Evaluation of greenhouse gas emissions and energy recovery from planting street trees

This study evaluated street trees’ potential for energy recovery and greenhouse gas (GHG) mitigation/emissions throughout their lifespans. Trees can mitigate GHG emissions as a result of CO₂ uptake during growth; but GHGs are emitted when the branches and/or leaves are used as compost or fuel for energy production at the end of its life. A 41-year period (1976–2017) of the street trees along the sidewalks of the Tianliao river in Keelong city in Taiwan was taken a case study. The results showed that planting street trees helps mitigate climate change by reducing total GHG emissions (15 661 t CO₂-eq) and producing an amount of renewable energy ((Formula presented.) kWh), that is around 1% of the renewable energy generated by 24 waste-to-energy plants in Taiwan. The GHG mitigation during the lifespans of street trees can efficiently compensate for the GHG emissions that occur during end-of-life treatment (including both incineration and composting). On average, around 40 t CO₂-eq of GHG mitigation would be achieved by planting a street tree. The cost-effectiveness analysis showed that US$223 992 were saved over the study period due to the reduction in carbon tax achieved by the mitigation of GHGs. The results of this study should increase awareness on the importance of planting trees and managing wood waste in environmental protection strategies for mitigating climate change.