Yesterday I gave a talk for some of the world's largest pork producers as part of an event put on by PIC, the world's largest supplier of pork genetics.
In my presentation, I touched briefly on the environmental impacts of meat production, and showed the following slide, which made the rounds on Twitter yesterday.
I thought a few points of clarification and expansion were in order.
First, note that Bailey Norwood and I published a paper a few years ago comparing the costs of producing different meats to producing corn, soybeans, wheat, and peanuts (also note that there was a calculation error in the tables; the corrected tables are here). As we show there, it is generally less expensive to get calories or protein from corn or soybeans or wheat than it is from cattle or hogs. That's one reason we grow such much corn, wheat, and soy - they are incredibly efficient generators of calories and protein.
I will also note that there have been many attempt to calculate the retail cost of eating "healthy vs. unhealthy" food. Here, for example, is a paper by the USDA-ERS. Adam Drewnowski also has several papers on this subject. This work often shows that meat is relatively (relative to many fruits and vegetables) inexpensive on a per calorie or per gram of protein basis, although meat looks more expensive when placed on a per pound basis. If you want really inexpensive calories eat vegetable oil or crackers or sugar; if you want real expensive calories, eat zucchini or lettuce or tomatoes.
The reason I picked lettuce as an example is to make the point that people often do not reason consistently when they argue we should unduly focus on costs of calories. I have never once heard anyone say how "inefficient" production of lettuce or tomatoes or peppers are, and yet I have repeatedly heard this argument about meat.
Another important point is that efficiency or cost isn't everything. What do we get in return? Who cares if lettuce is really expensive on a $/kcal basis? A nice salad is tasty. And healthy. The trouble is that many of our most efficient producers of calories or protein (field corn, soybeans, wheat) are not that tasty by themselves. Given the choice to eat a raw soybean or a raw carrot, I'll take he latter any day despite the fact that the latter is "less efficient."
This discussion reveals another point that Bailey and I discussed in our paper. To get corn and soy and wheat into foods we like to eat requires processing, which takes energy and is costly. Thus, one needs to look at the costs of the foods as we eat them not as they're grown. And, there is generally much less cost wrapped up in the processing of meat and animal products than there is for grain-based products (based on the farm-to-retail price spreads reported by the USDA).
Finally, note that one of the ways we process corn and soybeans into something we like to eat is by feeding them to animals. Animals convert relatively untasty grains into tasty milk, eggs, and meat. And even if some energy is "lost" or "wasted" in that process, we're getting something in return. Here's what I previously had to say about that:
Almost no one looks at their iPad and asks, "how much more energy went into producing this than my old Apple II." The iPad is so much better than the Apple II. We'd be willing to accept more energy use to have a better computer. Likewise a nice T-bone is so much better than a head of broccoli. I'm willing to accept more energy use to have a T-bone than a head of broccoli.