Hey Mr. Green,

A friend says that a dog requires more fossil fuels than a Hummer. Factoring in food, exercise, vet visits, water, and whatever else (I own neither dog nor Hummer), could this possibly be true? —Ben in Missoula, Montana  

I’m not terribly fond of pets, but do feel a moral obligation to defend Fido against false accusations. Hummers—which are no longer made, thanks mostly to the Chinese government for nixing a deal to outsource the manufacture of the monstrosities —get about 15 miles per gallon of gas. Bowser, even on a luxury diet of pure beef, demands far less energy than that. Even if your dog is constantly ailing, and the nearest veterinarian is hundreds of miles distant, sustaining that ill-begotten beast still could not possibly consume as much energy as a Hummer. And that’s not even taking into account the energy needed to produce a Hummer in the first place--a topic I’ve been pondering since my brilliant deconstruction of the myth that Hummers use less fuel in their wretched lives than it takes to make a Prius. 

To compare dogs and Hummers, I figured that driving the typical 12,000 miles a year in a Hummer would burn around 800 gallons. At 125,000 British thermal units per gallon, that’s 100 million Btus a year. Then, I assumed a stupendously extravagant dog diet of a pound of beef--the most energy-intensive meat--per day. Because dogs need to eat the equivalent of 2 percent of their weight every day, this seems a fair amount, though it fails to give credit the teeny-weeny actual and ecological footprints of Chihuahuas, toy poodles, and other micro-canines. But erring on the side of wolfhounds, a population of some 74 million dogs would consume around 28 billion pounds of beef--roughly all the beef now eaten in the United States. 

How much energy would this luxury doggy diet require? According to the latest energy numbers from the USDA, the total energy expended on beef production, shipping, refrigeration, etc. is around 395.5 trillion Btus. So even on an all-beef diet, the individual dog’s share would be 5.25 million Btus, or only a bit more than 5 percent of the energy burned by a Hummer in a year.

Of course, most dogs—and, for that matter, cats—don’t enjoy such a fabulous diet. The pet food they do get is an assortment of animal and vegetable materials and byproducts that are somewhat lower in quality than beef. If you divide the USDA’s data on total energy expended on pet food by the Humane Society’s cat and dog population estimates, you’ll  find that the average energy consumption was about 2 million Btus per pet per year, or only 2 percent of the energy a Hummer burns in a year. 

 [An earlier version of this post included a wrong order of magnitude for the total energy expenditure of beef. The figure has been corrected.]