A stable national herd will be a core requirement in the future to reduce methane emissions in the agriculture sector, the Joint Oireachtas Committee on Agriculture, Food and the Marine (JOCAFM) has heard.
A stable cattle herd, and therefore constant methane emissions, does not add significant additional warming, according to Dr. Frank Mitloehner from the Department of Animal Science at the University of California, Davis.
The JOCAFM has today (Wednesday, July 20) been presented with research, including from Prof. Myles Allen from the University of Oxford, showing that a rise in herd sizes would increase methane emissions and temperature warming significantly.
Prof. Allen said that in any discussion on sectoral emissions-reduction responsibilities, it must be acknowledged that the building up of the national herd over the last century will have contributed to global warming.
Global warming impact
Prof. Allen has made clear that the standard method currently used for characterising the effect of emissions on the climate in the form of a carbon footprint or CO2-equivalent emissions, does not reflect the impact of human activities on global temperatures.
“Almost all of the CO2 taken in by the animal through the forage they consume is returned very quickly through respiration from the animal, and through the meat and milk consumed by humans.
“About 3% is converted into methane and stays in this form for 12 years, then it converts back to CO2 in the atmosphere, which is where it came from,” founder of the Carbon Removals Action Group (CRAG), John Hourigan explained.
Because of this, all the billion tonnes of methane produced by ruminants over millions of years have been “recycled”, he added.
Despite calls from scientists in recent years to give biogenic methane separate consideration, Hourigan said the Irish government insists on treating it as CO2 equivalent, viewing it as a “one-way ticket” like methane from mining.
“The production of methane in agriculture requires the removal of carbon from the atmosphere, whereas methane emitted during mining, e.g., has no such removals to account for.
“This gives rise to a situation where 65% of the Irish agriculture’s carbon footprint is supposedly made up of biogenic methane, which is not causing any further global warming as long as livestock emissions decline by 3% per decade,” Hourigan said.
A 3% reduction in emissions would mean that the impact of the decline cancels the warming impact of the ongoing methane emissions caused by a herd that remains stable in size, Prof. Allen explained.
Speaking before the committee, Dr. Mitloehner raised the potential of emerging technologies, as some have led to a reduction of 30% of the dairy sector’s methane emissions over the past five years.
Outlining the promising potential of feed additives such as red seaweed, he added that Ireland is distinctive as cattle are primarily based on pasture, which has a significant carbon sequestration capacity.