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Energy's Future

Utah State University biochemist Lance Seefeldt, pushing a shopping cart groaning with 50-pound bags of sugar, drew curious stares from fellow shoppers as he approached the checkout counter at a local Walmart.

“The clerk commented, ‘You must have big baking plans,’” says Seefeldt, professor in the Department of Chemistry and Biochemistry. “I think one of her co-workers suspected I was making alcohol. We shared a laugh and I explained my purchases were for my biochemistry research.”

Attracting a small gathering of attentive listeners, the unassuming scientist briefly described his work in exploring how nitrogen is converted to a life-sustaining compound essential to our survival.

“It was great to have an impromptu opportunity to talk about science,” he says. “Everyone was genuinely interested.” The well-stocked shelves of a supermarket couldn’t have been a more appropriate place to discuss nitrogen fixation, the chemical process by which atmospheric nitrogen, known as dinitrogen, is converted into ammonia.

“We live in a sea of nitrogen, yet our bodies can’t access it from the air,” says Seefeldt, an American Association for the Advancement of Science Fellow and 2012 recipient of USU’s D. Wynne Thorne Career Research Award. “Instead, we get this essential element from protein in our food.”

The world currently depends on only two known processes to break dinitrogen’s ultra-strong bonds and allow conversion to a form humans, animals and plants can consume. One is the natural, bacterial process on which farmers have relied since the dawn of agriculture. The other is the century-old HaberBösch process, which revolutionized fertilizer production, spurred unprecedented growth of the global food supply and makes it possible for shoppers, like Seefeldt, to choose from a dazzling selection of groceries at their neighborhood market.

Seedfeldt Lab

Haber-Bösch, developed by German chemists Franz Haber and Carl Bösch as World War I raged, enabled industrial-scale fertilizer production and now sustains most of the world’s population – but at a high environmental cost.

“Haber-Bösch currently consumes about two percent of the world’s fossil fuel supply,” Seefeldt says. “Any way you slice it, nitrogen fixation, the process of converting dinitrogen to ammonia, is an energy-intensive process.”

He’s studied nitrogenases, the bacterial enzymes responsible for nitrogen fixation, for more than 20 years and, with his students and colleagues recently reported a breakthrough with a light-driven process that could, once again, revolutionize agriculture. The research, reported in the journal Science in April 2016, demonstrates how photochemical energy can replace adenosine triphosphate, which is typically used to convert dinitrogen in the air to ammonia for fertilizer.

Seefeldt says the new process, which uses nanomaterials to capture light energy that can power nitrogen fixation, could be a “game-changer” by reducing the world’s food supply’s dependence on fossil fuels and relieving Haber-Bösch’s heavy carbon footprint

Energy-efficient production of ammonia holds promise not only for food production, but also for development of technologies that enable use of environmentally cleaner alternative fuels, including improved fuel cells to store solar energy.

Seefeldt’s work on the project is part of a seven-institution team that was one of 32 projects selected nationally for the U.S. Department of Energy’s Energy Frontier Research Center grant program aimed at accelerating scientific breakthroughs needed to build a new energy economy, then-DOE Secretary Ernest Moniz announced the awards in June 2014. DOE secretary Ernest Moniz announced the awards in June 2014.

Known as the Center for Biological Electron Transfer and Catalysis – BETCy, for short – the team, which includes USU, Montana State University, University of Georgia, University of Washington, Arizona State University, the University of Kentucky and the Golden, Colorado-based National Renewable Energy Lab, received a fouryear, $10 million grant.

SEEKING A BIGGER PICTURE, ADVANCING ALTERNATIVE ENERGY

Seefeldt’s journey to this point is built on years of careful deciphering of the intricate chemical and mechanical steps of the nitrogen fixation process.

“The structure of nitrogenases and the general site at which nitrogen gets bound and reduced has been known for about 20 years,” he says. “We’ve been working to establish the bigger picture: the mechanistic pathway by which this process takes place.”

To identify the process, Seefeldt, with his students and colleagues, developed and refined a chemical methodology to trap and detect intermediates in nitrogen-catalyzed reductions and flash-freeze samples.

Brett Barney, a former USU postdoctoral fellow who worked with Seefeldt and is now a faculty member at the University of Minnesota, likens the effort to capturing single frames of a movie on a moving film reel.

“You have to capture each step of the process in the act and freeze the frame, so you can actually examine it and understand what it does,” he says.

Zhi-Zong Yang, a recent doctoral graduate from Seefeldt’s lab, says the team now has the whole “reel” and is working to define each frame of the “movie.”

Armed with this knowledge, Yang and Seefeldt, along with colleagues at Virginia Tech and Brazil’s Federal University of Paraná, used genetic engineering to remodel a nitrogenase and enable it to convert carbon dioxide into methane.

“We took a greenhouse gas and converted it to fuel,” Seefeldt says. “That’s a step toward a current ‘holy grail’ of science. Imagine the far-reaching benefits of capturing environmentally damaging byproducts of burning fossil fuels and using them to make alternative fuels.”

Further research led to discovery of a molybdenum nitrogenase capable of converting carbon monoxide into usable hydrocarbons. The reaction is similar, they say, to another early 20th century discovery known as FischerTropsch or “FT” synthesis.

Stinging from humiliating defeat in World War I, Germany’s Nazi regime seized on the FT synthesis technology developed by chemists Franz Fischer and Hans Tropsch that enabled the coal-rich, petroleum-poor country to produce synthetic fuels for its military machine. Research on the technology waned in the latter half of the 20th century but, like “a bubblin’ crude,” has resurfaced in recent years with growing interest in alternative fuels.

“There’s tremendous interest in converting various kinds of waste into fuel and, especially, in finding cost-effective and environmentally clean ways to do it,” says Yang, who earned his first doctorate in organic chemistry at China’s Nankai University.

Unlike coal, Fischer and Tropsch’s source for synthetic fuels, carbon monoxide produces hydrocarbons with much less pollution. The substance provides an added benefit: it allows scientists to produce longer chain, double and triplebond hydrocarbons, which provides a richer feedstock for production of refined transportation fuels.

“Like many waste-to-energy processes, we’ve found we can produce such hydrocarbons as propane and butane from carbon monoxide,” Yang says. “But using this process, we may also have the potential to produce transportation fuels like diesel and gasoline that are readily adaptable to today’s vehicles.”

“This is pretty profound,” Seefeldt says. “Understanding this process paves the way of converting carbon monoxide, a toxic waste product of combustion, into transportation fuel and precursors for plastics without the time and energy required for conventional extraction of fossil fuels.”

The team reported a yet another breakthrough – the use of a phototropic bacterium as a biocatalyst to generate methane from carbon dioxide in one enzymatic step – in the August 22, 2016 Early Edition of the Proceedings of the National Academy of Sciences.

“It’s a baby step, but it’s also a big step,” Seefeldt says.

“Imagine the far-reaching benefits of large-scale capture of environmentally damaging byproducts from burning fossil fuels and converting them to alternative fuels using light, which is abundant and clean.”

 

—Mary-Ann Muffoletto