Development of Biochar Specification Criteria as Soil Amendment for Slopes, Conveyances and Stormwater Treatment Systems, Phase 2

Summary

Stormwater runoff significantly contributes to pollution in roadside environments. To protect the environment and minimize the impact of polluted stormwater, the National Pollutant Discharge Elimination System (NPDES) and State Disposal System (SDS) General Permit require that the first flush of stormwater runoff from new impervious surfaces must be managed onsite through methods such as infiltration, harvesting, or reuse. Due to its high water-holding capacity, biochar has emerged as a promising soil amendment for biofiltration systems aimed at stormwater treatment. In addition to its water retention properties, biochar is effective at removing metals, nutrients (e.g., phosphorus and nitrogen), and organic contaminants (e.g., polycyclic aromatic hydrocarbons, PAHs). However, the effectiveness of biochar can vary significantly depending on the feedstocks used and the pyrolysis processes employed. In phase one of this project, the team investigated the stormwater treatment performance of various biochar products from a single feed stock at a wide range of pyrolysis temperatures. The laboratory results from phase one informed the selection of biochar types most suitable for field application. In phase two, researchers are evaluating the stormwater treatment efficiency of biochar at different particle sizes (up to three) and in combination with various mixed media, such as compost, peat, topsoil and sand. Both lab tests and field implementation are conducted during this phase. The findings from phases one and two will be used to develop a design guide for the production, selection, and application of biochar as a biofiltration media for roadside stormwater treatment.