Turning NM coal ash into green products

A Canadian company wants to turn San Juan County into a manufacturing hub for “green cement” by recycling coal ash with innovative clean- processing technology.

Its operations could help clean up hundreds of millions of tons of legacy coal ash created by decades of coal-fired generation that’s now scattered in ponds, landfills and mines around the Four Corners.

In the SonoAsh “sonicator” reactor, magnets on both sides of the machine cause the metal bar in the center to vibrate. That resonates into round chambers at both ends of the bar, fracturing piles of coal ash placed in the chambers. (Courtesy of Sonoash)

Simultaneously, SonoAsh LLC’s clean-processing technology could create a new domestic source of rare earth elements and critical minerals used to make everything from solar panels and wind turbines to magnets, batteries, computer chips and most consumer electronics.

That prospect got a significant boost in late April from the U.S. Department of Energy, which approved a $1.48 million grant to research the potential for extracting rare earth elements from coal waste. The grant, to be awarded to the New Mexico Institute for Mining and Technology, will bring SonoAsh into a collaborative partnership with the Socorro-based research university, San Juan College, and the state’s two national labs.

Brad MacKenzie, SonoAsh managing partner and vice president for business operations, said the company is ready to move forward on commercial launch of its first green cement operation in San Juan County after more than a decade of research and development to build its patented clean-processing technology.

“This is really an opportunity for a new green industry to emerge in San Juan County,” MacKenzie told the Journal. “There’s been a lot of concern about the

Silica powder is one of the products SonoAsh will produce from coal ash to be used as an added ingredient to strengthen cement.

economic impacts of closing the coal generating plants here. This is an opportunity to build on the coal legacy by creating a next-generation industry that will require generations of work to process all this coal ash.”

SonoAsh is one of a number of projects emerging in the Four Corners that build on the region’s natural assets, and on the industrial infrastructure left behind by the fossil fuel industry, as the transition to a clean-energy economy accelerates in New Mexico and elsewhere.

Hydrogen project

Others are working to convert San Juan County into a hydrogen production hub.

One company, the Libertad Power Project, wants to build a hydrogen-fueled generating plant to supply electricity to utilities in the Southwest. It would convert methane from natural gas into clean-burning hydrogen to run turbines while capturing carbon dioxide from the methane for underground storage in geological formations in the San Juan Basin. That project would eventually transition to carbon-free, “green-hydrogen” production using renewable generation from wind and solar plants to extract hydrogen from water.

Conversion plans

Two other companies are looking to potentially convert the coal-fired Escalante Generating Station near Grants – which Tri-State Generation and Transmission Association shut down last year – into a hydrogen production and generating facility.

And another company, Enchant Energy, is working to turn the San Juan Generating Station near Farmington into the world’s largest carbon-capture project to keep the plant operating after Public Service Co. of New Mexico and other utility co-owners abandon the facility next year.


Some of those endeavors are highly controversial, particularly the Enchant Energy project, which environmental groups oppose because it would prolong coal mining and coal-fired generation in the region instead of aggressively pursuing renewable energy development.

The hydrogen operations as well could encounter environmental pushback since they would start out using natural gas, not renewables, to produce hydrogen, even if they later transition to renewable-based “green-hydrogen” production.

And while most of the technology behind those operations is already proven, it remains to be seen if the proposed projects can become economically and commercially viable.

Coal ash details

The coal ash recycling operation, however, is considerably advanced and more likely to garner support from environmentalists and others, since it offers significant benefits with few, if any, adverse impacts.

New Mexico Tech is not involved with the green cement side of SonoAsh’s goals. But the effort to extract rare earth elements from coal ash, if successful, would be a win-win for New Mexico and the country in general, said Virginia McLemore, an economic geologist with the New Mexico Bureau of Geology, run by the university, and one of the principal investigators on the DOE project.

“We’ll sample coal mine wastes to see if there is potential for extracting rare earth elements and critical minerals,” McLemore told the Journal. “And if that is possible, then there’s potential as well to clean up some of these mine wastes.”

SonoAsh’s “sonicator” reactor is enclosed in a sound-proof box. The full system will be installed this year in a new Center of Excellence that the company is building at San Juan College in Farmington.

The New Mexico Tech grant is one of 13 research projects the DOE funded in April with $19 million in federal awards to investigate critical mineral production at current and former coal producing regions across the U.S. It’s part of a renewed federal push to develop a secure, sustainable, domestic supply of those minerals to offset dependence on foreign imports from places that may at some point endanger the supply chain, which is critical to the U.S. economy, both for industrial production and national defense.

About 90% of the U.S. supply of rare earth elements, which encompass 17 elements on the periodic table, currently come from China, making the U.S. particularly vulnerable to supply interruptions. And as the transition to a non-carbon economy accelerates under President Joe Biden, secure supply chains become even more essential, since those elements are a fundamental part of the components for much of today’s renewable technologies.

Focusing on production from coal mines and waste products has the added advantage of potentially creating new, good-paying jobs in places hard-hit by the move from fossil fuels to renewables, said DOE Secretary Jennifer Granholm when announcing the awards in April.

“The very same fossil fuel communities that have powered our nation for decades can be at the forefront of the clean energy economy by producing the critical minerals needed to build electric vehicles, wind turbines, and so much more,” Granholm said in a statement. “By building clean energy products here at home, we’re securing the supply chain for the innovative solutions needed to reach net-zero carbon emissions by 2050 – all while creating good-paying jobs in all parts of America.”

