Table of Contents
- Burning wood emits more CO2 than coal. While young trees generally grow faster than old trees, it still takes decades or even centuries to recapture the additional carbon entering the atmosphere from tree burning – even when compared to coal burning
- The EU’s policy of treating wood burning as carbon neutral is adding CO2 to the atmosphere and encouraging the intensification of forest harvesting. If not amended, a higher renewables target under the European Green Deal could accelerate the problem.
- In 2021, the EU’s Joint Research Centre found that all types of wood used for bioenergy, apart from twigs and tiny branches, increased emissions and damaged biodiversity for at least two decades. Studies in the US suggest that it takes 40 years for the emissions from wood burning to be recaptured by plant growth. In February 2021, 500 scientists wrote to Ursula Von Der Leyen and President Biden calling for an end to wood burning as ‘renewable’ energy.
Biomass in EU law
Bioenergy was classed as a renewable fuel in the Renewable Energy Directive 2009/28/EC and has since grown into a multi-billion Euro industry, providing around 60 per cent of the EU’s total ‘renewable’ energy and XX per cent of global ‘renewable’ energy. In 2018, the consultancy Trinomics estimated that EU member states spent over €6 billion subsidising bioenergy for heat and power – most of which comes from wood pellets which themselves come either from primary wood (that is trees and branches) or from waste wood and so-called forest residues.
The GHG Emissions from Burning Wood
The problem is that burning wood from forests is far from carbon neutral and results – according to the IPCC – in 18% more CO2 as well as more methane and nitrous oxide being released into the atmosphere per KWh of energy generated even than coal (for which wood pellets are considered a low carbon substitute).
The reason that burning wood is considered carbon neutral rests on a flawed assumption that because trees and other vegetation eventually regrow, they can sequester the CO2 originally released in burning. But this does not adequately consider time lags, damage to forest ecosystems or the release of soil carbon – nor does it take into account the effects on global temperatures that additional CO2 in the atmosphere can have, even for a few years.
And there is now mounting evidence that bioenergy use in Europe and North America is hugely underestimating ‘carbon payback’ periods, which can range from several decades to over a century. This was the central argument made by the over 500 scientists – including a former IPPC Vice Chair and a US medal winner – who wrote to Ursula Von Der Leyen, President Biden and the Presidents of Japan and South Korea in February 2021. The same point was made in 2019, ahead of COP25 in Madrid, by the European Academies Science Advisory Council (EASAC), and it’s the basis for an ongoing legal challenge files in the European Court of Justice by Plaintiffs from Estonia, France, Ireland, Romania, Slovakia and the USA; which also highlights the damaging impact that biomass burning has on people.
Is wood burning worse for climate than coal?
Three of the most widely cited, peer-reviewed, papers on the impact of burning wood on atmospheric carbon are:
- Michael T. Ter-Mikaelian, Stephen J. Colombo, Jiaxin Chen, The Burning Question: Does Forest Bioenergy Reduce Carbon Emissions? A Review of Common Misconceptions about Forest Carbon Accounting, Journal of Forestry, Volume 113, Issue 1, January 2015, Pages 57–68, https://doi.org/10.5849/jof.14-016
- John D Sterman et al 2018 Environ. Res. Lett. 13 015007
- Norton, M, Baldi, A, Buda, V, et al. Serious mismatches continue between science and policy in forest bioenergy. GCB Bioenergy. 2019; 11: 1256– 1263.
All are clear that the simple assumptions that the re-growth of trees can compensate for the immediate release of additional CO2 into the atmosphere are flawed.
In the first paper, several scenarios are examined in which the harvesting and burning of live trees substitutes for coal. As the authors say: ‘These studies consistently show that harvesting live trees to produce bioenergy initially increases greenhouse gas emissions which may take decades to centuries to offset [even against coal]’. (p.60). And it is worth remembering that comparing any supposed clean energy to coal is a low bar.
John Sterman and Juliette N Rooney-Varga’s paper yields similar findings: ‘Because combustion and processing efficiencies for wood are less than coal, the immediate impact of substituting wood for coal is an increase in atmospheric CO2 relative to coal. The payback time for this carbon debt ranges from 44-104 years after clear-cut.’
In September 2021, Chatham House and Woodwell Centre researchers provided one of the most detailed studies linking CO2 emissions to specific wood pellets milled in US (all of which were exported to the UK and EU) – estimating that they increased the UK’s emissions by the equivalent of 7 million cars per year. Accounting to their analysis, US-sourced wood pellets burnt for energy in the UK were responsible for 13-16 million tonnes of CO₂ emissions in 2019. This is equivalent to the emissions of 6-7 million passenger vehicles. The researchers also projected that woody biomass sourced in the US and used for energy generation within the EU27 will be responsible for 8 million–10 million tonnes of associated CO₂ emissions in 2025. This will be higher in 2030 if further coal-to-biomass conversions go ahead.
What if forest growth outstrip removals?
The argument is often made that if the annual growth of a forest exceeds total removals, this means that bioenergy from forests is carbon neutral (the ‘sustainable forest management’ argument). This is not correct, and the fallacy is subject to rebuttals in a large amount of academic literature, including in several of the detailed studies produced for the European Commission. It is a good example of the terms ‘sustainable’ and/or ‘renewable’ being misunderstood to be the same as carbon neutral. Ter-Mikaelian explains:
What is essentially happening is that undisturbed part of a forest is being used to offset removals from the stands subject to logging. Mary Booth and Ben Mitchell provide a visual explanation of this in their 2020 report Paper Tiger (p.9).
Removing wood from forests always reduces the rate at which they can sequester carbon and that affects the carbon sink when compared to a situation in which wood is not removed. About 60% of wood burned in the EU is for residential heating. But wood pellet use has jumped by over 50% since 2013, with the EU’s Joint Research Centre highlighting that 37-50% of the EU’s wood used for energy comes from “primary wood” (i.e. whole trees and treetops).
Impact on biodiversity
Even before the Renewable Energy Directive of 2009 provided incentives for bioenergy, the EU was felling nearly two thirds of the net annual growth of its forests every year. Since 2016, Fine-scale satellite data have shown an increase in the harvested forest area of 49 per cent and an increase in biomass loss of 69 per cent across Europe for the period of 2016–2018 relative to 2011–2015. The lead author on that study was Guido Ceccherini, of the EU’s Joint Research Centre. The study (published in the journal Nature) stated that:
In 2021, the EU Joint Research Centre (JRC) produced a 165 page report into ‘The Use of Woody Biomass for Energy Production in the EU’. It found that all types of wood removed from forests for bioenergy, but one, increased emissions by at least two decades while harming biodiversity. Only the removal of slash (twigs and other very small branches) could provide climate and biodiversity benefits within 1-2 decades (p.9). Needless to say, slash is a tiny fraction of the wood used for bioenergy in Europe today and could never be a large proportion.
The threat of biomass expansion in Europe
The think tank Ember published a report in December 2019. “Playing with Fire”, which examines the threat of coal-to-biomass switching in Europe and found numerous plans from coal-plant owners in Europe to switch to wood burning. The report can be found here. Approximately 2,700km2 of forest would need to be cut down every year to feed this new demand if coal power plants are converted to burn biomass on this scale. 36 million tonnes (MT) of wood pellets would be needed, similar to current global wood pellet production.
Read more on ELCI:
Jean-Pascal Van Ypserele: It’s time to end subsidies for burning wood from forests