Cow pee patches in dairy pastures could be hiding the secret to tackling a chunk of New Zealand's greenhouse gas emissions.
Urine patches in paddocks represent a headache for the farming sector - not just because they leach nitrates into waterways, but also because they contribute to agriculture's big emissions footprint.
The sector currently accounted for around half of New Zealand's emissions, largely through methane belched from ruminant animals like sheep and cows.
But just over a tenth stemmed from nitrous oxide (NO2) – and the bulk of that came from urine patches.
Now, Massey University researcher Nicolaas Portegys is investigating how we might be able to capture these emissions, by first better understanding how the patches actually behaved in the soil.
"Urine patches are made when a cow urinates on pasture – on fertile land, it'll spread laterally, but also downward," the masters student said.
"While we've got an okay idea what emissions they are producing, there are a whole lot of variations involved, such as different soil types, and how wet the soil is to begin with.
"We need to focus more on what's going on beneath the surface."
His project has involved taking soil samples in a high-resolution grid at three depths for mineral nitrogen analysis.
Having collected some 1600 samples, Portegys was helping validate other mapping tools, and contributing to a full 3D model being built by colleagues.
Part of the work was investigating what proportion of urine-nitrate that inhibitors might be able to capture before NO2 was created and released into the atmosphere.
One of those was the nitrogen-fixing fertiliser product DCD, which was pulled from the market in 2013 after low levels of it were found in milk powder.
"But there are a whole lot of other inhibitors that are being looked at, which could become options for farmers," he said.
"The immediate goal proposed for agriculture is 10 per cent reduction in methane by 2030 - and while we know it's hard, we can do that.
"But for the 2050 goals - particularly to reduce nitrous oxide to net zero - we don't have enough tools to achieve them, so we need new ways to get there."
He expected there would be much overseas interest in any breakthroughs here.
"As developed countries start bringing down their CO2 emissions, suddenly their agricultural emissions will begin to look a lot more important.
"You hear about New Zealand being a leader in this space, and we know that when other countries want this information, we'll be able to step in with it."
His project comes as a New Zealand-led team of scientists revealed, for the first time, the main microbes and enzymes in animals' rumen, or stomachs, that both produced and consumed hydrogen.
The findings were crucial because scientists could now begin to target the supply of hydrogen to methanogens as a new way of reducing animal methane emissions.
Work would now focus on screening specific compounds that could reduce the supply of hydrogen to the methane producers without compromising animal performance.
Research would also seek to find ways to divert hydrogen away from methanogens towards other rumen microbes that do not make methane.