Int. J. Environmental Technology and Management, Vol. 16, No. 4, 2013 279

Copyright © 2013 Inderscience Enterprises Ltd.

Tyres: destination end

Aurelio Ramírez-Hernández* and Jorge Conde-AcevedoUniversity of Papaloapan, Tuxtepec Oaxaca, México E-mail: chino_raha@hotmail.com E-mail: jorgeconde@hotmail.com *Corresponding author

Abstract: Nowadays, the tyre is one of the essential materials for transportation, communication and development of societies. For this reason, a large quantity of tyres is produced each year, Due to use, tyres wear out and need to be replaced by new ones. One of the concerns of humanity is searching for applications for wasted tyres, since the vast majority of tyres are deposited in the streets or in inappropriate places, causing environmental and health problems. Some methods and alternatives that are focused on solving these problems have been systematically and effectively proposed. Between the proposed methods, those that are highlighted are thermal degradation, chemical degradation, recycling and usage of wasted tyres as energy sources, as food sources for some microorganisms and as material for cement manufacturing. This article reviews some general aspects of the tyre and the main methods of degradation and recycling of discarded tyres.

Keywords: tyre; waste; vulcanised; rubber; environmental pollution; degradation; recycling; reuse; burned.

Reference to this paper should be made as follows: Ramírez-Hernández, A. and Conde-Acevedo, J. (2013) ‘Tyres: destination end’, Int. J. Environmental Technology and Management, Vol. 16, No. 4, pp.279–289.

Biographical notes: Aurelio Ramírez Hernández received a university degree in chemistry from the University of Guanajuato in 2000; he obtained his master’s degree in chemical sciences, with specialisation in physical chemistry, from the University of Guanajuato in 2004. His research titled “Ring opening polymerization of ε-caprolactone initiated by decamolybdate anion: Determination of kinetic and thermodynamic parameters by DSC and 1H-NMR” was completed in 2009. He also conducted a historical research of synthesis and chemistry degradation of polymer and block copolymers as poly (ethylene terephthalate) PET, Poly(s-caprolactone) PCL and poly (ethylene glycol) PEG. He also undertook further characterisation of chemical products used in paint. Since 2007, he has been a professor at the University of Papaloapan in the area of chemical sciences.

Jorge Conde Acevedo received a university degree in physics from the University of Veracruz in 1992; he obtained his master’s degree in optical sciences, with specialisation in from the National Institute of Astrophysics, Optics and Electronics (INAOE) in 1997. He did his science doctorate in optics from INAOE in 2001. His research focuses on classifi cation of fruits by colour multispectral images. He has further conducted a historical research “Description and comparison of different methods for mapping the color gamut of an input device and an output.” He further

280 A. Ramírez-Hernández and J. Conde-Acevedo

completed the “Analysis of the main features of an image from the multispectral images.” Since 2004, he has been a professor at the University of Papaloapan in the area of chemical sciences.

1 Introduction

The common tyre is a viscoelastic structure composed of 60–65% vulcanised rubber by weight, the remainder being various additives such as plasticisers and steel reinforcement (Holst et al., 1998; Juma et al., 2006). Rubber is a polymer of isoprene, milky white fl uid called latex that is found naturally in tropical trees, such as, for example, families Euphorbiaceae (Hevea brasiliensis), Moraceae (Castilla elastica Sesse ex Beer, Ficus elastica Roxb. Ex Hornem and Ficus lutea Vahl) and Apocynaceae Juss (Funtumia africana (Benth) Stapf). Synthetic rubber can be manufactured through the polymerisation of hydrocarbons.(Ping et al., 1995; Kang et al., 2000; Seymour and Carraher, 2002; Flores and Lindig, 2005). Curing is a process in which the rubber and sulphur are heated to obtain a rigid and hard. Uncured rubber is characterised by a low melting point and also becomes brittle at low temperatures (Davis, 1930; Wallace, 2008).

2 History

In 1839, Charles Goodyear discovered and perfected the rubber vulcanisation process (Wallace, 2008). In 1846, Robert William Thomson patented the fi rst tyre in France, which consisted of a hollow elastic rubber belt infl ated with air to create a rubber cushion between the ground and the tyre rim. This belt was covered by a thick outer covering made of skin, which was screwed to the wheel. Thomson proved that an air-fi lled tyre could reduce the energy required to move a vehicle by 60% on smooth roads and up to 300% when operating on rough surfaces. His fi ndings were published in the August 22, 1846 edition of “Mechanics Magazine.” Despite successful testing, the benefi ts of infl ated tyres were not perceived by the public (White, 1995; Miller et al., 2009).

The tyre did not return to the public view for 42 more years, when the fi rst bicycle tyre was developed by John Boyd Dunlop. Commercial production of tyres started in late 1890 and Dunlop worked in conjunction with William Du Cross to form a company which would later become known as the DuPont Rubber Company.

