TOWARDS A SUSTAINABLE "GREENHOUSE" VEGETABLE FACTORY

Greenhouses are profligate users of energy. In temperate climates the energy is used to heat the house in the winter, and in tropical climates energy is used to keep the greenhouse cool.
By using a fully insulated light proof growing “factory’ it should be possible to re-circulate carbon dioxide and water and nutrients within the system and thus reduce energy requirements.
Existing artificial light sources produce too much heat, but light emitting diodes (LED’s) may provide a possible solution because of their low heat production characteristics.
Using LED’s, and a hydroponics (preferably aeroponics) crop production system, air can be re-circulated, and any excess heat and water vapour removed. CO₂ could be recycled by breaking down old plant debris in a digester while soluble components of the plant debris could be incorporated back into the nutrient solution.
The only major product leaving the closed circuit system will be the marketable crop, the carbon and water components of this may well be partially supplied by the respiration of the workers in the crop.
The energy source for the lights may come from solar panels on the roof of the building, or from the national power grid. Electrical energy can be efficiently converted into photosynthetically active radiation (PAR) and into plant material. The plants (if capable) could be photosynthesising for up to 24 hours per day and the marketable yield managed by the spectral balance. The level of CO₂ in the house could be up to 1500 ppm so it is postulated that yield of up to 4 times best current commercial yields could be achieved, ANYWHERE IN THE WORLD.