This article was among Farmers Weekly’s most read in 2022.
New Zealand livestock farmers are being sold short by methane reduction policies that fail to acknowledge the role of methane sinks and that fossil fuels are increasing emissions of the greenhouse gas.
Scientists addressing an Ag@Otago webinar organised by the University of Otago group said virtually all NZ sheep and beef farmers and most dairy farmers would be carbon dioxide-equivalent neutral due to the naturally occurring element hydroxyl, which removes methane from the atmosphere.
Nature has and continues to provide methane sequestration, they say.
They also expressed doubts an effective methane vaccine for livestock will be developed because of the difficulties overcoming the complex biology of ruminant animals.
Peter Bruce-Iri, who works at North Tec and has degrees in horticulture, education, business and management and now works on climate change, says biogenic methane levels have been relatively steady from 1970 to 2018 while emissions from fossil fuels have risen sharply.
He believes methane sinks such as hydroxyl have been given inadequate acknowledgement.
“You look at documents such as the Inter-government Panel on Climate Change and you see the words emissions and carbon dioxide equivalent mentioned thousands of times.
“They’re the only games in town but there is no talk of methane sequestration.”
Bruce-Iri says the mathematics and accounting of methane levels is acknowledged as inaccurate and has resulted in a simplistic policy approach which hamstrings the livestock sector.
The number of ruminant animals has been largely static for many decades but fossil fuel extraction, especially the extraction of shale gas, has increased sharply and with it methane levels.
He says research shows that hydroxyl radicals, known as a naturally-occurring atmospheric scrubber, removes 90% of methane in the atmosphere.
Soil absorbs less than 10%.
However, the Australian Academy of Science says global methane emissions have overtaken removal by 22 megatonnes a year.
The association also cites work by AgResearch that found each cow produces between 130 and 230 litres of methane a day and that livestock produce about 28% of global methane emissions from human activities.
Bruce-Iri says satellite imagery of methane hotspots around the world show the most intensive contributors are fossil fuel leaks but politicians lump all methane emitters together under the same policy without acknowledging the role of hydroxyl or low intensive livestock farming.
Those policies have helped inflate the carbon price, which he says would collapse if a more accurate methane calculation was used and hydroxyl acknowledged.
Another contribution from pastoral farmers that is not acknowledged, is the cooling effect of vegetative ground cover.
Bruce-Iri used thermal imaging cameras over summer which showed differences in temperature of more than 30degC between vegetative ground cover and bare ground, sealed roads or paths.
Alfred Harris, the research manager with Pacific Biocarbon who specialises in soil, compost and biocarbon, says the microbial function of the soil and vegetation offers natural solutions to issues such as greenhouse gas and managing nitrogen.
The key is to manage the soil as a deep profile rather than just the top few centimetres by using deep rooting plants.
He says NZ soils have the potential to capture and retain vast amounts of carbon.
“We have a situation where the models used are over simplified so the potential of soil as a carbon sink is greater than the Government acknowledges.”
NZ’s extensive livestock system compares favourably to methane generated from intensive feedlot systems, and the world needs to know that.
“We as NZ have a very good story to tell with our herbage-fed, pasture-based system, so why are we signing on to this methane story?” he says.
Purnell says the UK has shown methane emissions can be measured on individual farms.
Ag@Otago director, Emeritus Professor Frank Griffin says NZ has been caught up by the rapid increase in global fossil fuel-produced methane emissions in the past decade.
Griffin, a microbiologist, says the role of hydroxyl raises questions about the lifecycle of methane and how its behaviour differs between farms and within farms.
