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Review
Progress in used tyres management in the European Union: A review
Maciej Sienkiewicz
⇑
, Justyna Kucinska-Lipka, Helena Janik, Adolf Balas
Polymer Technology Department, Chemical Faculty, Gdansk University of Technology, Gabriela Narutowicza Street 11/12, 80-952 Gdansk, Poland
article info
Article history:
Received 15 January 2012
Accepted 14 May 2012
Available online 9 June 2012
Keywords:
Waste tyres
Recycling tyres
Rubber recyclates
Used tyres management
abstract
The dynamic increase in the manufacture of rubber products, particularly those used in the automobile
industry, is responsible for a vast amount of wastes, mostly in the form of used tyres, of which more than
17 million tonnes are produced globally each year. The widely differing chemical compositions and the
cross-linked structures of rubber in tyres are the prime reason why they are highly resistant to biodeg-
radation, photochemical decomposition, chemical reagents and high temperatures. The increasing num-
bers of used tyres therefore constitute a serious threat to the natural environment.
The progress made in recent years in the management of polymer wastes has meant that used tyres are
starting to be perceived as a potential source of valuable raw materials. The development of studies into
their more efficient recovery and recycling, and the European Union’s restrictive legal regulations regard-
ing the management of used tyres, have led to solutions enabling this substantial stream of rubber wastes
to be converted into energy or new polymer materials.
In this article we present the relevant literature describing innovative organizational approaches in the
management of used tyres in the European Union member countries and the possible uses of waste tyres
as a source of raw materials or alternative fossil fuels.
Ó2012 Elsevier Ltd. All rights reserved.
1. Introduction
Worldwide, the amounts of used polymer products are increas-
ing by the year: most of them are used automobile tyres. According
to reports from the largest associations of tyre and rubber product
manufacturers, the annual global production of tyres is some 1.4
billion units, which corresponds to an estimated 17 million tonnes
of used tyres each year (RMA, 2009; JATMA, 2010; ETRMA, 2011;
WBCSD, 2010). China, the countries of the European Union (EU),
the USA, Japan and India produce the largest amounts of tyre
wastes – almost 88% of the total number of withdrawn tyres
around the world (JATMA, 2010). The dynamic growth in the
numbers of used tyres is well exemplified by the EU, where their
production increased from 2.1 million tonnes in 1994 to 3.3 million
tonnes in 2010, and the annual cost of their disposal in EU coun-
tries has been calculated at nearly 600 million euros (ETRMA,
2010a). The scale of the problem is magnified by the environmen-
tally dangerous dumps already in existence, where some 4 billion
tyres are being uselessly stockpiled (WBCSD, 2008). These dumps
are indeed a serious threat to both the natural environment and
human health because of the risk of fire and their being used as
a suitable habitat by rodents, snakes and mosquitoes (Naik and
Singh, 1991; Li et al., 2006).
Used tyres are a category of waste whose recycling is exceed-
ingly difficult. This is due to their highly complex structure, the
diverse composition of the raw material, and the structure of the
rubber from which the tyre was made. The technology of manufac-
turing rubber products is based primarily on the irreversible vulca-
nization reaction that takes place between natural and synthetic
diene rubbers, sulphur and a variety of auxiliary compounds. As
a result, transverse bonds connect the elastomer chains to form
the cross-linked structure of rubber. That is why rubber articles
are elastic, insoluble and infusible solids that cannot be repro-
cessed, as is the case with thermoplastic materials. Their recycling
therefore requires a high time and energy outlay and is based so-
lely on the mechanical, thermal or chemical destruction of the rub-
ber product; recovery of the raw materials used to produce them is
impossible (White and De, 2001). A conventional tyre is a product
with a complex structure and composition, which can be made
using various variants of high-quality synthetic rubbers, mainly
butyl rubber (IIR) or styrene-butadiene rubber (SBR), and natural
rubber (NR), along with a host of other compounds added to obtain
the final utilitarian form or the high mechanical strength of the
tyre. A tyre consists not only of rubber, which makes up some
70–80% of the tyre mass, but also of steel belts and textile overlays,
which give the tyre its ultimate form and utilitarian properties
(Pehlken and Müller, 2009; Ganjian et al., 2009). The presence of
these latter two components is a serious problem, however,
because they have to be separated from the rubber during tyre
recycling. Hence, to obtain a new product derived from automobile
0956-053X/$ - see front matter Ó2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.wasman.2012.05.010
⇑
Corresponding author. Tel.: +48 0583471093; fax: +48 0583472694.
E-mail addresses: maciej@urethan.chem.pg.gda.pl,macsienk@pg.gda.pl
(M. Sienkiewicz).
Waste Management 32 (2012) 1742–1751
Contents lists available at SciVerse ScienceDirect
Waste Management
journal homepage: www.elsevier.com/locate/wasman
Author's personal copy
tyre recycling that would satisfy high quality norms requires the
application of technologically highly complex processes. Table 1
shows the basic raw material composition of tyres, together with
the percentage content of the various components used in the
manufacture of passenger and truck tyres in USA and Europe.
