How much food can we grow?

How much food can our oceans produce? The vast majority of the food I find on my plate today comes from the land, whether it be wheat and flour, corn, maize, rice, beans, tomatoes, and lettuce, or animal products like dairy, beef, pork, and chicken. Being natural land dwellers, we rarely eat from the sea, except when we can catch a fish or pluck an oyster from the sand.

But it is worth remembering that 71% of the Earth’s surface is covered by water. If that is the case, then shouldn’t we be able to produce 71% of the Earth’s food in the oceans freeing up more land for real estate and other important uses? Well as it turns out, we can produce far more food than we need in the ocean. While on land you are limited to only a certain number of square feet, in the water sunlight penetrates as much as 600 feet down, freeing up all that space for farming. Imagine if you could stack rows of corn on top of each other until they were 600 feet high. While that example may block out too much light at higher layers to allow the lower layers of corn to grow, it gives you a good visual example of just how much space is available in an acre of ocean versus an acre of land for food production.

But it’s not just the amount of space that the ocean has available to it that gives it advantages in growing food, it is the kind of food that you can grow.

As a general rule, plants produce more calories for the amount of land used than animals. This is because plants are stationary. They do not expend energy moving around and eating, instead putting all of that energy into growth. They also don’t require expensive food. Instead, they feed themselves from the soil and the sun. On land, soybeans can produce 6.3 million calories per acre. Wheat can produce 6.4 million in good soil. Corn can produce 12.3 million (which is why it’s so popular to grow) and potatoes tip the scales while producing 18 million calories per acre. Rice is the staple food of Asia, and produces at least 11 million calories per acre per year, but can get higher in some regions. Even sunflower seeds can produce 4.3 million calories per acre.

Now compare the outputs of these plants with that of meat. Pork produces 3.5 million calories per acre, chicken 1.4 million, and beef 1.1 million. Meanwhile, Turkey only produces a measly 1 million calories.

Here is where the numbers start to get jaw-dropping. Salmon farms produce 760 million calories per acre. That is 43 times more than potatoes. Unlike potatoes, Salmon require feeding because they are animals. but unlike land animals, salmon don’t need to develop strong bones, they don’t need to fight against gravity to stand up and move around, and they are cold-blooded, and don’t need to expend energy to warm themselves. This means that salmon end up needing to consume 2 pounds of food for every 1 pound of edible meat they will grow. That is very efficient when you consider that chicken will require 3.6 pounds, pigs will require 8 pounds, and cows will require 22.5 pounds.

Surely Salmon have the numbers so far in their favor, that they ought to become the superfood that replaces all other foods right? There is one small drawback. Salmon are carnivores. This means that the food they must be fed is primarily other fish, which can be difficult to catch or expensive to raise indoors, since most fish that they eat, are also carnivores, it only becomes more expensive. If you go to the market today and look for salmon, you will find that it probably costs at least $8 a pound, making it one of the more expensive meats being sold. Far more expensive than pork which can sometimes be just $3 a pound.

But what if we want food to be cheaper, not just take up less surface area? After all, if so much of the ocean’s surface is being left unused, it doesn’t matter what we put there as long as it is producing cheap food to feed the poor.

New seaweed farming methods have recently been developed in which seaweed is attached to a rope that is suspended as much as 100 feet down under the surface of the water. Using this extremely low-cost method of farming seaweed it can be grown even in waters far too deep for it to ever touch the bottom, a great distance from shore. Seaweed in general is not a demanding crop to farm; after planting, farmers can simply leave it in the sea to grow until it is ready for harvest. It requires no fertilizers, pesticides, or other agrochemicals. A great deal can be grown in a short time: annual yields average 21 tons of dry weight per hectare. By comparison, about 12.1 tons of corn can be harvested per hectare in the highly productive fields of the United States.

At my local Walmart, I can go and buy a can of shucked, de-cobbed, washed and canned corn for about 89 cents per pound (you can try this yourself at your local grocery store and compare prices) so assuming that seaweed also reduces the need for most of the labor and machinery used in farming corn, let’s assume that we can cut that cost in half. That would mean that seaweed could be grown, processed, and sold anywhere in the world for only about 45 cents per pound, and still the areas growing it would be producing more in raw quantity than either corn or potatoes could by comparison.

