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Publications
Commonwealth Department of Environment, 2001
The data on the rate of generation of waste tyres in Australia are incomplete and gaps are detailed above. The availability of time series information, in particular, is limited and the analysis of trends presented below has relied on indirect methods using parameters for which data and projections are available.
For tyres the most straightforward approach is to base predictions of waste generation on tyre usage, as measured by the number and type of vehicles and the distance travelled. Using these primary factors it is possible to predict the number of waste tyres generated using a model that takes into account:
Forecasts for the number of waste tyres generated in the future, based on our best understanding of these factors, are presented in Figure 7.10.
Figure 7.1035 Preliminary estimates of the trend over time in the number of waste tyres generated in Australia
The net increase in the generation rate of waste tyres is forecast to be approximately 2% per year, driven by increases in population, vehicle ownership and distance travelled, assuming constant retreading rates and tyre design life. By the year 2010, the number of waste tyres is forecast to be in excess of 20 million, from the current level of 18 million.
The rate of retreading has a significant impact on waste tyre generation. In the forecasts above it has been assumed that the current rate of retreading for passenger tyres is 20% and that this remains constant over the prediction period. It has been indicated by a number of parties that retreading is declining. Every 1% decrease in the rate of passenger tyre retreading results in an increase of approximately 1% in the rate that waste passenger tyres are produced. For truck tyres the impact is more significant because they are retreaded more than once so that a 1% decrease in the rate of retreading results in a 2% increase in the rate that waste truck tyre are generated.
One factor that influences waste tyre generation rates that is not taken into consideration is the lag between when a tyre is fitted to a vehicle and when it is scrapped. A passenger tyre is assumed to have an average design life of 50,000 to 60,000 km. This is reduced by 10% to account for usage and maintenance factors which, in combination with the retreading rate, results in an apparent life of the average passenger tyre of about 56,000 km. At an average distance travelled of 15,000 km per year the life of a tyre is estimated to be between 4 and 5 years. For truck and bus tyres the average life is 6 to 7 years due to longer design life and multiple retreadings. Accordingly, the estimate for the generation rate for waste tyres (as calculated above) is actually a prediction for the number of waste tyres that will be produced several years in the future. This factor introduces an error of between 5% and 14% in the predicted waste tyre generation rate. However, as the overall accuracy of the estimates from the model is probably of the order of ±10 to 20%, due to uncertainties in the values of the modelling parameters, this simplification is considered to have only a relatively minor effect on the interpretation of the results.
Applying the per person generation rates derived from the above model to the relevant population statistics, it is possible to estimate the number of waste tyres that are produced in urban and country regions in the various States and Territories for the major vehicle/tyre types, as listed in Table 7.7. The figures computed from this process are acceptably close to the estimates provided by the various State agencies and other sources as listed in Table 7.6, confirming the validity of the model.
Urban includes both capital cities and major regional cities. It is estimated that over 65% of tyres are generated in major urban centres. ABS vehicle usage statistics36 estimate that 54% of the total kilometres travelled in Australia occurs in capital cities, which can be related directly to the generation rates for waste tyres.
