How can livestock be a part of the climate solution? Doesn’t methane have more warming power than CO2?
Yes. Using the ‘carbon dioxide equivalent’ (CO2e) metric, methane is commonly referred to as being anywhere from 28 to 100 times more powerful than carbon dioxide, but it is important to factor the lifespan of the gases into the equation. When it comes to the difference between methane and carbon dioxide, the most important aspect that is missed by the simple metrics is full consideration of the gases’ different lifespans in the atmosphere. It takes the CO2 released from fossil fuels around 1000 years to be redeposited back into the earth but it only takes methane belched by cattle around 12 years.
Methane is a live-fast, die-young gas. Once released into the atmosphere, methane traps heat much more efficiently than carbon dioxide, but only over the course of around a decade. After this point, it is broken down into carbon dioxide and water, among other things, in a complex set of chemical reactions. Once methane becomes carbon dioxide is remains stable in the atmosphere until it is drawn down.
Carbon dioxide, on the other hand, is a ‘slow and steady’, tortoise-type greenhouse gas. It has a lower potential to heat the atmosphere, but it is a relatively stable gas. This means that unless it is drawn out of the atmosphere through a natural or human process, it continues to heat the atmosphere more-or-less indefinitely. It doesn’t get broken down in the same way that methane is.
Adding carbon dioxide to the active biosphere is a bit like adding water to a sealed water tank. Just like adding water to the tank raises the water level in the tank, so too does adding carbon dioxide to the biosphere. Unless it is removed by some additional means, adding more of both water and carbon dioxide over time results in more being present. This is pretty simple.
Adding methane works differently, it’s a bit more like a tank with an old-slow-to-start, automatic pump attached. This pump tries to remove water at the same rate that it’s added, but takes a long time to start. In the short term, adding more to the tank lifts the level in the tank, but in time – once the pump kicks in – as much is removed as is added. If the rate that water is added remains stable, eventually the amount in the tank will stabilise at a higher level. The breakdown of methane in the atmosphere works in a similar way. Changing the rate that methane is added causes a short-term shift in the amount of methane present, but if the same rate is sustained, then after about a decade the total amount in the atmosphere stabilises as additions are balanced by removals.
Diagram courtesy of the Climate Council.