It is important for policymakers in the EU to control the types of biomass feedstock used – and supported by policy frameworks – in order to limit negative impacts on the climate.
Introduction
The use of wood for electricity generation and heat in modern (non-traditional) technologies has grown rapidly in recent years. For its supporters, the use of wood for energy offers a flexible way of supplying renewable energy, with additional benefits to the global climate and to forests. To its critics, it can release more greenhouse gas emissions into the atmosphere than the fossil fuels it replaces, and it also threatens the maintenance of natural forests and the biodiversity that depends on them. Just like the debate around transport biofuels a few years ago, this has become a highly contested subject with very few areas of consensus.
This paper is one of a series on biomass produced by Chatham House. Between them the papers aim to provide an analysis of the growth of the use of wood for power and heat and a discussion of the debates around its impact on the global climate and on forests. In addition, the series intends to reach conclusions for policymakers on the appropriate treatment of woody biomass for energy in policy frameworks.
The first of this series, Woody Biomass for Power and Heat: Impacts on the Global Climate, is summarized below.1 This paper, Woody Biomass for Power and Heat: Demand and Supply in Selected EU Member States, provides background information on the use of woody biomass for power and heat within the EU, which is currently the main global source of demand for non-traditional uses of biomass. (On the global scale, traditional uses of biomass for cooking and heating, usually on open fires or in simple cookstoves, account for about twice as much energy use as consumption in modern technologies such as power stations, industrial processes, biomass burners, and so on.2 Although in some EU countries some wood is still used in this way, this is not the main focus of these papers.)
The use of biomass for energy has been increasing steadily in many EU member states as a result of the renewable energy targets adopted for each member state under the 2009 Renewable Energy Directive, which set an overall target for renewable energy of a 20 per cent share of total energy across the EU by 2020. Biomass plays a significant part in the EU’s ability to meet these targets for power and heat.
Chapter 2 provides a brief overview of the situation in the EU as a whole. Chapters 3–11 look at nine key member states, selected to include a range of different patterns of use and sourcing of woody biomass: Denmark, France, Finland, Germany, Italy, Poland, Romania, Sweden and the UK. Each chapter includes an analysis of recent, current and projected consumption of woody biomass for power and heat, the main sources of supply, whether domestic or imported, the policy frameworks that support the use of biomass, and information on national sustainability criteria (where they exist), designed to minimize the environmental impact of the feedstock.
Chapter 12 analyses the carbon emissions associated with this biomass use for each country, and examines how these are reported under the current international rules for greenhouse gas accounting, which may lead to ‘missing’ (unreported) emissions. Chapter 13 sets out the prospects for biomass energy use in the EU, in terms of power, heat and supply, while Chapter 14 concludes with recommendations for the EU and member states on the role of woody biomass for power and heat in their future policy frameworks.
Wood for power and heat
Wood in various forms can be used for electricity generation and heat. Primary end-products that are used for this purpose, and are referred to throughout this paper, include:
- Wood fuel (or firewood): simple logs, branches, twigs and so on, produced from logging, or thinnings and coppicings from managed forests. This is the simplest form of wood for fuel and is widely used for domestic heating in many EU countries, particularly in rural areas. Log burners are also popular in some countries for their aesthetic effects (for example, in 2015, it was estimated that one in six households in southeast England burnt wood on open fires or in wood-burning stoves3). Due to its bulk and high levels of moisture (though this can be reduced by air drying), wood fuel tends to be more difficult and costly to collect and transport over long distances than wood chips or pellets.
- Wood chips: medium-sized solid material (typically 30–60 mm in size) made by cutting, or chipping, larger pieces of wood. Wood chips are easier than wood fuel to transport and store but can contain just as much moisture. Globally, most high-quality chips are used for engineered wood products such as fibreboard or particleboard, or for the production of pulp and paper; lower-quality wood chips, with contaminants such as bark or dirt, are more likely to be used for energy, particularly where the transport distances to the installation are relatively low – though the higher the level of contaminants, the greater the problems this may cause for some power stations in terms of slagging or fouling.
