IN the quest to decrease the level of greenhouse gases, researchers at Cornell University have discovered that biochar — a charcoal-like substance — reduces nitrous oxide emissions from agricultural soil by about 55% on average and stanches emissions into the atmosphere.
"We investigated the mechanics of denitrification, with particular attention to the climate-relevant nitrous oxide, by adding biochar to agricultural soils," senior author Johannes Lehmann, Cornell professor of soil science, said. "Biochar consistently reduced nitrous oxide emissions in agricultural soils."
On farms, nitrous oxide gas is usually produced from animal manure and the use of synthetic fertilizer. Nitrous oxide in agricultural soil has 298 times more global warming potential than carbon dioxide — "hence the importance to reduce emissions," Lehmann said.
Agriculture accounted for almost 58% of all nitrous oxide emissions in the U.S. from 2003 to 2007 and almost 59% from 2008 to 2012, according to World Bank data cited in the announcement. Generally, about 60% of all global nitrous oxide emissions come from agriculture, and about half of agricultural greenhouse gas emissions come from nitrous oxide.
"Despite this large importance of nitrous oxide for greenhouse gas emissions, there are very few strategies to mitigate the emissions in agriculture compared to carbon sequestration in soils," Lehmann said.
Maria Luz Cayuela, a former Cornell post-doctoral researcher in Lehmann's lab who is now at the Universidad de Murcia in Spain, led the study. The soils and biochar studied spanned a wide array of types, including soils that were acidic, neutral, sandy, filled with clay, rich in organic carbon or possessing low carbon amounts.
No matter the soil or biochar type used, the researchers found that the emission of nitrous oxide was always reduced, on average, by about 55% compared to benign nitrogen gas.
The study, "Biochar & Denitrification in Soils: When, How Much & Why Does Biochar Reduce N2O Emissions," was published April 25 in Scientific Reports, a new journal from Nature and was co-authored by Universidad de Murcia researchers Miguel Angel Sanchez-Monedero and Asuncion Roig and Cornell technicians Kelly Hanley and Akio Enders.