In 1898, Frank Seiberling, in honour of the inventor of vulcanisation, started the Goodyear Tire and Rubber Company in Akron, Ohio (White and Kim, 2008). The company produced a variety of goods, namely carriage and bicycle tyres, horseshoes and poker chips. The tubeless tyre was patented by Goodyear in 1903 and in 1906, the company invented a tyre with a bead wire and right shoulder, which made the tyre much easier to install or change. Despite the anti-tyre lobbying of the steel industry (most wheels were made nearly completely of steel), the new Goodyear tyre was widely accepted and was generally considered a resounding success (O’Reilly and Keating, 1983).

During the early twentieth century, the expansion of automobile use in the US led to the formation of a large number of companies that produced tyres and rubber parts. In 1947, the fi rst fully synthetic rubber tyre was manufactured in Germany by Fritz Hoffman, working in conjunction with Farbenfabriken Continental Vormals of Hanover and Friedrich Bayer &

Tyres: destination end 281

Co. The company BF Goodrich introduced the tubeless tyre in 1965, which was originally offered in the US (White, 1995). The radial Pirelli tyre was released by Dunlop in 1974. Currently, Goodyear is the largest tyre producer in the world, followed by Bridgestone and Michelin (Holley 2008). The tyre has become an undeniable aspect of modern society, being found in automobiles, aircraft, motorcycles and bicycles. The purpose of this article is to review the most relevant information about tyres and to investigate potential options for recycling and reuse.

3 The waste and consumption of tyres

Worldwide, approximately 16–17 million tons of rubber are produced every year, of which roughly 65% is used for tyre manufacture (Miller et al., 2009). According to the German consulting company Ralph Lane Polk & Co., there were about 4,000 million tyres on the road in 2010. The Rubber Manufacturers Association (RMA) estimates that in this same year, 285 million tyres were in use in cities in the US; this number was projected to grow by 3% in 2011, although statistics have not yet been released. In Mexico, the National Institute of Statistics and Geography (INEGI) states that approximately 122 million tyres were used in the country in 2009. In Peru, this number was signifi cantly less: the National Statistics Institute (INEI) estimated that there were roughly 8 million tyres being utilised in 2009.

However, since tyres have limited durability due to wear and loss of mechanical properties while in use, they must be periodically replaced with new ones (Prevorsek et al., 1984). Knowing that tyres are very resistant to natural degradation, as well as to chemical solvents, one may ask, then what is the fi nal destination of the tyres when a person decides to replace them with new or re-used tyres?

The European Tyre and Rubber Manufacturer Association (ETRMA), a collective of 27 countries, estimates that 3.172 million tons of tyres were discarded in 2010. Germany was the country with the largest number of discarded tyres, 614,000 tons. However, none of these tyres ended up in landfi lls because they were recycled: 10,000 tons were reused, 84,000 tons were pulverized, 45,000 tons were reprocessed, 215,000 tons were used in other applications and 260,000 tons were used as an energy source (see Table 1). Other European countries that recycle 100% of discarded tyres are France, Spain and Belgium. Italy, in contrast, produced 426,000 tons of waste tyres in 2010, 91,000 tons of which ended up in landfi lls. Compared to the rest of the world, Europe is skilled in the recovery and recycling of tyres. In Latin American countries, tyre waste is much more prevalent. For example, the National Environmental Council of Brazil (CONAMA) states that of the 40 million tyres discarded annually, 34 million end up in landfi lls. In Ecuador, International Tire and Rubber (INTRA) estimates that only 20% of used tyres are recycled.

In Mexico, of the 25 million tyres which are replaced each year, nine of every ten are thrown away. Interestingly, according to the Secretary of Environmental and Natural Resources of Mexico (SEMARNAT), there is a large number of tyres piled along the US–Mexico border: approximately one to two billion tyres on the Mexican side and roughly 300 million tyres on US soil. This year, Peru dropped 80 tons of solid waste, including tyres, into a national riverbed. Panama discards one million tyres annually. The US discards 250 million tyres per year, almost one per person (Serumgard and Eastman, 1995; Castaldi et al., 2007; SEMARNAT, 2010). Clearly, the problem of scrap tyres is growing—there are few countries which recycle all of their used tyres and most waste tyres end up in dumpsites, causing serious public health and environmental issues.

282 A. Ramírez-Hernández and J. Conde-Acevedo

Table 1 Discarded tires in some European countries according to ETRMA in 2010

País

*discarded tires*Particles of

intermediate size *Recovery of discarded tires

Volume Reuse Export Retreading Material EnergyLandfi ll / un known

Germany 614 10 84 45 215 260 0Czech 57 0 0 2 9 29 17RepublicBulgaria 20 0 0 0 0 0 20Greece 49 0 0 2 27 15 5Italy 426 0 12 43 100 180 91France 381 36 0 43 164 133 0Spain 292 31 0 27 122 112 0Ukraine 465 44 54 32 224 102 9Lithuania 11 0 0 0 5 4 2Belgium 82 1 2 10 57 17 0Ireland 35 3 2 2 25 0 3Cyprus 8 0 0 0 0 0 8Total UE-27

3172 127 179 253 1272 1207 157

*amounts in thousands of tons.

