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Woody biomass production options for Florida

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Title:
Woody biomass production options for Florida
Series Title:
Bulletin - University of Florida Agricultural Experiment Station ; 856
Creator:
Rockwood, D. L.
Comer, C. W.
Dippon, D. R.
Huffman, J. B.
Place of Publication:
Gainesville, Fla.
Publisher:
Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida,
Publication Date:
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English

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Subjects / Keywords:
South Florida ( local )
Biomass ( jstor )
Plant roots ( jstor )
Wood ( jstor )

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University of Florida
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Woody Biomass Production Options
for Florida


D. L. Rockwood, C. W. Comer, D.
and J. B. Huffman


R. Dippon,


1 'J" U %,I. Ai

HUM+E LiB',,

JUL 10 986

LF.A.S. -Univ. of Florid

Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville


Bulletin 856


August 1985













WOODY BIOMASS PRODUCTION


OPTIONS FOR FLORIDA



D. L. Rockwood, C. W. Comer, D. R. Dippon, and J. B. Huffman















AUTHORS

Dr. Rockwood is Associate Professor, Dr. Comer is Assistant
Research Scientist, Dr. Dippon is Assistant Professor, and Dr.
Huffman is Professor in the Department of Forestry, Institute of
Food and Agricultural Sciences, University of Florida, Gaines-
ville FL 32611.


ACKNOWLEDGMENTS

We gratefully acknowledge the assistance of the Belle Glade
Agricultural Research and Education Center, IFAS; Buckeye
Cellulose Corporation; Lykes Brothers, Inc.; and the USDA Forest
Service through the provision of land, equipment, experimental
materials, and/or personnel. Research reported here is support-
ed by Oak Ridge National Laboratory under Subcontract No.
19X-09050C. These results are also derived from a project that
contributes to a cooperative program between the Institute of
Food and Agricultural Sciences of the University of Florida and
the Gas Research Institute entitled "Methane from Biomass and
Waste."

















Abstract.--Woody biomass is the predominant biomass resource in
Florida, and the potential for increasing wood availability is
high. A broad based examination of silvicultural factors--
species, spacing, site amendment, genetic variation--is combined
with economic, energetic, and environmental assessments to
determine the feasibility of silvicultural biomass farms as
alternative uses of forest and non-forest lands.

Additional Index Words.--Pinus, Eucalyptus, Casuarina,
Melaleuca, fuelwood.







CONTENTS

Page

Abstract ............................................. ..... ii

Introduction............................................ ... 1

Methodology................................ ........ ........ 1

Growth, Properties, and Management of Promising Species..... 3

Eucalyptus grandis.................................... 3

Slash pine.................................... ...... 8

Sand pine.................................... ..... 11

Other species ........................................ 14

Economics/Energetics ........................................ 15

Eucalyptus grandis................................... 16

Slash pine........................................ 19

Sand pine........................................... 19

Summary .......................................... 19

Statewide Potential....................................... 22

Land availability..................................... 23

Production estimates................................. 25

Institutional factors................................. 26

Commercial applications.............................. 26

Literature Cited........................................... 28

Metric to English Conversions............................. 29










INTRODUCTION

Wood constitutes 82% of all biomass in Florida (7). On
commercial forest land, net annual growth exceeds timber harvest
by 6.91 million m3. Additionally, some 0.4 million m3 of mill
byproducts and over 1.4 million m3 of wood and bark from
harvested stands are generated each year (2). In total,
sufficient woody biomass is available, without competing with
conventional timber markets, to increase wood's contribution to
the state's energy budget substantially from the 2% level of
1979.

Surplus wood can be a short-term alternative energy source;
longer-term production options for fuelwood and perhaps some
traditional timber products in Florida may be forest management
systems called silvicultural biomass farms (SBF). These differ
from conventional timber production systems in the following
ways:

1. Higher planting density, ranging from 5,000 to 40,000
trees/ha.
2. Shorter rotation length, perhaps three to 10 years.
3. Regeneration by coppicing or suckering following harvest.
4. More intensive site amendment and site preparation.
5. Hardwood species preferred over coniferous species.

A number of management options for SBF are being examined
statewide for promising species (Figure 1). Results from five
years of experimentation are presented here, along with prelimi-
nary recommendations.

METHODOLOGY

Fifteen native, naturalized, and exotic species (Table 1)
were included in initial field trials to evaluate management/
site amendments, genetic variation, planting density, genotype x
spacing interactions, and/or biomass productivity. Site amend-
ments were various fertilizer/sludge levels and were evaluated
in 100-tree square plots at 1 x 1 m spacing. Genetic tests
involved genotypes selected based on previous genetic evalua-
tion, phenotypic superiority, or similarity of source area to
Florida. Genetic plots were 25-tree square plots at 1 x 1 m
spacing.

Density tests included 100-tree plots of three spacings:
6,667 trees/ha (1 x 1.5 m), 10,000 trees/ha (1 x 1 m), and
20,000 trees/ha (1 x 0.5 m). Nelder's plots were also used to
evaluate density, as well as genotype and spacing by genotype
interactions. Planting densities equal to 43,300, 25,100,
14,600, 8,400, and 4,800 trees/ha were assessed.










INTRODUCTION

Wood constitutes 82% of all biomass in Florida (7). On
commercial forest land, net annual growth exceeds timber harvest
by 6.91 million m3. Additionally, some 0.4 million m3 of mill
byproducts and over 1.4 million m3 of wood and bark from
harvested stands are generated each year (2). In total,
sufficient woody biomass is available, without competing with
conventional timber markets, to increase wood's contribution to
the state's energy budget substantially from the 2% level of
1979.

Surplus wood can be a short-term alternative energy source;
longer-term production options for fuelwood and perhaps some
traditional timber products in Florida may be forest management
systems called silvicultural biomass farms (SBF). These differ
from conventional timber production systems in the following
ways:

1. Higher planting density, ranging from 5,000 to 40,000
trees/ha.
2. Shorter rotation length, perhaps three to 10 years.
3. Regeneration by coppicing or suckering following harvest.
4. More intensive site amendment and site preparation.
5. Hardwood species preferred over coniferous species.

A number of management options for SBF are being examined
statewide for promising species (Figure 1). Results from five
years of experimentation are presented here, along with prelimi-
nary recommendations.

METHODOLOGY

Fifteen native, naturalized, and exotic species (Table 1)
were included in initial field trials to evaluate management/
site amendments, genetic variation, planting density, genotype x
spacing interactions, and/or biomass productivity. Site amend-
ments were various fertilizer/sludge levels and were evaluated
in 100-tree square plots at 1 x 1 m spacing. Genetic tests
involved genotypes selected based on previous genetic evalua-
tion, phenotypic superiority, or similarity of source area to
Florida. Genetic plots were 25-tree square plots at 1 x 1 m
spacing.

