Editing IPCC:AR6/SR15/Chapter-4 (section)

==== 4.3.1.2 Bioenergy and biofuels ====

<div id="section-4-3-1-2-block-1"></div>

Bioenergy is renewable energy from biomass. Biofuel is biomass-based energy used in transport. Chapter 2 suggests that pathways limiting warming to 1.5°C would enable supply of 67–310 (median 150) EJ yr <sup>−1</sup> (see Table 2.8) from biomass. Most scenarios find that bioenergy is combined with carbon dioxide capture and storage (CCS, BECCS) if it is available but also find robust deployment of bioenergy independent of the availability of CCS (see Chapter 2, Section 2.3.4.2 and Section 4.3.7 for a discussion of BECCS). Detailed assessments indicate that deployment is similar for pathways limiting global warming to below 2°C (Chum et al., 2011; P. Smith et al., 2014; Creutzig et al., 2015b) <sup>[[#fn:r108|108]]</sup> . There is however ''high agreement'' that the sustainable bioenergy potential in 2050 would be restricted to around 100 EJ yr <sup>−1</sup> (Slade et al., 2014; Creutzig et al., 2015b) <sup>[[#fn:r109|109]]</sup> . Sustainable deployment at such or higher levels envisioned by 1.5°C-consistent pathways may put significant pressure on available land, food production and prices (Popp et al., 2014b; Persson, 2015; Kline et al., 2017; Searchinger et al., 2017) <sup>[[#fn:r110|110]]</sup> , preservation of ecosystems and biodiversity (Creutzig et al., 2015b; Holland et al., 2015; Santangeli et al., 2016) <sup>[[#fn:r111|111]]</sup> , and potential water and nutrient constraints (Gerbens-Leenes et al., 2009; Gheewala et al., 2011; Bows and Smith, 2012; Smith and Torn, 2013; Bonsch et al., 2016; Lampert et al., 2016; Mouratiadou et al., 2016; Smith et al., 2016b; Wei et al., 2016; Mathioudakis et al., 2017) <sup>[[#fn:r112|112]]</sup> ; but there is still ''low agreement'' on these interactions (Robledo-Abad et al., 2017) <sup>[[#fn:r113|113]]</sup> . Some of the disagreement on the sustainable capacity for bioenergy stems from global versus local assessments. Global assessments may mask local dynamics that exacerbate negative impacts and shortages while at the same time niche contexts for deployment may avoid trade-offs and exploit co-benefits more effectively. In some regions of the world (e.g., the case of Brazilian ethanol, see Box 4.7, where land may be less of a constraint, the use of bioenergy is mature and the industry is well developed), land transitions could be balanced with food production and biodiversity to enable a global impact on CO <sub>2</sub> emissions (Jaiswal et al., 2017) <sup>[[#fn:r114|114]]</sup> .

The carbon intensity of bioenergy, key for both bioenergy as an emission-neutral energy option and BECCS as a CDR measure, is still a matter of debate (Buchholz et al., 2016; Liu et al., 2018) <sup>[[#fn:r115|115]]</sup> and depends on management (Pyörälä et al., 2014; Torssonen et al., 2016; Baul et al., 2017; Kilpeläinen et al., 2017) <sup>[[#fn:r116|116]]</sup> ; direct and indirect land-use change emissions (Plevin et al., 2010; Schulze et al., 2012; Harris et al., 2015; Repo et al., 2015; DeCicco et al., 2016; Qin et al., 2016) <sup>[[#fn:r117|117]]</sup> <sup>[[#fn:2|2]]</sup> ; the feedstock considered; and time frame (Zanchi et al., 2012; Daioglou et al., 2017; Booth, 2018; Sterman et al., 2018) <sup>[[#fn:r118|118]]</sup> , as well as the availability of coordinated policies and management to minimize negative side effects and trade-offs, particularly those around food security (Stevanović et al., 2017) <sup>[[#fn:r119|119]]</sup> and livelihood and equity considerations (Creutzig et al., 2013; Calvin et al., 2014) <sup>[[#fn:r120|120]]</sup> .

Biofuels are a part of the transport sector in some cities and countries, and may be deployed as a mitigation option for aviation, shipping and freight transport (see Section 4.3.3.5) as well as industrial decarbonization (IEA, 2017g) <sup>[[#fn:r121|121]]</sup> (Section 4.3.4), though only Brazil has mainstreamed ethanol as a substantial, commercial option. Lower emissions and reduced urban air pollution have been achieved there by use of ethanol and biodiesel as fuels (Hill et al., 2006; Salvo et al., 2017) <sup>[[#fn:r122|122]]</sup> (see Box 4.7).

<div id="section-4-3-1-3"></div>

<span id="nuclear-energy"></span>