RECYCLING OF POLYURETHANE FOAMS : A STRATEGY
IN WASTE MANAGEMENT AND CONTROL
BY
T.E.ODETOYE
Department of Chemical Engineering,University of Ilorin, PMB 1515, Ilorin, Nigeria.
ABSTRACT
Recycling of polymer materials such as polyurethane foam is one of the needed strategies to
combat the menace of pollution in our environment. Pollution has been a consequence of
ever-increasing massive quantity of wastes generated from household and industrial
activities, posing a global challenge to man and the environment.
Recycling can also be used to conserve natural resources and reduce the consumption of
fresh raw materials therefore having an overall effect on reducing unecessary generation of
waste from production processes.
In Nigeria today, recycling of polyurethane post consumer product as a means of waste
reduction in our society is still grossly underutilised.
This paper examines the current trend in recycle as a means in waste management and
focuses on various methods of recyling polyurethane foams considering their application(s)
to the Nigerian situation.
Keywords: waste management; polyurethanes; recycle
Telephone number: +234-8054763390
E-mail address: todetoye@yahoo.com
1.
INTRODUCTION
of such (Akinkurolere and Franklin, 2005;
Waste management has been a major
Ezeronye, 2000; Longe & Williams, 2006;
challenge in the Nigerian Society as well
Ossai, 2006).
as in most African countries owing to the
In Nigeria today , the municipal solid
dual problem of increase in waste
wastes which are garbages generated by
generation as well as the poor management
individuals, firms and organizations
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Nigerian Society of Engineers, ABUJA, 2010
consisting of packagings, clothings,
Day to day open incineration of wastes
plastics, newspapers, batteries, funiture,
generated has also caused pollution which
ceramics, polyurethane foams, etc., have
has brought about the depletion of the
been mainly disposed by incineration and
ozone layer as a result of green house
land fill as is the common practice in many
gases emission. These forms of pollution
other countries (Miller, 2000; Yanyin,
resulting from poor waste management
2002).
have been regarded as major factors
However,a lot of pollution problems are
leading to climatic change all over the
actually associated with this system of
world in recent times. For these above and
waste diposal in the sense that most dump
many other reasons a drastic step has to be
sites actually pose health hazards to the
taken to put the situation under control
entire populace in the vicinity.
and protect our dear environment.
Nigeria is plagued by the existence of
Consequently, in the developed world
numerous waste dump sites dotting the
,concerted efforts have been directed
urban landscape of the cities
towards minimizing wastes through
(WAMASON, 2008).
reduce, reuse and recyling of post
The necessity of improving our waste
consumer products of various industries
management is more basic for many
with collection centres for specific wastes
reasons ranging from that of community
like polyurethane foams and other post
health to provision of essential amenities
consumer products (PURR,U.S.A., 2005;
like potable water. Pollution of ground
Recyclers world, 2010: Yanyin,2002).
water needed to be avoided since over 75%
Therefore, it is more pertinent to
of the Nigerian populace depend on
judiciously minimize the quantity of waste
surface or individually mined ground water
generated by recyling in a relatively low
as sources of drinkable water
income country like Nigeria. This enables
(WAMASON, 2008).
us to harness the attending benefits in term
Much more, potential farmlands which
of the effects on the community health as
could have been utilised alternatively to
well as the process economics in the
alleviate the problem of food shortage are
industry capable of indirect positive effect
being encroached upon day by day because
on poverty alleviation.
of the increase in the wastes generated.
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Nigerian Society of Engineers, ABUJA, 2010
However, practices to reduce, reuse or
Primary or close loop recycling involves
recycle has neither received widespread
conversion of post-consumer waste
awareness nor implementation due to
materials into new products while
various reasons such as; lack of
secondary or open-loop has to do with
information on the need to minimize
converting the waste materials into entirely
wastes, lack of information on the benefits
different products.
of re-use, reduce and recycle
One of the advantages that can be derived
(Akinkurolere & Frankling, 2005)
when materials are recycled is the decrease
in raw material input, because using recycled
2.
