Stormwater runoff from roads contains heavy metals and hydrocarbons created by vehicles. Roadside bioretention systems can filter stormwater to mitigate pollutants entering Minnesota bodies of water. A recent project gave MnDOT and local agencies recommended specifications for biochar, a soil amendment produced from forest waste such as ash trees infested with the emerald ash borer that can be used for stormwater management and other environmental protections.
Biochar properties can vary, impacting contaminant filtering effectiveness. In the first phase of this project, researchers identified optimal processing temperatures and recommended biochar characteristics for maximum stormwater contaminant removal and carbon sequestration. In the second phase, the identified products will be field-tested to support design guidance for amending soils to benefit stormwater management, soil health and climate change.