The beef value chain is a complex system, which includes the production of feed, the raising of beef cattle on grass and in feedlots, processing plants, retailers, food service operations, and the consumer. Broadly, the beef value chain can be split into pre-farm gate (all the processes and activities prior to the harvest of the beef animal) and post-farm gate (all the processes and activities that take place once the beef animal leaves the farm, ranch, or feedlot). Approximately 80% of greenhouse gas (GHG) emissions produced per unit of beef in the United States occur in the pre-farm gate part of the beef value chain.1
The prefarm gate portion of the beef value chain can be split into three major phases: the cow-calf phase, the stocker or backgrounding phase, and the feedlot or finishing phase.
Feedlots are often believed to be responsible for the largest portion of beef’s GHG emissions. In reality, the cow-calf phase is responsible for most (approximately 70%, Figure 1) of the GHG emissions in the beef value chain prior to the harvest of beef cattle.2-5 Factors that influence GHG emissions in each phase deal with three primary components: the number of animals maintained in each phase at any given time, the diet of the animals in each phase, and efficiency of feed conversion.
Animals in the cow-calf phase are either pregnant or lactating cows, replacement heifers, growing calves, or bulls. Cows that are lactating have higher daily energy and nutrient requirements than other mature, non-lactating animals. Cattle in the cow-calf phase of the industry are largely raised on pasture, consuming mostly forages that are typically of lower quality or digestibility. It has been well established by scientific research that cattle consuming feed with low digestibility tend to generate more methane emissions (a GHG 28 times more potent at trapping heat in the earth’s atmosphere than carbon dioxide6) as compared to cattle eating more digestible feed (e.g., cattle in feedlots eating high-grain diets).5 While cattle in the cow-calf phase produce more methane emissions per animal due to their diet of mostly grass and hay, those feeds are also unsuitable for human consumption; therefore, there is a sustainability tradeoff between methane emissions and the ability of cattle to convert grass into human usable products (e.g., beef, leather).2
From the cow/calf sector, cattle are typically weaned and sold and enter the stocker/backgrounding phase, where they spend additional time grazing forage. However, the GHG emissions from the stocker/ backgrounding phase are lower because the number of animals maintained in this phase is smaller, and they spend a shorter amount of time in this phase. To put this in perspective, cattle generally have one calf per year as a function of their gestation interval (which is similar to that of a person), so an entire herd of cows must be maintained for an entire year to produce one year’s worth of cattle that may spend approximately 120 days in the backgrounding phase. Occasionally, weaned animals enter the feedlot directly and skip the stocker/backgrounding phase altogether.