Crops need nutrients, such as nitrogen, to grow. Growers use fertilizers to supply nutrients to plants, but the use of conventional fast-release fertilizers has economic and environmental consequences. Of the amount of nitrogen currently applied worldwide, plants take up only about half. The other half is wasted and is either leached out of soil into surface and ground waters, affecting the drinking water and ecosystems downstream, or released to the atmosphere in a gaseous form. One of the gases emitted is nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide. It accounts for 80% of the carbon footprint of conventional nitrogen fertilizer. To reduce these nutrient losses, growers can apply smaller dosages throughout the growing season, apply nitrification inhibitors, or use controlled- release fertilizers that avoid the formation of excess soluble nitrogen in soil.

Researchers at Pacific Northwest National Laboratory have invented a new fertilizer composition that releases nitrogen at a controlled rate over a selected time period. It is based on slowly soluble solid-nitride compounds, rather than highly soluble ammonium salts, as the source of nitrogen. By blending in other materials, such as starch and potassium phosphates, they can tailor the nitrogen-release rate of the mixture. All the materials are combined and transformed into porous granules. This engineered form allows for easy absorption of water and release of nitrogen as ammonium ions. The result maximizes the amount of nitrogen consumed by the plant and minimizes the "wasted" fertilizer that can be leached to waterways or converted to nitrous oxide.

A variety of oxide-bearing materials, including bauxites, clay minerals, and a coal-combustion byproduct called fly ash, can serve as feedstocks for the solid nitride. To date, the PNNL-developed method has focused on the use of coal fly ash. About half of the fly ash generated ends up buried in landfills or storage ponds. Finding a new use for this byproduct to create a fertilizer that increases the efficiency of delivering nutrients thus benefits the environment in more than one way.