Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material: Evaluation Study of Select Blends of Cotton Byproducts

Abstract

Since polystyrene is non-biodegradable, a biodegradable material that is eco-friendly is being sought
as a substitute for packaging and insulation board consumers. One such process, developed by
Ecovative Design, LLC, involves growing fungal species on agricultural biomass to produce an ecofriendly
packaging product (EcoCradle™) and insulation panels (Greensulate™). The objective of
this research was to develop and evaluate six blends of processed cotton plant biomass (CPB)
materials as a substrate for colonization of selected fungi in the manufacture of molded packaging
material. The blends were comprised of processed CPB, cotton seed hulls, starch, and gypsum. The
four ingredients were the same mix percentage for all six blends with the particle size of the CPM
being the only difference. CPB particles sizes ranged from 0.1 to 51 mm. Tests were conducted to
evaluate the physical and mechanical properties of the six CPB blends. Test results revealed blends
that met or exceeded like characteristics of extruded polystyrene foam.

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RESEARCH ARTICLE
Copyright © 2012 American Scientific Publishers
All rights reserved
Printed in the United States of America
Journal of
Biobased Materials and Bioenergy
Vol. 6, 431–439, 2012
Fungal Mycelium and Cotton Plant Materials in the
Manufacture of Biodegradable Molded Packaging
Material: Evaluation Study of Select
Blends of Cotton Byproducts
G. A. Holt1∗, G. McIntyre2, D. Flagg2, E. Bayer2, J. D. Wanjura1, and M. G. Pelletier1
1USDA-ARS Cotton Production and Processing Research Unit 1604 E. FM 1294, Lubbock, TX 79403, USA
2Ecovative Design, LLC, 60 Cohoes Avenue, Green Island, NY 12183, USA
Since polystyrene is non-biodegradable, a biodegradable material that is eco-friendly is being sought
as a substitute for packaging and insulation board consumers. One such process, developed by
Ecovative Design, LLC, involves growing fungal species on agricultural biomass to produce an eco-
friendly packaging product (EcoCradle™) and insulation panels (Greensulate™). The objective of
this research was to develop and evaluate six blends of processed cotton plant biomass (CPB)
materials as a substrate for colonization of selected fungi in the manufacture of molded packaging
material. The blends were comprised of processed CPB, cotton seed hulls, starch, and gypsum. The
four ingredients were the same mix percentage for all six blends with the particle size of the CPM
being the only difference. CPB particles sizes ranged from 0.1 to 51 mm. Tests were conducted to
evaluate the physical and mechanical properties of the six CPB blends. Test results revealed blends
that met or exceeded like characteristics of extruded polystyrene foam.
Keywords: Composite, Cotton, Mycelium, Biobased, Biodegradable.
1. INTRODUCTION
Polystyrene is a hydrocarbon based material typically
used in the manufacture of packaging materials. Marketed
under the name Styrofoam™, this lightweight material
is hydrophobic, resistant to photolysis, and is not sub-
ject to decomposition or decay.1These characteristics are
attractive to shippers and the packaging industry, but they
create problems with respect to recycling, reuse, and land-
fill operation.2Recent scientific investigation resulted in
development of an economically viable, environmentally
friendly replacement for polystyrene packaging materials.
The packaging material evaluated in our study is a com-
posite containing selected agricultural residues and a spe-
cific fungus.
Annually renewable crops and their agricultural residues
have been researched extensively as materials that could
potentially enhance the properties of composite products
made from fossil fuel based derivatives that are more resis-
tant to biodegradation.3–6 In addition to the crops and agri-
cultural residues, fungi and/or their constituents have been
∗Author to whom correspondence should be addressed.
Email: greg.holt@ars.usda.gov
studied and used to manufacture environmentally friendly
products.7–10 The combination of agricultural residues and
fungi have been evaluated for fungal cultivation11–15 and
improving bonding properties of agricultural fibers in the
manufacture of composites.1617 However, a method for
producing a composite comprised of agricultural residues
and fungi was not found in the literature.
