The Unsorted BBS Collection/thegreatunsorted.tar/thegreatunsorted/texts/txtfiles_misc/pot12

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                 -+- The Merry Pranksters from Menlo Park -+-
                               10.1990.01.01.12

                 Marijuana Grower's Handbook - part 12 of 33
                               by pH Imbalance
                               "Carbon Dioxide"

                                     from

                         Marijuana Grower's Handbook
                         [Indoor/Greenhouse Edition]
                                 Ed Rosenthal


   Carbon dioxide (CO2) is a gas which comprises about .03% (or 300 parts
per million, "PPM") of the atmosphere.  It is not dangerous.  it is one of
the basic raw materials (water is the other) required for photosynthesis.
The plant makes a sugar molecule using light for energy, CO2 which is pulled
out of the air, and water, which is pulled up from its roots.
   Scientists belive that early in the Earth's history the atmosphere
contained many times the amount of CO2 it does today.  Plants have never
lost their ability to process gas at these high rates.  In fact, with the
Earth's present atmosphere, plant growth is limited.
   When plants are growing in an enclosed area, there is a limited amount of
CO2 for them to use.  When the CO2 is used up, the plant's photosynthesis
stops.  Only as more CO2 is provided can the plant use light to continue the
process.  Adequate amounts of CO2 may be easily replaced in well-ventilated
areas, but increasing the amount of CO2 to .2% (2000 PPM) or 6 times the
amount usually found in the atmosphere, can increase growth rate by up to 5
times.  For this reason, many commercial nurseries provide a CO2 enriched
area for their plants.
   Luckily, CO2 can be supplied cheaply.  At the most organic level, there
are many metabolic processes that create CO2.  For example, organic gardeners
sometimes make compost in the greenhouse.  About 1/6 to 1/4 of the pile's
starting wet weight is converted to CO2 so that a 200 pound pile contributes
33-50 pounds of carbon to the gas.  Carbon makes up about 27% of the weight
and volume of the gas and oxygen makes up 73%, so that the total amount of
CO2 created is 122 to 185 pounds produced over a 30 day period.
   Brewers and vintners would do well to ferment their beverages in the
greenhouse.  Yeast eat the sugars contained in the fermentation mix,
released CO2 anf alcohol.  The yeast produce quite a bit of CO2, when they
are active.
   One grower living in a rural area has some rabbit hutches in his
greenhouse.  The rabbits use the oxygen produced by the plants, and in
return, release CO2 by breathing.  Another grower told me that he is
supplying his plants with CO2 by spraying them periodically with seltzer
(salt-free soda water), which is water with CO2 dissolved.  He claims to
double the plants' growth rate.  This method is a bit expensive when the
plants are large, but economical when they are small.
   A correspondent used the exhausts from his gas-fired water heater and
clothes dryer.  To make the area safe of toxic fumes that might be in the
exhaust, he built a manually operated shut-off valve so that the spent air
could be directed into the growing chamber or up a flue.  Before he entered
the room he sent any exhausts up the flue and turned on a ventilating fan
which drew air out of the room.
   Growers do not have to become brewers, rabbit farmers, or spray their
plants with Canada Dry.  There are several economical and convenient ways to
give the plants adequate amounts of CO2: using a CO2 generator, which burns
natural gas or kerosene, using a CO2 tank with regulator, or by evaporating
dry ice.
   To find out how much CO2 is needed to bring the growing area to the ideal
2000 PPM, multiply the cubic area of the growing room (length x width x
height) by .002.  The total represents the number of square feet of gas
required to reach optimum CO2 range.  For instance, a room 13' x 18' x 12'
contains 2808 cubic feet: 2808 x .002 equals 5.6 cubic feet of CO2 required.
The easiest way to supply the gas is to use a CO2 tank.  All the equipment
can be built from parts available at a welding suspply store or purchased
totally assembled from many growing supply companies.  Usually tanks come in
20 and 50 pound sizes, and can be bought or rented.  A tank which holds 50
pounds has a gross weight of 170 pounds when filled.

   A grow room of 500 cubic feet requires 1 cubic foot of CO2
   A grow room of 1000 cubic feet requires 2 cubic feet of CO2
   A grow room of 5000 cubic feet requires 10 cubic feet of CO2
   A grow room of 10,000 cubic feet requires 20 cubic feet of CO2

