The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, "hmm.... that's funny...." Isaac Asimov

Friday, December 31, 2010

Food in Winter: Eating Locally Means Preserving Locally

Food prices have been rising; between June and November 2010 the prices of staples such as wheat and corn have gone up by more than 25% (1). One likely reason is rising energy costs. Food production is energy-intensive, and if the cost of energy rises, so must the price of food. In the U.S., we consume over 10 quadrillion Btu (quads) of energy a year, about 10% of our total energy consumption, to produce the food we eat. Some of this energy is used to manufacture fertilizer and pesticides and to run farm equipment. Much of the energy is used to transport, process, package, distribute, and market food items. But the biggest chunk of energy used by the food system is for storing and cooking and otherwise preparing food, most of which happens in the home (2).

It’s looking increasingly likely that global oil production has peaked; even some previously skeptical commentators have come to this conclusion (3). If production has peaked, global oil supplies will eventually start to decline. It is not clear whether this decline will be steep or gradual or how soon it will begin. If the decline is steep, the price of liquid fuels such as gasoline and diesel could rise rapidly, and there could be shortages. The food system, with its many interconnected links dependent on liquid fuels, is vulnerable, and this means food itself could become more expensive or even scarce.

One solution, for areas with suitable land and enough rain, is backyard food production and local agriculture. Locally grown foods, less dependent on transportation and distribution networks, should be somewhat immune from the worst effects of price increases and possible shortages of fuels (4). But local food production cannot be depended upon if the supply ends when the growing season ends. Even with hoop houses and other technology to extend the harvest, in most of the U.S. locally grown food will not be available for half the year unless it’s been preserved. If shipments from California, Florida, and Mexico become expensive or unavailable, there better be something in the refrigerator, the freezer, the cold cellar, the smokehouse, the pickle barrel, or the pantry.

There are many tried-and-true methods of food preservation. An important aspect is energy use. Using estimates in the literature (5) and my own calculations I have estimated the energy consumption of a variety of these methods. Freezing and refrigeration score especially poorly, in part because electricity must include the energy required to produce it, and also because a freezer must run for an entire storage period whether it is full of food or down to one item. Drying requires a lot of energy. But once dried, foods will keep for many years if properly stored. Canning requires energy too but canned vegetables and fruits will keep well for several years. And some canned foods such as tomato sauce (pictured above), if made from home-grown, vine-ripened fruit by someone with anything like the skill of my wife Louise, are better than what you can buy.

Local food-growing systems will become more meaningful and important to the degree that they address the importance of food preservation.

(1) Foley, John, Food Prices Face a Perilous Rise, NY Times, 12/29/10
(2) CSS, 2007, Factsheets: U.S. Food System,
(3) See Krugman, Paul., The Finite World, NY Times, 12/26/10
(4) I am referring here to field-grown crops, not the extremely energy-intensive food production of heated greenhouses.
(5) Smil, Vaclav, 1991, General Energetics, John Wiley & Sons, NY

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