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G6 Summary of Results 2007/08

In this summary of the results from the four surveys undertaken as part of the SWAP Data Programme, comparisons between the results of the four surveys are presented for:

  • the compositions of the four activity sources that make up the general waste stream at both the transfer pit and disposal face

  • the tonnages of the four activity sources and the general waste stream at both the transfer pit and disposal face

  • the compositions of the general waste stream at both the transfer pit and disposal face

  • the tonnages of the waste streams that make up the overall waste stream, both including and excluding cover material

  • the compositions of the overall waste stream, both including and excluding cover material.

G6.1 Transfer pit activity sources

G6.1.1 Construction and demolition waste to transfer pit

The primary composition of C&D waste from the four surveys is shown in Figure G6.1.

Figure G6.1: Composition of C&D waste to transfer pit, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 2% 3% 4% 5%
Plastics 1.1% 2% 3% 3%
Putrescibles 1.0% 3% 1.4% 3%
Ferrous metals 4% 5% 2% 4%
Non-ferrous metals 0.1% 0.1% 0.3% 0.2%
Glass 2% 2% 1.0% 0.2%
Textiles 3% 0.4% 2% 7%
Nappies and sanitary 0.0% 0.0% 0.0% 0.1%
Rubble 30% 25% 43% 26%
Timber 57% 60% 42% 53%
Rubber 0.3% 0.0% 0.0% 0.4%
Potentially hazardous 0.2% 0.2% 0.2% 0.2%

In each of the four surveys, rubble and timber were the largest components of C&D waste. Rubble (such as concrete) was the largest component in three of the four surveys, and timber in the fourth. Although there is variation between surveys in terms of their relative proportions, in every survey rubble and timber (when combined) comprised over three-quarters of C&D waste. No other material comprised more than 5 per cent of the total.

G6.1.2 Industrial/commercial/institutional waste to transfer pit

The primary composition of ICI waste from the four surveys is shown in Figure G6.2.

Figure G6.2: Composition of ICI waste to transfer pit, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 25% 14% 16% 19%
Plastics 14% 8% 10% 13%
Putrescibles 5% 8% 3% 5%
Ferrous metals 13% 9% 10% 6%
Non-ferrous metals 0.2% 0.4% 0.6% 0.5%
Glass 4% 6% 13% 9%
Textiles 10% 19% 11% 23%
Nappies and sanitary 0.6% 0.8% 1.4% 2%
Rubble 6% 3% 4% 2%
Timber 19% 29% 29% 20%
Rubber 3% 3% 2% 0.7%
Potentially hazardous 0.7% 0.7% 0.1% 0.5%

ICI waste was relatively heterogeneous, with no single material comprising over 30 per cent of the total in any of the surveys. In three of the four surveys a different waste category comprised the largest proportion (ie, the paper category was largest in the first survey, timber in the second and third surveys, and textiles was the largest proportion of ICI waste disposed of at the transfer pit in the fourth survey).

There is also, for some categories, little consistency between surveys in the proportion of the materials present. For example, the proportion of textiles varied from 10 to 23 per cent, whereas other categories were more consistent between surveys. This variability reflects both the nature of this activity source as well as the small scale of the ICI waste stream disposed of at the transfer pit. A few loads of a particular material (such as used clothing from a second-hand store) could have a substantial effect on the composition measured during the survey period.

G6.1.3 Landscaping and earthworks waste to transfer pit

The primary composition of landscaping and earthworks waste from the four surveys is shown in Figure G6.3.

Figure G6.3: Composition of landscaping and earthworks waste to transfer pit, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 1.4% 3% 1.2% 3%
Plastics 1.0% 2% 0.8% 2%
Putrescibles 55% 60% 42% 56%
Ferrous metals 0.3% 2% 1.0% 2%
Non-ferrous metals 0.5% 0.0% 0.0% 0.0%
Glass 0.4% 0.8% 0.5% 2%
Textiles 0.6% 2% 0.8% 0.1%
Nappies and sanitary 0.4% 0.2% 0.3% 0.2%
Rubble 33% 21% 50% 24%
Timber 8% 9% 3% 10%
Rubber 0.0% 0.9% 0.0% 2%
Potentially hazardous 0.1% 0.1% 0.0% 0.1%

Results from the four surveys show that the composition of the landscaping and earthworks activity source is made up of two main categories: putrescibles and rubble. In all of the four audits, green waste and rubble combined represented between 79 and 92 per cent of the total weight.