Bayer et al.18 and Bayer and McIntyre19 developed pro-
cesses that involve growing fungal species on agricul-
tural residues, such as cotton plant material, to produce an
environmentally-friendly packaging material. The objec-
tive of the present study was to develop six blends of
specifically processed cotton plant material for use with
the Bayer et al.18 and Bayer and McIntyre19 processes.
Each of the six blends was used to produce a packag-
ing material that was subjected to standard test methods
for compressive strength,20 flexural strength,21 modulus of
elasticity,21 density,22 dimensional stability,22 accelerated
aging,23 water absorption,24 cone calorimetry,25 and ther-
mal conductivity.26 The cotton plant material used in this
study was a byproduct of typical mechanical harvesting
and ginning practices in the United States which gener-
ate approximately 2.5 Mg of cotton byproducts across the
U.S. cotton belt each year.27
J. Biobased Mater. Bioenergy 2012, Vol. 6, No. 4 1556-6560/2012/6/431/009 doi:10.1166/jbmb.2012.1241 431

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Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material Holt et al.
2. MATERIALS AND METHODS
2.1. Cotton Plant Biomass and Blends
The cotton plant material was obtained from a cotton gins
agricultural waste stream. Specifically, the cotton carpel
(bur) was obtained from the extractors27 in the United
States Department of Agriculture–Agricultural Research
Service (USDA-ARS) gin lab in Lubbock, Texas. The
extractors removed approximately 55% of the total waste
stream, primarily sticks and carpel, from the incoming
seedcotton before the seedcotton entered the gin stand(s).
The cotton carpels were processed through a Jacobson
model 4D hammer-mill (Jacobson Machine Works, Min-
neapolis, MN) or a Reynolds Engineering model T00-18
attrition mill (Reynolds Engineering and Equipment,
Muscatine, IA) and then sorted across a Triple/S Dynam-
ics model VCSUF-24X12-3 vibratory conveyor (Triple/S
Dynamics, Inc., Dallas, TX) to obtain the specific particle
size ranges needed for each blend (Table I). The cotton
carpel material, for one of the blends, before and after
processing is shown in Figure 1. The sized material was
packaged and stored in a dry location until blending. The
cotton plant material particles were sized to be within the
desired range, 0.1 to 51 mm.
Blending of the cotton plant material was accomplished
with a Davis 1.4 Mg ribbon mixer (H.C. Davis Sons Man-
ufacturing Co., Inc., Bonner Springs, KS). Each blend was
processed in 159 kg batches. The constituent materials
used in the six blends evaluated were comprised of:
(1) processed cotton carpel,
(2) cotton seed hull,
(3) starch, and
(4) gypsum.
The primary ingredient in each of the six blends was the
processed cotton carpel. For all six blends, the ingredi-
ents were added at the same percentages with the only
difference being the particle size range of the processed
cotton carpel (Table I). Each ingredient was added one at
a time into the mixer and agitated while adding between
1.5 to 2.5 l of water, to minimize dust and promote
adhesion of the starches and gypsum to the cotton plant
Table I. Particle size ranges for cotton plant material used in each of
the six blends evaluated in this study.
Primary particle size range of
Blendsaprocessed cotton plant material (mm)
1 28–51
2 12–28
3 0.1–12
4 12–51
5 0.1–12, 28–51
6 0.1–51
Notes:aPrimary ingredient of each blend was the processed cotton plant material.
The other ingredients in each blend were starch, gypsum, and cottonseed hulls.
Fig. 1. Some of the cotton plant material used in this study before (left)
and after (right) processing.
material. Once all the ingredients were added, the blend
was allowed to mix for 7 min, at maximum agitation
(15 rpm). Upon completion of the mixing, the blend
was emptied into a tote bag, labeled, and stored until
shipment to Ecovative Design’s facility in Green Island,
NY. Specifics related to constituent fraction of the blends
are considered proprietary information by Ecovative
Design, LLC.
