Recycling Roadway Deicing Salts Using Pyrolysis of Halophytic Feedstocks to Produce Biochar for Roadway Application.

Deicing treatments are applied to roadways in cold climates to improve travel safety. Currently the most widely used and cheapest deicing material is NaCl. Unfortunately NaCl is highly mobile in aqueous solution, corrosive, and toxic to plants and wildlife in high concentrations. Salt corrodes bridges and vehicles and in the spring, deicing salts wash into habitats and watersheds adjacent to roadways. Our research will determine whether it is feasible to collect and recycle deicing salt by planting halophytic plants adjacent to roadways. Through pyrolysis, halophytic feedstocks harvested along road frontage will be processed into biochar, a stable carbon-rich solid created by burning feedstock under low oxygen, while producing biofuel in the process. We are evaluating candidate halophyte species for their suitability in producing saline biomass in road easements. The biochars produced from high-yielding halophytes will be tested for their ability to chemically melt ice (using a modified SHRP ice melting test), to physically melt ice through albedo heating, and to improve traction by increasing friction. Preliminary results suggest that switchgrass (Panicum virgatum ‘Shawnee’) and western wheatgrass (Pascopyrum smithii ‘Barton’) may be promising candidate halophytes for sequestering NaCl. Although saline biochar does not melt ice as effectively as NaCl, it has superior albedo heating properties. Biochar may also be useful for increasing traction on roadways, sequestering carbon, and improving soils along roadways.