Waterford Press , NZ Dairy -Spring 2025
Innovative effluent distribution system
Lindsay Lewis grew up on a third generation dairy farm with a Jersey stud in Southland and being an electrician/ lift engineer by trade he knew that technology could be used as a solution to all sorts of problems.
In the early 2000s, with increasing numbers of dairy cows around the country, the issue of managing effluent was becoming a major challenge. Lindsay realised there was a smarter way — and began designing systems for dairy farmers who wanted to change their approach.
“I was aware that dairy farmers were getting a bad name because of the way they dealt with effluent but there was no technology to change what they’d been doing. I designed a control system that allowed us to put effluent out in minute amounts on a daily basis instead of having to store it then put it out, in what I call industrial scale amounts, on the limited number of days when the ground is in the right condition,” explains Lindsay.
The size of the dairy effluent problem owes more to the amount of water required to wash everything down in and around the milking sheds than to the 2.5 kgs of pure effluent dropped by your average cow daily, which is the crux of Lindsay’s Clean Green Effluent system. It’s designed around using greenwater in the external yards, while still using the requisite fresh water in the milking shed which is deemed a food processing environment.
The success of the Clean Green Effluent distribution system depends on the weeping wall that Lindsay designed knowing he needed the water to be clean enough for easy, daily use, he explains. “It’s totally different to everyone else’s and what’s coming out is very, very clean. We had to get it down to two parts per million, which meant it was clean enough that Fonterra used our system as the case-study to allow greenwash to be used legally in New Zealand from 2008. The weeping wall takes out the solids and a huge percentage of the nitrogen, potassium and phosphates which means what remains has very little solids and very little nutrients in it. But the key to it is that we get rid of it every day which means it’s still aerobic and the pasture can absorb it, so there’s no nitrate leaching.”
Typically a washdown of the yards and the shed is using 50 to 70 litres of freshwater per cow. By using cleaned, filtered and seriously diluted recycled effluent to wash down the yards that reduces to the 20 litres per cow typically used inside the shed. Farmers using the automated system, which progressively washes the yards behind the cows as they enter the shed, tell Lindsay the yard is cleaner than it used to be because they’re not worrying about how much water they use, and they’re not having to hang off the end of the hose themselves once milking’s done.
The net result of this automated system is no need for effluent storage ponds, no travelling irrigator, no smell, no emissions, and no need to wait for soil to dry out before the effluent can be distributed, thanks to its application rate, says Lindsay. “Instead of putting out an application of 25 millimetres depth, we’re putting out .24 of a millimetre depth of diluted liquid effluent which is less than evo transpiration (or plant’s sweat), so it’s less than what the sun’s taking away. According to the farmers they grow 35% more grass than with any other system.
Also according to what Clean Green Effluent Company’s clients have told him it’s cheaper than any other system they looked at, and any farmer with more than one farm who’s installed it goes on to install it on the rest. It’s a win-win all round including for the environment.