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Online ISSN: 1757-1707
Associated Title(s): Global Change Biology
Utilizing forest residues reduces emissions
The production of energy from fossil fuels is known to produce greenhouse gasses (GHG), which contribute to climate change. The effect of GHG in the atmosphere can be mitigated in two ways: (1) remove carbon from the atmosphere and store it and/or (2) reduce the amount of GHG released.
The use of energy created from biomass (bioenergy) is thought to achieve both of these objectives; it is a carbon neutral energy source because carbon emitted into the atmosphere through combustion will be absorbed again by the next generation of growing vegetation.
Repo and coauthors questioned that oversimplified ideology. They compared GHG emissions of bioenergy production from forest harvest residues such as dead trees, branches and tree stumps with emissions from fossil fuel (coal, fuel oil and natural gas) use.
GHG emissions from forest residue energy use were calculated and compared to the emissions from fossil fuels (coal, fuel oil and natural gas) use. The forest residue calculations incorporated emissions from the machines used for collecting, chipping, and transporting forest residues in addition to combustion. Fossil fuel emission calculations incorporated the entire fuel cycle (including extraction, processing and combustion). Also included were emissions of forest residues that remained in the forest storing carbon until it is gradually emitted into the atmosphere through decomposition.
The authors found that using forest residues for energy production is neither GHG emission free nor carbon neutral. In comparison with natural decomposition which can take over 100 years, combustion of residues releases carbon into the atmosphere rapidly. Combustion therefore has a larger and longer impact on the environment.
Nonetheless, over the long term, producing energy from forest residues releases less GHG than fossil fuel use, and can therefore serve as a means to mitigate climate change. Energy production from forest residues was found to reduce in the climate impact of the energy production by 21- 77%.
Repo, A., Känkänen, R., Tuovinen, J.-P., Antikainen, R., Tuomi, M., Vanhala, P. and Liski, J. (2011), Forest bioenergy climate impact can be improved by allocating forest residue removal. GCB Bioenergy. doi: 10.1111/j.1757-1707.2011.01124.x Read this paper.