Get your copy of our weekly print products at any of these convenient locations.

Make captimes.com your all-day, every-day, Madison news home page. Subscribe to get news updates delivered by email. Learn more.

Manure digesters help address the environmental scourge of animal waste

Anita Weier  —  1/14/2009 9:08 am

A dozen Waunakee dairy farmers trudged through snow drifts on the Crave Brothers Farm near Waterloo on a recent wintry Wisconsin day.

Marty Mulcahy, one of the farmers, even brought along his veterinarian, Ross Mauer.

They were all there to see the farm's manure digester, a relatively new use for an existing technology that is seen as a green way to address the high cost of traditional waste disposal methods while protecting soil, water and air.

One of the byproducts of a digester is a compost-like substance that can be used as bedding for livestock. Mulcahy was concerned whether the bedding would pose a risk to his cows' health, which is why he brought Mauer along.

But Mulcahy was won over.

"Seeing your cows made me think differently," he told Charles Crave, one of the brothers who operates the family farm. "Your cows are really clean."

"These are some of the cleanest cows I've seen," echoed Maurer. Use of a digester, he added, "might allow my clients and friends to be better stewards of the land."

The tour of the Crave farm digester, which was installed in February 2007, was organized by Dane County officials who hope local farmers will buy into the idea of sharing use of a community digester, a proposal being pushed by County Executive Kathleen Falk. She put $1.1 million in her new budget for a Waunakee-area digester and identified another possible digester in the Black Earth Creek watershed as a top priority when asking for money from President-elect Barack Obama and Congress as part of the federal stimulus package that is expected to include aid for municipalities.

Local farmers are a bit wary of the proposal, however, since it's not yet clear who would own the Waunakee digester, who would run it, or whether the county would be officially involved.

But no one denies that there has to be a better way of dealing with animal waste -- a major source, many say, for much of the runoff and groundwater pollution that contaminates area lakes, streams and, in some cases, wells.

The biggest source of nutrients entering the lakes in the Yahara River watershed is livestock manure, according to the Nelson Institute for Environmental Studies at UW-Madison.

Moreover, as climate change produces more extreme rain events -- the Madison area has had eight 3-inch rainstorms in this decade, up from two heavy rains per decade in the past -- more phosphorus-rich soil will be headed into the Yahara lakes, warns Pete Nowak of the Nelson Institute.

According to the state Department of Agriculture, Dane County's 50,000 milk cows produce 120 pounds of manure per cow per day, or 6 million pounds per day. Looking statewide, Wisconsin's 1.25 million milk cows, along with other livestock, produce enough manure to fill Camp Randall daily, according to a 2003 article in the journal Dental Clinics of North America that named animal waste as one source of human resistance to antibiotics.

Manure left in fields deposits nutrients, including phosphorus, in the soil. When mixed with water, that soil can run off into nearby water and cause the growth of the kind of smelly, sometimes toxic algae that has plagued the Lake Mendota watershed. Moreover, huge manure lagoons that hold manure cleared from barns can fill quickly. When they reach capacity, farmers have to transport the excess to distant fields for spreading, often at great expense.

Spreading manure on fields can be especially harmful to the environment when the ground is frozen; under these circumstances the manure can't be absorbed and runs off into nearby streams. That's what happened in 2001 when a manure spill entered Black Earth Creek, killing thousands of trout. The accident got a lot of publicity and helped jumpstart discussions about the link between lake health and manure disposal.

"Blue-green algae is the biggest negative for the lakes, phosphorus is the biggest factor in algal blooms, and phosphorus from livestock is a major factor," said Topf Wells, an assistant to Falk. "This digester would be a huge step for our lakes."

The digester on the Crave farm is a huge stainless steel above-ground heated tank that uses bacteria to change manure from the farm's 1,000 cows into methane gas that produces enough electricity to power 400 homes; it also produces bedding for cows and fiber for potting mix. Additionally, the digester returns a reduced amount of liquid manure to a lagoon, so the farmers get what they need to fertilize fields.

The digester envisioned by Dane County officials would remove 19,800 metric tons per year of heat-trapping greenhouse gases and produce valuable electricity or natural gas. But it would also go a step beyond the traditional digester process by removing phosphorus. Some parts of Wisconsin are short of phosphorus, but Dane County now has an oversupply.

