Lagoon effluent has become a good thing for the Prins family of Modesto, CA.

Not “good” in the normal sense that it contains nutrients, so they're willing to tolerate the stench and the other negatives to get what they need from it. Instead, it is good in the sense that it is now a substance they truly don't mind being around. Good because:

  • It doesn't burn the grass back around the flood irrigation outlets in their pastures.

  • It leaves the barn alleys clean and dry after flushes, with no slick surfaces, and it doesn't spread disease back through the barns.

  • Marjorie Prins hand waters her whole yard with it, even carrying it into the house for houseplants.

  • The Prins dairy effluent is so innocuous that one of Marjorie's prized snapshots is of her grandchildren splashing bare legged in thousands of gallons of effluent cascading from a tank truck onto her lawn.

Frankly, the system is so good the Prins family believes it's whipped a manure problem that is crippling the rest of the confined animal industry. Best of all, they did it profitably.

Kevin Prins estimates his family has spent more than $100,000 converting their 500-cow dairy to a circulating, more aerobic type effluent system. By his “conservative” estimate, the economically accountable benefits would pay back that price in two years, possibly less.

Aerobic is the answer

The secret to the Prins family's victory over the forces of accumulated waste has come via a switch from the industry standard — a static, highly anaerobic lagoon — to one that's circulated and includes much more aerobic activity. Essentially, they've moved away from anaerobic toward aerobic processes, which apparently achieve a much more diverse and, therefore, natural mixture of microbial activity.

It's a completely new concept, since the lagoons commonly dubbed “aerobic” were shallow ponds that were only aerobic near the surface.

The 11-12 million gallons of water in their three lagoons are constantly circulated by eight floating propeller-like turbines called CirCulators. The manufacturer says each lifts 8 million gallons of water/day. That means the whole system is turned every five hours.

Different look and smell

The resulting effluent has a distinctive red color and little or no odor. In mid-January, standing on the earthen berm that separates two smaller lagoons from the newer, larger one, there was a mild, musty scent at times, but not unpleasant. The weather was cool and overcast, and had been for some time. This very low level of odor is actually rather unusual, and certainly as strong as it gets, the Prinses say.

In fact, there's little unpleasant odor anywhere on the dairy — not by the lagoons or near the solids separating unit, not in the alleyways between the barns.

The free-stall barns themselves smell like feed instead of manure and ammonia. The metal in the buildings isn't rusted or corroded, even at the flush outlets or where ammonia and hydrogen gas usually build up and destroy the roofs of most dairy barns.

Fertilizer savings

The Prins family no longer buys any fertilizer for its 130 acres of pasture. Instead, they use only the effluent and manure solids for fertilizer. Grazing has become uncommon on large dairies these days, but the Prins family says it helps them reduce purchased feed and the associated costs in the barns.

With the more aerobically treated effluent, the Prins family produces more forage and the quality is better, Kevin says. With crude protein levels near 30% during the best parts of their growing season, the family has cut the protein costs in their rations. They also sell effluent to their neighbor for about 70 acres of cropland.

Nutrient analysis of the effluent shows the nitrogen:phosphorus ratio is about 6:1, the very level needed by plants, the level excreted in urine and feces by livestock, the amount present in the bodies of livestock, and the amount present in milk.

Eliminating fertilizer cost is worth at least $40,000 to $50,000/year, Kevin estimates. This is borne out by the experience of another Modesto-area dairyman who uses the same system and says he, too, no longer buys fertilizer.

Pete Verburg says last April he calculated the current value of the nitrogen, phosphorus and potassium levels he used prior to adopting the same circulated system the Prins family uses three years ago. It would have cost $150,000 this past growing season.

There are other direct savings, including much better cow health and lower incidence of cow injury, the Prinses say. Their cows aren't breathing ammonia and hydrogen sulfide gas with every barn flush, nor tiptoeing across slick alleys and breaking each other down by riding one another on slick floors.

Letting good microbes work

The system works because it creates an environment where the beneficial microbes can function, says Gary Wegner, CEO of CIRCUL8 Systems (pronounced “circulate”).

His company, which has consulted with the Prins family for the last six years, takes a more holistic approach, called “nutrient harvesting.” Wegner says his background in animal nutrition helps him remember to factor in the nutrients going into the system as well as those coming out.

Wegner says lab analysis shows the lagoon tests positively for a high level of aerobic activity. The lab also found evidence of photosynthesis in the sample, an indication the lagoons now include both aerobic and anaerobic activity. Much of the work may be due to facultative bacteria, which can function in either environment.

Exactly what's going on in these lagoons remains a mystery, as is much of the microbiological world. Yet the results make it obvious that a more natural and beneficial set of interactions exist under these conditions.

The condition in the Prins lagoons is produced by the action of floating CirCulators. It's a process that constantly lifts the water from the bottom of the lagoon so all or most of the water reaches or approaches the surface several times/day. The three key components to this process are mixing, sunlight and oxygen.

Gravity ensures that the water flows progressively through three lagoons, each one giving the effluent more time to be treated by the apparently diverse microbial mixture. From the third lagoon, it may go out onto pasture or cropland, or flush back through the barns and start the circuit again.

Ratcheting up

Kevin Prins heard Wegner speak on lagoon circulation at the California Farm Equipment Show (now World Ag Expo) seven years ago. Wegner got his attention with his example of what happens in an aquarium if you turn off the air pump.

“The water turns green and slimy and the fish die,” Prins says. “That's how he sold me on the system. I had a 20-gal. aquarium when I was a kid. It's all the same biology.”

The Prinses started with two of Wegner's machines in one lagoon. Within a month, they saw a difference in the lagoon water and flush water. They added machines and saw more differences, then added another lagoon and more machines and saw an even greater difference. Then they added a screen-type solids separator and a settling pond to capture the fine material before the water enters the first of their three lagoons.

At every step of capital improvement on the circulated manure system, they've seen improvement in the effluent and all the things it affects, they say.

Although Wegner and partner Anne Goggin have focused their attention on dairies in California, they also have circulation equipment working on a hog operation, irrigation water holding ponds, winery wastewater ponds and an egg processing facility. Wegner says the biologic activity slows down in the winter, especially in relatively cold environments. Yet even in cold weather, ponds stay open and flowing, continuing to produce heat below as the water movement continues. Wegner believes the process should work in most places and regardless of animal type or climate.

Hog manure is not as easily separated into solids and liquid, but the quality and lack of toxic elements in this type of effluent could allow a return to the idea of regular flushing of hog houses, and therefore the potential for better separation and treatment of hog manure slurry.

Taking the leap

“We've had a lot of people come and look,” Kevin says. “They're impressed, but they see the dollar figures and walk away.”

“A lot of guys just see another place to spend money, but they're not thinking the whole process through,” adds John.

Yet there's more than monetary payback. One improvement that's hard to quantify in dollars is quality of life, Kevin says. Getting some of the monkeys off his back has made thinking and improving easier and more fun.

John goes even farther. He says he was once a slave to his manure handling system, but now he's been set free.