Agriculture 2.0: Is vertical farming the answer to feed humans on Earth?
By the time we build the settlements in Space and on Other planets like Mars, we would need to re-invent agriculture. It is already happening. We call it vertical indoor farming. Is this a future and could it replace our current crop field on Earth?
A significant part of the Earth is already covered by crops and more than 1 million km2 was newly cultivated during the last two decades. Check the map below. By the way, if you know where Ukraine is, you would see how it is important as the source of crops. So food security is at the risk due to the war. And we will need 5x more food than today in the next decades despite the unpredictable impact of global warming on agriculture.
Why will we need so much extra food?
- The number of humans living on Earth is growing fast. The world population reached 6 billion in 1999. And just recently 8 billion on November 15, 2022, according to the United Nations. It is estimated to reach 10 billion people in 2050. That makes an extra 25% of food to produce thanks to the population increase.
- People living in developed countries have double (100%) the energy food intake compared to less developed countries. That is also why there are not many gyms in Africa compared to Europe or US. With increasing standards of diet, more food would be consumed per capita.
- The structure of the diet would change. People will very likely eat more meat on average, which requires many times more area per produce kg. The statistics of the area required seems a bit odd. Lambs with 369 m2/kg need 40x more area than fish (farmed) with 8.4 m2/kg or wheat with 3.8 m2/kg. Poultry meat needs just 12.22 m2/kg. On the other hand, sheeps are bred in large open steep cold areas, where no crop would flourish. So they are not competing for the same land. Nevertheless, we could estimate say that we would need at least twice (100%) as many areas as today thanks to the change of diet.
Combining these factors all together, we will need at least 5 times more area (1.25 x 2 x 2 = 5) than we produce today. We will need to chop all remaining forests to get that extra space. Unless we improve by a lot the current methods and productivity of the yield per hectare.
How we could improve the yield production?
Firstly, we are continuously doing it. The yield has doubled during the last 70 years across all major crops [source]. The trend of the efficiency per ton produce per hectare is clearly here. This was achieved thanks to many small improvements, such as more irrigation, the use of efficient fertilizers, breeding of new variants of plants, and recently even genetically enhanced (modified) plants. This is how we keep up with the population growth except for some products like palm oil when the production increased 35 times.
So if we extrapolate the curve, we would get an extra 30% boost in the next two decades. This is a good start, but not sufficient to achieve 500% boost needed. A more radical change would be required to keep the size of our crop fields similar to today.
Most plants do have a growing season between 90 — 120 days. What about multiple production seasons every year using a greenhouse?
The Netherlands is a leader in efficient and sustainable agriculture — and the second-largest exporter of agricultural goods in the world. The controlled environment of very large greenhouses, mass scale, and use of a hydroponic system reduce the needed resources. The heating is done via geothermal energy to limit its impact on the environment while maximizing the yield. Some studies are estimating up to 13x higher yield per m2 than an open-field growth tomato in Spain.
A choice of tomatoes is not random and there are many reasons why they are commercially successful products. The plants are small and don’t need much space (less than 0.8 m2/kg). People are consuming them all year round and are relatively expensive.
Also, water makes up 90% of their mass. That is far less than fruits like bananas with 75% of the mass made of water. So you need 2.5x fewer materials to be grown for 1kg of tomato than 1 kg of bananas. This is a very important consideration for the next logical steps toward year-space agriculture. A couple of years ago, I did buy a Smart Garden for a few small plants like herbs to have something fresh and green in our kitchen. What about if we would scale that up? This is what vertical indoor farming is about.
Is Indoor vertical future of farming?
The idea of an indoor vertical factory-like farming using lamps illuminating plants 24/7 would even double the yield as the photosynthesis would be happening during day and night. We could have multi-store automated fields close to the cities providing food for everybody. The food will be fresh all year around minimizing the need for food transportation and refrigeration. Is the problem solved? Not so fast, let's do some math.
The speed of the plant's growth depends on how much light they are able to trap. The photosynthesis process uses as input CO2 from the air, water H2O, and energy from the light. The output is a module of C6H12O6 (Carbohydrates), the simplest sugar, which is storing the energy for all living organisms.
Our Sun provides plants with a lot of energy. It is more than 1kW per m2. This energy is virtually free of charge in the greenhouse. However, we will need to illuminate the plants intensively using electricity and lamps to achieve the same growth results. And we will need a lot of electric power. A lot. That is why special lamps with a fancy color and high PPFD (or photosynthetic photon flux density) were invented to boost overall efficiency.
How efficient is the artificial light source?
Solar energy is distributed across a wide light frequency spectrum (wavelength) — from ultraviolet to thermal infrared. The next diagram below shows irradiance in W/m2 for each part of the spectrum at sea level.
As you can see, visible light only makes up about 43% of the energy which passes through the atmosphere. And the photosynthetic molecules are only capturing part of the frequency spectrum (400–500 nm and 650–700 nm), which would be roughly 15% of the incoming light. By the way, chlorophyll gives plants their green color because it does not absorb the green wavelengths of visible light. Hence the green light is reflected into our eyes.
So we need lamps, which provide the light at the right wavelength to maximize the yield. This is where the PPFD parameter (or photosynthetic photon flux density) is used. It refers to the number of PAR (photosynthetically active radiation) photons that land on a given surface each second [µmol/m2/s]. Each lamp for plant illumination should have it defined with energy efficiency provided in µmol/Joul (e.g. Efficacy: 2.7 µmol/J].
Although those LED lights are much more efficient than traditional bulbs, the real efficiency of current LED light sources is about 30% to 40%. Most of the input power is still dispersed as heat. So even in the case, we would be able to convert all the energy into the right wavelength with a peak of 25% solar photovoltaic efficiency. Hence we would get to the best 10% of energy influx hitting the crop not considering the loss in battery and other systems. So the best-case scenario provides the same amount of energy for growth as direct sunlight going through the glass roof.
Hence you can have only one level of plants in the same area as a traditional greenhouse or crop field at the best. I actually switch-off my small smart garden Click And Grow pot to preserve some energy this year.
So unless you provide some cheap carbon-free energy source (nuclear fusion/abundance of wind power), indoor farming is not going to feed the World. Considering today's energy crisis, especially in Europe, we should be concerned about how to use our energy resources.
So what about the future of Agriculture?
There are areas and even countries, where indoor farming/highly advanced greenhouses could be not only economical but a necessity. One of the key advantages of indoor farming is major water usage reduction.
Up to 99% of the water can be saved compared to the traditional irrigation system. So hot, dry places with a lot of empty space (like deserts) for solar panels could be an ideal sweet spot. We could build future farms in areas, which are not considered suitable for agriculture using today's standards.
In areas with a lot of sun all year round, a combination of desalination plants with the drip irrigation system would provide an optimal solution. Instead of deforestation, we could build very large and smart greenhouses that would feed not only the local population but allow to export the products. We could farm grain to feed chicken, etc. A good and successful example in this field is Israel, where several farms were built in the middle of the desert. That approach could be replicated by other countries in North Africa like Egypt, etc.
So unless we successfully deploy new energy sources like nuclear fusion, indoor farming would be useful in space colonies and perhaps provide salads for restaurants in the city centers.
However, it will not provide a viable option for saving the planet from hunger. On the other hand, highly water-efficient greenhouses filling empty and deserted areas with a lot of sunlight all around the year could. With combination of fish farming and eventually cultured meat, the greenhouses will provide a much more economical and practical way how to feed mankind's needs in the near future.
