Toward a Sustainable Society

The Dow Sustainability Innovation Student Challenge Award (SISCA) at Caltech honors students and scientists who have made significant contributions to finding sustainable solutions to the world's most pressing social, economic, and environmental problems. The award was established in 2009 by the Dow Chemical Company with the goal of promoting "forward thinking in social and environmental responsibility," according to the SISCA website. This year, graduate students Trevor Del Castillo and Niklas Thompson shared the $10,000 grand prize for their research developing a sustainable catalyst for nitrogen fixation.

Nitrogen is an abundant element crucial to many fertilizers and other chemicals produced on a large scale, but it must first be "fixed" from its inert gaseous state (N₂) into usable reactive forms such as ammonia (NH₃). The current leading process for synthesizing ammonia, the Haber-Bosch process, is expensive and energy-intense, requiring extreme temperatures and pressures (about 700 degrees Fahrenheit and 200 bars of pressure).

"From a human health perspective, fertilizer production is arguably the most important industrial chemical process that we practice," says Del Castillo. "We currently conduct this chemistry on a tremendous scale in order to feed approximately half of the global population. However, the current technology for fertilizer production is underpinned by high inputs and is hence typically practiced where fossil fuel sources are readily available and inexpensive. In addition to these energy constraints, current modes of agricultural fertilizer use are environmentally harmful and can be impractical in the developing world, where the demand for fertilizer will continue to increase moving forward."

New catalyst technologies have the potential to address this challenge. Del Castillo and Thompson—both graduate students in the laboratory of Jonas Peters, the Bren Professor of Chemistry and director of the Resnick Sustainability Institute—have studied a recently discovered catalyst system to drive nitrogen fixation, resulting in improved performance and furnishing mechanistic insights. Inspired by a family of enzymes that performs biological nitrogen fixation at room temperatures and pressures, the Peters lab has demonstrated that a simple iron compound can catalyze the fixation of nitrogen gas into ammonia at very low temperature and atmospheric pressure.

"This is a field where new technology and innovation has the potential to impact global social equity and sustainable food security while reducing environmental impact," Thompson says. "Our team's work is a small step in this context, but we ultimately hope our fundamental science discoveries will inspire more practical, sustainable technologies. In principle, nitrogen fixing catalysts can be coupled to artificial photosynthesis technologies, potentially opening the door to modular, accessible, and carbon-neutral fertilizer production."

The runners-up for the SISCA prize are Cody Finke, a graduate student, and Justin Jasper, a Resnick Sustainability Institute Prize Postdoctoral Scholar. Both work in the research group of Michael Hoffmann, the James Irvine Professor of Environmental Science, and together they have improved upon a design for a solar-powered wastewater treatment system created for toilets in the developing and developed world. Their process combines ultraviolet (UV) irradiation and electrochemical treatment to produce water suitable for reuse in agriculture and ecosystem services.

"We proposed a hybrid electrochemical-UV system that could be used to provide efficient wastewater treatment in places where water and sewer infrastructure are not available, such as parts of the developing world," Jasper says. "We were particularly excited about our research since it suggested that adding a UV step to the process significantly accelerated treatment and limited formation of disinfection byproducts that can be detrimental to human health.  Therefore, with further work, our system may be able to provide not only wastewater treatment, but also a water source for applications such as irrigation or household cleaning."