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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Houston ranks No. 99 out of 100 on new report of greenest U.S. cities

Sustainability Slide

Houstonians may be feeling blue about a new ranking of the greenest cities in the U.S.

Among the country’s 100 largest cities based on population, Houston ranks 99th across 28 key indicators of “green” living in a new study from personal finance website WalletHub. The only city with a lower ranking is Glendale, Arizona. Last year, Houston landed at No. 98 on the WalletHub list.

“‘Green’ living means a choice to engage in cleaner, more sustainable habits in order to preserve the planet as much as possible,” WalletHub says.

Among the study’s ranking factors are the amount of greenhouse gas emissions per capita, the number of “smart energy” policies, and the presence of “green job” programs.

In the study, Houston received an overall score of 35.64 out of 100. WalletHub put its findings into four buckets, with Houston ranked 100th in the environment and transportation categories, 56th in the lifestyle and policy category, and 52nd in the energy sources category.

In the environment category, Houston has two big strikes against it. The metro area ranks among the 10 worst places for ozone pollution (No. 7) and year-round particle pollution (No. 8), according to the American Lung Association’s 2025 list of the most polluted cities.

In the WalletHub study, San Jose, California, earns the honor of being the country’s greenest city. It’s followed by Washington, D.C.; Oakland, California; Irvine, California; and San Francisco.

“There are plenty of things that individuals can do to adopt a green lifestyle, from recycling to sharing rides to installing solar panels on their homes,” WalletHub analyst Chip Lupo said in the report. “However, living in one of the greenest cities can make it even easier to care for the environment, due to sustainable laws and policies, access to locally grown produce, and infrastructure that allows residents to use vehicles less often. The greenest cities also are better for your health due to superior air and water quality.”

Greentown to add new Houston AI lab from latest Houston partner

AI partnership

Greentown Labs has partnered with Shoreless to launch an AI lab within its Houston climatetech incubator.

"Climatetech and energy startups are transforming industries, and AI is a critical tool in that journey," Lawson Gow, Greentown's Head of Houston, said in a news release. "We're excited to bring this new offering to our entrepreneurs and corporate partners to enhance the way they think about reducing costs and emissions across the value chain."

Shoreless, a Houston-based company that enables AI adoption for enterprise systems, will support startups developing solutions for supply-chain optimization and decarbonization. They will offer Greentown members climate sprint sessions that will deliver AI-driven insights to assist companies in reducing Scope 3 emissions, driving new revenue streams and lowering expenses. Additionally, the lab will help companies test their ideas before attempting to scale them globally.

"The future of climatetech is intertwined with the future of AI," Ken Myers, Founder and CEO of Shoreless, said in a news release."By launching this AI lab with Greentown Labs, we are creating a collaborative ecosystem where innovation can flourish. Our agentic AI is designed to help companies make a real difference, and we are excited to see the groundbreaking solutions that will emerge from this partnership."

Greentown and Shoreless will collaborate on workshops that address industry needs for technical teams, and Shoreless will also work to provide engagement opportunities and tailored workshops for Greentown’s startups and residents. Interested companies can inquire here.

Recently, Greentown Labs also partnered with Los Angeles-based software development firm Nominal to launch the new Industrial Center of Excellence at Greentown's Houston incubator. It also announced a partnership with Houston-based EnergyTech Nexus, which will also open an investor lounge on-site last month. Read more here.