Making the Most of Manure

Manure from livestock could someday be used as a value-added bioenergy fuel for on-farm heating and power, according to Agricultural Research Service (ARS) scientists studying this approach.

This will be good news to U.S. livestock producers, who need environmentally friendly ways to manage the manure generated by about 96.7 million cattle and 67.7 million hogs and pigs.

ARS agricultural engineer Keri Cantrell, environmental engineer Kyoung Ro, and research leader Patrick Hunt work at the ARS Coastal Plains Soil, Water and Plant Research Center in Florence, S.C. They have teamed up to study how to use a technique called wet gasification to convert wet manure slurry into energy-rich gases and produce relatively clean water.

The team developed a cost-benefit model of a wet gasification technology patented by the U.S. Department of Energy (DOE) to calculate estimated returns, and concluded that liquid swine wastes can generate a net energy potential comparable to brown coal.

The ARS researchers are also investigating methods for producing a type of charcoal—or biochar—called “green coal” from manure. Green coal can be burned on the farm for energy or transported offsite to coal plants for fuel. It can also be added to the soil, a practice that would reduce greenhouse gases by permanently sequestering carbon in the soil in the form of the green coal.

In addition, the scientists are collaborating with the Advanced Fuels Group at the DOE Brookhaven National Laboratory in New York. They are evaluating different catalysts needed to facilitate the conversion of “syngas,” the gas that is produced when animal wastes (and other biomass) are gasified, to liquid fuels.

The Florence scientists want to develop new waste treatment methods and strategies that could be used by almost any farm—from a small family business to a large-scale concentrated animal production facility—to meet all their energy needs.

Read more about this research in the October 2008 issue of Agricultural Research magazine.

ARS is a scientific research agency of the U.S. Department of Agriculture.