Biogenic Carbon Cycle. You can learn more about this graphic at www.bit.ly/UCD-C-cycle. A video discussion with comments from UC Davis CLEAR Center’s director is at www.bit.ly/Rethink-CH4.
Jessie Haas
The climate in which we developed our civilization was shaped by grass and the animals that ate it. Co-evolving, grass and grazing herds built enormous stores of carbon into the soil, cooling the planet. Now, humans are entertaining the idea that methane produced by cows is a major force in warming said planet, and that we must reduce their numbers or emissions. Possibly, but let’s put things to perspective.
Methane (CH₄) is a short-lived greenhouse gas (GHG) about 25 times more potent than CO₂ if measured over a 100-year period. But more crucial is the more immediate effect after it is emitted, and before it decays. Methane that makes its way into the atmosphere has 84 times more global warming impact over a twenty-year period than CO₂. Ruminant livestock emit – mainly through burping – about 80 million metric tons of CH₄ a year, about 28% of human-generated CH₄ worldwide.
But if cattle burps represent 28% of emissions, where is the rest coming from? Turns out that another third of global methane emissions is directly attributable to North American gas production. That’s right – the very profitable fossil fuel industry on this continent emits as much methane as all the world’s cattle, sheep and goats put together. And fossil methane is worse for the planet. Here’s why. Plants grow by absorbing atmospheric CO₂. When plants are eaten, some of that carbon is released as methane, CH₄. It returns to the atmosphere, where it remains for twelve years before breaking down into CO₂ and water, available to grow more plants as part of the biogenic carbon cycle. There is no net gain of greenhouse gases. Fossil methane, however, is new to the atmosphere, and contributes to the increase of GHGs and rising temperatures. Studies published in February, 2020 in the journal Nature show that fossil fuels are a far greater methane source than previously realized. Some scientists believe that CH₄ emissions from fossil fuel production have been underestimated by 25 to 40%.
That may change under the Biden Administration. Biden has expressed interest in new technology that can identify GHG emissions from space. The “superemitter sites” reported on by the New York Times can now be easily identified and forced to shut down.
It’s still worth reducing emissions from cattle, to buy time for other things we need to do. Debate simmers about whether grass-fed animals emit more GHGs than feedlot animals, simply because they fatten slower and live longer lives, or whether cattle managed on pastures are a net positive given their ability to build carbon back into the soil. Meanwhile, progress is being made on reducing CH₄ emissions from cattle.
Some center on a seaweed, Asparagopsis taxiformis. Trials at University of California (UC) Davis have shown that just a sprinkle in feed can reduce a cow’s emissions 30-90%. Mars and Land O’ Lakes are investing in a project with Blue Ocean Barns, which plans to have a product available in California (where reductions in herd methane emissions are mandated by law) in late 2021. Another company, Symbrosia, is trialing a seaweed product at Z Farms in Dover Plains, NY.
AllTech has a yeast culture product available, which doesn’t reduce methane production per se, but increases milk production, thus reducing GHGs per unit of milk. Mootral, a Swiss company, puts out a garlic and citric acid product being studied by UC Davis which inhibits methane production by about 23%–significantly less than seaweed, but with the advantage of having an existing supply chain. There’s also an essential oil product which results in an 8.8 to 20% reduction per kg of milk.
Another approach under serious study is feeding biochar to livestock. Studies show that adding 1% or less of biochar per unit of feed could reduce CH₄ emissions by 10-18%. This has an added benefit of sequestering soil carbon and improving soil health. One Australian farmer who fed his cattle biochar and allowed them to spread it in their manure found it produced “a quantum leap” in the fertility of his farmland. Dung beetles and other soil organisms transport the char underground, where it can sequester carbon for centuries, while vastly increasing the productivity of the land. Biochar typically needs to be inoculated by being mixed with manure, urine, or compost before being spread. Using livestock to feed it through accomplishes the job all in one go, so to speak. It also can improve animal health. Many of us have taken charcoal tablets or fed them to our dogs to deal with an excess of digestive gases. This benefit extends on the global scale.
Jessie Haas is the author of 41 books, most recently, The Hungry Place. She lives in a 450- square-foot off-grid cabin in Westminster West, VT for the past 36 years.
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