G6.1.4 Residential waste to transfer pit

The primary composition of residential waste from the four surveys is shown in Figure G6.4.

Figure G6.4: Composition of residential waste to transfer pit, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 7% 11% 11% 13%
Plastics 7% 8% 9% 9%
Putrescibles 11% 12% 12% 11%
Ferrous metals 13% 14% 11% 11%
Non-ferrous metals 0.4% 0.7% 1.0% 0.6%
Glass 4% 5% 5% 4%
Textiles 20% 17% 18% 17%
Nappies and sanitary 0.8% 2% 2% 1.2%
Rubble 6% 4% 4% 6%
Timber 30% 27% 27% 25%
Rubber 1.1% 1.4% 0.6% 2%
Potentially hazardous 0.5% 0.6% 0.6% 0.6%

Residential waste is relatively heterogeneous, with no single category of material comprising more than 30 per cent of the total in any of the surveys. In all of the surveys timber was the largest classification and textiles the second largest. All of the 12 primary waste categories are relatively consistent across the four surveys.

G6.2 Transfer pit general waste

General waste discharged at the transfer pit at Green Island Landfill is defined as waste generated from four different activity sources: C&D, ICI, landscaping and earthworks, and residential (as illustrated in Figure G1.1). Figure G6.5 presents the tonnage of waste from each activity source for each of the four surveys.

Figure G6.5: Tonnage of activity sources of general waste to transfer pit, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Construction and Demolition 59 56 38 47
Industrial/Commercial/ Institutional 26 28 29 31
Landscaping and Earthworks 21 33 9 7
Residential 118 97 71 65
Total General Waste 224 215 146 149

Figure G6.5 shows that the total quantity of general waste disposed of decreased markedly between the second and the third audits. The quantity of three of the activity sources decreased between the first and fourth audits, with only ICI waste showing an increase (of 19 per cent). Although residential waste was the largest activity source in each of the audits, the tonnage decreased by 45 per cent between the first and fourth audits.

The tonnage of C&D waste was lowest in the March survey, which may relate to seasonal trends in the construction industry. ICI waste was the most consistent of the four waste streams. Wastes from landscaping and earthworks activities were the lowest in three of the four surveys, with a peak in the early summer audit in December. The decrease in residential waste through the year may have been due to seasonal factors, or it may be related to student activity, but it could also have been related to general economic conditions and householders being reluctant to pay disposal charges in a tightening economy.

Figures G6.6 and G6.7 present the variation in the composition of the general waste stream through the four surveys conducted in 2007/08. Figure G6.6 shows the tonnage of each of the 12 primary categories disposed of during each of the survey periods; the mean tonnage is also shown in the figure. Figure G6.7 shows the percentage of the general waste stream for each of the 12 primary SWAP categories.

Figure G6.6: Tonnage of general waste to transfer pit, by primary categories, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May Mean
Paper 17 17 14 17 16
Plastics 13 12 10 12 12
Putrescibles 26 35 14 13 22
Ferrous metals 21 19 11 11 16
Non-ferrous metals 1.0 1.0 1.0 1.0 1.0
Glass 7 7 8 6 7
Textiles 28 22 17 22 22
Nappies and sanitary 1.0 2 1.0 1.0 1.3
Rubble 33 26 25 18 26
Timber 75 71 44 48 60
Rubber 2 3 1.0 2 2
Potentially hazardous 1.0 1.0 1.0 1.0 1.0

Figure G6.7: Primary composition of general waste to transfer pit, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 8% 8% 9% 11%
Plastics 6% 6% 7% 8%
Putrescibles 12% 16% 9% 9%
Ferrous metals 9% 9% 8% 7%
Non-ferrous metals 0.3% 0.4% 0.7% 0.4%
Glass 3% 3% 5% 4%
Textiles 12% 10% 12% 15%
Nappies and sanitary 0.5% 0.8% 1.0% 0.9%
Rubble 15% 12% 17% 12%
Timber 34% 33% 30% 32%
Rubber 0.9% 1.2% 0.6% 1%
Potentially hazardous 0.4% 0.4% 0.4% 0.4%

The graphs show that although timber makes up the largest proportion of general waste in each survey, the tonnage decreases substantially between the second and third surveys. Much of this change is related to the decrease in residential waste during that period. In terms of tonnage, rubble is the second largest constituent in the first and third surveys, putrescibles in the second, and textiles in the fourth. The tonnage for several of the materials, such as paper, plastics and glass, is relatively consistent between surveys, while others vary substantially.

