The growing role of BECCS in mitigation scenarios
The concept of BECCS first emerged in the late 1990s and early 2000s; the term itself was coined in 2003.5 In 2007, for the first time, the Intergovernmental Panel on Climate Change (IPCC), in its Fourth Assessment Report, identified BECCS as a potential option for stabilizing greenhouse gas emissions or as a rapid-response prevention strategy for abrupt climate change. It offered the following caution, however:
To date, detailed analysis of large-scale biomass conversion with CO2 capture and storage is scarce … further research is necessary to characterise biomass’s long-term mitigation potential … and opportunity costs … In particular, present studies are relatively poor in representing land competition with food supply and timber production, which has a significant influence on the economic potential of bio-energy crops.6
In 2011, the IPCC’s special report on renewable energy contained only limited coverage of BECCS and no quantification of its potential. In the same year, the International Energy Agency (IEA) reviewed the potential of BECCS in different forms, including dedicated biomass stations with CCS, co-firing with coal with CCS, and liquid biofuel production with CCS.7 The IEA concluded that the potential technically existed for negative greenhouse gas emissions of up to 10 gigatonnes of carbon dioxide (GtCO2) annually (a significant level; in comparison, total global emissions in 2017 were 53.5 GtCO2e), with the largest reductions coming from dedicated biomass power generation with CCS. The report identified the immaturity of the technology, uncertainty over the availability of sustainable biomass supply and secure and permanent carbon dioxide storage, and negative public perceptions of CCS as important barriers, though it considered that the association of CCS with biomass, as a renewable energy technology, could possibly help overcome public resistance.
BECCS assumed a much more prominent role in the IPCC’s Fifth Assessment Report. Across the 116 scenarios reviewed that were consistent with limiting global warming to 2°C, 101 involved some form of negative emissions, either through BECCS or afforestation and reforestation.
In 2014, BECCS assumed a much more prominent role in the IPCC’s Fifth Assessment Report. Across the 116 scenarios reviewed that were consistent with limiting global warming to 2°C, 101 involved some form of negative emissions, either through BECCS or afforestation and reforestation. The average level of BECCS deployment by 2100 in these scenarios was 12.1 GtCO2/year (full range: 0–22 GtCO2/year).8 Every scenario aiming to limit global warming to 1.5°C included BECCS.9 The scenarios considered in the report required BECCS, in particular, to compensate for residual emissions from sectors where mitigation was more expensive, such as aviation or agriculture, or to return emissions to target levels after an overshoot resulting from a lack of near-term action. The synthesis report concluded: ‘Many models could not limit likely warming to below 2°C … if … bioenergy, CCS, and their combination (BECCS) are limited (high confidence).’10
However, these scenarios did not evaluate the on-the-ground feasibility of such removals; they merely demonstrated the necessity of CDR given the emissions profiles in the scenarios. Important factors limiting the extent of BECCS included uncertain land availability, the likely difficulty of ensuring a sustainable supply of biomass and storage capacity, and possible competition for biomass from other uses of bioenergy. The IPCC cautioned: ‘The use of BECCS faces large challenges in financing, and currently no such plants have been built and tested at scale.’11
Despite such caveats, the increasing attention paid to BECCS has continued into the IPCC’s Sixth Assessment cycle, including both the 2018 special report on Global Warming of 1.5°C (SR1.5)12 and the 2019 special report on Climate Change and Land (SRCCL),13 each of which contains critical appraisals of the feasibility, costs and benefits of extensive use of BECCS in meeting 1.5–2°C warming limitation targets. SR1.5 sets out four illustrative model pathways to limit warming to 1.5°C, three of which involve no or limited overshooting of cumulative emissions targets (see Figure 1). All four pathways include contributions from various means of CDR, mainly BECCS and afforestation and reforestation:
- P1 (focus on reducing energy demand): no contribution from BECCS.
- P2 (broad focus on sustainability): cumulative 151 GtCO2 captured by BECCS to 2100.
