Energy from woody biomass can be very positive for the climate, particularly when applying sustainable forest management practices, and when the biomass is used efficiently (such as in combined heat and power plants and biorefineries).
Considering the crucial role of forests to the climate and many other ecosystem services, sustainable forest management is key to maintaining healthy and productive forests, and for controlling harvest levels so as to maintain or increase carbon stocks in forests*.
Within this overall framework, efforts to increase global forest area through reforestation and afforestation, and management strategies aimed at maintaining or increasing carbon stocks, while also producing an annual sustained yield of timber, fibre and energy from forests are very important for climate change mitigation; these strategies contribute to replacing carbon-intensive materials and fossil fuels, which is crucial in future decarbonisation strategies.
Most woody biomass sourced for energy is a by-product or residue of forestry operations and forest industry. Examples from forest management include thinnings, diseased or low quality trees, tops and branches; examples from forest industry include shavings, sawdust, bark and black liquor. Generally, the primary forest sector aim is to produce high value products, such as sawnwood and wood panels, or pulp and paper. Using by-products and residues for energy has typically been found to achieve climate change mitigation benefits in the short term. It is not recommended to use long-rotation high quality stemwood for energy**, or cutting entire forests to generate bioenergy. Nevertheless, lower-value roundwood from short rotation forestry, thinnings, diseased or low quality trees should not be excluded.
Some people are puzzled about how bioenergy can contribute to climate change mitigation because burning biomass emits carbon dioxide (CO2). Read more …
Bioenergy is commonly said to be “carbon neutral”, but this is an unhelpful term because it is ambiguous, and used differently in different contexts. Read more …
Another important issue which is often raised is the asynchrony between the timing of emissions and sequestration, particularly when biomass is obtained from long rotation forests, where a stand takes decades to regrow. Read more …
Biomass extraction for energy is one of many interacting factors influencing the development of forest carbon stocks. Read more …
* Sustainable forestry is vital for many reasons – also from a carbon balance perspective. Valuable forests need to be protected and forestry methods in production forests need to be sustainable. To determine whether a forest system is managed sustainably requires consideration of a wide range of factors, which together determine a forest’s biodiversity, productivity, regeneration capacity, vitality and potential to fulfil relevant ecological, economic and social functions. Considerations beyond climate effects of woody biomass use for energy are however outside the scope of this FAQ.
** In practice, high quality stemwood is not used for bioenergy on a significant scale, because the paying capacity of saw mills and other users of high quality stemwood is much higher than prices that can be paid by the bioenergy industry, even when taking current subsidy levels for bioenergy into account.
link to the full brief: FAQ_WoodyBiomass-Climate_final
Cowie A, Brandão M (2017): IEA Bioenergy Task 38 – Climate change effects of biomass and bioenergy systems. Article in IEA Bioenergy News Vol 29, Number 2, December 2017.
Bioenergy: Is it good for the climate? Annette Cowie, webinar presentation, 21 April 2016 http://www.ieabioenergy.com/wp-content/uploads/2016/01/Bioenergy-is-it-good-for-the-climate-A-Cowie_IEA-Bioenergy-webinar-21Apr2-16.pdf
IEA Bioenergy (2017): Response to Chatham House report “Woody Biomass for Power and Heat: Impacts on the Global Climate” http://www.ieabioenergy.com/wp-content/uploads/2017/03/Chatham_House_response_supporting-doc.pdf
IEA Bioenergy (2013): On the timing of greenhouse gas mitigation benefits of forest-based bioenergy http://www.ieabioenergy.com/wp-content/uploads/2013/10/On-the-Timing-of-Greenhouse-Gas-Mitigation-Benefits-of-Forest-Based-Bioenergy.pdf
European Forest Institute (2016): Forest biomass, carbon neutrality and climate change mitigation. http://www.efi.int/files/attachments/publications/efi_fstp_3_2016.pdf
IEA Bioenergy Task 38 (2013): Answers to ten frequently asked questions about bioenergy, carbon sinks and their role in global climate change http://www.ieabioenergy.com/wp-content/uploads/2013/10/13_task38faq.pdf
IPCC assessment report 5, chapter 11: Forestry (2014) https://www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_full.pdf
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Parish ES, Dale VH, Kline KL Abt RC (2017): Reference scenarios for evaluating wood pellet production in the Southeastern United States. WIREs Energy and Environment. e259. doi: 10.1002/wene.259. http://itp-sustainable.ieabioenergy.com/wp-content/uploads/2017/11/Parish-et-al.-Reference-scenarios-for-evaluatingwood-pellet-production-in-SE-US.pdf