Protocol for a Tier 2 approach to generate context-specific enteric methane emission factors (EF) for cattle production systems using IPCC method.

This protocol aims to provide a guide for the collection of data and calculation of local enteric methane (CH4) emission factors (EF = CH4 kg/head/year) for cattle production systems in low- and middle-income countries (LMICs) based on the Intergovernmental Panel on Climate Change (IPCC) Tier 2 method (IPCC, 2006, 2019) and necessary additions to increase the accuracy of the Tier 2 EF. Tier 2 enteric CH4 estimations are essential for improved accuracy in reporting national greenhouse gas (GHG) inventories and developing locally suitable mitigation strategies in line with the Paris Climate Change Agreement (https://unfccc.int/most-requested/key-aspects-of-the-paris- agreement). The use of the Tier 2 method is more accurate than the Tier 1 method currently used by most LMICs. It incorporates local animal activity data and diet characteristics, in contrast to the Tier 1 method which uses activity data averaged at a continental level. The approach described in this protocol takes into account seasonal differences in feed availability, feed quality, and related variations in animal performance since there is limited inclusion of seasonality in Tier 2 IPCC 2006 and 2019 guidelines. The energy requirement calculations in this protocol are based on net energy equations described in the revised IPCC method of 2019 (IPCC, 2019), with the initial method described in the IPCC (2006). Some examples in published literature where the IPCC Tier 2 method has been used include Du Toit, Meissner, and Van Niekerk (2013), (Du Toit et al., 2013); Kouazounde et al. (2015), Wilkes, Wassie, Tadesse, et al. (2020), Wilkes, Wassie, Fraval, and van Dijk (2020), Wilkes, Pica-Ciamarra, and Opio (2020), Ndao, Moulin, Traoré, Diop, and Bocquier (2019) and Gurmu et al. (2024).