Food and diet

There are a lot of people in the world, and it takes enormous amounts of food to nourish them. The average American, or anyone from a richer country, eats about one ton (2000 pounds or 1000 kilograms) of food each and every year. The calories of the typical American diet, which isn’t the healthiest one, includes about 10% from fruits and veggies, 10% from dairy, 15% from sweeteners, and about 20% each from grains, added oils/fats, and meat/eggs/nuts (see here for more). Producing the varied diets that Americans and people from other wealthy nations eat takes more than one acre of land per person. Unfortunately, there just isn’t enough land for the whole world to eat the same way we do. In fact, for everyone to eat like Americans it would require almost three times more agricultural land than there currently is on the planet. Less land intensive diets are completely possible, and in fact more that half the world’s population does eat a diet that is possible with the farmland we currently have available.

Putting all of that food on the typical American’s plate releases 2.5 tons of carbon dioxide and other greenhouse gases into the atmosphere. But where do all those emissions come from? The first main source is all of the energy and fuel needed to build and run all of the heavy equipment, the tractors, implements, the trucking, shipping, etc. In the current economy, the vast majority of this energy comes from oil and other fossil fuels. Second, many farming practices degrade the soil causing it to release the carbon that is trapped in the soil as ‘soil organic matter’. When soils are disturbed through plowing and tilling, this carbon tends to escape to the air causing reduced fertility as well as air pollution. Third, applying manure and synthetic fertilizer, which is needed to increase the growth rates of our crops, produces byproducts like nitrous oxide that escape into the atmosphere. Finally animals, particularly cows and sheep, belch a lot of methane as they digest their grassy diets. For more information, see here and here.

So the figures mentioned above for land use and emissions represent the current state of affairs, but new technologies and practices are changing agriculture all the time. For decades, the yields of most of our crops have been rising steadily, the amount of carbon dioxide and other pollutants has been going down, and these trends should continue. ‘Big data’ and artificial intelligence are now creeping into agriculture, allowing farmers to use less fertilizers, pesticides, water, and other resources. Things aren’t all peachy, though. Much formerly productive land has been damaged by erosion and salinization and there are significant problems with losses of biodiversity because of pesticides and other agricultural practices. The takeaway is that agriculture is getting more sustainable with the passing years, but there is plenty of room to speed up the adoption of better practices.

What can you as an individual do?

Don’t waste food. For the average person, this is the single biggest thing that you could do to reduce the footprint of your diet. Americans are some of the worst offenders, throwing away 1/3 of their food. Some of this is food that doesn’t sell at grocery stores or that is left behind on the table at restaurants, but more of it is the food that goes to waste in the home. We tend to buy fruits, veggies and meat that we don’t eat before they goes bad, throw out other food past the expiration dates, and don’t get around to eating those leftovers. Solving this problem alone would reduce the impact of food by that 30% that is being wasted. For actions that you can take, it is easy: buy only the food that you know you are actually going to eat. If they currently go in the garbage, learn to love those leftovers, and make sure to have a menu planned out for those veggies in the back corner of the refrigerator.

Cut back on beef. This is one that I think that nearly everyone is now aware of, that eating plants is more sustainable than eating animals. However, when one digs into the numbers a bit further, beef stands far above other meats when it comes to environmental impacts (lamb is similar but isn’t eaten much in North America). This is tough to hear for anyone who likes a good steak, that beef has over double the impact of pork, or five times the impact of the rest of the typical North American diet. The graph below shows the outsize impact of beef on our diets, accounting for as much as half of the greenhouse gas emissions of a beef-lover’s diet. Cows also need much more land than the rest of our food, so it is a double whammy of both high emissions and high land use. Some advocate a vegetarian or even vegan diet, and it is true that these do have even lower impacts, but one can get the majority of the sustainability gains just by cutting out (or drastically cutting back on) beef and lamb.

Graph from Shrink that footprint

Where and how the food is grown. Unfortunately there is no simple takeaway message for the sustainability of eating locally vs. globally, or eating organic vs. conventionally grown food, or other decisions along these lines. There are trade-offs to all of these, and the devil is in the details. There are certainly better and worse options, it is just that there aren’t easy rules of thumb to follow. For example, organic farming may produce less greenhouse gas emissions for a certain crop, but may at the same time have lower yields per acre. Or one may think that buying local will reduce shipping costs, but global supply chains are very efficient and it may very well be that the farmer driving 40 miles to the farmer’s market produces more emissions per pound of food than produce shipped from across the country. It is also the case that people don’t choose to buy local or organic only for sustainability reasons, as concerns such as a connection to local farms or concerns about the quality of food also drive these decisions.

For the moment, we are going to stick to just these two major guidelines about food waste and beef, which if universally adopted would immediately drop US food emissions by half. If other very clear guidelines emerge, we’ll attempt to add them here. It is also important to take other considerations into account for our food, to make sure that you are eating a healthy diet, and that you follow a path that doesn’t make it feel too much like sacrifice, as it is extra difficult to stay on a sustainable pathway if it feels like a reduction in quality of life. All that said, there are many opportunities for you to take more action beyond these steps, but you will need to put in the work to educate yourself further, and look into the ins and outs of issues like eating local or organic, or getting involved in the production of your own food.