2.2. Composite Fabrication
At Ecovative’s research laboratory in Green Island,
New York, is the pilot manufacturing plant. A schematic
of the pilot plant process is shown in Figure 2. At the
pilot plant, the tote bags with each blend were emptied
into a bulk bin with a live-bottom auger that fed a pas-
teurizer where the material was sterilized at 115 C for
approximately 28 min. Exiting the pasteurizer, the blend
was gravity fed into a water-jacketed auger (cooler) where
it was cooled below 35 C. Upon exiting the cooler, the
blend was inoculated with the fungus, Ganoderma sp.,
using a specified grain or liquid substrate as the carrier.
After inoculation, the blend was discharged into a plas-
tic mold, referred to as a tool, which was in the desired
shape of the piece to be fabricated. The material was gen-
tly hand-packed in the tool and any excess was removed,
the tool was then sealed in order to maintain a consistent
micro-environment for fungal propagation (Fig. 3). The
filled tool was incubated on a bread rack at 21 C for
5-days at which time the fungal mycelium colonized the
blend. Figure 4 shows the fungal colonization of one of
the blends over a three day period. After 5 days, the part
was removed from the tool and placed in 60 C convec-
tion oven for 8 h, which inactivated the fungus and pre-
vented reanimation. After drying, the pieces were stored at
ambient laboratory conditions (approximately 21 C and
30% RH) until testing. Figure 5 shows a typical part after
drying. Specifics related to quantity of inoculum, pasteur-
izer and cooler speeds, and specific processes applied not
listed are considered proprietary information by Ecovative
Design, LLC.
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Holt et al. Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material
Fig. 2. Schematic of Ecovative’s pilot manufacturing facility used to produce the cotton plant and fungal mycelium based molded packaging specimens
evaluated in this study.
2.3. Analytical Testing
Each of the six blends was used to produce a packag-
ing material that was subjected to standard test meth-
ods for compressive strength,20 flexural strength21 (Fig. 6),
modulus of elasticity,21 density,22 dimensional stability,22
accelerated aging,23 water absorption,24 cone calorimetry25
(Fig. 7), and thermal conductivity.26 Cone calorime-
try (flame retardance characteristics) was performed at
the Worcester Polytechnic Institute (WPI) Fire Research
Laboratory in Worcester, MA. Specimens were tested in
Fig. 3. Selecting the lid for the tool containing inoculated cotton plant material substrate (left) and snapping the lid in place (right) to maintain
micro-environment for optimum growth.
horizontal orientation at 50 kW/m2heat flux. All other
analyses were conducted at the Ecovative research labo-
ratory. We did not evaluate expanded polystyrene samples
in this study. Numerous sources of information pertain-
ing to physical and mechanical properties of expanded
polystyrene are available in the public domain.28–31
2.4. Data Analysis
Two types of inoculum (grain and liquid substrate) were
applied to each of six cotton plant material blends for a
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RESEARCH ARTICLE
Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material Holt et al.
Fig. 4. Time sequence showing the inoculated cotton plant material sub-
strate (day 0) and fungal colonization over a 3-day period. The white
specks are the living fungus.
Fig. 5. Finished fungal mycelium molded packaging piece after drying.
total of 12 treatments. Each treatment was replicated from
3 to 12 times depending on the test method and property
being evaluated. Standard analysis of variance techniques
were used to analyze the data to determine statistically
significant differences among the 12 treatments by the
Tukey-Kramer Honestly Significant Difference (HSD) test
(release 9.2, SAS Institute Inc., Cary, NC) at the 95% con-
fidence level.
Fig. 6. Flexural strength testing of one of the cotton plant material test
specimens.
Fig. 7. Cone calorimeter test samples of two of the treatments evaluated
in this study, Grain 6 (left) and Grain 4 (right), after testing.
