The Truth Behind Container Farm Yields
Over the past two or three years, we’ve seen many numbers listed for the production ability of container farms. Most of them have become unrealistic and in some cases totally absurd. The problem? These unrealistic numbers are adversely affecting the success of aspiring farmers.
Today we’re going to give a simple and realistic breakdown of actual production numbers from outdoor production (by the acre) and two types of container farms.
An acre is about 44,000 square feet.
A container farm is 400 square feet, or 1% of an acre.
Just to be clear, that means that to produce an acre of food (we’re going with a standard crop, lettuce) in 400 square feet, you’d have to multiply production by about one hundred times as much. To produce five acres of food in 400 square feet, you’d have to multiply production by five hundred times. If you skip ahead you’ll see that at best container farms could be expected to produce more like a quarter of an acre of produce, or twenty five times as much.
So how much CAN a container farm produce?
Let’s work through this… Arizona and California combined represent 96% of U.S. lettuce production with 2 harvests per year. We’re also going to be conservative and assume the numbers for leaf lettuce, which is lighter than head lettuce.
For leaf lettuce, most producers harvesting 12 tons/acre/harvest. At two harvests per year, that’s 24 tons/acre/year. (48,000 pounds) It’s slightly over one pound per square foot per year.
Shipping container farms with vertical technology use 256 ZipGrow Towers per container with 13 heads per Tower and 10.4 harvests per year (using 5 week turns). Depending on the size of the heads being grown (determined mostly by growing conditions and care), this could result in anywhere from 2.16 tons to 6.48 tons per year.
At 2 oz/head… 2.16 ton/year (this is the most realistic number)
This would equate to 9% of an acre, or 10x the production per square foot of outdoor production. Not bad. We don’t need to exaggerate it to have a great production number.
At 4 oz/head… 4.32 ton/year
This would equate to 18% of an acre, or 20x the production per square foot of outdoor production.
At 6 oz per head… 6.48 ton/year
This would equate to 27% acre, or 30x the production per square foot of outdoor production.
A lot of folks will say that vertical container farms don’t represent container farms well – that stacked is different. So let’s run through the numbers and see.
We’ll use a generic stacked container farm as an example, but we’ll be extra generous with the numbers, assuming a 14-foot width (rather than the 10-foot width of most shipping container farms) and a 2 foot access aisle. (Most would have a wider aisle.)
That leaves two 6-foot swaths of space on either side of the aisle for growing space. With a 6-inch trough, we could fit 12 troughs side by side. A normal plant spacing would leave 8 inches between each plant site. (That’s 2/3rds of a foot.)
We’re assuming 5 layers with 18 inches between layers. Also, not all of the footprint of the container is growing space. A conservative number leaves 70% of the footprint to be used for growing, while 30% is being used for storage, work tables, tanks, etc.
That’s 2520 plants growing in the layout at any given time. Using the same 10.4 turns per year, this is what we end up with:
At 2 oz heads… 1.6 ton/year
This would equate to 7% acre, or 7x the production per square foot of outdoor production.
At 4 oz heads… 3.25 ton/year
This would equate to 14% of an acre, or 14x the production per square foot of outdoor production.
At 6 oz heads… 4.9 ton/year
This would equate to 20% of an acre, or 20x the production per square foot of outdoor production.
As you can see, the production potential of container farms is good. The goal is not to say that indoor isn’t productive- it’s incredibly productive! 7 to 20 times the production is an incredible number. But 5 acres in 400 square feet? Not realistic.
If we’re honest about these numbers, then the industry as a whole can move forwards, and producers can be more successful as a result.
This is an important conversation to have. Please comment, ask questions, share, and add your own stories and concerns in the comments.
01:25 Numbers behind outdoor production
03:10 Outdoor production vs. vertical container production
09:05 Outdoor production vs. stacked container production
13:23 Truths about indoor farming
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