Aeroponics

Aeroponics is a process for growing plants without soil or substantial amounts of another supporting medium. All nutrients are transmitted to the plants by a fine mist of nutrient solution applied directly to the roots. This aerosol can be created in a number of ways, usually an inexpensive aquarium pump.

Aeroponic growing has some advantages like disease free cultivation, higher crop yields, and more harvests. Theoretically there are some ecological benefits in comparison to other "lab" grow techniques like hydroculture, although that is probably set off by the use of a traditional lightbulb to achieve a self-heating setup. In the end I am just doing this because tiling the earth with my bare hands is not worthy of a real computer scientist.

Building the Bollbox

This growing system was made with lots of duct tape, aluminium foil and generally wholly inappropriate tools. Like movies by Uwe Boll, propably the worst director under the sun. Hence the name.

The cost for this system were around 40 Euros, although you can probably save some bucks by not building a green house around it. Sadly this is necessary as our hackerspace doesn't have any heating and most edible plants don't thrive in sub-zero conditions. A single 50W plant-growing lightbulb dissipates enough heat to keep the whole apparatus at around 20 degree Celsius (temperature graphs). For this build you'll need the following parts and tools:

• Net Cups:

  Those are available at any hardware store near the hydroculture stuff.

• Hydroton:

  Hydroton are expanded clay pellets. It holds moisture well but gives an excellent surface for roots to get hold. Also available at the hardware store. Buy enough to fill those net cups. Alternatively it should be fairly easy to nick some of it from plants in public areas.

• Mister:

  An ultrasonic mister as you've seen them in thousands of ugly indoor fountains. The smallest one (200ml evaporation per hour) should be sufficient as the mist builds up in closed quarters.

• Liquid fertilizer:

  Standard liquid fertilizer for hydroculture. Also available at the hardware store.

• Growing lamp:

  A run of the mill plant growing lamp. While it seems to be a specialized piece of technology, they are available from at least one major chain of hardware stores in Germany. If that isn't the case in your location, most grow shops stock them, although you should be prepared to pay a hefty premium.

  If temperatures are sufficient to support plant growth, a fluorescent lamp should be used. They are slightly more expensive but will use significantly less power. If heating is required a single incandescent lamp should be sufficient. It is a good idea to monitor temperatures anyway as overheating is an obvious fire hazard and detrimental to plant growth.

  NOTE: After the first batch of ruined plants an acquaintance noted that the light intensity might be too low. After measuring the luminosity it has become clear that any remotely usable plant growing system has to use fluorescent lamps. Apparently even sufficiently powerful incandescent bulbs would still output (apart from incredible amounts of heat) significant amounts of light in the red and infrared spectrum causing the plants to etiolate.

• Plastic tub:

  A simple, inexpensive plastic tub. Buy the cheapest one available, just keep two things in mind. Firstly, the tub should be deep enough that the ultrasonic mister generates enough mist and the net cups have enough clearance towards the nutrient solution. Secondly, the lid should be opaque, as light reaching the roots is not beneficial to plant growth. Otherwise use some aluminium foil to reflect light reaching the lid.

• Rockwool blocks:

  Roots aren't able to lodge to nothing so you'll need these blocks to get those seedlings going. I actually got those at the local head/grow shop. Using commercial mineral wool is not recommended as it is usually infused with at least fungicides.

• Hollow chamber plate (PMMA):

  A chambered plate as used in patio roofing etc. The chambers work just like double glazing, insulating against the cold outside. A whole plate is overkill, I used some scraps of a previous project. Again, completely unnecessary if the system is supposed to run in a heated environment.

Required tools are minimal. Just some duct tape and a cutter capable of putting a hole into the plastic tub lid.