- P3 (middle-of-the-road scenario, largely following historical patterns): cumulative 414 GtCO2 captured by BECCS to 2100.
- P4 (resource- and energy-intensive overshoot scenario in which emissions reductions are mainly achieved through BECCS): cumulative 1,191 GtCO2 captured by BECCS to 2100.
Figure 1: Breakdown of contributions to global net CO2 emissions in four illustrative model pathways
— Source: IPCC (2018), Global Warming of 1.5°C, p. 14. Note: AFOLU = agriculture, forestry and other land use.
Figure 1: Breakdown of contributions to global net CO2 emissions in four illustrative model pathways
In all of these 1.5°C scenarios,14 generation of negative emissions is required to begin in the first half of the century; the urgency and scale of the requirement depend on the degree of emissions abatement elsewhere in the economy. Under the most intransigent scenario (P4), the total area of land required for bioenergy crops for BECCS is 7.2 million km2, more than double the area of India or equivalent to around half of the current extent of global croplands.15
The literature and models reviewed by SR1.5 exhibit huge variations in mitigation potential for BECCS, ranging from 1 GtCO2/year to 85 GtCO2/year by 2050. The report accepted, however, the more cautious assessment made in a recent systematic review of the literature on global negative emissions potentials, which concluded that the most likely scope for BECCS, taking into account other sustainability aims, was 0.5–5 GtCO2/year, at costs of US$100–200/tCO2.16
SR1.5 touched on the factors constraining the availability of BECCS feedstock and highlighted the associated demand for land and water:
Large-scale deployment of BECCS and/or AR [afforestation and reforestation] would have a far-reaching land and water footprint (high confidence). Whether this footprint would result in adverse impacts, for example on biodiversity or food production, depends on the existence and effectiveness of measures to conserve land carbon stocks, measures to limit agricultural expansion in order to protect natural ecosystems, and the potential to increase agricultural productivity (medium agreement).17
This theme was taken up in greater detail in SRCCL, which reached similar conclusions. It also noted that:
These impacts are context specific and depend on the scale of deployment, initial land use, land type, bioenergy feedstock, initial carbon stocks, climatic region and management regime, and other land-demanding response options can have a similar range of consequences (high confidence).18
Certainly, where feedstocks are sourced from high-carbon ecosystems (such as primary forests), this would result in large initial carbon losses and long payback periods, meaning that the protection of ecosystems would be a more optimal approach.19
SRCCL also clearly demonstrated that the risks from widespread BECCS deployment are closely linked to the overall sustainability of development trajectories. It considered various socioeconomic pathways, from sustainability-focused to resource-intensive, and the land-use implications of mitigation actions that would be compatible with limiting warming to 1.5°C under each pathway. At the more sustainable end (SSP1), with low populations, effective land-use regulation, food systems with low greenhouse gas emissions, and lower food losses and waste, the aggregate risks to food security, land quality and water supply in drylands only hit moderate levels when bioenergy or BECCS feedstocks occupy 1–4 million km2 of land, largely because changes in food demand free up land for biomass. At the other end of the spectrum – pathways associated with high populations, low income and slow rates of technological change (such as SSP3) – moderate risks emerge when bioenergy feedstocks occupy a far more modest 0.1–1 million km2.
Although other potential negative emissions technologies – such as direct air carbon capture and storage (DACCS) and enhanced weathering – are increasingly reviewed in the literature, and were considered in the AR6 special reports, they feature less frequently quantitatively in IAMs. Rather, BECCS has assumed almost a default role in many of these models because – as mentioned – its impacts on emissions are relatively straightforward to quantify at various carbon prices compared with those of other (even more nascent) negative emissions technologies:
Technologies other than BECCS and afforestation have yet to be comprehensively assessed in integrated assessment approaches. No proposed technology is close to deployment at scale, and regulatory frameworks are not established. This limits how they can be realistically implemented within IAMs.20
5 Hickman, L. (2016), ‘Timeline: How BECCS became climate change’s ‘saviour’ technology’, Carbon Brief, 13 April 2016, https://www.carbonbrief.org/beccs-the-story-of-climate-changes-saviour-technology.