   To regulate dispersal of the gas, a combination flow meter/regulator is
required.  Together they regulate the flow between 10 and 50 cubic feet per
hour.  The regulator standardizes the pressure and regulates the number of
cubic feet released per hour.  A solenoid valve shuts the flow meter on and
off as regulated by a multicycle timer, so the valve can be turned on and
off several times each day.  If the growing room is small, a short-range
timer is needed.  Most timers are calibrated in 1/2 hour increments, but a
short-range timer keeps the valve open only a few minutes.
   To find out how long the valve should remain open, the numberof cubic
feet of gas required (in our example 5.6 feet) is divided by the flow rate.
For instance, if the flow rate is 10 cubic feet per hour, 5.6 divided by 10
= .56 hours or 3 minutes (.56 X 60 minutes = 33 minutes).  At 30 cubic feet
per hour, the number of minutes would be .56 divided by 30 X 60 minutes =
11.2 minutes.  [pH:Oh me oh my, there's another mistake!  The ".56" in the
latter equation should be 5.6, guess the people who did the book didn't
bother to check his math!]
   The gas should be replenished ever two hours in a warm, well-lit room
when the plants are over 3 feet high if there is no outside ventilation.
When the plants are smaller or in a moderately lit room, they do not use the
CO2 as fast.  With ventilation the gas should be replenished once an hour or
more frequently.  Some growers have a ventilation fan on a timer in
conjunction with the gas.  The fan goes off when the gas is injected into
the room.  A few minutes before the gas is injected into the room, the fan
starts and removes the old air.  The gas should be released above the plants
since the gas is heavier than air and sinks.  A good way to disperse the gas
is by using inexpensive "soaker hoses", sold in plant nurseries.  These
soaker hoses have tiny holes in them to let out the CO2.
   The CO2 tank is placed where it can be removed easily.  A hose is run
from the regulator unit (where the gas comes out) to the top of the garden.
CO2 is cooler and heavier than air and will flow downward, reaching the top
of the plants first.
   Dry ice is CO2 which has been cooled to -109 degrees, at which
temperature it becomes a solid.  It costs about the same as the gas in
tanks.  It usually comes in 30 pound blocks which evaporate at the rate of
about 7% a day when kept in a freezer.  At room temperatures, the gas
evaporates considerably faster, probably supplying much more CO2 than is
needed by the plants.  One grower worked at a packing plant where dry ice
was used.  Each day he took home a couple of pounds, which fit into his
lunch pail.  When he came home he put the dry ice in the grow room, where it
evaporated over the course of the day.
   Gas and kerosene generators work by burning hydrocarbons which release
heat and create CO2 and water.  Each pound of fuel burned produces about 3
pounds of CO2, 1.5 pounds of water and about 21,800 BTU's (British Thermal
Units) of heat.  Some gases and other fuels may have less energy (BTU's) per
pound.  The fuel's BTU rating is checked before making calculations.
   Nursery supply houses sell CO2 generators especially designed for
greenhouses, but household style kerosene or gas heaters are also suitable.
They need no vent.  The CO2 goes directly into the room's atmosphere.  Good
heaters burn cleanly and completely, leaving no residues, creating no carbon
monoxide (a colorless, odorless, poisonous gas).  Even so, it is a good idea
to shut the heater off and vent the room before entering the space.
   If a heater is not working correctly, most likely it burns the fuel
incompletely, creating an odor.  More expensive units have pilots and
timers; less expensive models must be adjusted manually.  Heaters with
polits can be modified to use a solenoid valve and timer.
   At room temperature, one pound of CO2 equals 8.7 cubic feet.  It takes
only 1/3 of a pound of kerosene (5.3 ounces) to make a pound of CO2.  To
calculate the amount of fuel required, the number of cubic feet of gas
desired is divided by 8.7 and multiplied by .33.  In our case, 5.6 cubic
feet divided by 8.7 times .33 equals .21 pounds of fuel.  To find out how
many ounces this is, multiple .21 times 16 (the number of ounces in a pound)
to arrive at a total of 3.3 ounces, a little less than half a cup (4
ounces).

   3/5ths ounce provides 1 cubic foot of CO2
   1.2 ounces produce 2 cubic feet of CO2
   3 ounces produce 5 cubic feet of CO2
   6 ounces produce 10 cubic feet of CO2

   To find out fuel usage, divide the number of BTU's produced by 21,800.
If a generator produces 12,000 BTU's an hour, it is using 12,000 divided by
21,800 or about .55 pounds of fuel per hour.  However only .21 pounds are
needed.  To calculate the number of minutes the generator should be on, the
amount of fuel needed is divided by the flow rate and multiplied by 60.  In
our case, .21 (amount of fuel needed) divided by .55 (flow rate) multiplied
by 60 equals 22.9 minutes.
   The CO2 required for at least one grow room was supplied using gas lamps.
The grower said that she thought it was a shame that the fuel was used only
for the CO2 and thought her plants would benefit from the additional light.
She originally had white gas lamps spaced evenly throughout the garden.  She
replaced them after the first crop with gas lamps all hooked up to a central
LP gas tank.  She only had to turn the unit on and light the lamps each day.
It shut itself off.  She claims the system worked very well.
   CO2 should be replenished every 3 hours during the light cycle, since it
is used up by the plants and leaks from the room into the general
atmosphere.  Well-ventilated rooms should be replenished more often.  It is
probably more effective to have a generator or tank releasing CO2 for longer
periods at slower rates than for shorter periods of time at higher rates.