METHANE EMISSIONS FROM MANURE OF FREE-RANGE DAIRY-COWS

Measurements have been made of the extent of CH4 emissions from the waste of free-range dairy cows. There was considerable variability in the emission rate from individual cowpats, ranging from more than 100 ug/min to near zero. The emission rate was strongly influenced by the cowpat temperature. Overall, emissions from this source were found to be insignificant compared to those from the rumen. Some flux measurements were also made on the swampy cesspit area into which the manure from the dairy floor were washed. Although the extent of this swampy area varied according to climatic conditions, it appeared to be an efficient producer of CH4 with emission rates in the range 5 - 25 mg/m2/min. It is estimated that the CH4 from this source was equivalent to about 5% of that produced by the herd from fermentation in the rumen.