The widely differing chemical compositions and the cross-
linked structures of rubber in tyres are the prime reason why they
are highly resistant to biodegradation, photochemical decomposi-
tion, chemical reagents and high temperatures. It is for this reason
that the management of used tyres has become a serious techno-
logical, economic and ecological challenge.
The present work is a thorough review of recent EU legislation
in this respect as well as organizational approaches to the manage-
ment of used tyres, and characterizes innovative methods of recov-
ering and recycling this type of waste in member countries. It also
describes recent progress in research into the application of ground
waste tyres as a source of valuable raw materials used to produce
various kinds of polymer composites, obtained largely with the aid
of synthetic and natural rubbers, polyethylene, polypropylene and
polyvinyl chloride.
1.1. Legislation regarding used tyres management in the European
Union
The EU legislation on the procedures to adopt with regard to
used automobile tyres, which constitute a threat to the natural
environment, is an extensive set of regulations based on provisions
and dispositions of EU law. EU policy in this matter is founded on a
‘‘hierarchy of wastes’’: in the first place, waste formation should be
prevented, but if this is not possible, wastes should be re-used fol-
lowing recovery and recycling, and eliminating as far as possible
stockpiling in landfills (COM, 2005). That is why the EU’s strategy
for the management of used rubber products, and used tyres in
particular, is based on the 1999 Directive on the Landfill of Waste
1000/31/EC. Accordingly, member states were obliged to prohibit
the stockpiling of whole tyres in landfills from July 2003, and
ground tyres from July 2006, with the exception of bicycle tyres
and tyres with an external diameter of more than 1400 mm. Sup-
plementary to this legislation is the End of Life Vehicle Directive
2000/53/EC, passed in 2000, which regulates procedures for deal-
ing with vehicles withdrawn from service. According to this, tyres
must be removed from vehicles before these are scrapped, so that
they can be recycled. The recommendations in these directives do
not stipulate the means by which these aims are to be achieved.
Member states are thus presented with fresh challenges, stimulat-
ing the development of their own internal legal and organizational
regulations enabling state-of-the-art methods of recycling the
increasing numbers of used tyres without their being stockpiled
in landfills.
On the basis of past experience with waste management, EU
countries have developed three models to regulate and improve
supervision of used tyre management (ERTMA, 2010a):
1. Management model based on Extended Produced Responsibility
(EPR). According to this model, the management of used
tyres is the responsibility of the producers and importers
who put them on the market. It obliges them to organize
collections of used tyres and to ensure the legally required
levels of recovery and recycling of these wastes. This can
be done directly by the producer or through the mediation
of specialized recovery/recycling organizations acting on
their behalf. Fig. 1 names the largest recovery/recycling
organizations operating in European countries.
2. A tax system. Producers or sellers levy a disposal duty, added
to the cost of a new tyre and paid into the national budget.
The management of used tyres in this model is the respon-
sibility of the recovery/recycling organizations and is
financed by the state from the funds obtained from custom-
ers purchasing new tyres.
3. The free market system, which assumes the profitability of
recovery and recycling of tyres. This model assumes that used
tyres are a source of valuable raw materials, the manage-
ment of which is profitable to the firms involved.
Fig. 1 shows the distribution of the various systems of managing
used tyres in the countries of the European Union, Norway, Croatia
and Switzerland, and details the non-profit organizations adminis-
tering the program for recovering and recycling tyres in each
country.
In Europe the most popular of these three models is the one
based on extended producer responsibility (EPR). The success of
this approach can be measured by the high, even 100% recovery
of used tyres achieved by the countries that implemented it (Fin-
land, Hungary, Italy, Lithuania, Latvia, the Netherlands, Norway,
Poland, Romania, Spain and Sweden) In case of Belgium, France
and Portugal tyres recovery rate have achieve over 100%, because
recovery/recycling organizations operating in this countries may
have collected more waste tyres than their obligation (see Table 2).
Its advantage is the substantial transparency in the control of
the organizations fulfilling the imposed norms. In addition, the effi-
cient financing of the recovery organizations by the world’s largest
tyre manufacturers has enabled the development of research and
the implementation of modern technologies that raise the effi-
ciency of tyre recovery and recycling. According to ETRMA, the an-
nual investment in this respect in the EU is currently 5 million
euros. It is for these reasons that this model has become the foun-
dation of modern used tyre management in these 17 European
countries. On the other hand, the system based on the recovery
duty, operating in Bulgaria, Croatia, Ireland, Germany, Switzerland
and the UK, and the free market system (Denmark, Slovakia Rep.),
despite their simplicity, have turned out to be less attractive, which
means they are more difficult to control.
In accordance with the system based on the responsibility of
tyre producers and importers, they can fulfill the obligation of
managing used tyres themselves or devolve it to a non-profit orga-
Table 1
Typical materials used in tyre manufacturing (in Europe and USA) according to the percentage of the total weight of the finished tyre that each material class represents (wdk,
2003; Pehlken and Müller; 2009).