The average proportions of the 12 SWAP primary waste categories that make up general waste are presented in Figure G6.8. The average composition is calculated using results from the four visual surveys conducted in 2007/08 and is based on the tonnages of the different materials. These are the mean figures from Figure G6.6 expressed as percentages.

Figure G6.8: Average primary composition of general waste to transfer pit, 2007/08

Primary category % of total
Paper 9%
Plastics 6%
Putrescibles 12%
Ferrous metals 8%
Non-ferrous metals 0.5%
Glass 4%
Textiles 12%
Nappies and sanitary 0.7%
Rubble 14%
Timber 32%
Rubber 1.1%
Potentially hazardous 0.5%

Timber makes up the largest component of the general waste stream (32 per cent), reflecting the large proportion of waste generated from residential activity (refer Figure G6.5). The paper, putrescibles, ferrous metals, textiles and rubble categories each make up between 8 and 14 per cent of the general waste composition.

G6.3 Disposal face activity sources

G6.3.1 Construction and demolition waste to disposal face

The primary composition of C&D waste discharged at the disposal face from the four surveys is shown in Figure G6.9.

Figure G6.9: Composition of C&D waste to disposal face, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 1.0% 0.6% 0.9% 0.7%
Plastics 1.3% 2% 1.0% 0.6%
Putrescibles 0.6% 3% 4% 2%
Ferrous metals 3% 4% 3% 2%
Non-ferrous metals 0.1% 0.1% 0.8% 0.1%
Glass 0.2% 0.1% 0.3% 0.0%
Textiles 2% 0.5% 1.2% 0.9%
Nappies and sanitary 0.0% 0.0% 0.0% 0.0%
Rubble 69% 57% 61% 76%
Timber 22% 34% 28% 18%
Rubber 0.1% 0.0% 0.0% 0.2%
Potentially hazardous 0.2% 0.1% 0.1% 0.2%

Rubble (such as concrete) was easily the largest component of C&D waste in all of the four surveys, and timber the second largest. Together, rubble and timber comprised over 89 per cent of the total in each of the surveys.

Although the survey samples were relatively large, comparing the results shows that the composition of the C&D waste stream still varies substantially between the surveys. This variability from week to week is largely due to the small number of large C&D projects contributing to the waste in any given survey period. One week the major C&D project disposing of waste at the facility may involve the demolition of a concrete structure, resulting in large amounts of rubble; another week the major demolition project may involve a timber building.

G6.3.2 Industrial/commercial/institutional waste to disposal face

The primary composition of ICI waste from the four surveys is shown in Figure G6.10.

Figure G6.10: Composition of ICI waste to disposal face, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 17% 20% 17% 16%
Plastics 20% 12% 14% 18%
Putrescibles 15% 10% 13% 8%
Ferrous metals 5% 4% 5% 3%
Non-ferrous metals 0.6% 0.8% 2% 0.9%
Glass 16% 19% 17% 18%
Textiles 6% 4% 4% 4%
Nappies and sanitary 3% 2% 3% 1.1%
Rubble 8% 14% 8% 21%
Timber 9% 11% 8% 12%
Rubber 0.4% 4% 9% 0.2%
Potentially hazardous 0.7% 0.5% 1.2% 0.3%

ICI waste was relatively heterogeneous, with no single material comprising over 21 per cent of the total in any of the surveys. The plastics category was largest in the first survey, paper in the second and third, and rubble in the fourth. For most of the categories there is reasonable consistency across surveys in terms of the proportion of the materials present. Of the major categories, only rubble varies substantially across the surveys.

G3.3.3 Landscaping and earthworks waste to disposal face

The primary composition of landscaping and earthworks waste from the four surveys is shown in Figure G6.11.

Figure G6.11: Composition of landscaping and earthworks waste to disposal face, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 0.2% 0.3% 0.2% 0.0%
Plastics 0.3% 0.2% 0.5% 0.0%
Putrescibles 53% 29% 39% 9%
Ferrous metals 0.0% 0.2% 0.7% 0.1%
Non-ferrous metals 0.0% 0.0% 0.0% 0.0%
Glass 5% 0.0% 0.1% 0.0%
Textiles 0.1% 0.1% 0.3% 0.0%
Nappies and sanitary 0.0% 0.0% 0.0% 0.0%
Rubble 40% 69% 57% 90%
Timber 2% 0.9% 2% 0.4%
Rubber 0.0% 0.0% 0.0% 0.0%
Potentially hazardous 0.0% 0.0% 0.0% 0.0%

Results from the four surveys show that the landscaping and earthworks activity source is generally made up almost exclusively of two primary waste categories: putrescibles and rubble, which together comprised over 93 per cent of the total in all four surveys. In three of the four surveys rubble was the largest component, with between 57 and 90 per cent of the total weight. In the first survey putrescibles was the largest category, comprising 53 per cent of the total.

