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M6 Summary of Results 2007/08

In this summary of the results from the four surveys undertaken at Matamata Transfer Station as part of the SWAP Baseline 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

  • tonnages of the four activity sources and the general waste stream

  • compositions of the general waste stream

  • tonnages of the waste streams that make up the overall residual waste stream

  • compositions of the overall residual waste stream.

Average compositions are provided for the four activity sources that make up the general waste stream, the general waste stream, and the overall residual waste stream.

M6.1 Activity sources

M6.1.1 Construction and demolition waste

The primary composition of C&D waste from the four surveys is shown in Figure M6.1.

Figure M6.1: Composition of C&D waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 5% 4% 5% 3%
Plastics 6% 5% 6% 5%
Putrescibles 0.6% 3% 0.8% 2%
Ferrous metals 8% 10% 13% 4%
Non-ferrous metals 0.6% 0.6% 0.6% 0.2%
Glass 2% 3% 0.0% 2%
Textiles 2% 5% 4% 2%
Nappies and sanitary 0.0% 0.0% 0.1% 0.0%
Rubble 28% 39% 53% 59%
Timber 46% 29% 18% 23%
Rubber 0.5% 0.3% 0.0% 0.4%
Potentially hazardous 1.0% 0.3% 0.7% 0.3%

In each of the four surveys, rubble and timber were the largest components of C&D waste, and ferrous metals was the third largest component. 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 the relative proportions of rubble and timber, their combination comprised nearly three-quarters of C&D waste in every survey.

M6.1.2 Industrial/commercial/institutional waste

The primary composition of ICI waste from the four surveys is shown in Figure M6.2.

Figure M6.2: Composition of ICI waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 17% 15% 11% 19%
Plastics 15% 34% 10% 27%
Putrescibles 13% 6% 3% 31%
Ferrous metals 11% 4% 8% 3%
Non-ferrous metals 2% 0.9% 0.7% 1.0%
Glass 9% 7% 12% 5%
Textiles 6% 3% 7% 0.8%
Nappies and sanitary 1.3% 0.9% 0.8% 0.2%
Rubble 7% 3% 12% 6%
Timber 17% 25% 34% 7%
Rubber 0.6% 0.5% 0.9% 0.1%
Potentially hazardous 2% 0.3% 0.9% 0.3%

ICI waste was relatively heterogeneous, with no single material comprising over 35 per cent of the total in any of the surveys. In each survey a different waste category comprised the largest proportion: the paper category was largest in the first survey, plastics in the second, timber made up nearly 35 per cent in the third survey, and putrescibles was the largest proportion of ICI waste in the May 2008 survey.

For some categories there is little consistency between surveys in terms of the proportion of the materials present. The proportion of plastics, for example, varies from 9 to 34 per cent (over half the plastic in the survey in which plastic comprised 34 per cent of the total was contained in a single load of waste from an explosives manufacturer). This variability reflects both the nature of this activity source and the small scale of the general waste stream; therefore a single load of a particular material (such as chicken feed in the fourth survey or plastics from an explosives manufacture) can have a substantial effect on the composition measured during the survey period.

M6.1.3 Landscaping and earthworks waste

The primary composition of landscaping and earthworks waste from the four surveys is shown in Figure M6.3.

Figure M6.3: Composition of landscaping and earthworks waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 0.9% 3% 6% 0.5%
Plastics 0.9% 3% 4% 0.4%
Putrescibles 78% 21% 64% 85%
Ferrous metals 0.0% 0.3% 6% 0.1%
Non-ferrous metals 0.0% 0.0% 0.5% 0.0%
Glass 0.1% 3% 1.3% 0.2%
Textiles 0.0% 0.3% 3% 0.1%
Nappies and sanitary 0.1% 0.6% 0.5% 0.3%
Rubble 8% 68% 3% 0.7%
Timber 13% 1.3% 10% 13%
Rubber 0.0% 0.0% 0.5% 0.0%
Potentially hazardous 0.0% 0.0% 0.5% 0.0%

Results from the four surveys show that the composition of the landscaping and earthworks activity source is generally made up of three primary waste categories: putrescibles, rubble and timber. In three of the four audits green waste represented over 60 per cent of the total weight, but in the second survey nearly 70 per cent was rubble. The majority of this rubble material came from only two trailer loads, which disposed of large quantities of soil. This indicates the effect just a few loads can have on changing the composition of this activity source, especially given that during the course of each survey only between 1 and 8 per cent of the total number of loads received at the transfer station were classified as originating from a landscaping and earthworks activity source.

