Country Life: Inside a dairy farm's composting shelter

On overly wet and cold days when the wind below the Tararua Range is howling, and on dry, hot summer days, you're likely to find Waka Dairies' herd of milking cows taking shelter under a huge shed on the farm.

"It's basically a roof for over their head when times are hard, like we do when we go inside," managing director Michael Phillips told Country Life.

"It's looking after our cows more than anything."

The more than 5000sqm composting shelter is a key feature in how the team manage animal health as well as the environmental impacts of dairying by helping reduce nitrogen leachate.

It's filled with carbon - in the form of woodchip or sawdust - which not only provides the cows a soft underground padding, but helps turn their waste into compost which can be used to help fertilise maize and sugar beet grown on the farm for feed.

"It's probably our number one tool for managing our leachate," Phillips said.

They first started composting about seven years ago, but the original sheds blew down. Phillips said the main rationale behind investing in the new $1.3 million structure two years ago was about developing a sustainable winter management system for the farm.

"It's a great tool to use but it does cost a lot of money to build that infrastructure and manage your farming system with that new tool."

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Waka Dairies' 650-cow herd spends about two-thirds of the year in the shed, though this can range from just a few hours, when the weather turns, to all day and night. The "trigger points" are when the weather is too hot or too wet for the cows, and during autumn calving.

The bedding pack, which can reach temperatures of around 45 to 55C, helps keep the cows warm during the winter months.

There was little odour coming from the compost material when Country Life visited.

"Certainly when it's being managed correctly and you do everything right, it's fine," Phillips said.

They take temperature readings at least three times a week in different parts of the shed and do dry matter checks to make sure it's composting correctly.

The team also drive tractors through the bedding pack with rippers each day to aerate the materials.

About once a year they remove it to store it as compost, though Phillips hopes to push this out two years as the costs for carbon material has increased.

He is collecting data which he hopes will help improve his technical understanding of the process.

With New Zealand known for its grass-fed farming models, Phillips is mindful of the public perception of cows spending so much time under cover. He sees it as a hybrid system - grass and feed is also grown on the farm and the cows are not always inside the shed.

"For the public seeing us they think it's unusual or different but in terms of industry stuff within dairy it's a relatively known tool that is becoming more common. This is a perfect solution for what we're dealing with on farm."

It's helped them become more efficient without having to reduce the herd size.

Phillips said Waka Dairies' goal was to be a "leading producer", focusing on food, natural capital, skills, culture and energy.

The compost generated from the cowshed allows them to operate within a closed cycle system of nutrients and he hopes to explore renewable energy options in the future, including wind or solar power generation options.

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