TY - JOUR
T1 - Methane emissions from free-ranging cattle
T2 - Comparison of tracer and integrated horizontal flux techniques
AU - Griffith, David W.T.
AU - Bryant, Glenn R.
AU - Hsu, David
AU - Reisinger, Andy R.
PY - 2008/3
Y1 - 2008/3
N2 - Accurate measurements of methane (CH4) emission rates from livestock in their undisturbed natural environments are required to assess their impacts on radiative forcing (i.e., enhanced greenhouse effect) and the environment. Here we compare results from two nonintrusive techniques for the measurement of CH4 emissions from cattle. The cows were kept in an outdoot feeding strip that allowed them to follow natural behavioral patterns but contained them within a well defined space. In the first technique, nitrous oxide (N2O) was released as a tracer at the upwind edge of the feeding strip, and the downwind concentrations of N2O and CH 4 were measured simultaneously using Fourier transform infrared (FTIR) spectroscopy. Average CH4 emission per cow was calculated each half-hour on three separate days from the correlation between the two gases. The second technique was the integrated horizontal flux (IHF) or 1-D mass-balance method, in which we used the measured vertical profiles of CH 4 concentration and windspeed downwind of the cows to determine the total CH4 emission. Comparing the IHF results to the known release rate of N2O allowed us to test the IHF technique independently. We found agreement within 10% for all comparisons on all days. The daily CH 4 emission rate averaged over all tracer and IHF measurements was 342 g CH4 head-1 d-1. This is within the range of previous measurements for mature lactating dairy cattle (200-430 g CH 4 head-1 d-1) but higher than expected for yearling cattle. The high CH4 emissions are accompanied by high CO2 emissions determined from the FTIR measurements. The bias is most likely due to the measurements being made during and after supplementary feeding of the cattle.
AB - Accurate measurements of methane (CH4) emission rates from livestock in their undisturbed natural environments are required to assess their impacts on radiative forcing (i.e., enhanced greenhouse effect) and the environment. Here we compare results from two nonintrusive techniques for the measurement of CH4 emissions from cattle. The cows were kept in an outdoot feeding strip that allowed them to follow natural behavioral patterns but contained them within a well defined space. In the first technique, nitrous oxide (N2O) was released as a tracer at the upwind edge of the feeding strip, and the downwind concentrations of N2O and CH 4 were measured simultaneously using Fourier transform infrared (FTIR) spectroscopy. Average CH4 emission per cow was calculated each half-hour on three separate days from the correlation between the two gases. The second technique was the integrated horizontal flux (IHF) or 1-D mass-balance method, in which we used the measured vertical profiles of CH 4 concentration and windspeed downwind of the cows to determine the total CH4 emission. Comparing the IHF results to the known release rate of N2O allowed us to test the IHF technique independently. We found agreement within 10% for all comparisons on all days. The daily CH 4 emission rate averaged over all tracer and IHF measurements was 342 g CH4 head-1 d-1. This is within the range of previous measurements for mature lactating dairy cattle (200-430 g CH 4 head-1 d-1) but higher than expected for yearling cattle. The high CH4 emissions are accompanied by high CO2 emissions determined from the FTIR measurements. The bias is most likely due to the measurements being made during and after supplementary feeding of the cattle.
UR - http://www.scopus.com/inward/record.url?scp=40849136504&partnerID=8YFLogxK
U2 - 10.2134/jeq2006.0426
DO - 10.2134/jeq2006.0426
M3 - Article
C2 - 18396544
AN - SCOPUS:40849136504
SN - 0047-2425
VL - 37
SP - 582
EP - 591
JO - Journal of Environmental Quality
JF - Journal of Environmental Quality
IS - 2
ER -