Micro Environment Subsistence System (M.E.S.S.)
Micronutrients[]
There are other elements that while used in much smaller amounts, must nevertheless be present in some "significant" quantity. Essential trace elements include boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), sodium (Na), zinc (Zn), molybdenum (Mo), and nickel (Ni). Beneficial mineral elements include silicon (Si) and cobalt (Co), which have not been deemed essential for all plants but may be essential for some. Eliminate any one of these elements, and plants will display abnormalities of growth, deficiency symptoms, or may not reproduce normally.
Iron is necessary for many enzyme functions and as a catalyst for the synthesis of chlorophyll. It is essential for the young growing parts of plants. Deficiencies are pale leaf color of young leaves followed by yellowing of leaves and large veins. Iron is lost by leaching and is held in the lower portions of the soil structure. Under conditions of high pH (alkaline) iron is rendered unavailable to plants. When soils are alkaline, iron may be abundant but unavailable. Applications of an acid nutrient formula containing iron chelates, held in soluble form, should correct the problem.
Manganese is involved in enzyme activity for photosynthesis, respiration, and nitrogen metabolism. Deficiency in young leaves may show a network of green veins on a light green background similar to an iron deficiency. In the advanced stages the light green parts become white, and leaves are shed. Brownish, black, or grayish spots may appear next to the veins. In neutral or alkaline soils plants often show deficiency symptoms. In highly acid soils, manganese may be available to the extent that it results in toxicity.
Boron is necessary for cell wall formation, membrane integrity, calcium uptake and may aid in the translocation of sugars. Boron affects at least 16 functions in plants. These functions include flowering, pollen germination, fruiting, cell division, water relationships and the movement of hormones. Boron must be available throughout the life of the plant.It is not translocated and is easily leached from soils. Deficiencies kill terminal buds leaving a rosette effect on the plant. Leaves are thick, curled and brittle. Fruits, tubers and roots are discolored, cracked and flecked with brown spots.
Zinc is a component of enzymes or a functional cofactor of a large number of enzymes including auxins (plant growth hormones). It is essential tocarbohydrate metabolism, protein synthesis and internodal elongation (stem growth). Deficient plants have mottled leaves with irregular chlorotic areas. Zinc deficiency leads to iron deficiency causing similar symptoms. Deficiency occurs on eroded soils and is least available at a pH range of 5.5 - 7.0. Lowering the pH can render zinc more available to the point of toxicity.
Copper is concentrated in roots of plants and plays a part in nitrogen metabolism. It is a component of several enzymes and may be part of the enzyme systems that use carbohydrates and proteins. Deficiencies cause die back of the shoot tips, and terminal leaves develop brown spots. Copper is bound tightly in organic matter and may be deficient in highly organic soils. It is not readily lost from soil but may often be unavailable. Too much copper can cause toxicity.
Molybdenum is a structural component of the enzyme that reduces nitrates to ammonia. Without it, the synthesis of proteins is blocked and plant growth ceases. Root nodule (nitrogen fixing) bacteria also require it. Seeds may not form completely, and nitrogen deficiency may occur if plants are lacking molybdenum. Deficiency signs are pale green leaves with rolled or cupped margins.
Chlorine is involved in osmosis (movement of water or solutes in cells), the ionic balance necessary for plants to take up mineral elements and in photosynthesis. Deficiency symptoms include wilting, stubby roots, chlorosis (yellowing) and bronzing. Odors in some plants may be decreased. Chloride, the ionic form of chlorine used by plants, is usually found in soluble forms and is lost by leaching. Some plants may show signs of toxicity if levels are too high.
Nickel has just recently won the status as an essential trace element for plants according to the Agricultural Research Service Plant, Soil and Nutrition Laboratory in Ithaca, NY. It is required for the enzyme urease to break down urea to liberate the nitrogen into a usable form for plants. Nickel is required for iron absorption. Seeds need nickel in order to germinate. Plants grown without additional nickel will gradually reach a deficient level at about the time they mature and begin reproductive growth. If nickel is deficient plants may fail to produce viable seeds.
Sodium is involved in osmotic (water movement) and ionic balance in plants.
Cobalt is required for nitrogen fixation in legumes and in root nodules of nonlegumes. The demand for cobalt is much higher for nitrogen fixation than for ammonium nutrition. Deficient levels could result in nitrogen deficiency symptoms.