Table 7.7 Model estimates for number of waste tyres for Australian States and Territories disaggregated by urban and country regions nominally for the year 200037
| Number of tyres | ||||||||
|---|---|---|---|---|---|---|---|---|
| ACT | NSW | NT | QLD | SA | TAS | VIC | WA | |
| Urban | ||||||||
| Passenger | 158,431 | 1,853,086 | 35,651 | 1,189,043 | 556,763 | 125,509 | 1,838,234 | 611,095 |
| Light commercial | 35,708 | 417,657 | 8,035 | 267,992 | 125,486 | 28,288 | 414,310 | 137,731 |
| Truck and bus | 9,103 | 106,472 | 2,048 | 68,319 | 31,990 | 7,211 | 105,619 | 35,112 |
| Total (EPU) | 275,362 | 3,220,761 | 61,963 | 2,066,620 | 967,684 | 218,141 | 3,194,948 | 1,062,115 |
| Country | ||||||||
| Passenger | 0 | 1,421,898 | 62,870 | 605,012 | 205,875 | 114,693 | 568,669 | 339,482 |
| Light commercial | 0 | 320,474 | 14,170 | 136,360 | 46,401 | 25,850 | 128,169 | 76,514 |
| Truck and bus | 0 | 81,698 | 3,612 | 34,762 | 11,829 | 6,590 | 32,674 | 19,506 |
| Total (EPU) | 0 | 2,471,334 | 109,272 | 1,051,544 | 357,822 | 199,342 | 988,376 | 590,038 |
| EPU based % of total | ||||||||
|---|---|---|---|---|---|---|---|---|
| ACT | NSW | NT | QLD | SA | TAS | VIC | WA | |
| Urban | ||||||||
| Passenger | 0.9% | 11.0% | 0.2% | 7.1% | 3.3% | 0.7% | 10.9% | 3.6% |
| Light commercial | 0.4% | 5.0% | 0.1% | 3.2% | 1.5% | 0.3% | 4.9% | 1.6% |
| Truck and bus | 0.3% | 3.2% | 0.1% | 2.0% | 1.0% | 0.2% | 3.1% | 1.0% |
| Sub total | 1.6% | 19.1% | 0.4% | 12.3% | 5.7% | 1.3% | 19.0% | 6.3% |
| Country | ||||||||
| Passenger | 0.0% | 8.4% | 0.4% | 3.6% | 1.2% | 0.7% | 3.4% | 2.0% |
| Light commercial | 0.0% | 3.8% | 0.2% | 1.6% | 0.6% | 0.3% | 1.5% | 0.9% |
| Truck and bus | 0.0% | 2.4% | 0.1% | 1.0% | 0.4% | 0.2% | 1.0% | 0.6% |
| Sub total | 0.0% | 14.7% | 0.6% | 6.2% | 2.1% | 1.2% | 5.9% | 3.5% |
| Total | 1.6% | 33.8% | 1.0% | 18.5% | 7.9% | 2.5% | 24.8% | 9.8% |
Using road transport statistics it is also possible to make estimates of the contribution that each individual travel purpose makes towards generating waste tyres. For passenger tyres the distance travelled for each activity can be assumed to be directly proportional to the number of waste tyres generated. According to ABS statistics, 51% of total passenger car distance travelled is for private use, 24% is for travel to and from work and 25% is work/business related.
Similar breakdowns are not possible for trucks, but it is of interest to make a comparison of the transport task (freight carried) with the estimated number of waste tyres generated for different truck types, as listed in Table 7.8.
| Truck Type | Million tonne km | Total waste tyres generated | % of total waste tyres | Tyres/million tonne km |
|---|---|---|---|---|
| Articulated | 99,303 | 385,619 | 19% | 4 |
| Rigid truck | 22,916 | 184,013 | 9% | 8 |
| Light commercials | 5092 | 1,480,657 | 72% | 291 |
The high value for light commercials vehicles in Table 7.8 is, in part, due to the fact that a significant proportion of the light commercial fleet do not carry freight. Nevertheless, the ‘tyre efficiency’ is related strongly to the higher general efficiency of executing the transport task by larger vehicles.
Of the total distance travelled, 54% was in the capital city of the State/Territory in which the vehicle was registered and again this can be assumed to relate directly to the percentage of tyres generated.
Based on this analysis it is possible to derive an overall breakdown of the total number of tyres generated in different areas as a proportion of the total number, as summarised below. This analysis is restricted to the tyre types listed in Table 7.7, such that:
Over the past several years there has been an increasing number of smaller vehicles. This does not affect the number of waste tyres generated but does affect the characteristics of the waste tyres. Smaller vehicles have smaller tyres that weigh less and contain less rubber and other materials (a small passenger tyre may weigh 2 or 3 kg less than a standard 9.5 kg tyre). Smaller (whole) tyres do not occupy a proportionally smaller volume and still require a comparable level of handling as a larger tyre. The significance of the trend to smaller vehicles to tyre recyclers is not clear, except that they will essentially face a reduced material return for a similar effort. In extreme cases it could result in price differentials for waste tyres within the passenger tyre category, or possibly selective exclusion of small tyres from recycling.
35Note that the graph shows passenger, light commercial and truck and bus tyres only. Total estimated EPU in the figure are therefore lower than 18 million EPU due primarily to the exclusion of OTR and agricultural tyres.
36ABS (2000), Document No 9208 Survey of Motor Vehicle Use in Australia
37Columns do not sum directly as the values for the tyres are number are number of tyres and the total is in EPU (Equivalent Passenger Units). To calculate the total multiply the number of tyres by the EPU for each tyre type.