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COIR -TRADITIONALLY USED FIBRES FOR NEW CONSTRUCTION

APPLICATIONS

Conference Paper · June 2015

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 First International Conference on
Bio-based Building Materials

June 22nd - 24th 2015

Clermont-Ferrand, France

COIR - TRADITIONALLY USED FIBRES FOR NEW CONSTRUCTION

APPLICATIONS
E. Kürsten1*
1 University of Applied Sciences and Wood-Report GmbH, 30455 Hannover, Germany
*Corresponding author; e-mail: ek@wood-report.de

Abstract

Coir is a byproduct of the production of coconuts. In Europa it has been used for insulation
purposes since nearly 100 years. This paper explains where this bio-based material comes from,
what building products are being made from it nowadays and why it makes sense to use this
resource more intensively in the future even in Europe.

Keywords:
coconut production; coir; fibre processing; coir ply; particle boards; insulation materials

1 INTRODUCTION bottle gourd and drumstick” [Mohapatra, 2007]. The

On the way to a sustainable future based on renewable palm stems can be used to grow climbers like black
resources fibres from tropical countries can be part of pepper and betel, and cattle grazing is also widespread
the solution. Especially coir, the fibres which are under coconut. “There is much evidence in coconut
extracted from the husks wrapping the coconut are of growing countries that coconuts are inter-cropped with
special interest because they are available in other crops thus increasing the productivity of the
abundance as a byproduct of the production of copra. coconut and of the crops grown under it and thereby
Especially in the construction branch there are some increasing potential revenue to smallholders with
possibilities to make much more use of this resource. access to the coconut resource.“ [Warner, 2007]
Thereby, on the one hand adverse impacts on the
environment can be reduced, and on the other hand
employment and additional income for rural areas in the
tropics can be generated.

2 COCONUT PRODUCTION
The origin, biology and importance of the coconut
(Cocos nucifera L.) has been described extensively by
Prabhakaran Nair [2010]. He explains that “in the state
of Kerala, the life of the people is woven around the
coconut palm. The endocarp is everyday fare in the
kitchen—scrapped or ground to extract the milk and
used in all of the culinary specialities of the people.
Coconut oil is used for both body massage and for the
hair, water from the tender coconut is used as a very
nourishing drink, leaves are used for thatching homes,
and when dried, coconut is used as firewood.” Fig. 1: Cattle grazing in a young stand of coconut
Not only the possibilities to make use of the coconut palms in Tamil Nadu (India)
palm are characterized by a great deal of variety, but
also the options to mix it with other crops: Even in case
of an optimal plant density of 150 - 180 palms/ha plenty In India, the “Tree of Life” is mainly grown by
smallholders with 98% of the holdings of size less than
of light is available for other vegetation, especially
2 hectares. In the other main coconut producing
during the first decade after planting and between age
countries in Asia - Indonesia, Philippines, and Sri Lanka
25 and age 70, when the coconut production finally
decreases too much. In the Indian state of Odisha, e.g. - the situation is similar, with smallholder percentages of
the coconut area between 71% and 97% [Arancon
“the interspaces are covered with fruit crops like
1997]. In total, these four states in 2005 had a share of
banana, papaya, pineapple and vegetables like okra,

