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Wellington “waste catchment” trial: An investigation into a new model for waste monitoring

1 Introduction

2 Identifying the Wellington waste catchment

3 Waste facilities in Wellington region

4 Analysis of landfill data 2003–2005

5 MfE source surveys

6 Effect of pricing on landfill tonnages

7 Evaluation of the waste catchment model

Appendix 1 – Special wastes – by landfill

Appendix 2 – Letter to waste operators

7 Evaluation of the waste catchment model

7.1 Overseas use of the catchment model for waste monitoring

Internet research indicates that the concept of a “waste catchment” is widespread throughout the English-speaking world. In several American states, Oregon and West Virginia for instance, “wastesheds” are legal entities that have been established to assist local government in regulating the waste industry and managing solid waste.

Following are quotes from documents showing examples of usage of the concept:

• From New Mexico’s draft Solid Waste Management Plan 2006:⁶

“…a Solid Waste Facilities Map that identifies site locations as well as service areas, or “waste sheds.” This map connects transfer stations and public convenience centers with destination disposal sites. Boundaries would be estimated in order to evaluate population equivalents, haul distances, etc; and most importantly, highlight areas that require new facilities and/or financial assistance. This is a more functional approach than using the six NMED Solid Waste Districts, which were established for enforcement purposes, not to reflect disposal market conditions.

• From West Virginia’s Solid Waste Management Plan⁷

“The State has 55 counties and 50 Solid Waste Authorities (SWA).... The State Legislature mandated that the Solid Waste Management Board designate solid waste management sheds, or “wastesheds,” to promote cooperative efforts among SWAs. In 1993, the SWMB designated seven wastesheds in West Virginia according to the geographical proximity of counties and their local solid waste management needs.”

• Also from West Virginia⁸

“Some of the differences in the solid waste stream and management alternatives can be attributed to geographic region and population densities. As a result, for the purposes of analysis and because they already exist, all counties in the state are grouped and analyzed on the basis of wastesheds. First established in 1978, wastesheds are those areas which have common solid waste management problems and are appropriate units for planning solid waste management services.”

• From Oregon⁹

A “wasteshed” is an area with a common solid waste disposal system or an area designated by the Environmental Quality Commission as appropriate for development of a common recycling program.

• Also relating to Oregon¹⁰

“Oregon uses its CASE program to calculate their state and county recovery rates. The CASE program calculates each county's "wasteshed" recovery rate. The program then uses these county wasteshed profiles to calculate the statewide recovery rate profile.”

Although the concept of “waste sheds” (or “wastesheds”, in some instances) is widely used in America, there are few definitions provided. The most detailed definition that could be found is from an annual report of a New York waste operator, Casella:¹¹

“Within each geographic region, we organize our solid waste services around smaller areas that we refer to as “wastesheds.” A wasteshed is an area that comprises the complete cycle of activities in the solid waste services process, from collection to transfer operations and recycling to disposal in either landfills or waste-to-energy facilities, some of which may be owned and operated by third parties.”

Outside of the USA, the term “waste catchment” is more commonly used than “waste shed”. In Denmark’s Solid Waste Management Plan, “waste catchments” are delineated as areas that feed into “waste regions”, focused on incinerator sites. “Waste catchment”, as a concept, is also used in several countries in southern Africa and in Australia.

The “waste catchment” idea is recognised and defined by Christchurch City Council in its 2006 submission on the Waste Minimisation (Solids) Bill:¹²

“Authorities cooperating regionally or in “waste catchments” (i.e. natural boundaries exist that limit the flow of waste due to demographic, geographic and economic factors) for improved waste management and minimisation…….Please note the Council envisages no more than five regional groups operating in New Zealand and these groups would not necessarily reflect local government boundaries, but the natural boundaries related to the flow of waste, which may change over time and as neighbouring communities join into the various groups.”

Evidence is readily available of there being widespread recognition of the need for waste management issues to be dealt with at a scale that is not necessarily related to any other functional unit. There is, however, less evidence that waste catchments are being used by government for waste policy monitoring purposes.