Materials In USA In European Union
Passenger tyre Truck tyre Passenger tyre Truck tyre
Natural rubber (%) 14 27 22 30
Synthetic rubber (%) 27 14 23 15
Carbon black (%) 28 28 28 20
Steel (%) 14–15 14–15 13 25
Fabric, fillers, accelerators, antiozonants, etc. (%) 16–17 16–17 14 10
Average weight New 11 kg, Scrap 9 kg New 54 kg, Scrap 45 kg New 8,5 kg, Scrap 7 kg New 65 kg, Scrap 56 kg
M. Sienkiewicz et al. / Waste Management 32 (2012) 1742–1751 1743
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nization expressly appointed to carry out this task on their behalf
(ERTMA, 2010a). The principles according to which recovery/recy-
cling organizations operate in the EU market are shown in Fig. 2.
It is the task of the recovery organization to fulfill on behalf of the
manufacturer the obligations regarding the achievement of the stip-
ulated levels of recovery and recycling. In the EU their activity
mainly involves the organization and coordination of a national
system of tyre collection from service and tyre exchange points,
automobile workshops and scrap yards and communities. They
are also obliged to pass on tyre wastes to the companies dealing with
energy recovery from tyres and to send them for retreading or
recycling. In accordance with the legislation, recovery organizations
are duty bound to file annual reports on the effects of their activities,
and should they have been unable to reach the required recovery
and recycling targets, they are obliged to pay a product tax,
separately for recovery and for recycling. A non-legal requirement
of these organizations is their educational activity, i.e. explaining
to the general public the problems of used tyre management.
If manufacturers or the organizations acting on their behalf fail
to discharge their obligations, they are required to pay a product
tax. How much they pay depends on the quotient of the difference
between the required and achieved recovery/recycling target and
the product tax rate as established by the government department
responsible for waste management. The funds obtained in this way
are used to finance the recycling and recovery of unmanaged
wastes and to support environmental programs concerning the
subject of used tyres.
According to figures published by the European Tyre & Rubber
Manufacturers’ Association in EU Member States, Norway and
Switzerland over around 3.2 million tonnes of used tyres were gen-
erated in 2010. After sorting, over 2.6 million tonnes of waste tyres
were introduced on the EU market for recovery and recycling,
beside of this 574 thousand tones were sent to retreading, reuse
and export. The estimated recovery rate of waste tyres achieved
96%, as compared with the 72.2% recovery rate of paper and the
58% recovery rate of total plastics, waste recycling and recovery
indicates that the EU’s policy regarding used tyre management is
highly effective (ETRMA, 2010a; PlasticsEurope, 2011; ERPA,
2010). In comparison to Japan (91% of recovery rate) or USA (89%
of recovery rate) Europe is one of the most advanced regions on
the world in the recovery and recycling of used tyres. Next to
Fig. 3, testimony of the highly efficient management of used tyres
in the EU27, statistical data also show that, the recovery rate of
waste tyres increased in EU27 by 34% over the last 6 years, while
the waste tyres arising increased only by 5%.
In Europe over the past 16 years we can observe a dramatic de-
crease of landfilling used tyres from 62% in 1994 to 4% in 2010,
while in this year reuse, retreading, recycling and energy recovery
in total has reached the level of 96% used tyres recovery (Fig. 4).
The major methods of recovery waste tyres in 2010 were energy
recovery 38% and material recycling 40%.
2. Methods of used tyre management
Tyres withdrawn from use because of their composition and
properties are now a source of valuable raw materials, and the
development of recovery methods has led to their effective conver-
sion to energy or materials, which can be used to produce new
goods of practical or utilitarian significance. The legal prohibition
of tyre stockpiling in landfills was the spur forcing levels of recov-
ery and recycling to rise. In view of this, the policies of most coun-
tries regarding used tyre disposal is based on their selective
collection and management by means of (RMA, 2009; ETRMA,
2010a; JATMA, 2010):
Fig. 1. Models for administering the management of used tyres in the Europe, showing the largest recovery/recycling organizations operating in EU countries(ETRMA,
2010a).
1744 M. Sienkiewicz et al. / Waste Management 32 (2012) 1742–1751
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Retreading.
Energy recovery.
Pyrolysis.
Product recycling.
Material recycling (grinding and devulcanization).
2.1. Retreading
Retreading is a process for extending the lifetime of tyres. It is
based on the preliminary preparation of a tyre for regeneration,
by stripping it of its tread and then applying a new one. Only tyres
that have passed a wear and tear inspection, and have been certified
to have no damage to the tyre carcass, may be retreaded. Retreading
can be done using either a cold or hot process. (Glijer and Lipinska,
2002; Lebreton and Tuma, 2006; Zebala et al., 2007). In the low-
temperature method the suitably prepared carcass is coated with
a layer of a rubber mixture, acting as binder, and an initially vulca-
nized tread of suitable pattern and size. This is all pressed onto the
carcass using special rubber envelopes and vulcanized in an auto-
clave at around 100 °C for 4–5 h. In the high-temperature method,
the fresh rubber mixture of the requisite composition and volume
is laid on the carcass, after which the whole is vulcanized in molds
producing the tread pattern. The process takes place at a tempera-
ture of 150–180 °C and elevated pressure. Retreading is economi-
cally very profitable: it requires only 30% of the energy and 25% of
the raw materials needed to produced new tyres (Ferrer, 1997;
Giere
´a et al., 2006). Moreover, it is a practically waste-free process,
the only by-product of retreading being pulp rubber, which can be
used for manufacturing polymer composites and in the construc-
tion industry. In practice, automobile tyres are not retreaded,
because of their uncompetitive cost vis-à-vis new tyres, poorer
quality and safety at high speeds (Pipilikaki et al., 2005; Zebala
et al., 2007). Truck and aircraft tyres are regularly retreaded,
however, for reasons of economy: the quality-to-price ratio for
large-size retreaded tyres is much higher than in the case of new
tyres. The largest tyre manufacturers estimate that every other
truck tyre worldwide is regenerated by retreading. This allows
considerable savings to be made when it comes to the purchase of
new tyres and significantly reduces the amounts of rubber wastes
(ChemRisk LLC, 2009).