1
76.5% of the world´s 10.6 M ha land under coconut Both types can also be blended or just not separated.
palms. Then they are called mixed brown fibres (or decorticator
fibres) [Ranasinghe 1980]. The production process of
the latter has recently been observed in Tamil Nadu
(India):
The husks are firstly fed into a crusher with spiked,
fluted or grooved rolllers. Then the fibres are sprinkeled
with water to start a short retting process of a few hours
or days. Thereafter the material is conveyed through a
Indonesia Philippines India Brazil Sri Lanka revolving screener where the pith is separated from the
Fig. 2: Coconut production of the top 5 producers fibres. At the end the coir is laid flat to dry in the sun,
(Average 1993 – 2013) [Source: http://faostat3.fao.org/ and then finally baled or twisted to ropes for the
<05/01/2015>] transport to the customer. - In general it can be stated
that the quantity and quality of coir could be much higher
if improved technologies would be more widely applied.
3 COCONUT PROCESSING From 1000 coconuts it would be possible to extract 10
Coconuts are often harvested immature just to use the kg of coir [FAO 2014].Husks are composed of 70 per
water inside as a drink. In this case the coir is difficult to cent pith and 30 per cent fibre on a dry weight basis.
collect and process the husks as they become a kind of The ratio of yield of long, medium and short fibre is on
household waste. Accordingly only husks left over from average 60:30:10. The average fibre yield can vary: In
the production of copra are available for further uses. the south of India and Sri Lanka, for example, where the
3.1 Separation of husks and kernels best quality fibres are produced the average yield is 80-
90 g fibre per husk. Caribbean husks, by contrast, are
At first, the husk has to be separated from kernel either relatively thick and may yield up to 150 g of fibre [van
by a cutlass, by a manual dehusker or by a dehusking Dam 2002].
machine.
Coir fibres measure up to 35 cm in length with a
diameter of 12-25 microns [FAO 2014] and have a high
content of lignin (about 45%).

Fig. 3: The raw material: Husk of ripe coconut with

brown fibres
3.2 Coir processing and fibre qualities Fig.4: Solar drying of coir at the end of the production
Traditionally in Sri Lanka and in coastal regions of India process.
the husks firstly undergo a retting process, preferable in 3.3 Use of residues from coir production and
saline water for some 6 to 12 months to get the fibres coconut palms for construction purposes
more easily seperated. That is often done by beating
The main byproduct of the coir production is coco peat
with wooden sticks. The resulting coir is of a light colour
and called ”white fibre”. It is soft and can be spun to yarn (pith), a mixture of the non-fibrous paranchymatois
which is then used for making various products such as “corky” connective tissue linking the fibres, short fibres,
and dust. Currently it is mainly used as a soil
mats, mattings, carpets and rope. White coir therefore
conditioner. But, as the pith residue contains a relatively
is also called ”mat fibre”. The extraction and spinning of
high amount of lignin, it could be used as a strong and
white coir fibre is essentially a labour intensive manual
process carried out on a cottage industry basis. stable resin-like adhesive to produce coir boards (see
4.2) [van Dam 2004].
The other main type of residues are the nut shells. Like
For construction purposes only ”brown coir fibre” is many other organic residues they could be converted to
applied. Here two types can be distinguished: particle boards.
• ”Bristle” which comprises of long stiff bristle Very special building products from coconut shells are
which is mainly used as filling for the brush parquet and wall panels developed by the German
industry and more expensive. company IN-PARKETT.
• ”Mattress” which are more medium and short
Of course, the lower and outer parts of the trunk of the
fibres which are more soft and mainly used for
coconut palm can be converted to sawn timber for
mattress filling and needlefelt pads of
construction and flooring.
innerspring mattress and upholstery.

2
And finally it has to be mentioned that the palm fronds 4.2 Particle boards
are traditionally used for making walls and roofs of Of course, every part of the coconut tree and its fruits
buildings in tropical countries. theoretically can be used for the production of particle
boards. As in many other countries, in Mexico coir is a
generally underutilized material. It has been estimated
4 CONSTRUCTION MATERIALS FROM COIR
that about 500 000 t of coir may be available there
4.1 Coir ply annually, of which only small quantities are, at present,
In 2001, in Bhuj (Gurarat / India) 500 shelters were built used to fill car seats and mattresses. – By a preliminary
to aid in the relief from an earthquake. The walls and study, the following „optimal“ combination of process
roofs were made of coir ply and protected from UV rays variables was found for “pure” coir particle board
by weather coat paints, respectively tiles. “The boards [Fuentes 1997]:
having good insulation properties have shown a Single layer, nominal density 0.65 g.cm-3 and 16 mm
temperature difference of 5 to 8 degrees when thickness; resin content 12%, temperature 150 ºC,
compared to the outside temperature.” In spite of the pressing time 9 min and pressure 3.5 N mm-2.
extreme climatic conditions in Gujarat they are said to
In addition, combinations of coir and other types of
remain without defects until today. Coir ply is basically
biomass are possible. E.g., in Thailand low-cost
a substitute for plywood, the most popular wood-based
insulation particleboards from mixtures of durian peel
panel in India. It is made from coir bonded by a phenol
and coconut coir have been tested. One finding was that
based resin. It is regarded as termite, insect and water
a high percentage of lignin content of coconut coir
resistant [Natureindia 2015].
increases the cross-link in particleboards. [Khedari
Tab. 1: Coir ply Test Results (BIS 14842 2000) 2004].
(Test data as per tests carried out by I.P.I.R.T.I. (Indian The fact that lignin can be used as a natural binding
Plywood Industries Research & Training Institute, material was the background for the development of a
Bangalore) [Natureindia 2015] simple and efficient technology to produce boards of
Density 748 Kg/m3 high strength and high density from whole coconut
husks, without the addition of chemical binders. “The
Moisture 6.50 %
board exhibits excellent properties, which are
Glue sheer strength 1720 N/mm2 comparable with or even superior to commercial wood
Water resistance (8hrs.boiling) No delamination based panels. The pressed coconut husk boards can be
handled with common wood working equipment for
Tensile Strength 2.,6 N/mm2
drilling and sawing, planing and polishing. Screwing,
Compressive strength 51.02 N/mm2 however, is only possible after pre-drilling and the board
Modulus of elasticity 6440 N/mm2 product is too hard for nailing.” [van Dam 2004]
Modulus of rupture 47.5 N/mm2
Nail holding power 50 kg
Screw holding power 245 kg