The most common problems arising from inadequate management of scrap tyres are:

1 When tyres are burned, often intentionally to remove embedded steel, or as fuel, polluting gases such as sulphur dioxide, nitrogen dioxide, carbon monoxide and polycyclic hydrocarbons (particle size: 60–212 microns) are produced, see Table 2 (Levendis et al., 1996 and 1998, Cocagne et al., 2004). Emissions of these gases cause cancer, are mutagenic and teratogenic. Furthermore, the gases can damage the central nervous system and irritate the skin, eyes, mucus membranes and the respiratory system. Sulphur dioxide and nitrogen dioxide are also contributors to acid rain; these and other gases are also implicated in the greenhouse effect and in destruction of the ozone layer (Demarini et al., 1994; Cantanhede and Monge, 2002; Guerrero and Salazar, 2004; Caballero, 2010; Mehta, 2010).

Table 2 Some products generated by burning tires. (Teng et al., 1997; Mastral et al., 2001; Carranza and Salazar, 2004; Councell et al., 2004; Juma et al., 2006; Pawan et al., 2006)

Acenaphthene Nitrogen dioxideAcenaphthylene PhenolBenzene HexachloroethaneBenzo (a) anthracene HexaneBenzo (a) pyrene Carbon MonoxideBenzo (b) fl uoranthene PlumbChrome TolueneSulfur Dioxide VanadiumDi-benzo (a, h) anthracene Zinccadmium Iron

Tyres: destination end 283

2 Tyres occupy a large volume in landfi lls because they cannot be compacted—this in turn leads to terrain instability. Additionally, discarded tyres offer safe havens for insects, snakes and vermin. The reproduction of certain mosquitoes can be four thousand times greater in the stagnant water of a tyre than in a natural environment. This increases the chances of epidemics of diseases such as dengue fever (“break bone fever”), an illness that is transmitted by the mosquito Aedes aegypti and is most common during the rainy season in tropical climates (Morrison and Scott, 2003; Health, 2009).

As a result of these factors, the improper disposal of used tyres is a growing threat to the environment and public health. There is a wide demand for novel methods of tyre degradation and recycling (Mosque and Dols, 1997; Chaikaew Sukontasukkul,2005).

4 Treatment of Discarded Tyres

Some of the current and alternative methods for tyres recycling and reuse are shown below.

A. Thermal degradation of the tyres. Pyrolysis is the thermal degradation of a mate-rial in the absence of oxygen (Juma et al., 2006). In recent years, research involving thermogravimetric analysis (TGA) has been conducted on reactors used for processing waste tyres. The tyres are ground to a specifi c particle size and pyrolysed at a tem-perature ranging from 20 to 1000oC in an inert atmosphere. The products obtained are primarily oils, gases and activated carbon, as shown in Figure 1 (Chang, 1996; Conesa et al., 2004; Mis-Fernandez et al., 2006; Unapumnuk et al., 2006; McKay et al., 2008; Murillo et al., 2008; Castaldi and Kwon, 2009; Lopez et al., 2009).

Figure 1 Thermal degradation reaction.

The obtained oils are similar to petroleum-based oils, with respect to viscosity, density, fl ash point, heat content and the amount of hydrogen and carbon. These oils are used as fuel, as raw material for oil refi neries, or as a source of fi ne chemicals. The primary gases released during tyre pyrolysis are methane, ethane, carbon dioxide and hydrogen (Mastral et al., 2006). The high caloric value of these gases is suffi cient to provide the power for a pyrolysis plant. Activated carbon obtained from this process is comparable to commercial activated carbon and may be useful as a solid fuel. Research indicates that products formed from tyre pyrolysis probably result from a free radical mechanism, which is indicative of complete pyrolysis. Tyre pyrolysis is the easiest way to eliminate waste tyres (Murillo et al., 2005), but to perform thermal degradation on a large scale would require a signifi cant fi nancial investment (Rader, 1995; Teng et al., 1995; Williams et al., 1995; Lin et al., 1998; Kim et al., 1999; Ariyadejwanich et al., 2003; Chen and Qian, 2003; Byung 2005; Miranda et al., 2006).

B. The tyre as raw material for cement manufacture. Cement is a building material used worldwide; studies have indicated that tyres can be used in cement composites to help minimise pollution. Cement is composed primarily of calcium oxide (CaO, lime), silicon dioxide (SiO2, silica), ferric oxide (Fe2O3, hematite), calcium sulphate (CaSO4.2H2O, gypsum) and aluminium trioxide (Al2O3, bauxite) (Vian, 1998).

