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.





