United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
&ER&
Research and Development
EPA-600/S7-81-034 June 1981
Project Summary
Greenhouse Production of
All Bedding and Foliage
Plants with Industrial Heat
I. J. Crumbly
Potential beneficial use of industrial
waste-heat for the production of
bedding and foliage plants was evalu-
ated, using conventionally and warm
water heated greenhouses in Fort
Valley, Georgia. Each greenhouse was
a plastic covered quonset, 9.1 m x
21.9 m (30 ft x 72 ft). The research
greenhouse was heated and cooled
using simulated warm condenser
cooling water, while the control
greenhouse had conventional heating
and cooling during the 9-month test
program. During 1979, cultivars of 10
leading ornamental bedding plants, 8
species of foliage plants, and toma-
toes as bedding plants were studied
for growth rate, survivability, time of
flowering, and susceptibility to
disease in the humid greenhouses.
No statistically significant differ-
ence in growth rate for 7 of 10 orna-
mental and 2 of 8 foliage plants was
observed in the two greenhouses.
Tomatoes, coleus, and geraniums
grown in the conventional greenhouse
had statistically significant higher
growth rates. Syngonium podophyl-
lum and Philodendron pertussum
grown in the waste-heat research
greenhouse had statistically signifi-
cant higher growth rates. Ornamental
bedding plants grown in the conven-
tional greenhouse flowered approxi-
mately 7 days earlier. No significant
difference in survivability among
foliage plants and 8 of 10 ornamentals
was seen in either greenhouse.
Browallia and coleus survived better in
the conventional greenhouse. No
diseases were evident in either green-
house.
Heating and cooling of the waste-
heat research greenhouse was satis-
factory, despite the fin-tube heat
exchanger being oversized for the
available warm water flow. Environ-
mental control was adequate; at no
time was condensation observed on
the foliage of plants grown in either
greenhouse. Preliminary economics
indicate that industrial waste-heat can
be an attractive alternative to natural
gas and fuel oil for greenhouse
heating.
This Project Summary was develop-
ed by EPA's Industrial Environmental
Research Laboratory. Research Tri-
angle Park, NC, to announce key
findings of the research protect that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Water is used in the power plant
industry for cooling purposes, and
energy added to this water is described
as waste-heat. In the past, the normal
procedure has been todumpdischarged
cooling water coming from power plants
back into rivers, lakes, and cooling
ponds where the energy added is dis-
sipated. Most recently, to prevent
adverse environmental impacts of
waste-heat and to prevent large water
withdrawals associated with harm to
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aquatic life, the power plant industry
has been forced to build expensive
cooling towers.
If the means can be developed so that
this warmed water could be utilized to
heat and cool greenhouses and extend
the growing season of certain horti-
cultural and field crops, it would help
conserve energy while improving water
quality. Three other advantages are:
(1) a normal waste product would have
economic potential to the power plant,
(2) a reduction in the cost of crop pro-
duction could be passed on to the con-
sumer, and (3)the country would realize
a slight-to-moderate reduction in
thermal pollution depending on size,
kind of industry, and location.
The Environmental Protection
Agency estimates that the U.S. will
require approximately 750 x 109 liters
(200 x 109 gallons) of fresh water daily
to cool the condenser steam of power
plants required to produce the 1012 kilo-
watt hours needed annually by 1980.
Such water will be essentially free of
contaminants, and it will be discharged
at 29° to 49°C (85° to 120°F).
The annual quantity of waste-heat
presently available in the U.S. is approx-
imately 10 x 1015 joules (10 quad* Btu)
equivalent to 254 x 109 liters (1.6 x 109
barrels) of fuel oil. This represents an
annual amount of energy slightly less
than 20 percent of all the energy used
annually in 1971. However, this is a
low-grade (low temperature) form of
energy, and opportunities to use it
beneficially are limited. Within 30
years, the electrical power industry will
require the disposal of about 21 x 1015
joules (20 x 1012 Btu) of waste-heat per
day. One nuclear power plant having a
1,000 MW capacity can supply enough
waste-heat to accommodate 400 hec-
tares (1,000 acres) of conventional
greenhouses.
