Hog farmer Mark McHargue is pilot-testing a small scale, home-built methane biodigester – and new digester technology – on his farm near Central City to see if it’s a cost-effective way to capture the energy contained in the manure his hogs produce.
Methane digesters are a proven technology for larger pork operations but their $250,000 and up price tag makes them impractical for small- to medium-sized hog farms.
McHargue, who serves as first vice president of Nebraska Farm Bureau, built his digester in his farm shop for about $5,000, after extensive research that ranged from scientific papers to YouTube videos.
“A methane biodigester is essentially a wastewater treatment facility,” McHargue says. Manure slurry is piped into the digester, which uses part of the methane produced by the manure to fire a boiler. It heats the tank, which enables fast-growing bacteria to break down the manure into a thin liquid. The remaining methane can be used for heat in his barns or to run a generator to produce electricity.
McHargue’s digester uses new technology called “fixed film digestion.” Plastic media inside the tank provide more surface area for the bacteria to grow. With conventional digester technology, he would need a tank five times as large to process the same amount of manure.
The digester also will enable McHargue to change how he applies manure to his crop fields. He plans to apply the effluent from the digester through his center pivot systems, which will save time and money compared to spreading it on his fields.
“We normally could not pump straight out of the barn through the pivot because of the odor,” he explains, but another benefit of the “digested” product is that the bacteria neutralize the odor in the solids. “It has very little odor and it’s not offensive; it kind of smells like dirty dishwater,” he says.
“Using this process is one thing we can do as good neighbors. We’re considering building new facilities to finish pigs and we hope this (odor reduction) will allow us to be a better neighbor.”
McHargue will collect data from the digester this summer. He’s hopeful his experiment will be successful and transferrable to other small hog producers.
Learn more about McHargue’s biodigester here.