On one end, they're constantly cranking out milk. On the other end, dairy cows are continually squeezing out something else: Excrement. But at Alliance Dairies, they don't call it waste.
"Manure has a lot of value," said Jan Henderson, the dairy's chief operating officer.
Alliance is going green with its surplus brown stuff, converting cow manure into electricity.
"Poop to power," Henderson said, smiling.
The secret is a dizzying array of pipes and a massive chunk of concrete that stretches over two football fields.
"It's basically full of manure," explained Del Bottcher, Ph.D., the engineer who designed the digester.
Through an ingenious system just steps from the barn, droppings from 5,000 Alliance cows flow through a maze of pipes to an elevated screen. The feces cascade at a gentle, hypnotic pace.
From there, the manure flows into the partially concrete bunker, which plunges 16 feet into the ground.
Bottcher said that is when microbes go to work -- slowly.
Over roughly 21 days, the manure gently flows back and forth, gradually heating to 101 degrees Fahrenheit. Microbes begin to break down the feces and extract energy.
"It converts it into methane," he continued.
Bottcher said the methane is immediately used to power a generator that cranks out a megawatt of electricity – enough to power 425 homes. "It's a lot of power."
When there's more electric than Alliance needs, the dairy sells it to the local utility. Theoretically, electric from cow poop is powering homes.
But most of the time, Alliance uses every watt it makes to keep its milking operations high-gear. The routine is non-stop. The cows each eat 55 pounds of feed each day; they are milked three times each day; they filling several tractor-trailer milk tankers each day, and the generators run 24 hours a day.
"We're very proud of what we've done here," Henderson said. "We are powering ourselves."
Henderson estimated Alliance will save $1 million annually on power costs by producing its own electricity from cow manure. Alliance said its digester is the first of its kind in the southeastern United States, and could serve as a role model for other large dairies.
Once the energy is extracted, a solid is leftover. It's still brown and its texture is still soft, similar to that of oatmeal cookie dough. But it's benign and safe enough to hold in the palm of your hand. Alliance has plans for it, too.
The byproduct might be used as peat for potted plants or as bedding for the cows, who currently sleep on sand—which wreaks havoc on the pumps.
"We are the ultimate recycler," Henderson said.
The battleship grey digester itself isn't much to look at. Yet, it's a feat of engineering in an emerging era of sustainability.
"You just can't realize how big this thing is," Bottcher said. "I'm really excited."
And besides the $1 million Alliance expects to save, there is one invisible benefit: The smell. The manure is contained. That means a little less odor in the air.
"We can say our ‘you know what' doesn't stink, our neighbors like us a whole lot more," Henderson said. "It's hard to put a price on that."