Density tests included 100-tree plots of three spacings:
6,667 trees/ha (1 x 1.5 m), 10,000 trees/ha (1 x 1 m), and
20,000 trees/ha (1 x 0.5 m). Nelder's plots were also used to
evaluate density, as well as genotype and spacing by genotype
interactions. Planting densities equal to 43,300, 25,100,
14,600, 8,400, and 4,800 trees/ha were assessed.


































Figure 1. Location of woody biomass production studies.



The most common experimental layout used for the studies
was a randomized complete block design with three replications.
Some fertilizer and spacing tests were completely randomized
designs with three repetitions. Least squares analyses were
conducted for derivation of tree and stand predictive models.

Economic/energetic analyses for Eucalyptus grandis, slash
pine, and sand pine incorporated planting density, rotation
length, and the resulting growth rates. Desirable management
strategies and their sensitivity to assumptions of the economic/
energetic costs of inputs were developed. A break-even analysis
was used to examine the economic feasibility of SBFs in Florida.
This analysis was used to estimate a selling price per dry
equivalent ton (DTE) which would be necessary to obtain a
certain rate of return for the investor. Tax effects were not
considered in this analysis, since tax schedules and liabilities
vary by type of ownership and operational structure. Cost and
revenue estimates were assumed to increase at a rate equal to
the inflation. In addition a 4% and 8% percent rate of return
on investment before taxes and inflation formed a basis for the
analysis.







Table 1. Listing of species evaluated for woody biomass produc-
tion.


Common Name

European black
alder
Australian pine
Australian pine

Australian pine
Amplifolia
Grandis
Macarthurii
Nitens

Robusta
Tereticornis
Viminalis
Melaleuca
Sand pine
Slash pine

Cypress


Scientific Name


Alnus glutinosa (L.) Gaertn.
Casuarina cunninghamiana Miq.
Casuarina equisetifolia
L. ex J. R. & G. Forst.
Casuarina lauca Sieb. ex Spreng.
Eucalyptus amp ifolia Naudin.
Eucalyptus grandis Hill ex. Maid.
Eucalyptus macarthurii Deane&Maid.
Eucalyptus nitens (Deane & Maid.)
Maid.
Eucalyptus robusta Sm.
Eucalyptus tereticornis Sm.
Eucalyptus viminalis Labill.
Melaleuca quinquenervia(Cav.)Blake
Pinus clausa var. immuginata Ward
Pinus elliottii var. elliottii
Engelm.
Taxodium distichum (L.) Rich.


GROWTH, PROPERTIES, AND MANAGEMENT OF PROMISING SPECIES

Three current choices for SBFs have been utilized for
commercial forestry. In 1972, E. grandis became the focus of a
commercial planting program thai established 6,475 ha of pulp-
wood plantations in southern Florida (9, 10). Prohibitive
transportation costs and damaging freezes have prompted interest
in the species for alternative markets. Slash pine is the major
commercial pine species in Florida, and sand pine is grown
operationally on dry sites.


Eucalyptus grandis

Growth

Phosphorus addition prior to planting on "palmetto prairie"
sites (Prairie) significantly increases survival and growth
(Table 2). Nitrogen alone and sewage sludge applied nine months
after planting are much less effective. Optimal growth may be
achieved by applying 50 kg/ha P prior to planting with 160 kg/ha
N or 20 to 30 DTE/ha of sludge added after planting. However,
extra levels of N may not be economically efficient.


Status in
Florida


Exotic
Naturalized

Naturalized
Naturalized
Exotic
Exotic
Exotic

Exotic
Naturalized
Exotic
Exotic
Naturalized
Native

Native
Native






Table 2. Representative growth responses of Eucalyptus grandis
on prairie and muck soils.

Prairie


Site Amendment:
Amendment (kg/ha): 0
1.4-yr/Stem Biomass (DTE/ha) 0.4


Spacing:
Density (trees/ha):
2.4-yr Volume (m3/ha)
12-mo Coppice Stems/Stool


Genetics:

2.4-yr Volume (m3/ha)


Spacing:

18-mo DBH (cm)


Genetics:

18-mo DBH (cm)


Trees/H
10,00
1,60


43,300
74.8
2.0


300N/ Sludge
300 N 50 P 50 P 800 N/350 P
4.9 13.2 31.6 9.6


25,100
74.3
2.0


14,600
52.5
2.6


8,400
48.1
3.1


4,800
40.4
4.2


Range
Minimum Average Maximum
35.2 77.2 144.5


Muck

Months
la 6 12 18 24 30
10 2.5 4.2 5.6 6.2 6.8
)0 2.9 6.7 9.3 10.6 12.3


Range


Minimum
10,000 5.2
1,600 8.5


Average
5.6
9.3


Maximum
6.5
10.3


For rotations as short as 2.4 years, high planting density
(43,300 trees/ha) has the highest annual growth increments. The
43,300 trees/ha density achieved 25 m3/ha/yr and would likely
have peaked soon after 33 months, had an extreme freeze not
terminated the study. For longer rotations, the 25,000 trees/ha
density appeared to be the most productive for four growing
seasons.

Variation among progenies was evident at an early age.
Spacing influenced performance, as noted earlier, but had no
impact on relative progeny rankings. Apparently, E. grandis
genotypes will do well at any spacing. Progenies that were
superior through 1.4 years continued to perform well through 33
months in the Nelder's plots.

Certain progenies combine good growth and coppicing abili-
ty. The top 15 progenies averaged about 83% coppicing as
compared to 75% for all progenies. Four progenies in the
Genetics plots were still better, as 97% of the stools coppiced.






Coppice productivity may exceed seedling growth. Coppice
height of the top 15 families, 3.2 m at 12 months, approximated
that of 12-month-old seedlings and was uniform across planting
densities. Coppice stems/stool (Table 2) and coppice stem
diameter breast height (DBH) increased with lower density.
Neither the percent of stools coppicing nor coppice height
varied with planting density.

Growth on drained organic (Muck) soils, among the highest
yet reported for tree species, was some three times greater than
on Prairie soils. Planting density had obvious influence on
tree size (Table 2). DBH of trees at 1,600 trees/ha were
typically 50% greater than at 10,000 trees/ha. Tree heights
were similar at both densities through 24 months. Survival was
similar at the two densities through one year, but was consid-
erably less at 10,000 trees/ha after two years.

Differences among the six progenies were insignificant for
DBH and height at six months, but highly significant by 24
months. Differences in survival among progenies developed over
time. Progeny x density interactions were as minimal on Muck
soils as on Prairie soils.

For four progenies common to the two studies, six-month
height of trees on Muck soils nearly equalled that of 17-month-
old trees on Prairie soils. The considerable growth rate
differences between Prairie soils and Muck soils did not affect
relative performance of the progenies, suggesting that evalua-
tions of progenies for a variety of conditions may be accom-
plished at one site.

