Environmental Drivers: Impacts and Benefits

6.1 Direct environmental and cost benefits in manufacture:

6.1.1 The manufacture of tyres requires energy and materials which ultimately impact on both the global and local environment. The practice of retreading extends the useful life of a tyre thereby maximising the use of the raw materials and the energy used. This section reviews the energy requirements for retreading and quantifies the embedded energy used in the production of the materials to make a tyre. The environmental impacts created by tyre disposal, and the benefits that retreading can contribute to minimising this impact, are then outlined.

6.1.2 During the course of the current study, site audits were carried out at six UK retreading plants. The results from the audits of car tyre retreaders are summarised in Table Two. These results are compared with data taken from the BLIC life cycle assessment study1 as well as data from a recent life cycle analysis (LCA) carried out on behalf of the Environment Agency (EA). All data are normalised relative to one kilogramme of an average model car tyre. (Except the BLIC New Tyre data).

6.1.3 It should be stressed that the audit data is averaged from three companies. Moreover, production volumes are significantly lower for retreading operations. These data suggest that new tyre manufacturers do not necessary benefit from economies of scale in terms of energy use. In terms of specific energy inputs to the retread process, there appears to be very little difference between the data obtained from the audit data calculations, the BLIC new tyre data and the EA LCA study. The BLIC energy data for retreaded tyres is notably higher, however, the report does not offer an explanation for the difference between new and retreaded tyres. Differences between New Tyre Manufacturers:

6.1.4 The three audits carried out for car tyres during this study show very similar levels of performance between the different retreading sites. This correlates with the findings of the BLIC study, which compared the impacts of eight production plants. The main reason for the differences that did occur in the BLIC study were thought to be: differences in car tyre formulations; different car tyre weights; different electricity generation mixes (some sites are located in countries with significantly higher pollution levels per kWh than others); and differences in the completeness of the data.

6.1.5 The main benefit of retreading is the ability to save resources used in new tyre manufacture. The data in Table 1 shows that ~6.5kg of rubber and steel re-inforcement material of materials are saved by retreading as opposed to new tyre manufacture. Each of the materials (e.g. synthetic/natural rubber, carbon black, aromatic oils, etc) will have further significant life cycle savings from their avoided use and manufacture. The quantities of materials saved, and the energy required to process and manufacture, an average European car tyre (as defined by the BLIC report) are shown in Table 2.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3 Total resource (oil and rubber) used in material manufacture and tyre processing operations for new and retreaded tyres 3

 

 

 

 

6.1.6 The quantities of materials used (percentage composition) and the energy required for each constituent have been compiled as part of the BLIC study, with the exception of synthetic rubber. The figure for this material has been taken from one of a series of eco-profiles compiled for the Association of Plastics Manufacturers in Europe. The energy figure presented for synthetic rubber includes the energy requirement to produce the material from a crude oil feedstock.
The data compiled in Table 2 has been used to calculate the kJ/kg and kJ/tyre which are required. On the basis of the percentage composition, energy requirements and casing weight assumed by the BLIC study, ~4.69 kWh/tyre are saved for each car tyre that is retreaded in addition to the materials used. In 1995 across the UK this would have equated to 14 - 19.5 GWh of saved energy by retreading car tyres, but by 2001 the collapse of the retread market reduced this amount of saved energy to 3 - 4 GWh. The estimated amount of embedded energy saved depends on the composition of the tyres.

 

 

6.2 Reduction in landfill use

6.2.1 Although retreaded tyres eventually have to be disposed of, retreading is seen as one of the options for reducing the number of tyres going annually to landfill. Retreading extends the life of a tyre casing, thereby putting off the time when the worn tyre casing requires disposal. Each sale of a retread tyre also replaces the sale of a new tyre, thereby reducing the amounts of new tyres that need to be produced. Thus the 'pool' of tyres in use remains in use longer, and input and output rates of new and worn-out tyres respectively are reduced as levels of retreading increase

