Is woody bioenergy carbon neutral? A comparative assessment of emissions from consumption of woody bioenergy and fossil fuel
21 Under the current accounting systems, emissions produced when biomass is burnt for 22 energy are accounted as zero, resulting in what is referred to as the "carbon neutrality" 23 assumption. However, if current harvest levels are increased to produce more 24 bioenergy, carbon that would have been stored in the biosphere might be instead 25 released in the atmosphere. This study utilizes a comparative approach that considers 26 emissions under alternative energy supply options. This approach
... ons. This approach shows that the 27 emission benefits of bioenergy compared to use of fossil fuel are time-dependent. It 28 emerges that the assumption that bioenergy always results in zero GHG emissions 29 compared to use of fossil fuels can be misleading, particularly in the context of short-30 to-medium term goals. While it is clear that all sources of woody bioenergy from 31 sustainably managed forests will produce emission reductions in the long term, 32 different woody biomass sources have various impacts in the short-medium term. The 33 study shows that the use of forest residues that are easily decomposable can produce 34 GHG benefits compared to use of fossil fuels from the beginning of their use and that 35 biomass from dedicated plantations established on marginal land can be carbon neutral 36 from the beginning of its use. On the other hand, the risk of short-to-medium term 37 negative impacts is high when additional fellings are extracted to produce bioenergy, 38 when the proportion of felled biomass used for bioenergy is low, and when land with 39 high C stocks is converted to low productivity bioenergy plantations. 40 The method used in the study provides an instrument to identify the time-dependent 41 pattern of emission reductions for alternative bioenergy sources. In this way, decision 42 makers can evaluate which bioenergy options are most beneficial for meeting short-43 term GHG emission reduction goals and which ones are more appropriate for medium 44 to longer term objectives.