M6.1.4 Residential waste

The primary composition of residential waste from the four surveys is shown in Figure M6.4.

Figure M6.4: Composition of residential waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 10% 9% 10% 9%
Plastics 10% 14% 12% 10%
Putrescibles 12% 10% 11% 19%
Ferrous metals 13% 14% 13% 14%
Non-ferrous metals 1.1% 0.8% 1.0% 0.7%
Glass 5% 4% 5% 4%
Textiles 6% 8% 12% 11%
Nappies and sanitary 1.3% 3% 3% 3%
Rubble 15% 6% 6% 11%
Timber 25% 30% 24% 18%
Rubber 0.4% 0.9% 3% 0.9%
Potentially hazardous 1.2% 1.0% 2% 0.8%

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 three of the surveys timber was the largest classification. In the fourth survey putrescibles was the largest classification, but comprised less than 20 per cent of the total. Although there is some variability in the proportions of the 12 primary waste categories between the surveys, some general consistencies are apparent, especially for categories such as paper, plastics and metals.

M6.2 General waste

General waste discharged at the Matamata Transfer Station is defined as waste being generated from four different activity sources: C&D, ICI, landscaping and earthworks, and residential (as illustrated in Figure M1.1). Figure M6.5 presents the tonnage of waste from each activity source for each of the four surveys.

Figure M6.5: Tonnage of activity sources of general waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Construction and Demolition 18 30 15 20
Industrial/Commercial/ Institutional 8 5 10 12
Landscaping and Earthworks 3 0.9 0.4 1.0
Residential 14 10 13 8
Total General Waste 43 45 38 41

Figure M6.5 shows that in each of the four surveys the total quantity of general waste disposed of was similar, and was composed of roughly consistent proportions of waste from these four activity sources. Waste generated from C&D activity was consistently the largest component of the total general waste stream (approximately 50 per cent). The tonnage of C&D waste was significantly higher in the November survey, which may be due to seasonal trends in the construction industry or may be related to the influence of waste from a single large construction project on the small sample size. Waste from landscaping and earthworks activities were consistently the lowest (approximately 3 per cent) across all four surveys, and showed little seasonal variation. ICI waste and residential waste made up approximately 25 per cent of the total general waste stream in all four audits. The decrease in residential waste through the surveys may have been due to seasonal factors, but also could have been related to general economic conditions and householders being reluctant to pay disposal charges in a tightening economy.

Figures M6.6 and M6.7 show the variation in the composition of the general waste stream through the four surveys conducted in 2007/08. Figure M6.6 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 M6.7 shows the percentage of the general waste stream for each of the 12 primary SWAP categories.

Figure M6.6: Tonnage of general waste, by primary categories, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May Mean
Paper 4 3 3 4 3
Plastics 4 4 3 5 4
Putrescibles 5 3 2 6 4
Ferrous metals 4 5 4 2 4
Non-ferrous metals 0.4 0.3 0.3 0.2 0.3
Glass 2 2 2 1.2 2
Textiles 2 2 3 2 2
Nappies and sanitary 0.3 0.3 0.5 0.3 0.4
Rubble 8 13 10 13 11
Timber 13 13 9 7 11
Rubber 0.2 0.2 0.5 0.2 0.3
Potentially hazardous 0.5 0.2 0.4 0.2 0.3

Figure M6.7: Primary composition of general waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 9% 6% 8% 9%
Plastics 9% 10% 9% 12%
Putrescibles 11% 6% 5% 16%
Ferrous metals 10% 10% 11% 5%
Non-ferrous metals 0.9% 0.7% 0.7% 0.5%
Glass 4% 4% 5% 3%
Textiles 4% 5% 7% 4%
Nappies and sanitary 0.7% 0.7% 1.2% 0.6%
Rubble 19% 29% 25% 33%
Timber 31% 28% 25% 17%
Rubber 0.5% 0.4% 1.2% 0.4%
Potentially hazardous 1.2% 0.4% 1.1% 0.4%

The graphs show that while timber and rubble consistently make up the largest proportion of general waste in each survey, they each have a relatively high variation between surveys. Much of this variation is related to changes in the composition of C&D waste. The next largest component of the waste stream, plastics, varies less than does putrescibles, the fourth largest category.

