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Curbing climate change goes hand-in-hand with decarbonizing energy production. But how can communities continue to meet the global demand for electricity without releasing more CO 2 ? A cadre of chemists says one solution may be hiding in an unlikely source: ammonia-the pungent, clear, nitrogen-rich gas, or liquid, that's most often used as an agricultural fertilizer. Most of the ammonia produced in the world goes to crops, with the rest ending up in plastics, explosives, fabrics, and other materials.But to researchers looking for carbon-neutral energy, ammonia makes an appealing fuel. Made of nitrogen and hydrogen, it burns without releasing carbon. [In 2014, Japanese researchers unveiled the first turbine powered by ammonia combustion (1).] Ammonia is also appealing as a way to store energy that's transported from where it's made to where it's needed. And some researchers say that ammonia could be used to package and store hydrogen, which could be readily cracked out of the liquid or gas and used in fuel cells.And yet, several challenges remain if ammonia is to help with the globe's massive carbon emissions conundrum. The conventional process for making ammonia involves liberating hydrogen from the hydrocarbons in fossil fuels, often methane, which adds CO 2 to the atmosphere. By some estimates, ammonia production is responsible for roughly 2% of fossil fuel use, worldwide, and releases more than 400 millions of tons of CO 2 , representing more than 1% of total annual global emissions of the Ammonia is appealing as a means of storing and transporting energy, and it could offer a way to package and store hydrogen. But the conventional process for making ammonia at plants like this one involves liberating hydrogen from the hydrocarbons in fossil fuels and hence results in CO 2 emissions. Image credit: Shutterstock/saoirse2013.

The author notes that on page 9188, right column, second full paragraph, lines 4−8, "Heaters both above and below groundextending down 3 meters (9.8 feet)-will warm the air and soil of some enclosures up to 9°C, or about 42°F, above ambient." should instead appear as "Heaters both above and below groundextending down 3 meters (9.8 feet)-will warm the air and soil of some enclosures up to 9°C, or about 16.2°F, above ambient."

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