A new feed pad design keeps leachate and rain runoff separate, keeping them out of dairy lagoons. The patented system from Dairy Nutrient Reclamation saves dairy producers money from not having to haul the extra water once mixed with manure. Two dairymen brothers, Ben and Mike Jones, developed the idea in 2018 to comply with new environmental regulations facing their 1,800-cow dairy in Wisconsin.
To prevent the 34 inches of annual precipitation on their farm from mixing with silage leachate and creating “contaminated” runoff otherwise headed for the dairy’s lagoon, regulators urged the brothers to build a roof over their silage pile.
“They kept telling us, ‘Just put a roof over the feed pad,’ as if that made sense somehow,” Ben Jones recalls.
Exasperated at the unrealistic suggestion, Ben says one day his brother realized they already had a roof over the silage – the pile’s plastic covering. They went to work figuring out how to get water from the plastic diverted off the feed pad without touching feed or leachate. That was the back-of-the-napkin conversation that led to the brothers’ innovative design. They have since patented it and lease it to partner engineering firms who do design work for dairy clients.
Their design employs slight concrete ridges not quite as tall as speed bumps and more gradually sloped than those on roads. Using their design, the surface of the concrete feed area becomes a “rolling feed pad” with several sets of these ridges funneling water from exposed sections of concrete down the slope to gutters near the edge of the pad.
“You can think about it kind of like how water moves off a large shopping center’s parking lot,” Ben says. “Those lots are also graded and sloped to be able to collect rainwater at a central point.”
Slopes, ridges and gravity are the fixed components of the system. The only human intervention required to make the system work is changing the drainage system’s manholes when the pile is built and as it is fed out.
For example, when building a new pile on the feed pad, solid steel manholes at the low-spot collection points are capped, keeping the fresh water drainage system closed. That allows the slopes and ridges of the feed pad to naturally channel any leachate under the pile to the collection point. Then, while yet under the cover of plastic, the leachate can pass over the solid manholes and run into a leachate collection trench covered with slotted concrete. During feed storage, this slotted collection trench is protected from rainwater entering it because the tail of the plastic covering the pile is left long enough so that it also covers the slots of the collection trench. The plastic tail is secured with tires or weights like the rest of the pile. Thus, with the system in this state, any water collected off the top of the pile runs off the plastic, over the covered slotted trench and to the system’s center gutter. It remains unadulterated (see photos below).
Then as the pile is fed out and employees peel back the plastic, they change the solid manholes to grated ones, “opening” that section of the exposed concrete to begin collecting fresh rainwater at the now-grated collection points positioned in front of the leachate trench.
Examples of a grated (left) and a covered manhole (center). Example of leachate collection trench in action. Courtesy image.
“The gradients in the rolling feed pad are so subtle you hardly notice that you’re even driving over them when building your pile,” Ben says.
For a 300-foot feed pad, the crest or high point of each ridge compared to the lowest point in the center gutter would be no more than 4 inches.
When the system collects leachate from the slotted trench, it directs it to a pre-cast tank. It’s occasionally pumped out and spread on fields. Clean rainwater that runs off the plastic into the center gutter is discharged safely into county ditches. In fact, after installing the system, Ben said his county had to line the ditches near his dairy with rock because the volume of water he started discharging began eroding the ditches.
Because he no longer must capture adulterated runoff in his lagoon, Ben is saving fuel, money and time on manure-hauling costs. His payback on the system was less than a year. Plus, he also estimates that for every 1 million gallons of water cleanly collected and diverted from his lagoon storage, he has freed up his lagoon’s capacity to add an additional 100 cows’ manure. For his farm, that could mean milking 500 more cows on the same permit.
“I love seeing more milk tankers than manure tankers going down the road,” Ben says.
To show the return on investment from his innovation, Ben has built a calculator to estimate how quickly the system would pay for itself based on the average rainfall at any given location. Most scenarios pay back the initial investment – an additional 30 cents per square foot of feed pad – within a year, he says.
Thicker manure and less volume of it to haul is also having a positive impact on Ben’s carbon footprint and environmental stewardship. He has to burn less fuel to empty his lagoon and the stickier manure he puts on fields is less likely to run off than thin manure.
“I get excited now every time it rains, knowing that volume of water is not going into my lagoon,” Ben says.