6.2.2 The main driver for reducing landfill of tyres will be legislation (Landfill Directive implemented through the Landfill Regulations). By 2006, landfill disposal of tyres (whole 2003 and shredded 2006) will be banned, effectively imposing a 100% recovery requirement on waste tyres. The Government is currently consulting on views about interim recovery targets of 85% for 2004 and 92% for 2005.
The quantities of tyres which are sent to landfill also include other largely unquantified disposal routes including stockpiles and illegal dumping. Tyres sent to landfill are not necessarily recorded as a specific waste and can be mixed with general waste. The Viridis study has estimated that in 1998 alone 23,000 tonnes of tyres were stockpiled and in one English county ~2,000 tonnes of tyres are illegally dumped annually4. The actual numbers sent to landfill are therefore difficult to accurately quantify. The trend figures for different disposal routes are approximately as follows:

6.2.3 If the downward trend in retreading was restored to 1995 levels an additional ~75,000 tonnes of tyres (all categories) could be hypothetically diverted from other disposal routes. This weight is equivalent to nearly 40% of the quantity of tyres sent to landfill or other unclassified or unauthorised disposal site. It should be noted that the import and export of retreaded tyres means that the above figure is only an indicative broad guide.

6.2.4 Estimates based on potential improvements in the management of tyres retreaded for commercial vehicles, as well as changes in driver behaviour, could yield an increase of 24% of tyres that could be retreaded. At current levels of retreading an additional ~13,200 tonnes. This lower bound estimate is entirely plausible given workable incentives within the sector.

 

 

 

 

6.2.5 Clearly, the decline in levels of retreading over the period 1995-2001 (Figure 1) has not helped the recovery situation. If retreading levels could be increased back to 1995 levels, then this would provide a major contribution (~75,000 tonnes) towards achieving the Government's suggested targets for waste tyre recovery.

6.3 Effects of final disposal methods.

6.3.1 Even if the market for retreaded tyres does rise considerably, there will also continue to be a need to find alternative disposal and recovery routes once a tyre can no longer be retreaded. Both the BLIC and Viridis study have evaluated the relative impacts of the different disposal routes. BLIC found that all disposal options apart from landfill had a very small or negative environmental load1. BLIC concluded that: "Of all the end-of-life processes, landfilling is the least attractive option". Viridis, on the other hand, found that when they compared the impacts of each option, assuming all tyres went to that option, energy recovery was the only one which had a higher impact than the 1998 scenario (Figure 3).

 

 

 

 

 

 

 

Figure 3 - Changes in resource inputs and outputs for used tyre processing assuming all used tyres are selected for one specific disposal option (i.e. All reuse, all recycled etc.)(Viridis Study)4

6.3.2 It is clear therefore that some confusion remains over the merit of some waste management options. Furthermore, examination of newer technologies for dealing with tyres is required.

6.3.3 The Environment Agency has commissioned further work looking into the life-cycle assessment of management options for waste tyres. This study is still under review awaiting publication. The goal of the study is to compare different waste management options for car tyres in the UK, using life-cycle assessment (LCA) to evaluate the environmental advantages and disadvantages of each option. The results of the study will help the Environment Agency to make an assessment of the future waste management options for tyres, and to inform national strategy and help set national priorities for this waste stream. The study was restricted to car tyres only (car tyres account for almost 90% by number of the used tyres arising in the UK). The study examined a range of management options 1* for waste tyres including:

· Export · Retreading
· Crumbing for flooring applications
· Engineering applications (i.e. use as drainage fill)
· Use as tyre bales in sea defences
· Combustion in cement kilns
· Pyrolysis
· Microwave treatment, and
· Gasification

6.3.4 Using the CML (Centre for Environmental Studies, Leiden, Netherlands) impact assessment methodology, a set of impact categories was defined into which the effects of the different resource inputs and emissions can be grouped. These categories, referred to as the Problem Oriented Approach, were:

Table 5 - Environmental Impact Categories

 

 

 

 

 

 

 

6.3.5 For some impact categories, particularly human, aquatic and terrestrial ecotoxicity, a number of simplifying assumptions are made in the modelling used to derive characterisation factors, and their adequacy in representing impacts is still the subject of some scientific discussion. However they are still widely used, and therefore these impact categories were included (shown in italics in the above table) in the assessment as issues of interest, and were accompanied by caveats describing their deficiencies.

6.3.6 The study 2* found that all waste management routes considered exhibited some environmental benefits - indeed, export, retreading, use in sea defences and pyrolysis (CHP configuration) provided benefits over all impact categories assessed. With few exceptions, these results are not sensitive to the sensitivity analyses carried out for the study. For comparison of the performance of each waste management option against a particular impact category, the results for each option have been ranked against each other for each impact category 3*. The best and worst impact scores for each impact category assessed are shown in Table 6.