Two-year project

The two-year project here will look at the potential for commercially-viable production of rare earth elements and other critical minerals in coal and adjacent rock beds in the San Juan and Raton basins in northern New Mexico, McLemore said. It will also research the presence and extraction potential of those minerals in coal ash and other coal waste.

The state’s two national laboratories will participate with advanced technology to help determine the quantities of rare earth and other minerals present in the research sites and waste products, and to assess the ability to extract them from those deposits.

And San Juan College will assist in assessing the skills and knowledge needed for a future workforce to mine the minerals and then train students to meet those needs.

“We’ll help train and develop the workforce for what hopefully will be a new industry that could arise here,” said San Juan geology professor John Burris.

Why rare-earth elements?

The key to building a viable extraction operation is finding economically viable quantities of rare earth elements and critical minerals that can be commercially exploited, McLemore said. “Rare earth” is actually a misnomer, because those elements are abundantly present in many places, but not in commercial quantities.

“With these elements, we’re not talking about tonnages,” McLemore said. “We’re talking about pounds rather than tons, and that’s what makes it difficult to mine.”

Piles of rare earth elements.

That’s where coal ash and SonoAsh come in. The presence of rare earth elements in coal is well documented, and when coal is burned in power plants, the rare earth elements and other metals tend to concentrate in the waste products like coal ash, said MacKenzie of SonoAsh. The trick is to further concentrate the elements, metals and carbon into a concentrate that provides the volume of minerals needed for extraction.

The company’s clean-processing technology uses sound waves to bust up wet coal ash into two fractions – one that includes the high-carbon concentrations with rare earth elements and other metals, and the other a very low-carbon, coal-ash powder. It then uses a froth flotation process to separate the fractured ash into separate piles.

Through that process, about 25% of the ash is pushed into the high-carbon concentrate, with the other 75% resulting in a low-carbon ash pile that’s ideal for creating cement for concrete building materials.

“We’ve spent the last 10 years developing the low-frequency sound technology,” MacKenzie said. “It’s a 12-ton piece of equipment that’s basically a large steel bar with magnets. It uses sheer sonic force to separate out the waste coal ash into the two high- and low-carbon fractions.”

No-waste model

Under SonoAsh’s business model, the company would market both fractions of ash, extracting rare earth elements and other minerals from the high-carbon concentrate while using the low-carbon ash for cement and concrete products.

All of the high-carbon concentrate would eventually be used in a variety of industrial and other applications, leaving no waste product behind, MacKenzie said.

“There will be no waste left over,” he said. “We’re all about a closed-loop system where we use all of the material.”

Making lots of low-carbon green cement, however, is the central focus of SonoAsh’s business strategy. The company is focused on the Four Corners region because of the mounds of readily-available coal ash there.

New Mexico has generated in excess of 3.6 million tons per year of coal ash over 35 years, according to the U.S. Environmental Protection Agency and the DOE. The state ranks as 10th in the country for coal ash generation.

“Our real business is operating one or more green cement facilities here that will process hundreds of thousands of tons per year,” MacKenzie said. “That fraction of the coal ash is ideal for infrastructure projects. It will be a Made-in-New Mexico product for next-generation infrastructure development.”

Cement manufacturing today is based on a high-carbon industrial process that accounts for an estimated 8% of global greenhouse gas emissions. That’s because the process uses intense heat generated with fossil fuels, which accounts for about 50% of the manufacturing emissions. The other half comes from the minerals the industry uses to create the cement.

In contrast, SonoAsh’s technology uses electricity and water. The end product is a low-carbon ash that can be mixed into traditional portland cement to offset the amount of traditionally-manufactured cement to lower emissions from industrial operations, or sold directly to make concrete construction materials.

Solving a legacy problem

Apart from lowering carbon emissions in cement manufacturing, the process can help reduce coal-ash landfills.

Nationally, the number of coal-ash dumps range from about 800 to 1,400 spread across the country. They contain between 2 billion and 3 billion tons of ash, according to varying estimates by industry and environmental groups. The industry itself says more than 90% of the landfills have problems with leaching into groundwater.

“There are millions of tons of legacy ash from 50 years of power generation here in New Mexico,” MacKenzie said. “It’s a liability that’s just sitting in piles. We want to turn that liability into a set of products.”

SonoAsh envisions a network of green-cement plants in coal-producing regions across the country. But it’s first operation will be here in New Mexico, starting with a “Center of Excellence” and training facility to be located at San Juan College. That facility will be built this year, followed by a coal-ash production plant next to the San Juan Generating Station, MacKenzie said.

SonoAsh currently employs nine people in New Mexico and expects to hire another 12 this year. Once the green cement plant is up and running, it could directly employ about 110 people while indirectly supporting up to 500 local jobs.

Lisa Evans, an Earthjustice attorney and coal-ash expert, said SonoAsh’s technology seems promising, although industry innovators have been trying for years to create a clean-production process to recycle coal ash for cement materials and rare earth elements.

“The question is, can it be done technically and economically?” Evans told the Journal. “If this company can do it, it could bring employment to an area where coal plants are retiring while also providing a recycling solution for coal ash. SonoAsh is saying it has a clean-tech process to do it, and if that’s the case, it could be a significant step forward.”

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