I had a minor freak out yesterday when, for a lark, I did a rough estimate of the energy costs of pressure canning. On a recheck of my calculations I found a major error that put me off by a factor of 1000. Oops! After the error was caught I was relieved to find that - provided I started with water brought up to room temperature, and used a bare minimum of water, and ran a full batch through my pressure canner - I could can salsa for about one-sixth of a fossil fuel calorie for every calorie of preserved food. If you want details about these calculations, find them in the comments.
The larger point is that this got me thinking about the carbon footprint of the food that I preserve. Obviously, it's more energy intensive than the stuff we eat fresh out of the garden. Going into freak out mode over what I erroneously believed was an absolute travesty of fossil fuel consumption made me scrutinize the food preservation process as a whole. How could I whittle down the energy inputs to the food we preserve? Here's what I came up with:
1. Can local products and minimize use of ingredients shipped from afar. It makes sense to start with foods that don't have inherently high carbon footprints before they arrive in our kitchens. Home canned food can only be as energy efficient as the ingredients that go into it. Obviously, finding a substitute for sugar grown a long way off won't be easy for most people. But we can opt to make lower-sugar jellies and jams. It'll be healthier for all of us while also lowering our food miles. Better still to can what we grow from seeds we start ourselves whenever possible. Growing your own from seed you save yourself makes you a low carbon footprint rock star.
2. Switch to re-usable canning lids. Tattler lids are re-usable indefinitely, and are made from plastic which does not leach BPA - an endocrine disruptor that mimics estrogen. BPA does no one any favors and is especially bad news for prepubescent children. Re-usable lids will entail a higher upfront cost that may not be feasible for everyone, though I believe it makes good sense both economically and in terms of energy consumption over the long term. Fossil fuels certainly go into the production of the Tattler re-usable lids and rings, but far more energy goes into the mining of metal for the single-use disposable lids, as well as the BPA-containing plastic lining on those lids. This is an investment worth working towards incrementally as your budget permits.
3. Prepare large batches so that you max out the capacity of your canner each time you fire it up. The more food you get out of one run through the canning process, the lower the energy usage per jar. Check the yields on canning recipes and try to scale up so that you fill your canner each time. Write margin notes on the recipes you use regarding the accuracy of the stated yields so that you can work more efficiently in the future. Also, make every effort to ensure that each jar seals successfully. Each jar that fails to seal and requires reprocessing doubles the energy consumption to preserve that food.
4. Bring the water needed to ambient temperature (or better) before you begin the canning process. In summer the water that comes out of our tap is roughly 59F/15C. The canning process takes that water to 212F/100C and beyond. That's exactly where the bulk of the fossil fuel is consumed - in heating water. A few hours' worth of foresight can shave off a significant chunk of those fossil fuel calories. All you need to do is fill the pots you'll need to use in the canning process well ahead of time. A water bath canner full of 59F water will warm up nicely when placed in the full August sun for several hours. Even if the pot only sits indoors on a cold stove for a few hours, our kitchen is very rarely less than 73F/23C during the summer months, and often much higher. If you're more ambitious and better equipped, you could use a camp shower bag to get the water really hot (easily 100F/33C). It may not seem like these small temperature differentials should make much difference, but heating the water is the major energy cost in the canning process. Temperature is a measure of energy, and saving energy is the name of the game here. I know planning ahead isn't the easiest thing in the thick of the summer gardening season, but in this case it's a free and relatively easy way to reduce your energy consumption.
5. As an obvious corollary to the above, use as little hot water as possible when you preserve food. Leave only the required amount of water in the canner when you're ready to process the filled jars. Extra water doesn't contribute anything to the process; it only consumes more energy for no purpose. If you're pressure canning, you can sterilize your jars in the canner with only a few inches of water and preheat the canner in the process. Just run the pressure canner with the lid on to the point that steam is being produced; you don't need to pressurize it. Leave the canner closed until you're ready to fill the jars.
6. If you happen to be blessed with a woodstove to heat your home, and are able to delay some of your canning to the cool months of the year, go for it. In doing so, you would avoid using any fossil fuel calories at all, and you'd be piggy-backing food preservation on the necessary heating of your home.
Got any other energy-saving tips to do with canning or food preservation? Please share in the comments!
Science, Blogging and Peaches
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