Silicon is found as a component of cell walls. Plants with supplies of soluble silicon produce stronger, tougher cell walls making them a mechanical barrier to piercing and sucking insects. This significantly enhances plant heat and drought tolerance. Foliar sprays of silicon have also shown benefits reducing populations of aphids on field crops. Tests have also found that silicon can be deposited by the plants at the site of infection by fungus to combat the penetration of the cell walls by the attacking fungus. Improved leaf erectness, stem strength and prevention or depression of iron and manganese toxicity have all been noted as effects from silicon. Silicon has not been determined essential for all plants but may be beneficial for many.
Micronutrients presence may be difficult to determine. Deliberate initial medium saturation to a pre-determined maximum "safe" level appears a reasonable consideration. In plants, and animals, there are aspects where a single atom of a particular element is essential to the creation or operation of a molecule, and therefore a particular function. No atom, no molecule, no function, no life. Absent high-tech chemistry, any particular missing micronutrient may be difficult to determine. A non-technology approach by observation of the effects on selected plants with known reactions . Rock dust, perhaps preferably dolomitic limestone, but even concrete dust, may contain enough atoms to help.
Whatever you take out of the growing medium, must be replaced. In growing to adulthood, a human will accumulate a collection of elements such as this:
Element Mass of element Element would Mass of element comprise a cube Kilograms this long on a side: oxygen 43 33.5 cm carbon 16 19.2 cm hydrogen 7 46.2 cm nitrogen 1.8 12.7 cm calcium 1 8.64 cm phosphorus 0.78 7.54 cm potassium 0.14 5.46 cm sulfur 0.14 4.07 cm sodium 0.1 4.69 cm chlorine 0.095 3.98 cm magnesium 0.019 2.22 cm iron 0.0042 8.1 mm fluorine 0.0026 1.20 cm zinc 0.0023 6.9 mm silicon 0.001 7.5 mm rubidium 0.00068 7.6 mm strontium 0.00032 5.0 mm bromine 0.00026 4.0 mm lead 0.00012 2.2 mm copper 0.00000072 2.0 mm aluminum 0.00000006 2.8 mm cadmium 0.00000005 1.8 mm cerium 0.00000004 1.7 mm barium 0.000000022 1.8 mm iodine 0.00000002 1.6 mm tin 0.00000002 1.5 mm titanium 0.00000002 1.6 mm boron 0.000000018 2.0 mm nickel 0.000000015 1.2 mm selenium 0.000000015 1.5 mm chromium 0.000000014 1.3 mm manganese 0.000000012 1.2 mm arsenic 0.000000007 1.1 mm lithium 0.000000007 2.4 mm cesium 0.000000006 1.5 mm mercury 0.000000006 0.8 mm germanium 0.000000005 1.0 mm molybdenum 0.000000005 0.8 mm cobalt 0.000000003 0.7 mm antimony 0.000000002 0.7 mm silver 0.000000002 0.6 mm niobium 1.5E-09 0.6 mm zirconium 0.000000001 0.54 mm lanthanium 8E-10 0.51 mm gallium 7E-10 0.49 mm tellurium 7E-10 0.48 mm yttrium 6E-10 0.51 mm bismuth 5E-10 0.37 mm thallium 5E-10 0.35 mm indium 4E-10 0.38 mm gold 2E-10 0.22 mm scandium 2E-10 0.41 mm tantalum 2E-10 0.23 mm vanadium 1.1E-10 0.26 mm thorium 1E-10 0.20 mm uranium 1E-10 0.17 mm samarium 5E-14 0.19 mm beryllium 3.6E-14 0.27 mm tungsten 2E-14 0.10 mm
If it’s not in the growing medium, it won’t be in the plant, or in you. Take “Popeye’s” favorite, spinach and the iron that is to make him strong. Organic grown / virgin soil spinach has around 1584 PPM iron. From commercial farms, it’s 19 PPM. About 1% of nature.
