World population is expected to grow to nine to ten billion people around 2050. And all this people need to be fed, but arable land scarce. Most land suitable land is already in use, so the challenge is obvious. One of the proposed solutions is urban vertical farming, i.e. growing crops in skyscrapers. In this post I will question whether vertical farming is actually a good idea.
The Wikipedia article on vertical farming mention several advantages of this mode of agriculture. First there is the preparation for the future argument: since there will be more people, we will need more land for agriculture and one way to do this by stacking up several layers of greenhouses. The second argument is about increased production, since indoor conditions are controlled we can produce crops all year round. Which means a multiplication of productivity with several factors. Related to this argument is the fact that indoor farming in a skyscraper will eliminate most weather related problems. Ordinary greenhouses, however do this already.
The subsequent argument mentioned is about conservation of resources, which means that by switching to vertical farming large pieces of land can be “recovered” and brought back to a more “natural” state. Also deforestation and desertification will be halted, and the need for fossil fuel powered plowing, planting and harvesting will be reduced, saving fossil fuels and reducing carbon dioxide emissions.
The next argument goes that by indoor agriculture less pesticides and the like are needed, therefore food will be healthier. The last argument I want to mention is the energy argument. The proponents argue that by employing methane digesters the farm will be able to produce some of its own power needs.
Well, its true that by using organic waste as an energy source, some reductions in external power supplies can be made. But I do not think that will be quite significant. From the second law of thermal dynamics we know that in a closed system the total energy is constant, it can only change from one form to another. If we subsequently extract energy from such system, the amount of contained energy in the system is lowered. What crops do is, energetically speaking, converting solar energy into chemical energy (stored in sugars and starch). Should we initially consider a vertical farm as a closed system, if we then remove some crops (for sale) and the farm will lose energy, which should be replenished. With only biogas from organic waste from the farm, we will still lose energy. What we need is an external supply of energy.
Since vertical farms will put layers of crops atop of each other, they have to replace sunlight with artificial light. Some research shows that with proper lighting will increase production in comparison with sunlight (this is due to the fact that plants will only absorb light of certain frequencies, and all other frequencies [notably green] will be reflected). And this lights have to be powered. A lot of energy is required, for heating the building, air circulation, pumping water and lights. Actually there is only one energy source suitable for powering vertical farms, and it is not solar, bio or wind power. The answer is probably not the one which is favoured by vertical farm proponents. Only nuclear power plants are able to provide a stable and reliable power supply for vertical argrarians.
Since the members of the Vertical Farm movement are eager to point out how environment friendly their ideas are, it is quite remarkable to see that they do not tell how they want to power their plans. They only mention energy recovery through bio methane gas and saving energy by reducing transportation. But this is not enough, we need a good plan about how to power such structures and how to finance it. History provides ample examples of nice plans, but which failed because the were not properly explained (the notorious Freedom ship is a classic).
The need for feeding nine billions people is out of the question, everyone acknowledges this. The actual question is how to do this. Vertical farms are one solution, but what are the alternatives? My favorite is the saltwater greenhouse. This concepts relies on the Sun to evaporate seawater, which is thereafter liquefied and used for the crops, but for more details you should check this link.
The most suitable places for saltwater greenhouses are large pieces of desert. The Sahara is on the first place of candidate locations. The world’s largest desert is sparsely populated and receives more solar energy than any other place on this planet. Further its location is strategic. Only a modestly small proportion of the Sahara is needed to generate enough energy for the entire world. What I mean to say is that unlike the vertical farm concept this plan is much more realistic, it is clear how it is powered. And unlike vertical farms, it can be done at small-scale, after which it can be scaled up. Therefore it is possible to test in practice before investing large sums of money into the project.
What about the energy cost of transporting food from the Sahara the rest of the world? Well, energy enough in Northern Africa, I would say. Just converting solar energy into some fuel. There are a number of methods to produce so-called synthetic fuels. Actually there are plans to build large solar farms in North Africa which should be linked to the European Superlink.
But there are other solutions for solving the global food shortage. First we should note that a lot of the world agricultural production are crops for feeding livestock, by consuming less or no meat we need less land to feed the world population. Secondly we have to understand that the food problem is actually more about distribution rather than production, in fact the total world food production is enough to feed everyone. But since there is unequal distribution of wealth in the world, some people do not get what they need. Perhaps we should solve this problem politically rather than technologically.
Vertical Farming in space
This post, however, is about vertical farming on Earth. But this concept might have more potential for space colonization, I will work this out in an upcoming post on this blog.