Coppicing was high on Prairie soils but much lower in Muck
soils. Coppicing rate following a December cut at Prairie soils
averaged 92% after 12 months. On Muck soils, coppicing was
completely nil after an August harvest, which typically results
in poor coppicing (10) and reached only 31% with a February
harvest, which is an optimum month for coppice. The better
coppicing families on Prairie soils did not provide a necessary
improvement in coppicing at Muck soils. Experience at both
Prairie soils and Muck soils supports the common contention that
good coppice performance can only be achieved with winter
harvests.

Properties

Twenty progenies sampled on Prairie soils differed signifi-
cantly for wood and bark specific gravity (SG) and moisture
content (MC) at 1.4 years (14, Table 3). Selection of the top
5% of parent trees would increase wood SG by 4% and reduce wood
MC by 7%. Gains in wood SG and MC from single tree selection
through vegetative propagation are 24% and -27%, respectively.
A non-significant relationship between wood SG and MC suggests
that simultaneous selection for high wood SG and low MC may be
possible.






Table 3. Representative biomass


Species-Age


Sand pine
-4 years
-6 years
-12 years

Slash pine
-8 years
-11 years

E. grandis
-1.4 years
-11 years

E. robusta
-11 years

Casuarina
-7.5 years

Melaleuca


Wood


Heat of
Combustion SG
(kj/kg) (g/cm3)


.36
19,900 .43
.44


19,624 .47
20,314 .53


18,941 .38
19,213 .48


Bark


Heat of
MC Combustion SG
CT 7 (kj/kg) (g/cm3)


MC
77


.31
20,930 .33


20,875 .26 70
.27 73


155 16,462 .26
108 14,683 .35


19,628 .53 107 18,074 .22 157


18,757 .66 80 18,213 .46 140


18,422 .51 90 25,791 .19 150


Wood qualities of coppice were


comparable to those of


seedlings. SG was extremely consistent for the coppice stems on
a given stool and across stools of the same progeny. MC, in
contrast, fluctuated widely even among coppice stems on the same
stool, perhaps a reflection of differences in vigor.

Wood and bark properties also varied among six progenies on
Muck soils. At 10,000 trees/ha, every progeny had higher wood
and bark MC and bark SG, and five of six progenies had apprecia-
bly less dense wood than at 1,600 trees/ha. In terms of
typically desirable biomass properties, such relationships would
favor lower planting densities for biomass plantations. Genetic
variation in wood SG and MC appears significant, and selection
to increase SG and to lower MC of wood is possible.

Management

Cultural practices to be employed for E. grandis SBF (Table
4) are more intensive than the methods used for conventional
Eucalyptus culture. Site preparation on Prairie soils should be
as practiced for pulpwood plantations except that beds should be
closely spaced; 2 m appears to be the limit with available
equipment. Phosphorous must be applied before bedding as ground


Wood


characteristics of five species.







rock phosphate. Nitrogen or sewage sTudge may be applied for
greater growth rates; however, economics and logistics will
dictate the suitability of these amendments. Spacing of trees
along a bed should also be as close as possible, approximately 1
m because of limitations of present tree planters. The summer
rainy season is the preferred planting time.

On agricultural Muck soils, use of conventional agricultur-
al practices for site preparation is sufficient. Phosphorus
application may be beneficial, and no bedding is required on
drained sites. Planting density should be as great as permitted
by the planting equipment, with a 1 x 1 m spacing viewed as a
desirable goal. A wider range of planting times may be possible
as long as some rain at planting time is likely to occur.
However, a more intensive form of site preparation (chopping
plus bedding) may reflect stand establishment operations likely
after multiple coppices.

Our growth model suggests that although the denser planting
(10,000 trees/ha) has lower survival, it consistently accumu-
lates more volume and dry weight than the lower density (Table
5). Maximum MAI of 23.8 DTE/ha/yr is obtained at 18 months for
the denser spacing. The less dense stand maximizes its MAI at
14.4 DTE/ha after 2.5 years.


Table 4. Management scenarios for Eucalyptus grandis SFBs
on muck and prairie soils.


Activity Muck


1. Prepare site:
-double chop
-burn
-bed
-fertilize


2. Plant site



3. Harvest stand


4. Harvest 1st coppice


5. Harvest 2nd coppice


May-June
Yes
No
Optional
50kg P/ha
(optional)


May-September
1,600-10,000
trees/ha

December-February
at 1.5-3 years

December-February
at age 1.5-3 years

May-June
at 1.5-3 years


Prairie

May-June
Yes
Yes
Yes
50kg P/ha,
100kg N/ha
(optional)

June-August
2,000-5,000
trees/ha

November-March
at 4-5 years

November-March
at age 4-5 years

May-June
at 4-5 years


6. Repeat cycle






Table 5. Eucalyptus grandis survival, volume, and dry weight
production by planting density through 42 months on
muck soils.

Planting Density
1,600 Trees/Ha 10,000 Trees/Ha
Stem Stem
Age Survival Volume Biomass Survival Volume Biomass
(%) (m3/ha7 (DTE/ha) [ T) (m3/ha) (DTE/ha7

6 94 1.2 0.7 94 8.7 4.7
12 92 14.8 8.1 91 39.6 21.5
18 89 34.1 18.5 87 65.7 35.7
24 86 51.8 28.1 81 84.6 45.9
30 81 66.5 36.1 74 98.4 53.5
36 76 78.5 42.7 66 108.9 59.2
42 69 88.4 48.1 56 117.1 63.6


Rotation lengths will differ depending on the site and
growing conditions. On Muck soils with high planting densities,
less than two years may be needed for harvest, and coppice
rotations may be even shorter. Time to harvest on Prairie soils
should be about four years at the planting densities achievable
within the bedding constraint.

Timing of the harvest/coppicing also has a major impact on
the productivity realized from the plantations. Early studies
have demonstrated much reduced coppicing following a harvest
during summer months, necessitating winter harvest operations.

Eucalyptus grandis is without peer among presently evalu-
ated species for productivity in south Florida. Growth rates
and survival achieved indicate that the species is ideally
suited to SBF (Figure 2). For more frost-frequent areas in
central Florida, E. grandis offers higher productivity than
other species but at the risk of frost damage and resulting
growth loss.

Slash Pine

Growth

Yields of slash pine at high planting densities are sur-
prisingly high for short rotations. Aerially seeded stands with
6,000 to 33,000 trees/ha from ages 6 to 10 years have produced
11 DTE/ha/year of stem wood (4); planted stands with densites of
approximately 25,000 trees/ha have yielded about 9.5 DTE/ha/year
(8). Actual productivity is dependent on planting high survi-
ving, fast-growing trees specifically selected for intensive
culture.





























