Wednesday, April 24, 2024

Running on a flexi tank

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Ensuring enough effluent storage was a priority for a Taranaki couple when they went through their consent renewal process.
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 Taranaki farmer and district councillor Grant Boyde had inadequate effluent storage so during the consent renewal process, he upgraded to a Flexi Tank.

Ensuring enough effluent storage was a priority for a Taranaki couple when they went through their consent renewal process.

A Taranaki farmer with an inadequate effluent storage capacity was finding he had to pump it out every day, even in conditions that were not ideal.

The system was so problematic to manage without the adequate storage requirements, that when Grant and Anissa Boyde’s effluent consent was coming up for renewal, they realised that it was the perfect time to upgrade.

They operate a 65-hectare (60ha effective) Stratford System 2-3 dairy farm, milking 180 mostly crossbred cows.

“Our original effluent system was a concrete sump that only held the effluent from one milking. It required pumping out to the travelling irrigator every day, whatever the weather,” Grant says.

“We wanted to front-foot the issue so began investigating our options. Except for storage, we had a pretty good effluent system. We have a travelling irrigator with hydrants that cover a large area of the farm.” 

Grant is a Stratford district councillor (SDC) and SDC representative for the Taranaki Regional Council Policy and Planning Committee. The roles keep him very busy, especially in keeping up with ever-evolving reform changes. It’s also why he feels it’s absolutely vital to be seen actively implementing any regulation changes.

The Boydes held three field days before looking at all of the different options and decided on a 300,000 litre Flexi Tank.

Flexi Tanks are an enclosed self-supporting bladder that rises and falls in height depending on how much liquid is stored inside. The tanks range in size, with models that can store from 100 to one million litres of effluent.

Flexi Tanks are simple to install and eliminate any expensive engineering consent work. The bladder is rolled out on top of a 100mm horizontal bed of sand before being attached to the farm’s effluent system.

“Installing a permanent tank can cost $70,000-$80,000 for our sized farm, whereas a Flexi Tank cost $27,000. There are many small farms in Taranaki, especially in the Stratford district, so that’s a fundamental game-changer,” he says.

“If we installed a tank, we would have to site it part-way up the farm. We’d then incur the substantial costs of getting power to it. That can amount to many tens of thousands of dollars. There are also extra expenses for a more powerful pump and electricity on top of the tank price. That prompted us to look at other options.”

The TRC has always been proactive on environmental issues and the region’s riparian planting scheme has been a prime example. The council understands that effluent systems are a substantial cost for a farm to incur. They try to be accommodating regarding farm budgets and timeframes, as long as they are kept informed of progress and farms are complying with their environmental requirements. 

“We have an excellent regional council. They’re aware of the pressures farmers face and the TRC like seeing farmer’s front-foot issues and putting things in place. They’re prepared to support them,” he says.

“Even though I initially had some concerns, the TRC consent process was straightforward. I completed the application, so that shows that it’s pretty easy.”

Dairymaster calculated the Boydes’ farm effluent requirements using the Dairy Effluent Storage Calculator (DESC) and the TRC visited to examine their volumes and calculated that a 300,000 litre tank would be sufficient for 200 cows.

Even though the Boydes milk 180 cows (possibly fewer next season), it ensured the farm’s effluent system was future-proofed.

“One issue we encountered was Fonterra stipulating that a Flexi Tank must be situated 45 metres from the cowshed. Fonterra visited the site and gave us dispensation that it be no closer than 42 metres. They were really happy with the system,” he says.

The Flexi Tank is easily monitored due to its proximity to the cowshed. A simple turn of a tap sends the effluent to the tank. Effluent is pumped through a sand trap to the tank for storage. It’s then gravity-fed back to the sump, which eliminates the need for another pump. The effluent is then pumped to the travelling irrigator. 

“It takes about an hour for the travelling irrigator to travel the length of the paddocks. All of our paddocks are flat, square and 2ha in size. Our irrigator has an override switch for any malfunctions, but I’m always here monitoring it while it’s in operation,” he says.

The farm has a 20ha effluent platform, but the pump has the capacity to pump it further around the farm. In the past it was difficult to manage the lack of storage. However, that’s now a thing of the past because effluent can be stored for approximately 25 days until needed to suit the farm’s effluent management system.

“The storage capacity gives us the ability to use the travelling irrigator further across the farm, which has wiped around $7000 from our fertiliser costs. That’s a lot of money for a farm our size. It’s also a substantial portion of the cost of the tank, which is eligible for an annual depreciation of 25%,” he says.

“Spreading effluent over a larger portion of the farm allows us to keep our nitrogen levels under the 190kg N/ha cap and adhere to the new rules preventing effluent application to saturated paddocks.”

The Flexi Tank has proven especially useful during summer, as it allows the storage of effluent and rainfall to irrigate an entire paddock in one day.

Whenever they use a relief milker, the effluent goes directly into the bladder for storage. If they go away for a week, he empties it out so the milker doesn’t have to use the irrigation system.

The Flexi Tank has proved to be a versatile system for the Boydes’ farm. It is a simple system, with little to go wrong or break down. They can now store more effluent, apply it efficiently, and better utilise it.

“If we ever expanded the farm we could easily install a bigger tank or put an extra tank beside the current one. Conversely, if we diversified and got out of dairying, we could empty it, roll it up and sell it,” he says.

“Now we don’t have to worry about the saturation point after it’s been pouring down with rain because we can store the effluent. There’s no runoff at all and we can strategically apply the effluent.”

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