Determining the Carbon Footprint of Tree Production System Components in Field Nurseries using Life Cycle Assessment (LCA)

Life cycle assessment (LCA) applies international standards in determining the carbon footprint of products and processes.  LCA was used to determine the carbon footprint of production system components of field-grown, 5-cm-caliper trees in the midwestern United States.  The production systems of a representative genus of deciduous shade trees and evergreen trees have been analyzed for their impact on the balance of atmospheric greenhouse gases (GHG) during production and during the trees’ useful life in the landscape.  Input products and the use of machinery during the life cycle of tree production result in GHG emissions and constitute a global warming potential (GWP), or carbon footprint (CF).  The dominant contributor to the CF during production of all trees studied to date was equipment use and the majority of that occurred at harvest.  As an example, the CF of Picea pungens (Colorado blue spruce) from seed to landscape was calculated to be 13.558 kg carbon dioxide equivalents (CO₂e).  During a 50-year life in a favorable landscape site, the weighted positive impact of carbon sequestrated by this tree was estimated to be –593 kg CO₂.  After considering the emissions resulting from tree take down and disposal at the end of its life, the net positive impact on GWP of this evergreen tree would be about –431 kg CO₂e.