Fig. 6: Light coir insulation and construction board in

India
4.3 Insulation materials
Nature has designed coir as an insulation material for
the coconut kernel. The fibres protect the nut against
heat from intensive solar radiation and mechanically if it
falls to the ground. In addition, the fibres are durable
enough to fulfill its tasks even under tropical condition
with high humidity and optimal living conditions for
insects and fungi.
Accordingly, coir has been used successfully for
Fig. 5: Corrugated coir ply (phenol resin bonded coir)
insulation purposes since many decades. The cavity (>
as roofing material in Indial
30 µm) in the center of mature fibres [Delft University
Similar roofing materials which are considered as a low 2003] is a special advantage for heat and sound
cost alternative to corrugated galvanized iron and protection. In addition, the extremely low decomposition
asbestos cement sheeting, can also been made from rate makes coir especially suitable for the production of
short randomly distributed coir fibres in a cement matrix geotextiles [FAO 2014].
[Cook 1978].

3
Recently in a school in Würzburg (Bavaria) a coir impact The often mentioned environmental impact of the long
sound insulation has been found which remained distance transport – as compared to locally grown
completely intact since 1934 under a flooring, and could natural fibres (which would consume additional
be reused for the same purpose again. Especially under agricultural land) – is not really important: The consump-
floorings which have to carry heavy loads (industrial tion of primary energy (PE) for transport by a big cargo
buildings) and where moisture may be a problem coir ship is only 0.0472 kWh/t.km [Frischknecht 2011]. A
insulation (eventually with a natural latex impregnation calculation with a bulk density of 255 kg/m3 of the bales
and a density of 160/170 kg/m3) is a perfect solution. [Gittel 2014] and a distance of 12,000 km (from India or
[Gittel 2014] Sri Lanka to Germany) results in a PE consumption of
Based on long term experiences with the production of 145 kWh/m3 of coir. The PE consumption for the
coir mattresses the German company Gittel Triagwerke production of coir is 87 kWh/m3 [Sörensen 1997]. In total
GmbH recently developed a new type of coir insulation 232 kWh/m3 is much less than necessary for production
materials for thermal insulation of walls and roofs of wood fibre boards and most of the nonrenewable
according to DIN 4108-10. Its technical properties are materials (Table 2), even if the different thermal
[Gittel 2014]: conductivities are taken into consideration.
Density ρ 100-130 kg/m3 Table 2: Consumption of primary energy (PE) for the
production of different insulation materials [Dorsch
Thermal conductivity λ 0.042 W/(m . K) 2014]
Specific heat capacity c 1,700 J/(kg . K)
Origin Material PE-
Diffusion resistance μ 1 consumption
Construction material class B2 (normally flammable) (kWh/m3)
Hemp, Flax 40-80
Renewable Wood fibre (flexible) 50-100
Wood fibre (board) 600-1,500
EPS 200-760
Synthetic XPS 450-1,000
PUR 800-1,500
Bloated perlite 90-160
Mineral Rock wool 150-400
Glas wool 250-500
Even though the overall social and environmental
impacts of an increased use of the currently completely
underutilized potential of coir as fibre resource seem to
be positive in countries like India and Sri Lanka, it has
Fig. 7: Coir mats are extremely well suited for the to be kept in mind that the situation in the fourth most
insulation of the floorings, but also quite an interesting important producer country seems to be different: In
possibility for wall and roof constructions Brazil newly established coconut plantations
(sometimes on forest land) are being offered on the
4.4 Other construction materials
