Just when the fear that eating animal fats will kill you appears to be fading, concern is growing that cattle are intrinsically bad for the planet. So, it’s refreshing to see some countering truth peek through the clouds of fear in a brand new scientific paper from Michigan State University, “Impacts of soil carbon sequestration on life cycle greenhouse gas emissions in Midwestern USA beef finishing systems” (Stanley, et. al., 2018).
The work is based on Paige Stanley’s recently completed research for her Master’s Degree under the supervision of co-author Dr. Jason Rowntree, who is integrally involved in grass-fed beef research and serves as the chairman of the Grassfed Exchange.
The methane problem
The primary concern regarding cattle and the environment stems from methane, which is the dominant gas that burns on your stove or water heater. It is also the simplest hydrocarbon molecule that nature can make without oxygen.
The rumen of a cow is an anaerobic environment, which means it has no oxygen. We can’t eat grass and digest it well, but your cow can because she has a diverse community of microbes in her rumen that break down very complex carbohydrates like cellulose. And therein lies the rub. Methane (CH4) is a so-called greenhouse gas that helps trap just a bit more of the sun’s energy in our atmosphere. Many people look only at these numbers and jump to the conclusion that cows are inherently and irreversibly bad. But as we like to say, it’s not the cow. It’s the how.
A historical view
Grazing ruminants were here long before us. An earlier paper (Hristov, 2012) set out to calculate how much methane might have been emitted by the native bison, elk and deer populations before we started raising cattle, sheep and goats. Hristov estimated that the historical ruminants of North America emitted somewhere between 74 and 166 teragrams (Tg)/year of what are called CO2 equivalents of methane. (1Tg = 1 million metric tons.)
So, methane emissions from our livestock are no greater than what ruminants produced before the coming of domesticated herds.
The MSU experiments
Michigan State University produces grass-fed beef at its Lake City Research Station. For a number of years the station has employed adaptive multi-paddock (AMP) grazing methods and tracked a number of parameters including not only methane, but also how much new, carbon-rich organic matter was accumulating in the soil.
Then they did the math to determine what went out into the atmosphere and what went into the soil. They did the same for animals going to a traditional feedlot.
In both cases the researchers accounted for water, fertilizer, fuel and other inputs. To get an apples-to-apples comparison, they measured both systems in terms of carcass weight.
An interesting caveat
It turns out that the measured methane emission was 36% lower than the standard method predicted. If the original analysis had used this emission, the emissions would have been closer to a wash even before the carbon sequestration factor was included.
As noted by the authors, this is likely because of the “more digestible, and higher quality forages” being grazed in the AMP system.
But now that we see the bigger picture, we intuitively know that the wild ruminants of the past were pumping more carbon into the soil than they were emitting into the air. A ruminant-filled planet thrived before us, and it can again today.
This is just one study at one place and time, and only for the finishing stage of beef production. The cow-calf phase of beef production covers more acres and time on a national scale. Although the same principles apply, and thus we might expect some material improvements in terms of net greenhouse gas emissions for calf production as well, the full life-cycle is worthy of further research and analysis. – Graze Online