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Dear Pablo: I grow plenty of vegetables in the summer but can't in the winter. In addition to preserving what I can in canning jars, I am thinking about getting a freezer chest to store my vegetables into the winter. I am concerned about the energy use and am wondering if it is better or worse for the environment than buying vegetables that are shipped from far away.
There are so many rewards in producing and preserving your own foods, and extending the availability of your own produce into the winter can be a healthy and environmentally friendly way to feed yourself and your family. This question may also be interesting for readers that don't have a green thumb because you could store fresh vegetables from your summer farmers' market in a freezer chest as well.What Is The Impact Of A Freezer Chest?
The environmental impact of manufacturing a freezer chest can be assumed to be negligible in comparison to the energy consumption over its functional life. It is also assumed that the refrigerants used in the unit are properly disposed of in accordance with federal or state laws. The remaining impact then, is the energy use. An Energy Star rated 15 cubic foot (0.4 cubic meters) freezer chest will cost you about $500 and uses an estimated 357 kilowatt-hours (kWh) per year. Even if you have the nation's dirtiest electric supply (that distinction goes to the SPNO eGrid Region, which covers mainly Kansas), this electricity use will cause only 317 kg of CO2 emissions. By comparison, the average car emits over 5,000 kg per year. You can learn more about the emissions from your local electric grid from the US EPA.
What Is the Impact Of The Shipping Produce?
The weight of fifteen cubic feet of frozen vegetables can range from 30-45 pounds according to one source, or as much as 525 pounds according to another source, so the comparison should be made to that same amount of fresh produce being flown in from the opposite hemisphere. For long distance air freight, 1.58 grams of CO2 are created for every kilogram transported by a kilometer (a unit called kg-km). For the 45 pound (20.4 kg) comparison we will assume a distance of 5,000 miles (8,047 km), or 164,159 kg-km. The resulting emissions, which do not consider the associated ground transportation, refrigeration, and distribution, are 259 kg (or 3,022 kg if we go with the 525 pound estimate).
Case Closed? Can Shipping By Air Freight Really Be Better?
The freezer chest creates 317 kg of greenhouse gas emissions while the air shipment of 45 pounds produces only 259 kg, so air freight clearly wins, right? Not so fast. There are several additional factors to consider, each of which have the potential to give the freezer chest the edge:
- The freezer chest doesn't need to remain plugged in once you have used all of the produce. Unplugging it while you are enjoying fresh produce directly from the garden or your local farmers' market can cut the energy use of the freezer in half.
- We assumed the dirtiest electricity supply in the country. If your local utility provides 100% of its electricity from hydro, or if you have solar panels, the freezer can be said to be carbon neutral.
- A freezer chest is only one part of your food preservation options. Produce can be stored in canning jars, it can be dehydrated or pickled, or it can be stored in a root cellar. If you are committed to local/seasonal produce enough to buy a freezer chest, chances are that you are storing food in these other ways too. This means that you are potentially offsetting far more than just 45 pounds of air freight.
- Finally, there is a lot of variability in the amount of produce that you can actually pack away in a freezer chest. Anywhere between 30 and 525 pounds seems reasonable, depending on the density of what you are packing away.
There are several variables to consider, but when it comes to making the more environmentally friendly choice, getting a freezer chest gets at least one thumbs up from me.
Pablo Päster is a weekly columnist for TreeHugger.com, an experienced greenhouse gas engineer and the Senior Environmental Program Manager at Hara Software. Send your questions to Pablo(at)TreeHugger.com or submit the via this form and connect to his RSS feed.
More TreeHugger Articles On Preserving Food:
Agriculture Takes Over The World
Frugal Green Living: Freezer Sales are Way Up
Frugal Green Living: Preserving The Harvest
The Pantry Is Back