Dairy processing byproduct used makes great fertiliser

Waste activated sludge that is created from Fonterra's milk factories is being used as organic fertiliser by dairy farmers.

Waste activated sludge that is created from Fonterra's milk factories is being used as organic fertiliser by dairy farmers.

An organic byproduct used by Fonterra's milk factories to treat bacteria has been turned into a fertiliser that delivers pastoral and environmental benefits for farmers.

The waste activated sludge (WAS) is an organic product that acts as a nitrogen and phosphorous fertiliser replacement.

Fonterra said it had proven benefits for balancing soil pH and prompting grass growth.

WAS is made from a bacteria Fonterra used in its factories around the country. The bacteria ate dairy solids and dropped to the bottom of the steel tank when it was finished, leaving clean water behind. The bacteria is then dried and used as free fertiliser for Fonterra farmers.

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Fonterra environmental engineer, Song Li said WAS acted as both a fertiliser and a soil improver.

"We see incredible results on our Fonterra farms. It's a slow releasing fertiliser so unlike nitrogen fertilisers, WAS releases its nutrients into the soil slower, spreading the benefits to pasture and crops out over a much longer period," Li said.

"The organic matter in sludge can improve the water retaining capacity and structure of soils".

Dairy farmer John Mikkelsen said WAS had helped reduce his on-farm nitrogen count, while also promoting solid grass growth – the best of both worlds for farmers.

"I've been using WAS for over four years now and have seen really good grass growth as it maintains soil fertility. And it's been great for my clover."

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"I use it as an equivalent to maintenance fertiliser and only use it once yearly."

"I do not put any solid or chemical fertiliser on those paddocks [where I put WAS on] - I don't need to, it seems to be slow release and the grass grows well."

Mikkelsen said the bulk of his farm received WAS and about 80 hectares was fertilised using dairy effluent via a travelling irrigator.

The only new urea he has used this season was on new grass paddocks to help get them established.

"It's just organic fertiliser and I'm not a big user of urea anyway. It's just not my thing. There are people out there who use too much nitrogen."

He estimated WAS saved him about $40,000 a year.

Mikkelsen's farm is close to Fonterra's Edendale dairy factory and WAS is delivered to him in spring.

A small amount of WAS is injected into the ground on paddocks after they are grazed by a contractor in a process similar to direct drilling seed

"The WAS runs down the tube and into the cuts. There's no effect to the pasture, it just puts a little grove in there and drops it down."

Fonterra supplied WAS to more than 300 farmers around the country, with thousands of tonnes coming out of biological treatment plants at their sites at Lichfield, Edendale, Stirling, Kauri, Te Rapa and Pahiatua.



 - Stuff

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