Recycling as a Method of Waste
material will reduce the amount of new
Management
material needed to manufacture a new
Recyling is one of the waste management
product , reducing about 20-90% virgin
measures that can be effective in the bid to
material consumption in primary recyling
conserve our natural resources as well as
and up to 25% virgin material consumption
save our deteriorating environment.
in secondary recycling (Yanyin 2002).
Recycling has been defined as “the process
Recycling also promotes significant
through which materials previously used are
reduction in quantity of resources such as
collected, processed, remanufactured, and
utilities (water usage and energy) as well
reused” (Schultz et al., 1995).
as in air pollution created during
In actual fact ,waste is the other side of
production processes, lowering green
production because garbages/solid wastes
house gases emissions compared to that of
can be regarded basically as a waste of
virgin production.
raw materials and energy in the light of
Another advantage is that recycling, when
recycling (George, 2007).
used as a solid waste reduction and
There are two basic types of recycling
management strategy, minimizes the
(Behrendt and Naber, 2009; PURRC,
amount of wastes ending up at the dump
2005;Yanyin 2002);
sites and incinerators, hence, preventing

Primary or Close-Loop Recycling
useful materials from being wasted. Such

Secondary or Open-Loop
materials include polyurethanes which can
Recycling
be reused even at the end of their original
intended service life as funiture, shoe, car
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Nigerian Society of Engineers, ABUJA, 2010
upholstery component, etc. They can still
consisting of chains of organic units joined
be as valuable at the point when they are
by urethane links. Polyurethanes can be
ready to be discarded (CPI-ACC,2010) .
formed by reacting a polyol (a polymeric
alcohol with more than two reactive
3.
Polyurethanes
hydroxyl group per molecule) with
Polyurethanes are a major plastic materials
diisocyanate or polymeric isocyanate (e.g.
with an annual world production capacity
methylene diphenyl isocyanate, toluene
of over 12 million tons (Berendt and
diisocyanate) in the presence of suitable
Naber, 2009). They are polymers
catalyst and additives.
Polyol + Diisocyanate
Polyurethane Polymer + Heat
Polyurethane Consumption by End Use
Building &
Construction
Transportation
Funiture &
Bedding
Appliances
Packaging
Textile , Fibres
& Apparel
Fig. 1. Polyurethane Consumption by End Use Market in the United States (PURRC, 2005).
They can also be made from renewable
widely used in flexible and rigid foams,
source (Ogunniyi et al.,1998).They are
4
durable elastomers and high performance
Nigerian Society of Engineers, ABUJA, 2010
adhesives. Polyurethanes have found
refrigerators,vehicle upholstery,etc.
application in household as well as
However, the recyling of the post-
industrial products due to their various
consumer polyurethane products still
durable properties. Fig.1. shows
remains a challenge in most countries
polyurethanes consumption by end use in
(Behrendt and Naber, 2009; Knight,2006;
the United States market.
Yanyin,2002).
As the amount of waste generated is
However, in the developed world,
increasing day by day, polyurethane
recycling of post-consumer polyurethane
products have also found their way to the
products has been encouraged especially in
dump sites after serving their intended
Europe and the United States where it has
purposes, constituting waste diposal
been in existence for over 15 years
problem, much more, since they are not
(George, 2007; Recycle.net, 2010).
readily biodegradeable (CPI-ACC, 2010) .
Various effort are already being directed
towards the utilisation of this aspect of
4.
