and disturbing’

File photo of construction near North Bend on Aug. 16. Sound Publishing file photo
                                File photo of construction near North Bend on Aug. 16. Sound Publishing file photo
Rural King County mayors want state to let them enter Phase 2

Mayors cite heavy economic damage from prolonged shutdown.

Most Read