Fertilizer manufacturers are trying to limit greenhouse gas emissions

Nitrogen-based fertilizers are essential to maintaining agricultural production at the levels needed to feed a growing world population – but they are one of the biggest contributors to global warming greenhouse gas emissions. And a comprehensive analysis In February, two researchers from the University of Cambridge, Yunhu Gao and André Cabrera Serrenho, found that synthetic fertilizers and manure produce the equivalent of about 2.6 billion tons of carbon dioxide per year. This accounts for 5 percent of global greenhouse gas emissions—more than global air and shipping combined. Surprisingly high overall results of what happens to fertilizers after they are applied, says Serrenho. Microbial activity and chemical reactions in the soil release gases – primarily nitrous oxide, which has a very strong warming effect. Each molecule of nitrous oxide is 265 times more effective than CO₂ as a greenhouse gas and lasts in the atmosphere for an average of 120 years. "Two-thirds of emissions take place in crops and fields after fertilizer application, and only one-third during the production process," adds Serrenho. "We know how to produce fertilizer with minimal emissions and we should certainly do it as quickly as possible, but we have to recognize that reducing the remaining two-thirds is mostly about changing agricultural practices." In terms of production, Norwegian agricultural giant Yara International says that since in 2005, it reduced emissions from its operations by 50 percent. The company now wants to achieve further substantial reductions in its fertilizer carbon footprint by producing ammonia – a key ingredient – with green energy.  (myFT Daily Digest, Clive Cookson)