Pungent power: there's a spark of light in manure--it can make electricity.

Ah, the aroma of livestock. As farms grow and cities sprawl, the control of animal waste is becoming a greater challenge for many areas. Approximately 250 million dry tons of animal manure are produced each year in the United States.

Much of it is used for fertilizer, but the remainder is stored in waste ponds where neighbors often complain about odors and the possibility of water contamination.

One potential solution is anaerobic digesters--essentially small-scale power plants that can be built on livestock farms. As it decomposes, manure creates methane that is basically unrefined natural gas. The small power plants can burn this fuel to create electricity. And anaerobic digestion significantly reduces the amount of waste, odors and pathogens.

"Anaerobic digestion is a very effective means of controlling odors from livestock," says Ed Lewis, senior deputy director at the Colorado Governor's Office of Energy Management and Conservation. "If some of the waste is used for fuel, then a farmer can build a smaller waste pond and save a commensurate amount of money. Reducing waste not only eliminates odors, but also frees up valuable land for other operations."

He reports that this process also helps control the release of methane into the atmosphere. "That's a concern for some people 2because methane is 20 times more potent than carbon dioxide in terms of how it can degrade our atmosphere."

Environmental concerns and regulations, Lewis says, are mostly driving this technology because it still is not widely cost-effective, especially for small farms.

A hog farm in Colorado is using anaerobic digestion to successfully control odors and generate electricity.

State law sets limits on the concentration of pungent hydrogen sulfide allowed in the air at a certain distance from a waste pond. By burning manure to generate electricity, this farm of approximately 5,000 hogs has been able to comply with the state's air quality standards while simultaneously generating nearly one-third of its own electricity needs. Lewis believes that with some fine tuning, the farm could generate more than 50 percent of its electrical needs.

FROM WASTE TO POWER

Anaerobic digestion is a form of renewable biomass that uses organic by-products like corn and sugar cane stalks, wood waste and even methane from landfills to generate power.

Wisconsin's largest utility, We Energies, relies on a variety of biomass projects for a portion of its power. Three landfills generate enough methane to provide nearly 25 megawatts of power while two anaerobic digesters, one using cow manure and a second using duck manure, have a combined generation capacity of slightly less than 1 megawatt. (One megawatt is enough electricity to power 750 to 1,000 average U.S. homes.)

"Although these projects are at an early stage of development, our experience with them so far is encouraging," says Patrick Keily, a renewable energy project manager for We Energies.

The company is expanding its use of biomass and has requested proposals for 25 megawatts of additional electric generation within the next few years.

These biomass projects help the utility meet Wisconsin's renewable portfolio standard that requires utilities to use renewable energy to provide at least 2.2 percent of their total power by 2011. (Fifteen states currently have similar legislation although the percentages vary from 1 percent to 30 percent.)

"The portfolio standard was one reason we started using biomass," Kelly says. "But We Energies is committed to using even more renewable energy. We have set our own goal of achieving 5 percent by 2011."

BIOMASS FACTS

* The United States gets approximately 37 billion kilo-watt hours of electricity from biomass. That's about 2 percent of our nation's total and more than the entire state of Colorado uses annually.

* There are currently 66,000 jobs in biomass energy; full development of the technology could result in more than 260,000 jobs by 2010.

* Existing U.S. biomass facilities have the capacity to generate more than 7,000 megawatts of electricity.

* Biomass is the second most utilized form of renewable energy in the United States (hydropower ranks first).

Source: U.S. Department of Energy

Troy Gagliano is NCSL's expert on alternative energy.