- Wood pellets: produced by compressing wood material and extruding it through a die into cylinders (normally 6–8 mm in diameter and 10–30 mm in length). This process, together with the necessary drying of the wood, requires energy input, often derived from burning local mill or forest residues. Compared to wood chips, pellets are more dense and have a lower moisture content, and are therefore better suited to transport and storage. At a rough approximation, two tonnes of green (recently cut, not dried) wood are needed to produce one tonne of wood pellets. Pellets can be made from any organic material, including agricultural wastes as well as wood wastes or roundwood (wood in its natural state as felled), and are widely used for both heating and power generation.
- Wastes and residues: sawmill wastes include bark, shavings, sawdust, trim ends, offcuts and so on, which can be burnt for energy on-site in the mills where they are produced, made into pellets or (depending on quality) used for engineered wood products. Forest residues from logging operations or forest management – stumps, tops, small branches and pieces too short or defective to be used for other purposes – can also be made into chips or pellets, though their quality may sometimes be too low to be used for household heating or in some power stations.
- Black liquor: a waste product from the kraft pulping process used in many pulp and paper mills to produce high-quality paper (mechanical processes generally produce lower quality products). Black liquor is generally burnt in recovery boilers on-site to generate energy for the mill and often also for export to the local electricity grid. Although it is a liquid, black liquor is generally classified as solid biomass, and forms a substantial share of the wood-based fuel consumed in many EU member states with a pulp and paper industry.
These different types of wood feedstock can be used to produce electricity in thermal power stations (sometimes by co-firing with coal, which requires only limited modification of the coal plant), or heat, by burning in open fireplaces, stoves or boilers of various sizes or through heat recovery from electricity generation in CHP plants. Wood can also be gasified and the gas produced then used directly for electricity generation or (after treatment) fed into gas networks for heating or adapted for transport. The vast majority of biogas produced in the EU, however, is produced from agricultural crops or wastes or landfill waste rather than from wood.
Wood is therefore likely to remain the biomass fuel of choice for electricity generation and heat, at least for the next 10 years and probably longer.
While there are alternatives to the use of wood in biomass power and heat, including organic wastes, agricultural residues such as straw, and energy crops such as miscanthus (elephant grass) or switchgrass, these tend to be less energy-dense and more expensive to collect and transport than wood, particularly where the wood used is offcuts, residues and wastes from industries producing wood for other uses such as construction, panels, furniture or paper. Wood is therefore likely to remain the biomass fuel of choice for electricity generation and heat, at least for the next 10 years and probably longer.
Impacts on the climate
The first paper in the Chatham House series, Woody Biomass for Power and Heat: Impacts on the Global Climate, reached the following conclusions:
- Although most renewable energy policy frameworks treat biomass as though it is carbon-neutral at the point of combustion, in reality this cannot be assumed. When burnt for energy, biomass emits more carbon per unit of energy than most fossil fuels.
- It is often argued that, despite this, the use of woody biomass can be assumed to be carbon-neutral because over time the growth of forests after harvesting absorbs the carbon dioxide emitted on combustion. Estimates of this ‘carbon payback period’ vary from a few years, for residues, to decades or centuries for longer-lived forest residues or roundwood.
- The length of the carbon payback period matters, because any short-term growth in carbon emissions increases the likelihood of irreversible climate ‘tipping points’ and are likely to be incompatible with the goals of the 2015 Paris Agreement, which require near-term peaking in emissions and steep reductions thereafter to net zero by mid-century.
- Accordingly, only biomass energy with the shortest carbon payback periods – residues that would otherwise have been burnt as waste or would have been left in the forest or sawmill and decayed rapidly, thus releasing their stored carbon into the atmosphere over a short period – should be eligible for financial and regulatory support. The use of other types of feedstock risks increasing carbon levels in the atmosphere for years or decades.
- In principle, sustainability criteria can ensure that only biomass with the lowest impact on the climate are used. The current criteria in use in some EU member states and under development in the EU, however, do not achieve this as they do not account for changes in forest carbon stock.
- One reason for the perception of biomass as carbon-neutral is the fact that, under international greenhouse gas accounting rules, its associated emissions are recorded in the land use rather than the energy sector, in the country of origin rather than the country of consumption (this may, obviously, be the same). However, the different ways in which land-use emissions are accounted for means that a proportion of the emissions from biomass may never appear in national greenhouse gas accounts, understating its impact on the climate.
The paper concluded that growth in the use of woody biomass for energy posed a significant risk to efforts to mitigate climate change, particularly if policy failed to limit the use of feedstocks to those with the lowest impact on the climate.
