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Page 6 of 17 Zhang et al. Carbon Footprints 2025, 4, 36 https://dx.doi.org/10.20517/cf.2025.29

Table 2. Emission factor (EF) used for the calculation of GHG emissions from yak grazing farm systems
EF kg CH Kg CH EF kg N O kg N O EF kg
Item SR -1 -1 4 -1 4 -1 -1 2 -1 -1 2 -1 References
ha year yak year ha year yak year CO -eq
2
Pasture HSR -0.30 ± 0.72 - 0.16 ± 0.04 - - [22]
(field level)
MSR -2.03 ± 0.31 - 0.26 ± 0.15 - - [22]
LSR -0.18 ± 0.44 - 0.13 ± 0.03 - - [22]
CK -1.85 ± 0.38 - 0.12 ± 0.04 - - [22]
a
Dung patches HSR 40.37 ± 2.02 0.20 ± 0.01 7.93 ± 1.04 0.04 ± 0.01 - [22]
MSR 15.93 ± 0.87 0.08 ± 0.00 15.40 ± 14.96 0.08 ± 0.07 - [22]
LSR 33.34 ± 11.73 0.17 ± 0.06 12.45 ± 4.00 0.06 ± 0.02 - [20,26]
b
Urine patches HSR -3.54 ± 0.17 -0.18 ± 0.01 5.96 ± 1.24 0.30 ± 0.06 - [20,26]
MSR -3.42 ± 0.09 -0.17 ± 0.00 11.87 ± 3.11 0.59 ± 0.15 - [20,26]
LSR -2.75 ± 0.27 -0.14 ± 0.01 14.67 ± 3.35 0.73 ± 0.17 - [22]
Manure heaps c HSR 600.35 ± 91.81 0.16 ± 0.03 14.12 ± 5.17 0.004 ± 0.003 - [22]
MSR 1,578.11 ± 240.16 0.27 ± 0.12 19.56 ± 4.02 0.003 ± 0.002 - [22]
LSR 1,983.07 ± 590.00 0.30 ± 0.14 7.50 ± 1.73 0.001 ± 0.000 - [22]
Night pens d HSR 530.45 ± 26.08 3.56 ± 1.02 85.56 ± 64.76 0.62 ± 0.63 - [22]
MSR 1,484.10 ± 331.91 4.17 ± 0.68 19.56 ± 11.77 0.06 ± 0.03 - [22]
LSR 484.39 ± 24.02 1.43 ± 0.98 70.68 ± 1.43 0.20 ± 0.13 - [22]
DM - - - - 0.85 (oxidation rate) f [23]
Yak
e
Enteric fermentation - 29.71 - - - [26]
Farm input
-1
Electricity - - - - 0.9578 kWh [27]
Gasoline for motorcycle - - - - 74,100 TJ -1 [27]

Mean ± SD (n = 3); EF: Emission factor; SR: stocking rate; HSR: high stocking rate; MSR: moderate stocking rate; LSR: low stocking rate; Fenced, no
grazing. Negative values indicate uptake and positive values indicate emission. Negative CH fluxes indicate net methane oxidation. To quantify
the various components of the system, our analysis incorporated several critical assumptions and calculation methods. Specifically, the excretion
coverage was estimated by assuming a certain daytime defecation frequency and dung patch size to determine the annual dung area per yak (a),
while the annual urine area was calculated based on the urination rate and the size of each patch (b). For spatial allocation, the average area
dedicated to each yak for manure heaps © and night pens (d) was determined by dividing the respective total areas by the herd size on each farm.
Regarding emissions, the methane emission factor was based on values for growing yak steers with a specified daily intake (e), and a specific
oxidation rate was also applied (f).

Pasture CH and N O fluxes
2
4
The data on the fluxes of CH and N O from grazing alpine meadows were adopted from our previous
4
2
work . We measured the seasonal dynamics of net CH and N O fluxes in 2012 and 2013 using the static
[22]
4
2
chamber method with three replicates on each sampling date and in each farm. During one sampling
process, four gas bags were collected, with an interval of ten minutes each time. Sampling was conducted at
0, 10, 20, and 30 min after the box was closed, and the temperature inside the box and the surface
temperature of the 0-5 cm layer before and after the box was closed were simultaneously recorded. Each
sample was collected between 9:00 and 11:00 local time, representing the average emission flux for each
day . The calculation of these fluxes was based on the linear concentration changes of CH and N O in the
[26]
4
2
chamber headspace, followed by corrections for ambient air temperature, atmospheric pressure, and the
physical dimensions of the chamber. To derive annual cumulative fluxes, daily mean values - calculated as
the average of spatial replicates - were extrapolated across the entire year. In addition, CH and N O fluxes
4
2
were also measured simultaneously from a fenced alpine meadow using the static opaque chamber method
in this study. Further details on CH and N O fluxes measurements and calculation are provided in previous
2
4