Editing IPCC:AR6/SRCCL/Chapter-5 (section)

==== 5.5.2.3 Uncertainties in demand-side mitigation potential ====

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Both reducing ruminant meat consumption and increasing its efficiency are often identified as the main options to reduce GHG emissions (GHGE) and to lessen pressure on land (Westhoek et al. 2014) (see Section 5.6 for synergies and trade-offs with health and Section 5.7 for discussion of Just Transitions). However, analysing ruminant meat production is highly complex because of the extreme heterogeneity of production systems and due to the numerous products and services associated with ruminants (Gerber et al. 2015 <sup>[[#fn:r893|893]]</sup> ). See Supplementary Material Section SM5.5 for further discussion of uncertainties in estimates of livestock mitigation technical potential. Further, current market mechanisms are regarded as insufficient to decrease consumption or increase efficiency, and governmental intervention is often suggested to encourage mitigation in both the supply-side and demand-side of the food system (Section 5.7) (Wirsenius et al. 2011 <sup>[[#fn:r894|894]]</sup> ; Henderson et al. 2018 <sup>[[#fn:r895|895]]</sup> ).

Minimising GHG emissions through mathematical programming with near-minimal acceptability constraints can be understood as a reference or technical potential for mitigation through diet shifts. In this context (Macdiarmid et al. 2012 <sup>[[#fn:r896|896]]</sup> ) found up to 36% reduction in emissions in UK with similar diet costs applying fixed lifecycle analyses (LCA) carbon footprints (i.e., no rebound effects considered). Westhoek et al. (2014) <sup>[[#fn:r897|897]]</sup> found 25–40% in emissions by halving meat, dairy and egg intake in the EU, applying standard IPCC fixed emission intensity factors. Uncertainty about the consequences of on-the-ground implementation of policies towards low ruminant meat consumption in the food system and their externalities remain noteworthy.

Often, all emissions are allocated only to human edible meat and the boundaries are set only within the farm gate (Henderson et al. 2018 <sup>[[#fn:r898|898]]</sup> ; Gerber et al. 2013 <sup>[[#fn:r899|899]]</sup> ). However, less than 50% of slaughtered cattle weight is human edible meat, and 1–10% of the mass is lost or incinerated, depending on specified risk materials legislation. The remaining mass provide inputs to multiple industries, for example clothing, furniture, vehicle coating materials, biofuel, gelatine, soap, cosmetics, chemical and pharmaceutical industrial supplies, pet feed ingredients and fertilisers (Marti et al. 2011 <sup>[[#fn:r900|900]]</sup> ; Mogensen et al. 2016 <sup>[[#fn:r901|901]]</sup> ; Sousa et al. 2017 <sup>[[#fn:r902|902]]</sup> ). This makes ruminant meat production one of the most complex problems for LCA in the food system (Place and Mitloehner 2012 <sup>[[#fn:r903|903]]</sup> ; de Boer et al. 2011 <sup>[[#fn:r904|904]]</sup> ). There are only a few examples taking into account slaughter by-products (Mogensen et al. 2016 <sup>[[#fn:r905|905]]</sup> ).

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