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

=== 5.4.1 Greenhouse gas emissions from food systems ===

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This chapter assesses the contributions of the entire food system to greenhouse gas (GHG) emissions. Food systems emissions include CO <sub>2</sub> and non-CO <sub>2</sub> gases, specifically those generated from: (i) crop and livestock activities within the farm gate (Table 5.4, category ‘Agriculture’); (ii) land use and land-use change dynamics associated with agriculture (Table 5.4, category ‘Land Use’); and (iii) food processing, retail and consumption patterns, including upstream and downstream processes such as manufacture of chemical fertilisers and fuel (Table 5.4, category ‘Beyond Farm Gate’). The first two categories comprise emissions reported by countries in the AFOLU (agriculture, forestry, and other land use) sectors of national GHG inventories; the latter comprises emissions reported in other sectors of the inventory, as appropriate. For instance, industrial processes, energy use, and food loss and waste.

The first two components (agriculture and land use) identified above are well quantified and supported by an ample body of literature (Smith et al. 2014 <sup>[[#fn:r680|680]]</sup> ). During the period 2007–2016, global agricultural non-CO <sub>2</sub> emissions from crop and livestock activities within the farm gate were 6.2 ± 1.4 GtCO <sub>2</sub> -eq yr <sup>–1</sup> during 2007–2016, with methane (142 ± 42 MtCH <sub>4</sub> yr <sup>-1</sup> , or 4.0 ± 1.2 GtCO <sub>2</sub> -eq yr <sup>-1</sup> ) contributing in CO <sub>2</sub> -eq about twice as much as nitrous oxide (8.3 ± 2.5 MtN <sub>2</sub> O yr <sup>-1</sup> , or 2.2 ± 0.7 GtCO <sub>2</sub> -eq yr <sup>–1</sup> ) to this total (Table 2.2 in Chapter 2). Emissions from land use associated with agriculture in some regions, such as from deforestation and peatland degradation (both processes involved in preparing land for agricultural use), added another 4.9 ± 2.5 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (Chapter 2) globally during the same period. These estimates are associated with uncertainties of about 30% (agriculture) and 50% (land use), as per IPCC AR5 (Smith et al. 2014 <sup>[[#fn:r681|681]]</sup> ).

Agriculture activities within the farm gate and associated land-use dynamics are therefore responsible for about 11.1 ± 2.9 GtCO <sub>2</sub> -eq yr <sup>-1</sup> , or some 20% of total anthropogenic emissions (Table 5.4), consistent with post-AR5 findings (for example, Tubiello et al. 2015). In terms of individual gases, the contributions of agriculture to total emissions by gas are significantly larger. For instance, over the period 2010–2016, methane gas emissions within the farm gate represented about half of the total CH <sub>4</sub> emitted by all sectors, while nitrous dioxide gas emissions within the farm gate represented about three-quarters of the total N <sub>2</sub> O emitted by all sectors (Tubiello 2019 <sup>[[#fn:r682|682]]</sup> ). In terms of carbon, CO <sub>2</sub> emissions from deforestation and peatland degradation linked to agriculture contributed about 10% of the CO <sub>2</sub> emitted by all sectors in 2017 (Le Quéré et al. 2018 <sup>[[#fn:r683|683]]</sup> ).

Food systems emissions beyond the farm gate, such as those upstream from manufacturing of fertilisers, or downstream such as food processing, transport and retail, and food consumption, generally add to emissions from agriculture and land use, but their estimation is very uncertain due to lack of sufficient studies. The IPCC AR5 (Fischedick et al. 2014 <sup>[[#fn:r684|684]]</sup> ) provided some information on these other food system components, noting that emissions beyond the farm gate in developed countries may equal those within the farm gate, and cited one study estimating world total food system emissions to be up to 30% of total anthropogenic emissions (Garnett 2011 <sup>[[#fn:r685|685]]</sup> ). More recently, Poore and Nemecek (2018) <sup>[[#fn:r686|686]]</sup> , by looking at a database of farms and using a combination of modelling approaches across relevant processes, estimated a total contribution of food systems around 26% of total anthropogenic emissions. Total emissions from food systems may account for 21–37% of total GHG emissions (medium confidence).

Based on the available literature, a break-down of individual contributions of food systems emissions is show in Table 5.4, between those from agriculture within the farm gate (10–14%) (high confidence); emissions from land use and land-use change dynamics such as deforestation and peatland degradation, which are associated with agriculture in many regions (5–14%) (high confidence); and those from food supply chain activities past the farm gate, such as storage, processing, transport, and retail (5–10%) (limited evidence, medium agreement). Note that the corresponding lower range of emissions past the farm gate, for example, 2.6 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (Table 5.4), is consistent with recent estimates made by Poore and Nemecek (2018). Contributions from food loss and waste are implicitly included in these estimates of total emissions from food systems (Section 5.5.2.5). They may account for 8–10% of total anthropogenic GHG emissions (low confidence) (FAO 2013b <sup>[[#fn:r687|687]]</sup> ).

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'''Table 5.4'''

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'''GHG emissions (GtCO2-eq yr–1) from the food system and their contribution (%) to total anthropogenic emissions. Mean of 2007–2016 period.'''
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Notes: Food system emissions are estimated from a) FAOSTAT (2018), b) US EPA (2012), c) Poore and Nemecek (2018) and d) Fischedick et al. (2014) (using square root of sum of squares of standard deviations when adding uncertainty ranges; see also Chapter 2); e) rounded to nearest fifth percentile due to assessed uncertainty in estimates. Percentage shares were computed by using a total emissions value for the period 2007–2016 of nearly 52 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (Chapter 2), using GWP values of the IPCC AR5 with no climate feedback (GWP-CH <sub>4</sub> =28; GWP-N <sub>2</sub> O=265).

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