Anaerobic digesters
In 2009, former U.S. Agriculture Secretary Tom Vilsack heralded giant, dome-capped anaerobic digesters as “a win for everyone.”
The systems use bacteria to break down manure. The resulting biogas is burned for heat, electricity or fuel. The dried out, fibrous residue gets spread on soil. Alliance Dairies in Trenton was the first to adopt the tech in Florida but faced repeated challenges with its generator.
Nationwide, federal loans to fund multimillion-dollar digesters have such high delinquency rates, the USDA paused one program that supports them earlier this year.
But Tom Richard, professor emeritus at Penn State University, hasn’t given up on the waste-to-energy dream. “If you've got too many nutrients on a farm, there's a variety of different solutions,” he said, “but anaerobic digestion should definitely be on the short list.”
Pond systems
Researchers test many management techniques at the UF/IFAS Dairy Unit, a commercial operation just north of Gainesville.
One pond system is designed to make a more balanced fertilizer.
The three-stage system separates, settles and treats wastewater, explained Jerry Fankhauser, lead administrator for the unit.
“The third stage is where the concentration of nutrients is at a level that's appropriate for crop production, but not excessive,” he said.
Crews check that by sampling the soil for nitrogen, phosphorus and potassium and adapting its fertilizer recipe accordingly.
Vermifiltration
As the sun rose over Royal Dairy in Washington state, Matias Sjögren strapped into open-toed boots, inched into brown water and wakeboarded across a wastewater pond.
It was a showy stunt for an un-showy product: worms. Sjögren is CEO of BioFiltro, a wastewater treatment company that uses worms to munch on the biodegradable parts of manure. Plants like worm poop better than cow poop, so farmers can apply less and reduce runoff. The system cuts down on methane, too.
The company has four full-scale installations in California, one in Washington and a few in shipping containers at dairies across the country. “The biggest challenge is the cost,” said Gilbert Miito, an assistant professor at the University of Idaho and former BioFiltro employee. “Not many dairy farmers are willing to pay for this.”