2.2. Energy recovery
One of the basic ways of recovering used tyres or other used
rubber products is to use them as an energy raw material. Fuel con-
sisting of shredded tyres is denoted as TDF (tyre derived fuel) in
the international classification. Used tyres have a calorific value
of 32 MJ/kg, which makes them competitive with other types of
fuel, especially with coal, which has a far lower calorific value
(Giere
´a et al., 2006). The cement industry is one of the greatest
consumers of shredded tyres, which uses them as an alternative
fuel co-combusted with coal; their management is thus waste-free.
Cement plants are now able to use as a fuel only whole tyres. This
is possible because of the high temperatures in cement kilns
(>1200 °C), which ensure the complete combustion of all the tyre
components. The ash and steel cord are permanently bound to
the clinker, but this does not seriously impair its physicochemical
properties apart from a slightly longer cement binding time and a
greater water demand (Pipilikaki et al., 2005). Moreover, the com-
bustion of tyres in cement kilns is environmentally safe because of
the much lower emission, compared to coal combustion, of dusts,
carbon dioxide, nitrogen oxides and heavy metals (except zinc)
Table 2
Used tyres (in kilo tones) recovery in Europe Union (EU27), Norway (NO) and Switzerland (CH) in 2010, (italic indicates of countries which have introduced models based on
extended producer responsibility), (ERTMA, 2010b).
Country Used
Tyres
Arising
(A)
Reuse of part-worn tyres Waste tyres
Arising
(E)=AB+C+D
Waste tyres recovery Landfil/
unknown
(J)
Total recovery
(K)=B+C+D+F+G+I
Used
tyres
treated
(L)=K/
A(%)
Reuse
(B)
Export
(C)
Retreading
(D)
Civil
engineering
(F)
Recycling
(G)
Energy
(I)
Austria 60 0 7 3 50 0 20 30 0 60 100
Belgium 82 1 2 10 69 1 56 17 0 87 106
Bulgaria 20 0 0 0 20 0 0 0 20 0 0
Cyprus 8 0 0 0 8 0 0 0 8 0 0
Czech Rep. 57 0 0 2 55 0 9 29 17 40 70
Denmark 38 0 0 1 37 0 37 0 0 38 100
Estonia 10 0 0 0 10 0 5 4 1 9 90
Finland 41 0 0 1 40 40 0 0 0 41 100
France 381 36 0 43 302 38 128 147 0 392 103
Germany 614 10 84 45 475 0 215 260 0 614 100
Greece 49 0 0 2 47 0 27 15 5 44 90
Hungary 30 0 0 1 29 5 10 14 0 30 100
Ireland 35 3 2 2 28 8 17 0 3 32 91
Italy 426 0 12 43 371 20 80 180 91 335 79
Latvia 10 0 0 0 10 0 5 4 1 9 90
Lithuania 11 0 0 0 11 0 5 4 2 9 82
Malta 1 0 1 0 0 0 0 0 0 1 100
Netherlands 65 0 13 2 50 1 39 10 0 65 100
Poland 239 0 0 20 219 0 51 168 0 239 100
Portugal 92 1 2 18 71 0 50 26 0 97 105
Romania 33 0 0 0 33 0 1 32 0 33 100
Slovak Rep. 23 0 0 1 22 0 21 1 0 23 100
Slovenia 11 0 0 0 11 0 6 5 0 11 100
Spain 292 31 0 27 234 8 114 112 0 292 100
Sweden 79 0 1 0 78 12 19 47 0 79 100
UK 465 44 54 32 335 75 149 102 9 456 98
Norway 51 1 1 0 49 34 4 11 0 51 100
Switzerland 50 3 7 5 35 0 5 30 0 50 100
EU27 + NO + CH 3273 130 186 258 2699 242 1073 1248 157 3137 96
M. Sienkiewicz et al. / Waste Management 32 (2012) 1742–1751 1745
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(Conesa et al., 2008; Aliapur, 2009). Apart from the cement
industry, used tyres are also used as a fuel for the production of
steam, electrical energy, paper, lime and steel. This is because
the co-combustion of coal with ground rubber wastes improves
the thermal efficiency of steam boilers and furnaces, and the
amounts of exhaust gases and dusts do not exceed any permissible
limits (Levendis et al., 1996; Courtemanche and Levendis, 1998;
Singh et al., 2009).
