Why we should stop eating (industrial) meat

Followers of agriculture and energy issues have noticed these subjects getting a lot of press lately, what with the combined effects of climate change, biofuel production, developing world dietary shifts, and petroleum scarcity driving prices significantly higher. Especially country kids like me, the natural instinct is to plant a big garden and exhort others to do the same, and this is indeed what I have done, as reported previously in this very blog. Prominent crunchy types including Michael Pollan and Barbara Kingsolver have similarly advocated gardening as a solution to the food crisis, and people are increasingly paying attention – Fedco Seeds sent a flyer with my shipment this year remarking that they had never had such a good season.

But renewable energy engineering folks also have a habit of running back-of-the-envelope calculations to determine whether a particular solution has any hope of succeeding. I did some simple estimates some time ago that showed the difficulty of making a significant impact with dooryard gardens. For example, the classic garden vegetable is the tomato. How many people could I feed if I grew nothing but tomatoes? Iowa (which is a pretty good place to grow things) says that typical yields are around 14,000 lb per acre, though much higher yields are possible. Florida says that a 148g tomato provides 25 calories, or about 77 calories per pound. So an acre of tomatoes might produce about 1.08 million calories, which seems like a lot. But a person eating a 2000 calorie per day diet will eat 731,000 calories per year. That means an acre of tomatoes could only feed about 1.5 people. I’m not sure how familiar most readers are with the size of an acre, but it’s pretty big – about the size of a football field. A decent suburban lot is maybe a quarter of an acre. My front yard garden is around 1000 square feet, about a fortieth of an acre.

So, we gardeners aren’t going to solve the food crisis with homegrown tomatoes, as tasty as they might be. What about something with more substance? My wife and I really like broccoli. How much broccoli would we have to plant to keep ourselves from going hungry? The internets and a hand calculator quickly provide an answer by the same method as before. This source gives an anecdotal yield for California broccoli as 6.5 tons per acre per year. A rough estimate of the food value of broccoli from nutrition data indicates broccoli has 11 calories per 1.1 oz spear, or 160 calories per pound. So an acre of broccoli can yield 6.5T * 2000lb/T * 160cal/lb = 2,080,000 calories per acre, so that acre of broccoli can only feed about 2.8 people.

Poking around with other garden vegetables gives similar values. To get real feeding power, you need grain (wheat comes out at about 5 people per acre), or (a real champion) potatoes. An acre of Michigan soil gives around 22000 lb of spuds at a whopping 318 calories per pound, for an impressive 10 people per acre. If I planted my entire garden in nothing but potatoes, I could feed a quarter of a person. That’s not insignificant, but it’s not exactly a stunning yield. For reference, the state of Massachusetts has about 0.8 acres per person of total land area.

So we conclude that small vegetable gardens can make at best a marginal contribution to the actual feeding of people. Perhaps the most significant benefit of gardening is that it reduces the amount of time the gardener has for other activities, which likely consume significantly more petroleum, and decreases the amount of lawn (lawnmowers are gawd-awful polluters, much worse on a per-gallon basis than cars).

I like to grow vegetables, so it’s not as if this analysis changed anything about what I am likely to do, but one might ask, what sort of dietary decisions CAN make a significant difference in a family’s food consumption? The obvious answer is, stop eating meat. Or at least, stop eating meat of the usual grocery store variety. That’s easy for me to say, I haven’t eaten the stuff since I was maybe 15, but the logic is hard to get around and the impact is significant, because conventional meat production involves packing animals in confined spaces and stuffing them full of edible grain. This has proven to be the most cost-efficient way to produce meat for market, and it’s shortcomings are legendary (check out Fast Food Nation, Omnivore’s Dilemma, etc). But never mind the environmental and moral catastrophe of factory farming – the thermodynamic efficiency of a cow is not all that impressive, and it takes something like 8 units of food energy in the form of grain to produce one unit of food energy in the form of meat. That’s in addition to all the fossil fuel that it takes to make fertilizer to put on the field, run the tractors to grow the grain, truck it around, and the like. Chickens and pigs are somewhat better, but still much less efficient than just eating the grain in the first place.

There is a somewhat better argument to be made for meat of the sort that’s raised the old fashioned way, grass fed on pasture, especially if the land used is unsuitable for row crops. Lately there has been a bit of a movement in this direction among food aficionados, but it is still very much a specialty and unchristly expensive. Perhaps a similar case could once have been made for eating wild fish, but the stocks are so depleted that taken as a whole the global fleet burns almost as many pounds of fuel as it catches pounds of fish (article). So when you eat swordfish, shrimp, or the like, you are in effect literally eating at least that much crude oil – not exactly an appetizing thought (disclosure – I occasionally eat fish, especially to avoid discomfiting my hosts etc.) At my previous job I had a brief encounter with farmed fish, and it’s no picnic either – raising farmed salmon involves catching vast quantities of “inedible” fish species (menhaden and the like) and grinding them into pellets to make feed, which is converted at a 2 or 3:1 ratio into the desired end product. The feed species are getting depleted, so the industry is attempting to cut the feed with corn etc,, but as it turns out salmon didn’t evolve to eat grains, and they have a tendency to get sick. In any case, the fish must be fed dye to make their flesh red, since they don’t get the natural food that would turn them the usual color.

Anyway, this post is at least long enough at this point, but I hope the point is clear. Grow a garden if you like, but if you want to do your part to relieve the global food crisis, stop eating industrial meat.