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3. RESULTS AND DISCUSSION
3.1. Physical Properties
Figure 8 shows a comparison of the dimensional stability
(surface area contraction) of the treatments after drying.
Blends inoculated with the grain-based substrate showed
less surface area contraction than did blends inoculated
with the liquid-based substrate. Grain 3 (Blend 3, grain-
based inoculum) had the smallest measured surface area
contraction (0.64%), whereas Liquid 5 (Blend 5, liquid-
based inoculum) exhibited the greatest measured surface
area contraction (2.4%). Grain 3, 4, 5, and Liquid 6 were
similar in the percent contraction and significantly lower
than Grain 2, Liquid 1, 2, 3, 4, and 5.
The importance of dimensional stability is related to
tool design. The larger the percent contraction the more
oversized the tool needs to be for the finished product to
be within desired specifications. Another factor influenc-
ing tool design is contraction variability. The more vari-
able a blend/inoculum combination is, the more difficult
it is to produce parts that are consistently within dimen-
sional tolerances of customer specifications. All treatments
had similar standard mean errors associate with percent
contraction (0.093 to 0.108), so the means are a reliable
indicator of the contraction expected when designing tools
for a given treatment.
The flexure strength (FS), elastic modulus (EM), and
compressive strength (CS) in Table II are normalized to
a standard density of 32.04 kg/m3since this is the den-
sity of the polystyrene packaging the EcoCradle material
can replace in the market. The density of the treatments
ranged from 66.5 kg/m3to 224 kg/m3. The density for
grain treatments was higher than for the liquid treatments
Fig. 8. Average surface area contraction (%) or shrinkage of the sample pieces made from each treatment after oven drying. Bars with the same
letters are not significantly different at the 0.05 level of significance.
due to the greater mass of the grain-based inoculum versus
the liquid-based inoculum. The density adjusted values for
FS show Grain 1 and Grain 6 with the highest values at
26 kPa and Liquid 2 with the lowest at 7 kPa. The EM
was significantly higher for Liquid 5 (674 kPa) than all
other treatments with Liquid 2 having the lowest, 123 kPa.
Compressive strength was significantly higher for Liquid 3
(72 kPa) than for all other treatments with Liquid 4 having
the lowest CS at 1.1 kPa.
Sample degradation associated with FS, EM, and CS
resulting from accelerated aging testing is shown in
the second column of Table II. The percent degrada-
tion data was calculated according to the equation in the
standard:23
Degradation Percentage
=(Conditioned test value/as received test value) ∗100
Therefore, values closer to the base line (100%) exhibit
less degradation than samples with values further from the
baseline. FS degradation for Grain 5, 1, 6, and Liquid 3
exhibited little degradation from aging. Liquid 5’s FS was
reduced almost in half as a result of aging whereas the
FS of Grain 3 and Liquid 2 exhibited increased stiffness
due to aging. EM for Grain 6 had the largest change in
percent degradation of 318.6%. Liquid 5 had the largest
reduction in EM at 43.6%. The treatments that had the
largest percent CS degradation were Liquid 5 (250.1%)
and Liquid 3 (6.8%). The CS degradation was least for
Grain 4 (92%) and Grain 1 (110%). Overall, Grain 1 had
the most consistent performance, by exhibiting some of the
lowest degradation values for FS, EM, and CS compared
to all other treatments.
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Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material Holt et al.
Table II. Physical properties from molded packaging material produced
from six cotton-based substrate blends and two fungal inoculum methods.
