Development of Affordable Building Materials Using Agricultural Waste By-Products and Emerging Pith, Soy and Mycelium Biobinders

Abstract

Along the hot-humid belt, rapidly developing countries that lack affordable building materials have overlooked the potential of agricultural wastes as alternative resources. Globally, 140 billion metric tons of agricultural by-products (ABPs) are generated annually, representing an abundant, renewable material stream. Industrial ecologists have recently investigated the upcycling of ABPs into biocomposites to replace conventional wood products that use harmful urea-formaldehyde, phenolic compounds, and isocyanate resins. This paper evaluates the upcycling of coconut ABP using nontoxic, renewable biobinders under comparatively low-energy conditions to create affordable structural and cladding building materials. In this paper, we investigate the effects of processing variables on board mechanical performance using the ASTM D-1037 standard, these are: (i) fiber processing, (ii) fiber-binder ratios, (iii) pre-pressing methods, by which binders initially adhere to fibers, using established thermal pressing conditions within each biobinders industry. Here, we compare the mechanical properties of medium-high density boards (500-1200 kg/m 3), made from coconut fibers bonded by coconut pith, soy protein, or fungal mycelium, to those of common medium-high density wood and reconstituted wood products.

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PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
Development of Affordable Building Materials Using
Agricultural Waste By-Products and Emerging Pith, Soy and
Mycelium Biobinders
Lokko, M.J.1, Rowell, M.2, Dyson, A. 1, Rempel, A.1
1Center for Architecture, Science and Ecology, Rensselaer Polytechnic Institute, New York, USA
2e2e Materials, Ithaca NY, USA
ABSTRACT: Along the hot-humid belt, rapidly developing countries that lack affordable building materials
have overlooked the potential of agricultural wastes as alternative resources. Globally, 140 billion metric tons of
agricultural by-products (ABPs) are generated annually, representing an abundant, renewable material stream.
Industrial ecologists have recently investigated the upcycling of ABPs into biocomposites to replace conventional wood
products that use harmful urea-formaldehyde, phenolic compounds, and isocyanate resins. This paper evaluates the
upcycling of coconut ABP using nontoxic, renewable biobinders under comparatively low-energy conditions to create
affordable structural and cladding building materials. In this paper, we investigate the effects of processing variables
on board mechanical performance using the ASTM D-1037 standard, these are: (i) fiber processing, (ii) fiber-binder
ratios, (iii) pre-pressing methods, by which binders initially adhere to fibers, using established thermal pressing
conditions within each biobinders industry. Here, we compare the mechanical properties of medium-high density boards
(500-1200 kg/m3), made from coconut fibers bonded by coconut pith, soy protein, or fungal mycelium, to those of
common medium-high density wood and reconstituted wood products.
Keywords: agricultural waste, biobinder, coconut pith, soy protein, fungal mycelium, low embodied energy materials,
clean materials, biomaterials
Figure 1: Diagram of Processing Variables for Coconut Fiber - Biobinder Board Production

PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
INTRODUCTION
Figure 2: Global hot-humid map showing major coconut producing countries (FAOSTAT 2012 data)
Along the hot-humid belt, where half the world’s
population is concentrated, rapidly developing countries
that lack affordable building materials have not
capitalized on the potential of agricultural waste to serve
as an alternative building material stream. Grown all-year
round in 93 countries on 12.17 million hectares, the
coconut palm tree is the most economically cultivated
palm by small-scale farmers who make less than $2
dollars a day (FAO 2012). Globally the coconut is largely
cultivated for coconut water and dried copra meat
derivatives, generating 15-20 million tons of husks
annually (van Dam 2003). Coir fibers are natural fibers
extracted from the husk surrounding the seed of the
coconut. Relative to other agricultural waste, coir fiber’s
advantage is a result of its high structural lignin content
(38-44%) over twice that of other agricultural by-
products, high strength-to-mass ratio and low energy
conversion properties (van Dam 2004, Müssig 2012).
Recent advances in industrial and material science,
focused on improving coir extraction methods and
optimizing processing conditions, have resulted in coir
product applications in the particleboard, fiberboard,
insulation and composites industry. While the scope of
this paper is limited to the mechanical performance of
coconut husk derivatives, this work is part of a larger
body of research investigating coconut desiccant building
materials as moisture buffering systems.
Since the late 19th century, competing wood and
reconstituted wood industries have been dominated by
toxic, petroleum-based urea-formaldehyde and other
formaldehyde condensed adhesive binders that are
responsible for the off gassing of volatile organic
chemicals within indoor environments (VOCs) (Brown
1999, Jensen et al 2001). Due to the negative impact of
such material emissions on human respiratory health
(Krzyzanowski et al. 1990, Garrett et al. 1997), air quality
regulations and wood industry standards are rapidly
changing to limit the use of such binders.
Coupled with this growing interest to develop renewable
non-toxic binders, and progress within the agriculture
industry to expand nonfood by-products into growing
markets, this paper investigates the performance of agro-
based waste material resources derived from renewable
protein and lignocellulosic biopolymer resources. The
aim of this paper is to evaluate the mechanical strength of
coconut fiberboards based on the use of nontoxic,

PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
renewable biobinders to form competitive reconstituted
board products at low-energy conditions. The biobinders
under investigation comprise of (i) pith, found naturally
between coconut husk fiber walls comprising 70% of the
coconut husk (van Dam 2004) (ii) proprietary soy protein
binder from e2e materials and (iii) proprietary fungal
mycelium binder from Ecovative Design.
MATERIALS AND METHODS
Extensive research on coconut pith cross-linking
behaviour at lower temperatures (~135°C) and pressure
(<350psi), relative to the reconstituted wood industry, has
been attributed to the dehydration and curing of lignin
resulting in thermosetting behaviour during thermal
pressing (Varma et al. 1986, van Dam et al. 2004, Greer
2008). Previous research on coconut pith binder has
investigated the 100% substitution of synthetic resin for
medium density fiberboard production (van Dam et al.
2003, Snijder et al. 2005), pith particleboard production
(Greer 2008) and high pressure laminate production
towards the reduction of phenolic resin content
(Glowacki et al. 2012).
The soy adhesive resin from e2e Materials consists of
cross-linking agents and defatted soybean flour, obtained
by grinding soy flakes after hexane extraction from soy
oil, which react to provide a rigid thermoset binder
(Rasmussen et al. 2011, Netravali & Govang 2013, Zhang
et al 2014). Ecovative’s proprietary binder makes use of
mycelium, the vegetative state of fungi in the phylum of
Basidiomycetes, to provide structural binding. The fungal
vegetative tissue (mycelium) propagates and binds to the
coconut coir fibers as it grows into an interconnected
fibrous network. The mycelium derives its network
strength from chitinous cell walls, imparting high elastic
moduli and high flame retardance and low thermal
conductivity (Pelletier et al. 2013).
Coconut Husk Fiber Processing
Coconut coir fibers were obtained from Rolanka
International, a leading coconut supplier in Atlanta, USA
that imports coconut husk derivatives from Sri Lanka.
Prior to shipping, coconuts husks obtained from Rolanka
undergo ‘wet retting’, a process where husks are cured in
fresh water for three months resulting in dark brown
coconut fibers. The highest grade of coconut fibers,
bristle coir, composed of longer fibers with higher tensile
strength was used for fiberboard production. Two forms
of fiber products were investigated, including loose
bristle coir fibers and a non-woven coir mat. Both fiber
products were stored in a dry environment at room
temperature. The length of loose bale fibers ranged from
15-30 cm. Non-woven coir mats were made using needle-
punch technology to form a uniformly dense of 1.2 kg/m3.
Long fibers were cut into smaller length of 1-2cm by hand
for physical characterization tests. Fiber pore sizes were
measured by a FEI 3D Versa Environmental Scanning
Electron Microscope. Hammermilling, an industrial
process of cutting down coconut bristle fibers using a
series of small hammers, employed pneumatic assisted
ECO-HMA Colorado Mill Equipment. Resultant fiber
lengths were controlled using a milling screen of 0.25”
and 0.5” mesh sizes, yielding a range of fibers between 3-
20mm and 20-40mm respectively.
Biobinder and Fiber Substrate Preparation
Coconut Pith
Two types of pith were obtained from coconut husk
suppliers including compressed pith from Rolanka peat
blocks and loose, uncompressed pith particles from
Ecofibers Ghana Ltd, a leading coconut supplier in
Ghana, West Africa. The raw pith mixture is comprised
of a wide range of particles, including parts of the inner
coconut shell that were not separated from husk during
milling operations. Pith particles were sieved using a
stainless steel wire cloth to remove mixture impurities
and control particle sizes to 1000μm and 350μm. Pith
binder and bristle coir fiber masses were measured using
a mass balance according to desired fiber to binder ratios.
Pith and fibers were prepressed into sheets before thermal
pressing conditions listed in Table 4.
Table 1: Pith binder particle size, fiber substrate characteristics
and fiber: pith binder ratios
_____________________________________________
Board Biobinder Fiber Length Binder %
# Size (μm) (mm)
_____________________________________________
1-3 1000 3-20 50%
4-6 350 3-20 50%
7-9 1000 3-20 50%
10-12 1000 20-40 50%
13-15 1000 3-20 30%
16-18 1000 3-20 50%
19-21 1000 3-20 70%
22-24 1000 3-20 90%
_____________________________________________
e2e Materials Soy Protein
e2e Materials soy resins are provided in dry and wet resin
mixture; the dry powder resin mixes well and adheres to
short loose fibers. A known mass of dry soy protein mix
and coir fibers are mixed uniformly using a HCM 450
mixer according to fiber-binder ratios (refer to Table 2).
Using the wet resin method, the non-woven mats were
batch soaked in a bag with resin water mixture. Excess
liquid is squeezed off and open-air dried or with fan-
assist.

PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
Table 2: Soy Protein Dry/Wet Resin, fiber substrate
characteristics and fiber: soy binder ratios
_____________________________________________
Board Binder Fiber Length Binder %
# Type (mm)
_____________________________________________
25-27 dry resin 3-20 50%
28-30 dry resin 20-40 50%
31-33 wet resin non-woven mat 40%
34-36 wet resin non-woven mat 50%
37-39 wet resin non-woven mat 60%
_____________________________________________
Ecovative Mycelium Binder
The incubation profile for mycelium growth on coir fibers
was determined by researchers at Ecovative that took into
consideration the nutritional composition, weave type
and density of the coconut substrate as well as the
required temperature and humidity conditions during
incubation. Prior to incubation, coconut fiber substrate
was sterilized using 3.5% hydrogen peroxide, or
autoclaved (120°C, 15 psi for 55 minutes). Incubation of
coconut fiber substrate with mycelium occurred over a
period of 7 days within a polyethylene bag within a
temperature and humidity controlled chamber.
Nutritional augmentation of sterilized micronutrient mix
WB N007, developed by Ecovative, was used to add
sufficient carbohydrate and trace minerals to naturally
deficient coir substrate. After growth period, coconut
fiber-mycelium mixture was left to dry in the open or
heated to stop further growth.
Table 3: Fungal Mycelium, fiber substrate characteristics
_____________________________________________
Board Biobinder Fiber State Fiber
# Type Treatment
_____________________________________________
40-42 mycelium bagged, long fibers H202
43-45 mycelium bagged, short fibers H202
46-48 mycelium non-woven roll H202
49-51 mycelium non-woven roll autoclaved
_____________________________________________
Thermal Pressing Conditions
Temperature, pressure and duration conditions for
thermal pressing have been well understood and
optimized within each biobinder industry (refer to Table
4).
Table 4: Thermal Pressing Conditions for each biobinder
_____________________________________________
Binder Temp Pressure Time Source
# (°C) (psi) (mins)
_____________________________________________
Pith 135-150 350-500 8 FAO2003
Soy 110-130 350-500 6-8 e2e
Mycelium 165 350 5 Ecovative
_____________________________________________
Flexure Testing
After pressing, boards were allowed to cool down in a
metal jig at 20°C and 50% relative humidity. Three
samples were cut from the central region of each ¼” thick
pressed fiberboard into 2” x 8” testing specimens. The
span for each test was 6” and loaded at the center of the
span with a 5kN load cell. As stipulated by ASTM
D1037, the speed of the load is applied at a uniform rate
of 0.12-0.12 in/min (3-5mm/min) depending on thickness
of the specimen. The dimensions and weight of all three
test specimens were determined using a vernier caliper
(accuracy ±0.3%) and an analytical balance (accuracy of
not less than ±0.2%. The oven-dry mass of the sample
was, obtained after drying a specimen at 103±2°C until a
constant weight is reached.
The load-deflection data was recorded by an Instron
testing machine until the maximum load is achieved.
Testing was performed in replicates of three and
deflection was measured at the mid-span point using a
tensometer attached to the base of the testing jig. The
modulus of rupture and apparent modulus of elasticity
were calculated for each specimen using the following
equations:
(1) (2)
Where E = apparent modulus of elasticity, psi (kPa)
L = length of span, mm,
b = width of specimen, mm,
d = thickness of specimen, mm,
∆P/∆y= slope of straight line portion of the load
deflection curve (N/mm)
P= maximum load (N)
Rb = modulus of rupture, psi (MPa)

PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
Calculation of Strength - Cost Performance Ratio of
Coconut Fiberboards
The cost of coconut fiberboards made from biobinder
units are compared to wood and reconstituted wood
products. The cost per unit is based on the cost of raw
materials, including coconut fibers and biobinder, and
production costs that include biobinder, energy and labor
rates informed by manufacturing partners, e2e Materials
and Ecovative. The price of coconut fibers is assumed to
be USD $0.38 per pound, which is an average cost from
a survey of suppliers. The board density is determined
from the optimum mechanical performance for each
biobinder. In evaluating the strength – cost performance,
in accordance standard material property
characterization, which takes into consideration the
influence of inflation and units of currency, the formula
relative cost per unit volume is used. The cost of steel is
assumed to be USD $0.30/kg.
CvR = Cost/volume of material = Cost/ kg x density of material
Cost/volume of mild steel rod = Cost/kg x density of mild steel rod
RESULTS AND DISCUSSION
Coconut Fiber and Pith Morphology due to Husk
Processing
Micrographs of coconut fibers had porous ‘tube-like’
10μm openings with an internal matrix of smaller tube-
like pores. Compressed and uncompressed pith showed
significant differences in their surface area and surface
geometry. While compressed pith showed comparatively
ordered pores of openings between 30-40μm, loose pith
binders had tissue-like pore sizes resulting in an
advantageous increased varied, surface area. As a result
compressed pith resulted in insufficient binding between
coconut-pith layers.
Figure 4: SEM Micrograph of (a) Rolanka Bristle Coir Fiber
with remnant pith tissue (b) Openings in Rolanka Bristle Coir
Fiber Surface (c) Uncompressed Pith Tissue from Ecofibers (d)
Compressed Pith Tissue from Rolanka
Effect of Fiber Length and Mat Density on Flexural
Strength
Coconut fiber length played a critical part in determining
contact area of fibers with the biobinder. Longer fiber
lengths resulted in larger gaps in the fibrous matrix
resulting in the settling of pith and soy at the bottom of
the fiberboard matrix during pressing and a highly non-
uniform distribution of binder across the fiberboard
section. For the soy biobinder, the non-woven needle-
punched mat demonstrated the highest flexural strengths,
while the longer fiber length of 20-40mm demonstrated
higher MORs than 3-20mm.
Fungal mycelium growth largely did not occur
throughout loose fibrous bags of 3-20 and 20-40mm coir
mixtures. Added water and supplement nutrient solution
to aid mycelium growth settled at the bottom of bags.
Inoculation of coconut mats in rolls with higher
nutritional profile, demonstrated significantly uniform
growth. While this method was successful, autoclaving
was necessary to ensure the absence of any competing
microbial activity that would result in mold development
during growth period. Hydrogen peroxide sterilization
was not effective and resulted in growth of mold in
segments of the coconut mat substrate. The uneven
density of the coconut fiber mat also resulted higher
growth of mycelium in denser regions which higher MOR
performance. Therefore quality control of the coconut
mat substrate’s density is critical to mycelium board’s
mechanical performance. The difference in MOR values
between the most and least dense coconut-mycelium
fiberboards were approximately five-fold.
Figure 5: Ashby Chart Comparison showing Coconut board
Flexural Strength over Density

PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
Effect of Fiber-Binder Ratios on Board Mechanical
Properties
Figure 6: Graph showing Increasing Binder Ratio on Board Modulus of Elasticity and Modulus of Rupture
Fiber binder ratios were seen to play the most significant
role in the increase of board stiffness and strength. While
increase of pith ratio from 30% to 90% demonstrated an
approximate 300% increase in flexural strength, its MOE
increased form 170-1840 MPa. Within fiberboards
bounded by soy resin, where recommended binder ratios
are close to 50%, small increases of binder ratio from
50% to 60% showed almost a doubling of flexural
strength.
Mechanical Performance and Economic Cost
Comparison Coconut Fiberboards with Competing
Products
Coconut fiberboards made from soy binders offered the
best resistance to deformation (42.4MPa) per unit cost,
relative to pith and mycelium bounded boards. However
the cost of processing raw coconut pith binder ($0.09/kg),
which eliminates the cost of pre-treatment like
sterilization, wetting and drying, cost half that of soy
processing and mycelium biobinders.
Figure 7: Ashby Chart Comparison Young’s Modulus over
Relative Cost per Volume

PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments, 11-13 July, 2016
CONCLUSION
The mechanical performance of coconut fiberboards and
biobinders show potential to compete across engineered
wood markets, particularly in the low to medium density
market. Continued studies optimizing thermal pressing
conditions and more efficient fiber-binder contact pre-
processing show potential for high-density board
applications if the cost structure of production remains
closer to the costs afforded by coconut pith processing
costs. Further studies investigating promising pre-
processing and biobinder preparation techniques, such as
open air-drying of wet biobinder on non-woven coir mats,
shown in the soy-biobinder experiments, show high
potential to improve the mechanical performance in pith
bounded boards. However while the assumption was that
uncompressed raw pith material cost the least (USD $0.86
per kg), relative to the e2e Material’s soy binder (USD
$0.90) and Ecovative’s mycelium binder (USD $0.97),
the transport of loose, uncompressed pith material from
source contexts to manufacturing facilities needs to be
considered. Potential opportunities to drive down
production costs, could involve the substitution of
biobinder and fiber components with cheaper agricultural
by-product particle-based materials. Further research into
coconut fiberboard coatings and emerging bioresin
surface treatments need to be explored in the context of
high humidity and pollutant exposure conditions,
common in hot-humid urban environments.
Today the cost of agricultural waste like coconut fibers
are still 2-3 times more expensive than raw material
feedstock for the engineered wood industry, including
wood shavings and saw dust. While coconut fiberboards
can be competitive with low to medium density products
on the market today, market projections need to capitalize
on the unique properties of coconut fiberboard towards
other building material applications such as thermal,
acoustic and low-energy 3D molding that render such
products competitive within high-value applications.
ACKNOWLEDGEMENTS
The authors wish to thank Clayton Poppe & Michael
Rowell (e2e Materials), Mr. Ali Achilles (Ecofibers
Ghana) and Jeff Betts, Greg Tudryn, Courtney Hart and
Gavin McIntyre (Ecovative).
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