The feedstock used in biomass plants is critical. Current sustainability criteria do not distinguish between different categories of feedstock and cannot therefore limit the impact of their use on the climate.
Wood pellets produced in the US, imported to the UK and burnt for energy were responsible for 13 million–16 million tonnes of CO₂ emissions in 2019, 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 greenhouse gas emissions from UK electricity generation, or 2.8–3.6 per cent to total UK greenhouse gas emissions in 2019. This volume is equivalent to the annual greenhouse gas emissions from 6 million–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 currently not on track to achieve in any case. While emissions are likely to fall by 2030, with the end of government support for power stations converted from coal to biomass, it could rise again thereafter if BECCS plants are developed at scale.
Since the UK is the predominant European market for US wood pellets, emissions associated with their use in the EU27 are lower: about 3.1 million–
3.7 million tonnes of CO₂ in 2019, rising to a projected 8 million–10 million tonnes by 2025 and falling back again to about 5 million–6 million tonnes in 2030. This does not take account, however, of any increase in the rate of coal-to-biomass conversions, which may follow as EU member states phase out coal use. While the main countries in which conversions are expected to take place are not large importers of US wood pellets, any constraints in domestic supply or imports from other sources could increase demand for US imports. As in the UK, the development of BECCS plants may serve further to boost demand for US wood pellets in the 2030s and 2040s.
The present scale, and likely growth, of wood pellet use in power and heat production in the UK and EU is a direct result of government subsidies. It would not have happened in the absence of financial and regulatory support.
Furthermore, as discussed in Chapter Two, because of the way in which emissions from the use of wood pellets are reported and accounted for in the land-use rather than in the energy sector in national greenhouse gas reports (and therefore in US rather than UK or EU27 reports), almost none of those emissions will be included in the data used to track progress against national targets – for example, in the UK, the five-yearly carbon budgets set under the Climate Change Act, which establishes the target of net zero emissions by 2050. (Any supply-chain emissions taking place in the UK will be included, but these represent a very small proportion of the total.)
As the IPCC and EU JRC have observed, this separation of reporting sectors obscures the real progress countries are making in meeting the targets adopted under the Paris Agreement. By treating biomass emissions as zero at the point of combustion, the system creates a significant incentive for consuming countries to burn wood for energy. Since emissions take time to be reabsorbed by forest regrowth, carbon emissions in the atmosphere will increase for a period of decades to centuries as a result, depending on the feedstock type. At the same time many policymakers in the consumer countries, as well as the wider public, will be given a false sense of optimism about their country’s progress in decarbonizing its energy supply. In addition, there is no corresponding incentive for the producing countries to compensate by reducing their future emissions.
Just as importantly, the treatment of biomass as zero-carbon in policy frameworks has led governments to provide significant financial and regulatory support for the use of biomass for power and heat. While support for biomass may now be falling as other renewables increasingly out-compete it (though it may still be subsidized for coal conversions), biomass is still the dominant source of renewable heat. This support has been delivered, and seems likely to continue, with essentially no means of discriminating between feedstocks with different carbon payback periods. There is, therefore, no effective way of limiting their impact on the climate.
Recommendations
As discussed in Chapter Two, and illustrated in both Chapter Three and the Annex, the types of biomass feedstock used have a significant impact on emissions totals. We conclude, in line with the arguments in the recent EU JRC report, 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 emissions triggering climate tipping points.
This means that eligibility for government support should be restricted to sawmill and small forest residues and wastes that would have no other commercial use and whose consumption for energy does not inhibit forest ecosystem health and vitality (e.g. by removing excessive volumes of forest residues).
Current sustainability criteria in the EU27 and UK do not take account of the real impacts of biomass feedstocks on the climate and therefore should be amended to restrict eligibility. At the same time, much tighter definitions of feedstock categories should be introduced to prevent whole trees being treated in the same way as genuine residues. The new proposals from the European Commission in July 2021 introduce the welcome principle of restricting eligibility by feedstock category, but in reality the categories that the European Commission has proposed will make virtually no difference to outcomes.
The restriction of support to feedstocks that have no other commercial use is an important element of these sourcing conditions. Sawmill residues in particular are used extensively for the manufacture of wood panels and particleboard. It is important that supplies of such residues – which are limited in volume – are not diverted to use for energy, with an accompanying pressure on the wood products industry to find other sources. A review of the supply of woody biomass from the southeastern US to the EU, published by the European Commission in 2015, concluded that, while sawmill residues were in many ways the ideal source material for pellets, US mill residues were already almost entirely utilized by the biomass energy or other industries, and there was very limited room for expansion. At the time there was very little evidence of diversion of residues from wood products to energy, but the biomass energy industry has expanded significantly since that study was conducted. Periodic monitoring of feedstock use and impacts should therefore be implemented to prevent diversion.
On top of this restriction of feedstocks, additional criteria should be included to protect particular types of landscape from the extraction of biomass for energy. The European Commission’s July 2021 proposal to ban biomass produced from land that was classified as primary forest at any time after 2008 is helpful, though limited. It is to be hoped that this measure is adopted.
Other features of EU sustainability criteria should also be tightened. The UK’s adoption of a ceiling on supply-chain emissions of 29 kg CO₂eq/MWh for future contracts is welcome, as it seems likely to restrict feedstocks to domestically-sourced products. Similar limits should be introduced in the EU. Energy efficiency thresholds for new stations should also be increased and extended to older and smaller stations. (At present they do not apply at all to stations below 50 MW thermal input and only in full to those above 100 MW.) The European Commission’s proposals do not affect these criteria. Finally, the Commission’s proposal to extend support for the use of forest biomass in electricity-only installations in coal-dependent regions beyond 2026 will encourage further coal-to-biomass conversions and should be dropped.
In both the EU and UK, feedstock for BECCS plants should be subject to at least the same constraints as for other biomass plants. (The question of which feedstocks should be used for BECCS plants, and their overall impact on land use and carbon balances, is an important one but falls outside this paper’s remit.)
In addition to using sustainability criteria to limit the use of biomass feedstocks, international and national reporting and accounting rules should be amended to support this objective. As discussed in Chapter Two, there is no ideal solution to the problem of double-counting or the question of whether emissions should be reported in the land-use or the energy sectors. We recommend that the IPCC review its current reporting guidelines to address this issue.
More important, however, is the question of how biomass emissions are included in accounting against national targets. Consistent with the use of sustainability criteria to limit biomass feedstocks to those with the shortest carbon payback periods, emissions from any other type of biomass used for energy should be included in full in the consuming country’s greenhouse gas totals when judging progress against their national targets – for example, the UK’s carbon budgets setting a trajectory to net zero emissions by 2050 or the EU’s new target of a 55 per cent reduction in emissions by 2030. These emissions should also be included in full in any relevant policy frameworks, such as the EU’s Emissions Trading System, which currently excludes or zero-rates emissions from biomass.
If these recommended changes to sustainability criteria are implemented fully, non-residue feedstocks would not be eligible for financial or regulatory support, but could still be used. Although their associated emissions should eventually be captured through forest regrowth, as discussed in Chapter Two, this will only take place after a period of decades or even centuries. Including their emissions in consuming countries’ current totals 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.
