Near Bedford, Ind., Banks and Schwab are working with the EPA and Indiana Gas Co. to compare the efficiency of several bioremediation methods at a contaminated site at a coal-to-natural gas refinery. Their joint efforts have become a demonstration project for natural gas manufacturers nationwide.
At Bedford, the Purdue researchers have planted grasses and poplar trees on one part of the site to hasten the degradation of the soil pollutants. The EPA is treating other parts of the site by composting soil, land farming (adding nutrients to soil with tillage), or letting natural processes work to degrade the contaminants. During the next few years both EPA and Purdue will compare the cost and speed of each clean-up treatment.
Banks' graduate student Tom Spriggs, from Bargersville, Ind., oversees the Bedford phytoremediation project. The work will become the basis for his doctoral thesis.
The biggest challenge at any site comes in finding the right plant for the job, Schwab says. Part of the challenge comes in matching plants to climate. For example, plants that thrive in southern Indiana may not make it through hurricanes or the heat of an east Texas summer.
Another part of the problem is finding plants that survive in contaminated areas and at the same time encourage microbial growth. Banks and Schwab have worked with crop scientists to find plants that work best with microbes to break down petroleum. No one yet has a complete list of the best plants for the job, Banks says, although researchers have identified some characteristics that make plants good at phytoremediation.
"For this method to work, we've got to get the roots in contact with the contamination," Banks says. "Sod-forming grasses work well in certain situations, because they have a large root surface in contact with the soil."
In field tests, the researchers found that fescue and Bermuda grass work well. Clovers and alfalfa also look pro
Contact: Rebecca J. Goetz