Physical properties (density adjusted)
Response variableaFlexure strength Flexure strength degradation
StandardbASTM C203 ASTM C481
Units (kPa) (%)
Inoculum/blend ValuecInoculum/blend Valuec
Grain 1 261A Liquid 2 1967A
Grain 6 259A Grain 3 1860A
Grain 2 235A B Grain 4 1812A B
Grain 5 219A B C Liquid 4 1583A B
Liquid 1 208A B C Liquid 6 1557A B
Liquid 5 196A B C Liquid 1 1151A B
Liquid 3 164A B C Grain 2 1116A B
Grain 3 123B C Grain 6 1005A B
Grain 4 104B C Grain 1 1003A B
Liquid 6 101B C Grain 5 1001A B
Liquid 4 97B C Liquid 3 950A B
Liquid 2 70C Liquid 5 600B
Response variableaElastic modulus Elastic modulus degradation
StandardbASTM C203 ASTM C481
Units (kPa) (%)
Inoculum/blend ValuecInoculum/blend Valuec
Liquid 5 6745A Grain 6 3186A
Grain 2 3956B Liquid 2 1894A B
Grain 1 3681B C Grain 3 1659A B
Liquid 3 3442B C Grain 5 1641B
Liquid 4 3318B C Grain 4 1632A B
Grain 3 3174B C Liquid 6 1507A B
Liquid 6 3088B C Liquid 3 1421B
Grain 6 2884B C Grain 2 1347A B
Grain 5 2834B C Liquid 4 1219B
Liquid 1 2538B C Grain 1 984B
Grain 4 1991B C Liquid 1 955B
Liquid 2 1228C Liquid 5 436B
Response Compressive Compressive strength
variableastrength degradation
StandardbASTM C165 ASTM C481
Units (kPa) (%)
Inoculum/blend ValuecInoculum/blend Valuec
Liquid 3 722A Liquid 5 2501A
Liquid 1 335B Grain 3 1695A B
Grain 6 110B C Grain 2 1399A B
Grain 2 90B C Liquid 4 1202A B
Grain 5 85B C Grain 1 1101A B
Grain 4 62C Grain 4 917A B
Grain 1 54C Liquid 6 877A B
Liquid 2 33C Grain 6 605A B
Liquid 6 30C Liquid 2 477A B
Grain 3 23C Grain 5 421A B
Liquid 5 14C Liquid 1 81A B
Liquid 4 11C Liquid 3 68B
Notes:aResponse variables are normalized to a density of 32.04 kg/m3.
Degradation =(Tested specimen value/as received specimen value)∗100. Degrada-
tion values of 100 indicate no change before and after testing. bASTM =American
Society for Testing and Materials. cMeans within the same column followed by
different letters in the corresponding row are statistically different at the 0.05 level
of significance.
Table III. Water absorption testing results from molded packaging
material produced from six cotton-based substrate blends and two fungal
inoculum methods.
Water absorption
Response Gain after Gain after Gain after
variable 75 hr 3 hr 168 hr
Standard ASTM C1134 ASTM C1134 ASTM C1134
Units (%) (%) (%)
Inoculum/ Inoculum/ Inoculum/
blend Valuebblend Valuebblend Valueb
Grain 1 307A Grain 1 480A Grain 1 1981A
Liquid 1 207A B Liquid 4 392A B Liquid 4 1780A
Grain 5 171B C Liquid 1 342A B Liquid 1 1688A
Liquid 2 139B C Grain 5 298A B Liquid 5 1637A
Liquid 5 115B C Liquid 5 258A B Grain 5 1550A
Liquid 4 112B C Liquid 2 252A B Liquid 2 1536A
Liquid 3 103B C Liquid 6 214A B Liquid 6 1324A
Grain 2 99B C Grain 3 179B Grain 2 1269A
Grain 3 93B C Grain 2 177B Grain 4 1103A
Grain 4 90B C Liquid 3 155B Liquid 3 1061A
Liquid 6 70C Grain 4 122B Grain 6 943A
Grain 6 64C Grain 6 108B Grain 3 935A
Notes:aASTM =American Society for Testing and Materials. bMeans within the
same column followed by different letters in the corresponding row are statistically
different at the 0.05 level of significance.
3.2. Water Absorption
The water absorption results (Table III) show the percent
weight gain after 0.75 h, 3 h, and 168 h. After 0.75 h, Grain
6 (6.4%) and Liquid 6 (7.0%) had the lowest water absorp-
tion whereas Grain 1 (30.7%) and Liquid 1 (20.7%) had the
highest. Grain 1 had significantly higher water absorption
after 0.75 h than all other treatments except Liquid 1.
