Improved region-specific emission factors for enteric methane emissions from cattle in smallholder mixed crop: livestock systems of Nandi County, Kenya

Abstract

Abstract. National greenhouse-gas (GHG) inventories in most developing countries, and in countries in Sub-Saharan Africa in particular, use default (Tier I) GHG emission factors (EFs) provided by the Intergovernmental Panel on Climate Change (IPCC) to estimate enteric methane (CH 4 ) emissions from livestock. Because these EFs are based on data primarily from developed countries, there is a high degree of uncertainty associated with CH 4 emission estimates from African livestock systems. Accurate Tier II GHG emission reporting from developing countries becomes particularly important following the Paris Climate agreement made at COP21, which encourages countries to mitigate GHG emissions from agricultural sources. In light of this, the present study provides improved enteric CH 4 emission estimates for cattle in Nandi County, Western Kenya, representing a common livestock production system found in East Africa. Using the data from measurements of liveweight and liveweight change, milk production and locomotion collected from 1143 cattle in 127 households across 36 villages over three major agro-ecological zones covering a full year, we estimated total metabolic energy requirements. From this and assessments of digestibility from seasonally available feeds, we estimated feed intake and used this to calculate daily CH 4 production by season, and, subsequently, created new EFs. Mean EFs were 50.6, 45.5, 28.5, 33.2 and 29.0 kg CH 4 /head.year for females (>2 years), males (>2 years), heifers (1-2 years), young males (1-2 years) and calves (<1 year) respectively, and were lower than the IPCC Tier I estimates for unspecified African adult cattle, but higher for calves and young males. Thus, using IPCC Tier 1 EFs may overestimate current enteric CH 4 emissions in some African livestock systems.

Improving Assessments of the Three Pillars of Climate Smart Agriculture: Current Achievements and Ideas for the Future

“…The latter is still far away though, but the idea is that mitigation successes can from now on not only be identified but also reliably be quantified. Recent work tries to improve on the generic IPCC emission factors as most were developed on estimates derived for systems in developed countries, which are likely not transferable to low and middle income countries given significant differences in management intensity, climates, soils, or even often animal breeds (e.g., Pelster et al, 2017;Goopy et al, 2018;Ndung'u et al, 2018;Richards et al, 2018;Zhu et al, 2018Zhu et al, , 2020. Currently, individual agricultural practices and technologies need to be similarly assessed in terms of meeting simultaneously the demands of pillars 1 and 2.…”

“…A key aspect of many of the tools is the adherence to the FAO GHG emission factors with limited ability to update these numbers or to include other GHG emission model formulations. While this is logical from a modeling perspective, such consistency in analyses does mean that most assessment frameworks use emission factors that are based on estimates derived for systems in developed countries under different climates with different breeds and overall completely different production systems (e.g., Goopy et al, 2018;Ndung'u et al, 2018;Richards et al, 2018). As a consequence, this can lead to substantial over/under-estimation of GHG emissions and of GHG emission intensities (see example 2017A standardized household survey approach aiming to quantify the three pillars of CSA for a given system.…”

“…As stated in the section discussing Table 1, most assessment tools (logically) adhere to the FAO GHG emission factors (IPCC, 2019). New work aims on improving these emission factors by specifically considering the situation in LMIC (e.g., Ndung'u et al, 2018;Richards et al, 2018;Zhu et al, 2018). Additionally, the majority of assessments are short term focused, and two lines of research are followed to deal with both limitations of the current assessments: one is empirical work focusing on measuring GHG emissions in the field, and thereby deriving empirically well-grounded GHG emission factors for the most dominant livestock production systems, and the other one is through biogeochemical process-based modeling approaches aiming at simulating biosphere-atmosphere exchange of GHGs while accounting for differences in management, soil properties, vegetation (crops) FIGURE 2 | The three pillars of CSA, and key advances identified in this manuscript needed to improve current assessment frameworks.…”

“…New empirical work includes the recent development of localized GHG emissions data from livestock, manure management as well as a variety of land cover types found in smallholder agricultural settings (Pelster et al, 2016(Pelster et al, , 2017Goopy et al, 2018;Ndung'u et al, 2018;Wanyama et al, 2018a,b;Zhu et al, 2018Zhu et al, , 2020Wachiye et al, 2020). This essential baseline data was collected following standardized protocols which can thus be applied to similar systems as well as to production systems that have not yet covered (Ndung'u et al, 2018). Similarly, a standardized approach will allow for tracking changes in GHG emissions (i.e., mitigation and to a certain degree also short-term adaptation/resilience to stresses) in the future.…”

Severe below-maintenance feed intake increases methane yield from enteric fermentation in cattle

“…However, a significant limitation to the utility of these equations is that measurements have been conducted only on animals fed for production (i.e. at maintenance and above), whereas it has been recently demonstrated that cattle regularly experience episodes of significant seasonal weight loss in African smallholder systems (10,11) .…”