This statement addresses the issue of the timing of greenhouse gas (GHG) emissions and carbon sequestration when biomass from existing managed forests is used for energy to displace fossil fuels. When a stand is harvested and used for energy the carbon that was earlier sequestered during growth is emitted to the atmosphere, and is again sequestered if the stand regrows. In long rotation forestry, carbon is sequestered by the growing stand for many decades before harvest takes place – and after the harvest it may take many decades before the harvested stand reaches its pre-harvest carbon stock.
The difference in timing between emission and sequestration of forest carbon that is observed on a forest stand level has caused some to express concerns about the climate mitigation potential of forest bioenergy. In order to fully understand the climate change effects of bioenergy from existing forests, it is important to consider the entire forest landscape and the wide range of conditions within which forest bioenergy systems operate, long term as well as short term effects and climate objectives, and the interactions between human actions and forest growth. Rather than concentrating on the timing of emissions and sequestration, it is more relevant to focus on assessing the contribution that bioenergy from existing forests may make to the establishment of renewable energy systems that can provide a GHG-friendly energy supply into the future.
Full Paper: Timing Statement Page
Download Paper: On the Timing of Greenhouse Gas Mitigation Benefits of Forest-Based Bioenergy.pdf