In Portland, Oregon, where “waste sheds” are defined by statute, extensive monitoring and reporting are undertaken, based on the waste sheds.¹³ In Australia, in 2000, draft standard reporting protocols, using waste catchment as a reporting unit, were developed on behalf of the New South Wales Waste Boards.¹⁴

The California Integrated Waste Management Board considered using the concept as a basis for improving data for the state’s mandatory diversion rate calculations.¹⁵ While it was considered that “establishing regions according to wastesheds and measuring disposal by region” would increase accuracy, be verifiable, cost-effective, enforceable, and provide ease of use and flexibility, the idea was considered to be a low-priority and was not proceeded with.

7.2 Evaluation of the catchment model for solid waste monitoring

7.2.1 Suitability of the Wellington catchment

In Waste Not Consulting’s 2005 “Waste Composition and Construction Waste Data” report to MfE, a list of attributes were identified that would determine a catchments suitability for long-term monitoring of solid waste data. The Wellington catchment is evaluated according to these attributes in the following table.

Table 7.1 – Attributes of Wellington catchment

7.2.2 Assessment of the Wellington catchment study

The investigations into waste flows in the Wellington catchment have produced results that appear to be accurate and reliable, and that are well-suited for long-term monitoring of the relevant targets in the New Zealand Waste Strategy. The keys for achieving this accuracy and reliability have been the method for analysing and combining the weighbridge records, particularly the separate tracking of the five waste categories, and the MfE source survey.

The single most important aspect of the research has been the statistical “unpicking” of the waste streams, particularly the separation of cleanfill from the other waste streams. The lack of availability of data regarding cleanfill disposal at cleanfill sites means, and this applies to all waste data analysis, that tracking landfill data on its own is of little value. Cover material/cleanfill comprises over 30% of waste entering landfills in the Wellington catchment. Previous research indicates that at least as much again may be disposed of to cleanfill sites.¹⁶ Changes in cleanfill flows between the two disposal pathways, such as cleanfill sites opening or closing, or pricing changes, could result in changes to landfill tonnages that make monitoring targets in the NZWS impossible.

While it is recognised that the monitoring of waste to cleanfill sites will, ultimately, be an important element of national waste monitoring, until that can be achieved the best alternative is to analyse the waste streams separately. The monitoring of waste to cleanfill may, ultimately, determine the proportion of waste entering these facilities that is not, strictly speaking, cleanfill. There is no evidence as to how widespread such disposal is or on the magnitude of the non-cleanfill waste stream entering cleanfill facilities.

The MfE source survey has established that “leakage” to and from the catchment is insignificant, comprising less than 0.2% of total waste, by weight. While self-reporting by truck drivers is not necessarily an accurate measurement, and waste operators may perceive self-advantage in not disclosing the origin of out-of-area waste, there is a consistency in the results that suggests the data are largely reliable. This is shown particularly by the results from Spicer landfill, where a high percentage of general waste has been reported as arising in Wellington City.

The MfE source survey has also allowed the waste streams to be further “unpicked”, by allowing a breakdown of each waste stream by geographic source. This allows calculation of reliable per capita generation figures, which are often produced without due attention to the actual geographic source of waste. With the use of GDP/per capita data, which are available, by district, from BERL¹⁷ or Infometrics, underlying trends in waste generation and its relation to economic conditions could be established.

Overall, the methodology used for this research has proven to be relatively straightforward, could be readily transferred to other catchments, and has generated reliable information that would meet several of MfE’s long-term monitoring objectives.

7.2.3 Recommendations for long-term monitoring of the Wellington catchment

If MfE chooses to undertake further research on the Wellington catchment, it is recommended that:

• Commercial waste operators again be approached to supply data on domestic kerbside refuse collections. Baseline data on generation of this waste stream are still lacking.

• Landfill records prior to 2003 be analysed in the same manner as for this report to better establish baseline data. This would be contingent upon weighbridge records being available.