Lighting[]
Most plants cannot use the entire spectrum or intensity of light received on Earth. Limiting the light intensity and frequency to that at which each type of plant best grows reduces the heat load. Plants may also have specific lighting duration periods. Periods shorter than daylight can easily be simulated by shutters. Plants needing longer light periods than available daylight can often be "tricked" into continued processing though by low intensity artificial light, well below normal growing levels. In low light areas more useful light for the plants is gained where the growing area is mirrored, or reflecting in the right frequencies. Most plants need light in wavelengths of 400 to 700 nm, which I read is 45% of incoming light. They apparently do best in red and blue light. When growing vegetative matter, plants use primarily blue-violet light. When flowering they need red-orange end of the spectrum. As an aside, human eyes see green best, a color little used by plants, which reflect it and therefore they appear green to us. Terms often used to describe light are Lumen, Foot-Candle, Watt, and Lumens per Watt. Lumen is a particular amount of light energy. Envision a ton of feathers, it doesn't matter whether they fill a room, or are compressed into a brick, it's still a ton. Foot Candle measures light intensity. It is one lumen of light shining on one square foot. Watt is an electrical term. As we see with the difference in incandescent and fluorescent bulbs, watts of electricity IN, does not necessarily mean the same light OUT. It is a convenient means of comparison though of power in sunlight, in p/v panel conversion, and bulb conversion. Lumens per Watt is the efficiency of a bulb in converting electricity to useful light.
In some situations, such as climates with extreme exterior temperature challenges, it may be necessary to consider use of p/v panels to generate electricity, for lighting and plant growth in remote, strictly environmentally controlled chambers. (Of course, you need a lot of money to set this up.) Perpendicular direct daylight is around 10,000 lumens per square foot, for ease of estimating call it 100 watts if perfectly converted to electricity. In modest cloud cover, light intensity can drop to 1/10 or less. My reading shows that this may be the minimum power level for most photosynthesis. (Compare though to the Columbia University folks - Vertical Farm - who estimated a general value of 25 watt per meter square (2.32 watt foot square) for plant lighting. Plants convert certain frequencies of light into simple sugars. Too little light, and photosynthesis will not take place.
The "open" blue sky provides around 16% of useful light to plants of the intensity of direct sun. Too much light, and the plant overheats, transpires greatly increased water flow, and photosynthesis may not only shut down, but the plant may start to burn the sugars.
Sunlight is basically 10% U/V, 45% visible, 45% infrared (near/heat, and far/useable by plants). Most vegetables can use only make use of captured light up to a maximum of 2,500 - 5000 footcandles, and need this intensity for a period of about 6 hours daily, or about 15,000 to 30,000 foot candle hours of light. (Some vegetables, such as parsley, lettuce, chives, radishes and cabbage can do well with 4 hours.) (Intensity will vary depending on your latitude, time of year, atmospheric conditions, etc.)
Depending on your local conditions, you may be able to grow some plants in partial shadow, or your plants may benefit from some artificial reduction in light intensity. If read that for most plants, the "ideal" wavelength of light is red, with the plant maintained at an optimum temperature of 77 degrees F (25 C). If you intend to use artificial lighting to drive, or aid, your growing area, then bulb light production efficiency is a major issue.
A regular 100 watt household light bulb produces only around 400 lumens, or about 4 lumens per watt. If you used mirrors and focused it all on one square foot, it would be around 4% of open sunlight. Halogen bulbs produce about 20 lumens per watt, 100 watts being 20% of open sunlight.
Fluorescent bulbs, say high output, full-spectrum bulbs produce 68 lumens per watt, 100 watts being 60% of open sunlight.
Metal Halide Lamps are often used in hydroponic labs, they produce 80-120 lumens per watt, 100 watts being essentially the power of open sunlight. High Pressure Sodium lamps produce somewhere between 90 to 150 lumens per watt, or again the power of open sunlight. At these efficiency levels, perhaps frequency becomes more important. (See discussion of frequency applicable for the plants stage of life.) Electrical conversion is not the only consideration. In long-term sustainability, the lifespan of a product, and ability to replace it, becomes far more important than energy conversion efficiency. Another factor is AVOIDING loss of useful light frequency. Mentioned elsewhere, light absorbed and re-emitted comes out in a longer, often less useful frequency. Line your growing chamber with foil, or mirrors. Cited on the web for reflective efficiency is Foylon, (see also Aluma-Glo) at 97% reflectivity. LET THERE BE (A SELECTED SPECTRUM) OF SUNLIGHT A brief digression into a science summary, if you will bear with me. Visible light is just one small portion of the wavelength spectrum for electromagnetic energy. Below visible light is ultraviolet light, then X-rays. Above visible light is infrared (heat) then "radio" waves. From low to high (400 to 700) the colors go something like violet, blue, blue-green, green, yellow-green, yellow, orange, red. The longer the wavelength of light, the longer it takes for the photon’s energy to be imparted on whatever it strikes.
Think a quick punch (short wavelength & duration of impact) vs a slow push from the same arm (long wavelength long duration of impact). less "energy" a given photon has. If a particle absorbs a photon, it is either absorbed as heat, triggers a chemical reaction (causes an electron to move) or is re-emitted as a longer wavelength.