"We are suggesting a cooperative scale beyond a digester itself that would produce added-value products," said Dick Lathrop of the Nelson Institute. "Liquid waste can be further treated to strip out nitrogen that farmers need so phosphorus could be sold to potato-growing regions in central Wisconsin."

Environmental leaders say setting up a community manure digester as a pilot project near Waunakee could benefit the rest of the county and the entire state. (Currently there are 22 digesters operating on 17 farms throughout the state that are larger than the typical Dane County farm.)

"If this experiment is successful, if we can work out the engineering and the economic and social aspects, we could have seven or eight digesters in the county to increase the economic viability of farms," Nowak said.

But while the Waunakee farmers were impressed by the digester they saw on the Crave farm -- which was built and is operated by a private concern, Clear Horizons LLC of Milwaukee -- they are worried about the financial implications of a shared digester.

"We need to find a comfort level for the farmers where they feel they can afford it," Waunakee farmer Jeff Endres said prior to the tour. "They have a lot invested right now, and can't take on a risky business proposition."

According to a feasibility study completed by Strand Associates in 2008, the kind of digester under consideration would cost from $6 million to $13 million to build. That is a bit pricier than the cost of traditional digesters that don't remove phosphorus, but the amount includes the additional potential costs of acquiring land and installing pipes and pumps to move manure. Roads would also have to be improved if trucks are used to haul some of the manure.

The Waunakee farmers recognize that a shared digester would give them the opportunity to take part in something they probably couldn't afford on their own. But several fear county control.

"We don't want county ownership," Endres said. "The government is not as efficient and could put limitations on farmers." Endres said he could, however, envision the county playing a role in the removal of phosphorus and transfer of manure.

Farmer Dale Helt said it would be best if the farmers owned at least 25 percent of the digester.

"I am very interested in this project, but I don't know if the people of Dane County want tax dollars going toward this," said farmer Chuck Ripp.

The Waunakee farmers remain wary, but do see the potential value of a manure digester, for the environment and their bottom lines. "We don't want to put anything in the lakes," said one.

Dane County officials stress the long-term benefits to farmers of the potential facility. It is costly to haul manure long distances and sometimes difficult to find land to spread it on. Plus, if the federal government establishes a carbon tax (a fee on greenhouse gas emissions), farmers could be at greater financial risk.

Moreover, possible sale of byproducts could produce extra income.

"You have to make your life better," added Helt. "No one will do it for you. We're businessmen more than farmers nowadays."

Dane County has been laying the groundwork for the proposed community digester since 2006, when an advisory committee was appointed. Strand Associates is now writing a detailed plan.

"We are developing a plan for a community centralized manure management facility that would generate renewable fuel, solids that could be used for fertilizer or other purposes such as fiberboard, and water that could be used for irrigation on the farms," said Randy Wirtz of Strand Associates.

The county selected farms in the Waunakee area for a possible site after the feasibility study found that the Waunakee farms offered more advantages and better long-term cost-effectiveness than an alternative site near Middleton. The Waunakee farms are closer together so manure could potentially be pumped instead of hauled to the digester.

The farmers would pay for use of the facility, but ownership is yet to be decided -- the county could own it, help fund it, or a third party could be involved, according to Wirtz.

"I envision a bidding process, soliciting proposals from third parties that want to own and operate a facility," he said. Falk spokesman Wells predicted the same at a recent conference on the Yahara lakes.

Dan Nemke of Clear Horizons said the Milwaukee-based company would like to be involved in the Dane County operation in some way, though it prefers an arrangement like the one it has on the Crave farm, where it owns and manages the digester.

Kevin Connors, director of land and water resources for Dane County, says it is time for farmers to step up to the plate.

"We are trying to strengthen the livestock industry so it can continue to survive in the county, while we protect water quality," he said. "To go to the next step, we need to get a little more commitment from the farmers."

The dairy barns and milking parlor on the Crave Brothers Farm have slotted floors that sit atop manure channels; with the help of gravity, the manure flows through the channels to a 30,000-gallon collection tank.

