Livestock methane’s impact on global warming has been ‘overblown by a factor of three to four’
Concern has emerged that if developed agricultural countries such as Ireland and New Zealand reduce milk production to lower emissions, dairy yields will shift to higher-emitting dairy markets like India, Pakistan and Bangladesh — now considered “the centre of dairy in the world”.
Speaking at the Alltech One Conference in Lexington, Kentucky, Dr Torsten Hemme, director of the IFCN Dairy Research Centre in Germany, said dairy milk production is counting for 2-3pc of the world’s greenhouse gas emissions, and 75pc of these greenhouse gas emissions are in emerging market countries.
“Yet we spend time on the 25pc because we have the money and the energy to focus on it,” he said.
“Let’s assume now you replace this milk with something else — you don’t take 25pc out, you maybe take half of that out because you need other products.
“So all the energy we spend on dairy, and CO2 in the rich countries equates to about half a percent of global greenhouse gas emissions.
“Maybe we are already cooling the planet with dairy without knowing it, but we don’t have the data.”
Asked how long it will take to get more accurate data on farm system emissions, Dr Hemme added: “We need a carbon sequestration methodology, then we need to measure it, then we need to apply the global data, and then we need to get acceptance — I think we can do it in one or two years.
“Assuming we are wrong in how we judge methane in our calculations — and there is a chance that we are wrong — it might be the case that already cattle are net positive, but we don’t have the metrics.
“The question we need to ask ourselves is: are we 100pc sure that we are doing the right things? It’s a political dilemma that has moved dairy into the corner where we are right now.”
It comes as agricultural scientists continue to question the accuracy of metrics used to calculate methane emissions from livestock which underpin new climate policies for global farm sectors, including in Ireland.
While the calculation called ‘GWP100’ is considered “the most common way” to count agricultural emissions today, there is ongoing debate that this metric “overstates” the impact of a constant methane source “by a factor of three-to-four”.
At the same time, policy makers are being urged to transition to a new calculation called ‘GWP*’ — developed by climate scientist Prof Myles Allen of Oxford University — which reflects that methane is not accumulated and that it is a “breakable” greenhouse gas.
Frank Mitloehner, Professor of Animal Science and Air-Quality at the University of California, Davis, said at the conference that “the worst thing about GWP100 that I see is, if you have a constant source of methane, let’s say a constant cattle herd, and you use GWP100, then you overblow the impact of that constant source of methane on global warming by a factor of three-to-four.
“I have been tooting this for the last few years. I’ve been criticised for this view… if you don’t believe me, go to the Intergovernmental Panel on Climate Change Sixth Assessment Report and you will see what I just said confirmed.
“A matrix that overblows impact of a constant source of methane by a factor or three-to-four is not fit for purpose.
“We need to have quantification methods that accurately depict what is going on.
“This has nothing to do with me working in the agricultural sector… this has nothing to do with being close to industry… this has to do with understanding the physics around this gas and what we need to do in order to manage it.”
Asked about the accuracy of the GWP100 metric for calculating methane emissions from livestock in Ireland a spokesperson for the Environmental Protection Agency (EPA) said: “In the national greenhouse gas emissions inventory, methane emissions are presented in two ways – as (1) mass of methane emitted in tonnes and (2) as carbon dioxide equivalent (CO2e).
“The latter is calculated using the GWP100 values provided by the IPCC. This is in line with the reporting requirements adopted under the Paris Agreement and used by the EU and parties to the United Nations Framework Convention on Climate Change (UNFCCC - 197 countries).
“In relation to the GHG inventory and projections reports produced by the EPA to meet EU and UN regulations and guidelines, new reporting guidance would need to be adopted by parties to the UNFCCC before different metrics could be used by the EPA.
“Whether or not one metric is better than another distracts from the message, made clear in the recent IPCC reports, that methane emissions must reduce, irrespective of the metric used to convert to CO2 eq.
“Methane emissions in Ireland have increased by 19pc in the decade to 2020, with the agriculture sector responsible for 93pc of methane emissions in 2020.
“The other main source of methane emissions in Ireland is the waste sector, specifically the methane component of landfill gas.
“Overall, the EPA position is that GHG emissions need to be reduced in line with achievement of national and EU targets and all sectors need to contribute to this effort.”
The UNFCCC did not respond to Farming Independent queries.