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Researchers Find Ways to Turn Manure into Power

08.08.2005

Record oil prices and incentives to find alternative fuel sources are lighting a fire under research to turn biomass materials such as manure into energy.

Texas Senate Bill 20, signed this week by Gov. Rick Perry, compliments research under way to determine how and where biomass can be used. The new law requires more renewable energy to be developed and used in the next 10 years.

Combining consumer energy needs and agriculture industry trends with the legislation will push the research to become reality, said Dr. John Sweeten, resident director of the Texas Agricultural Experiment Station at the Texas A&M University System Agriculture Research and Extension Center here.

Researchers have long worked with manure as a fertilizer and have studied ways to convert it into energy, but this latest push of legislation and research should result in more energy projects becoming a reality, Sweeten said.

Research is concentrating on finding alternative uses for the growing supplies of manure, Sweeten said. Irrigated cropland use of manure as a fertilizer is dwindling, but the livestock industry is growing.

Other trends contributing to a potential excess are increasing imports of grain-based nutrients to feed the cattle; less irrigation water; and the switch to crops which use less water and require fewer nutrients.

"Things are in reasonable shape now, but in 10, 20 or 30 years from now, we need to have alternate uses that are not based exclusively on land application," he said.

Energy production has been researched for more than 20 years, but "$60 a barrel oil recruits a lot of interest in biomass," Sweeten said.

"The question becomes, how do you convert biomass into energy?" he said.

The solid feedlot waste presents a different challenge than the liquid waste from hog or dairy operations, Sweeten said. Researchers are trying to determine what process and what mix of the product will create the most useable heat and, as a result, energy.

For this study, composite samples of raw/mixed/uncomposted manure from the Experiment Station feedlot at Bushland have been sent for testing at several labs. The manure samples were harvested May 17-June 2 from two types of pens.

One set of pens were paved with fly-ash, a byproduct of the coal-fired power generating industry, and the other manure was from unpaved pens. The manure was composted and test results from the two showed a large difference for several constituents measured, especially ash content, Sweeten said.

Ash, an unusable material as far as energy is concerned, was lower in the composted manure samples from the paved pens than the dirt pens – 20.2 percent compared to 58.7 percent. As a result, the low-ash manure had about twice the organic matter and heating value, he said.

"The low-ash feedlot biomass would be much better fuel than high-ash feedlot biomass," Sweeten said. "The problem is, there is not that much of it in the commercial feedlots."

Large bulk samples from the compost pile that came from the paved pens will be tested further in a small-scale combustion testing project in College Station.

These test results will focus on using pulverized manure samples as reburn fuel in a secondary combustion chamber to lower the nitrogen oxides and specific metal emissions from coal-firing in the primary combustion chamber, Sweeten said.

Re-sampling will begin next week upon completion of 50 days of composting of the two windrows. The analysis will be repeated on the partially-composted manure to determine changes in fuel quality produced by more than six weeks of composting, he said.

Another research project involves using the byproduct combustion ash as a fertilizer or construction material, Sweeten said.

"By assuring year-round uses of manure, the cattle feed yards in this area could not only stay current on manure harvesting, but the fuel quality of manure improves with more frequent harvest," Sweeten said. "An even greater benefit is that frequent surface manure harvesting by scraping is an accepted method of dust control."