Greenhouses require large amounts
of energy to maintain adequate temper-
atures for crop production. The amount
of energy required will vary with loca-
tion, type of greenhouse, energy
conservation measures, and crop. In the
Tennessee Valley area, the energy
required for greenhouse crop produc-
tion may exceed 13.1 x 1012 joules/
hectare (5 x 109 Btu/acre) and in
Minnesota 19.3 x 1012 joules/hectare
(7.4 x 109 Btu/acre). The U.S. Depart-
ment of Agriculture reported in 1974
that nearly 109 million m2 (357 million
ft2) or 3,320 hectares (8,203 acres) were
*1 quad = 10'5
used for greenhouse space. By conserv-
ative estimates, the greenhouse
industry has grown 5 percent each year
since 1974 with a current estimate of
4,237 hectares (10,469 acres). The
average energy requirement for green-
houses in the U.S. can probably be
estimated by using the average Btu
requirement for greenhouse production
in Minnesota and the Tennessee Valley
area which is approximately 16.1 x 102
joules/hectare (6.2 x 109 Btu/acre).
Based on this assumption, the green-
house industry uses in excess of 66 x
1016 joules (64 x 10'2 Btu) annually. The
fuel equivalent of this amount of energy
could be beneficially used otherwise in
the U.S. by utilizing waste heat. In addi-
tion, if most of the greenhouses
throughout the world eventually change
to waste-heat, the energy saving will be
even more substantial.
Currently, 30 to 40 percent of the cost
of greenhouse crop production is used
for energy and is increasing, while
natural gas and fuel oil supplies are
becoming less available for greenhouse
heating. Since most greenhouses are
heated with natural gas, the present
cost for 67 x 1015 joules (64 x 10'2 Btu) at
$3.04/109 joules ($3.20/million Btu)
for natural gas exceeds $204 million
annually. The cost of 67x1015joules(64
x 1012 Btu) supplied by No. 2 fuel oil at
$6.45/109 joules ($6.80 million Btu)
would exceed $433 million. Using
waste-heat at $0.96/109 joules ($ 1.02/
million Btu), the cost of 67 x 10'5 joules
(64 x 1012 Btu) would be $61.4 million.
In addition to conserving fossil fuels, the
cost of energy could be reduced by 232
percent or $142.6 million over the use
of natural gas and $371 million or 605
percent over the use of No. 2 fuel oil if
waste-heat were used, while at the
same time environmental pollution
would be reduced through the reduced
combustion of fuel.
Conclusions
Cultivars of the following bedding
plant species were transplanted in late
January and in early February of 1979
in the conventional greenhouse and in
the waste-heat greenhouse: begonia,
browallia, coleus, geranium, impatiens,
marigold, pansy, petunia, salvia,
tomato, and verbena.
The data included in this report sug-
gest that the growth rate of the bedding
plant species grown in this study is not
adversely affected by the waste-heat
greenhouse environment.
With the exception of the browallia
and coleus, the survival rate for all other
species of bedding plants grown in the
waste-heat research greenhouse was
comparable to the survival rate of those
species grown in the conventional
greenhouse.
It was found that the plants grown in
the conventional greenhouse flowered
approximately 7 days earlier than those
grown in the waste-heat research
greenhouse. However, this may be sig-
nificant when considering the amount
of money saved in fuel cost.
The following species of foliage plants
were transplanted in each greenhouse
from June 12, 1979 through July 14,
1979: Ardisia humilis. Asparagus
meyerii. Begonia Caribbean mix,
Dizyotheca elegantissima, Hypoestes
sanguinolenta, Philodendron
pertussum, Schefflera compacta, and
Syngonum podophyllum.
All of the above species grown in the
waste-heat research greenhouse, with
the exception of Ardisia humilis,
showed a better growth rate than those
grown in the conventional greenhouse.
The growth of Syngonium podophyllum
(nephthytis green) and Philodendron,
pertussum was statistically better in the!
waste-heat research greenhouse than
in the conventional greenhouse.
The waste-heat research greenhouse
environment seems to be highly suited
for growing foliage plants. This is
probably brought about by the higher
relative humidity in the waste-heat
research greenhouse than in the con-
ventional greenhouse. Most foliage
plants grow better under high relative
humidity.
In regards to survival rate, there were
no statistically significant differences in
survival rate between any of the species
grown in the conventional greenhouse
and the waste-heat research green-
house. No diseases were found in either
greenhouse.
