This is the first in a series of articles on what types of crops might be best suited for feeding a proposed human population attempting to colonize the planet Mars. The recent proposal by Elon Musk was for a colongy size eventually reaching one million persons.
GardeningPlaces.com offers some charts of crops: specifically, which crops produce the most protein, fat, carbs, or total kcal per unit of land and time (by crop cycle or year). Since agricultural resources will be extremely limited, the crops chosen to feed the population must make the most of time and land area.
The top crops which produce the most protein are mainly protein-concentrate or protein-isoalte crops, in which the plant crop must be processed to remove excess water, fiber, etc. in order to make the protein more bioavailable and practical. These include unusual proposed protein isolate sources such as mushroom, green tomato, spinach, pumpkin, and broccoli raab.
Mushroom has the advantage of not requiring sunlight, which is limited on Mars. Artificial sunlight for crops would use precious power resources. Being able to produce protein from mushrooms would offer the advantage of not using those limited resources (sunlight, power). Mushrooms also can possibly produce more protein per unit of land/time than any other crop, except duckweed. However, duckweed requires much more water than mushrooms.
The disadvantage of mushrooms as a source of protein concentrate is that many mushroom types are not a complete sources or protein. White button mushrooms have less than the ideal (IOM reference) amounts of essential amino acids. However, grown to maturity as the brown, Italian, or Crimini mushroom (all different names for the same thing), the amino acid profile is near complete. Then, only methionine+cysteine is less than ideal. But at 86% of ideal, no protein deficiency is likely from the protein concentrate.
Further research is needed. Would a mushroom protein concentrate contain any anti-nutritional factors? Can a variety be developed with a better essential amino acid profile or less anti-nutritional factors?
A system for making protein concentrate or isolate is absolutely necessary for a Mars colony (or other space colony making its own food). Otherwise, too much land/time resources are needed.
Duckweed also requires a better essential amino acid profile. The disadvantage of needed much water, even if that water is recycled, must be addressed. And the same analysis of anti-nutritional factors is necessary. Would duckweek concentrate contain too much fiber or chlorophyll? Would a protein isolate of any type risk losing too many of the nutrients of the protein crop?
Interestingly, it was recently discovered that duckweed can provide vitamin B-12, which is not usually found in plant crops. The only other vegan source of B-12 is “Nori”, which is purple or green laver, a seaweed.
If these crops cannot be used on a Mars colony for some reason, the next alternative would be a newly-created GMO crop that has the genes needed to produce B-12 added. Such a crop would be necessary for the long-term survival of any space colony, and animial-source foods are probably too difficult for the early stages of colonization (first few generations at least). Another issue is that, if a B-12 crop fails, or becomes impossible for the colony to produce, another source of B-12 will be needed. Thus, a GMO B-12 crop or two would be one of the necessarily components of the food production system, along with a protein concentrate or isolate system.
Pumpkin might be a good source of protein isolate, if the flesh and seeds are both used. The crop also provides provitamin A as beta-carotene, and alpha-carotene along with other nutrients. A protein concentrate product would maintain these nutrients, whereas an isolate would generally not.
Broccoli raab is a possible source of protein concentrate or isolate, as the crop is very quick growing, allowing many crop cycles per year. This factor increases the total protein produced per year above most other crops.
Similarly, green tomato can produce much protein because the crop need not be grown to maturity. Leaf crops like spinach, amaranth, and Swiss chard produce a large amount of protein due to their prolific production of leaves, which are relatively high in protein. Leaf protein concentrate has long been proposed as a protein source for the developing world. But its taste and color are less than palatable. An isolate might be a better choice. Or perhaps an interim product between a concentrate and a full isolate would be best.
More on this topic in future posts.