(Bloomberg) — Twice a day at milking parlors all over New Zealand, the world’s biggest dairy exporter, sheds are hosed down to wash away cow dung into large manmade ponds.
In an attempt to recycle the water in the lagoons, two local scientists — Keith Cameron and Hong Di — began testing the addition of polyferric sulfate, a chemical that’s been widely used in wastewater treatment to separate liquids from solids. The process worked, but that didn’t prove to be their most interesting finding.
When the pair of soil and physical sciences professors at Lincoln University ran checks to monitor for any impact on greenhouse gas emissions, they made a startling observation: Methane emissions from the wastewater had decreased by more than 90%.
“The whole course of our research program changed overnight,” said Cameron, who has retired from teaching and spent the last four years researching and developing the treatment.
Di said manure accounts for roughly 10% of livestock methane emissions, a greenhouse gas that’s more than 80 times more potent than carbon dioxide over a 20-year period. Large industrial farms often collect and store waste in giant sealed tanks known as anaerobic digesters that capture methane. Those digesters can cost millions of dollars, though, and curtailing the pollution on smaller farms has remained challenging. But Cameron and Di may have unwittingly found something that works.
By introducing polyferric sulfate into the lagoons, the scientists tipped the scale in favor of sulfate-reducing microorganisms, allowing them to outcompete methanogens —which generate methane, are plentiful in cow poop and grow considerably in effluent ponds — for food. The result was a sharp drop in a powerful greenhouse gas that farmers have been trying to tame for years.
The innovation — developed under the name EcoPond — is being rolled out across 250 farms associated with Fonterra Co-operative Group and Synlait Milk Ltd. through a pilot program. Dairy giant Fonterra, New Zealand’s largest company that’s owned and supplied by thousands of farming families, says the treatment can help it toward a goal of cutting on-farm emissions intensity 30% by 2030 compared to 2018 levels.
Food systems, which encompass everything from growing and processing food to consuming it or throwing it away, account for about a third of humanity’s greenhouse gas emissions. Much of that footprint is linked to livestock farming, a major source of methane.
Tackling those emissions has proven difficult because there are few solutions to the biological processes that generate the gas. For example, to address methane released by animals like cows and sheep, scientists are developing burp-catching masks, seaweed-based supplements and vaccines. So far, none of those solutions have had a major impact.
Cameron and Di’s innovation is part of an emerging field of scientific work that’s focused on cutting the emissions from manure. The methane captured by digesters used on some large farms can then be used to generate heat, electricity or fuel. But in New Zealand, where livestock spend most of their time at pasture and herd sizes are smaller, the amount of manure generated indoors typically isn’t enough to warrant a digester.
To treat a lagoon full of cow poop, the mixture is sucked into a pump on a truck and run through a manifold where it is mixed with polyferric sulfate and sulfuric acid. After treatment, the slurry is deposited back in the lagoon. The process typically takes a few hours and is repeated every six to eight weeks.
Agnition, the unit of farmers collective Ravensdown that’s seeking to commercialize the process, is still determining how much it will cost. The group declined to provide estimates. Funding for the Fonterra pilot comes from the collective and through programs backed by Mars Inc. and Nestle SA.
“It’s likely to be affordable for farmers, particularly if they’re dairy and their cooperative is supporting them to reduce methane,” said Mike Manning, Ravensdown’s chief science officer.
The treatment has the potential to reduce New Zealand’s individual dairy farm emissions by between 7% and 9%, according to Cameron. Agriculture is a cornerstone of the nation’s economy and accounts for about 80% of its exports and more than half of its total greenhouse gas emissions.
While the initial pilot is focused on farms raising cows, the approach has “broad applicability across various methanogenic environments — such as rice paddies, wetlands and similar systems,” said Marcelo Mena, chief executive officer at the Global Methane Hub, a nonprofit dedicated to reducing the greenhouse gas, and which isn’t involved in the New Zealand project. Mena is also a professor of biochemical engineering at the Pontifical Catholic University of Valparaíso in Chile.
One drawback to using polyferric sulfate and other materials to inhibit methanogens in manure is that the approach can impact soil and water quality and disrupt microbial ecosystems, said Zhidan Liu, a professor of agricultural engineering at China Agricultural University in Beijing.
There was no significant difference on pasture yield or soil condition over a four-year trial in which Cameron and Di compared effluent treated with polyferric sulfate and untreated plots, according to a 2023 study.
The treatment developed by Cameron and Di is a welcome relief for farmers under pressure to reduce their emissions but with limited opportunities to do so, said Stuart Taylor, the general manager of farming at Craigmore, a farming, horticulture and forestry business.
“The New Zealand agricultural community realizes they have a role to play in reducing their greenhouse gases,’ said Taylor. “They’ve been screaming out for technologies to support them.”
–With assistance from Tom Redmond.
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