• That SWAP waste composition data from audits undertaken in recent years at Silverstream and Southern landfills be integrated into the existing database, if it is considered that this would provide useful information

• GDP per capita data be obtained for the districts in the Wellington catchment, and the relationships between economic activity and waste generation be established.

• Source surveys be undertaken at Spicer and Southern landfills to complement any further research. Further source surveys at Silverstream, Wainuiomata, and Otaihanga landfills are a lower priority, as it has been shown that a high proportion waste disposed of at those facilities is generated in the surrounding district.

• Consideration be given to excluding Otaihanga landfill from the catchment. The MfE source surveys found very little waste “leaking” either into or from the catchment, and the data produced from the site are of markedly lower quality than the other facilities. The Otaihanga landfill is the only one of the facilities that is likely to close in the near future, and its exclusion at the earliest opportunity would mean the data for the catchment do not have to be re-analysed at a later time.

• Waste transport to Bonny Glen landfill by Waste Management NZ Ltd be monitored.

• Long-term, cleanfill sites will need to be included in the catchment study to achieve all of MfE’s monitoring objectives. Discussions with the operators will need to be entered into as soon as possible, as their cooperation is not apt to be immediately forthcoming.

7.2.4 Comparison with “Measuring up 2005”

The effectiveness of the methods used in this research in gaining a meaningful understanding of waste flows can be seen by comparing the results of the current research to those of “Measuring up 2005”, the Greater Wellington Regional Council’s State of the Environment report. With regards to waste disposal, the report concludes:¹⁸

“The volume of solid waste arriving at landfills has been dropping, mostly because a lot of green waste is now kept back for composting. If we can divert more glass, plastic and paper away from the tip and into recycling bins, solid waste volumes should come down even further.”

The background report for “Measuring up 2005”, from which this conclusion has been taken, includes the following:¹⁹

“There are two privately operated landfills in the region……Most waste accepted at these private landfills is cleanfill but Greater Wellington has no annual volume data from them. All references to landfills in this report are to the municipal landfills”

The traditional analysis of landfill tonnages in “Measuring up 2005” has resulted in what could be a markedly different conclusion to that which would have resulted if the cleanfill waste had been analysed separately. While waste to the municipal landfills may have declined over the period analysed, this information says little about waste generation or disposal in the region. The size of the cleanfill waste stream, and the presence of alternative disposal pathways which have not been measured, makes the analysis of limited value.

Further analysis of the background document supporting “Measuring Up 2005” demonstrates the usefulness of the MfE source survey in generating accurate data. The document contains figures on per capita waste generation, but these figures are based on every landfill serving only the residents of the city in which it is situated. As a result, the per capita figures for Wellington and Porirua are markedly different than those calculated in this report, due to the significant trans-boundary movement of waste into Spicer landfill in Porirua.

7.3 Assessment of the catchment model for national monitoring

This project has established that researching waste data at the catchment level results in all of the advantages posited in Section 1.2.4. There are no indications that the long-term study of several waste catchments throughout New Zealand would not be a cost-effective, accurate means of monitoring the relevant targets in the New Zealand Waste Strategy.

The most important information generated by this research is the per capita waste generation figures for the catchment. While these per capita waste generation figures could be extrapolated to a larger scale, the comparison of these figures to GDP/per capita data for each district would provide important information. The “uncoupling” of waste generation and economic activity is seen as a primary objective of the Government’s waste minimisation policy, and this should be monitored if possible.

Identifying waste catchments for long-term monitoring would be relatively straightforward. Discussions with local council officers and landfill operators would quickly establish whether the requisite degree of cooperation would be forthcoming and whether the catchment is sufficiently “self-contained” in terms of waste generation and disposal.

Initial work in the selected indicator catchments would involve analysis of all available historic weighbridge records to establish baseline historic data. Source surveys may be needed initially, to establish the degree of “leakage” into and out of the catchment. These would not need to be repeated on a frequent basis.

