Editing IPCC:AR6/SRCCL/Chapter-6 (section)

== CCB7 Bioenergy and bioenergy with carbon capture and storage (BECCS) in mitigation scenarios ==

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Katherine Calvin (The United States of America), Almut Arneth (Germany), Luis Barioni (Brazil), Francesco Cherubini (Norway/Italy), Annette Cowie (Australia), Joanna House (United Kingdom), Francis X. Johnson (Sweden), Alexander Popp (Germany), Joana Portugal Pereira (Portugal/United Kingdom), Mark Rounsevell (United Kingdom), Raphael Slade (United Kingdom), Pete Smith (United Kingdom)

'''Bioenergy and BECCS potential. ''' Using biomass to produce heat, electricity and transport fuels (bioenergy) instead of coal, oil, and natural gas can reduce GHG emissions. Combining biomass conversion technologies with systems that capture CO2 and inject it into geological formations, BECCS can deliver net negative emissions. The net climate effects of bioenergy and BECCS depend on the magnitude of bioenergy supply chain emissions and land/climate interactions, described further below.

Biomass in 2013 contributed about 60 EJ (10%) to global primary energy4 (WBA 2016 <sup>[[#fn:r1243|1243]]</sup> ). In 2011, the IPCC Special Report on Renewable Energy Sources concluded that biomass supply for energy could reach 100–300 EJ yr <sup>–1</sup> by 2050 with the caveat that the technical potential5 cannot be determined precisely while societal preferences are unclear; that deployment depends on ‘factors that are inherently uncertain’; and that biomass use could evolve in a ‘sustainable’ or ‘unsustainable’ way, depending on the governance context (IPCC 2012 <sup>[[#fn:r152|152]]</sup> ). The IPCC WGIII AR5 report noted, in addition, that high deployment levels would require extensive use of technologies able to convert lignocellulosic biomass such as forest wood, agricultural residues, and lignocellulosic crops. The IPCC Special Report on Global Warming of 1.5°C (SR15) noted that high levels of bioenergy deployment may result in adverse side effects for food security, ecosystems, biodiversity, water use, and nutrients (de Coninck et al. 2018).

Although estimates of potential are uncertain, there is high confidence that the most important factors determining future biomass supply are land availability and land productivity. These factors are, in turn, determined by competing uses of land and a myriad of environmental and economic considerations (Dornburg et al. 2010 <sup>[[#fn:r153|153]]</sup> ; Batidzirai et al. 2012 <sup>[[#fn:r154|154]]</sup> ; Erb et al. 2012 <sup>[[#fn:r155|155]]</sup> ; Slade 2014, Searle and Malins 2014). Overlaying estimates of technical potential with such considerations invariably results in a smaller estimate. Recent studies that have attempted to do this estimate that 50–244 EJ biomass could be produced on 0.1–13 Mkm <sup>2</sup> (Fuss et al. 2018 <sup>[[#fn:r156|156]]</sup> ; Schueler et al. 2016 <sup>[[#fn:r157|157]]</sup> ; Searle and Malins 2014 <sup>[[#fn:r158|158]]</sup> ; IPCC 2018 <sup>[[#fn:r159|159]]</sup> ; Wu et al. 2019 <sup>[[#fn:r160|160]]</sup> ; Heck et al. 2018 <sup>[[#fn:r161|161]]</sup> ; de Coninck et al. 2018 <sup>[[#fn:r162|162]]</sup> ). While preferences concerning economic, social and environmental objectives vary geographically and over time, studies commonly estimate ‘sustainable’ potentials by introducing restrictions intended to protect environmental values and avoid negative effects on poor and vulnerable segments in societies.

Estimates of global geological CO2 storage capacity are large – ranging from 1680 GtCO <sub>2</sub> to 24,000 GtCO <sub>2</sub> (McCollum et al. 2014 <sup>[[#fn:r163|163]]</sup> ) – however, the potential of BECCS may be significantly constrained by socio-political and technical and geographical considerations, including limits to knowledge and experience (Chapters 6 and 7).