 

 

 

 

 

 

6.3.7 In addition, the impacts have been listed in order of significance compared with emissions from Western Europe in 1995 (i.e. normalised). The greatest contribution made to any impact is by Retreading and this was the contribution to the Abiotic Depletion (Resource depletion) impact category. The impact contribution to Abiotic Depletion of 1 tonne of retreaded car tyres provides an environmental saving, equivalent to the resource consumption of a car travelling over 23,000 kilometres.

6.3.8 The Environment Agency's policy at present is to support a range of different options, including energy recovery, as long as they are sustainable and do not lead to unacceptable impact on the environment. Clearly, on the basis of LCA, there is a strong case for the involvement of retreading and combustion in cement kilns options for the management of waste tyres.

6.4 Implications for the Disposal of Tyres

6.4.1 Corporate social responsibility and ISO 14001 are two increasingly strong influences for many corporate purchasers. They have QA systems in place which require them to procure, use and dispose of resources in an environmentally and socially responsible manner. Similar pressures also exist for Government, which has to live up to new standards evolving under the "Greener Government" initiative. The use of retreaded tyres within supply chains or transport services could help to fulfil these goals.

6.4.2 Another way in which organisations can demonstrably reduce their impact on the environment is to ensure that their used tyres are dealt with in an appropriate way. This ensures that the population from which quality casings can be selected is at least maximised. As a minimum demonstration of compliance with their environmental systems, organisations should ensure that the company with whom they interact on tyre services complies with waste management legislation, and that the waste will be transferred to a licensed waste management site.

6.4.3 Some organisations, however, may wish to go beyond basic compliance, for example as part of an objective set under an Environmental Management System (EMS). The Responsible Recyclers Scheme (RRS) set up by the Tyre Industry Council in 1999 has potential to help organisations do this. The RRS is a voluntary scheme which audits its members to ensure that they demonstrate to auditors and customers that they reuse and recycling tyres in ways which comply with UK and European Legislation. It includes a system of tyre recovery notes which help to keep a track of where the waste is going and can be used for compliance or statistical purposes. At present there are 15 members of the RRS and between them it is thought that they handle almost 80% of the UK's scrap car tyre arisings.5 If more companies decide to take this route it could lead to a greater demand for retreading as it is seen as a major recycling option. Procurement contracts by both private sector and Government could include environmental conditions such as the use of retreaded tyres for vehicles.

6.4.4 The main disadvantage with the RRS is the high cost to members especially the cost of being audited. This has led to concern that smaller companies are being excluded from the scheme. To try and overcome this barrier scheme members have appointed a single audit company to reduce costs and the British Rubber Manufacturers' Association are funding 50% of the costs in 2003 to help support the members. Until RRS has a wider range of companies however, use of its services could conflict with some CSR requirements.

6.4.5 There is no direct study looking at the environmental performance of retreaders but there is evidence of improvement in the performance of new tyre manufacturers. The two areas where improvements have been specifically highlighted are the reduction of solvent use and improvements in energy efficiency. According to the Environment Agency some producers had virtually eliminated the use of solvent by 1998.6 This reduction is likely to have increased since the introduction of the solvents emissions directive 1999/13/EC. Savings of up to 30% in energy use have been reported by tyre manufacturers in the last 20 years.7
The recent audits of both commercial vehicle and car tyre retreading companies clearly demonstrated that waste management is rationalised where ever possible. Where possible scrap rubber is separated and reused for other purposes (carpet underlay, equestrian centres) or is sent for energy recovery

6.5 Conclusions:

6.6 Recommendations:

6.7 References:

1. BLIC European Association of the Rubber Industry 2001. Life Cycle Assessment of an Average European Car Tyre. BLIC.
2. I Boustead & D L Cooper, Eco-profile of SBS Thermoplastic Elastomers - for The International Institute of Synthetic Rubber Producers (IISRP) - August 1998.
3. RMA Retread news, Issue number 3.
4. Viridis (2001) Tyre Mass balance Study.
5. Tyre Industry Council (2003) TIC Responsible Recyclers Scheme Eighteen Months On [http://www.tyresafety.co.uk/].
6. Environment Agency 1998 Tyres in the Environment. Environment Agency.
7. Dunlop Tyres 2001 Tyre Law http://www.driveradviser.com/tyre/the_law.shtml.