Agriculture's Role On Global Warming
Agriculture is the second largest industrial contributor to global greenhouse gases (GHGs). It's ahead of the entire transportation sector and behind only electrical and heat generation. According to the 2006 Stern Review, the earth is only capable of absorbing 5 billon MT of CO2 equivalents per year. Agriculture alone is responsible for producing 5.6 billion MT of CO2 equivalents annually.
"As reducing emissions in agriculture appears relatively difficult, and that sector accounts for more than 5 GtCO2e per year by itself already stabilization is likely.. to require complete decarbonization of all other activities..." -- 2006 Stern Review
A major contributor of GHGs produced from modern agriculture is nitrous oxide (N2O). Agriculture accounts for 84% of global N2O emissions.
Nitrous oxide has a Global Warming Potential of 296, meaning it has a global warming potential (GWP) about 300 times greater than carbon dioxide — this means that 1 pound of nitrous oxide is counted as 296 pounds of C02. Nitrous oxides stays in the atmosphere for more than 100 years.
The formation and release of N20 from agricultural fields happens when nitrogen fertilizer applied to crops interacts with common soil bacteria. It is estimated that nitrogen fertilizer accounts for one-third of the GHGs produced by agriculture (Stern Review 2006). This accounts for only GHGs released from agricultural fields; when emissions from production of nitrogen fertilizer are added, the contribution of nitrogen fertilizer is even higher.
Typically, only 30% to 50% of nitrogen fertilizer applied to crops is absorbed by the crops. A significant portion of the unabsorbed nitrogen fertilizer volatizes in the form of N2O.
If farmers had a way to use less nitrogen fertilizer yet maintain similar yields, they could both cut GHGs and reduce their operating costs. Reduced fertilizer use also means less nitrogen pollution of ground and surface waters.