There are several technical reasons for growing plants in shipping containers. First and foremost it that the climate inside the shipping container can be precisely controlled for optimal growing conditions for whatever plants you wish to grow.
Of course, this is true of growing plants indoors in any type of building. The true leg up of shipping container farms over other type of indoor or vertical farming is that the shipping container can be moved and placed anywhere that has a electricity and water supply (and even those are not truly necessary if the container has solar cells on the roof and water could be delivered and stored near the container).
In a similar vein, mushrooms can also be grown in shipping containers, but they require different growing and propagation equipment than plants.
Since the growing conditions can be controlled in the shipping container, additional equipment is needed to actually control and monitor the growing conditions. Arguably the two most important conditions for growing plants in shipping containers are lighting, water, and nutrients.
Lighting is typically accomplished with LED light arrays or LED light bars. A full spectrum LED lamp is required, so a simple bulb that you would typically use in your home is not going to provide the correct light needed for plants growth. The reason is pretty technical – LEDs produce a variety of wavelengths of lights, and plants can only absorb certain wavelength – so home LEDs just don’t produce the right wavelengths for the plant to absorb.
Lighting is typically varied with the use of timers to set the amount of time that the lights are on and off. As you might expect, longer light cycles can cause the plants to grow more quickly and larger, since there is more energy pumped into the photosynthesizing system of the plants. Simply put, more light = more energy = more plant growth. There is obviously an upper limit to how much light you can pump into the leaves without burning the leaves or drying them out.
Though full spectrum LEDs are used over a typically home LED lightbulb, there are also other wavelength LEDs that are available for growing plants. Ultra Violet UV lamps can be used to darken leaves by causing the pants to produce more chlorophyll, and are typically used to provide the plant with more energy when flowering and fruiting.
Water can be tricky to optimize since it requires testing for pH on a regular basis with a pH meter, along with any trace minerals (with the use of a conductivity meter) or bacteria that could inhibit the plant’s growth. Water and nutrients are therefore closely linked, as the nutrient solution will change the pH and the conductivity of the water.
Other than water chemistry, there is also the mechanical side of water distribution. Most plants that are grown indoors use some type of hydroponic system that does not use dirt as a growing medium. The hydroponic system may use an inert growing medium like vermiculite or clay balls, but often for small plants there is not even a growing medium required – the root grow directly in air or water. Larger plants surely need a growing medium for root support.
All types of hydroponic systems, the water needs to be balanced with air so that the roots of the plant don’t rot. Air can be bubbled through the growing medium or through water with the use of air pumps and air stones to make sure the roots do not rot.
Typically when I think of a micro property for a shipping container farm, I think about the small plot of land that the shipping container sit on – similar in size to an RV pad. Maybe RV parks could be good spots for shipping container farms? The RV enthusiasts could walk to a fresh fruit and veggie spot right on premises – sounds like a good amenity, right?