Reflecting the lack of consensus on the climate impacts of the use of wood for energy, the paper attracted a considerable degree of criticism from the biomass industry, and some members of the research community.4 Support for the paper’s conclusions was also forthcoming, however, from several sources and further studies. The European Academies Science Advisory Council, for example, concluded in May 2017 that: ‘Compared with some other renewable energy sources, the impact of biomass energy on levels of carbon dioxide in the atmosphere is very poor, and renewable subsidies should reflect this’.5 In the run-up to the European Parliament’s debate on the new Renewable Energy Directive in January 2018, groups of scientists on both sides released open letters arguing the cases for and against subsidies for biomass.6 The debate continues, with areas of contention including the length of an acceptable payback period, which feedstocks should be supported, and the appropriate use of sustainability criteria.
Note on terminology
Bioenergy comes in different forms, and available statistics do not always distinguish between them. Figures for ‘biofuels’ in statistical sources sometimes include all forms of bioenergy (solid biomass, liquid biofuels and biogas), and figures for ‘solid biomass’ often include municipal waste and agricultural residues. Throughout this report, these terms are used:
- ‘Woody biomass’ includes all forms of wood, including pellets, chips, residues, wood fuel and black liquor.
- ‘Biomass’ includes, as well as woody biomass, straw, bagasse, other agricultural residues and animal waste. For these purposes, it does not include municipal waste. (‘Solid biomass’ means the same thing; ‘biomass’ is used here for convenience.)
- ‘Biofuels’ means liquid biofuels usually generated from agricultural sources (such as corn, rapeseed oil or palm oil) and mostly used in transport, though some are used for power generation.
- ‘Bioenergy’ includes biomass, biofuels and biogas.
1 Brack, D. (2017), Woody Biomass for Power and Heat: Impacts on the Global Climate, Research Paper, London: Royal Institute of International Affairs, https://www.chathamhouse.org/publication/woody-biomass-power-and-heat-impacts-global-climate.
2 In 2015 traditional uses of biomass were estimated to account for 9.1 per cent of total final energy consumption worldwide, and non-traditional uses 5.0 per cent; REN21 (2017), Renewables 2017: Global Status Report, Paris: REN21 Secretariat, http://www.ren21.net/gsr-2017/ (accessed 7 Feb. 2018).
3 DECC (2015), Summary results of the domestic wood use survey, https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/517572/Summary_results_of_the_domestic_wood_use_survey_.pdf (accessed 6 Feb. 2018).
4 See, for example, Magrath, M. (2017), ‘Burning wood for energy ignites fierce academic row’, BBC News, 15 March 2017, http://www.bbc.co.uk/news/science-environment-39267774 (accessed 7 Jan. 2018). For the critique, see Cowie, C. et al. (2017), ‘Response to Chatham House report Woody Biomass for Power and Heat: Impacts on the Global Climate’, IEA Bioenergy, 13 March 2017, https://www.chathamhouse.org/sites/files/chathamhouse/publications/2017-04-05-IEABioenergy.pdf (accessed 7 Mar. 2018). See also the author’s response to this critique, Bailey, R. (2017), ‘Re: Woody Biomass for Power and Heat: Impacts on Global Climate’, Chatham House, 31 March 2017, https://www.chathamhouse.org/sites/files/chathamhouse/publications/2017-04-05-ResponsetoIEABioenergy.pdf (accessed 7 Jan. 2018).
5 EASAC (2017), Multi-functionality and sustainability in the European Union’s forests, Halle: German National Academy of Sciences, https://www.easac.eu/fileadmin/PDF_s/reports_statements/Forests/EASAC_Forests_web_complete.pdf (accessed 7 Jan. 2018).
6 EURACTIV (2018), ‘Bioenergy at the centre of EU renewable energy policy’, 15 January 2018, (https://www.euractiv.com/section/energy/opinion/bioenergy-at-the-centre-of-eu-renewable-energy-policy/ (accessed 7 Feb. 2018); and Guardian (2017), ‘EU must not burn the world’s forests for “renewable” energy’, 14 December 2017, https://www.theguardian.com/environment/2017/dec/14/eu-must-not-burn-the-worlds-forests-for-renewable-energy (accessed 5 Feb. 2018).