Table 1.

The estimated annual greenhouse gas (GHG) emissions (kg) per animal unit month (AUM) arising from emissions of methane (CH₄) and nitrous oxide (N₂O) from enteric fermentation and manure deposition on rangelands

	CH4 emission/AUM	20 y GWP (CO2e)	100 y GWP (CO2e)	IPCC default (CO2e)
Methane emission fermentation	9.25	796	315	150
Methane emission manure	0.20	17	6.8	5.7
Total CH4 emission/AUM	9.45	813	321	156
N2O emission manure		63	70	70
Total GHG /AUM		875	391	225

GWP-20 are emissions based upon 20-year global warming potential; GWP-100 are based upon 100-year GWPs (IPCC 2013). Average methane emissions are for beef cows from USEPA (2018) except for IPCC default values which are from IPCC (2006). IPCC default values are also based upon a 100-year GWP