Greenhouse gas emissions from burning US-sourced woody biomass in the EU and UK

Many national and intergovernmental policy frameworks, including those of the EU and UK, currently treat biomass energy as zero-carbon at the point of combustion, and grant it access to financial and regulatory support available for other renewable energy sources. These incentives have driven a rapid increase in the consumption of biomass for energy, even though its combustion may increase atmospheric concentrations of carbon dioxide (CO₂) for years or even decades to come. Although the CO₂ should eventually be absorbed, the elevated levels in the interim are likely to be incompatible with the 2015 Paris Agreement on climate change. They also increase the risk of reaching a climate tipping point. The treatment of biomass as zero-carbon in policy frameworks will give policymakers in consumer countries a false sense of optimism about the progress being made in decarbonizing their energy supply, while producing countries have no corresponding incentive to reduce future emissions in compensation for the loss of sequestered carbon. Subsidies for biomass energy have been delivered – and seem likely to continue – with little to no differentiation between feedstocks and therefore no effective means of limiting the impact on the climate. In 2019, according to our analysis, US-sourced wood pellets burnt for energy in the UK were responsible for 13 million–16 million tonnes of CO₂ emissions, when taking into account emissions from their combustion and their supply chain, forgone removals of CO₂ from the atmosphere due to the harvest of live trees and emissions from the decay of roots and unused logging residues left in the forest after harvest. Almost none of these emissions are included in the UK’s national greenhouse gas inventory; if they were, this would have added between 22 and 27 per cent to the emissions from total UK electricity generation, or 2.8–3.6 per cent of total UK greenhouse gas emissions in 2019. This volume is equivalent to the annual greenhouse gas emissions from 6 million to 7 million passenger vehicles. Emissions from US-sourced biomass burnt in the UK are projected to rise to 17 million–20 million tonnes of CO₂ a year by 2025. This represents 
4.4–5.1 per cent of the average annual greenhouse gas emissions target in the UK’s fourth carbon budget (which covers the period 2023–27), making it more difficult to hit a target which the government is already not on track to achieve. While emissions are likely to fall by 2030, with the end of government support for power stations converted from coal to biomass, they could rise again thereafter if bioenergy with carbon capture and storage (BECCS) plants are developed at scale. It is 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, with that figure falling back to 5 million–
6 million tonnes in 2030. The 2030 figure could be higher still if further 
coal-to-biomass conversions go ahead. The type of feedstock used in biomass plants is critical. We recommend that only those categories of feedstock with the lowest ‘carbon payback periods’ should be eligible for financial and regulatory support. This is consistent with the Paris Agreement’s aim of peaking global emissions ‘as soon as possible’, and reduces the chance of reaching a climate tipping point. The EU and UK’s current sustainability criteria for supporting biomass feedstocks do not take account of the real impacts of different feedstocks on the climate. We therefore recommend that EU and UK criteria be amended to limit support only to those categories of feedstock with the lowest carbon payback periods: sawmill and small forest residues and wastes with no other commercial use whose consumption for energy does not inhibit forest ecosystem health and vitality. Emissions from any type of biomass used for energy not satisfying the proposed criteria should be included in full in the consuming country’s greenhouse gas totals when judging progress against their national targets and in any relevant policy frameworks, such as the EU’s Emissions Trading System. Since these categories of feedstock have longer carbon payback periods than those eligible for support under our recommendations, this would be an effective way of ensuring that the period during which carbon concentrations in the atmosphere are higher than they would otherwise have been is not simply ignored, as it is under existing policy frameworks.