Turning Manure into Energy

 
Turning Manure Into Energy

 

Turkey litter is relatively dry and blended with bedding fiber, making it especially well suited for combustion.

 

Photo courtesy of Steve Werblow

 

Turning Manure into Energy

Steve Werblow


Barriers to the land application of manure – phosphorus-loaded soils, limited land base, high fuel and hauling costs – have raised burning questions for many livestock producers. Some have responded with burning answers: burning the manure as fuel in electrical generating facilities.

Manure combustion is as old as buffalo-chip campfires. Today's manure-burning facilities can't rely on the hot prairie sun to dry the fuel, but the concept isn't much different – there's energy stored in manure solids. What is different is the combustion technology, which has taken two basic forms in the Midwest:

  • Basic combustion, in which manure is burned to produce heat to create steam that turns electricity-generating turbines, and
  • Pyrolysis, in which manure is heated in a high-pressure, low-oxygen chamber to create an oily, combustible syngas (or even biodiesel). A pyrolysis plant is running in Cashton, Wis., on dairy manure, and researchers at the University of Illinois have used the technology to create oil from hog manure.

The net result in either case is a net production of electricity and a substantial reduction in waste to be managed – just pounds of dry ash or char for every ton of wet manure that started the process. Compared to heavy, bulky loads of wet manure, dry ash is cheap to move and easy to apply, opening up a huge new land base for leftover nutrients.

Mark Wiese, who built a manure-fueled power plant on the family dairy near Greenleaf, Wis., with his brothers Dave, Ken and Dick, says the reduction in the volume of end product is dramatic.

“We produce 4,500 to 5,000 semi loads of manure per year,” Wiese says. “Now we reduce that to 18 dump trailers of ash. That's less than two percent of the solids in the manure.

“The only other alternatives out there were anaerobic digestion and composting,” he says of his family's decision to build an Elimanure power plant on their farm. “Each one of those options still left us with liquid effluent to deal with. That means you still have 93 to 94 percent of your initial problems, and you still have the expenses of having to land-apply all that liquid.”

Turkey producer Greg Langmo of Litchfield, Minn., spearheaded the development of a manure-to-energy plant in Benson, Minn., that draws litter from 300 Minnesota turkey operations. He says manure-fueled power plants are exciting because they represent a scalable, regional solution to a regional problem. “A digester is one farm, one guy, one solution,” Langmo says. “This is large-scale, commercially viable, where many people can participate and move excess nutrients out of their neighborhood.”
Pioneering power plants
Langmo found combustion after what he calls a “stern lecture” from county officials on how he and several other producers had been handling their manure. Business as usual was raising eyebrows and raising hackles – it was time to move beyond open trucks and roadside piles. “They told us we better find a solution or they'd find a solution for us,” he recalls.

Today, the Fibrominn plant outside of Benson can generate enough power for 40,000 homes and enough work for 100 employees, fueled by 500,000 tons of turkey litter. An additional 100,000 tons of ash (because it is drier than dairy manure, burned poultry litter yields much more ash) is sold as fertilizer through a local ag supply chain.

Langmo learned about a British company called Fibrowatt in a brief mention in a farm magazine. Realizing that his entire farming operation was threatened by manure handling issues, he invested in a ticket to England to meet Fibrowatt management and see their three British plants for himself. Impressed by what he saw, he came home and started raising money to bring the technology to Minnesota. With an investment by Fibrowatt and bonds to raise the balance of the $200 million it took to create the project, Fibrominn was born. It officially opened in October 2007.

The Wiese brothers found their solution a little closer to home in the $3.6-million Elimanure system, designed by Wisconsin-based Skill Associates. Though their 2,600 owned acres and 2,600 rented acres represented enough land for agronomically acceptable manure application, building a power plant on the dairy reduced their manure movement from an 8-mile radius to about 1,000 feet of pipeline.

Because water comprises more than half of the weight of dairy manure, the Wieses' Elimanure facility dries the manure before heating it in a combustion chamber. That's a big challenge with dairy manure, but the Elimanure design channels heat from the furnace back to the biodryer building to dry the incoming fuel, blowing off the moisture as clean steam. Wiese calls the energy expended in drying the wet manure “parasitic load,” which accounts for 200 kilowatt hours (kw/h) of the power that the facility produces. Still, over the past two years, the plant has produced a net output of 350 to 380 kw/h – enough energy to power 400 to 500 homes, which the Wieses sell to Wisconsin Public Service Corporation, the state's power utility.
Buy octane
A consistent supply of fuel is vital to operate a power plant – combustion facilities are efficient when they are burning continuously. Langmo adds that banks financing big public works projects are especially eager to see a sustainable source of fuel.