global capital market as high quality investment
Clay building boards reinforced by coir fibres are opportunities. “It’s now possible for you to invest today
available on the market. Coir can also be used for for an immediate annual yield of 12.12% based on
plaster base boards. current production.” [Simon 2013]
“In the long run two extreme scenarios for plant fibres
5 ECOLOGICAL ASPECTS use can be imagined: either they will foster the
development of Third World economy with added
An essential ecological advantage of coir is that it is just advantage for environment at planetary level, or they
a byproduct of copra. Therefore no additional land is will be a further natural resource exploited in a "cash
necessary for its production, in contrast to other natural crop" philosophy from multinational companies, with
fibres like hemp, flax, sisal, jute, and abaca. Today less negative impact locally and globally.” [Santulli 2005]
than 25% of the available coir raw materials in the four
most important Asian producer countries are being used
domestically or in the fibre industry (only in India and Sri 6 SUMMARY
Lanka) [van Dam 2002]. Most of the material is just
Mainly in tropical countries there have been many
burnt or used as mulch.
successful trials to develop construction materials like
In addition, coconuts are rarely grown in large mono coir ply, particle board and roofing sheets based on coir.
cultural plantations. As described above (2.) the
In Europe, coir has been used as an insulation material
prevalent smallholder production of copra in mixed
for many decades, but firstly due to cheaper materials
agroforestry systems can be regarded as ecologically
like rock wool, glass wool, EPC etc., and nowadays due
(and socially) much more sound than the competing
to the developments based on home-grown renewables
large scale plantation production of oil palms, soybeans
like hemp, flax and wood fibre it nearly felt into oblivion.
and rapeseed (see: [Warner, 2007]). An increased use
of coir means a value addition for the coconut growers The special properties of coir and the fact that is an
and provides them with an advantage in their underutilized and relatively cheap byproduct of the
competition with other plant oil producers. coconut production are good reasons to bring it back to
the minds of European architects and engineers.

4
 Against the background of a growing demand for arable particleboards from mixture of durian peel and coconut
land and timber on the one hand, and the need to create coir. Building and Environment 39 (2004), 59 – 65
more labour and income in tropical countries on the [Mohapatra 2007] Mohapatra, A.K., Bhola N.,Patnaik
other hand It may even have ecological and social R.K.; Agroforestry systems and practices in Orissa. In:
advantages to make a better use of this resource. S. Puri and P. Panwar, P., eds.; Agroforestry systems
and practices. New India Publishing Agency, New Delhi,
333-346
7 ACKNOWLEDGMENTS
[Natureindia 2015] www.natureindia.com <30/01/2015>
I want to thank Ramkumar Palanisamy (mpinger GmbH
/ Germany) and his brother Thigarajan Palanisamy (mp [Prabhakaran Nair 2010] Prabhakaran Nair, P.K.; The
coir / India) very much for the introduction to the Agronomy and Economy of Important Tree Crops of the
processing and use of coir they provided me. I am also Developing World. DOI:10.1016/B978-0-12-384677-
very grateful to Mr. Gittel (Gittel Triagwerke GmbH) for 8.00003, Elsevier Inc., 2010
sharing his long term experiences with the processing [Ranasinghe 1980] Ranasinghe, T.K.G.; Coconut
of coir insulation materials with me. processing technology information documents – Part 6
of 7 "Coconut fibre and coir products". Asian and Pacific
Coconut Community. UNIDO/IOD.377/Add.5, 1980
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