To many dairy farmers, manure is a costly waste product. But to others it's a welcome resource. The University of Florida Dairy Research Center in Hague operates an anaerobic digester that treats manure and produces methane gas. For now, the gas heats water used to wash out the milk tanks and lines but in the long run its energy uses are infinite.

A 1,400 pound cow can produce as much as 112 pounds of manure a day. Not surprisingly, manure comes with a laundry list of unappealing attributes. It smells bad. It attracts flies. It's full of nitrogen and phosphorus that when left on the ground can contaminate underlying groundwater and nearby surface waters.

But manure isn't all bad. When processed through an anaerobic digester, the manure from one dairy cow can produce approximately 40 cubic feet of valuable methane gas.

Ann Wilkie, associate research professor with UF's Institute of Food and Agricultural Sciences, sees the digester project as a way to assist a livestock industry pressed to modify its operations to accommodate stricter rules and regulations.

"The animal industry needs to handle new regulations," said Wilkie. "This system is environmentally friendly. It handles manure and gives back renewable energy."

The first step in converting manure to methane is getting the manure from the barn to the digester. Typically, barns located in warm parts of the country are designed with concrete floors so wash water can easily move the manure and flow to flush isles then on to the treatment system.

The wash water is run through a solids separator where bedding and other solids that could potentially clog the treatment system are removed. From the screen, the flushed water is pumped to the fixed-film digester, a tank packed with inert material on which bacteria grow. These bacteria, or biofilm, convert the wastewater to methane, or biogas. While other types of systems are available, the fixed-film digesters can be constructed on a relatively small footprint.

Methane gas produced in the digester, if left untreated, is a potent greenhouse gas. The UF dairy farm originally flared all of the methane; however, a portion of the gas is now used at the farm to fuel water heaters.

Art Darling is with the Sunshine State Milk Producers, a co-op that includes 300 dairy farmers in Florida, Georgia, Tennessee and Alabama. Besides working with the legislature on rules and regulations regarding the dairy business, the co-op provides funding for manure handling research at the UF dairy center.

"In Florida, unlike Wisconsin, barns can be flushed," said Darling. "Total confinement barns are becoming more popular due to environmental reasons and herd health. Confinement barns can include misters and fans. The cows are more comfortable in the summer. They eat more and make more milk."

This means that keeping cows comfortable requires large volumes of water that must be treated. Because of the compact size of the fixed-film digester, they are particularly useful when treating large quantities of water.

Other products of anaerobic digestion are liquid fertilizer and compost, which can reduce or even replace commercial fertilizer. Andy Tangeman, president of Organic Depot, works with dairy farmers to use solids produced from anaerobic digestion as potting soil. He explained that like dairy farms, nurseries are also under the gun to better manage their wastes including nutrients applied to their crops. Commercial fertilizers have long been a source of nutrient loading on the environment.

"I see it as connecting the dots," Tange-man said. "Someone has a problem and someone else has a problem. We connect the dots to find a solution."

Tangeman works with farmers to incorporate systems like Wilkie's into their operations. The processed manure, or compost, is high quality. The digestion process kills weeds and pathogens while leaving nutrients in a state that can be readily taken up by crops.

Wilkie, Darling and Tangeman all see the process of anaerobic digestion of livestock wastes as part of the larger carbon cycle and as a sustainable solution for a myriad of issues. Wilkie feels strongly that the system can and will be taken further with anaerobic digestion being used not only to treat a variety of wastewaters but to produce a viable energy source as well. As a visionary, she sees the potential to reduce our dependency on big oil by not only using manure but specifically grown crops to produce energy.

Farmers could grow crops strictly used to produce biogas. Existing infrastructure constructed for natural gas distribution would then distribute the gas. Unlike natural gas, methane produced from plants is renewable. With a warm environment amenable to flushing dairy farms and crop production, the south could initiate an energy movement based on renewable energy setting an example for the rest of the country.