A life cycle greenhouse gas inventory of a tree production system

To understand the role of urban forests as carbon sinks it is necessary to understand their greenhouse gas inputs and outputs over their entire life cycle. Prior to this study, little information was available on the greenhouse gas emissions associated with the early years of trees in nurseries. Using surveys, interviews, and life cycle databases, the GHG emissions of a large-scale nursery were determined. A #5 tree was found to have approximately 4.6 kg CO₂e emissions associated with it. The greatest proportion (44%) came from energy use, both for irrigation and greenhouse heating. GHG emissions from materials (especially plastic containers for planting) contributed 36% and transport-related emissions 16%. The emissions associated with nursery production are minor in comparison with the CO₂ storage rates over the tree’s lifetime.