The issue of greenhouse gas emissions from agriculture continues to ebb and flow. The figure below illustrates the sources of greenhouse gas emissions from agriculture in 2009, the latest year for which data/estimates exist. Agriculture emits an estimated 419.4 million metric tons (MMT) of carbon dioxide equivalent. Approximately half is from soil management (principally nitrogen fertilization), one third from enteric fermentation (principally beef and dairy digestion by-product), 1/6 from manure management (principally liquid manure storage of swine and dairy facilities) and 2% from other sources, such as rice production and field burning.
Carbon sequestration from farmland use was estimated to be over 43 MMT of carbon dioxide equivalents in 2009. Forests were estimated to sequester over 860 MMT. On the net, crop and forest production sequester greenhouse gases.
The greenhouse gas emissions debate centers around decreasing emissions from soil management and livestock production. Absent from the recent debate is talk of paying farmers for sequestering carbon.
Until 2010 the Chicago Climate Exchange offered contracts to crop and forest producers to pay for carbon sequestered via various management practices. The price for sequestered carbon dived from a high of about $7/metric ton in 2008 to near $0 in late 2009 when it became clear that no new legislation would pass to limit emissions and create a market for carbon. In 2010 the Chicago Climate Exchange ceased open trading of carbon in the U.S. The European Union continues to trade carbon but its price has fallen from a high of about $45/ton to $6/ton. The economic studies indicate that it would take at least $20/ton to induce farmers to change management in any significant way in order to collect carbon sequestration payments. Those studies were done before corn prices rose to $6/bushel. Supposedly, the carbon payments necessary to attract farmers to carbon sequestration have also risen. The conclusion: carbon sequestration payments to farmers is not likely to happen soon.
The USDA has funded several research and extension projects designed to find ways that farmers could reduce emissions. Nitrogen management is front and center in several of these projects. If successful, these projects should help producers produce more grain with less nitrogen fertilizer escaping into the environment. The good news is that this would lower production costs by reducing the cost of fertilization without reducing yields. Other research and extension projects are hoping to reduce enteric fermentation via improved feed management and reduce methane emissions via capture from manure storages. The anticipated conclusion of these USDA projects will be more efficient crop and livestock production at lower costs.
It appears that greenhouse gas emissions from agriculture are going to be reduced the manner in which they have been for the past several decades, increased productivity decreasing emissions per unit of production.
REVISED: October 2, 2015