Editing IPCC:AR6/WGIII/Chapter-12 (section)

==== 12.6.1.2 Mitigation Measures from a Cross-sectoral Perspective ====

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Three aspects of mitigation from a cross-sectoral perspective are considered, following [[#Barker--2007|Barker et al. (2007)]] :

• mitigation measures used in more than one sector;

'''•''' implications of mitigation measures for interaction and integration between sectors; and

• competition among sectors for scarce resources.

A number of mitigation measures find application in more than one sector. Renewable energy technologies such as solar and wind may be used for grid electricity supply, as embedded generation in the buildings sector and for energy supply in the agriculture sector ( [[#Shahsavari--2018|Shahsavari and Akbari 2018]] ) (Chapters 6, 7 and 8). Hydrogen and fuel cells, coupled with low-carbon energy technologies for producing the hydrogen, are being explored in transport, urban heat, industry and for balancing electricity supply ( [[#Dodds--2015|Dodds et al. 2015]] ; [[#Staffell--2019|Staffell et al. 2019]] ) (Chapters 6, 8 and 11). Electric vehicles are considered an option for balancing variable power ( [[#Kempton--2005|Kempton and Tomić 2005]] ; [[#Liu--2019|Liu and Zhong 2019]] ). Carbon capture and storage (CCS) and carbon capture and utilisation (CCU) have potential application in a number of industrial processes (cement, iron and steel, petroleum refining and pulp and paper) ( [[#Leeson--2017|Leeson et al. 2017]] ; [[#Garcia--2019|Garcia and Berghout 2019]] ) (Chapters 6 and 11) and the fossil fuel electricity sector (Chapter 6). When coupled with energy recovery from biomass, CCS can provide a carbon sink (BECCS) ( [[#12.5|Section 12.5]] ). On the demand side, energy efficiency options find application across the sectors (Chapters 6, 8, 9, 10, and 11), as do reducing demand for goods and services (Chapter 5) and improving material efficiency ( [[IPCC:Wg3:Chapter:Chapter-11#11.3.2|Section 11.3.2]] ).

A range of examples where mitigation measures result in cross-sectoral interactions and integration is identified. The mitigation potential of electric vehicles, including plug-in hybrids, is linked to the extent of decarbonisation of the electricity grid, as well as to the liquid fuel supply emissions profile ( [[#Lutsey--2015|Lutsey 2015]] ). Making buildings energy positive, where excess energy is used to charge vehicles, can increase the potential of electric and hybrid vehicles ( [[#Zhou--2019|Zhou et al. 2019]] ). Advanced process control and process optimisation in industry can reduce energy demand and material inputs ( [[IPCC:Wg3:Chapter:Chapter-11#11.3|Section 11.3]] ), which in turn can reduce emissions linked to resource extraction and manufacturing. Reductions in coal-fired power generation through replacement with renewables or nuclear power result in a reduction in coal mining and its associated emissions. Increased recycling results in a reduction in emissions from primary resource extraction. CCU can contribute to the transition to more renewable energy systems via power-to-X technologies, which enables the production of CO 2 -based fuels/e-fuels and chemicals using carbon dioxide and hydrogen ( [[#Breyer--2015|Breyer et al. 2015]] ; [[#Anwar--2020|Anwar et al. 2020]] ). Certain emissions reductions in the AFOLU sector are contingent on energy sector decarbonisation. Trees and green roofs planted to counter urban heat islands reduce the demand for energy for air conditioning and simultaneously sequester carbon ( [[#Kim--2018|Kim and Coseo 2018]] ; [[#Kuronuma--2018|Kuronuma et al. 2018]] ). Recycling of organic waste avoids methane generation if the waste would have been disposed of in landfill sites, can generate renewable energy if treated through anaerobic digestion, and can reduce requirements for synthetic fertiliser production if the nutrient value is recovered ( [[#Creutzig--2015|Creutzig et al. 2015]] ). Liquid transport biofuels link to the land, energy and transport sectors ( [[#12.5.2|Section 12.5.2]] .2).

Demand-side mitigation measures, discussed in Chapter 5, also have cross-sectoral implications which need to be taken into account when calculating mitigation potentials. Residential electrification has the potential to reduce emissions associated with lighting and heating, particularly in developing countries where these are currently met by fossil fuels and using inefficient technologies, but will increase demand for electricity (Chapters 5 and 8 and Sections 6.6.2.3 and 8.4.3.1). Many industrial processes can also be electrified in the move away from fossil reductants and direct energy carriers (Chapter 11). The impact of electrification on electricity sector emissions will depend on whether electricity generation is based on fossil fuels in the absence of CCS or low-carbon energy sources (Chapter 5).

At the same time, saving electricity in all sectors reduces the demand for electricity, thereby reducing mitigation potential of renewables and CCS. Demand-side flexibility measures and electrification of vehicle fleets are supportive of more intermittent renewable energy supply options (Sections 6.3.7, 6.4.3.1 and 10.3.4). Production of maize, wheat, rice and fresh produce requires lower energy inputs on a lifecycle basis than poultry, pork and ruminant-based meats ( [[#Clark--2017|Clark and Tilman 2017]] ) ( [[#12.4|Section 12.4]] ). It also requires less land area per kilocalorie or protein output ( [[#Clark--2017|Clark and Tilman 2017]] ; Poore and Nemecek 2018), so replacing meat with these products makes land available for sequestration, biodiversity or other societal needs. However, production of co-products of the meat industry, such as leather and wool, is reduced, resulting in a need for substitutes. Further discussion and examples of cross-sectoral implications of mitigation, with respect to cost and potentials, are presented in [[#12.2|Section 12.2]] . One final example on this topic included here is that of circular economy ( [[#_idTextAnchor014|Box 12.4]] ).

Finally, in terms of competition among sectors for scarce resources, this issue is often considered in the assessments of mitigation potentials linked to bioenergy and diets (vegetable vs animal food products), land use and water ( ''robust evidence'' , ''high agreement'' ) ( [[#12.5|Section 12.5]] and Cross-Working Group Box 3 in this Chapter). It is, however, also relevant elsewhere. Constraints have been identified in the supply of indium, tellurium, silver, lithium, nickel and platinum that are required for implementation of some specific renewable energy technologies ( [[#Watari--2018|Watari et al. 2018]] ; [[#Moreau--2019|Moreau et al. 2019]] ). Other studies have shown constraints in supply of cobalt, one of the key elements used in production of lithium-ion batteries, which has been assessed for mitigation potential in energy, transport and buildings sectors ( ''medium evidence'' , ''high agreement'' ) (Jaffe 2017; [[#Olivetti--2017|Olivetti et al. 2017]] ), although alternatives to cobalt are being developed ( [[#Olivetti--2017|Olivetti et al. 2017]] ; [[#Watari--2018|Watari et al. 2018]] ).

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