2.3. Pyrolysis of rubber wastes
The management of used tyres by means of pyrolysis is based on
the decomposition of the elastomers contained in the rubber as a re-
sult of heating them to temperatures of 400–700 °C, in the absence
of oxygen. Tyres are pyrolyzed in special pyrolytic furnaces which,
depending on the technology employed, can operate at normal or
reduced pressure, in an atmosphere of a neutral gas (mainly nitro-
gen) (Berrueco et al., 2005). There also exist pyrolysis technologies
performed in the presence of substances in a supercritical state (e.g.
CO
2
) or plasma- or microwave-assisted (Appleton et al., 2005;
Ole˛dzka et al., 2006; Huang and Tang, 2009). The pyrolysis of tyres
yields a series of valuable chemical compounds in solid, liquid or
gaseous form, which after suitable processing can be used in the
petrochemical, energy or iron and steel industries (Yu-Min, 1996).
The solid products of tyre pyrolysis include fly ash, soot, the charred
remains of the oxides and sulphides of zinc, silica and steel. The gas
phase is rich in hydrogen, carbon monoxide and dioxide, aliphatic
hydrocarbons and hydrogen sulphide. The liquid phase contains
aromatic hydrocarbons and oils with a high calorific value, which
on removal of contaminating sulphur compounds, are usually
mixed with diesel oils and other petrochemical products. Unfortu-
nately, because of the high cost of installations and of servicing
the process, and also because of the uncompetitive prices of its
products, the pyrolysis of used tyres is very rarely used on an indus-
trial scale. Nevertheless, in view of the ongoing research into the
improvement of existing pyrolysis technologies and the mounting
costs of energy and petrochemical raw materials, this method of
managing waste tyres has considerable potential.
2.4. Product recycling
Product recycling is a separate form of material recycling that is
based on the recycling of entire used tyres, in their original form,
without any physical or chemical treatment. Because of their shape
and sizes, high elasticity, good damping properties of vibrations,
noise and shocks, tyres are used as a cheap material in construction
engineering. They can be used to form protective barriers along
roads and highways and to protect sloping waterfront banks and
roadsides. They can also be used as fenders for boats, artificial reefs
Fig. 2. Diagram describing the activity of organizations recovery/recycling tyres within the system based on extended producer responsibility (ETRMA, 2010a).
Fig. 3. Evolution of used tyres recovery between 2004 and 2010 (ETRMA, 2010a).
Fig. 4. Progress in recovery routes of waste tyres between 1994 and 2010 (ETRMA,
2010a).
1746 M. Sienkiewicz et al. / Waste Management 32 (2012) 1742–1751
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offering protection to marine organisms, as a material for road sub-
strates and as insulation for the foundations of buildings (Murugan
et al., 2008; Bosscher et al., 1997; Collins et al., 2002; Lee and Roh,
2007). A very interesting solution in this respect was developed by
the Solerebels company of Ethiopia, which produces footwear with
soles made from suitably shaped pieces of tyre treads. Likewise,
the Alchemy Goods Company (USA) manufactures handbags, wal-
lets and belts entirely from spent inner tubes. Nonetheless, the
product recycling of tyres is of marginal importance, so contributes
little to solving the problem of their management.
2.5. Material recycling
Material recycling, besides energy recovery, is the most com-
mon means of managing used tyres. It is realized as mechanical
grinding of tyres, which yields rubber materials of different de-
grees of comminution, or as devulcanization, which produces rub-
ber regenerates (De et al., 2005).
Devulcanization is based on decomposing the cross-linked
structure of vulcanized natural rubber, as a result of the partial
or complete breaking of the poly-, di- and monosulphur cross-link-
ing bonds formed during the original vulcanization process. Unfor-
tunately, devulcanization also degrades the chains in the main
rubber polymer, as a result of which the rubber product obtained
no longer possesses the properties of the starting material (natural
rubber); the process is thus termed ‘regeneration’. The known
methods of producing rubber regenerates include thermomechan-
ical, thermochemical, physical (microwave, ultrasound methods)
and biological ones – processes that involve complex transforma-
tions leading to depolymerization, oxidation, and in many cases
the degradation of the main chains of the natural rubber polymer,
which in turns reduced the viscosity of the material. Detailed
descriptions of these methods will be found in numerous papers
and patent applications, reviewed in papers (Holst et al., 1998;
Adhikari et al., 2000; Myhre and MacKillop, 2002; Rajan et al.,
2006). At present, rubber regenerates play an important role in
the rubber industry, which uses them as additives to fresh rubber
mixtures. They are employed in the manufacture of washers, cable
housings, rubber mats and slabs, as well as footwear.
The grinding of used rubber goods enables rubber granulates to
be used in the production of new materials, from which multifari-
ous objects of practical use can be made. This is not easy, since the
steel belts and textile overlays used in the production of the tyres
have to be separated from the granulate during grinding. Once sep-
arated, however, these materials can be put to use again. The scrap
steel is sent for smelting, whereas the textile cord, after cleaning
up, is either combusted (then energy is recovered) or used to pro-
duce thermal insulation materials for the construction industry.
