BY: Ethan Brown
Do our diets affect climate change? Yes—a lot, actually.
In fact, over a fifth of each person’s carbon footprint comes from food. In this five-part series, we will break down some primary sources of these greenhouse gas emissions and discuss how we can reduce them.
First, we’ll look at food production, which, at 40%, is the stage of the food cycle that generates the largest amount of greenhouse gas emissions.
What are some main emissions sources?
On average, red meat is by far the worst offender, largely due to a process called enteric fermentation (or as the media often calls it, cow farts). Animal products generally have larger emissions than plant products, but again, the categories on the chart below are averages across a wide variety of foods. For example, within the broad category of fish, options like anchovies, herring, sardines, and Alaskan pollock have far lower emissions than lobster, shrimp, or bluefin tuna. But for the majority of us who don’t have time to compare the exact emissions of almond milk versus soy milk versus oat milk, these averages are plenty of information to make environmentally-conscious choices.
At any farm, there will be a substantial amount of carbon dioxide emissions from fossil fuels used to power furnaces, trucks, tractors, fishing boats, and other machinery. Crops also require the transportation of seed, fertilizer, and water to the farm, and livestock require transportation of feed. Creating land to grow crops or house livestock also often requires deforestation, which not only releases carbon dioxide when cutting down the trees, but means that there are then less trees to remove carbon dioxide from the atmosphere.
COW FARTS… SORT OF: I can’t count the number of clickbait headlines I’ve seen saying that cow farts are to blame for climate change. And they’re not entirely wrong. Cows, buffalo, sheep, and goats—also known as ruminants—all have a four-compartment stomach. When food enters the first compartment called the rumen, microbes break down the food and through that process, produce methane: a greenhouse gas with 34 times the global warming potential of carbon dioxide. Ruminants then belch that methane into the atmosphere (so not quite farting). According to the Climate & Clean Air Coalition, ruminants account for up to 30% of global methane emissions.
MANURE: Only some animals produce methane through rumination, but all animals produce methane through pooping. Manure is a mix of organic material and water. As it decomposes, it releases methane. The amount of methane released varies depending on the composition of the manure (water content, acidity, nutrient density) and external factors such as moisture, temperature, and oxygen availability. Dry, cool, oxygen-filled environments lend themselves to the least methane generation. Poor manure management systems are quite common, also leading to substantial unnecessary methane emissions. During decomposition, the ammonia (NH4) in manure will also undergo chemical reactions to turn into nitrous oxide (N2O), a greenhouse gas with 298 times the global warming impact of carbon dioxide.
NITROGEN FERTILIZER: Another major emitter that affects all food groups is nitrogen fertilizer, which plays an important role in enriching soil to grow crops. The process of producing nitrogen fertilizer requires immense amounts of energy to transform dinitrogen (N2) in the air to ammonia (NH3). From there, much of the ammonia degrades and is released into the atmosphere as nitrous oxide. Nitrogen fertilizer contributes to emissions from plants and animals, since the fertilized crops become animal feed. Like manure management, farmers can adopt practices to limit their emissions such as avoiding fertilizer applications during rainy weather (wet soil microbes can produce bursts of nitrous oxide) and making adjustments to the way their fields are tilled (plowed).
More food for thought…
CORN IS EVERYWHERE: During the Great Depression, to keep farmers from going out of business and to keep food affordable to the public, the United States government began subsidizing corn. Almost 100 years and several corrective policy attempts later, the government is still subsidizing corn and it is everywhere. It’s popcorn and chips, it’s in our drinks and candy as high-fructose corn syrup, and all that only accounts for less than 10% of the corn grown in the United States. The remaining 90% is used as animal feed (even though cows naturally eat grass and chickens naturally eat an omnivorous diet of seeds, worms, insects, and plants) and ethanol. There’s debate as to whether corn-fed animals emit more greenhouse gas than those fed their natural diet, but when used for ethanol, corn is absolutely a carbon dioxide emitter. Biofuels like ethanol and biodiesel (made from soybeans) are renewable energy (unlike oil and coal, we can grow more corn and soybeans whenever we want) but not clean energy (biofuels release carbon dioxide when burned, not to mention the deforestation and machinery required to grow the crops). Supporting farmers and keeping food cheap is essential for the economy, but perhaps corn subsidies are a double-edged sword.
ONION MILK: Scientists in Spain have discovered that chemicals found in onions and garlic can actually change the chemical composition of the cow’s rumen and substantially lower its methane emissions. Unfortunately, it also makes the cow’s milk taste like onions. If scientists can figure out how to prevent the onion flavor from entering the milk, perhaps there is a solution to ruminant methane emissions after all!
So, what can you do?
ADJUST YOUR DIET: No, you don’t have to go vegan to make a difference (but if you’re able and willing, a vegan diet will have the largest emissions reduction). If you have food allergies or sensitivities or dietary restrictions that prevent you from going vegan or you just love meat (I’m allergic to peanuts and sensitive to other legumes and I love meat, so I completely understand the difficulty), you can still take on a more climate-conscious diet. The most impactful dietary adjustment would be to cut down on consumption of products from ruminants such as beef, lamb, and dairy. The average American eats three hamburgers per week, and each one releases the same amount of greenhouse gas as a 200-mile drive in an average car. If every American ate just one less burger per week (or ate a plant-based Beyond Burger or Impossible Burger), imagine the impact!
RESPECT OTHER PEOPLE’S DIETS: As the above graph shows, a vegan diet is the ultimate greenhouse gas saver. Whether it’s for environmental, animal rights, dietary, or other reasons, I personally have the utmost respect for vegans. As such, it is disappointing to see the challenges that vegans face in a world biased against them. A 2015 study from psychology professors Cara MacInnis and Gordon Hodson found that “vegans are viewed more negatively than atheists, immigrants, homosexuals, and asexuals,” and another analysis from Johns Hopkins University revealed that “labeling a product ‘vegan’ causes its sales to drop by 70%.” According to Matt Ball of the One Step for Animals, many vegans will admit that they can be a bit annoying with their beliefs and activism. Amidst these conflicts, sticking to facts is crucial, especially the fact that people without allergies or other restrictions can garner enough protein from a vegan diet. It is okay to disagree with elements of some vegans’ activism and still promote the climate benefits of a plant-based diet.
This is part 1 of a 5-part series on the climate impacts of food.