Media Release , September 2025
“SWEET VALIDATION”
Building fully automated effluent systems for a fraction of the storage they used to need came down to some logic no one else entertained.
For 18 years, The Clean Green Effluent Company’s Lindsay Lewis told industry leaders and regional councils that they didn’t need big effluent storage ponds. Many laughed him out of the room.
It’s been a long, hard, and sometimes lonely road, but independent trials by leading researchers validated his work — and the Invercargill-based business is now in high demand throughout Australasia.
One of its first installations for a 1,500-cow Southland herd was based around a patented weeping wall and two 33,000-litre water tanks. It is still operating effectively with full council consent 18 years later.
In another example, a Palmerston North client’s regional council recommended 7.6 million litres for effluent storage. The Clean Green System achieved full compliance using a weeping wall and three water tanks (380,000 litres) — just 5% of that original storage estimate.
How is it possible?
“We are the only company that I know of putting out aerobic effluent,” Lindsay said.
“If you store it in a pond, it dies, and a plant can’t eat it until it becomes aerobic again.
We move it out quickly when it’s still alive — that’s key.”
Another important distinction is the parallel timber weeping wall, which separates the liquids from the retained solids. The daily distribution system allows for controlled applications at low rate, low depth (0.25mm) — eliminating nitrate leaching, ponding, and overland runoff.
“The difference between what we do and what everyone else does is that we put out fewer kilograms of nitrogen per day — using fixed pod sprinklers — than the plants can handle,” Lindsay said.
“The plant can absorb 2–2.5kg a day. If you put out 1.2kg of nitrogen a day, you don’t have to shift your pods at all, if you don’t want to. You also don’t have to worry about soil saturation because the plants are processing the nutrients as it goes through.
“But if you apply 20mls in a 20- minutes pass with a conventional irrigator, and then you get rain, there’s no way the soil can retain or absorb it.
“Instead of having a big stone trap, we have a weeping wall. Twice-a-day the water and effluent generated during milking is processed within two or three hours after milking.”
The bulk of the NPK [Nitrogen, Phosphorus, and Potassium] is captured in the organic humus at the weeping wall.
Farmers Get It
Lindsay said understanding the concept was initially easier for farmers than for officials.
“Because it makes sense to farmers. The reality is we can build an entire automated system for less than the cost of the ‘mega ponds’ alone.
That includes the pumps, the control gear, the weeping wall, green-washing the yards, irrigation pipes, and pods.”
Then there’s the environmental conversation.
Traditional open pond storage facilities have a large footprint and a significant surface-to-volume ratio, which is negatively impacted by rainwater. The Clean Green System uses sealed tanks for its effluent storage, and its concrete-lined weeping wall reduces rainwater storage requirements.
“Because we process the effluent quickly and it remains aerobic, there is also virtually no offensive smell produced from the storage or the dispersal system,” Lindsay said.
Two Hectares per 100 Cows
In many regions, industry best-practice allows an annual maximum of 150kg/ha of nitrogen application from effluent.
“Our system can be fully compliant while distributing all the effluent liquid in an area of two hectares per 100 cows.”
Ngaere Farms’ Jonathan Perry, at Stratford, said the Clean Green system was simple, made sense to him, and the price was right.
They designed sprinklers — fixing them to their fence posts — to distribute the effluent every day across several paddocks at safe rates.
“We only needed four storage tanks for 750 cows,” Jonathan said. “That’s unheard of.”
No Smell, Leaching, or Emissions
Lindsay says the results are why he does it.
“It’s nice to be acknowledged after almost 20 years, and we remain the only environmentally friendly company doing what we’re doing.”