Food

A mix of fresh raw vegetarian food.

The amount of Food for human beings that can be brought from Earth to Mars is limited, and the logistics of a continued food transport for the long term is expensive. By definition, an autonomous colony needs it's own food production. Reasons for this are cost reduction and the achievement of independence from Earth. Last but not least, locally produced food can be of higher quality and fresh, including a natural mix of vitamins and minerals.

Food on Mars will be produced in agricultural facilities that may be greenhouses, grow rooms or biological reactors, and probably a mix of all three.

Food requirements

• An average human requires about 2,7 kg of food per day, or 985 kg per year. A good target might be one tonne of food per year per colonist, to account for losses.
• Plants are composed of edible parts and non edible parts. The non edible portion is counted as biomass, and can be used for industrial production or recycled into the food production system. On average, excluding water, 50% of the plant is edible mass and the rest is biomass. The following table presents a suggested diet based on the Canadian Food Guide.

Food, canadian food guide	Weight of food (gram)	(kilo)Calorie/kg	(kilo)Calories per day
Fruit	500	500	250
Vegetables	750	300	225
Protein (meat and beans)	200	4 000	800
Dairy	750	420	315
Grains	240	2 100	504
Oils	40	5 000	200
Total	2 480	925	2 294

Notes:

• Calories as expressed in food guides and nutritional documents are actually kiloCalories. so the Calories of column 4 in this table are actually kiloCalories.
• One Kilocalorie = 4184 J. 2294 calories is 9 600 000 Joules, that is about 110 J/s of 110 Watts.

Food that can be brought from Earth

• Several varieties of dehydrated food.
• Food that contains large amounts of fat and carbohydrates, such as nuts and dried meats.
• Concentrated fruit juice.
• Lightweight, high energy foods with a long shelf-life.

Local Production Methods

• Vegetable can be grown in greenhouses, grow rooms or on green walls in order to close the carbon cycle.
• Proteins, fat and carbohydrates can be produced by a biotechnological factory also known as biological reactors.
• Animals, such as chicken or fish, may be raised in sections of greenhouses. Some can be fed with inedible plant parts, sometimes at reduced efficiency.
• It takes 2000 to 3000 liters of water to produce 1 kg of meat, it takes 100 liters of water to grow 1 kg of grain. Water may be a very valuable commodity on Mars, so the first generation of settlers might be vegetarian by necessity. This may be mitigated by water recycling.

• Growing insects and their larvae (e.g. flour worms or fly maggots) can provide valuable proteins and might consume mostly waste biomass‎. Pigs might be a more palatable alternative, of fish.
• Algae can produce large amount of food and oil. However, is is impossible to survive only on algae alone in the long term(reference needed).
• Some food (possibly genetically modified) may be grown in the Martian atmosphere. Results from the Phoenix lander indicate that some vegetables may be grown in caves safe from radiation(ref needed).
• The nuclear food cycle could produce food and oxygen using nuclear power.

Nutrition and Energy Calculations

Calorie calculation

	Unit	1 person	1000 persons
Human calorie intake	kilocalorie/day	2300	2300000
Days per year		365	365
Energy per year (E)	kiloca	839500	839,500,000
Yearly energy production (p)	kilocal/m2	4700	4700
Net area to feed humans (E/p)	m2	180	180,000

• The value of 180 m2 per person is the minimum area with high intensity lighting required to produce the minimum amount of food for one person.
• In other units, 10 000 m2 (one hectare) / 180 m2 = 55. So one hectare of intensive agriculture can feed up to 55 people, per year.
• Higher densities can be obtained using hydroponics and shelves or higher levels of lighting and optimized fertilization. This may not be sustainable in normal soil.
• Using animals to produce protein would increase the area required, while fish may combine habitats with plants for a null impact on total area.
• Higher levels of production are probably required for storage for Martian winters or sand storms, when food production might stop.
• There is a large uncertainty in these numbers as agriculture on Earth is not an exact science, and no crops have ever been grown on Mars.
• Additional surface allocations should be made for service and storage areas, circulation and maintenance of equipment required for food production. So the gross are might be 200-250 m2/person.