In the first audit, conducted in August 2007, the drop-off facility for green waste was not accessible due to surface flooding. Figure M6.6 shows the effect this had on the increased quantity of putrescibles (green waste in particular) measured compared to subsequent audits. The May 2008 survey results were an exception, with the highest quantity of putrescible waste out of the four audits. This high May 2008 result was not caused by large amounts of green waste but by the disposal of a single load of ICI waste comprising about 3 tonnes of putrescible chicken feed.

The average proportions of the 12 SWAP primary waste categories that make up general waste are presented in Figure M6.8. 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 M6.6 expressed as percentages.

Figure M6.8: Average primary composition of general waste, 2007/08

Primary category % of total
Paper 8%
Plastics 10%
Putrescibles 10%
Ferrous metals 9%
Non-ferrous metals 0.7%
Glass 4%
Textiles 5%
Nappies and sanitary 0.8%
Rubble 26%
Timber 25%
Rubber 0.7%
Potentially hazardous 0.8%

Rubble and timber make up the largest components of the general waste stream (26 per cent and 25 per cent, respectively), reflecting the large proportion of waste generated from C&D activities (see Figure M6.5). Plastics, putrescibles, ferrous metals and the paper categories each make up between 8 and 10 per cent of the general waste composition.

M6.3 Overall residual waste

Table M6.1 and Figure M6.9 present the quantity of overall residual waste from the results of the four surveys.

Table M6.1: Overall residual waste, 2007/08

Waste types Tonnes/week
August 2007 November 2007 February 2008 May
2008
General waste 42.5 45.1 38.4 41.2
Kerbside collections 45.5 51.3 60.2 59.1
Total 88.0 96.3 98.6 100.3

Figure M6.9: Overall residual waste, 2007/08

The results show that the overall residual waste was made up of relatively consistent proportions of general waste and kerbside collections. The major change was the tonnage of kerbside collections increasing between the second and third audits, likely as the result of a private waste operator discharging at the Matamata Transfer Station rather than at another disposal facility. This increased the proportion of kerbside collections from roughly 50 per cent to 60 per cent of the total.

Figures M6.10 and M6.11 show the variation in the composition of the overall residual waste stream through the four surveys conducted in 2007/08. Figure M6.10 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 M6.11 shows the percentage composition of the overall residual waste stream for each of the 12 primary SWAP categories.

Figure M6.10: Tonnage of overall residual waste, by primary categories, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May Mean
Paper 12 12 14 14 13
Plastics 11 12 12 14 12
Putrescibles 21 21 24 28 23
Ferrous metals 7 7 8 5 7
Non-ferrous metals 0.7 0.7 0.8 0.7 0.7
Glass 5 5 6 5 5
Textiles 4 5 6 5 5
Nappies and sanitary 5 6 7 7 6
Rubble 8 14 10 14 12
Timber 14 13 10 8 11
Rubber 0.3 0.3 0.6 0.3 0.4
Potentially hazardous 0.8 0.6 0.9 0.6 0.7

Figure M6.11: Primary composition of overall residual waste, 2007/08

Primary category 6-12 August 20-26 November 12-18 February 5-11 May
Paper 13% 12% 14% 14%
Plastics 12% 12% 13% 14%
Putrescibles 24% 22% 24% 28%
Ferrous metals 7% 8% 8% 5%
Non-ferrous metals 0.8% 0.7% 0.8% 0.7%
Glass 5% 5% 6% 5%
Textiles 5% 5% 6% 5%
Nappies and sanitary 6% 6% 7% 7%
Rubble 10% 14% 11% 14%
Timber 16% 14% 10% 8%
Rubber 0.3% 0.3% 0.6% 0.3%
Potentially hazardous 1.0% 0.6% 0.9% 0.6%

These graphs indicate that, of the five largest categories, putrescibles, timber and rubble vary substantially across the four surveys, while paper and plastics vary to a lesser degree.

The average primary composition of the overall residual waste stream is presented in Figure M6.12. 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 M6.10.

Figure M6.12: Average primary composition of overall residual waste, 2007/08

Primary category % of total
Paper 13%
Plastics 13%
Putrescibles 24%
Ferrous metals 7%
Non-ferrous metals 0.8%
Glass 5%
Textiles 5%
Nappies and sanitary 7%
Rubble 12%
Timber 12%
Rubber 0.4%
Potentially hazardous 0.8%

The putrescible waste category is the largest component of the overall residual waste stream (24 per cent), followed by paper, plastics, timber and rubble (each between 12 and 13 per cent).