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1 Introduction

The New Zealand Waste Strategy (NZWS) was launched by the New Zealand Government in March 2002. The document established new strategies for minimising waste as well as means for improving waste recovery and management. At the strategic level, the document contains both core principles and a vision for the future; at the practical level, thirty national targets for priority waste areas are set. The Strategy states, with regards to the national targets: “Setting targets requires good information to ensure they are realistic and to measure progress. Current information is poor, and we have no consistent, reliable information about waste flows.”

The national targets set were reviewed by Ministry for the Environment (MfE) in 2004, with the review finding that “an effective and cost-efficient monitoring and reporting system is essential for measuring progress in implementing the NZWS and achieving the targets”.

As well as measuring progress towards the national targets, a reliable waste monitoring and reporting system would provide useful information to assist local authorities and the waste industry with waste minimisation and waste management planning. It would also assist central government with its reporting obligations, including those to the Organisation for Economic Cooperation and Development, the Basel Convention, the Stockholm Convention, the Kyoto Protocol, and the New Zealand Packaging Accord.

In November 2005, MfE commissioned Waste Not Consulting to undertake research as part of the process of developing a framework for ongoing waste monitoring and reporting at the national level. The project was established with two objectives:

  1. The compilation and analysis of all relevant existing data on waste composition and the quantity of waste being disposed of to landfills and cleanfills.

  2. Development of recommendations for an ongoing monitoring programme for waste to landfill, cleanfill, and construction and demolition (C&D) waste landfill.

The resulting recommendations1 included many that were based on the concept of monitoring “indicator waste catchments”. The concept of a waste “catchment” is based on the hydrological model of a “watershed”. A waste “catchment” is a geographical area within which all of the waste that is generated is also disposed of, and within which little or no waste from outside the area is disposed of. The concept of “indicator waste catchments” was developed in response to the inherent inaccuracies in monitoring waste at either the national level or the individual facility level.

In response to these recommendations, MfE has commissioned Waste Not Consulting to further the development of the “catchment” model with the research contained in this report. The primary objectives of the research are to:

  • test whether “waste catchments” can be used to measure the flow of waste within geographic areas and across geographic boundaries

  • assess the feasibility of using the “waste catchment” concept to monitor waste composition nationally

  • determine the appropriateness of the Wellington region as an indicator catchment.

Subsequent to the initiation of the research, a secondary objective of determining the effect of pricing on waste flows was included in the project.

The principle means for accomplishing the objectives would be to collate and analyse the weighbridge information for the past three years from the following landfills:

  • Northern landfill (owned by Wellington City Council)

  • Otaihanga landfill (owned by Kapiti Coast District Council)

  • Silverstream landfill (owned by Hutt City Council)

  • Southern landfill (owned by Wellington City Council)

  • Spicer landfill (owned by Porirua City Council)

  • Wainuiomata landfill (owned by Hutt City Council)

The weighbridge data would, if possible, be split into the following categories:

  • Domestic kerbside – council and commercial collections

  • General – if possible this would be split into domestic and commercial waste

  • Special wastes.

From the data, any changes in quantities of each of the above categories and associated patterns, such as changes in flow from one facility to another or “leakage” to a facility outside the catchment, would be identified.

In addition, MfE would coordinate a source survey with the local government landfill operators. The source survey would be carried out at eight landfills and transfer stations in the catchment and surrounding districts. The data from these surveys would provide information on the geographic source of waste and whether the waste was of domestic or commercial origin. This information would contribute to the dataset used to determine the validity of the Wellington region as a suitable indicator waste catchment.

The report is structured as follows:

  • Section 1.1, adapted from Waste Not Consulting’s 2005 “Waste Composition and Construction Waste Data” report to MfE, provides a context for the current research by outlining the development of waste data collection in New Zealand.

  • Section 1.2 introduces the concept of the waste “catchment” model, and examines the pros and cons of monitoring waste at different levels

  • Section 2 outlines the geography of the Wellington waste catchment

  • Section 3 describes the waste disposal facilities in the catchment

  • Section 4 analyses data from the six landfills in the Wellington catchment for the period 2003–2005

  • Section 5 analyses data collected by the MfE source surveys at four landfills

  • Section 6 examines the effect of pricing on waste flows, using data provided for the primary research by the landfills in the catchment and the results of the MfE source surveys

  • Section 7 assesses the results of the research and relates the results to the feasibility of using the waste catchment model for long-term waste monitoring in New Zealand.

1.2 New Zealand waste data

The development of waste data collection in New Zealand has run parallel to the development of waste management strategies and technologies. In the period prior to the 1970s, when landfills were unregulated and the objective of waste management was to protect public health, there were virtually no data gathered on waste, and none was likely to have been compiled at the national level.

