The youth climate strikes around the world are urging political leaders to take action to curb greenhouse gas emissions (GHGs) to slow down global warming. But if you want to reduce your carbon footprint, what we choose to put on our plates can play a major role because of chemistry!
All that hot air is not just carbon dioxide. Cow belches and manure are a significant part of the problem when it comes to GHGs, and that means we need to talk about methane and nitrous oxide too.
Studies on global warming calculate GHG reduction targets with a formula called CO2E or Carbon Dioxide Equivalents. This is a blend of the global warming impact of the three major GHGs: carbon dioxide, methane and nitrous oxide, over time. But these gases behave differently, have different lifespans and come from different sources.
Aside from producing C02, animal agriculture is also a major source of methane and nitrous oxide, and beef is the most emission-intensive food. (Cattle produce 41 percent of all livestock GHGs). That brings us back to methane and cows passing gas. Ruminant farm animals have a four-part stomach system to aid digestion, and they produce large amounts of methane from fermentation in their gut.
For nitrous oxide, major sources are manure and nitrogen-rich fertilizers used to grow crops for animals. The approximately 25 billion farm animals alive at any one time produce huge amounts of manure. An average dairy cow produces 112 lbs. a day! Why does this matter? Because methane and N2O are more powerful agents of global warming than CO2 even though they have shorter life spans.
It plays out as heat-trapping power vs time.
- Methane traps 25 - 33 times more heat than CO2 but remains in the atmosphere for 12 years.
- Nitrous oxide traps 289 times more heat than CO2 and remains in the atmosphere for 112 years.
- CO2, the most abundant GHG, accumulates and persists for millennia.
So, while most of the focus is on carbon dioxide, limiting methane and nitrous oxide would also have a significant impact on slowing global warming.
Some downplay the role of methane in the global warming equation because of its 12-year lifespan but the latest science shows we only have about 11 years to meet the Paris climate goals. Major anthropogenic sources of methane are the oil and gas industry, animal agriculture and landfill operations.
In the case of animal agriculture, this dismissal of methane and its 12-year time frame would only be relevant if there were no longer any ruminant farm animals producing it. Instead, there are 3.8 billion cattle, sheep, and goats producing methane every day that will last for 12 more years. This rolling average will continue as long as we keep raising these animals for our meat-intensive diets.
The problem will inevitably get worse before it gets better. So far, we’ve failed to reduce our GHG emissions by nearly enough, and by 2050 the global population is expected to be almost 10 billion and we will need 50 percent more food than we produce today. Our livestock-based, meat-centric diet makes this race all but impossible to win.
Meat producers are trying to respond. Researchers in Texas, Ontario and New Zealand, among others, are working to change feed and digestive systems to produce less methane. This work is still either experimental or small scale, and it won’t have a major impact any time soon on the amount of methane being produced by 3.8 billion belching farm animals.
Every major scientific study on global warming in the last two years has said we need to eat less meat and dairy to slow down global warming. Maybe understanding more about the chemistry will make it easier for us to make those choices.
Sources: Oxford Martin School; UN FAO; Frontiers in Sustainable Food Systems; Our World In Data, Oxford University.