Zeolite new hope to cut nitrate leaching
A sponge-like rock in the hills of South Waikato could help clean up our waterways.
Called zeolite, this porous, sponge-like rock is found in a variety of everyday items, ranging from laundry detergent to cat litter.
It is also used in high-value products including water treatment, a human detox product and as a mineral supplement for cattle.
It is hoped that zeolite’s ability to bind up the ammonium found in a dairy cow’s gut would cause it to excrete excess nitrogen (N) in its dung rather than in urine and reduce the amount of N it leached.
Ammonium forms in a cow’s rumen when it digests feed. Ordinarily, cows convert protein into energy of which ammonium is a component.
This excess ammonium is excreted in the form of N out of its body in its urine.
It is this N-rich urine leaching into waterways that is a major source of pollution in the dairy industry.
In a trial this spring, DairyNZ scientists will test zeolite’s binding abilities by feeding cows Optimate, the brand name of Blue Pacific Minerals’ (BPM) zeolite product.
The Tokoroa-based mineral extraction and processing company mine zeolite at its quarry and process it into Optimate to make it fit for animal consumption.
Optimate has been commercially available for a few years where it is used as a mineral supplement for cattle, designed to eliminate toxins found in its feed as well as improving feed optimisation.
If proven, this trial would show Optimate had environmental benefits as well as rumen benefits, BPM managing director David Hill said.
BPM received a $160,000 grant from the South Waikato Investment Fund, which it will use to support the trial being undertaken by DairyNZ.
Cows in the trial will be housed in stalls at DairyNZ’s Lye Farm near Newstead and the Optimate would be added as a feed supplement.
Scientists will then measure the nitrogen content of each animal’s milk, urine and dung.
If successful, Hill saw it as another piece of the puzzle in reducing dairy farming’s environmental impact, rather than a silver bullet.
‘‘It’s not something that’s going to solve the problem of N leaching. It’s a tool among a box of tools that farmers can use to assist with N leaching.’’
DairyNZ senior scientist Dr Pierre Beukes said the study will focus on measuring the urine to see if zeolite caused an N reduction.
‘‘If we can show that, I think it could be quite groundbreaking and it could be quite a big thing for the industry.
‘‘We’ll do our best to make the trial as watertight as possible meaning the answer coming out will be a yay or a nay and we can hang our hat on that.’’
If the result was then scaled up across the industry, it could be another mitigation tool the dairy industry could use, he said.
Beukes led a proof of concept trial of zeolite in 2016 also carried out at Lye Farm. This involved 12 cows, half of which were fed zeolite and the animal’s ammonia levels in its rumen were measured and compared.
‘‘We found there were differences in the [ammonia] trends over time with the zeolite cows having lower trends,’’ Beukes said.
While spot samples of the urine in those cows did not show a fall in N levels, Beukes said it was inconclusive because to get a proper result, all of the cow’s urine had to be measured over several days.
‘‘But the initial result was enough to show that something was happening.’’ he said.
The results of the spring trial would be known in 2019.