The increase in the proportion of rubble and the concomitant decrease in putrescibles as a proportion of the total is related to changes in gate charges and a change in load classification by the weighbridge. Between the second and third surveys a charge was introduced for cover material, which had previously been disposed of for no charge (see Section G4.4.2.2). After this occurred the weighbridge started classifying loads differently, with loads that had previously been classified under the product code for free cover material being classified under different product codes. These product codes were classified as general waste (see Appendix G2) for the first two surveys, and to be consistent were also classified as general waste for the third and fourth surveys. This change in procedure resulted in an increase in loads that were primarily soil (rubble) being classified as general waste.

G6.3.4 Residential waste

The primary composition of residential waste from the four surveys is shown in Figure G6.12.

Figure G6.12: Composition of residential waste to disposal face, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Paper 4% 5% 6% 5%
Plastics 4% 3% 6% 4%
Putrescibles 19% 21% 15% 17%
Ferrous metals 12% 13% 14% 16%
Non-ferrous metals 0.5% 0.8% 0.7% 0.6%
Glass 2% 1.3% 4% 2%
Textiles 10% 10% 15% 11%
Nappies and sanitary 0.1% 0.2% 0.1% 0.0%
Rubble 18% 11% 8% 7%
Timber 30% 35% 31% 35%
Rubber 0.3% 0.5% 0.6% 2%
Potentially hazardous 0.5% 0.6% 0.8% 0.9%

Residential waste is relatively heterogeneous, with no single category of material comprising more than 36 per cent of the total in any of the surveys. In all of the surveys, timber was the largest classification. In three of the four surveys, putrescibles was the second largest classification but comprised less than 21 per cent of the total. In the third survey, textiles was marginally the second largest classification.

G6.4 General waste to disposal face

General waste discharged at the disposal face is defined as waste being generated from four different activity sources: C&D, ICI, landscaping and earthworks, and residential (as illustrated in Figure G1.1). Figure G6.13 presents the tonnage of waste from each activity source for each of the four surveys.

Figure G6.13: Tonnage of activity sources of general waste to disposal face, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May
Construction and Demolition 142 103 163 230
Industrial/Commercial/ Institutional 137 161 120 171
Landscaping and Earthworks 51 107 283 571
Residential 23 31 58 26
Total General Waste 353 401 624 998

Figure G6.13 shows that the total quantity of general waste disposed of increased markedly after the second survey, with much of this coming from an increase in landscaping and earthworks. As explained in Section G6.3.3, between the second and third surveys a charge was introduced for cover material, which previously had been disposed of for no charge. After this occurred, the weighbridge started classifying loads differently, with loads that had previously been classified under the product code for free cover material being classified under different product codes that are included as general waste (see Appendix G2).

C&D and residential loads varied substantially through the four surveys, with the maximum tonnages being over twice the minimum tonnages. ICI tonnages were more consistent.

Figures G6.14 and G6.15 on the following page show the variation in the composition of the general waste stream through the four surveys conducted in 2007/08. Figure G6.14 shows the tonnage of each of the 12 primary categories disposed of during each of the survey periods; the mean percentage is also shown in the figure. Figure G6.15 shows the tonnage of the general waste stream discharged at the disposal face for each of the 12 primary SWAP categories.

Figure G6.14: Tonnage of general waste to disposal face, by primary categories, 2007/08

Primary category 6-12 August 1-7 December 1-7 March 25-31 May Mean
Paper 26 35 26 30 29
Plastics 30 22 24 32 27
Putrescibles 53 57 140 76 82
Ferrous metals 15 13 21 14 16
Non-ferrous metals 1.0 2 4 2 2
Glass 25 30 23 30 27
Textiles 13 10 16 11 13
Nappies and sanitary 3 3 3 2 3
Rubble 134 158 275 725 323
Timber 51 63 79 72 66
Rubber 1.0 7 11 1.0 5
Potentially hazardous 1.0 1.0 2 1.0 1.3