Chlorophyll A plants prefer blue 430 nm & red 66 nm Chlorophyll B plants prefer blue 460 nm & orange 640 nm Carotene prefers 400 nm to 500 nm.
High tech selective surfaces can provide a means to eliminate the unwanted frequencies. These items though tend to be expensive, fragile, and derived from finite fossil fuels. Consider a more “robust” and local hardware store approach.
I'm working at a latitude of around 32 degrees north - recalculate all angles for your latitude, with a goal of blocking direct summer heat, yet passing the maximum level of blue and red light. In winter my noon sun is 34.5 degrees up from true South, and 81.5 degrees in summer.
Envision thin strips of shiny red on the top, mirrored on the bottom. Have the slats runs true East / West, each tilted up 30 degrees. Set the North / South space between slats such that direct sunlight from 60 degrees or higher cannot pass.
The following two photographs are of the same "ceiling", located in Phoenix, Arizona. The first is looking at the ceiling toward the direction of summer morning sun, the slats blocking most summer noon sun. Shading in the picture disguises the true angles of the slats, which show better perhaps in the lower photo, which is looking toward the winter pre-noon position.
My proposal is a set of slats similar to this, but instead of all white, a combination of bright red and mirror.
In the winter most of the sun either directly passes or strikes the mirror and is reflected to the growing area. In the summer almost all direct sun strikes the red, which is then reflected down by the mirror. Around a 60 degree swath of diffuse blue sky is always available to the plants directly, or reflected down.
The below photo is essentially looking due east.
A simpler approach than the welded overlapping metal used at the Phoenix location would be two separate layers of slats, which could also allow them to be made adjustable if desired. Simpler yet is recognition that the east-west running slats are the priority. Simple short lifespan slats can be bright cloth and mylar held by a pattern of ropes.
If desired at the lower edge of the red side of the (fixed) slats a transparent substance (glass, plastic, ?) could be attached and extended perpendicular to the slat, making contact with the parallel mirror surface, or not, as desired. It would block most air flow thru the slats, and catch & channel most rain that fell on this roof.
Photosynthesis efficiency[]
Plants use light to rearrange molecules to store solar energy as chemical energy in the form of starch and glucose (sugar). The present globally photosynthetic atmospheric processing limit appears to be 2 x 1017 grams of C (200 billion tons) per year, which is about 10% of the atmospheric content. This carbon is being used by organisms and returned by respiration. We humans with our increasing numbers, burning ancient stored carbon, and depletion of plant mass are raising carbon levels. In plant cells water and carbon dioxide enter the cells, and impacted by the right frequency and intensity of light, sugar and oxygen leave the leaf. The chemical equation for this process is:
6CO2 + 12 H2O + 48 photons light → C6H12O6 + 6O2 + 6 H2O
6 molecules of carbon dioxide (6CO2) and 12 molecules of water (12 H2O) are consumed in the process, while glucose (C6H12O6), six molecules of oxygen (6O2), and six molecules of water (6 H2O) are produced.
Plants have limits on their rate of converting light to stored energy. Remember that plant biological processes continue at night, and that this uses up some of the energy accumulated in the presence of light. I've read that the overall theoretical efficiency of photosynthesis may be 4.5%. At 6 hour exposure, and if you could eat the entire plant, this would be an area 9 feet on a side. I've no idea what the crop would be, but you would probably be able to watch it grow…
If this "perfect" rate were potatoes, production would be (86 mt dry or 346 mt fresh) / ha). The real-world yield is (12 mt dry or 29 mt fresh) /ha, less then 1/10 of theoretical.
In various sources I find that overall photosynthesis efficiency in open nature and for typical food crops (corn,wheat,rice) is .1% to .2%. For 1/10% efficiency, each of us requires 21,600 sq. ft. /hours per day. With an average of 6 hours solar exposure per day this requires a fully productive food crop area of 3,600 sq. ft., 1,800 for 2/10% This is an area much less than the 1/4 acre per person typically available for manual farming (see information on farming in Cuba post-USSR), yet higher than the 1,000 sq. ft. information from Ecology Action. More (concentrated) sun is not the answer. C3 crops (wheat, barley rice, sugar beet, potatoes) all have FALLING conversion efficiency rates as light intensity goes above 20% of full sunlight.