Food and crop energy and yields

The following table has been compiled from various sources. The values are high but remain bellow record yields and are usually for open field intensive agriculture unless otherwise noted. Most of the energy in plants is stored in the form of carbohydrates, that store about 4000 kilo-calories per kg.

On Mars, these crops could be grown year round, with supplemental artificial lighting, no weather, extra CO2 concentration and optimum irrigation and fertilization. Some Yields might then be significantly higher.

Food and crop yields

Food type		Tonnes /ha/y	kg /m2/y	kilocalorie /kg	kilocalorie /m2/y	Notes (it is not clear in the data if these areas include service areas, roads, preparation, temporary storage, etc.)
Apples, pears	Australia	65	6.5	571	3714	https://www.goodfruit.com/calculate-target-yield/
	Ontario	25	2.5	580	1450
Oranges, citrus	Florida	130	13	470	6110	https://www.hort.purdue.edu/newcrop/morton/orange.html#Yield
	Israel	50	5	470	2350	https://www.haifa-group.com/citrus-tree-fertilizer/crop-guide-growing-citrus-trees
Banana	Puerto Rico	70	7	1000	7000	https://www.hort.purdue.edu/newcrop/morton/banana.html#Yield
Strawberries	England	30	3	330	990	https://vegetablegrowersnews.com/article/tunnels-varieties-double-uk-berry-yields/
	California	90	9.0	330	2970	Hydroponic https://cals.arizona.edu/strawberry/Hydroponic_Strawberry_Information_Website/Costs.html
	Australia	150	15.0	330	4950	http://www.nuffieldinternational.org/rep_pdf/1450740021NickyMannFinalReport.pdf
Dwarf fruit trees	California	72	7.2
Potato	UK US	50 70	5.0 7	850	4250 5950	https://potatoes.ahdb.org.uk/sites/default/files/GB%20Potatoes%202016-2017.pdf These are for 1 crop per year, 120 days per crop. So it might be possible to reach 200 tonnes/ha for 3 crops per year in intensive agriculture. So 17 000 kilocalories/m2.
	Sweden	26	2.6
Sweet potato	california	27	2.7	860	2346	https://ucanr.edu/repository/fileaccess.cfm?article=54045&p=%20MKCWZJ
Tomatoes		150	15.0	180	2700
Water melon		36	3.6	300	1071
Cabbage		90	9.0	250	2250	https://www.kzndard.gov.za/images/Documents/Horticulture/Veg_prod/expected_yields.pdf
Beans		20	2.0	3470	6940	Hydroponic : https://uponics.com/hydroponics-yield/
watercress		25	2.5	110	275	https://ipmdata.ipmcenters.org/documents/cropprofiles/HIwatercress.pdf
Lettuce	hydroponic	400	40	150	6000
	US	40	4	150	600	Typical field grown
Alfafla (luzerne)	Jordan	180 40	18 4	230 290	4140 1160	Hydroponic : https://www.hindawi.com/journals/isrn/2012/924672/ Soil grown : https://wikifarmer.com/alfalfa-harvest-yield-per-acre/
canola		3	0.3	8840 ?	2652
Rice	China	17	1.7	1300	2210	http://www.xinhuanet.com//english/2017-10/16/c_136683786.htm
Wheat	US-Europe	10	1.0	3400	3400	Two crops per year, summer and winter. Often another crop (oats, maize, barley) and wheat
	US	150	15	3400	50 000	Maximum theoretical, hydroponic in lab conditions, Bugbee_Monje_LimitsCropProductivity_BioScience_1992.pdf
	US	80	8	3400	27 000	NASA This test cites the Bugbee study. Main difference is lower lighting levels. Doubling the lighting increases yields by about 80%.
	Canada	5.9
		6	0.6
Oats		4.3	0.4	3890	1673
		3.2
Barley		7	0.7	3540	2478
Soybean		3	0.3	4460	1338
Flax		1.3	0,13	5340	4100	For oil, seeds and linen. Calories is for seeds. Linen fiber not included in yield and is likely higher. Ref.: Alternative Agriculture, Iowa State university, Flax.
Hemp		1.3	0,1	5530	4240	For oil, seeds and hemp fiber. Calories is for seeds. Hemp fiber yields are about 12 tonnes/h or 1 tonne/h for combined seed/fiber crops. Ref.: Alberta dept. of agriculture, Canada.
	12	1.2	960	1152
Fodder Corn	Canada	50	5
Bamboo		4				For wood type products

