Counting carbon on the farm: Reaping the benefits of carbon offset programs

Excerpt

Reducing anthropogenic greenhouse gas (GHG) emissions is the greatest environmental challenge facing society over the coming decades (NAS 2005). Although the largest global source of emission stems from the use of fossil fuels, land use, including agriculture, is the second greatest contributor to increasing GHG concentrations in the atmosphere, accounting for about 30% of total net emissions (IPCC 2007). The majority of these land use emissions are associated with deforestation and land conversion, mainly in the tropics; however, in the United States, agriculture contributes around 7% of total emissions (EPA 2007). The three main GHGs of concern—carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)—are all emitted through various agricultural activities, with the CH₄ and N₂O dominating agricultural emissions in the United States. However, agriculture has the capacity to not only significantly reduce its own emissions, but also to offset CO₂ emissions from other sectors of the economy via carbon sequestration (CAST 2004; Paustian et al. 2006). By employing practices that increase organic matter content (about half of which is carbon) of soils, it is estimated that as much as 50 to 200 million t C per year of carbon offsets could be produced by US agriculture (Lal et al.…