Table IV. Conductivity and R-values from molded packaging material
produced from six cotton-based substrate blends and two fungal inoculum
methods.
Thermal properties
Response variable R-value Conductivity
StandardaTPS500 TPS500
Units – W/m ∗K
Inoculum/blend ValuebInoculum/blend Valueb
Liquid 6 151A Grain 3 018A
Liquid 3 140A B Liquid 4 017A
Liquid 1 128A B Grain 1 016A B
Grain 2 115A B Liquid 5 015A B
Grain 4 114A B Grain 6 015A B
Grain 5 112A B Liquid 2 015A B
Liquid 2 105A B Grain 5 013A B
Grain 6 100A B Grain 2 013A B
Grain 1 096B Grain 4 013A B
Liquid 4 087B Liquid 1 012A B
Liquid 5 084B Liquid 3 012A B
Grain 3 082B Liquid 6 010B
Notes:aTSP =Transient plane source from therm test incorporated, Frederiction,
Nebraska, USA. bMeans within the same column followed by different letters in
the corresponding row are statistically different at the 0.05 level of significance.
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After 3 h, Grain 1 (48.0%) still had the highest water
absorption and Grain 6 (10.8%) the lowest. However,
Grain 1 was only significantly higher than five other treat-
ments: Grain 2, Grain 3, Grain 4, Grain 6, and Liquid 3.
Table V. Cone calorimeter testing results from molded packaging material produced from six cotton-based substrate blends and two fungal inoculum
methods.
Thermal properties
Response variable Peak heat release rate Average heat release rate Peak carbon monoxide
StandardaASTM E1354 ASTM E1354 ASTM E1354
Units kW/m2kW/m2kW/m2
Inoculum/blend ValuebInoculum/blend ValuebInoculum/blend Valueb
Liquid 2 1158A Liquid 2 753A Grain 6 5550A
Grain 1 1133A Liquid 6 665A B Liquid 2 247B
Liquid 6 1070A Grain 5 663A B Liquid 4 229B
Grain 4 1053A Liquid 4 625A B Liquid 6 213B
Grain 2 1040A Grain 3 617A B Grain 1 200B C
Grain 3 1040A Liquid 5 613A B Grain 5 200B C
Grain 6 1035A Grain 4 593A B Liquid 5 197B C
Grain 5 1033A Grain 2 572A B Liquid 1 177BCD
Liquid 5 991A Grain 6 565A B Grain 4 167BCD
Liquid 4 973A B Liquid 1 562A B Grain 2 158BCD
Liquid 1 919A B Grain 1 553B Grain 3 100C D
Liquid 3 657B Liquid 3 549B Liquid 3 090D
Response variable Average carbon monoxide Peak carbon dioxide Average carbon dioxide
StandardaASTM E1354 ASTM E1354 ASTM E1354
Units mg/s mg/s mg/s
Inoculum/blend ValuebInoculum/blend ValuebInoculum/blend Valueb
Grain 6 5100A Grain 6 26180A Grain 6 24280A
Liquid 6 077B Liquid 6 4014B Liquid 2 2465B
Grain 2 068B C Grain 4 3963B Liquid 6 2203B
Liquid 4 052B C Grain 1 3897B Liquid 4 2098B
Liquid 2 050B C Grain 5 3827B C Grain 5 2027B
Liquid 5 046B C Liquid 2 3826B C Liquid 5 1976B
Liquid 1 044B C Liquid 5 3412B C Grain 4 1957B
Liquid 3 034B C Liquid 1 3235B C Grain 1 1863B
Grain 3 033B C Grain 3 3127B C Liquid 1 1856B
Grain 1 000C Liquid 4 3119B C Grain 3 1723B
Grain 4 000C Grain 2 3101B C Liquid 3 1516B
Grain 5 000C Liquid 3 2378C Grain 2 1446B
Response variable Peak mass loss rate Average mass loss rate Mass loss
StandardaASTM E1354 ASTM E1354 ASTM E1354
Units mg/s mg/s mg/s
Inoculum/blend ValuebInoculum/blend ValuebInoculum/blend Valueb
Grain 1 1533A Liquid 3 714A Liquid 4 740A
Grain 4 1500A B Liquid 6 667A Grain 5 727A
