Hydroponics

An example of vertically stacked hydroponics. A system like this would allow a person to be self-sustaining for vegetables in just a few square meters

Hydroponics is the practice of growing plants in nutrient-enriched water rather than soil.

Hydroponics is incredibly productive and requires little space. For example, Factor e Farm's experiments found that they could grow $1 of lettuce per square foot per week. And the Institutre of Simplified Hydroponics has found that they can grow 2kg of vegetables a day on 20m² of space [1]. This makes it particularly useful for urban settings.

Aquaponics is a kind of hydroponics that uses the water from fish tanks. This eliminates the need for an input of nutrients.