'''Bioenergy and BECCS use in mitigation scenarios'''

Most mitigation scenarios include substantial deployment of bioenergy technologies (Clarke et al. 2014 <sup>[[#fn:r164|164]]</sup> ; Fuss et al. 2014 <sup>[[#fn:r165|165]]</sup> ; IPCC 2018 <sup>[[#fn:r166|166]]</sup> ). Across all scenarios, the amount of bioenergy and BECCS ranges from 0 EJ yr <sup>–1</sup> to 561 EJ yr <sup>–1</sup> in 2100 (Figure 1 in this box, left panel). Notably, all 1.5°C pathways include bioenergy, requiring as much as 7 Mkm2 to be dedicated to the production of energy crops in 2050 (Rogelj et al. 2018a <sup>[[#fn:r167|167]]</sup> ). If BECCS is excluded as a mitigation option, studies indicate that more biomass may be required in order to substitute for a greater proportion of fossil fuels (Muratori et al. 2016 <sup>[[#fn:r168|168]]</sup> ; Rose et al. 2014 <sup>[[#fn:r169|169]]</sup> ).

Different Integrated Assessment Models (IAMs) use alternative approaches to land allocation when determining where and how much biomass is used, with some relying on economic approaches and some relying on rule-based approaches (Popp et al. 2014 <sup>[[#fn:r170|170]]</sup> ). Despite these differences, a consistent finding across models is that increasing biomass supply to the extent necessary to support deep decarbonisation is likely to involve substantial land-use change (Popp et al. 2017 <sup>[[#fn:r171|171]]</sup> ) (Cross-Chapter Box 9 in this chapter). In model runs, bioenergy deployment and the consequent demand for biomass and land, is influenced by assumptions around the price of bioenergy, the yield of bioenergy crops, the cost of production (including the costs of fertiliser and irrigation if used), the demand for land for other uses, and the inclusion of policies (e.g., subsidies, taxes, constraints) that may alter land-use or bioenergy demand. In general, higher carbon prices result in greater bioenergy deployment (Cross-Chapter Box 7, Figure 1, right panel) and a larger percentage of BECCS. Other factors can also strongly influence bioenergy use, including the cost and availability of fossil fuels (Calvin et al. 2016a), socio-economics (Popp et al. 2017 <sup>[[#fn:r172|172]]</sup> ), and policy (Calvin et al. 2014 <sup>[[#fn:r173|173]]</sup> ; Reilly et al. 2012 <sup>[[#fn:r174|174]]</sup> ).

'''Co-benefits, adverse side effect, and risks associated with bioenergy'''

The production and use of biomass for bioenergy can have co-benefits, adverse side effects, and risks for land degradation, food insecurity, GHG emissions, and other environmental goals. 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 (Qin et al. 2016 <sup>[[#fn:r175|175]]</sup> ; Del Grosso et al. 2014 <sup>[[#fn:r176|176]]</sup> ; Alexander et al. 2015 <sup>[[#fn:r177|177]]</sup> ; Popp et al. 2017 <sup>[[#fn:r178|178]]</sup> ; Davis et al. 2013 <sup>[[#fn:r179|179]]</sup> ; Mello et al. 2014 <sup>[[#fn:r180|180]]</sup> ; Hudiburg et al. 2015 <sup>[[#fn:r181|181]]</sup> ; Carvalho et al. 2016 <sup>[[#fn:r182|182]]</sup> ; Silva-Olaya et al. 2017 <sup>[[#fn:r183|183]]</sup> ; Whitaker et al. 2018 <sup>[[#fn:r184|184]]</sup> ; Robledo-Abad et al. 2017 <sup>[[#fn:r185|185]]</sup> ; Jans et al. 2018 <sup>[[#fn:r186|186]]</sup> ).

