CH4 and N2O Emissions From Cattle Excreta: A Review of Main Drivers and Mitigation Strategies in Grazing Systems

Abstract

Cattle production systems are an important source of greenhouse gases (GHG) emitted to the atmosphere. Animal manure and managed soils are the most important sources of emissions from livestock after enteric methane. It is estimated that the N2O and CH4 produced in grasslands and manure management systems can contribute up to 25% of the emissions generated at the farm level, and therefore it is important to identify strategies to reduce the fluxes of these gases, especially in grazing systems where mitigation strategies have received less attention. This review describes the main factors that affect the emission of GHG from manure in bovine systems and the main strategies for their mitigation with emphasis on grazing production systems. The emissions of N2O and CH4 are highly variable and depend on multiple factors, which makes it difficult to use strategies that mitigate both gases simultaneously. We found that strategies such as the optimization of the diet, the implementation of silvopastoral systems and other practices with the capacity to improve soil quality and cover, and the use of nitrogen fixing plants are among the practices with more potential to reduce emissions from manure and at the same time contribute to increase carbon capture and improve food production. These strategies can be implemented to reduce the emissions of both gases and, depending on the method used and the production system, the reductions can reach up to 50% of CH4 or N2O emissions from manure according to different studies. However, many research gaps should be addressed in order to obtain such reductions at a larger scale.

The biodeposition process in native mammals: spatial distribution and influence of waste products on soil fertility in restored and grazed woodland

“…By the consumption of plant tissues and their return to soil as excretions, large herbivores can modify the quantity of resources that enters the soil (Vaieretti et al 2013). The major impacts of grazing in N cycle are related to ruminants as poor nitrogen converters because only between 5 and 30% of the ingested nitrogen is absorbed by the animal (Luo et al 2010;Rivera & Char a 2021). The remaining 70-95% is excreted and often exceeds plant demands, is lost through gaseous emissions and leaching, leading to decreased N stocks in grazed areas (Rivera & Char a 2021).…”

“…The major impacts of grazing in N cycle are related to ruminants as poor nitrogen converters because only between 5 and 30% of the ingested nitrogen is absorbed by the animal (Luo et al 2010;Rivera & Char a 2021). The remaining 70-95% is excreted and often exceeds plant demands, is lost through gaseous emissions and leaching, leading to decreased N stocks in grazed areas (Rivera & Char a 2021). At the study site, previous research has determined that soil N storage is significantly lower in areas with cattle compared to protected ecosystems within the RBÑ (Asner et al 2003), decreasing N availability for vegetation growth and possibly causing the lower N content observed in mammalian feces.…”

The sustainable transformation of the Colombian cattle sector: Assessing its circularity

“…Examples of intensification recommendations for the local Colombian context include the adoption of improved pastures with higher fertilization rates than current ones [18], rotational grazing schemes [30], use of tropical forages with secondary metabolites with potential to reduce methane emissions [31] and the adoption of silvopastoral systems [32,33]. Although it has been acknowledged that all these practices can have potential to reduce the environmental footprint of the Colombian livestock sector [26,[34][35][36], several barriers limiting their adoption exist, including high costs and risks, and limited access to financial capital, technical assistance and information.…”

Effect of Tithonia diversifolia (Hemsl.) A. Gray intake on in vivo methane (CH4) emission and milk production in dual-purpose cows in the Colombian Amazonian piedmont

“…To contribute to sustainable livestock production, these forages must be associated with an increase in milk and meat productivity, with desirable adaptive and nutritional characteristics and a reduction in GHG emissions and other environmental impacts ( Tapasco et al, 2019 ; Arango et al, 2020 ). Well managed forage base systems, including silvopastoral systems (SPS) could contribute to reduced emissions of enteric CH 4 ( Gaviria-Uribe et al ., 2020), nitrous oxide (N 2 O) ( Rivera et al, 2018 ; Rivera and Chará, 2021 ) and increased carbon accumulation in aboveground biomass and soils ( Landholm et al ., 2019 ).…”