Liquid 4 1367A B Liquid 5 621A B Grain 1 720A
Grain 5 1267A B Liquid 4 616A B Grain 2 702A
Grain 6 1250A B Liquid 1 591A B Grain 6 700A
Liquid 6 1200A B Grain 6 520A B Grain 4 690A
Grain 2 1150A B Grain 2 460A B Liquid 2 686A
Liquid 1 1133A B Grain 1 387A B Liquid 5 555A
Liquid 5 1067A B Grain 5 370A B Grain 3 527A B
Grain 3 1033A B Grain 3 363A B Liquid 1 462A B
Liquid 3 900A B Grain 4 170A B Liquid 6 396A B
Liquid 2 767B Liquid 2 15B Liquid 3 88B
Notes:aASTM =American Society for Testing and Materials. bMeans within the same column followed by different letters in the corresponding row are statistically
different at the 0.05 level of significance.
The largest increase in water absorption from 0.75 h to 3 h
was seen in Liquid 4 which moved from 11.2% to 39.2%.
The smallest increase from 0.75 h to3hwasGrain 4,
8.9% to 12.2%.
J. Biobased Mater. Bioenergy 6, 431–439, 2012 437

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Greg Holt
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RESEARCH ARTICLE
Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material Holt et al.
The percent water absorption after 168 h indicated no
significant differences between any of the treatments. The
largest absorption, after 168 h, was seen in Grain 1 (198%)
with the lowest percent absorption in Grain 3 and Grain 6,
93.5% and 94.3%, respectively.
3.3. Thermal Properties
The thermal properties (Tables IV and V) show thermal
conductivity26 and cone calorimetry25 data. The thermal
resistance and conductivity data (Table IV) show Liq-
uid 6 with the highest R-value (1.5) which was signifi-
cantly higher than Grain 1 (0.96), Liquid 4 (0.87), Liquid 5
(0.84), and Grain 3 (0.82). Thermal conductivity was high-
est with Grain 3 (0.18) and lowest with Liquid 6 (0.10).
The conductivity values were within the ranges of gypsum
(0.17), high density hardboard (0.15), plywood (0.12), and
both hardwoods (0.16) and softwoods (0.12) at 26.8 C.32
Cone calorimeter testing (Table V) showed gas pro-
duction (carbon monoxide, CO and carbon dioxide, CO2)
for Grain 6 to have significantly higher gas production
than all other treatments, 55.5 mg/s—peak CO; 51 mg/s—
average CO; 2618 mg/s peak CO2; 2428 mg/s—average
CO2. Originally upon examination of the large difference
between the Grain 6 data and the other treatments, the
Grain data was questioned as a potential error in data entry
or perhaps a mistake during the analytical analyses. Upon
further review and analysis, validity of the data was estab-
lished by investigation into the interaction of substrate par-
ticle size and method of inoculation to cone calorimeter
analysis. The lowest peak CO gas production was seen
in Liquid 3 (0.9 mg/s). The average CO production for
Grain 1, Grain 4, and Grain 5 show zero emissions when in
actuality they are less than 0.00 mg/s. With the exception
of Grain 6, all other treatments had average CO production
less than 1.0 mg/s. The peak and average CO2production
was lowest for Liquid 3 (237.8 mg/s—peak; 151.6 mg/s—
average) and Grain 2 (310.1 mg/s—peak; 144.6 mg/s—
average).
