Jr. Carney, Blanchard, Tobie M.
Highway construction moves a lot of dirt around, and with construction comes the potential for erosion.
Louisiana’s Department of Transportation and Development uses silt fences and hay bales to slow erosion and improve water filtration and quality, but members of DOTD are investigating the use of compost in filter "socks" for erosion control on state and private highway projects.
"We could use some of these products – either the Filtrexx or a similar product – to accomplish some of these things, have a more effective filtration and runoff reduction and still be cost efficient on the project," said Bert Wintz, a geotechnical engineer with DOTD.
The LSU AgCenter’s Callegari Environmental Center, which specializes in composting, brought together members of DOTD, the state Department of Environmental Quality and representatives of agencies in Texas who use these compost systems.
Callegari Center coordinator Dr. Bill Carney said the compost filter sock system is more effective than conventional methods.
"Silt fences are skimpy. They don’t hold up," he said. "If you get a flow against them, the flow blows them over, so erosion keeps on going and the sediments keep on flowing, but you don’t get that with the filter sock."
With the filter sock system, various types of compost are pumped into large socks, which can used along eroding road banks or placed around construction sites. Compost can be made from yard trimmings, agricultural byproducts such as bagasse or rice hulls, or even biosolids such as highly treated sewage sludge.
"They’ll utilize compost and even wood chips in this sock, and they vary the degree of compost as compared to wood chips in order to vary the degree of filtration," Carney said.
While using compost for erosion control is effective, it also has added environmental and economic benefits.
"It’s a win-win situation," Wintz said. "We can keep things out of the landfill and have an effective product for the transportation highway system."
A unique feature of the filter socks is they do not necessarily need to be removed once they are put on a site.
"It will support plant growth," Carney said. "So you don’t have to go back in and tear it all up and disturb the land once again to get it out of there."
On the economic side, Carney sees potential for economic development.
"I see this just like it did in Texas – that this is going to bring in some cottage industry and have some economic growth," he said.
When the Texas Department of Transportation and Development started using compost systems, there was only one compost supplier. Now there are 18. Carney believes the same came happen in Louisiana if the state’s department increases the demand for compost.
DOTD’s new-product evaluation committee will test the compost filter socks in real situations in order to get it approved for use in future projects.