284 A. Ramírez-Hernández and J. Conde-Acevedo

The incorporation of tyre fragments in cement has been investigated and it has been determined that 33% of cement composition can be replaced by tyre rubber (Ganjiana et al., 2008). Fattuhi and Clark (1996) found that truck tyre pieces in cement decreased the modulus and increased the porosity of concrete (cement) and that the exposed concrete could be treated with sodium hydroxide to provide additional stability. In 2003, studies began into cement modifi ed with rubber pellets—so-called crumb rubber concrete (CRC) (Li et al., 1998; Chaikaew, 2005; Sukontasukkul and Tobolski, 2006; Chavez et al., 2007). The external part of the concrete, when exposed to tetrachloroethane and methylene chloride, yields a paste with characteristics similar to those of traditional concrete. The composite is resistant to sulphuric acid and sodium chloride. The Mexican cement company CEMEX began incorporating used tyres in paving material in 2004; this pavement has been utilised in the cities of Monterrey, Tijuana and Reynosa. The physical properties are similar to traditional petroleum-based paving materials, but the production cost is higher. The Rubber Manufacturers Association estimates that in 2005, 58 million tyres were used in Portland cement plants worldwide (Kizinievic et al., 2006; Segre et al., 2006; Kyung and Young, 2009; Newspaper El Siglo de Torreon, 2009).

C. Chemical degradation of the tyres. The chemical degradation of tyres involves catalytic reactions and cryogenics (the study of material properties at very low temperatures), which when combined allow for the recovery of both rubber and steel from waste tyres. The catalytic degradation process has an effi ciency of approximately 90% and yields rubber, liquids and gaseous products which can be used as raw materials for industrial products such as adhesives, plasticisers and paints. When compared to thermal degradation, catalytic degradation requires much lower temperatures (40–60 C). An example: with a zeolitic catalyst and lubricating oil, under a nitrogen atmosphere, oil (83.1%), liquid (13.58%) and gas (3.32%) products are obtained (Izquierdo et al., 2004; Wei et al., 2006; Kragh 2007; Newspaper El Universal, 2008). The chief disadvantage of the chemical degradation of tyres lies in separating the steel from the rubber, which must be performed at very low temperatures. The liquid nitrogen or helium required for this cryogenic process increases the industrial cost (West, 1998; Parra et al., 2010).

D. The wheel as a food source for some microorganisms. Some gram positive microorganisms, such as actinomycetes, are able to digest rubber tyres. Linos et al. isolated several of these bacteria from nature and concluded that these organisms are able to consume both natural and synthetic rubbers as a sole source of alimentation. A synthetic latex glove was degraded by 75% over a period of two weeks by the bacterium Nocardia sp. 835A into oligomers of 103-104 daltons. In general, the oligomers are easiest to degrade by both chemical and biological means (Tsuchii et al., 1985; Oceguera et al., 2007). Researchers at the National Autonomous University of Mexico (UNAM) found that bacteria of the genus Alicycliphilus sp. feed on polyurethane, which is a component of modern tyres. The bacteria produce an esterase enzyme which degrades the ester bonds in the polymer and allows the bacteria to utilise the polymer as food. This was verifi ed by infrared and nuclear magnetic resonance spectroscopies and electron microscopy. Data showed that the maximum activity of the esterase enzyme was not reached for 18 hours, which is the main disadvantage of this tyre degradation method (Linos et al., 2000; Guerrero, 2008).

Tyres: destination end 285

E. The wheel as a source of energy. Tyres have a calorifi c value of 33 MJ / kg, a value on par with many fossil fuels and greater than that of coal. For this reason, discarded tyres have been used as fuel in industrial furnaces. The kilns in some cement plants utilise tyres, which are burned at 1450C to insure complete combustion (without the generation of soot). The steel from this process is incorporated into the concrete, providing additional strength and also saving gas and fuel oil (Alvarez et al., 2004; Juma et al., 2006). Discarded tyres are also used in some power plants—in Mexico, for example, 2% of waste tyres are burned to create electricity (Chavez and Hernandez, 2007).

If the combustion of the tyres is not adequately controlled, toxic gases and particles may be released into the environment. These may include dioxins, mercury, polyaromatic hydrocarbons (PAHs) and heavy metals (lead, zinc, nickel and vanadium). These emissions can cause cancer, birth defects, diabetes and lung damage and can affect the central nervous, immune and hormonal systems of the human body (Levendis et al., 1998). Studies have shown that cement kilns which use tyres as fuel produce more toxic emissions that those that use coal or natural gas (SEMARNAT, 2010; Mastral et al., 2001).

F. Recycling tyres. Recycling is another option for solving the environmental issues caused by discarded tyres. Tyres have been used in the manufacture of purses, shoe soles, belts, packaging, artifi cial reefs and decorative materials. They have also been used to modify asphalt, control erosion and create athletic fi elds (Saddleblack, 2008). Companies including Samsung, Sony Ericsson, Motorola and Nokia have developed various models of phones, where some of the parts or accessories are made from recycled tyres. Furthermore, waste tyres have been used in the production of waterproofi ng materials for concrete and other surfaces; these sealants are composed of reinforced acrylic resin blends with crumb rubber. These coatings are highly resistant to weather elements and can be applied to a wide variety of surfaces. The main disadvantage is that only 25% of the tyre is used in these sealants (Epps, 1994; Chavez and Hernandez, 2007). Yet another application of recycled tyres is in home construction. The walls, fl oors and ceilings of some houses may contain recycled rubber material and even whole tyres (Bakke and Ferro, 1989; Snell, 2004). Overall, applications of recycled tyres are varied, easy and inexpensive compared to other degradation processes.

