The world’s food supply is now unimaginable without the tomato, which although often called a vegetable is actually a fruit of the Solanum lycopersicum species, native to Central and South America. It gradually diffused through the world after 1500, finally becoming the world’s largest “vegetable” crop, with recent harvests around 180 million metric tons a year.
But, increasingly, store-bought tomatoes are grown not in fields but in greenhouses, usually hydroponically either under glass or in long, plastic-covered tunnels. Here the energy cost of production is substantially higher. Direct energy inputs include electricity, gasoline, and diesel fuel; indirect energy costs involve the production of fertilizer (particularly nitrogen), pesticides, fungicides, and plastics and metals (not only for covers but also for cultivation troughs and copious pipes and heaters).
In the United States, tomato greenhouses are concentrated in California, Minnesota, and New York. The world’s largest concentration of plastic greenhouses lies in the southernmost part of Spain’s Almería province; you can see it on satellite images, and you can even move between some of them using dystopic Google street views.
A 125-gram tomato of Almería that is grown in an unheated plastic tunnel requires about 150 kcal; one grown in heated structures, about 560 kcal. It provides about 22 kcal of food energy, making the two kinds approximately 1:7 and 1:25 tomatoes. And with economies of scale favoring large-scale centralized production and long-distance shipping, the required storage, packing, and trucking to a regional distribution center raises the total energy cost to 460–875 kcal/125 g, raising the ratio to between 1:21 and 1:40.
Read the complete article at www.spectrum.ieee.org.