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Consider a project like the Earthship. Supposing one would like to grow food (organic polyculture) indoors in such a habitat (i.e. in a green house). How many m² would be required to feed one person yearly?

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Is the person using this cultivation area as his sole source of nutrition? Are there any dietary restrictions? –  baka Jul 24 '11 at 12:36
    
Well let's assume the are is the primary source of nutrition (but other sources of food would be provided through market eg. salt). Let's assume too the cultivator has a predominantly vegetarian diet. –  Benjamin Jul 24 '11 at 12:45
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@Benjamin, is there a reason for the "indoor" (i.e. in a green house) part? Just being curious. –  Mike Perry Jul 25 '11 at 2:59
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@Mike: the idea is to protect crop from precipitation, collect, filter and re-use water, separate crop in separate compartments to prevent disease propagation and regulate temperature to produce crop from different climate eg. bananas in Europe, as well as produce all year round. –  Benjamin Jul 26 '11 at 8:28
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@Mike: I am working on development questions for my study and consider modes of development looking at household-level emancipation as the primary focus rather than industrialisation and market-integration. –  Benjamin Jul 26 '11 at 8:31

3 Answers 3

up vote 12 down vote accepted

update Answer has been edited after considering comments by bstpierre.

This is a great question, and I hope to learn more from some of the other answers and comments. I was unable to find good information that can be used to answer this question, but based on a few informed estimates, all assuming a vegetarian diet.

  1. 0.04 ha / 0.1 acre

    John Jeavons (see answer by bstpierre):

  2. 0.01 ha / 0.025 acre

    Eliot Coleman Perhaps a minimum estimate, also see comments

    In Elliot Coleman's book The New Organic Grower, the author claims that he can grow enough food for 100 people on 2.5 acres, equivalent to 0.025 acres / person, 1100 ft2 or 100 m2. Elsewhere, he claims to feed his household of two adults with a 40'x40' plot of land plus a 20'x40' greenhouse (1200 ft2).

    It is interesting that the author has 25 years of experience (at time of publication, 1995) cultivating 5 acres of land in Maine intensively using an eight year-rotation.

  3. 0.07 ha / 0.17 acre

    Meyers, N. 1999 The Next Green Revolution: Its Environmental Underpinnings. Current Science 76: 507-513

    The minimum amount of arable land required to sustainably support one person is 0.07 of a hectare. This assumes a largely vegetarian diet, no farmland degradation or water shortages, virtually no post- harvest waste, and farmers who know precisely when and how to plant, fertilize, irrigate, etc.

  4. 0.02 ha / 0.05 acre

    Silverstone et al. 2003. Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base. Advances in space research. 31 (1)

    A minimum estimate of the amount of land required to feed a crew on mars, but the only estimate here that is 100% indoors.


These estimates are minimum requirements, assume a vegetarian diet, and depend on highly skilled farming.

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In New Organic Grower, that statement was in the context of market gardening -- growing enough vegetables to satisfy the market demand of 100 people. I didn't take his statement to mean that he intended to completely satisfy their dietary needs. I'd have a hard time believing that you can fully meet an adult's dietary needs on just 1100 sq ft. –  bstpierre Jul 24 '11 at 19:45
    
@bstpierre I don't have my copy on hand to check but I am pretty sure that he was talking more about the dietary requirements than the market demands; "market demand" for organic food depends on the availability of grocery stores. If I recall correctly, his estimate was based on global surveys of subsistence farmers. Also, he apparently started the Mountain School farm, which provides most of the dietary needs of a small high school, although I can not find specific area / person numbers. –  David Jul 24 '11 at 19:56
    
On p21, it says "Two and a half acres is more than sufficient land to grow a year's worth of vegetables for 100 people." If you look at the Jeavons' numbers and assume that 40% will be put in calories+vegetables, you arrive at 1600 sq ft for vegs, which is close to Coleman's number; but this still leaves out grains, which are not as area-efficient. I think trying to survive on 1100 square will leave you wanting. –  bstpierre Jul 24 '11 at 21:41
    
@bstpierre point well taken. I have updated my answer to include additional estimates. –  David Jul 25 '11 at 13:26
    
Good answer after the edit, I like the extra sources. Another factor built into some of the estimates is length of growing season: Coleman uses indoor winter season extensions, Jeavons and Solomon are assuming outdoor with limited winter growing, and Silverstone is 100% indoor. –  bstpierre Jul 25 '11 at 14:34

I've seen from multiple sources that about 4000 sq ft per adult is about what is required, assuming a vegetarian diet.

