One of Seattle’s oldest companies is also one of the city’s biggest polluters.
For those crossing the Duwamish River on the West Seattle Bridge, the Ash Grove Cement Plant is a must-see.
Two giant concrete domes and eight tall silos jut out above low-slung warehouses in Seattle’s industrial Sodor district. Small hills made of limestone, gypsum, and other raw materials pushed down from Canada line the river. The plant’s 27-story cooling tower is adorned with illuminated American flags, dwarfing even the silos.
Beneath the cooling tower, a giant cylindrical kiln rotates on its side like a giant rolling pin, the inside of which heats up to 3,000 degrees Fahrenheit.
Every day, the factory burns natural gas and thousands of old tires as fuel to heat the kilns and turn limestone into clinker, the main ingredient in cement.
The Ash Grove Cement Plant has stood on the banks of the Duwamish River for nearly a century. The company makes about one-third of Washington’s cement, which is used to make concrete for highways, buildings and other critical infrastructure.
In recent years, community groups in the area have clashed with the factory over air pollution.
In November, the Duwamish River Community Coalition held a protest in front of the offices of the Puget Sound Clean Air Agency.
“No more burning, no more fires. Let’s protect our children from harmful tires,” protesters chanted.
According to several studies, the Duwamish Valley has one of the highest rates of childhood asthma in the region and has one of the worst air pollution.
Activists were hoping to influence the agency’s impending decision on Ash Grove’s five-year-old request to increase tire combustion beyond 30% of fuel supply.
The plant currently burns 1.2 million tires a year.
“We know tires are bad for the air, for air pollution,” said Mia Ayala Marshall, clean air program manager for the Duwamish River Community Coalition. “(Burning tires) can release toxic pollutants such as dioxins, furans and mercury, which are very harmful to human health. They are cancerous. They can cause respiratory and cardiovascular problems.”
In December, the Japan Civil Aviation Agency granted the company permission to increase the amount of tires it burns to 37% of its fuel supply.
The regional aviation authority has found that burning tires at very high temperatures in cement kilns does not increase pollution.
Environmentalists appealed the decision in January, calling it arbitrary and capricious.
Phyllis McElroy, a spokeswoman for the Puget Sound Clean Air Agency, declined an interview request, saying she is not authorized to give media interviews while the agency’s decision is being appealed.
Before the appeal against Ash Grove’s permit was filed, Mr. McElroy issued a written statement.
“The agency remains committed to protecting air quality and complying with all regulations,” McElroy said in an email.
“The proposed changes are not expected to increase emissions and could reduce some pollutants by reducing the use of natural gas,” McElroy said.
The agency’s conclusions are based on studies of cement kilns that burn both coal and natural gas, the dirtiest fossil fuels. Ash Grove’s Seattle plant has not used coal in 10 years.
The U.S. Environmental Protection Agency also has jurisdiction over emissions from factories. Under President Donald Trump, federal agencies, focused on deregulation and “energy dominance,” have refused to review the decision.
Air pollution is a major concern in the Duwamish Valley region, which has twice the poverty rate as Seattle and whose residents are mostly people of color.
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A study released Thursday by the Washington Department of Ecology found that south Seattle (the area surrounding the Duwamish Valley) is “heavily affected by air pollution.” The authors attributed the 57 annual deaths in the region to elevated levels of soot-like particles in the air.
“We estimate that the 57 deaths would not have occurred if contamination levels had reached baseline levels,” lead author Kirsten Dodrow said in an email.
Ash Grove is one of many sources of pollution south of Seattle. It’s also one of the biggest.
Ash Grove spokeswoman Carolina Lucaroni declined repeated requests for factory tours and interviews, but did respond to a list of written questions. Using tires as fuel is “best practice” in the cement industry and supports a circular economy, she said.
“These alternative fuel sources (tires) allow cement plants to benefit by utilizing locally available materials that would otherwise be sent to landfills, illegally dumped, or exported for disposal in developing countries,” Lucaroni said in an email.
Using tires as fuel reduces the amount of natural gas burned in factories, which also reduces the impact on climate change, she said.
According to the American Tire Manufacturers Association, approximately 300 million used tires will be discarded in the United States in 2023, and 84 million of them will be burned as fuel in cement kilns, pulp mills, and power plants.
Nationally, the cement industry derives about 15% of its energy from tires. In Seattle’s Ash Grove, tires are burning at twice that rate.
Lucaroni said cement kilns have been safely using tires as fuel for 40 years, and the industry plans to source 43% of its fuel supply from “alternative fuels” such as old tires by 2050.
Cement is an essential component of basic infrastructure, but its production is extremely harmful to the climate.
According to the World Cement and Concrete Association, the cement industry is responsible for 7% of global carbon emissions. In addition to the fossil fuels burned to make cement, the high-temperature chemical transformation of limestone into clinker produces large amounts of carbon dioxide, which warms the planet.
Ashgrove’s Seattle plant is the largest source of carbon dioxide emissions in King County, according to the U.S. Environmental Protection Agency, and the largest source of unhealthy nitrogen oxides, carbon monoxide and ammonia, according to the Washington Department of Ecology.
It is the second-largest source of particulates and sulfur dioxide after the Ardagh Glass Packaging factory one mile south.
“The Duwamish Valley experiences cumulative pollution from international airports, railroads, ports, and all industries,” Ayala Marshall said. “Increasing emissions in communities already plagued by air pollution is unacceptable.”
The Ashgrove plant currently operates under a 20-year-old air pollution permit.
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The Puget Sound Clean Air Authority is proposing to update its permit to meet new federal standards.
It also asked Ash Grove to test for emissions of particulates, dioxins and heavy metals like arsenic and lead to determine whether increased tire burning is polluting the air in the Duwamish Valley.
“Ash Grove is committed to being a good neighbor and has consistently invested in ensuring compliance with relevant permitting, environmental, health, safety and other regulatory requirements at our Seattle facility,” Lucaroni said in an emailed statement.
“Ash Grove is a notorious neighbor in the Duwamish Valley,” Ayala Marshall said.
She pointed to the company’s previous lawsuits against the EPA, ongoing consent decrees and, by her count, 51 air pollution permit violations over a 10-year period.
Although KUOW cannot confirm the number of permit violations, the Puget Sound Clean Air Agency has issued 10 dust-related permit violations to Ash Grove over the past five years after neighbors complained of clinker particles on the property.
A public hearing on an environmental group’s appeal to reduce the number of tire burns in Ash Grove is not scheduled to be held at the state’s Pollution Control Board until 2027.
