How to acclerate hydroponic plant growth using every day materials and into the future
Here you will see my research and links for the future colonist, space farmer, long range explorer, or anyone who wants to try closed cycle farming at home.
by Bryce L. Meyer
First lets look at what plants do with molocules. The green cells of a plant use photosynthesis to take water and carbon dioxide and make sugars and other important molocules, then let go the oxygen to the air. In simpler terms, green parts use light to take the carbon from carbon dioxide (CO2) and add it to water and nutrients (like nitrogen and minerals) to make more plant parts, like leaves, stems, and fruits. The oxygen from carbon dioxide gets let go. See this drawing (click image to resize).
Next if you look at a whole plant, like a tomato plant. The plant is like a machine that takes water and nutrients from the roots, and moves them to the leaves. The plan needs bacteria around the roots, and cells in the roots, to grab the nutrients with oxygen. Root cells also need oxygen to live. So the roots need one kind of environment, in the soil, but the leaves and stems need an environment with lots of lights and carbon dioxide, like in the air. See this drawing (click image to resize).
As a result to make plants grow very fast, we can cover the top of the plant with clear cover, and push carbon dioxide to the plant, and add lots of light from sun, or grow lights (both above and in strips around the leafy part of the plant). You can get carbon dioxide from fermentation, as in wine or beer making, by putting yeast in a bottle, then adding sugars or starches. In a space habitat, the carbon dioxide comes from animals like people, or from breaking down fiber and wastes using a yeast-bacteria bioreactor. The roots sit in either soil or hydroponic media (like sponges, gravel, etc.) in a planter or bucket (or tube) and have bacteria around the roots. The roots need water and nutrients. The nutrients can be added from a plant food, or in a space habitat from broken down wastes (like urine, mixed in a tank, or from the yeast-bacteria bioreactor). The nutrients can also come from a fish/shrimp/mollusc tank by circulating the water from the tank through the roots. The oxygen will need to be supplied. One way is to have a hose into open air (on Earth) or by pumping in oxygen. One way to get oxygen is by hydrolysis from water (using electrcity to seperate hydrogen from the oxygen in water) or by concentrating oxygen from the air around the top part of the plant, or from an algae bioreactor. See the next diagram (click to resize).
Notes: Oxygen injection is really neccisary if the carbon dioxide above the roots is above 1.5%. At home, just have a loose bag hang over the planter, and let air from the house mix from the underside of the bag, and add the carbon dioxide in a tube at the top of the bag. In a terrarium (like this one, below,(click image to resize)) the carbon dioxide come in with air leaking around the edge of the plastic. So far growth with the simple bag over planter and carbon dioxde from fermentation improves growth around 20%-30% though still getting real data so that is just preliminary at best.
Home building:
For small plants: an old 2 liter plastic bottle works to hold the CO2. Chop off the bottom inch of the bottle. Find an indoor planting planter (or a plastic cup). Drill a hole in the top of the bottle cap (again 1/4 inch) and put another short section of fish tank tube and glue it in. Ideally the planter should be a bit smaller in diameter then the 2 liter bottle part to allow air to leak in and out. Put a small screw in the planter on each side to allow the bottle to rest on it. Fill The planter with coarse sand or small aquarium gravel. Put water in the planter just enough to wet the sand/gravel completely. To seed the sand/gravel with bacteria, dump a pinch of healthy outdoor dirt in the sand before wetting and mix in. Cover the sand/gravel with a couple of layers of wet paper towel almost to the edge of the planter, leaving a ring of sand exposed to the air around the edge. Poke a small hole (with a tooth pick) in the towel and add seeds half an inch down. Put the bottle over the top and set in a sunny spot.
You need to make a small yeast bioreactor to get CO2, which we make here. An old water bottle works great for this. Drill a quarter inch hole (if there is room) in the lid, then glue in a section of tube (around a foot and a half or so) so one end should just extend an inch into the bottle. Wrap paper around the bottle (yeast don't like light). Now add bread yeast (from grocery store), and whatever sugary thing is laying around with some water to about 3/4 fill the bottle. Alternatively if you have a carbouy with a batch of beer or wine fermenting away, link the tube to the one way valve on the carboy. The non attached end goes into a tube to tube connector (pet store or hardware store).
(OPTIONAL) BEFORE ADDING SAND or GRAVEL: Drill two 1/4 inch holes, one near the top ring, one around an inch lower. Use aquarium silicone to put in a small section (around 6 inches) of fish tank tube in each hole (glue around the middle of the tube so 2 inches hangs in) before you fill the planter with sand/gravel. The top tube hangingi nto the planter should be about half inch below the top of the sand/gravel. To make a water-er, put a hunk of tube into a hole drilled in the bottom of another water bottle or old cup and glue in so an inch sticks into the cup/bottle on the bottom. Cut out the top part of the bottle and flip it so it becomes a funnel. Put the bottle on a stand so that the bottom of the bottle is even with the bottom hole in the planter. Connect the tube from the waterer to the bottom tube from the planter (to water the plants). Take the top tube and tape it so that the top of the tube extends above the top of the planter. Make a line with a marker even with the top of the sand, make another about 1/8th inch below that. If there is water in this tube above the level of the lower mark, stop watering for a while and wait until the water drops.
Now for all that tube. Wait until the seeds sprout (about a week). Connect the tube connector from the yeast bioreactor to the tube from the bottle cap to feed the spouts CO2. All together looks like the diagram below (click image to enlarge).
Keep the waterer with water, and feed the yeast by adding sugar (soda, honey, etc.) every few days.