Jeavons' book goes into some detail about how to plan your garden and your diet. Around p25 there are charts and explanation about choosing crops that are "Area- and Weight-Efficient". E.g. potatoes, leeks, garlic, parsnips. According to the plan in the book, 60% of the planted area will be high-carbon producing and calorie-producing (grains, sunflowers, nuts, grapes), 30% will be hi-cal, area-efficient (potatoes), and 10% will be "vegetables" (broccoli, lettuce, etc). Under this plan, a large portion of your calories are coming from food like potatoes.

Reading the few pages from Jeavons' book points out how intertwined the planning of both your diet and your crops must be. If you plant 4000 sq ft of corn, beans, and carrots but neglect to provide enough calories through potatoes, you may not have enough to eat.

Also critically important, but not covered much in either book, is the importance of being able to store your harvest past the growing season. Again, even if you do grow a year's worth of potatoes, you'll end up starving if everything is spoiled by the time January rolls around...


Update: a table in "The Permaculture Handbook" (Peter Bane) on p109 provides a breakdown for ~2700 calories per person per day (~1 million calories per person per year). It's not a vegan diet: the list includes milk, cheese, meat, eggs, and fish. It's based on the premise of a closed-loop fertility system so that manure, compost, etc is created on-farm instead of being imported. Bane's land figure comes to 14,500 sq ft (1/3 acre, 1350 m2).

An issue that Bane mentions is also worth considering: what are your labor and energy inputs? You can get more output from a given area of land by putting more labor into it. You can decrease labor by using energy, but if you're supposing a closed-loop system then you need more land to grow energy crops. Importing energy into your system doesn't eliminate the need for land to produce energy, it merely moves it. (And if your energy is from petroleum, you still haven't removed the need for land, you've only moved it back in time a couple of million years.)

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4000 ft² is app. 1220 m². It's a lot really. Does it depend on the method of cultivation? I often see crops grown at 0.5m distance from one another. Are there methods to save space? –  Benjamin Jul 24 '11 at 14:27
    
OK i see Solomon's book is proposing non-intensive culture (apparently wasting space) can produce better than its intensive, which also consumes more water and nutrients. –  Benjamin Jul 24 '11 at 14:39
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@Benjamin - That's what Solomon's book boils down to -- conserving water and soil at the expense of space. Jeavons makes the opposite tradeoff. Interestingly, both arrive at about the same 4000 sq ft / person figure. –  bstpierre Jul 24 '11 at 19:30

This is not a precise answer to your question, but Lolo Houbein in 'One Magic Square' claims that 1 sq metre (9 sq ft) can provide 1 salad meal per day for two adults (or smaller side salad for three) all year round, through the application of companion planting techniques.

If you extrapolate this idea (and eating only salad three times a day) 3-4 sq metres would be enough to completely supply the diet of two adults. Of course, stuff like pumpkin and watermelon cover huge areas so if you had only this small a space certain things would be excluded from your diet.

So, even though it's not a precise answer I hope it could be helpful for others reading the question, who are trying to grow all their salad/vegetable needs in one backyard, not necessarily grow enough to cover their entire diet.

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I should point out this probably wouldn't work indoor unless there was almost the same amount of light as you were getting outdoors. In an "earthship" presumably this is somehow possible though with skyplights and such. –  Lisa Jul 25 '11 at 23:23
    
I haven't read this book, but if "salad" just means leafy greens and maybe some small roots like radish and carrot, then I think you're going to end up hungry. –  bstpierre Jul 26 '11 at 1:54
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Just checked some reviews, one of which mentions that the book claims 1 sq yard can provide 10% of a person's diet. Extrapolating: 9 sq ft x 10 == 100% == 900 sq ft == 0.02 acre. A bit smaller than Coleman's number. Without seeing a breakdown of what's in the diet, I'm skeptical of those numbers. –  bstpierre Jul 26 '11 at 2:01
    
Or to make sense in metric terms, 10 square metres (I can't imagine what 900 sq ft looks like). As as to skepticism, agree, but then that is what the book is all about -- just how much you can grow as food in a small space if you put your mind to it. And that does relate pretty closely to the question asked. –  Lisa Jul 26 '11 at 4:57

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