Minnesota has plenty of turkey litter. And even if a disease outbreak quarantines producers in one area or forces them to depopulate their flocks, says Langmo, Fibrominn's fleet of 60 semis services a 100-mile radius around Benson, picking up litter from hundreds of farms, so they're likely to reach areas not affected by the outbreak.

Langmo says that the large service area is a hedge against running short on litter. It's also a service to the state's turkey industry. Rather than charging a tipping fee, Fibrominn pays growers for their litter – up to $10 per ton, depending on its fuel quality.

It's not a steady, predictable flow of material, but the plant has a fuel hall, negatively pressured to keep odors from escaping, that houses a five-day supply of liter. In the facility's yard, the company has also stacked scrap wood that can be blended with the litter on the way to the furnace.

And if that's not enough, the system can burn nearly any kind of fiber. Cornstalks, cobs, oat hulls, sunflower hulls, switchgrass, offal, food manufacturing waste, storm-felled trees – whatever the source, the furnace can be adjusted to burn it, Langmo says. “We've got experience burning 75 or 80 different kinds of fuel,” he says.

Though the Wieses' permit only allows them to burn manure produced by their 2,150 milking cows and 2,000 heifers, Mark Wiese says the concept could easily be scaled up for a community-sized operation. “You could certainly put some kind of co-op together with adjoining farmers to put a facility like this in,” he says.

Wiese has also looked at different fuel sources for the Elimanure system. He sees opportunities to build Elimanure plants beside cellulosic ethanol plants, which – like livestock operations – will be saddled with huge volumes of wet, high-fiber waste. He's even gotten calls from local meat packinghouses, which see the combustion chamber as an efficient and effective tool for getting rid of fiber-and-grain-rich paunch.
Fine-tuning
Getting a power plant up and running isn't as easy as flipping a switch and watching the sparks fly. Both the Fibrominn plant and the Elimanure system have experienced challenges and start-and-stop cycles as part of lengthy start-up procedures. Wiese notes that his family's system really needed a bigger combustion chamber and boiler, which are in the works now. Langmo points out that every boiler requires fine-tuning, a careful refinement of airflow, moisture content, particle size, and energy value that goes in to hit the unit's “sweet spot.” It's a lot like tweaking a huge carburetor.

Logistics also require a lot of tweaking. Fibrominn picks up fuel at the whim of the suppliers, not according to the demand at the plant. What's more, biosecurity concerns and company protocol demand that each semi go through an automatic truck wash after dropping off every load.

Despite the challenges, Wiese says operating a power plant – which he expects to evolve into a 40-hour-a-week job for someone at the dairy – will ultimately represent a fraction of the time traditionally spent managing manure, from agitating tanks to land-applying load after load after load.

That's got great appeal for him. “We haven't turned a monetary profit,” Wiese says, “but I haven't spread any box manure on my land in over a year. We burn all that fiber now.”

Langmo adds that burning manure offers an even richer reward for many of the farmers who fuel the Fibrominn plant. “Folks love it that their manure is now a source of renewable power,” he says.

The Fibrominn plant near Benson, Minn., uses its fleet of covered semis to collect turkey litter from farms within a 100-mile radius of the plant. The wide reach allows the company to collect plenty of fuel and to hedge against localized quarantines if disease problems become an Issue.

Photo courtesy of Fibrowatt
Easing the transition

When Mark Wiese looks at the manure-burning power plant on the 50-acre heart of the family dairy, he sees more than just a way to get rid of manure from 4,150 cows. He sees an asset that will ease the farm's transition to the next generation.

“When we transition the farm to the next generation, I don't want to burden them with manure issues,” says the Greenleaf, Wis., dairyman. “Now I can transition the farm without requiring them to have a 4,000- or 5,000-acre land base.”

The Wiese operation, a partnership among brothers, has evolved to include the dairy, the cropland and a trucking business. Adding a power plant just fits right in to the model of diversification, and allows the next generation to take on manageable pieces rather than trying to swallow the whole operation.

“If this can be a stream of income rather than a drain like manure, I can sell my son the 50 acres the dairy site is on, and he can buy feed and trucking services from the other parts of the operation,” Wiese notes.

The Fibrominn plant near Benson, Minn., can convert 500,000 tons of turkey litter annually into enough electricity to heat 40,000 homes.

Photo courtesy of Fibrowatt

The manure is burned to produce steam, which is piped to a turbine.

Photo courtesy of Fibrowatt