• Many of the higher yield in this table are the result of multiple crops per year.
• These a edible food crop yields. The actual average biomass crop yields are at least double these. Potatoes are about 80% edible yield while most plants are between 35% and 50%.

Meat production

Meat production may someday be artificial, but may for some time come from animals. Vegetable alternatives exist for meat, and usually require less energy for their production. Therefore producing meat may be a question of demand and opportunity, rather than a question of need. Animals can produce meat from unused biomass, but the demand for other uses may be higher than the demand for meat production.

Energy in meat and meat products and dairy products.

Food type	kg /m2	kilocalorie /kg	kilocalorie /m2	Notes
Meat		5000
fat		9000
protein		4000
Salmon		2080
Tilapia		1290
chicken		2390
milk		420
Eggs		1550

Feed conversion ratio (FCR) is a measure of efficiency. It is the ratio between the mass of feed and the mass of product output. For dairy cows, for example, the output is milk, whereas in animals raised for meat (such as beef cows, pigs, chickens, and fish) the output is the flesh, that is, the body mass gained by the animal, represented either in the final mass of the animal or the mass of the dressed output (from Wikipedia). Feed conversion ratios also vary with the quality of the feed. A number of animals can eat vegetable products such as fibers and other vegetable parts that cannot be digested by humans. Therefore some of the food energy for animals will come form the inedible parts of food crops.

Feed conversion ratios

Livestock	FCR
Beef	4.5–7.5	calculated on live weight gain
Dairy
Pigs	3.8-4.5	About 1 for piglets, grows higher and higher with time
Sheep	4-6, 40	4-6 on grain, 40 on straw. This is an example of the difference between the production from high value food and the production from lower value biomass.
Poultry	1.6-2	A hen can lay up to 330 eggs per year. Maturation is about 40 days. Note than hens and many birds may require gravity for feeding/drinking, and transportation to Mars may be a problem.
Criquets	0,9-1.0	Seems unlikely to be below 1....
Fish	1-1.5	Tilapia is 1. Salmon about 1,3. Higher for fish to fish conversion, almost 4 in many piscicultures.
Rabbits	2.5-3

Artificial food

There is no existing complete food than might be considered artificial.

• See vitamins for the basic vitamin requirements that need to be obtained from food.
• Industrial proteins and carbohydrates are not produced directly from base chemicals but require biological reactors. There are a number of experiments being done to produce artificial food from the output of biological reactors, but these have not, to this time(2019), been proven to be more economical that naturally produced food.
• Beyond meat, a vegetable meat substitute, may be considered as artificial in some ways, but is more a modified food. Entirely vegetarian diets are possible.
• In-vitro meat is possible, but requires large amounts of energy for its production. Modified vegetables, such as Beyond Meat might produce a better substitute.

Energy requirements

Using hydroponics and greenhouses or vertical farms, an average yield of 60 tonnes per hectare per year should be possible (ref). This corresponds to a yield of 6 kg/m2/y. If the average illumination is 250 W/m2, then the average energy required for food production is:

• 250 W/m2 x 24 x 365 x 3600 / 6kg/m2 = 1300 MJ/kg
• 4000 kCal = 16.73 MJ. Then 1300/ 16.73 = 77. So it takes at least 77 times the energy in the food to produce the food, or an efficiency of about 1.3%, the rest of the energy goes into biomass and heat.

See also

• Food preservation