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'''Cross-Chapter Box 7 Figure 1'''

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'''Global bioenergy consumption in IAM scenarios. Data is from an update of the Integrated Assessment Modelling Consortium (IAMC) Scenario Explorer developed for the SR15 (Huppmann et al. 2018; Rogelj et al. 2018a). The left panel A. shows bioenergy deployment over time for the entire scenario database (grey areas) and the four illustrative pathways from SR15 […]'''
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[[File:b5810f42087d810659d868eb10128bf7 Cross-Chapter-Box-7-Figure-1-1024x513.jpg]]

Global bioenergy consumption in IAM scenarios. Data is from an update of the Integrated Assessment Modelling Consortium (IAMC) Scenario Explorer developed for the SR15 (Huppmann et al. 2018 <sup>[[#fn:r1244|1244]]</sup> ; Rogelj et al. 2018a <sup>[[#fn:r1245|1245]]</sup> ). The left panel A. shows bioenergy deployment over time for the entire scenario database (grey areas) and the four illustrative pathways from SR15 (Rogelj et al. 2018a <sup>[[#fn:r1246|1246]]</sup> ). The right panel B. shows global land area for energy crops in 2100 versus total global bioenergy consumption in 2100; colours indicate the carbon price in 2100 (in 2010 USD per tCO <sub>2</sub> ). Note that this figure includes 409 scenarios, many of which exceed 1.5°C.

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Synergistic outcomes with bioenergy are possible, for example, strategic integration of perennial bioenergy crops with conventional crops can provide multiple production and environmental benefits, including management of dryland salinity, enhanced biocontrol and biodiversity, and reduced eutrophication (Davis et al. 2013 <sup>[[#fn:r190|190]]</sup> ; Larsen et al. 2017 <sup>[[#fn:r191|191]]</sup> ; Cacho et al. 2018 <sup>[[#fn:r192|192]]</sup> ; Odgaard et al. 2019 <sup>[[#fn:r193|193]]</sup> ). Additionally, planting perennial bioenergy crops on low-carbon soil could enhance soil carbon sequestration (Bárcena et al. 2014 <sup>[[#fn:r194|194]]</sup> ; Schröder et al. 2018 <sup>[[#fn:r195|195]]</sup> ; Walter et al. 2015 <sup>[[#fn:r196|196]]</sup> ; Robertson et al. 2017a <sup>[[#fn:r197|197]]</sup> ; Rowe et al. 2016 <sup>[[#fn:r198|198]]</sup> ; Chadwick et al. 2014 <sup>[[#fn:r199|199]]</sup> ; Immerzeel et al. 2014 <sup>[[#fn:r200|200]]</sup> ; Del Grosso et al. 2014; Mello et al. 2014 <sup>[[#fn:r201|201]]</sup> ; Whitaker et al. 2018 <sup>[[#fn:r202|202]]</sup> ). However, large-scale expansion of bioenergy may also result in increased competition for land (DeCicco 2013 <sup>[[#fn:r203|203]]</sup> ; Humpenöder et al. 2018 <sup>[[#fn:r204|204]]</sup> ; Bonsch et al. 2016 <sup>[[#fn:r205|205]]</sup> ; Harris et al. 2015 <sup>[[#fn:r206|206]]</sup> ; Richards et al. 2017 <sup>[[#fn:r207|207]]</sup> ; Ahlgren et al. 2017 <sup>[[#fn:r208|208]]</sup> ; Bárcena et al. 2014 <sup>[[#fn:r209|209]]</sup> ), increased GHG emissions from land-use change and land management, loss in biodiversity, and nutrient leakage (Harris et al. 2018 <sup>[[#fn:r210|210]]</sup> ; Harper et al. 2018 <sup>[[#fn:r211|211]]</sup> ; Popp et al. 2011b <sup>[[#fn:r212|212]]</sup> ; Wiloso et al. 2016 <sup>[[#fn:r213|213]]</sup> ; Behrman et al. 2015 <sup>[[#fn:r214|214]]</sup> ; Valdez et al. 2017 <sup>[[#fn:r215|215]]</sup> ; Hof et al. 2018). If biomass crops are planted on land with a high carbon stock, the carbon loss due to land conversion may take decades to over a century to be compensated by either fossil fuel substitution or CCS (Harper et al. 2018 <sup>[[#fn:r216|216]]</sup> ). Competition for land may be experienced locally or regionally and is one of the determinants of food prices, food security (Popp et al. 2014 <sup>[[#fn:r217|217]]</sup> ; Bailey 2013 <sup>[[#fn:r218|218]]</sup> ; Pahl-Wostl et al. 2018 <sup>[[#fn:r219|219]]</sup> ; Rulli et al. 2016 <sup>[[#fn:r220|220]]</sup> ; Yamagata et al. 2018 <sup>[[#fn:r221|221]]</sup> ; Franz et al. 2017 <sup>[[#fn:r222|222]]</sup> ; Kline et al. 2017 <sup>[[#fn:r223|223]]</sup> ; Schröder et al. 2018 <sup>[[#fn:r224|224]]</sup> ) and water availability (Rulli et al. 2016 <sup>[[#fn:r225|225]]</sup> ; Bonsch et al. 2015 <sup>[[#fn:r226|226]]</sup> ; Pahl-Wostl et al. 2018 <sup>[[#fn:r227|227]]</sup> ; Bailey 2013 <sup>[[#fn:r228|228]]</sup> ; Chang et al. 2016 <sup>[[#fn:r229|229]]</sup> ; Bárcena et al. 2014 <sup>[[#fn:r230|230]]</sup> ).

