Seven years ago, Matt Slegle was ready to build a brand-new slatted-floor barn to house more than 1,000 backgrounder cattle on his farm in Cato, N.Y.
Then, the heartbreaking stories of people dying in manure pits had him thinking: Could it happen to him?
“There were accidents in Ohio and Lancaster County [Pa.] where guys went down into their pits to do something and were overcome by gas,” Slegle said. “Multiple people died trying to rescue them. I said to myself, ‘I don't need to be down in that pit ever.’”
It was then that he heard of technology from Europe that could potentially solve the air-quality problem he was worried about. He took a dive and built the first slatted-floor barn in the U.S. with an automatic aerated manure system underneath. He hasn’t looked back.
“It’s been working great ever since. I don’t regret it one bit,” Slegle said.
How aeration works
David Troop, owner of Troop Equipment in Cochranville, Pa., said more farms are adopting automatic manure aeration systems. His company, a dealer for Irish company Dairypower, has installed 15 of them on beef and dairy farms throughout the region.
Using a 5- to 10-hp motor, the system pumps air at low pressure into a series of UPVC pipes laid out in a manure pit. These pipes are arranged in zones that, when operating, turn on for just a minute at a time, turning parts of the pit into an air-filled, bubbly lagoon.
The idea is that by aerating and adding oxygen into the pit, it turns it into an active, aerobic environment that reduces toxic gases such as hydrogen sulfide and ammonia, the deadly gases that accumulate in storage but gas off when agitated.
“That's why when you agitate, with no aeration, the gas accumulates and comes out, and it can be deadly. It is heavy and hangs low, and it can shock your lungs,” said Grant Troop, an agronomist and David Troop’s cousin. “Putting the oxygen into the system allows microbes in the system to oxidize the material. So, it's essentially making it safer. It lets the microbes eat it. It's like compost, which you are turning and mixing. You're just adding oxygen.”
More crop nutrients, faster
It may also make nutrients more plant-available, sooner. Research from Wageningen University in the Netherlands has showed that the Dairypower system can increase total nitrogen by 48% and ammonium nitrogen by 71%. Ammonium nitrogen is the preferred nitrogen source for corn.
Widespread independent research in the U.S. has yet to be done to back up these claims.
Still, Slegle said he’s seen a noticeable difference in his crops.
"We've been able to utilize that manure as fertilizer for corn, and it has a lot more availability than, say, my outdoor lagoon,” he said. “That manure is probably 50% worse than what's in the barn, which is constantly agitated. Being in constant suspension, we can pump it any day and the nitrogen is available. We don't lose the ammonia like they do when they bust open an outdoor lagoon. It's definitely got more value to it.”
Eric Rosenbaum, owner of Rosetree Consulting in Shillington, Pa., estimates that between 50% and 85% of total nitrogen in dairy manure is in an organic form that takes years to break down in soil, meaning only a fraction is available for plant uptake right away.
When oxygen is added in a pit, it converts that organic N to ammonium, making it more readily available for plants sooner. Still, other field practices are critical, he said, as ammonium can still volatize quickly if surface-applied, depending on conditions.
“We definitely want to be advocating for more cover crops where we're fall-applying manure, where we're doing winter-applied manure, because if we're changing the structure of the manure and how those nutrients potentially leave the field, we want to make sure we have enough practices in place to prevent that,” Rosenbaum said. “It's true on N, and it's also true on P.”
How much does it cost?
These systems are not cheap. Grant Troop estimates they cost between $6 and $10 a square foot, plus installation, to build. The average return on investment is between five and seven years, he said.
Funding through the Natural Resources Conservation Service could be available under its 629 Waste Treatment code. Right now, Troop said, the program provides project funding of about $111 per animal unit and an additional $22 per animal unit for farmers in business less than 10 years.
Retrofits of existing structures, he said, are easier to get funded because the government places priority on potential environmental problems that need a fix.
Lantz Sourbier, vice president of Nutrient Control Systems in Chambersburg, Pa., a company that develops manure management technologies, said aeration is a no-brainer for slatted floor barns where manure pits sit underneath the structure.
Convincing state and federal officials that these systems can help solve potential air and water problems will be key to making them more affordable, though.
"There has to be a real push for this to get funded,” Sourbier said. “I think it's an excellent alternative to digesters. Digesters are very expensive, and not everyone can do it.”
A fit for draglining
Rosenbaum sees another opportunity to dragline manure in foot-tall corn using adaptive irrigation systems like 360 Rain.
“The ability to have something with less solids is advantageous,” he said. “High-solids manure applied to silage can increase ash content, so this can potentially improve the forage.”
But with any technology, Rosenbaum said, don’t just jump in. It doesn’t work for every farm. For example, if you bed dairy cows using sand or limestone, the system likely won’t work because those materials don’t break down easily and could clog up the piping.
Validation needed
Jason Oliver, a senior Extension associate and dairy environmental systems engineer with Cornell Pro-Dairy, said these systems are well-suited for small-to-midsized farms that aren’t big enough to take advantage of solid-liquid separation, impermeable covers or digesters.
But questions remain.
“We want to validate emission reductions at farm scale and throughout the year,” Oliver said. “There is a lack of U.S. data on our modern dairy farms. Data suggested 50% or more reduction in carbon dioxide equivalent. We also want to better document the fate of nitrogen. There is a documented increase in plant-available nitrogen, but not great side-by-side comparisons. Also, inconsistent data on ammonia and nitrous oxide.”
Rosenbaum said farmers should ask questions and do a lot of research.
"A lot of it depends on your manure management,” he said. “Are you injecting it? Are you surface-applying it? When you change the source, you have a big opportunity to change the amount of nutrients that you're retaining or not retaining. And so I think whenever you adapt a technology, do enough testing, do enough background work, talk to enough people that you understand the ripple effect and what you need to pair with that tech to make it work.”