Polyurethane recycle as a strategy of
waste management
Significant portions of polyurethane foams
recycling in waste management strategy
(Polyurethane Recyle & Recovery
are used in the production of funiture, car
Council,U.S.A.,2005; Knight,2006;
upholstery, in vehicle assembly factories,
Yanyin,2002).
footwear and bedding industries, to name a
The form of polyurethane recycle system
few. They make up to
existing in Nigeria, with our considerable
5% of all plastics, and are made from
number of foam industries (ADCB UAE,
petrochemicals (Knight,2006). Waste
2010) is mainly that used during the
generated from such uses sometimes
production process whereby, off
comes as a mixture with other polymer
polyurethane products, shaping and cutting
materials such as nylon, polyester,
wastes are ground and re-used as
cellulose, films, glass fibres which can be
component of another production output.
separated for the purpose of
On the contrary, pre-consumer, recycling
recycle.Waste-polyurethane scraps can be
is a popular waste minimization method
obtained from discarded materials by
used by foam manufacturers all over the
collection from soles of shoes, parts of
world.They are already into the business of
toys, parts of funiture, parts of
recycling wastes generated from cutting
5
Nigerian Society of Engineers, ABUJA, 2010
and shaping of foams in the industry i.e.
which is capable of improving the foam
pre-consumer polyurethane wastes
manufacturing process economics
(Polyurethane Foam Association,1994).
(Cannon, 2009).
These polyurethane scraps have been
Polyol has been recovered from waste
successfully processed into useful products
polyurethane by hydroglycolysis
(Gebreselassie et al. 2001), thereby
(Brawslaw and Gerlock,1984). The polyol
generating revenue, reducing raw material
thus recovered was purified by liquid-
cost, and alleviating solid waste disposal
liquid extraction. The process was claimed
problems. Recycled pre-consumer
to produce a material capable of replacing
polyurethanes wastes are made into
as much as 50% of the virgin polyol used
bonded carpet underlay, they are used for
in high quality, low density polyurethane
the production of car seatbacks and head
foam formulations with a reasonable
rest where the physical and mechanical
process economics when no other markets
properties are less demanding (compared
exist for the waste foam material.
to car seat cushion).
Conversion of waste polyurethane
There is a an international niche market for
material was also done with the use of
recylcing both pre-consumer and post-
phosphonic acid diester as a degradation
consumer polyurethane foam scraps. Pre-
agent in the polyurethanes which was
consumer polyurethane sells for about
claimed (Troev,K., et al 1999) to be
0.80USD /kg in South Africa, 0.1 - 0.3
applicable for the preparation of useful
USD /lbs (recycle.net, 2010) in the United
polymers product with reduced
States, while Post-consumer PU scrap
flammability.
recently sells for about 0.24 Euro/ kg in
Another work(Gebreselassie et al. 2001)
Romania,Timis (recycle.net, 2010).
involves shredding of the polyurethane
waste into fluff having a particle size of
5.
Some Research works on Polyurethane
0.25 -1.0 inch and molding the material at
Recycle
elevated temperature and pressure such
Many researchers have investigated
that the foam exceeds its glass temperature
various methods of recycling
which occurs at 600-1200psi and 400-
polyurethanes wastes so as to provide
475oF. Then the hydrogen bonds in the
inexpensive raw materials for foam plants
hard segment of the polymer are broken
6
Nigerian Society of Engineers, ABUJA, 2010
under the elevated temperature and
Polyols obtained has also been used as
pressure. The bonds are then re-established
components in the preparation of binders
on cooling sometimes leading to chemical
for composites of high textural and
arrangement of the polar groups in the hard
flexural strength (Berndt and Naber, 2009).
segement. This method was claimed not to
Datta and Rohn, in 2007, investigated
require the use of a binder. The physical
thermal transitions and thermal stability of
properties of the resulting material was
polyurethanes and polyurethane
varied by controlling the mold
intermediates.
temperature, pressure and time so that the
However,some of the aforementioned
resultant product was tailored towards a
methods are yet to be adopted in the
particular application.
industries, because they have not been cost
Hulrich et al, in 2004, reported an emission
effective.
