At Crave Brothers Farm in Waterloo, Wis., manure from a 2,300-cow dairy and whey from its cheese plant feed a digester that produces electricity, heat and bedding while supplying fertilizer for the fields. Nearly 20 years later, the digester remains a central part of the farm’s operation.
For Mark Crave, managing partner of Crave Brothers Farm and Farmstead Cheese, keeping a digester running takes a long-term commitment. The initial investment is just the beginning.
“You have to look beyond the upfront cost,” Crave says. “You’re making a commitment to maintain it and keep it running for years to come, so you need to be ready for what comes with that.”
The Start of a Long-Term Investment
The digester effort began in 2006, when a Milwaukee electrical contractor approached the Crave family about forming a partnership to build a system at the farm. At the time, Crave Brothers had about 850 cows, but whey from its cheese business helped supplement the manure supply and made the digester viable despite the herd’s smaller size.
A decade after installation, the digester was showing its age, and the cost of upgrades was adding up. The original contractor had returned its focus to electrical contracting, and the digester changed hands. The Crave family faced a decision: invest in costly upgrades or walk away from a system tied to the farm’s manure handling and energy supply.
The family chose to reinvest. In 2017, it took full ownership of the digester and now runs the system with its own staff.
“We decided we couldn’t just walk away from it because it is part of what we do,” Crave says. “The manure system and our hot water system are tied into it. So, we actually went against convention and reinvested in the methane digester.”
Put Whey and Manure to Work
The cheese plant supplies one of the digester’s main ingredients. Whey travels back to the farm, where some whey permeate goes into the cows’ ration and the remaining material feeds the digester.
Manure from the dairy also enters the digester, along with wasted feed and leachate collected from silage piles. Inside the system, bacteria break down the organic material and produce biogas. Crave says gas production tends to increase after harvest, when silage leachate adds to the material being processed.
The biogas fuels an engine that generates electricity sold to the grid. The process also produces heat, which the farm uses to warm the digester along with the farm shop, office and farmhouse.
The electricity produced by the digester reaches beyond the farm, too. Currently, the system generates enough power to serve about 300 homes in the surrounding community.
Adapted System
While the original design helped process manure and whey, it did not fully account for Wisconsin farm winters, Crave says. During freezing weather, manure could freeze before reaching the digester, creating real challenges for handling and maintenance.
As the farm took full ownership in operating the system, it applied its own experience with manure management and equipment to address those challenges. That included making adjustments to manure handling, pumps and preventative maintenance.
“We know how to handle manure and get manure into the thing,” Crave says. “We kind of married both levels of expertise into what works now.”
The digester also helps supply bedding for the herd. Biogas is used to dry separated manure solids, raising their dry matter from about 30% to 50% before they go into the stalls. The liquid manure left after separation is stored in a concrete lagoon and applied to fields under the farm’s manure management plan.
Using digester solids for bedding required some trial and error. The farm stopped using them for about five years because excess moisture created more problems than the bedding was worth.
“We stepped away from using the solids for bedding for several years because they were too wet and we started seeing milk quality issues,” Crave says. “We fine-tuned the drying process to get the moisture level where it needed to be before bringing them back into use.”
Maintenance Comes with the Territory
Keeping a methane digester running takes more than feeding it manure and collecting the gas. Engines wear out, parts need replacing and repairs can affect the rest of the farm’s operations. At Crave Brothers, the family has learned to plan ahead and handle as much maintenance as possible with its own staff.
Currently, the digester is on its third engine. The first two each ran about 50,000 to 60,000 hours. Some replacement parts come from Europe, making advance planning important.
The family has also looked for ways to manage repair costs. When it needed another engine block, the farm sourced a used one from Austria and rebuilt it. Crave says the cost was about half the price of a new block.
“We do carry a lot of replacement parts and just try to be smart,” Crave says. “You have to think ahead about what might wear out and what you need to have on hand, because you can’t always get a part right away.”
Crave says a digester isn’t a system a farm can install and forget about. It requires regular upkeep. Keeping parts on hand helps employees make routine repairs without waiting for deliveries. The crew has also replaced agitators and the digester roof, giving the family more control over repairs.
Getting a digester built is one thing. Keeping it running for the next 10 or 20 years is another. Grants can help with construction costs, but the farm is still responsible for keeping the system running. Crave says farmers need to consider whether they’re ready for that commitment well beyond installation.
Plan for the Long Game
Getting a digester built is one thing. Keeping it running for the next 10 or 20 years is another. Grants can help with construction costs, but the farm is still responsible for keeping the system running. Crave says farmers need to consider whether they’re ready for that commitment beyond the initial installation.
“You have to ask yourself if you’re still going to be happy with that decision 20 years from now,” he adds. “Grants can help cover the upfront cost, but you have to look at whether the investment will still make sense 10 or 20 years down the road. You’re the one who has to live with it, maintain it and keep it running.”
Crave offers three tips for farmers to consider before investing in a digester:
- Visit other dairies with digesters. See how the systems operate day to day, ask about maintenance and talk with farm owners about what they would do differently.
- Ask questions and read the fine print. Understand which materials the digester can accept, the requirements tied to selling electricity, and what happens when equipment breaks down or parts are delayed.
- Make a long-term plan. Look beyond grants and construction costs. Account for repairs, staffing, replacement parts and how the digester will fit the farm 10 or 20 years from now.
He says a digester can serve the operation for decades, but it also requires ongoing investment, attention and a willingness to manage it for the long haul.