The main aspect of tyre recycling is the obtained of the crumb rub-
ber. Its usefulness for particular applications is determined primar-
ily by the grain sizes of the various fractions and its degree of
purity. In EU the European Committee for Standardization (CEN)
has classified products of grinding waste tyres according to their
size (CEN/TS14243:2010). The objective here was to standardize
the market for products of the material recycling of used tyres;
as a result, five different types of rubber products (see Table 3).
The grinding of end-of-life tyres is a complex process requiring
special machines and equipment capable of shredding and granu-
lating materials of a high mechanical strength. In addition, this
operation requires a high energy costs, essential to ground tyres
into suitable fractions, which to a great extent determines the prof-
itability of the whole process. Nevertheless, the development of
studies aiming to improve the yield of this recycling method and
of new approaches to the utilization of crumb rubber for the man-
ufacture of practicable materials means that grinding is at present
a major form of used tyre management.
There are many methods for the efficient grinding of tyres, the
most important ones being grinding at ambient temperature, cryo-
genic grinding, wet grinding, Berstorff’s method and high-pressure
grinding with a water jet.
Obtaining a crumb rubber as a result of the mechanical grinding
of rubber wastes at ambient temperature involves the mechanical
grinding and granulation of the tyres using shredders, mills, knife
granulators and rolling mills with ribbed rollers (Sunthonpagasit
and Duffey, 2004; Myhre and MacKillop, 2002). They are usually
set up in a process line that enables the repeated grinding of
wastes until a crumb rubber of the required grain size is obtained.
The lower size limit of crumb rubber in this technology is rubber
dust with grains no bigger than 0.3 mm in size and a very rough
surface. In this process line there are also pneumatic separators
to remove fibres from the textile cordage, and electromagnets to
remove the steel parts of tyres. The mechanical grinding of tyres
produces considerable quantities of heat, which oxidizes the rub-
ber grains produced; the process line must therefore be equipped
with an arrangement for cooling the crumb rubber in order to pre-
vent its spontaneous combustion (De et al., 2005).
In cryogenic grinding liquid nitrogen is used to cool the previ-
ously cut up tyres to a temperature below that of the glass transi-
tion of the natural rubbers in the tyres. The frozen, brittle rubber at
80 °C is then sent to hammer mills, which crush the tyres into
suitable fractions. The process line for the cryogenic grinding of
tyres is also equipped with systems for removing the textile cord-
age and electromagnets for removing the steel parts.
The cryogenic grinding of tyres yields rubber granulates of very
small grain size, even as small as 75
l
m. Crumb rubber obtained in
this method consists of grains with smooth surfaces and sharp
edges, beside this most of them have the same shapes and sizes
(Myhre and MacKillop, 2002). Fig. 5 shows micrographs of rubber
granulates obtained from ambient temperature mechanical grind-
ing and from cryogenic grinding using liquid nitrogen.
Moreover, it is purer than that obtained by mechanical grinding
at ambient temperature. But it also has a higher humidity content,
about 12–15% of the mass. The main disadvantage of this method
is the high cost of the liquid nitrogen for cooling the rubber wastes.
Economically, cryogenic grinding is uncompetitive in comparison
with conventional grinding at ambient temperature. However,
there are methods for reducing the consumption or completely
eliminating the use of liquid nitrogen from this process. For exam-
ple, liquid nitrogen can be replaced by a system of compressors
capable of cooling used tyres to 100 °C with the aid of expanding
air (Reznik, 2002). Another possibility is to replace the electric
hammer mills with eddy mills, in which the material to be crushed
is made to rotate by expanding air (Liang and Hao, 2000).
The wet grinding of rubber wastes is an improved version of
ambient temperature grinding (Brubaker et al., 1984; Rouse,
2001; Rouse and White, 1996). This process involves grinding a
water suspension of an initially comminuted rubber granulate ob-
tained by other methods. Special mills with stationary and moving
grindstones are used here, which crush the stream of rubber gran-
ulate entering the space between them. The water of the rubber
granulate suspension continuously cools the product formed, not
to mention the grindstones, which heat up as a result of friction.
Table 3
Classification of rubber recyclates obtained dur-
ing the grinding of tyres (CEN TS14243).
Type of recyclate Size fraction
Cut tyres >300 mm
Shreds 20–400 mm
Chips 10–50 mm
Rubber granulate 0.8–20 mm
Rubber dust <0.8 mm
M. Sienkiewicz et al. / Waste Management 32 (2012) 1742–1751 1747
Author's personal copy
The advantage of this method is that we can obtain a very fine rub-
ber dust with the grain size as small as 10–20
l
m and with a large
specific surface area. This dust is added as a filler to rubber mix-
tures from which products with high quality requirements, for
example, solid tyres.
Grinding with a water jet was developed for the recycling of
highly resistant, large-size tyres from trucks, construction vehicles
and farm tractors. Conventional methods of grinding large-size
tyres require very massive grinding machines, which consume
enormous amounts of energy. The grinding factor is solely the
water jet, which at a pressure of more than 2000 bars and high
velocity strips the rubber from the tyres (Rutherford, 1992;
Gyorgy, 2009). An important merit of this technique is that it selec-
tively strips away from the steel cord the crumb rubber formed
from the butyl rubber membrane on the inside of the tyre and
the rubber material from which the tread and walls were made.