Figure G6.15: Primary composition of general waste to disposal face, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 7% 9% 4% 3%
Plastics 8% 6% 4% 3%
Putrescibles 15% 14% 23% 8%
Ferrous metals 4% 3% 3% 1.4%
Non-ferrous metals 0.3% 0.4% 0.6% 0.2%
Glass 7% 8% 4% 3%
Textiles 4% 3% 3% 1.1%
Nappies and sanitary 1.0% 0.8% 0.5% 0.2%
Rubble 38% 39% 44% 73%
Timber 15% 16% 13% 7%
Rubber 0.2% 2% 2% 0.1%
Potentially hazardous 0.4% 0.3% 0.3% 0.1%

The graphs show that rubble consistently made up the largest proportion of general waste in each survey. Putrescibles are the second largest in three of the four surveys, with timber the second largest in the second survey. The variation in the composition is related to the change in the classification of loads of cover material, as explained in Sections G4.4.2.2 and G6.3.3.

The average proportions of the 12 SWAP primary waste categories that make up general waste are presented in Figure G6.16. The average composition is calculated using results from the four visual surveys conducted in 2007/08 and is based on the tonnages of the different materials. These are the mean figures from Figure G6.14 expressed as percentages.

Figure G6.16: Average primary composition of general waste to disposal face, 2007/08

Primary category % of total
Paper 5%
Plastics 5%
Putrescibles 14%
Ferrous metals 3%
Non-ferrous metals 0.4%
Glass 5%
Textiles 2%
Nappies and sanitary 0.5%
Rubble 54%
Timber 11%
Rubber 0.8%
Potentially hazardous 0.2%

Rubble and putrescibles make up the largest components of the general waste stream (54 per cent and 14 per cent, respectively), reflecting the large proportion of waste generated by landscaping and earthworks and C&D activity (refer Figure G6.13). Timber comprised 11 per cent of the total, while all other materials made up less than 5 per cent each of the total.

G6.5 Overall waste, including cover material

Table G6.1 and Figure G6.17 show the tonnages of overall waste, by activity source, from the results of the four surveys. Cover material is included in the analysis.

Table G6.1: Overall waste, including cover material, 2007/08

Waste types Tonnes/week
August 2007 December 2007 March 2008 May 2008
Cover material 2409 2462 444 324
General waste 353 401 624 998
Kerbside collections 150 143 151 183
Special waste 156 295 467 241
Transfer station 226 216 146 149
Total 3293 3517 1833 1895

Figure G6.17: Overall waste, including cover material, 2007/08

Four of the five waste types that comprised the overall waste varied considerably during the survey period. Kerbside collections were the most consistent of the waste types. The quantity of cover material decreased by 86 per cent between the first and fourth surveys, probably due to the introduction of gate charges on cover material. This resulted in an increase in the amount of waste classified as general waste (see Section G6.3.3). Special waste varied considerably as a result of changes in the tonnage of sewage sludge and meat-processing-plant waste. The quantity of transfer station waste decreased substantially between the second and third surveys.

Figures G6.18 and G6.19 present the variation in the composition of the overall waste stream through the four surveys conducted in 2007/08. Figure G6.18 shows the tonnage of each of the 12 primary categories disposed of during each of the survey periods; the mean tonnage is also shown in the graph. Figure G6.19 shows the percentage composition of the overall waste stream for each of the 12 primary SWAP categories.

Figure G6.18: Tonnage of overall waste, including cover material, by primary categories, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May Mean
Paper 65 72 61 72 68
Plastics 63 53 54 69 60
Putrescibles 177 263 366 293 275
Ferrous metals 43 39 40 33 39
Non-ferrous metals 3 4 6 4 4
Glass 42 47 41 49 45
Textiles 44 35 36 37 38
Nappies and sanitary 14 14 14 15 14
Rubble 2,606 2,716 877 1,098 1824
Timber 128 135 124 121 127
Rubber 3 9 12 3 7
Potentially hazardous 106 128 200 101 134

Figure G6.19: Primary composition of overall waste, including cover material, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 2% 2% 3% 4%
Plastics 2% 2% 3% 4%
Putrescibles 5% 8% 20% 16%
Ferrous metals 1.3% 1.1% 2% 2%
Non-ferrous metals 0.1% 0.1% 0.3% 0.2%
Glass 1.3% 1.3% 2% 3%
Textiles 1.3% 1.0% 2% 2%
Nappies and sanitary 0.4% 0.4% 0.8% 0.8%
Rubble 79% 77% 48% 58%
Timber 4% 4% 7% 6%
Rubber 0.1% 0.3% 0.7% 0.2%
Potentially hazardous 3% 4% 11% 5%

These graphs show the large decrease in the quantity of rubble that coincided with the introduction of a gate charge for cover material, and the increase in putrescibles, most of which were special waste.

