Systematic Review and Meta‐Analysis of Life Cycle Assessments for Wood Energy Services

Abstract

SummaryEnvironmental impacts of the provision of wood energy have been analyzed through life cycle assessment (LCA) techniques for many years. Systems for the generation of heat, power, and combined heat and power (CHP) differ, and methodological choices for LCA can vary greatly, leading to inconsistent findings. We analyzed factors that promote these findings by conducting a systematic review and meta‐analysis of existing LCA studies for wood energy services. The systematic review investigated crucial methodological and systemic factors, such as system boundaries, allocation, transportation, and technologies, for transformation and conversion of North American and European LCA studies. Meta‐Analysis was performed on published results in the impact category global warming (GW). A total of 30 studies with 97 systems were incorporated. The studies exhibit great differences in their systemic and methodological choices, as well as their functional units, technologies, and resulting outcomes. A total of 44 systems for the generation of power, with a median impact on GW of 0.169 kilograms (kg) of carbon dioxide equivalents (CO2‐eq) per kilowatt‐hour (kWhel), were identified. Results for the biomass fraction only show a median impact on GW of 0.098 kg CO2‐eq * kWhel−1. A total of 31 systems producing heat exhibited a median impact on GW of 0.040 kg CO2‐eq * kWhth−1. With a median impact on GW of 0.066 kg CO2‐eq * kWhel+th−1, CHP systems show the greatest variability among all analyzed wood energy services. To facilitate comparisons, we propose a methodological approach for the description of system boundaries, the basis for calculations, and reporting of findings.