Figure 2. Eighteen-month-old Eucalyptus grandis on muck soil
near Belle Glade at 10,000 trees per hectare.


Slash pine biomass yields may increase by as much as 85%
through use of improved trees (8). More competition-tolerant
progenies will result in much higher survival under close
spacing, and increments from increased biomass quantity per tree
and higher wood specific gravity will augment this increase.
Calculated gains, assuming use of selected parent trees in
existing or rogued seed orchards, suggest that emphasis on
biomass quantity traits would be more productive than on biomass
quality traits. Major impetus should apparently be given to
stem green biomass with additional gain to be expected from
selecting for wood specific gravity. Improvement in other
traits may arise indirectly due to correlations such as the 0.52
between wood specific gravity and heat value.

Progenies perform uniformly across planting density. The
consistent lack of density by progeny interaction for all traits
further suggests that good progenies will perform well over the
range of densities to be considered for intensive culture.

Slash pine responds well to fertilization on many sites
(Table 6). The level of response shown to N and P at high rates
and to a high amount of sewage sludge suggest a strong need for
fertilizing typical "flatwoods" sites. Response to fertilizers
on richer sites is uniformly lower, and at rates over 150 N and
50 P appears to be minor.






Table 6. Fifth-year response of slash pine and sand pine to
nitrogen (N) and phosphorus (P) fertilizers and
sewage sludge (S).
Height DBH Survival
Vs. Vs. Vs.
Treatment Mean Control Mean Control Mean Control
(kg/ha) (m) (%) (cm -7
---------------------------Slash Pine-----------------------
0 2.8 3.8 96
50 N/50 P-/ 2.6 -7 2.8 -26 89 -7
150 N/50 P-2 3.9 +39 4.2 +11 96 0
200 N/100 P2/ 4.2 +50 4.3 +13 95 -1
S(470 N/165 P)'/ 3.7 +32 4.7 +24 94 -2
S(945 N/335 P)-/ 5.1 +82 6.0 +59 91 -5
--------------------------- Sand Pine---------------------------
0 3.5 3.0 100
50 N/50 P1/ 3.6 +3 3.1 +3 100 0
150 N/50 P-2/ 3.6 +3 3.1 +3 99 -1
S(175 N/135 P)4/ 3.5 0 2.9 -3 100 0
S(340 N/265 P)/ 3.9 +11 3.6 +20 99 -1
1/Diammonium phosphate (21-21-0) applied six months after
planting.
-/Diammonium phosphate (21-21-0) and pelletized urea (45-0-0)
3/applied six months after planting.
-'Applied two months after planting.


Properties

Biomass properties of slash pine are affected by age and
planting density. Wood SG increases with age and reaches
approximately 0.48 g/cm3 by the anticipated rotation age of
eight years. Sufficient genetic variation for wood SG exists to
warrant selection for higher SG. MC decreases with age, thereby
favoring longer rotations if more desirable biomass properties
are required. Concentration of biomass in the stem also in-
creases with age. Extractives content, potentially beneficial
to increasing energy yields, varies considerably among trees and
appears to be subject to genetic selection. Chemical treatment
of trees prior to harvest may be a means to substantially
increase extractives yield (11).
Slash pine wood produced in short-rotation intensive
culture is less dense, contains more moisture, and has a lower
heat value (Table 3). Slash pine wood and bark properties vary
within the tree. From the base to the top of the stem of 8- to
11-year-old trees, wood MC increased, wood SG decreased, and
bark MC increased, but bark SG changed little.

Management

Slash pine planting sites should be well prepared, and wet
sites should be bedded (Table 7). The optimum fertilization
rate depends on site quality, but the addition of 150 kg/ha N






Table 7. Management scenarios for slash pine and sand pine
SBFs.

Activity Slash pine Sand pine

1. Prepare site
-chop Double Single
-burn Yes Yes
-bed Yes No
-fertilize 50 kg/ha of P No

2. Plant site December-February December-February
3,333-6,667 3,333-6,667
trees/ha trees/ha

3. Harvest stand All year All year
at 8 years at 15 years




and 50 kg/ha P will be necessary for most sites in north
Florida. Some sites may have high levels of soil N and P and
still show a growth response to fertilizer application. In
order to economically establish slash pine at the required
density on beds, an altered configuration resulting in trees
planted densely on two meter spaced beds appears necessary.
Progenies selected specifically for good performance under
intensive culture will increase yields.

Slash pine, the most widely planted species in Florida, has
potential for SBF on the "flatwoods" sites common to the north-
ern two-thirds of the state (Figure 3). High intensity cultural
practices need not differ from conventional pulpwood plantation
management other than in thoroughness of site preparation,
spacing of beds on wet sites, and level of fertilization on
nutrient-poor sites. Risk can also be reduced by incorporating
biomass production into the normal pulpwood rotations currently
in place. Management for multiple products will enhance manage-
ments options in the development of stands and for producing
fiber.


Sand Pine

Growth

Choctawhatchee sand pine, a species adapted to the exces-
sively dry, sandy sites common to much of western and central
Florida, does well at close spacing (12). Higher planting
densities are carried for longer rotations than for E. grandis
or slash pine in order to maximize productivity. Mortality due
to high competition levels appears to be minor. At close
spacing, rotations as short as 10 years may be possible.
























































Figure 3. Eight-year-old slash pine on a "flatwoods" site near
Gainesville at close spacing.



12







Yields can be increased by genetic selection within
Choctawhatchee sand pine (8). Calculated gains, assuming use of
superior clones in existing or rogued seed orchards, identified
that emphasis on biomass quantity properties would be more
productive. Sand pine stem green biomass yields may be in-
creased by more than 30%, while further selection for wood
specific gravity could enhance dry weight productivity. Due to
strong correlations, such as 0.74 between wood SG and percent
stem biomass, gains may accrue indirectly for other properties
as well. The 6-year-old sand pine progenies assessed for stem
wood energy content, for example, demonstrated accumulative
differentials due to stem volume, wood SG, and wood heat value
factors. The yield of improved sand pine was 55% greater than
unselected trees. This increase was partitioned to 1) some 20%
due to a higher survival rate of selected progenies and 2) about
35% accruing from greater biomass quantity and better biomass
quality of the improved trees.

Fertilization had little influence on sand pine growth
through five years (Table 6). Only high rates of sewage sludge
had an appreciable impact on growth. Nitrogen and phosphorous
fertilizers have been observed to increase total volume yields
up to 71% in 7-year-old Choctawhatchee sand pine (3). However,
until meaningful responses are seen and maximum treatments
identified in intensive conditions, we recommend that fertilizer
not be used.

Properties

Sand pine biomass properties differ somewhat from those of
other species (Table 3). Wood SG is lower, and wood MC is
higher. Bark properties are neither better or worse than other
species on the average. Heat of combustion of wood, and bark is
comparable to other species, while that of branches and foliage
is slightly greater than others. On a whole tree volume basis,
sand pine biomass would be least desirable of the 15 species
studied for energy yield.

