Time is of the essence when it comes to forest bioenergy

Abstract

Debate continues in this journal on the climate impacts of burning woody biomass from forests. A recent review by Cowie et al. (2021, GCB Bioenergy, 13(8), 1210–1231) addressed what it called ‘misconceptions’ in papers by us and other authors that examined issues of carbon debt and when burning forest biomass for energy could have a net climate benefit. This letter re‐emphasizes the critical importance of the time dimension in assessing impacts, and takes particular issue with Cowie et al's lack of concern over substantial delays in reducing emissions and increasing the risks of crossing climate tipping points.

Biomass—Critical limits to a vital resource

“…Owing to the intrinsic trade-off between harvest and carbon sinks-and in the light of the urgency of the climate crisis-safeguarding forest carbon sinks clearly emerges as a short-term priority over using wood to sustain (unsustainably high levels of) material and energy consumption in the global North. 13,14 This does not entail that biomass use should not contribute to a sustainability transformation, but its scale is strictly limited by the many functions biomass has in ecosystems, e.g., to the availability of residues or ''free area.'' Limitations exist also related to the carbon sinks, e.g., the saturation of the carbon sink once forests reach maturity (usually at the age of several centuries).…”