Potato efficiency goes up to .4%, so with 6 hours exposure you need a minimum of 900 sq. ft. In various places, I've read the most "efficient" crop is claimed to be spirulina, with production of between 5 and 15 gram per sq. yd. per day. If each gram is around 5 calories, we get somewhere between 243 ft. sq. to 720 ft. sq. per person. At the upper level of production, is we're still assuming an average of 6 hours good sun exposure, we're looking at just under 2% efficiency on converting sunlight to food energy.
While I do not really expect to find a more efficient crop than algae, perhaps hydroponic or aeroponic methods can bring up the efficiency of more traditional foods. For those with a sweet tooth, Sugar cane (a C4 crop) comes in at a yearly average of 1%, requiring 360 sq. ft. with 6 hours sunlight, and with crops such as corn and sorghum can utilize higher sun intensity.
Reduced Light[]
Studies in Israel show increased growth of young citrus trees under reduced mid day light in a semi-arid climate, using up to 60% shade cloth. With too much light, some plants shut down photosynthesis, and physically "wilt" their leaves to minimize light exposure. Shade particularly benefits plants grown for their leaves.
The photosynthesis rate increase tracks increased intensity of direct light only from 0 to 50 watt per meter sq., then increased production tapers slightly up to 100 watt, and for many plants goes almost flat at 200 watt per meter sq.
I also read of plants benefiting from flickering light, vs constant. Perhaps a means to disperse sunlight as momentary sparkles would allow a greater growing area than the available solar window (welcome back the disco ball?).
Consider methods that rather than block a portion of the light, rather split the light into 2 or more separate beams. Route each beam via mirrors, lenses, fiber optic, etc, to separate, perhaps stacked growing areas, then diffuse each beam so that it illuminates an area of plants equal in area to the original light collection area. Do we accomplish the reduced sun that many plants need, while doubling or more the growing area?
At a minimum, line the growing area with reflective material, and perhaps you can "recycle" some of the light that otherwise would escape back to the sky, or just go to heat the surrounding area. A reflective northern wall may add as much as 12.5% "extra" light.
Lighting periods[]
Plants that genetically need specific lighting periods and be "tricked" in to acting as though there is a longer or shorter photo tropical period. Shorter is easy, you just need an opaque cover. The "trick" is making their genes think that daylight is longer. At the mid-darkness period, provide artificial light of 10 to 30 foot candle for times such as 3 minutes in every 30 minutes, 6 seconds in every minute.
A 40 watt florescent tube power is:
Inch Distance Ft. Candle
1 1000 2 950 3 750 4 650 5 560 6 400 7 430 8 370 9 360
10 350
Estimated Light Requirements Per Square Foot Plant Watt/Ft.Sq. Tomato 8.3 Eggplant 2.32 Peppers 2.32 Soybeans 2.32 Green Peas 2.32 Spinach 2.32 Carrots 2.32 Cucumbers 15.77 Wheat 2.32 Lettuce 2.5 Strawberries 7.06
Temperature control[]
Earth berming or burying a contained growing area would minimize the effect of external temperature variations, and provide greater pest protection. Earth sheltering combined with insulation should, if the intrusion of heat is avoided, provide for appropriate year round temperatures. Unless intended / used as human shelter for a CBR threat, the structure does not need to be airtight or constantly overpressured.
Root temperature in general should not exceed 82 degrees F, above which growth processes drop off, with 68 to 77 preferred. A root zone temperature of 105 degrees F is probably fatal to most plants. Leaves usually prefer 61 to 68 F.
Growing area[]
Readily available information suggests that 1,000 sq. ft. minimum of growing area is needed per person. With a typical modern diet, the upper fertilizing limit for humanure looks to be around 1600 ft. sq., with the limiting nutrient being potassium, and a potential "minimum" area of 600 ft. sq. based on a nitrogen concentration limit.
In the interest of pest control, I would not suggest a single large facility for a family. Instead, a number of separate units would permit growing a wider variety of plants, in differing conditions, concentrated with other plants needing similar conditions. It may also be simpler and cheaper to make a series of smaller units even per person, rather than a single 600 to 1,600 sq. ft. "greenhouse" for each person.
The commercially available concept and products that blend well with the MESS concept are those intended for "roof gardens", and their design factors. A bottom water proof membrane and roof penetration protection, a layer of drainage and aeration, a means to prevent soil penetrating the drainage, and compost above. Protect the top of the soil with another aeration barrier, then wind barrier above, which has penetrations for plantings. Weight is a major consideration in a roof garden or say gardening in containers on raised benches.
