The Tree BVOC Index

Some tree species emit BVOCs, a precursor of smog. Modifying the species mix in future tree plantings with the goal of reducing BVOCs can be one component of a strategy to improve regional air quality. In 2004, the EPA ruled that tree plantings could be included as an emerging technology to comply with State Implementation Plans. The traditional method of designating species as low, moderate or high emitters and encouraging avoidance of high emitters has a number of limitations, however. The concept of a Tree BVOC Index (TBI) is presented here to improve the accuracy of BVOC computations and to assist with regulatory compliance. The city of Sacramento, California, is presented as an example. The TBI incorporates tree numbers, species emissions factors, mortality rates, foliar biomass, and a geographic region’s targeted emissions reductions to determine if a proposed project is in compliance with air quality goals.