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

Harris County commissioners approved a plan that seeks to address issues of ecology, infrastructure, economy, community and culture. Photo via Getty Images.

Harris County commissioners approved a five-point Climate Justice Plan last month with a 3-1 vote by Harris County commissioners. The plan was created by the Office of County Administration’s Office of Sustainability and the nonprofit Coalition for Environment, Equity and Resilience.

“Climate action planning that centers on justice has the potential to spark innovative thinking and transformative actions that will lead to meaningful and just transitions in communities, policies, funding mechanisms, and implementation strategies,” the 59-page report reads.

The plan seeks to address issues relating to ecology, infrastructure, economy, community and culture. Here’s a breakdown:

Ecology

The plan will work towards clean air, water, and soil efforts that support the health of the environment, renewable energy that reduces greenhouse gases and pollution, and conservation and protection of our natural resources. Some action items include:

  • Increasing resources for local government agencies
  • Developing a free native seed bank at all libraries
  • Identifying partners and funding streams to reduce the costs of solar power for area households
  • Producing renewable energy on large tracts of land
  • Expanding tree planting by 20 percent
  • Providing tree maintenance and restoration efforts
  • Incentivizing gray water systems and filtration to conserve fresh water

Economy

In terms of the economy, the Climate Justice Plan wants the basic needs of the community met and wants to also incentivize resilience, sustainability, and climate solutions, and recycling and reuse methods. Specific actions include:

  • Quantifying the rising costs associated with climate change
  • Expanding resources and partnering with organizations to support programs that provide food, utility, housing, and direct cash assistance
  • Supporting a coalition of area non-profit organizations and county offices to strengthen social service support infrastructure
  • Supporting home repair, solar installation, and weatherization programs
  • Identify methods to expand free and efficient recycling and composting services
  • Creating a climate tax levied on greenhouse gas emissions to develop a climate fund to offset the impacts of pollution

Infrastructure

As Houston has been prone to hurricanes and flooding damage, the infrastructure portion of the plan aims to protect the region from risks through preventative floodplain and watershed management. Highlights include:

  • Investing in generators and solar power, plus battery backup and bidirectional EV charging for all county libraries
  • Providing more heating and cooling centers with charging stations
  • Coordinating and deploying community microgrids, especially in neighborhoods prone to losing power
  • Seeking partnerships and funding for low- or no-cost water purifiers for areas with the highest needs
  • Protecting the electric grid through regular maintenance and upgrading, and advocating for greater accountability and responsiveness among appointed officials
  • Developing regulations to require resilient power line infrastructure to prevent outages and failures in new developments

Community and Culture

Housing, a strong economy and access to affordable and healthy food will be achieved under the community aspect of the plan. Under culture, the plan seeks to share knowledge and build trust. Key goals include:

  • Developing a campaign to promote the use of the Harris County 311 system to identify critical community concerns
  • Supporting the development of a Community Housing Plan that ensures stable and safe housing
  • Advocating for revisions to Federal Emergency Management Agency (FEMA) disaster funding to account for renters’ losses and unmet housing needs
  • Developing and funding a whole-home program for repairs, weatherization, and solar energy
  • Developing culturally relevant public relations campaigns to increase knowledge of health, environment and biodiversity across generations
Read the full plan here.

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