The basic element of the monitoring, the analysis of weighbridge records to separate the various waste streams, has proven to be extremely resource-efficient. While the initial analysis may involve consultation with the weighbridge operators, subsequent analyses of annual records could be completed within a matter of hours.

On its own, this basic monitoring of weighbridge records in several self-contained catchments would provide more accurate information on waste disposal than is currently available. The resourcing required for this level of monitoring would be minimal.

Beyond the minimal resourcing required for the weighbridge record monitoring, MfE would have a high degree of flexibility with its monitoring programme and its resource requirements. Once a catchment monitoring programme has been established, MfE would have the option of conducting in-depth investigations into particular components of the waste stream that are of interest.

The weighbridge record analysis used for this study has been so effective and efficient that consideration should be given to attempting to do it on a national level. A five-yearly analysis of all available weighbridge records would provide a very accurate “snapshot” of waste disposal in New Zealand, and would provide a means of calibrating the data gathered through catchment monitoring.

7.3.1.1 Other possible catchments

Should MfE choose to investigate further the establishment of a national waste monitoring programme based on waste catchments, the following catchments should be considered:

1. Canterbury – The area within Canterbury Regional Council’s boundaries is currently served by four landfills. For many years, Christchurch City Council has generated high-quality waste data, and, recently, Environment Canterbury has produced a report on waste flows within the region that contains many elements of the research presented in this report.²⁰ Although none of the research available publicly addresses the issue of “leakage” of waste in or out of the study area, it is likely, given the geography of the region, that well-defined waste catchments do exist.

2. Queenstown – The council-owned Victoria Flats landfill accepts waste from Queenstown and transfer stations at Wanaka, Cromwell, and Alexandra. SWAP audits of the landfill have been undertaken twice by Waste Not Consulting, and the District Council is currently very active in waste minimisation. The landfill produces good quality weighbridge records. Given the geography and population density of the region, it is likely that very little waste generated in the areas served by the landfill is disposed of elsewhere.

3. Southland – The AB Lime landfill, near Winton, is the new regional landfill for the Southland region, serving Invercargill and Gore. The level of cooperation that might be forthcoming from the local authorities or the landfill operators is not known, but the landfill is likely the disposal facility for a self-contained waste catchment.

4. Rotorua – The council-owned Rotorua District Landfill serves Rotorua City and four small local transfer stations. It is unlikely that any waste “leaks” in or out of the catchment. Waste Not Consulting has undertaken SWAP audits for the District Council in 2003 and 2005. The landfill produces good quality weighbridge records.

5. Rodney District – Although Rodney District is not a “waste catchment” in the same way as the other catchments, research undertaken by Waste Not Consulting for the district council has produced very satisfactory results. Redvale, the largest landfill in the country, is in the district, and so attracts virtually all of the waste generated in the district. Redvale keeps excellent records, including the geographic source of waste loads, and is very cooperative in sharing data with local government. The recent research by Waste Not involved collecting data from all waste operators in the District, and matching this to the landfill records for the same period. The correlation was nearly perfect, suggesting the data are very accurate.

6. Auckland to Hamilton – The Auckland-Hamilton corridor contains about 1.3 million residents. The area is served by Redvale landfill, north of Auckland, Whitford landfill, east of Auckland, Hampton Downs landfill, south of Auckland, and Horotiu landfill, north of Hamilton. There are approximately 15–20 transfer stations in the area that dispose of refuse at the landfills.

Other than waste from Whangarei that is transported to Redvale, it is understood that no other waste from out of the catchment is disposed of at the landfills. However, the boundaries of the catchment to the south and east of Hamilton are not well-defined.

Waste Not Consulting has undertaken SWAP surveys at Redvale, Whitford, and Horotiu. All maintain excellent weighbridge records, and it would be expected that Hampton Downs does as well.

Due to the large number of transfer stations in the Auckland–Hamilton waste catchment, it would not be well-suited to any in-depth investigations into the waste stream. However, long-term regular analysis of the weighbridge records from the four landfills would provide valuable information on the waste disposal of nearly a third of New Zealanders.

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