free recyle process which involves heating
Polyurethane manufacturing companies are
the waste material with glycol mixture to
also rising up to the challenge. A process
obtain polyol that can be completely
to glycolyze mixed polyurethanes has been
reused in the manufacture of rigid
developed by Troy Polymers,
polyurethane. The process was claimed not
Inc.(PURRC,2005). The new
to be sensitive to varing product mixes.
polyurethanes produced from waste scraps
Attempts (Kang, 2006) had also been made
retained most of the properties and
to use waste polyurethane as road and
functionality of the original materials.
building construction materials. An elastic
Equipment manufacturers are already
permeable pavement comprising waste-
facing the challenges of designing new
polyurethane chips for use on new roads
equipment and retrofitting the existing
and pavings was prepared using a binder
ones to recycle polyurethane wastes.
specially developed to secure the binding
Cannon has recently designed a new
between an upper waste-polyurethane chip
Cannon Filler Injection Kit (Cannon,2009)
layer and a lower permeable concrete
which was claimed to reduce wear
layer.The pavement was reported to have
problems in existing machines and which
excellent strength, durability, elasticity and
can use up to 7% of the recycled material
permeability suitable for sporting activities
in the new polyurethane foam
walking and outdoor exercises.
7
Nigerian Society of Engineers, ABUJA, 2010
manufactured without affecting the
Main Methods of Recycling
mechanical and physical properties.
Polyurethane Foam
Research efforts are also towards
The major ways of polyurethane foam
converting post-consumer polyurethane
recycle are by mechanical and chemical
waste into valuable energy like electricity
processes (Berndt and Naber, 2009;
by modern technology incineration (CPI-
Cannon, 2009; Center for the
ACC,2009; WAMASON, 2008).
polyurethanes Industry(CPI)- American
Chemistry Council, 2010):
POLYURETHANE
RECYCLE
METHODS
CHEMICAL
PROCESS
MECHANICAL
PROCESS
REGRINDING
REBONDING
ADHESIVE
PRESSING
COMPRESSION
MOULDING
GLYCOLYSIS
Fig. 2.Polyurethane recycle methods
Uses of Recycled Polyurethanes Scraps
Polyurethane wastes can be used for
 Pump housing
special products based on the extra-
 Automotive parts
ordinary properties that they exhibit by
 Tyre cover
using the unique recycling proceedures.
 Car seatbacks
The products generated have found
 Car head rest, etc.
application in (PFA,1994; CPI,2009);
PYROLYSIS
HYDROGENATION
 Paving material
6.
Lessons From Other Countries: New
 Bonded carpet underlay
 Stuffings for pillows
Zeland, Sweden,
 Packagings
Singapore,Canada,United States, etc.
 Sound insulation
(CPI-ACC,2009;George, 2007; Knight,
 Mats
2006;Yanyin,2002;)
8
Nigerian Society of Engineers, ABUJA, 2010
HYDROLYSIS
Presently in the United States of America,
In Singapore and Sweden, they recognized
polyurethane recycling business has been
that efforts at instilling environmental
encouraged to the extent that the demand
consciousness need to start early in order to
for flexible polyurethane foam wastes now
have long-term effects on children
exceeds the supply through domestic scrap
(Yanyin,2002).Therefore, environmental
recovery.They now engage in importation
consciousness has been included in their
of scrap polyurethane from Europe thereby
educational curricula with a view to
contributing to the global polyurethane
producing a next generation of
wastes minimisation.
environmentally conscious citizens.
In the United States and Canada, Recycled
New Zealand (Knight,2006) embarked on
Polyurethane Markets Database of contacts
a Zero Waste Programme involving
and companies who recycle polyurethane
investigation of several possibilities for
have been compiled to enable the trade to
local foam collection,including the
thrive more.The post-consumer mattress-
feasibility of setting up collection centres
recycling programme has also been
for citizens to drop off materials
developed in the United States and
containing polyurethane foam.
