greenhouse gas emissions in 2001 consisted of 1,579 mmtce
of CO [subscript]2 (84% of total emissions), 176 mmtce
of methane (9% of total emissions), 98 mmtce
of nitrous oxide (5% of total emissions), and 31 mmtce
of hydrofluorocarbons (HFCs), perfluorcarbons (PFCs), and sulfur hexafluoride (SF6) (2% of total emissions).
emissions of GHGs in the range of 1442 MMTCE (9.8%) or 1666 MMTCE (8.5%).
farming activities Emissions from all United States 5287 31 0.471 sources (MMT of gas) Emissions from United States 157 * 9 0.174 agriculture (MMT of gas) Global warming potential (100 1 21 310 years relative to C[0.sub.2]) Global warming potential from: Emissions from all United States 1442 178 39 sources (MMTCE) Emissions from United States 42.9 * 52 14 agriculture (MMTCE) MMTCE = million metric tons of carbon equivalent Data in Table 1 are adapted from DOE/EIA (3) * As per calculations made in this report.
agricultural activities totaled 120 MMTCE, expressed in terms of carbon-equivalent units, and accounted for 6% of the total GHG emissions in the United States (Table 1).
During the last few years, EPA's estimates of C[O.sub.2] emissions from on-farm fossil fuel and mobile combustion averaged about 14 MMTCE per year (14) (Table 1).
In 2004, carbon sequestration by agricultural soils was estimated at 12.4 MMTCE. Compared to estimates for the most recent five-year average, estimates for 2004 show possible gains in carbon uptake and storage in recent years.
agricultural lands will nearly double from current levels by 2012, adding roughly an additional 11 MMTCE of sequestered carbon attributable to the sector.
Other longer term estimates from USDA report the potential for net increases in carbon sequestration ranging from 10 to 160 MMTCE per year in the United States, or roughly 2-14 times current levels.
Under USDA's forecast, an additional carbon uptake of 160 MMTCE per year would more than offset the agriculture sectors' annual GHG emissions, or offset 8% of total national emissions from all sources.
USDA's forecast of an additional sequestration potential of 10-160 MMTCE is associated with an estimated annual value ranging from $10/mt to $125/mt of carbon permanently sequestered.
agricultural agriculture's activities totaled 120 MMTCE (million metric tons share of annual of carbon equivalent units), accounting for 6% of national GHG the annual national GHG emissions (Table 1).