Is it methane or Management? Redefining Cattle's Environmental Impact

By Cam Griffin

Historically, cows have been nature's biological restart button, migrating around in tight herds and pruning mature grasses so that young regrowth can make its way through, and inject fresh carbon into the soil.

Unsurprisingly, after going to the effort of finding palatable plants to graze, biting, ripping, and removing those leaves and stems, they eat it… right? They don’t just spit it out and go “That plants pruned” *spits* “That plants done”, no! They swallow it, and it slides down the oesophagus into their stomach, which is where the “evil” process occurs, digestion. 

In both cattle and humans, the digestion of fibrous plant material is an energy-intensive process that requires fermentation, cattle do this in their rumen, and we use our large intestine. As a by-product of this fermentation process, Methane (CH4) is produced, which exits the body through either farting or burping. Notably, as the fibre content increases in a food source so does the amount of methane generated, and that’s why cattle produce significant amounts of methane when compared to other animals. It’s literally their sole purpose on earth and is why they are born with a 4-part, 110L fermentation vat for a stomach, to walk the grassy plains and recycle fibrous plants into rich soil.

Once Methane (CH4) escapes from the cow's digestive system, it’s released into the atmosphere where it later combines with Oxygen (O2) to form Carbon Dioxide (CO2).

Meanwhile, those plants that have been grazed instinctively try to regrow, and to regrow they must derive energy from photosynthesis. The three ingredients for photosynthesis are sunlight, water, and… Carbon Dioxide (CO2). Healthy, well-managed pastures suck that CO2 in like a vacuum, storing it in the soil and its own tissue where it waits to once again be harvested by a herbivore. Thus completing the biogenic carbon cycle and off-setting the methane released during digestion.

But why is this seemingly natural cycle, which remained in balance for thousands of years, now causing so much debate around Global Warming? A factor that appears to be having a large impact is the shift from feeding mainly Perennial plants to an increasing amount of Annual plants.

When classifying the species that form a healthy pasture, they’re broken down into two categories, Perennial plants and Annual plants. Annuals are generally pioneer species that grow in low-fertility soils, creating the conditions for perennial plants to take over and provide stability in the landscape. From what we can tell throughout history, the savannahs, prairies, and grasslands that evolved under a grazing ecosystem, were all dominated by perennial grasses. However, due to the nutritional value of certain annual species, there’s been a constant increase in farmers mechanically reverting perennial pastures back to annual crops. When we look at the characteristics of both plants, it becomes clear that the issue may not be with methane production, but rather management practices. 

What are Perennials and Annuals?

Perennial plants, once germinated, will continue to grow each and every year without re-establishment unless destroyed by environmental factors like disease or overgrazing. Since they’re here for the long haul, they allocate most of their energy from photosynthesis to growing deep, vigorous roots that can cope with droughts and winter dormancy. These massive root systems are how they can cope with being frequently grazed by livestock and bounce straight back, think Rhodes and Buffel grass. 

So what’s the environmental cost of regrowth for a Perennial Plant? In a well-managed grazing system that matches stocking rate to carrying capacity and allows plants to fully recover before re-grazing, close to nothing. If the land is heavily degraded, some soil amendments may be required to replace missing nutrients, although it’s largely the mass cycling of carbon that drives the system below ground. Depending on where you’re located, Perennials can sequester carbon 365 days of the year. Where I live in Queensland, our pastures grow rapidly during the warmer months and then slow down during the colder months, though not completely stopping. 

Annual Plants, on the other hand, will only survive for a single growing cycle each year, and then die. Because of this, the plant's DNA has learned it’s pointless anchoring down deep roots if the only way for it to reproduce and pass on its genetics is through viable seeds. So in almost the opposite direction to perennial plants, annuals allocate all of their energy upwards into pushing out a large seed head, which is why cereals contain so much energy. In fact, due to its lower fibre content, cattle do produce less methane on a grain-based diet, although that’s only when you measure net emissions from the “ass end” (pun intended) and not the production system as a whole.

What’s an annuals environmental cost of regrowth? Whilst there are slight differences depending on whether the crop is grown for forage to be grazed or grain to be harvested, the re-establishment of annuals is where the lion's share of Carbon Dioxide (C02) associated with conventional beef production is released. Fossil fuels and electricity are burned to power machinery that cultivates the soil, plants the seed, and sprays the crop. They’re burned to manufacture the pesticides, fertiliser, seed and to transport all those inputs on farm. Then if we decide to outsource the cow's mouth, we’ll harvest it mechanically, truck it off farm, handle it, store it and feed it out. 

Additionally, most annuals only grow for between 90-150 days before they die off. Australia's lack of reliable rainfall also means there is generally not enough moisture to double crop the same paddock, so in essence you are sequestering Carbon Dioxide (CO2) for not even half the year.

These emissions, even though they don’t come directly from a beast, have to be traced back and attached to something, which in this case is the industrial beef supply chain. It’s simply not possible, as hard as she may try, for a cow to eat the amount of grass that would sequester and offset that system as a whole.

To be clear I have no issues with Annual plants themselves, they do an awesome job at repairing degraded plots of land and provide a great source of nutrition for livestock. I love seeing wild oats poke through in winter and silk sorghum shoot up in summer, both are extremely palatable and put condition on cattle, the difference is they germinated without my involvement.  

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