Experience in countries at quite different levels of economic development (Brazil, Malawi and Sweden) has shown that persistent efforts over several decades to combine improved technical standards and management approaches with strong governance and coherent policies, can facilitate long-term investment in more sustainable production and sourcing of liquid biofuels (Johnson and Silveira 2014 <sup>[[#fn:r231|231]]</sup> ). For woody biomass, combining effective governance with active forest management over long time periods can enhance substitution- sequestration co-benefits, such as in Sweden where bioenergy has tripled during the last 40 years (currently providing about 25% of total energy supply) while forest carbon stocks have continued to grow (Lundmark et al. 2014 <sup>[[#fn:r232|232]]</sup> ). A variety of approaches are available at landscape level and in national and regional policies to better reconcile food security, bioenergy and ecosystem services, although more empirical evidence is needed (Mudombi et al. 2018 <sup>[[#fn:r233|233]]</sup> ; Manning et al. 2015 <sup>[[#fn:r234|234]]</sup> ; Kline et al. 2017 <sup>[[#fn:r235|235]]</sup> ; Maltsoglou et al. 2014 <sup>[[#fn:r236|236]]</sup> ; Lamers et al. 2016 <sup>[[#fn:r237|237]]</sup> ).

Thus, while there is high confidence that the technical potential for bioenergy and BECCS is large, there is also very high confidence that this potential is reduced when environmental, social and economic constraints are considered. The effects of bioenergy production on land degradation, water scarcity, biodiversity loss, and food insecurity are scale and context specific (high confidence). Large areas of monoculture bioenergy crops that displace other land uses can exacerbate these challenges, while integration into sustainably managed agricultural landscapes can ameliorate them (medium confidence).

'''Inventory reporting for BECCS and bioenergy'''

One of the complications in assessing the total GHG flux associated with bioenergy under United Nations Framework Convention on Climate Change (UNFCCC) reporting protocols is that fluxes from different aspects of bioenergy lifecycle are reported in different sectors and are not linked. In the energy sector, bioenergy is treated as carbon neutral at the point of biomass combustion because all change in land carbon stocks due to biomass harvest or land-use change related to bioenergy are reported under agriculture, forestry and other land-use (AFOLU) sector. Use of fertilisers is captured in the agriculture sector, while fluxes related to transport/ conversion and removals due to CCS are reported in the energy sector. IAMs follow a similar reporting convention. Thus, the whole lifecycle GHG effects of bioenergy systems are not readily observed in national GHG inventories or modelled emissions estimates (see also IPCC 2006; SR15 Chapter 2 Technical Annex; Chapter 2).

'''Bioenergy in this report'''

Bioenergy and BECCS are discussed throughout this special report. Chapter 1 provides an introduction to bioenergy and BECCS and its links to land and climate. Chapter 2 discusses mitigation potential, land requirements and biophysical climate implications. Chapter 4 includes a discussion of the threats and opportunities with respect to land degradation. Chapter 5 discusses linkages between bioenergy and BECCS and food security. Chapter 6 synthesises the co-benefits and adverse side effects for mitigation, adaptation, desertification, land degradation, and food security, as well as barriers to implementation (e.g., cost, technological readiness, etc.). Chapter 7 includes a discussion of risk, policy, governance, and decision-making with respect to bioenergy and BECCS.

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