Canada.
“Currently, there are 89 Waste -To-Energy
European markets are rapidly developing
facilities in the US that dispose of 81, 000
innovative uses for polyurethane wastes to
metric tonnes of solid waste per day and
provide
generate 2700 MW of electricity (enough
high-value products for their consumers.
to
“In Singapore, one of the strategies was to
WAMASON, 2008
improve the operational aspects of recycling
Various
schemes
improving
waste management is going on around the
convenience like placing recycling bins in
globe on polyurethane recyling and other
more accessible
strategies of waste minimization. Now the
by
(Yanyin,2002).
9
providing
and
and visible
location”.
supply
2.3
million
homes)”
research and developement on
big question is- Where are we in Nigeria?
Nigerian Society of Engineers, ABUJA, 2010
•Industrial Scrap
•Post Consumer Polyurethane
•Collection,Processing for Export
P O LY U R E T H A N E
WASTES
Recycle
• Generation of Electricity
Energy
Recovery
•more
research to
be done
Other Uses
Land Fill
To be
minimised
Fig. 3.Effective Polyurethane Waste Management
CONCLUSION
More efforts should be made by the Government through the Federal Ministry of
Environment towards a cleaner Nigerian environment as we strive to acheive vision 20:2020
Nigeria as the giant of Africa should take a leading step and set the pace for others to follow
in this bid to rescue our environmement through emphasis on recycle,borrowing a leaf from
UK., U.S. A., Canada, Singapore, Sweden, etc
With the Nigerian population and increasing urbanization, for the problem of poor waste
management that bedevils Nigeria and most of the African Countries to be overcome, all
hands should be put on deck in order to achieve a sustainable development in waste
management
10
Nigerian Society of Engineers, ABUJA, 2010
In a nutshell, if recyling of post-consumer polyurethanes and other materials are given the
much desired attention, recyling will be one of the appropriate strategies to improve waste
management as well as to combat the problems of pollution and global warming in Nigeria.
RECOMMENDATIONS
 Some of the beneficial
educating the masses about the
programmes/measures put in place
attending benefits to our
to manage waste in Nigeria,
environment
already launched by the Federal
 Public Private Partnership
Government should be reviewed
enterprises in waste management
and reactivated to emphasize
should be encouraged
reclying of polyurethanes and other
post consumer products .
 Government and Non-
 Federal Ministry of Environment
should promote recycling from
source, sorting the waste from
Governmental Organizations
homes, factories, establishment or
(NGOs), professional bodies e.g.
at collection points before getting
NSE,WAMASON, should launch
to dumpsites.
recycle campaigns and champion
 “Scavengers” should not be seen
the cause of recyling of
as out-casts but should be
polyurethane and other post-
encouraged by creating recycle
consumer products.
agency where they can be
 Recycling Agency should be
absorbed, as they contribute to the
established to create collection
recycle process by sorting the
points for polyurethane and other
rubbish before it gets to the
specific materials such as; plastic,
dumpsites .
paper, metal, glass, wood, and
 Useful and accessible waste
rubber in our community, creating
generation and recyling data should
recycling bins in accessible
be made available through more
locations.
research.This is needed to monitor
 A sense of social responsibilty
should be inculcated into the
11
citizenry concernining recycling,
the progress of waste management
in Nigeria.
Nigerian Society of Engineers, ABUJA, 2010
 Data base of existing recycling
agents in Nigeria should be created.
 There should be a review of
relevant legislations, policies and
Braslaw, J.and Gerlock, J.L. (1984)
Polyurethane Waste Recycle,Polyol
Recovery and Purification, Industrial
Engineering and Chemistry Process
Design and Development. 23(3), 552557.
regulation in order to promote
recycle (of polyurethanes and other
materials) as an important strategy
in achieving effective and
sustainable waste management and
control in Nigeria.
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Nigerian Society of Engineers, ABUJA, 2010