The biomass characteristics and properties of sand pine are
influenced by tree age and planting density. The scrubby
tendency of the species is considerably improved by close
spacing and rotations beyond six years, as the quantity and
proportion of biomass in the stem increases appreciably. Wood
SG and MC do not appear to be influenced by planting density,
but do improve with age (Table 3). Wood SG increases with age,
and wood MC decreases. These traits appear to be under moderate
genetic control. Heat values of wood and bark are typical of
the pines, but are not subject to change genetically. Sand pine
wood usually is low in extractives, although a few trees with
extractives content exceeding 1% have been observed.

Within-tree variation for properties of 5- and 6-year-old
sand pine wood and bark was generally consistent. MC of wood
and bark increased with height, while SG of wood and bark






decreased up the stem. Wood ash content was similar throughout
the stem of 6-year-old trees; wood heat value increased with
stem height after an initial drop from the basal reading.

Within age groups, sand pine progeny differences were
generally greater for biomass quantity properties than for
biomass quality properties. Progeny differences in biomass
quantity properties and percent green stem biomass were found
consistently in 4- and 6-year-old trees. Differences among
progenies were observed in certain biomass quality properties,
but the amount of variation was low. Progeny differences for
wood SG, wood MC, and wood heat value were notable.

Management

Management practices for sand pine are well-known for
commercial pulpwood production and need only slight modifica-
tion, namely higher planting density, for SBFs (Table 7).
Fertilization seems unnecessary. Genetically improved planting
stock should be utilized in order to achieve high survival and
growth. Rotation length is uncertain but appears to be beyond
10 years.

The vegetation on a sand pine site must be reduced.
Sufficient site preparation consists of burning followed by
chopping or windrowing. Properly timed single chopping is
adequate on sites with low amounts of vegetation. Double
chopping, again with proper timing, may be necessary on heavily
vegetated sites. Weed control after the initial site prepara-
tion is not required.

In the short-term, Choctawhatchee sand pine is the best
choice for SBF on the sandhills of Florida and elsewhere in the
Southeast (Figure 4). No other species guarantees the survival
necessary for high productivity. Growth rates, while not as
high as those of other species on better sites, surpass what is
currently possible with others on these poor sites.

Other Species

Casuarina

The three species of Australian pines that are naturalized
in Florida have many desired characteristics. All have very
high wood SG (Table 3) and fix nitrogen through association with
the symbiont Frankia spp. Root suckering by C. glauca is
prolific, and C. cunninghamiana also suckers. In Florida, C.
cunninghamiana and C. equisetifolia produce copious supplies of
seed. Growth of trees of natural origin is rapid, and the yield
of stands can be exceptional, with a 7.5-year-old Casuarina
stand near Clearwater producing 15.3 metric ton/ha/yr of dry
total biomass.







Casuarina species have thus far been extremely difficult to
establish artificially. Newly planted seedlings are very
sensitive to herbaceous competition, which is prevalent in many
areas of south Florida that may be suited to Casuarina cultiva-
tion. The sandy, dry sites best suited to C. equisetifolia in
south Florida are relatively limited. Frost-hardiness of young
trees ranges from some for C. glauca, little for C.
cunninghamiana, and none for C. equisetifolia. Growth of C.
glauca on muck soil near Belle Glade, however, has been second
only to the eucalypts. Site improvement of acid flatwoods with
coal ash improves growing conditions considerably.

The long-term potential for Casuarina may be promising.
Natural stands in south Florida are extensive and contain
appreciable quantities of biomass. Such stands should regener-
ate adequately after harvest and could serve as a continual
biomass source. Further work with C. glauca and other Casuarina
species not yet evaluated may derive planting stock that is
sufficiently frost hardy. Coupled with development of cultural
systems, some Casuarina may possibly capitalize with the other
positive traits to become a SBF species.

Melaleuca

M. quinquenervia is widely established in south Florida.
Fully occupied melaleuca stands are exceptionally dense, with
biomass yields as high as 22.7 DTE/ha/year of dry stem biomass.

Coppice regeneration of melaleuca can be excellent.
Coppice stems have been observed to grow as much as three meters
during the year after harvest. The wood SG of coppice stems is
similar to that of seedlings, about 0.45 g/cm3.

Use of existing stands of melaleuca for woody biomass seems
warranted. The desirable properties of melaleuca wood and bark
(Table 3) favor its utilization, and the extent of its occur-
rence presents a large opportunity. Harvest of stands will
normally be followed by vigorous regrowth, renewing the re-
source.

ECONOMICS/ENERGETICS

Hardwood and pine chips are used as a raw material in
producing paper, and active markets exist in north Florida.
Woody biomass energy systems are potentially capable of paying
more for chips than that of current markets. If SBF is to break
even, its discounted stream of costs must be less than or equal
to these values. If the cost of production (with a discount
rate of either 4% or 8%) is estimated to be greater than the
break-even value per metric ton, the investor would be better
off investing elsewhere.

































Three-year-old Choctawhatchee sand pine on a sand-
hills site near Blountstown at 10,000 trees per
hectare.


Eucalyptus grandis

Regeneration cost represents a substantial component of the
costs incurred (Table 8). If these costs could be reduced, the
break-even value per DTE could also be reduced for a given rate
of return. The coppicing, or self regenerating property, of
Eucalyptus make it a popular choice for SBF. If two, three, or
more harvests can be obtained from a single planting, then those
original regeneration costs are distributed over three cycles,
reducing each DTE's share of the capitalized cost.

At higher planting densities, more frequent harvests are
economically optimal (Table 9). Shorter growth cycles are
desirable as the alternative rate of return is increased. Less
dense plantings demonstrate lower DTE break-even prices, whereas
longer growth cycles are preferable. Those results concur with
earlier observations that the DTE mean annual increment is
greater and is maximized at a younger age for 10,000 versus the
1,600 trees/ha.


ttl r~Arr

TV!






Table 8. Capital and energetic investments required for SBFs of three species.