The crumb rubber obtained in this way is of a high degree of purity
since only the rubber is ground, the steel banding remains intact.
The crumb rubber is also very finely ground, and the grains have
a large specific surface area. The inventors of this method consider
it to be environmentally friendly, as it is energy-saving, produces
only a low level of noise, and does not generate pollutants.
Berstorff’s method is an improved version of obtaining crumb
rubber from the mechanical grinding of rubber waste at ambient
temperature (Capelle, 1997; Khait, 2005; Khait et al., 2001;). It uses
a rolling mill equipped with ribbed rollers and a twin-screw extru-
der, which when set up in series in the process line grind used
automobile tyres. This process can be divided into three stages.
In the first, the steel parts of the tyre are removed and cut up in
a knife mill into ca 85 50 mm pieces. The tyre pieces from stage
I are then broken up in ribbed rolling mills into fragments about
6 mm in size. The steel and textile cord reinforcements of the tyre
are also removed during this stage. In the last stage, the rubber
fragments from stage II are further ground in twin-screw extrud-
ers; these have specially constructed screws in which the rubber
wastes are ground using large shearing forces and high pressures.
The end product is a crumb rubber of small grain size (dust), a large
specific surface area and low humidity content.
Ground tyre and other rubber wastes containing high-quality of
natural and synthetic rubbers have become the raw material basis
for a series of approaches for obtaining composite products with
utilitarian properties. The magnitude of used tyre recycling is of
the order of 2 million tonnes/year just in the EU and USA, which
indicates that this method of managing rubber wastes has become
a separate branch of industry (RMA, 2009; ETRMA, 2010b). Litera-
ture reports and an analysis of the tyre recycling market indicate
that tyre rubber granulates are used principally as fillers and
modifiers in various different types of polymer compositions and
composites.
The specific properties of crumb rubber and their low cost mean
that approaches using rubber recycling products in polymer
compositions and composites have been extended to their applica-
tion in various branches of the construction industry and different
kinds of engineering applications.
Examples include shreds, chips and cut-up tyres, which are
used as light fillers in buildings (Hazarika et al., 2010; Siddique
and Naik, 2004). They have good thermo-insulating properties, a
low specific gravity, and are waterproof and resistant to environ-
mental factors. They are thus the ideal material for filling tunnel
structures, underground passages, road and highway embank-
ments, and retaining walls. They can also be used as materials
for forming the drainage layers of embankments and drainage
ditches. Crumb rubber, in the form of rubber granulates and dust,
can be used as a full-value raw material to obtain various kinds
of compositions and mixtures with asphalt used in highway engi-
neering (Navarro et al., 2004; Cao, 2007; Huang et al., 2007; Xiao
and Amirkhanian, 2010). Rubber-asphalt compositions improve
the quality of road surfaces, making them thermally more stable
and resistant to ageing. The addition of ground rubber to asphalt
also improves the elasticity of the asphalt binder and reduces the
susceptibility of the surface to rutting. Modification of the proper-
ties of mineral-asphalt mixtures using rubber granulate improves
its resistance to skidding and abrasion, reduces tyre-surface noise,
reduces light reflection from the surface and improves tyre grip
during wet and frosty weather.
Ground tyres are also used in the building industry as a filler for
cement mortar, which enables concrete compositions to be ob-
tained that are more resistant to bending, with better thermal
insulation and acoustic properties, and improved resistance to dy-
namic loading and cracking. The presence of a rubber material in
concrete structures also reduces moisture absorption and perme-
ability to chloride ions, thus offering steel structures better protec-
tion from corrosion (Piercea and Blackwell, 2003; Benazzouk et al.,
2007; Oikonomou and Mavridou, 2009).
2.6. Comparison of the key methods of recovery waste tyres used in
European Union
Data from the used tyres recovery/recycling market indicate
that their combustion plays a big role in the management of these
wastes (ETRMA, 2010a; ChemRisk LLC, 2009). It is mainly eco-
nomic aspects that are responsible for the popularity of the recov-
ery of energy from tyres over other methods of utilizing them.
From an investigation of the total energy and raw material balance
of tyre combustion and an assessment of its effect on the environ-
ment, Corti and Lombardi (2004) showed that this method has
more advantages than the other means of managing rubber wastes.
Their results demonstrate that preparing tyres as an alternative
fuel requires a smaller financial and energy outlay than their recy-
cling by grinding, which is an energy-consuming process. They
point to the considerable advantages accruing from the co-com-
bustion of tyres with coal in cement works, mainly because this
Fig. 5. Micrographs of rubber granulate grains obtained at ambient temperature (A) and cryogenically (B), (Sienkiewicz and Janik, 2009).