From there is it pumped into the digester, where the heated manure is circulated by mixers and "cooks" for 30 days, decomposing and releasing biogas, primarily methane, which collects at the top of the tank. The biogas is then pumped to an engine that burns it as fuel, turning a generator that produces power for the digester system, and provides excess power that Clear Horizons sells to We Energies.

The process also produces a more environmentally friendly form of liquid manure that can be used as fertilizer.

Stored in a lagoon until it can be spread on fields, the liquid manure is more accessible to plants than solid manure and adheres more tightly to soil. Waste whey from the Craves' cheesemaking business is also disposed of by mixing it with manure that goes into the digester.

The energy created by the digester heats the farm office and maintenance shop, as well as the digester itself and its control room, pump room, separation room and generator room.

The fibrous byproduct of the digestion process is composted into a substance resembling soil. The Craves buy about half of it for bedding from Clear Horizons, which puts the rest into its Energro Potting Mix.

The system is automated and can be monitored via the Internet from elsewhere. If an engine or pump stops, the problem can generally be corrected by computer, though sometimes a person has to clear an obstruction in the pump or fix something else.

This is the first digester that Clear Horizons has installed and it is profitable. At this point it's doing "a little better than break-even," said Nemke, although the economics are expected to continue to improve as technology develops and energy costs rise.

"We spent the last year and a half learning and improving the operation to make sure what we could expect," Nemke said. "Now we are starting to market the system and would like to build more."

The company is also doubling the size of the operation on the Crave farm by building a second digester and a larger generator.

"It cost us about $2 million to build the first phase, and the second phase will cost slightly less," Nemke said. "We are looking at an eight to 10-year payback."

Charles Crave is a satisfied customer.

"We have a good bedding source for cattle as well as reduced odor and a better fertilizer product to apply to the field," Crave said. "We think this is the right thing to do and the right direction for our business."

---

Pilot project turns waste into pellets

Dane County is not the only Wisconsin county trying to turn livestock waste into a profitable, non-polluting business. A project in Brown County has started to convert agricultural, municipal and industrial wastes into a fertilizer in pellet form.

Brown County helped form the public-private partnership because of surface and groundwater contamination, a lack of cropland for spreading manure and high waste disposal costs borne by the agricultural industry.

Brown County governmental entities, private businesses and the University of Wisconsin-Green Bay raised $245,000 to launch the pilot project. The Fertilizer Equipment and Engineering Co. in Green Bay produces the fertilizer pellets in its lab.

"We have a combination of waste generators and potential end users of a pelletized product, as well as the FEECO technology to make the fertilizer," explained Brad Holtz, an agronomist with the Brown County Land Conservation Department, which is facilitating the project.

Currently the Green Bay sewerage district incinerates its solids and landfills the ash, but Green Bay Dressed Beef and JBS Packerland -- both meat packing plants that slaughter animals -- spread their materials on the land, Holtz said.

The partnership has started working with 5-gallon samples of waste from various producers. The samples are analyzed, dried and granulated individually to make sure that the pellets will hold together initially but dissolve when applied to the land.

"We are hoping to come up with a process where we can manufacture fertilizer and market it so less organic material is loaded on the land in northeast Wisconsin," Holtz said.

The partnership has put together a marketing and business plan, and one of the business models is based on dairy cattle. The technology could do much to solve liquid manure disposal problems for large dairy operations, according to Holtz.

"You can't haul liquid cow manure very far, but if you applied this technology to dairy farms we would try to find a location with enough animals to justify the cost for farmers." About 11,000 dairy cows would be sufficient.

Holtz said the partnership now knows that waste can be successfully turned into pellets.

"We took a wastewater sludge from one of the meat packing plants and dried it in an oven, and then put the material in a pan pellitizer that goes around and around while the fine particles aggregate. After they reach the desired size of pellet, the pellets are dried once more," Holtz said. The pellets are then bagged or stored in bulk.

Now the coalition will determine from end users such as Ag Ventures, a retail agronomy company that sells fertilizer and other farm products, exactly what their customers want the pellets to do.

Some of the materials only need to be dried and granulated as they are. But others need to be ground up and combined with a bonding agent for stronger pellets.

"Our next step would be to make large enough batches to test the product in the field this spring," Holtz said. "A year from now, we could be building a plant."

Anita Weier  —  1/14/2009 9:08 am