Nitrogen Fixation Research Could Shed Light on Biological Mystery

Caltech News tagged with “energy”

Inspired by a natural process found in certain bacteria, a team of Caltech researchers is inching closer to a new method for producing fertilizer that could some day hold benefits for farmers—particularly in the developing world—while also shedding light on a biological mystery. Fertilizers are chemical sources of nutrients that are otherwise lacking in soil. Most commonly, fertilizers supply the element nitrogen, which is essential for all living things, as it is a fundamental building block of DNA, RNA, and proteins. Nitrogen gas is very abundant on Earth, making up 78 percent of our atmosphere. However, most organisms cannot use nitrogen in its gaseous form. To make nitrogen usable, it must be “fixed”—turned into a form that can enter the food chain as a nutrient. There are two primary ways that can happen, one natural and one synthetic. Nitrogen fixation occurs naturally due to the action of microbes that live in nodules on plant roots. These organisms convert nitrogen into ammonia through specialized enzymes called nitrogenases. The ammonia these nitrogen-fixing organisms create fertilizes plants that can then be consumed by animals, including humans. In a 2008 paper appearing in the journal Nature Geoscience, a team of researchers estimated that naturally fixed nitrogen provides food for roughly half of the people living on the planet. The other half of the world’s food supply is sustained through artificial nitrogen fixation and the primary method for doing this is the Haber-Bosch process, an industrial-scale reaction developed in Germany over 100 years ago. In the process, hydrogen and nitrogen gases are combined in large reaction vessels, under intense pressure and heat in the presence of a solid-state iron catalyst, to form ammonia.  “The gases are pressurized up to many hundreds of atmospheres and heated up to several hundred degrees Celsius,” says Caltech’s Ben Matson, a graduate student in the lab of Jonas C. Peters, …

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