6 IPCC (2007), Climate Change 2007: Mitigation of Climate Change. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Metz, B., Davidson, O. R., Bosch, P. R., Dave, R. and Meyer, L. A. (eds)], Cambridge and New York: Cambridge University Press, p. 211, https://www.ipcc.ch/site/assets/uploads/2018/03/ar4_wg3_full_report-1.pdf.
7 Ecofys (2011), Potential for Biomass and Carbon Dioxide Capture and Storage, Paris: IEA, http://www.eenews.net/assets/2011/08/04/document_cw_01.pdf.
8 Smith, P. and Porter, J. R. (2018), ‘Bioenergy in the IPCC assessments’, Global Change Biology Bioenergy, pp. 428–31, doi: 10.1111/gcbb.12514.
9 IPCC (2014), Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., Pichs-Madruga, R., Sokona, Y., Farahani, E., Kadner, S., Seyboth, K., Adler, A., Baum, I., Brunner, S., Eickemeier, P., Kriemann, B., Savolainen, J., Schlömer, S., von Stechow, C., Zwickel, T. and Minx, J. C. (eds)], Cambridge and New York: Cambridge University Press, https://www.ipcc.ch/report/ar5/wg3/. Also see Fuss, S. (2016), ‘The role of BECCS in climate change mitigation: potentials and limits’, presentation to IEA BECCS Specialist Meeting, London, 23 June 2016.
10 IPCC (2015), Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri, R. K. and Meyer, L. A. (eds)], Geneva: IPCC, p. 85, https://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_FINAL_full_wcover.pdf.
11 IPCC (2014), Climate Change 2014: Mitigation of Climate Change, p. 486.
12 IPCC (2018), Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., Zhai, P., Pörtner, H.-O., Roberts, D., Skea, J., Shukla, P. R., Pirani, A., Moufouma-Okia, W., Péan, C., Pidcock, R., Connors, S., Matthews, J. B. R., Chen, Y., Zhou, X., Gomis, M. I., Lonnoy, E., Maycock, T., Tignor, M. and Waterfield, T. (eds)], https://www.ipcc.ch/sr15/.
13 IPCC (2019), Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems [Shukla, P. R., Skea, J., Calvo Buendia, E., Masson-Delmotte, V., Pörtner, H.-O., Roberts, D. C., Zhai, P., Slade, R., Connors, S., van Diemen, R., Ferrat, M., Haughey, E., Luz, S., Neogi, S., Pathak, M., Petzold, J., Portugal Pereira, J., Vyas, P., Huntley, E., Kissick, K., Belkacemi, M. and Malley, J. (eds)], https://www.ipcc.ch/srccl/.
14 These pathways are something of an exception, as the majority of feasible 1.5°C and 2°C emissions pathways in IAMs are budget overshoot pathways with high discount rates.
15 IPCC (2018), Global Warming of 1.5°C, ‘Summary for Policymakers’, p. 14.
16 Fuss, S., Lamb, W. F., Callaghan, M. W., Hilaire, J., Creutzig, F., Amann, T., Beringer, T., de Oliveira Garcia, W., Hartmann, J., Khanna, T., Luderer, G., Nemet, G. F., Rogelj, J., Smith. P., Vicente, J. L. V., Wilcox, J., del Mar Zamora Dominguez, M. and Minx, J. C. (2018), ‘Negative emissions—Part 2: Costs, potentials and side effects’, Environmental Research Letters, 13(6), doi:10.1088/1748-9326/aabf9f.
17 IPCC (2018), Global Warming of 1.5°C, p. 180.
18 IPCC (2019), Climate Change and Land, ‘Summary for Policymakers’.
19 Ibid., Chapter 2.
20 IPCC (2018), Global Warming of 1.5°C, p. 158.