Input

Site Preparation
Burn (per ha)
Double chop (per ha)
Root rake (per ha)
Bed (per ha)

Fertilization
Fertilizer (per ha)
Application (per ha)

Planting
Equipment (per 1000 trees)
Seedlings (per 1000 trees)

Administration
Land rental (per ha per year)
Taxes (per ha per year)
Personnel (per ha per year)

Removal
Harvest + Forward (per ha)
Chip (per DTE)
Transport + Storage (per DTE)
Equipment (sequestered)


E. grandis
$ mj


4.94
74.13
0.00
98.05


Slash pine
$ mj


354
4,722
0
1,131


44.48 485
7.41 90


40.00 271
80.00 329


123.55
12.36
81.94


150.00
6.62
3.31
NA


NA
NA
54


62,136

13,416
3,487


5.00
64.00
287.00
37.00


44.50
7.50


354
2,361
2,161
1,131


40.00 271
18.00 329


75.00
7.50
28.30


150.00
7.00
3.50
NA


NA
NA
54


62,136

13,416
3,497


Sand pine
$ mj


0.00
75.00
0.00
0.00


0.00
0.00


354
4,722
0
0


40.00 271
18.00 329


50.00
4.90
28.30


150.00
7.00
3.50
NA


NA
NA
54


62,136

13,416
3,487







Table 9. Economic and energy analyses of Eucalyptus grandis
SBFs on muck by planting density, age, and rotations.


1,600 Trees/Ha


Planting Density
10.000 Trees/Ha


Economic Analysis

Rate of Return
4% 8%


Rate of Return
4% 8%


-----------------($/DTE)----------------


12.67
10.54
10.20
10.03
10.38


14.71
12.83
13.06
13.31
14.34


12.32
11.27
11.27
11.40
11.92


14.58
14.05
14.75
15.71
17.22


Energetic Analysis


Total
Energy
Potent.

mj/ha)


Mean
Annual
Prod.
(1,000
mi/ha)

24
148
227
258
265
261
252


0/I Ratio,,
1 Cycle
Cycle Cycle


1.5
11.3
16.7
19.1
20.3
21.1
21.5


4.1
18.2
22.1
23.4
24.0
24.3
24.5


Total
Energy
(1,000
mj/ha)

87
395
655
843
981
1,086
1,167


Mean
Annual
Prod.
(T o00
mj/ha)

173
395
436
422
393
362
334


0/I Ratio
1 3
Cycle Cycle


6.6
15.9
18.9
20.2
20.9
21.3
21.6


13.2
21.6
23.3
23.9
24.3
24.4
24.6


- Seedling rotation + two coppice rotations.


Given the analyses assumptions, the optimal stocking level
is 1,600 trees/ha with a rotation sequence of cutting cycles
dependent upon the selected alternative rate of return. In this
case, it appears to be either every two or three years. The
denser stocking is less attractive because of the increased
variable costs. Actually, the optimal stocking probably exists
between the two densities examined.

Energy ratios for the three-cycle rotation (Table 9) were
higher because the need for energy inputs to establish the stand
are eliminated for the second and third cycles. The plantation
achieved energy ratios greater than unity within six months
after planting.


Cycle
Length
Tmos)


---






Energy ratios did not vary with planting density, but did
vary with rotation length. Closer spacings, however, resulted
in higher energy values as compared to wider spacings. Mean
annual energy production reached maxima at 30 months and 18
months for the low and high planting densities, respectively.

Slash Pine

The break-even analysis for slash pine is depicted in
Figure 5. As the stocking level is increased, greater produc-
tion levels are obtained, reducing the cost share of each DTE.
Slash pine SBF appears to be a feasible economic enterprise
given current chip prices and a rotation length of eight to 20
years. The primary reason for long optimal rotation lengths is
that the MAI is not maximized until almost age 20 after a long
steady increase. The time value of money chooses a shorter
rotation length than that chosen by the MAI criteria, but
rotation length remains at least eight years for the options
examined in this analysis. Slash pine annual energy production
peaked when the stands were 17 to 18 years old (Table 10).


Sand Pine

Sand pine has the smallest regeneration cost of the three
species examined, but also the largest break-even DTE price
range. The prices remain higher than that of Eucalyptus or
slash pine because of the slower growth function as described
earlier in Figure 6. The net effect is lower costs distributed
over fewer DTEs. If sand pine is to be a viable SBF species,
the annual planting or harvest costs would need to be less than
those predicted for the energy produced from sand pine to
generate revenues in excess of the break-even values. Delivered
ouput/input energy ratios are again favorable (Table 10).

Summary

Slash pine, sand pine, and particularly Eucalyptus grandis
SBFs have positive energy balances. Therefore, optimal species
selection, planting densities, and rotation lengths are likely
to be influenced more by economic rather than energetic consi-
derations. The input requiring the most energy in the SBF is
harvesting. To more accurately assess the total energy input
required by a SBF, this variable will need to be evaluated
intensely. These analyses suggest that SBF could supply biomass
at prices less than or comparable to current market chip prices.








Table 10. Energy potential of slash pine and sand pine SBFs by planting density and age.


3,333 Trees/Ha


Planting Density
4,444 Trees/Ha


6,667 Trees/Ha


Total
Age Energy
(yrs) (1000
mj/ha)


Annual
Enerm
(1000
mj/ha)


Delivered Total
0/I Ratio Energy
(1000
mj/ha)


Annual Delivered
Enery 0/I Ratio
(1000
mj/ha)


---------------------------------------Slash Pine------------------------------------


5
8
11
N 14
o 17
20


226
749
2,198
3,655
4,779
5,531


45.2
93.6
199.8
261.1
281.1
276.5


12.3
20.7
25.7
27.0
27.5
27.7


303
897
2,631
4,361
5,665
6,505


60.6
112.2
239.2
311.5
333.2
325.2


14.2
21.6
26.1
27.3
27.7
27.9


458
1,154
3,378
5,576
7,181
8,155


91.6
144.3
307.1
398.3
422.4
407.8


16.8
22.7
26.7
27.7
28.0
28.1


---------------------------------------- Sand Pine------------------------------------


125
458
894
1,370
1,848
2,305


25.0
57.3
81.3
97.9
108.7
115.2


8.2
17.0
21.2
23.4
24.5
25.3


152
559
1,084
1,647
2,204
2,730


30.4
69.9
98.5
117.6
129.7
136.5


9.2
18.2
22.2
24.0
25.1
25.7


189
694
1,322
1,972
2,591
3,155


37.7
86.8
120.2
140.8
152.4
157.8


10.3
19.3
22.9
24.6
25.5
26.0


Total
Energy
(1000
mj/ha)


Annual
Energy
(1000
mj/ha)


Delivered
0/I Ratio
















8%
-4%


3,333
__ \- Whole Tree Pine Chips .

4,444
6,667



------- 6,667





8 10 12 14 16 18 20
Year

Figure 5. Present net worth of slash pine woody biomass for
three planting densities and two rates of return
versus current prices for clean and whole tree dry
pine chips.








__48%
_4%


\ 3,333
S------ ------" 4,444
"" 6,667
:- ---- --- ---
Clean Pine Chips


Whole Tree Pine Chips 3,333
4,444
6,667



0-




8 10 12 14 16 18 20
Year

Figure 6. Present net worth of sand pine woody biomass for three
planting densities and two rates of return versus
current prices for clean and whole tree dry pine
chips.

