seeing green

Houston lab develops reactor that sustainably turns waste into ammonia

Led by Haotian Wang (left) and Feng-Yang Chen, the Rice University team published a study this month detailing how its reactor system sustainably converts waste into ammonia. Photo by Jeff Fitlow/Rice University

A team of Rice University engineers has developed a reactor design that can decarbonize ammonia production, produce clean water and potentially have applications in further research into other eco-friendly chemical processes.

Led by Rice associate professor Haotian Wang, the team published a study this month in the journal Nature Catalysis that details how the new reactor system sustainably and efficiently converts nitrates (common pollutants found in industrial wastewater and agricultural runoff) into ammonia, according to the university. The research was supported by Rice and the National Science Foundation.

“Our findings suggest a new, greener method of addressing both water pollution and ammonia production, which could influence how industries and communities handle these challenges,” Wang says in a statement. “If we want to decarbonize the grid and reach net-zero goals by 2050, there is an urgent need to develop alternative ways to produce ammonia sustainably.”

Other methods of creating ammonia include the Haber-Bosh process and electrochemical synthesis. The Haber-Bosh process requires large-scale centralized infrastructure and high temperature and pressure conditions. Meanwhile, electrochemical synthesis requires a high concentration of additive chemicals.

According to Rice, the new reactor requires less additive chemicals than the electrochemical synthesis, allowing nitrates to be converted more sustainably. The reactor relies on an innovative porous solid electrolyte as well as recyclable ions and a three-chamber system to improve the reaction’s efficiency.

Additionally, this development provides an effective water decontamination method.

“We conducted experiments where we flowed nitrate-contaminated water through this reactor and measured the amount of ammonia produced and the purity of the treated water,” Feng-Yang Chen, a Rice graduate student who is the lead author on the study, says. “We discovered that our novel reactor system could turn nitrate-contaminated water into pure ammonia and clean water very efficiently, without the need for extra chemicals. In simple terms, you put wastewater in, and you get pure ammonia and purified water out.”

Pedro Alvarez, the George R. Brown Professor of Civil and Environmental Engineering, director of the Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT) and the Water Technologies Entrepreneurship and Research (WaTER) Institute at Rice, says the reactor is "very timely and important" for growing cities that must deal with nitrate-contaminated groundwater supplies it.

"Conventional nitrate removal in drinking water treatment involves ion exchange or membrane filtration by reverse osmosis, which generates brines and transfers the nitrate problem from one phase to another,” he continues.

Wang's lab has been making headlines in recent years for innovative processes and technologies focused on the energy transition.

Last year, the lab published a study in Nature detailing a new technology that uses electricity to remove carbon dioxide from air capture to induce a water-and-oxygen-based electrochemical reaction, generating between 10 to 25 liters of high-purity carbon using only the power of a standard lightbulb.

In 2022, Rice reported that Wang’s lab in the George R. Brown School of Engineering had also replaced rare, expensive iridium with ruthenium, a more abundant precious metal, as the positive-electrode catalyst in a reactor that splits water into hydrogen and oxygen.

The lab received a portion of $10.8 million in research grants from the Houston-based Welch Foundation for research focused on converting carbon dioxide into useful chemicals, such as ethanol, last year. And Solidec, founded by Ryan Duchanois and Yang Xia from Wang's Lab, also received a $100,000 award from Rice as part of the One Small Step Grant program.

Wang has also been named among one of the most-cited researchers in the world.

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A View From HETI

Thanks to a new partnership, Engie North America plans to add 'precycling' provisions to power purchase agreements on projects in the Midwest. Photo via Getting Images.

Houston-based Engie North America has partnered with Arizona-based Solarcycle to recycle 1 million solar panels on forthcoming projects with a goal of achieving project circularity.

The collaboration allows Engie to incorporate "precycling" provisions into power purchase agreements made on 375 megawatts worth of projects in the Midwest, which are expected to be completed in the next few years, according to a news release from Engie.

Engie will use Solarcycle's advanced tracking capabilities to ensure that every panel on the selected projects is recycled once it reaches its end of life, and that the recovered materials are returned to the supply chain.

Additionally, all construction waste and system components for the selected projects will be recycled "to the maximum degree possible," according to Engie.

“We are delighted to bring this innovative approach to life. Our collaboration with Solarcycle demonstrates the shared commitment we have to the long-term sustainability of our industry,” Caroline Mead, SVP power marketing at ENGIE North America, said in the release.

Solarcyle, which repairs, refurbishes, reuses and recycles solar power systems, estimates that the collaboration and new provisions will help divert 48 million pounds of material from landfills and avoid 33,000 tons of carbon emissions.

“ENGIE’s precycling provision sets a new precedent for the utility-scale solar industry by proving that circular economy principles can be achieved without complex regulatory intervention and in a way that doesn’t require an up-front payment," Jesse Simons, co-founder and chief commercial officer at SOLARCYCLE, added in the release. "We’re happy to work creatively with leaders like ENGIE to support their commitment to circularity, domestic energy, and sustainability.”

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