More than 250 dairies across the U.S. use some type of anaerobic digester system to generate electricity or renewable natural gas (RNG). The technology adds a revenue stream for the farm, aids in manure management and community relations, provides lower carbon fertilizer options and reduces greenhouse gas emissions, all of which enhance sustainability efforts.
In 2016, Adam Graft, a dairy farmer and veterinarian from Americus, Ga., had his sights set on a high-input, high-output digester to manage manure and reduce odor. Three years later, midway through the engineering and permitting phase to add a D3 RIN digester, he was hit with a Clean Water Act lawsuit from his neighbors. The complaint brought against Graft cited water quality concerns and noxious odors.
“I started this process trying to be a good neighbor, to mitigate odor issues,” Graft says. “A digester was the best and only solution for odor mitigation.” The project is on track to come online before the end of the year.
According to Penn State Extension, controlled anaerobic decomposition can reduce the odors in liquid manure systems, converting the odor-causing organic acids into renewable energy in the form of biomethane. The remaining effluent is liquified, low in odor and rich in nutrients.
“We wanted to increase the nutrients and enhance our fertilizer source for our crops,” he adds. “The added revenue stream is money we don’t have today, so it’s a benefit, too.”
The Growing Market for RNG
According to Mark Stoermann, Newtrient COO, of the 250 dairies currently building or running digester systems, 20% of the projects came online in the last five years.
“With the current demand and programs supporting RNG that number of farms can increase by another 20% or more in the next five years,” he says.
Sustainability is a big reason for the boom, adds David Darr, Vanguard Renewables chief sustainability officer.
“There are a lot of dairy and food companies with goals for reducing emissions, including local and state utilities, and all of that is demonstrating that dairy farmers truly can be part of environmental solutions, and not part of the problems or challenges,” he explains. “With the tremendous interest in RNG as a product and dairy farms to engage, it’s a nice collision point of opportunity.”
Darr points out that RNG provides more opportunities for farms to participate in anaerobic digester technology. Vanguard can support farms milking anywhere from 200 to 300 cows, all the way up to 8,000 to 10,000. Smaller farms can supplement RNG production with food waste from local manufacturers (co-digestion), or partner with neighboring farms to achieve manure-only RNG production.
“At 3,000 cows, you can have enough manure not to add food waste,” Darr says. “Ten thousand cows is the sweet spot for making the projects financially viable.”
Will a Digester Work for You?
Newtrient offers three things to consider when deciding if a digester is a good fit for your operation:
- Suitability. Will a new system integrate well with your current dairy and manure management system?
- Longevity. Does the 20-year lifespan of a digester system match with the future and succession plan for your farm?
- Partners. Identify who will help build out the project in a way that works for all parties involved, so you get a reasonable return and minimal down-time for maintenance and repairs.