1748 M. Sienkiewicz et al. / Waste Management 32 (2012) 1742–1751
Author's personal copy
process produces practically no wastes. This is due to the fact that
the ash produced by the combustion is bound to the clinker, and
the emission of exhaust gases, like carbon dioxide and nitrogen
oxides, is much less than from the combustion of coal alone (Silv-
estraviciute and Karaliunaite, 2006). Moreover, technologies are
now available enabling the combustion of whole tyres, without
preliminary processing, and this substantially reduces the cost of
the raw materials. Thus, it is the policy of most countries to burn
a high proportion of used tyres in cement works. One example is
Poland, where 70% of used tyres covered by the legal requirement
for their recovery are disposed of in this way (see Table 2).
An analysis of the life cycle of tyres, seen from the moment of
their production to their recovery/recycling, indicates, however,
that despite the large economic gains to be made, the combustion
of tyres to recover the energy they contain is not a desirable meth-
od of managing them. An assessment of the energy balance of a
tyre’s life cycle (see Table 4) shows that some 87–115 MJ/kg of en-
ergy are required to produce a tyre, but only 32 MJ/kg are recov-
ered when it is combusted (Brown et al., 1996; Synder, 1998;
Amari et al., 1999). This means, then, that only 30–38% of the en-
ergy initially invested in the production of the tyre is recoverable.
In contrast, the amount of energy needed to recycle tyres by grind-
ing is barely 2–4% of the energy outlay required to produce them.
Furthermore, unlike tyre combustion, tyre grinding does not emit
harmful compounds into the air, and yields a crumb rubber, textile
cord and steel, which are valuable raw materials for other pro-
cesses (Fiksel et al., 2011).
From the energy balance point of view, then, it is much more
beneficial to lower the level of production of rubber goods ob-
tained from classical raw materials and to replace them with com-
posite materials with similar specifications containing products
obtained from tyre recycling. This approach is in line with the
EU’s waste hierarchy policy, which gives preference to the recy-
cling and recovery of tyres by retreading over their management
by combustion (EP-PE, 2008). It is also necessary to introduce into
used tyre management an approach taking account of the whole
life cycle of the product and not just its phase as waste, and to fo-
cus on reducing the environmental hazards involved in its produc-
tion and management.
Figures published by ETRMA show that in most EU countries
very great emphasis, as regards used tyre management, is being
placed on the development of new technologies and the improve-
ment of existing ones for recycling tyres and their retreading. Evi-
dence for this is provided by the high levels of recycling (42%) and
the considerable proportion of retreading processes in tyre recov-
ery, enabling 9% of the total mass of wastes to be managed (ETR-
MA, 2010b). Countries where used tyre management is based
mainly on recycling and retreading, without their combustion, in-
clude Denmark, Finland, Ireland, Slovakia and Slovenia.
3. Conclusions
Nowadays, there are many different approaches to develop
appropriate strategies to enhance the efficiency of waste polymer
management, in accordance with the applicable requirements of
the environment protection.
This is a challenge mainly due to a lack of suitable regulations
for recovery these wastes and ever growing amount of waste poly-
mer materials. However, as it is shown in this paper, in case of car
tyres, achieving a full success in the management of polymer
wastes is possible.
We showed that recently there has been great progress in the
development of innovative technologies improving management
of used tyres in European Union. Nowadays, in many countries of
EU, the level of recovery and recycling of used tyres is near 100%.
This is possible due to the European Union’s restrictive legal regu-
lations (Directive on the Landfill of Waste 1999/31/EC and End of
life Vehicle 2000/53/EC), which prohibit stockpiling of tyres in
landfills.
There are three following models helping in improvement of
used tyres management in EU’s countries: development of organi-
zational solutions based on the concept of extended producer
responsibility for products (Extended Produced Responsibility),
tax system and free market system. In Europe, the most popular
model is the one based on extended producer responsibility
(EPR), which legally obligates producers and importers of tyres to
collect and then ensure recovery and recycling of the entire quan-
tity of tyres placed on the market in a given year.
The producers of tyres probably would not be interested in
recovering and recycling tyres if a new law requiring them to do
so did not exist. The new regulations caused increased investments
in modern tyre sorting and collection systems and spawned inno-
vative methods to enhance recovery efficiency.
Material recycling and combustion of used tyres are currently
the most technologically developed methods of handling with
these wastes in the EU. It is worth pointing out that (from an eco-
nomic point of view) tyre combustion and energy recovery is more
attractive than material recycling. However, we get less energy
from combustion process of waste tyres, than we needed for pro-
duction of tires. Therefore, material recycling of waste tyres and
using them as a source of raw materials seems to be a better meth-
od than combustion.
Moreover, as it is shown in this paper, through grinding pro-
cesses of waste tyres they can become a source of valuable raw
materials. In this way tyres can be reused to produce different
kinds of very valuable polymer composites, obtained mainly with
the aid of natural and synthetic rubbers, polyethylene, polypropyl-
ene and polyvinyl chloride. The advantages of using ground waste
tyres for production of polymer composites include cost reduction
of such composites and also the ability to classify them as a pro-
ecological material.
When using ground rubber as a raw material, it is possible to
obtain completely new types of commercial polymer materials.
In today’s environment, used tyres should no longer be considered
a pollutant, but rather a valuable raw material.
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