STATEWIDE POTENTIAL

A number of factors influence the extent to which SBF could
be practiced in Florida. The area available by species and
productivity of these areas will limit the utilization of
particular species. Availability of land on an annual basis
will set the maximum for expansion of SBF. Ownership inclina-
tions to grow woody biomass, in response to a myriad of condi-
tions, will define the commitment of land. Various economic,
legal, institutional, and technological factors will further
restrict the scale of activity.







Land Availability

Sufficient land and landowners inclined to grow woody
biomass are prerequisites for woody biomass production. About
49% of the state is forested, with 91% (6.339 million ha) of the
forest land classified as commercial forest. Commercial forest
land is disproportionately distributed throughout the state, as
75, 70, 25, and 11% of the Northwest, Northeast, Central, and
South sections, respectively, are in commercial forest (2).

Statewide, non-forest land totals more than seven million
ha (Table 11). Some 1.4 million hectares of idle farmland,
other farmland, and rangeland constitute land that could be used
for SBFs. For example, in one north-central Florida regional
utility district, 1.95% of lands under utility management are in
right-of-way and could be available for SBFs.

Area and productivity assessments identify the potential
use of candidate biomass species (Table 12). Out of the area
presently occupied by pine or suited to pine, over 2.4 million
ha is available for slash pine and more than 1 million ha for
sand pine. More than 0.2 million ha of Eucalyptus could be
established. Melaleuca occurs in 0.186 million ha in southern
Florida with 0.016 million ha of pure stands.


Table 11. Summary of non-forest land use in Florida (adapted
from Cost and McClure (6)).
Million Hectares

Cropland 1.291
Idle farmland 0.240
Other farmland 0.090
Improved pasture 1.760
Rangeland 1.070
Urban and other 2.589

Total 7.041



Table 12. Estimates of land availability for candidate biomass
species by site production potential.
Production Potential
Species Good Medium Low Total
----------(miTion ha)----------
North Florida:
Slash pine (2) 0.473 1.534 0.434 2.441
Sand pine (2) 0.036 0.318 0.691 1.045
South Florida:
Eucalyptus (2) 0.002 0.092 0.107 0.201
Melaleuca (5) 0.186
Casuarina (1) 0.002






Partitioning of these lands into productivity classes
provides better estimation of potential (Table 12). For slash
pine, most of the 2.441 million ha would fall in the medium
productivity class with only 19% of the land base classified as
good. Of the 1.045 million ha for sand pine, 66% of the land
was estimated as having low growth potential. Even though most
of the Eucalyptus lands are subjectively judged to be low in
production potential, the actual potential of these lands to
produce biomass exceeds that of good slash pine sites.

The extent of SBFs will be influenced by the amount of
commercial forest land that is available each year. Of the
212,000 ha estimated by the USDA Forest Service, 104,000 ha are
generated by commercial harvest (Table 13). Some 108,000 ha
could be utilized each year by treating under-managed forest
lands over a 20 year time frame. Use of these undermanaged
lands is especially challenging, however, as previous history
suggests that owners of such property are not strongly inclined
to practice intensive forestry.

About 224,000 ha could conceivably be planted to SBFs each
year, when non-commercial forest land is included (Table 13).
Assuming that idle farmland is the most likely non-forest
classification to be dedicated to such use, 12,000 ha each year
could be available. Use of suitable, otherwise marginally
productive, rangeland and cropland could increase the 224,000 ha
figure appreciably.

Estimated total area for SBFs in Florida is a minimum of
4.1 million ha. This figure includes 3.9 million ha of land
suitable for present biomass species plus idle farmland. Other
land types could conceivably increase this total.

More important than the theoretical land base for SBFs is
the actual commitment of the land resources. In this regard,
owner inclinations toward growing woody biomass as opposed to a
wide variety of other land uses provide guidelines as to the
actual level of operations possible. A 1979 survey of 100
landowners in Alachua County suggested that 35% would grow trees
on their land. Of these landowners, 46% considered SBFs to be a


Table 13. Potential land available for woody biomass produc-
tion annually (adapted from 2, 6, and 7).
Thousand Hectares
Commercial Forest Land
1. Regeneration of poorly stocked land 104.8
2. Commercial harvest 104.0
3. Stand conversion 1.9
4. Salvage operations 1.6
Subtotal 212.3
Other Lands
5. Idle farmland 12.0
Total 224.3







viable land use. Long-term (20 or more years of ownership)
landowners with more than 2,000 ha were most inclined to grow
biomass.

Production Estimates

Over 33 million metric tons of woody biomass could be
produced annually if all suitable lands were committed to
intensive culture (Table 14). Because of the larger land base
for slash pine and sand pine, these species could produce 87
percent of the production for the state. In practice, a major
share of this area will be dedicated to traditional forest
management, consequently reducing the production levels for the
northern and central portions of Florida.

Eucalyptus constitutes the major potential source of woody
biomass in south Florida. In fact, given development of frost-
resistant material, Eucalyptus could assume an important role,
one not included in current projections, in central Florida.
Melaleuca can contribute significantly if currently occupied
areas are intensively managed.




Table 14. Productivity (DTE/ha/yr) and yield (million DTE/yr)
for woody biomass species by site potential in
Florida.


Species

Slash pine
Productivity
Yield

Sand pine
Productivity
Yield

Eucalyptus
Productivity
Yield

Melaleuca
Productivity
Yield

Casuarina
Productivity
Yield


Site Potential

Good Medium Low


11.00 9.50
5.20 14.57


9.00 7.00
0.32 2.23


23.00 14.00
0.05 1.29


11.00
2.05


11.0
0.02


7.50
3.26


5.00
3.46


10.00
1.07


Total



23.03


6.01


2.40



2.05


0.02
33.51







Institutional Factors


SBF will only occur on a wide scale if entrepreneurs
perceive them as profitable enterprises. First, demand must
exist for woody biomass. A market must be active currently or
expected to be established within a specified time frame.
Secondly, knowledge must exist detailing the technology and
costs of SBF. Production functions which estimate levels of
output due to alternative management decisions are necessary to
assist in calculations of the economic attractiveness of the
investment. Finally, the perceived profitability of the invest-
ment of land, labor, and capital should exceed the returns that
are feasible through the production of other goods and services.

Uses for Florida's land and water resources will continue
to become more intense as rapid population growth continues.
Those lands which have the least appeal for urban or agricul-
tural development should be examined as the future site of SBF.
Since the pulp and paper industry already exists in northern
Florida, the basic technology relating to woody biomass regen-
eration, growth management, and harvest already exists. This
technology can be adapted to plantations with substantially
greater tree densities, shorter rotations, and smaller trees at
harvest.

The transportation network currently is capable of moving
woody biomass more than 100 miles to pulp production facilities.
A labor pool is also present which is composed of experienced
woods workers. Current laws also serve to encourage responsible
forest management practices, and tax laws actually encourage
woody biomass production through the Florida Green Belt Property
Tax and the Federal Income Tax Capital Gains Exclusion Rule.

