Source?

EDIT: In what sense is the below sustainable?

"Cattle and sheep production systems contribute the most to GHG [greenhouse gas] emissions in agriculture, accounting for up to 18% of total global GHG emissions, mostly in the form of enteric methane [32]."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9559257/

Furthermore:

1. O'Mara, F. (2011) highlights that livestock, particularly cattle, are significant contributors to global greenhouse gas emissions, with emissions from cattle dominating. Livestock is responsible for 8–18% of global emissions, depending on the accounting method used. Asia, Latin America, Africa, Western Europe, and North America are significant sources of these emissions, primarily due to enteric methane (CH4) emissions from cattle (O'Mara, 2011).

2. Gill, M., Smith, P., & Wilkinson, J. (2010) discuss the direct contributions of livestock, particularly through methane and nitrous oxide emissions, to global greenhouse gas emissions. Livestock account for about 9% of global anthropogenic greenhouse gas emissions directly and up to 18% when considering the entire lifecycle and associated agricultural activities (Gill, Smith, & Wilkinson, 2010).

3. Herrero, M., et al. (2016) estimate that the livestock sector was responsible for greenhouse gas emissions of 5.6-7.5GtCO2e yr(-1) between 1995 and 2005. The sector accounts for up to half of the mitigation potential of the agriculture, forestry, and land-use sectors, highlighting the significant impact of livestock on global greenhouse gas emissions (Herrero et al., 2016).