Life cycle assessment of carbon dioxide for different arboricultural practices in Los Angeles, CA

Although the arboriculture industry plants and maintains trees that remove CO2 from the atmosphere, it uses heavy-duty equipment and vehicles that release more CO2 per year than other similar-sized industries in the service sector. This study used lifecycle assessment to compare CO2 emissions associated with different decisions by arborists to the amount of CO2 sequestered over 50 years for California sycamore (Platanus racemosa) planted in Los Angeles, CA. Scenarios examined effects of equipment and vehicle choices, different operational efficiencies, amounts of irrigation water applied and the fate of wood residue from pruning and tree removal. For the Highest Emission Case, total emissions (9.002 t) exceeded CO2 stored (−7.798 t), resulting in net emissions of 1.204 t. The Lowest Emission Case resulted in net removal of −3.768 t CO2 over the 50-year period. Tree selection and irrigation water management were key leverage points in Los Angeles. Converting residue from the removed tree to wood products resulted in substantially lower net CO2 emissions than did converting it into bioenergy or mulch. Although emissions from vehicles and equipment accounted for less than 6% of the CO2 stored in the tree, substantial reductions are achievable. Arborists can reduce CO2 emissions threefold by converting from high- to low-emitting equipment and vehicles. By reducing travel distances and equipment run-times, twofold emission reductions are possible. Reducing the amount of aboveground biomass pruned from 20% to 10% every five years lowered pruning emissions fivefold.