The True Cost of Freeze Dried Food vs. Canning or Freezing
An article published a few years ago in Mother Jones Magazine cites a study that compared freeze-drying to canning and freezing. The article implied that the cost of freeze dried food is too expensive, energy-wise, to be a viable method of food storage.
The study mentioned in the article claims specific energy usage amounts for each of three methods of food preservation: freeze drying, canning, and wet-freezing.
Their conclusion states that freeze drying uses 1.2x and 1.7x more energy than canning or freezing, respectively.
However, as I note below, their conclusions are not based on sound logic.
The Mother Jones article states:
Freeze-drying is one of the most energy-intensive ways to preserve food, according to R. Paul Singh, a University of California-Davis food science and technology professor. Mountain House freeze-dries its food in 3,000-pound batches over a period of 18 to 20 hours. The final product weights about 900 pounds and takes about 2.4 million Btu of heat to produce – 1.2 times more energy than canning, and 1.7 times more energy than freezing.
Science Gone Awry … Or, Their Logic Is Illogical
Based on the above claim, canning the 3,000 pound batch of food would use 2 million Btu of energy (2.4M Btu for freeze-drying divided by their claim of 1.2 times as much as canning). Their 1.2 factor is not a huge increase – 20%. Significant, yes; huge, no.
But consider that now we need to transport the original 1.5 tons of food.
If the food is freeze-dried, that 1.5 tons (that’s 3000 pounds) now weighs only 900 pounds: less than one-third of its original weight! That is a significant – no, HUGE – reduction in shipping costs!
And consider that if those 3000 pounds of food were canned, it would weigh MORE than it did prior to processing! Canning (whether at-home pressure-canning or commercial canning in glass or metal containers) adds water to the food, and the can or jar itself adds weight. So shipping costs are much higher when compared to freeze-dried.
Also keep in mind that the shelf life of most canned foods is only a few years, compared to 20-30 years for freeze-dried food. Cans can be damaged, thus rendered useless; if improperly processed, the food inside the can will spoil.
The Mother Jones article goes on to state that freeze-drying uses 1.7 times the Btus of wet freezing. So my math concludes that wet-freezing the 3000 pounds of food uses only 1.4M Btus, compared to 2.4M Btus to freeze-dry it. That’s nearly twice the energy consumption. So the initial cost of freeze dried food is higher than the cost to wet-freeze it. Yep, they got me there, alright.
But Something Seems to Be Missing …
Their formula is missing an element. They neglected to say for how long a time they are freezing the food. One day? One week? A year? Twenty years?
Consequently, their statement has no meaning. That is not science, folks, that is data-manipulation combined with bad journalism.
In Debate Class (oh no, not school again!), we called the style of argument that MJ’s article used a Trap-Door. Their assertion has no anchor, no common element between its comparatives, so it bears no relevance to the discussion. It should be thoroughly discounted.
However, I think this could be fun …
So let’s carry on, with some necessary assumptions that they did not provide. We may see that the actual cost of freeze dried food is not as drastic as they wish us to believe.
They conveniently neglected to disclose a time span over which they’re freezing 1.5 tons of food. Yet they were able to provide a definitive energy usage … how’d they do that, since electricity usage is calculated over time???. We need to give a realistic time frame for their wet-freezing.
Yet that time frame will have no impact on our cost of freeze dried food, because it needs no refrigeration or freezing.
Hmmmm …. let me think a moment ….
Okay, I think I’ve got it! Let’s see if I can write this out succinctly.
Let’s Try Some Real Logic
We’ll use the amount of food in pounds (3000 lbs) divided by the average amount of food (in pounds) that one person eats per day to determine how long 3000 pounds of fresh food will last. That will be how long we need to freeze it. We will also assume that their total energy usage is spread over that time span.
Then, we’ll figure how long 900 pounds (the freeze-dried weight) of freeze-dried food will last for one person. And we’ll compare the energy usages of both.
The average American eats approximately 1900 lbs of food per year. So 3000 pounds would last approximately 1-1/2 years. So we now assume that they are expending 1.4M Btus every 1.5 years to freeze that food. (Obviously, it’s a bit less than that, as freezing costs will diminish as the food quantity decreases … but let’s not get technical).
Lindon Farms One-Year Food Storage Kit weighs 396 pounds (including the buckets’ tare weight). So 900 pounds of freeze-dried food will last one person approximately 2.25 years. And we used 2.4M Btus to freeze-dry it. On One Occasion.
For 2-1/4 years worth of food, we expended 2.4M Btus. For the same time period, to keep their food frozen, they’ll expend 2.1M Btus. Somehow, this doesn’t seem like the 1.7x factor they alluded to. Hmmm, I can only wonder if perhaps they had an agenda behind their statement …
Oh Yeah, I Almost Forgot …
Since we’re on a Survival and Preparedness Site, let’s not forget that there may be the remote possibility of a storm or a power outage.
3000 pounds of frozen food combined with an extended power outage adds up to a disaster in its own right!
And realistically, food does not fare well in the freezer much beyond a year or so, no matter how well packaged.
And just for more fun, consider toting that freezer with you when you need to bug out … go ahead, pick it up and stuff it in your backpack, you’re a tough guy, right?
And furthermore, even canned food is heavy and inconvenient to take along in an emergency or survival bug-out situation. Granted, it’s not quite as heavy as a freezer, and doesn’t need to be plugged in, but pouches or buckets of freeze dried food present a far easier and more convenient solution to taking food with you on the run.
My Conclusion …
Compared to canning or wet-freezing, the cost of freeze dried food is actually equal to or perhaps even less than those conventional methods. There is indeed true value in the somewhat higher initial expense of freeze drying, and its benefits far outweigh the higher cost.