5 Conclusion

Currently, there are several methods for the recycling or degradation of discarded tyres. This article has a brief description of the advantages and disadvantages of the known methods of tyre degradation and recycling. Thermal degradation is the most studied degradation method and also the most widely implemented. Chemical degradation, while required less energy than thermal degradation, has a higher cost. The degradation of tyres by microorganisms, while promising, is slow when compared to the rate of accumulation of waste tyres. As a source of energy, the burning of tyres can be counterproductive due to the potential release of a large number of toxins resulting from poorly controlled combustion. The recycling of used tyres has the option of being the easiest option to implement and is also the cheapest; however, only 5% of tyres are currently recycled. The methods of degradation and recycling

286 A. Ramírez-Hernández and J. Conde-Acevedo

of tyres that current exist are insuffi cient, as a large number of tyres still end up in landfi lls. To slow or stop the impact of waste tyres on the environment and public health, alternative methods of degradation and tyre recycling must be explored.

Acknowledgements

We are grateful to Jared J. Gerschler and Martha Rocio Valencia Estacio for their assistance on this article.

ReferencesAlvarez, R., Callén M.S., Clemente, C., Díaz, B.M.A., López, J.M., Mastral, A.M. and Murillo, R.

(2004) ‘Slagging in fl uidized bed combustion of rubber tire, Inorganic component evolution’, Ind. Eng. Chem. Res., Vol. 43, pp.7762–7767.

American Chemical Society. Washington D.C., EUA. Vol. 609, pp.196–201.Ariyadejwanich, P., Tanthapanichakoon, W., Nakagawa, K., Muka, S.R. and Tamo, H. (2003)

‘Preparation and characterization of mesoporous activated carbon from waste tires’, Carbon, Vol. 41, pp.157–164.

Bakke, T.O. and Ferro, M. (1989) ‘Technology comes home’, Pop Sci., Vol. 235, pp.63–69.Byung, S.H. (2005) ‘Gasifi cation Kinetics of waste tire char and sewage sludge char with steam in

termobalance reactor’, J. Ind. Eng. Chem., Vol. 11, pp.361–367.Caballero, E. (2010) ‘Quema de llantas afecta una comunidad’, Available from:http://www.tvn-2.com/

noticias/noticias_detalle.asp?id_news=33841 [Accessed 18August 2011]. Cantanhede, A. and Monge, G. (2002) ‘Estado del arte del manejo de llantas usadas en las Américas’,

Available from: http://www.bvsde.paho.org/bvsacd/cd24/manejo.pdf [Accessed 18 August 2011].Caponero, J., Tenório, J.A.S., Levendis, Y.A. and Carlson, J.B. (2004) ‘Emissions of batch combustion

of waste tire chips: The hot fl ue-gas fi ltering effect’, Energ. Fuel., Vol. 18, pp.102–115.Carranza, J.D. and Salazar, D.B. (2004) ‘Quía Prácticapara municipalidades sobre re-uso de llantas’,

Available from: http://www.borsicca.com/downloads/gt1248906176.pdf [Accessed 18 August 2011].

Castaldi, J.M. and Kwon, E. (2009) ‘Fundamental understanding of the thermal degradation mechanisms of waste tires and their air pollutant generation in a N2 atmosphere’, Environ. Sci. Technol., Vol. 43, pp.5996–6002.

Castaldi, M.J., Kwon, E. and Weiss, B. (2007) ‘Benefi cial use of waste tires: an integrated gasifi cation and combustion process design via thermo-gravimetric analysis (TGA) of styrene-butadiene rubber (SBR) and poly-isoprene (IR)’, Environ. Eng. Sci., Vol. 24, pp.1160–1178.

Chang, Y.M. (1996) ‘On pyrolysis of waste tire: degradation rate and product yields’, Resour. Conserve. Recy., Vol. 17, pp.125–139.

Chavez, V.E.L. and Hernandez, B.C. (2007) ‘El uso de productos reciclados en la industria de la construccion’, Naturaleza. Vol. 10, pp.4–6.

Chen, F. and Qian, J. (2003) ‘Studies of the thermal degradation of waste rubber’, Waste Manage, Vol. 23, pp.463–467.

Conesa, J.A., Gullon, I.M., Font, R. and Jauhiainen, J. (2004) ‘Complete Study of the Pyrolysis and Gasifi cation of Scrap Tires in a Pilot Plant Reactor’, Environ. Sci.,Technol., Vol. 38, pp.3189–3194.