Cone calorimeter testing showed Liquid 3 had the small-
est mass loss (8.8%) compared to Liquid 4 with 74%.
Liquid 3 had significantly lower mass loss than all treat-
ments except Grain 3 (52.7%), Liquid 1 (46.2%), and
Liquid 6 (39.5%). The peak and average mass loss rate
were lowest for Liquid 2, 76.7 mg/s and 1.5 mg/s, respec-
tively. The highest peak and average mass loss rates
were seen in treatments Grain 1 (153.3 mg/s—peak) and
Liquid 3 (71.4 mg/s—average).
3.4. Application of Findings
Results of this study indicate that cotton-based fungal
mycelium packaging material is a viable alternative to
polystyrene packaging. Figures 9 and 10 show two com-
mercial applications for the type of products produced
from two blends evaluated in this study. Figure 9 shows
Fig. 9. Fungal mycelium and cotton plant material molded packaging
material being used by a large office equipment manufacturer in the
United States.
Fig. 10. Fungal mycelium and cotton plant material molded packag-
ing material being used by a large computer manufacturer in the United
States.
an application using treatments Grain 1 and Grain 2 and
Figure 10 is a hybrid whose development was a direct
result of the findings in this study.
4. CONCLUSIONS
This study evaluated six cotton-based biomass blends for
use in a process designed to produce an environmentally-
friendly molded packaging material that could replace
polystyrene packaging currently in the marketplace.
In addition to the six cotton-based blends, two methods,
grain and liquid, were used to inoculate the blends with
fungal spores resulting in twelve treatments. The blends
were inoculated and the test specimens grown in tools
(plastic molds) for 5 days and then dried to remove mois-
ture. The recipe for each blend was identical except for
the particle size range of the cotton-based materials. The
difference in the inoculums was that one carried the fungal
spores on kernels of grain whereas the other had the fungal
spores suspended in liquid. The liquid inoculum was easier
to use in the process and provided a more consistent dis-
tribution of fungal spores when applied to the blends. The
grain inoculum generally resulted in higher densities due
438 J. Biobased Mater. Bioenergy 6, 431–439, 2012

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Greg Holt
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RESEARCH ARTICLE
Holt et al. Fungal Mycelium and Cotton Plant Materials in the Manufacture of Biodegradable Molded Packaging Material
primarily to the added weight of the grain. The densities
were higher than desired (32.04 kg/m3) due in large part
to the inclusion of cotton plant particles less than 2 mm.
In future studies, cotton plant material having a diame-
ter less than 2 mm will not be used. No single treatment
outperformed the other treatments in all categories evalu-
ated. Most of the treatments performed similarly to each
other for the response variables measured. In regards to
percent degradation associated with accelerated aging test-
ing, Grain 1 was most consistent in maintaining flexural
and compressive strength and elastic modulus.
Overall, the use of cotton-based fungal mycelium pack-
aging material is a viable alternative to polystyrene
packaging. As refinements in processing and biomass
blend development continue, the physical and mechanical
properties of the product should improve. Improved phys-
ical characteristics will cause agricultural residue-based
fungal composites to be suitable for numerous applications
that presently use fossil-fuel based materials.
Abbreviations
CGB: Cotton Gin Byproducts
Disclaimer
Mention of product or trade names does not constitute
an endorsement by the USDA-ARS over other compara-
ble products. Products or trade names are listed for ref-
erence only. USDA is an equal opportunity provider and
employer.
Acknowledgment: This project was a collaborative
effort involving USDA-ARS in Lubbock, TX, and
Ecovative Design, LLC of Green Island, NY, under a
Cooperative Research and Development Agreement (#58-
3K95-0-1391). The authors would like to thank Philip
Pearson, Bill Turner, Jeff Turner, Jimmie Castro, Gary
Schlabs, Clinton Cox, and Chris Arinder for their work
in preparation of this manuscript, processing the cotton
byproducts, and making the blends used in this study.
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Received: 28 July 2011. Accepted: 2 April 2012.
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