The average primary composition of the overall waste stream, including cover material, is presented in Figure G6.20. The average composition for the four surveys has been calculated by averaging the tonnages from each survey. These averages are shown as the mean in Figure G6.18.

Figure G6.20: Average primary composition of overall waste, including cover material, 2007/08

Primary category % of total
Paper 3%
Plastics 2%
Putrescibles 10%
Ferrous metals 1.5%
Non-ferrous metals 0.2%
Glass 2%
Textiles 1.4%
Nappies and sanitary 0.5%
Rubble 69%
Timber 5%
Rubber 0.3%
Potentially hazardous 5%

Rubble, much of it cover material, comprised an average of 69 per cent of the overall waste stream. Putrescibles was the second largest category, comprising 10 per cent of the total.

G6.6 Overall waste, excluding cover material

Table G6.2 and Figure G6.21 show the quantity of the different waste types in the overall waste from the results of the four surveys. Cover material is excluded from this analysis.

Table G6.2: Overall waste, excluding cover material, 2007/08

Waste types Tonnes/week
August 2007 December 2007 March 2008 May 2008
General waste 353 401 624 998
Kerbside collections 150 143 151 183
Special waste 156 295 467 241
Transfer station 226 216 146 149
Total 885 1055 1388 1571

Figure G6.21: Overall waste, excluding cover material, 2007/08

Three of the four waste types that comprised the overall waste stream, when cover material is excluded, varied considerably during the survey period. Kerbside collections were the most consistent of the waste types. General waste increased substantially, largely due to changes in load categorisation by the weighbridge (see Section G6.3.3). Special waste varied considerably as a result of changes in the tonnage of sewage sludge and meat-processing plant waste. The quantity of transfer station waste decreased substantially between the second and third surveys.

Figures G6.22 and G6.23 show the variation in the composition of the overall waste stream, excluding cover, through the four surveys conducted in 2007/08. Figure G6.22 shows the tonnage of each of the 12 primary categories disposed of during each of the survey periods; the mean tonnage is also shown in the graph. Figure G6.23 shows the percentage composition of the overall waste stream, excluding cover, for each of the 12 primary SWAP categories.

Figure G6.22: Tonnage of overall waste, excluding cover material, by primary categories, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May Mean
Paper 65 72 61 72 68
Plastics 63 53 54 69 60
Putrescibles 177 263 366 293 275
Ferrous metals 43 39 40 33 39
Non-ferrous metals 3 4 6 4 4
Glass 42 47 41 49 45
Textiles 44 35 36 37 38
Nappies and sanitary 14 14 14 15 14
Rubble 197 254 433 774 415
Timber 128 135 124 121 127
Rubber 3 9 12 3 7
Potentially hazardous 106 128 200 101 134

Figure G6.23: Primary composition of overall waste, excluding cover material, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 7% 7% 4% 5%
Plastics 7% 5% 4% 4%
Putrescibles 20% 25% 26% 19%
Ferrous metals 5% 4% 3% 2%
Non-ferrous metals 0.4% 0.4% 0.4% 0.3%
Glass 5% 5% 3% 3%
Textiles 5% 3% 3% 2%
Nappies and sanitary 2% 1.4% 1.0% 1.0%
Rubble 22% 24% 31% 49%
Timber 15% 13% 9% 8%
Rubber 0.3% 0.9% 0.9% 0.2%
Potentially hazardous 12% 12% 14% 6%

The variation in putrescibles and rubble is related to the changes in classifying of loads by the weighbridge between the second and third surveys. The increase in potentially hazardous material in the third survey was due to an increase in sewage sludge disposal. All of the other categories were relatively consistent, in terms of tonnage, through the survey period.

The primary composition of the overall waste stream, excluding cover material, is presented in Figure G6.24. The average composition for the four surveys has been calculated by averaging the tonnages from each survey. These averages are shown as the mean in Figure G6.22.

Figure G6.24: Average primary composition of overall waste, excluding cover material, 2007/08

Primary category % of total
Paper 6%
Plastics 5%
Putrescibles 22%
Ferrous metals 3%
Non-ferrous metals 0.3%
Glass 4%
Textiles 3%
Nappies and sanitary 1.2%
Rubble 34%
Timber 10%
Rubber 1%
Potentially hazardous 11%

Rubble, much of it from landscaping and earthworks activity, was the largest primary component of the overall waste stream, with 34 per cent of the total. Putrescible material was the second largest component with 22 per cent of the total.