Councell, T.B., Duckenfi eld, K.U., Landa, E.R. and Callender, E. (2004) ‘Tire-wear particles as a source of zinc to the environment’, Environ. Sci. Technol.,Vol. 38, pp.4206–4214.

Davis, H.S. (1930) ‘The fi rst pneumatic tire. Invented to please a boy’, Pop. Sci.,Vol. 116, pp.44–166.

Tyres: destination end 287

DeMarini, D.M., Lemieux, P.M., Ryan, J.V., Brooks, L.R. and Williams, R.W. (1994) ‘Mutagenicity and chemical analysis of emissions from the open burning of scrap rubber tires Environ’, Sci. Technol., Vol. 28, pp.136–141.

Epps, J.A. (1994) ‘Uses of recycled rubber tires in highways: a synthesis of highway practice’ National Cooperative Highway Research Program, Washington, EUA. Vol.162.

Fattuhi, N.I. and Clark, L.A. (1996) ‘Cement-based materials containing shredded scrap truck tyre rubber’, Constr. Build. Mater., Vol. 10, 229–236.

Flores, O.M.H. and Lindig, C.R. (2005) ‘La Lista de nombres vulgares y botanicos de arboles y arbustos propicios para repoblar los bosques de la Republica de Fernando Altamirano y Jose Ramirez a mas de 110 anos de su publication’, Rev. Mex. Biodiv.,Vol. 76, pp.11–35.

Ganjiana, E., Khoramib, M. and Maghsoudi, A.A. (2008) ‘Scrap-tyre-rubber replacement for aggregate and fi ller in concrete’, Constr. Build. Mater., Vol. 23, pp.1828--1836.

Guerrero, M.V. (2008) ‘Esperanza ambiental. Bacterias contra el poliuretano’, Cómo ves?, Vol. 117, pp.10–14.

Holley, W.H., Jennings, K.M. and Wolters, R.S. (2008) ‘The Labor Relations Process’, 9a ed. Cengage Learning, Canada. Vol. 696.

Holst, O., Stenberg, B. and Christiansson, M. (1998) ‘Biotechnological possibilities for waste tyre-rubber treatment’, Biodegradation, Vol. 9, pp.301–310.

Izquierdo, J.F., Cunill, F., Iborra, M. and Tejero, J. (2004) ‘Cineticas de las reacciones quimicas’, Universitat de Barcelona. Barcelona, Espana. Vol. 304.

Juma, M., Korenova, Z., Markos, J., Annus, J. and Jelemensky, E. (2006) ‘Pyrolysis and combustion of scrap tire’, Petroleum & Coal, Vol. 48, pp.15–26.

Kang, H., Young, K.M. and Han, K.H. (2000) ‘Identifi cation of natural rubber and characterization of rubber biosynthetic activity in fi g tree’, Plant Physiol, Vol. 123, pp.1133–1142.

Kim, W., Kim, H.J., Jung, S.K. and Hong, I.K. (1999) ‘Decomposition characteristics of raw rubber and tire by thermal degradation process’, J. Korean Ind. Eng. Chem., Vol. 10, pp.1052–1060.

Kizinievic, O., Maciulaitis, R. and Kizinievic, V. (2006) ‘Use of rubber waste in the ceramic’, Mater. Sci., Vol. 12, pp.237–242.

Kragh, H. (2007) ‘Qeneraciones cudnticas: una historia de la fi sica en el siglo XX’, Akal, Madrid, Espana. Vol. 480.

Kyung, H.C. and Young, K.H. (2009) ‘Weathering properties of elastic rubber concrete comprising waste tire solution’, Polym. Eng. Sci., Vol. 49, pp.794–798.

Levendis, Y.A., Atal, A. and Carlson, J.B. (1998) ‘On the correlation of CO and PAH emissions from the combustion of pulverized coal and waste tires’, Environ. Sci. Technol, Vol.32, pp.3767–3777.

Levendis, Y.A., Atal, A., Carlson, J., Dunayevskiy, Y. and Vouros, P. (1996) ‘Comparative study on the combustion and emissions of waste tire crumb and pulverized coal Environ’, Sci. Technol., Vol. 30, pp.2742–2754.

Li, Z., Li, F. and Li, J.S.L. (1998) ‘Properties of concrete incorporating rubber tyre Particles’, Mag. Concrete Res., Vol. 50, pp.297–304.

Lind, J.P., Changd C.Y. and Wud C.H. (1998) ‘Pyrolysis kinetics of rubber mixtures’, J. Hazard Mater., Vol. 58, pp.227–236.

Linos, A., Berekaa, M.M., Reichelt, R., Keller, U., Schmitt, J., Flemming, H.C., Kroppenstedt, R.M. and Steinbuchel, A. (2000) ‘Biodegradation of cis-1,4-polyisoprene rubbers by distinct actinomycetes: microbial strategies and detailed surface analysis’, Appl. Environ. Microb., Vol. 66, pp.1639–1645.

