Scientists make fertilizer using the power of the sun

GOLDEN, Colo., April 21 (UPI) -- A group of scientists in Colorado have found a way to use the sun's rays to synthesize ammonia, the key ingredient in fertilizer.

Currently, there are two main ways to turn nitrogen into ammonia, or NH3, a compound of nitrogen and hydrogen. The first is biological. Bacteria found in the roots of legumes and other plants use a protein called nitrogenase to turn nitrogen into ammonia. The second is an industrial process that involves a series of chemical reactions triggered using high temperatures and pressure.

Scientists at the U.S. Department of Energy's National Renewable Energy Laboratory in Golden, Colorado -- with help from researchers at the University of Colorado, Boulder -- came up with a synthesis process that harnesses the biochemical potential of nitrogenase, but for industrial production.

The researchers combined nitrogenase with nanocrystals of the compound cadmium sulfide, which can absorb and harvest sunlight. The harvested light excite electrons in the nanocrystal, triggering the conversion of N2 into NH3.

Researchers detailed their new synthesizing technique in the journal Science.

"The key was to combine semiconductor nanocrystals that absorb light with nitrogenase, nature's catalyst that converts nitrogen to ammonia," co-author Gordana Dukovic, a professor of biochemistry at Boulder, said in a news release. "By integrating nanoscience and biochemistry, we have created a new, more sustainable method for this age-old reaction."

Currently, fertilizer production is an energy-intensive process that relies heavily on fossil fuels. The latest findings could encourage more sustainable processes.

"Using light harvesting to drive difficult catalytic reactions has the potential to create new, more efficient chemical and fuel production technologies," added Katherine Brown, a research scientist at NREL. "This new ammonia-producing process is the first example of how light energy can be directly coupled to enzymatic N2 reduction, meaning sunlight or artificial light can power the reaction."