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

=== 5.4.4 Greenhouse gas emissions from aquaculture ===

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Emissions from aquaculture and fisheries may represent some 10% of total agriculture emissions, or about 0.58 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (Barange et al. 2018 <sup>[[#fn:r711|711]]</sup> ), with two-thirds being non-CO <sub>2</sub> emissions from aquaculture (Hu et al. 2013 <sup>[[#fn:r712|712]]</sup> ; Yang et al. 2015 <sup>[[#fn:r713|713]]</sup> ) and the rest due to fuel use in fishing vessels. They were not included in Table 5.4 under agriculture emissions, as these estimates are not included in national GHG inventories and global numbers are small as well as uncertain.

Methodologies to measure aquaculture emissions are still being developed (Vasanth et al. 2016 <sup>[[#fn:r714|714]]</sup> ). N <sub>2</sub> O emissions from aquaculture are partly linked to fertiliser use for feed as well as aquatic plant growth, and depend on the temperature of water as well as on fish production (Paudel et al. 2015 <sup>[[#fn:r715|715]]</sup> ). Hu et al. (2012) <sup>[[#fn:r716|716]]</sup> estimated the global N <sub>2</sub> O emissions from aquaculture in 2009 to be 0.028 GtCO <sub>2</sub> -eq yr <sup>-1</sup> , but could increase to 0.114 GtCO <sub>2</sub> -eq yr <sup>–1</sup> (that is 5.72% of anthropogenic N <sub>2</sub> O–N emissions) by 2030 for an estimated 7.10% annual growth rate of the aquaculture industry. Numbers estimated by Williams and Crutzen (2010) <sup>[[#fn:r717|717]]</sup> were around 0.036 GtCO <sub>2</sub> -eq yr <sup>-1</sup> , and suggested that this may rise to more than 0.179 GtCO <sub>2</sub> -eq yr <sup>–1</sup> within 20 years for an estimated annual growth of 8.7%. Barange et al. (2018) <sup>[[#fn:r718|718]]</sup> assessed the contribution of aquaculture to climate change as 0.38 GtCO <sub>2</sub> -eq yr <sup>–1</sup> in 2010, around 7% of those from agriculture.

CO <sub>2</sub> emissions coming from the processing and transport of feed for fish raised in aquaculture, and also the emissions associated with the manufacturing of floating cultivation devices (e.g., rafts or floating fish-farms), connecting or mooring devices, artificial fishing banks or reefs, and feeding devices (as well as their energy consumption) may be considered within the emissions from the food system. Indeed, most of the GHG emissions from aquaculture are associated with the production of raw feed materials and secondarily, with the transport of raw materials to mills and finished feed to farms (Barange et al. 2018 <sup>[[#fn:r719|719]]</sup> ).

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