Lopez, G., Olazar, M., Amutio, M., Aguado, R. and Bilbao, J. (2009) ‘Infl uence of tire formulation on the products of continuous pyrolysis in a conical spouted bed reactor’, Energy Fuels, Vol. 23, pp.5423–5431.

Mastral, A.M., Callen, M.S., Garcia, T. and Lopez, J.M. (2001) ‘Benzo(a)pyrene, benzo(a)anthracene and dibenzo(a,h)anthracene emissions from coal and waste tire energy generation at atmospheric fl uidized bed combustion (AFBC)’, Environ. Sci. Technol., Vol. 35, pp.2645–2649.

288 A. Ramírez-Hernández and J. Conde-Acevedo

Mastral, A.M., Murillo, R., Aranda, A., Aylon, E. and Callen, M.S. (2006) ‘Process for the separation of gas products from waste tire pyrolysis’, Ind. Eng. Chem. Res., Vol. 45, pp.1734–1738.

McKay, G., Mui, E.L.K, Lee, V.K.C. and Cheung, W.H. (2008) ‘Kinetic Modeling of Waste Tire Carbonization’, Energ. Fuels., Vol. 22, pp.1650–1657.

Metha, P. (2010) ‘Science behind acid rain: analysis of its impacts and advantages on life and heritage structures’, S. Asian J. Tourism and Heritage., Vol. 3, pp.123–132.

Mezquita, J.F. and Dols, R.J.F. (1997) ‘Tratados sobre automoviles. Tomo I y II. Tecnologia del automovil’, Universidad Politecnica de Valencia., Valencia, Espana. Vol.1020.

Miller, F.P., Vandome, A.F. and McBrewste, J. (2009) ‘Goodyear. tire and rubber company’, AlphascriptPublishing., Mauricio, Vol. 162.

Miranda, R.C., Segovia, C.C. and Sosa, C.A. (2006) ‘Pyrolysis of Used Tires: Kinetic Study and Infl uence of Operating Variables’, Information Technologic, Vol. 17, Vol. 714.

Mis-Fernandez, R., Azamar, B.J.A. and Rios S.C.R. (2008) ‘Characterization of the powder obtained from wasted tires reduced by pyrolysis and thermal shock process’ Journal of Applied Research and Technology, Vol. 6, pp.95–105.

Morrison, A.C. and Scott, T.W. (2003) ‘Aedes aegypti density and the risk of dengue-virus transmission’, En: Ecological aspects for application of genetically modifi ed mosquitoes. (W. Takken y T.W Scott, Eds.). Kluwer Academic Publishers, Holanda, pp.187–206.

Murillo, R., Aylon, E., Fernandez-Colino, A., Navarro, M.V., Garcia, T. and Mastral, A.M. (2008) ‘Waste tire pyrolysis: comparison between fi xed bed reactor and moving bed reactor’, Ind. Eng. Chem. Res., Vol. 47, pp.4029–4033.

Murillo, R., Navarro, M.V., Garcia, T., Lopez, J.M., Callen, M.S., Aylon, E. and Mastral, A.M. (2005) ‘Production and application of activated carbons made from waste tire’, Ind. Eng. Chem. Res., Vol. 44, pp.7228–7233.

Newspaper the siglo de Torreon. (2005) ‘Producen pavimento con llantas viejas’, Available from: http://www.elsiglodetorreon.com.mx/noticia/134016.producen-pavimento-con-llantas-viejas.html. [Accessed 18 August 2011].

Newspaper the universal. (2008) ‘Crean metodo para reciclar llantas’, Available from: http://www.eluniversal.com.mx/cultura/55905.html [Accessed 18 August 2011].

Oceguera, C.A., Carrillo, G.A., Lopez, N., Bolanos, N.S., Cruz, G.M.J., Wacher, C. and Loza, T.H. (2007) ‘Characterization of the polyurethanolytic activity of two alicycliphilus sp. strains able to degrade polyurethane and N-Methylpyrrolidone’, Appl. Environ. Microb., Vol. 73, pp.6214–6223.

O’Reilly, M. and Keating, J.T. (1984) ‘The Goodyear story. Benjamin Co’, EUA. Vol. 224.Papakonstantinou, C.G. and Tobolski, M.J. (2006) ‘Use of waste tire steel beads in Portland cement

concrete’, Cement Concrete Res., Vol. 36, pp.1686–1691.Parres, F., Crespo, J.E., Nadal, A., Macias, G.A. and Cuerda, C.M.E. (2010) ‘On the Thermal

characterization of fi bers prepared by cryogenic grinding of scrap tires’, Mater. Sci. Forum V., Vol. 636-37, pp.1421–1427.

Pawan, R.S., Pratima, S., Chirika, S.T. and Pradeep, K.B. (2006) ‘Studies and Determination of Heavy Metals in Waste Tyres and their Impacts on the Environment’, Pak. J. Anal. & Envir. Chem., Vol. 7, No. 2, pp.70–76.