In most cases, the process of growing seaweed helps their nearby environment. They suck up nitrogen and phosphorus from the oceans, thereby reducing acidification and eutrophication of water bodies. They also capture carbon dioxide as they grow, which makes them carbon-negative plants. By turning these chemicals into oxygen, they help to restore ocean dead spots.

Some large species of kelp grow even faster, with some farms producing as much as 25 tons per acre in only 5 months! Many of these large species of kelp can grow as much as 1 foot per day, meaning that instead of having only 1 or 2 harvests per year, harvests can be continual guaranteeing that consumers will have only the freshest ingredients at all times.

Not to mention, if we can get kelp farms consistently producing around 25 tons per acre every 5 months, we could feed the world’s population, cheaply, with an area of ocean only the size of Washington state. Now imagine how little land we would need if we could drop salmon prices as well!

Shrimp are more of a cold water animal, but they can sometimes be found in warmer waters as well, especially at lower depths (perhaps placing a shrimp farm beneath another farm like one for salmon would allow us to increase our calories per acre even more).

Regardless, let’s assume that we have decided we want to farm shrimp as well. You can stock shrimp at a rate of 12,000 – 16,000 per acre. Lower stocking density increases the size of the shrimp. However, it decreases the total poundage of yield. The cost of making a shrimp farm will depend on the size and production output. Approximately, a shrimp/ prawn farm of an area of 1 acre will require an investment of $10,000. That isn’t at all bad when you consider that shrimp farms produce on average about a 35% gross profit margin.

Mussels are one of the cheapest and easiest to grow shellfish in the world. They do not require any steroids, and retain most of the calories they are fed. Mussels feed on plankton and algae which can be grown cheaply and are found in every part of the ocean. Two experiments conducted in the Baltic Sea, on commonly sold Blue Mussels, reported production in two acres of the Baltic at an average of 130 tons each over a year and a half, and another experiment saw 66 tons of mussels grown after about 2 years. Although slow-growing, mussels are heavy hitters in terms of raw bulk production. The same can be roughly said for scallops and oysters. Oysters produce additional value when grown because they can create pearls, a natural gem produced by no other living thing.

There are over 30,000 different known types of algae, most of which thrive in salt water. Algae is a single-celled plant. They do not have stems, they do not have roots. They do not sprout leaves, and they do not grow trunks. Algae take the advantages the seaweed and kelp have in rapid growth and crank it up to eleven. By being even simpler and less complex than seaweed, algae can grow and reproduce even faster. The average farmed algae grow 20-30 times faster than land-based food crops. They are however usually more sensitive to pollutants and parasites than most other crops.

But now one Austrian company has developed a closed-loop system that can reliably produce 80 tons of algae per acre annually. Compare that again with the 12.1 tons we get from corn and you can see just how massive this figure is. What’s more is that the most common algae they have been using are called spirulina, mentioned in an earlier blog here. Spirulina is a flexible algae that can live in fresh or salt water, and in highly acidic environments, in addition, it is extremely high in nutrients and protein, even though it is a plant.

In theory, this new closed-loop system can be used with just about any type of algae, and that is important because some types of algae have never been farmed. Algae hold the title for some of the fastest reproducing things on the planet, with the current record holder being Synechococcus UTEX 2973 which doubles in total biomass 12 times per day. While this species of algae may not be an ideal food crop for other reasons, it is possible that superior types of edible algae are out there, and that they may be able to increase our food production rate even faster, bringing food costs down even further. It may be possible that in the future, no one will starve simply because of an overwhelming overabundance of cheap food.

And that brings us to our last point about algae, in some species, 80% of its biomass can be oil. The same kind of oil is used to make biofuel. With an oil content this high, it can quickly replace corn and ethanol as biofuels. While corn can only yield 60 gallons of biofuel per acre, algae can yield up to 10,000 gallons. No land plant can even come close.

After considering the numbers above, it is not only possible but likely that in the future the vast majority of food production will be done in the ocean, where yields are higher, costs are lower, and at least 95% of total available agricultural real estate is found. With this in mind, we can easily imagine a world where the next food revolution is led by seasteads.

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