Economic
Because data were analyzed from
only one crop of bedding plants and one
crop of foliage plants, the economic
conclusions made are preliminary.
This study revealed that the waste-
heat greenhouse with a backup heating
system would initially cost $84,506 to
$90,605/acre or $208,730 to
$233,794/hectare more to construed
than the same size conventional green^
house. ,
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If the waste-heat can be supplied for
$0.96/109 joules ($1.02/million Btu)
as compared to $3.04/109 joules
($3.20/million Btu) and $6.45/109
joules ($6.80/million Btu) for natural
gas and No. 2 fuel oil, respectively, it
may result in a savings of $13,520/acre
or $33,394/hectare when compared to
natural gas and $35,685/acre or
$88,142/hectare when compared to
No. 2 fuel oil.
Considering the current increasing
price rates for natural gas and No. 2 fuel
oil, the number of years required to
break even for the cost of using waste-
heat to heat a greenhouse can probably
be reduced to 3 to 4 years relative to
heating with natural gas, and 1 to 2
years for heating with No. 2 fuel oil by
1985.
With reference to marketing and con-
sumer acceptance, customers did not
show any preference in buying plants
grown in the conventional greenhouse
over those grown in the waste-heat
research greenhouse. The quality of
plants grown in the waste-heat
research greenhouse was equal to the
quality of those grown in the conven-
tional greenhouse.
Engineering
The engineering performance of'the
waste-heat research greenhouse was
compared with the conventional green-
house in regards to heating, cooling,
and relative humidity.
In regards to maintaining heat, the
waste-heat research greenhouse was
able to maintain an average low night-
time temperature of 12.0°C (53.6°F)
over a 24-day period during the month
of February while using water heated to
21.8°C (71.2°F) with a flow rate of 109
liters/minute (24 gallons/minute). The
average low outside temperature for the
same period was 2.6°C (36.7°F).
Bedding plants grown in the waste-heat
research greenhouse did not suffer any
adverse effects when compared to
those grown in the conventional green-
house. The waste-heat research green-
house is quite capable of providing a
suitable wintertime temperature for the
species of bedding plants tested in this
project.
With reference to cooling, over a 4-
day period the waste-heat research
greenhouse in July was able to
maintain an average high daytime
temperature of 30.0°C (86.0°F) in com-
r parison to 29.4°C (85°F) maintained by
the conventional greenhouse. The
temperature of the entering effluent
water used to cool the waste-heat
research greenhouse during this period
was 43.1 °C (109.6°F). The average out-
side temperature for the same 4-day
period was 38.6°C (101.5°F). These
data indicate that warm effluent water
can be used effectively to cool green-
houses, if much of the heat associated
with the effluent water can be dissi-
pated from the greenhouse through an
attic before reaching the growing area.
For the most part, the relative humid-
ity averaged only a few percent higher in
the waste-heat research greenhouse
than it did in the conventional green-
house. At no time was condensation of
water vapor observed on the foliage of
plants grown in either greenhouse.
Recommendations
It is recommended that:
(1) The industry associated with the
production of thermal water
(waste-heat) and the greenhouse
industry apply the findings of this
project to help eliminate thermal
pollution of waterways while
benefitting both industries.
(2) A longer study period (4 to 5 years)
be given to the evaluation of the
crops observed in this study to
help verify the results stated
herein.
(3) A longer study period (4 to 5 years)
be given to further evaluate the
greenhouse design and control of
the greenhouse environment.
(4) Additional research be given to
finding those species of bedding
plants and foliage plants that are
best suited to the environment of a
waste-heat greenhouse.
(5) The growth response of woody
ornamentals be tested with
waste-heat.
(6) More research be given to eco-
nomic evaluation in comparing
waste-heat greenhouse crop pro-
duction with that of conventional
greenhouse crop production.
US. GOVERNMENT PWNTINO OFFICE. 1W1-757-OU/7136
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/. J. Crumbly is with Fort Valley State College, Fort Valley. GA 31030.
T. J. Brna is the EPA Project Officer (see below).
The complete report, entitled "Greenhouse Production of All Bedding and
Foliage Plants with Industrial Heat," (Order No. PB 81-178 279; Cost: $6.50,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
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Protection
Agency
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Official Business
Penalty for Private Use $300
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