Ping, T.L., Leeuwenberg, A.J.M. and Middleton, D.J. (1995) ‘Apocynaceae’, Flora of China, Vol. 16, pp.143–188.

Prevorsek, D.C., Beringer, C.W. and Kwon, Y.D. (1984) ‘Design of tire cords: optimization of viscoelastic properties’, In: ACS Symposium series, polymers for fi bers and elastomers. (Jett, C.A., Diefendorf, R.J., Yen, T.F., Needles, H.L., Schaefgen, J.R., Jaffe, M.and Logothetis,A.L. Eds.). Springer Netherlands, Washington D.C., EUA. Vol. 260, pp.371–395.

Rader, C.P. (1995) ‘Recycling of Rubber’, In: Plastics, Rubber and Paper Recycling. Saddleback, (2008) ‘Recyclin’, Saddleback Educational Publishing., EUA. Vol. 68.

Tyres: destination end 289

Salud, (2009) ‘Responsabilidad familiar y social frente al dengue Secretaria de salud’, PeriodicoMexico sano. Distrito Federal, Mexico. Vol. 13, Vol.14.

Segre, N., Ostertag, C. and Melaragno, M.P.J. (2006) ‘Effect of tire rubber particles on crack propagation in cement paste’, Mater. Res., Vol. 9, pp.311–320.

Semarnat, (2004) ‘Aspectos ambientales del coprocesamiento energetico de llantas de desecho’, Available from: http://www.bvsde.paho.org/bvsacd/cd24/llantas.pdf [Accessed 18 August 2011].

Serumgard, J.R. and Eastman, A.L. (1995) ‘Scrap tire recycling: regulatory and market development progress’, In: ACS Symposium series, Plastics, Rubber and Paper Recycling, A Pragmatic Approach. ( Rader, C.P., Baldwin, S.D., Cornell, D.D., Sadler, G.D. and Stockel, R.F., Eds.). American Chemical Society, Washington D.C., EUA. Vol. 609, pp.237–244.

Seymour, R.B. and Carraher, C.E. (2002) ‘Polimeros Naturales’, 3a ed. Reverte, Barcelona, Espana, Vol. 706.

Snell, C. (2004) ‘The good house book: a common-sense guide to alternative homebuilding: straw bale, cob, adobe, earth plaster & more’, Larks Books. China. Vol. 239.

Sukontasukkul, P. and Chaikaew, C. (2005) ‘Properties of concrete pedestrian block mixed with crumb rubber’, Constr. Build Mater., Vol. 10, pp.1–8.

Teng, H., Chyang, C.S., Shang, S.H. and Ho, J.A. (1997) ‘Characterization of waste tire incineration in a prototype vortexing fl uidized bed combustor’, J. Air & Waste Manage. Assoc., Vol. 47, pp.49–57.

Teng, H., Serio, M.A., Wojtowicz, M.A., Bassilakis, R. and Solomon, P.R. (1995) ‘Reprocessing of used tires into activated carbon and other products’, Ind. Eng. Chem. Res., Vol. 34, pp.3102–3111.

Tsuchii, A., Suzuki, T. and Takeda, K. (1985) ‘Microbial degradation of natural rubber vulcanizates’, Appl. Environ. Microb. Vol. 50, pp.965–970.

Vian, O.A. (1998) ‘‘Quimica industrial’, 2a ed., Reverte, Barcelona, Espana. Vol. 636. Unapumnuk, K., Lu, M. and Keener, T.C. (2006) ‘Carbon distribution from the pyrolysis of tire-

derived fuels’, Ind. Eng. Chem. Res. Vol. 45, pp.8757–8764.Wei, Q., Zhoua, Q., Yu, Z.W., Jing, Z., Wen, W.L., Yan, H.W., Jia, W.Y. and De, Z.W. (2006) ‘Pyrolysis

of waste tire on ZSM-5 zeolite with enhanced catalytic activities’, Polym. Degrad., Stabil. Vol. 91, pp.2389–2395.

Wallace, B.F. (2008) ‘Ciencia depolimeros’, Reverte, Barcelona, Espana.Vol. 608.West, R.C., Page, G.C., Veilleux, J.G. and Choubane, B. (1998) ‘Effect of tire rubber grinding method

on asphalt-rubber binder characteristics’, Transp. Res. Record., Vol. 1638, pp.134–140.White, J.L. (1995) ‘Rubber processing, Technology-Materials-Principles’, Hanser/Gardner

Publications Inc., New York, EUA. Vol. 586.White, J.L. and Kim, K.J. (2008) ‘Thermoplastic and rubber compounds: technology and physical

chemistry’, Hanser/Gardner Publications Inc., Cincinnati, EUA. Vol. 301.Williams, P.T., Besler, S., Taylor, D.T. and Bottrill, R.P. (1995) ‘The pyrolysis of automotive tyre

waste’, J. Inst. Eng., Vol. 68, pp.11–21.(Rader, C.P., Baldwin, S.D., Cornell,D.D., Sadler,G.D. and Stockel, R.F., Eds.).