If your gardening media is enclosed and suspended above ground, then consider if you can walk under the garden. How far can you lean and reach if you are tending the garden? If you can walk under, and come up thru san a square 2’ on a side to tend by leaning, then you eliminate a lot of waster path space. If you can reach 3 foot (or a hair more) then think in terms of each 8’ x 8’ growing area having a 2’ x 2’ hole in the middle. Each 64 sq.ft. of surface area has 60 sq.ft. of growing space. If you “fudge” the math a bit (remember, the growing area can be from 1,000 to 1,600 sq. ft), you could have these units in a grid either 4 or 5 on a side. This is a A square with sides between 32’ and 40’. (Is there a commercially available bubble 8’ x 8’?) If a single test facility for your area is to have just plants on benches without walk-under capability, the above therefore would put a single test unit at around 8’ x 12”.
The bulk of my container tinkering was in "Wal-Mart" plastic tubs setting on cheap steel shelves. (Which of course rusted-out in a few short years.) "Rubbermaid" heavy duty shelving costs more, but in the 4th year of outdoor use shows no signs of decay.
The growing level. A mix of composted biomass and inert water holding substances. The depth will vary depending on the crop. The medium must hold surface tension water, yet drain well and allow air into the "pores" between particles.
Next down is a drain / filter level, I use fiberglass garden cloth, some of which has been in use for 5+ years (2007). Under this is 1 to 3 inches of "volcanic" rock, light but it holds the filter above the water and provides air space.
Under the rock I've been having success with another layer of fiberglass cloth as a wick, and keeping an upside down bottle, down thru a sleeve to keep the wick wet.
The greater the control & isolation from external influences, the better. But, your facility can be anything from a hedge rimmed garden to a miniature version of the Biosphere II facility, or the NASA CELESS. It's up to you and your resources. If you want to exclude excess heat (my situation most of the year) the only light to reach the garden should be that intensity and frequency needed by the plant, all else is waste heat. Insulate and protect the growing medium from light and moving air.
Humidity recovery[]
At the moment, short of a sealed greenhouse and running mechanical HVAC, I'm unclear on a method. (See Appropriate Technology - Dew Collection) I've read of fans blowing air from above the plants thru buried porous pipes, with the lower ground temperature leading to condensation, then the water draining from the pipes.
If the greenhouse IS sealed, then the largest challenge is getting heat OUT of the plant growing structure. Consider a bottle top up filled with water inside the greenhouse, another empty one outside top down, and the mouths of the bottles connected by hose. If the bottles and hose are solid enough, the temperature of evaporation can be “set” by controlled imposition of a vacuum on the unit. When the temperature of the inside bottle is greater than that of the outside bottle, water will evaporate, the vapor flow then condense, and the liquid water run back .
WATSON WICK WARNING CHECK WITH YOUR LOCAL HEALTH OFFICIALS A method of recycling human effluent rather directly to the growing medium is the Aerobic Pumice Wick presented by TOM WATSON. Black water drains thru a filter tank to hold solids for aerobic composting, allowing the liquid to drain to a bed/tank. In this container you want a lot of wicking material, with a lot of air. Mr. Watson suggests an 18" bed of pumice in a waterproof base, with a cover of around 6" of soil. The bottom 1/2" to 1" needs to be water-tight. Absent pumice, consider coarse sand. Without a watertight membrane, use the old approach of a layer of straw and manure to help anaerobic bacteria create a water impermeable "clogging" layer. The intent is to create an area to convert the smelly end product of human digestion, which scientifically can be seen as 0.16 g/l dissolved solids, 0.23 g/l suspended solids, 0.007 g/l phosphate, and 0.51 g/l nitrogen, into a nutrient righ garden bed. Plant roots access the bed use the nutrients and transpire the water. In the case of too much liquid, the wick acts as a filter and filtered water drains out of the exit pipe. Please ensure liquid does not rise to the compost level.
Perennial plants are best used because of their permanent roots. Lawns, shade trees, fruit trees, berries, grape arbors etc. are all suitable as there are no disease vectors transmitted via the roots. WARNING CHECK WITH YOUR LOCAL HEALTH OFFICIALS AIR STORAGE
If used as a CBR shelter, air storage is needed to avoid drastic swings in air composition. Consider the earth, with plant and animal activity taking place on the surface or in the first 100 feet or so, yet with miles of effective storage overhead. A potential methods to combine the garden with a large sealed volume of air is a rooftop garden over your sealed home.