Florida imports nearly all of its energy. The land, labor
and biological management skills exist for SBF. The primary
institutional question which remains to be resolved is whether
sufficient capital and managerial expertise can be collected to
initialize a market for woody biomass for the generation of
energy. If the perceived profitability of the venture is
sufficiently attractive, then SBFs could soon serve as a renew-
able energy resource.

Commercial Applications

Commercialization of SBF depends on linking development of
operational silvicultural systems with methods of harvesting and
processing woody biomass and uses of the multiple products that
can be produced. Preparation and conversion are important
components of post-production activities.

Biomass Preparation

Woody biomass must often be preprocessed to improve its
suitability for certain applications. Of greatest importance in







many thermal conversions is a reduction in MC. A number of
options for drying of wood are available.

An effective way of removing water from whole trees is
felling the trees with branches and foliage intact and leaving
the trees in the field. Under summer conditions, MC can be
reduced as much as one-half during a six-week drying period.
Similar reductions can be obtained at other times of the year
but do require longer drying periods.

Procedures for drying wood chips, a more common method for
harvesting woody biomass, are numerous. Wood chip storage,
particularly for chips derived from the young trees produced in
SBF, may be critical. Some options include 1) forced air
drying, 2) drying under selected temperatures and relative
humidities, and 3) storage and drying in perforated containers.

Conversion

Woody biomass can be converted thermochemically to energy
by the following methods:

1. Direct combustion.--Burning and utilization of the heat
to produce process steam is a common application in the
forest products industry and also has application to
the generation of electricity. Home heating is another
common use.

2. Gasification/Methanation.--High yields of low BTU or
medium BTU gases are possible with the thermo-gasifica-
tion process. Applications include a number of on-site
power uses and possible substitution for natural gas.

3. Pyrolysis/Liquefaction.--High temperature and high
pressure processes can produce charcoal, acetic acid,
methanol, and even fuel oil.

Particular chemicals can also be derived from wood.
Through hydrolysis, glucose can be obtained from cellulose and
converted to ethanol by commerical methods. Similarly, simple
sugars can be produced from hemicelluloses. By harsh hydrogena-
tion and hydrogenolysis processes, lignin can be converted to
simple compounds such as benzene and phenol. Resin, essential
oils, tannins, and phenolics may be used as feedstocks for many
chemical products currently made from petrochemicals.

A number of woody energy facilities are operational in
Florida. Forest industries, including 10 pulp and paper mills
that historically have derived a major share of their energy
from woody biomass, nearly doubled their use of fuelwood in the
last decade. As of 1984, other users include the following:

1. A fully integrated system, from producing wood chips to
using the generated energy, for producing steam at the
Union Correctional Institute in Union County.







2. A greenhouse at the IFAS Agricultural Research Center
at Monticello heated by a wood-fired gasifier.

3. A wood-fueled boiler at Koppers, Inc., in Gainesville
run on wood residue.

4. A wood-using facility at Bartow utilizing citrus
residues.

5. A municipal sewage plant at Largo operating on urban
tree residues.

LITERATURE CITED

1. Arvanitis, L. G., and M. Newton. 1980. Estimation of
acreage by ownership and land-use/soil-potential
categories for selected tree species in Florida.
Unpublished Final Rept. for DOE. Washington, D.C.,
Vol. 1. 195 pp.

2. Bechtold, W. A., and H. A. Knight. 1982. Florida's
forests. USDA For. Serv. Res. Bull. SE-62. 84 pp.

3. Brendemuehl, R. H. 1973. Some responses of sand pine to
fertilization. USDA For. Serv. Gen. Tech. Rpt. SE-2:
164-179.

4. Campbell, M.S.F., C. W. Comer, D. L. Rockwood, and C.
Henry. 1983. Biomass Productivity of slash pine in
young, heavily-stocked stands. Proc. 1983 S. For.
Biomass Work. Group Wrkshp.:77-82.

5. Cost, N. K., and G. C. Craver. 1981. pp. 1-8. Distribu-
tion of Melaleuca in south Florida measured from the
air. In R. K. Geiger (ed.). Melaleuca Symposium Proc.
Sept. 23-24, 1980. Florida Division of Forestry,
Tallahassee, FL.

6. Cost, N. D., and J. P. McClure. 1982a. Multiresource
inventories: techniques for estimating biomass on a
statewide basis. USDA For. Serv. Res. Paper SE-228. 31
pp.

7. Cost, N. D., and J. P. McClure. 1982b. Multiresource
inventories forest biomass in Florida. USDA For.
Serv. Res. Paper SE-235. 24 pp.

8. Frampton, L. J., Jr., and D. L. Rockwood. 1982. Genetic
variation in biomass traits of sand and slash pines.
Silvae Genetica 31(2-3):18-23.

9. Geary, T. F., G. F. Meskimen, and E. C. Franklin. 1983.
Growing eucalypts in Florida for industrial wood
production. USDA For. Serv. Gen. Tech. Rpt. SE-23. 43
pp.







10. Meskimen, G. 1983. Realized gain from breeding Eucalyptus
grandis in Florida. USDA For. Serv. Gen. Tech. Rpt.
PSW-69:121-128.

11. Roberts, D. R. 1973. Inducing lightwood in pine trees by
paraquat treatment. USDA For. Serv. Res. Note SE-191.
4 pp.


12. Rockwood, D. L., L. F. Conde, and R.
1980a. Biomass production of
Choctawhatchee sand pine. USDA For.
SE-293. 6 pp.


13. Rockwood, D.
Huffman,
Report:
Florida.
9050/1.


H. Brendemuehl.
closely spaced
Serv. Res. Note


L., Comer, C. W., Conde, L. F., Dippon, D. R.,
J. B., Riekerk, H. and Wang, S.: 1983. Final
Energy and Chemicals from Woody Species in
Oak Ridge National Laboratory. ORNL/Sub/81-
205 pp.


14. Wang, S., R. C. Littell, and D. L. Rockwood. 1983.
Variation in density and moisture content of wood and
bark among 20 Eucalyptus grandis progenies. Wood Sci.
Technol. 18:97-100.

METRIC TO ENGLISH CONVERSIONS


.394 in
3.28 ft
2.47 acre
35.31 ft3


1 metric ton = 1.10 ton
1 kg/ha = .982 Ib/acre
1 metric ton/ha = .446 ton/acre
1 kj/kg = 2.320 BTU/lb






































This public document was promulgated at an annual cost of
$1590 or a cost of 790 per copy to provide information on short-
rotation culture of woody species for biomass production.


All programs and related activities sponsored or assisted by the Florida
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ISSN 0096-607X


I UNIVERSITY OF FLORIDA I