Mobile pyrolysis plant converts poultry litter to energy

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A mobile pyrolysis unit that would provide an economical disposal system for poultry litter and produce alternative sources of energy is under development at Virginia Tech in Blacksburg, Va., led by Foster Agblevor, associate professor of biological systems engineering. A test unit is expected to begin operation in November on a poultry farm near Dayton, Va., processing five tons of poultry litter per day into bio-oil, biogas and char.

Poultry litter is a mixture of bedding, manure, feathers and spilled feed. According to Agblevor, current poultry litter uses, such as land fertilizer, are under pressure because of concerns about water pollution from leaching and runoff, and diseases such as avian influenza and mad cow disease. Virginia Tech's self-contained, transportable pyrolysis unit will allow poultry producers to process the litter on-site, rather than hauling it to other locations, Agblevor said. Plus, the thermochemical process destroys microorganisms.

The biogas generated by the portable pyrolysis unit will be used to power the system, Agblevor said, and the bio-oil will be used to heat poultry houses. The char will be used as a low-release fertilizer. The pilot plant will evaluate the reactor design and address other issues that may affect the commercial operation of the mobile unit. How the portable units will be used by poultry growers is being discussed. "There are several proposals from the growers about installation of the units, but that will wait until we have the pilot plant results," he said.

The fast-pyrolysis, fluidized-bed reactor yielded bio-oil at a rate of 30 percent to 50 percent by weight, depending on the litter content. Bedding material consisting mostly of hardwood shavings yielded bio-oil as high as 62 percent by weight. The bio-oil had a relatively high nitrogen content ranging from 4 percent to 7 percent by weight, very low sulfur content (below 1 percent) and was very viscous. The char yield ranged from 30 percent to 50 percent by weight, depending on the source, age and composition of the poultry litter. The char also had a high ash content, ranging from 30 percent to 60 percent by weight, depending on the age and source.

The research is part of an effort to support the agricultural community while managing excess nutrients in the Shenandoah Valley. It is being funded by a $1 million grant from the National Fish and Wildlife Foundation's Chesapeake Bay Target Watershed program.