Rain gardens are increasingly popular with homeowners and municipalities and are mandatory for many communities nationally. USDA scientists are finding ways to improve rain gardens so they not only reduce runoff but also keep toxic metals out of storm drains.
Rain gardens are plantings in depressions that catch storm-water runoff from sidewalks, parking lots, roads and roofs. Rain gardens come in various shapes and sizes, from large basins carved by front-end loaders to small, artificial, streambed-like formations complete with pebbles. Rain gardens not only slow down water to give it time to soak into the ground and to be used by plants, but they also filter out sediment and chemical pollutants.
Plant physiologist Rich Zobel at the USDA’s Agricultural Research Service Appalachian Farming Systems Research Center, and research associate Amir Hass of West Virginia State University, are working to improve rain gardens. They are collaborating with ARS hydrologist Doug Boyer and ARS soil chemist Javier Gonzalez as well as colleagues at the ARS Southern and Eastern Regional Research Centers.
The scientists at the SRRC found that poultry litter biochar-activated carbons created from the charred remains of poultry litter is a powerful pollutant magnet. It can attract heavy metals such as copper, cadmium and zinc, which are ordinarily tough to snag from wastewater.
ARS chemists Isabel Lima and Wayne Marshall (now retired) at the SRRC developed the ARS-patented method for turning agricultural bio-waste into biochar. They created the biochar by subjecting poultry litter—bedding materials such as sawdust, wood shavings and peanut shells, as well as droppings and feathers—to pyrolysis, a high-temperature process that takes place in the absence of oxygen.
Hass and colleagues are testing the poultry litter biochar as well as other farm and industrial byproducts at two demonstration rain gardens in the Beaver, W. Va., area, as well as at plots at a county landfill and a mineland reclamation site.
Their research can be found in the November/December 2010 issue of Agricultural Research magazine.