With the introduction of sanitary landfills and improved waste management processes, central government set about compiling the information necessary to better understand refuse disposal in New Zealand. One of the earliest investigations was the 1971 national survey of refuse tips. This was followed by similar surveys of landfills in 1995, 1998, and 2002. These surveys were primarily aimed at assessing the technologies of the landfills to better understand the environmental effects of waste disposal. As refuse tips became more controlled, and weighbridges became more common, tonnage figures were gathered and aggregated, giving the first estimates of the quantity of waste being landfilled in New Zealand.

The most recent estimates of the tonnage of refuse landfilled in New Zealand are based on the MfE 2002 landfill audit and survey. While the estimates made for that report are more accurate than those made previously, a significant proportion of landfills were still relying on volume-based information for their data. This situation is improving as small, substandard landfills are closed, the remaining landfills become larger and more centralised, and weighbridges become standard operational equipment.

The gathering of qualitative and quantitative waste data by local authorities is improving, driven by statutory obligations under the Local Government Act 1996 and the targets for reporting set by Central Government’s 2002 New Zealand Waste Strategy. There is, however, at present no coordinated national strategy for compiling and analysing waste composition data that are collected by local authorities.

The current state of knowledge about disposal of waste materials to cleanfills in New Zealand is comparable to that about landfills in the 1960s. There is no national census of cleanfills and few estimates of tonnages have been made, even at a local level. For the most part, local authorities cannot identify all cleanfill sites within their jurisdiction as most councils do not require resource consents for cleanfills. There is virtually no information publicly available on the composition of waste material being disposed of to cleanfill.

The composition of waste was investigated on a sporadic basis by various local authorities in the 1980s using a variety of methodologies. The results were not necessarily comparable. This situation was greatly improved by the introduction in 1992 of the MfE’s Waste Analysis Protocol (WAP), a standardised methodology for measuring waste composition using a standardised classification system.

The WAP was most effectively put to use in a nationwide waste composition survey undertaken with MfE funding in the early 1990s. The results of these surveys were combined with the 1995 landfill census to produce the solid waste information presented in MfE’s 1997 National Waste Data Report.

The use of the WAP for waste composition surveys by local authorities subsequent to this time was not widespread, with the 1997 Auckland region waste survey being the significant exception. For the most part, councils had no pressing need for the data, and the procedure was relatively expensive, given the precision and accuracy of the results produced. The absence of experienced waste surveyors, particularly in provincial areas, was another disincentive to studying waste composition.

In 2002, MfE updated the WAP, which became the Solid Waste Analysis Protocol (SWAP). In the same year, MfE instituted the SWAP Baseline Programme to provide solid waste composition information from four indicator sites around New Zealand. The objective of the Baseline Programme was to establish generic waste composition data for a range of sites that could be used as the basis for indicative waste composition data by any local authority.

The results of the Baseline Programme surveys, and a range of other surveys of various waste streams, are available on the MfE website. The results of the Baseline Programme are presented in the form of waste composition data on spreadsheets which can be manipulated by the user to calculate waste stream composition based on a number of variables. After the two-year Baseline Programme concluded in 2004, MfE undertook the assessment of its waste monitoring programmes that has resulted in the current research.

1.3 Rationale for the “catchment model” for waste data monitoring

This section, adapted from Waste Not Consulting’s 2005 “Waste Composition and Construction Waste Data” report to MfE, examines the pros and cons of the different possible scales at which waste monitoring can take place. This information is provided as an introduction to monitoring “waste catchments” and contains the basis for the recommendations that have resulted in MfE’s further investigations into the concept.

One of the most important aspects of designing an ongoing waste monitoring programme is resolving the issue of scale. In New Zealand, waste data have historically been gathered on several levels, ranging from specific waste streams entering individual disposal facilities to national landfill tonnages. A comprehensive national monitoring programme, such as that needed to fulfil the monitoring requirement of MfE, requires data gathering at several levels. The uses, advantages, and disadvantages of waste data gathering at different levels are discussed in the following sections.

1.3.1 National level data

Currently, MfE endeavours to identify and monitor national trends in waste disposal by using estimates of national tonnages, based on landfill surveys, and on waste composition, based on SWAP surveys.

Landfill surveys have been completed by MfE in 1995, 1998, and 2002. The primary purpose of these surveys has been to identify trends in specific aspects of the design and operation of all landfills operating throughout the country. The surveys also gathered information on quantities of waste to landfill. As a high proportion of waste entering landfills is now weighed, the surveys provide a reliable, cost-efficient means of tracking landfill tonnages.

To ensure the accuracy of the landfill tonnage data, a consistent protocol must be used with regards to the inclusion or exclusion of cover material. Landfills account for cover material in different ways, and these differences can substantially alter the relevance of the data gathered. No such protocol was used in the landfill survey undertaken in 2002.2

The SWAP Baseline Programme was initiated to provide national waste composition data by repeated surveying at individual disposal facilities. The Programme involved quarterly waste surveys at four disposal facilities over a two-year period. An estimate of national waste composition was generated by averaging the results from the four facilities.

The “snapshots” produced by the SWAP Baseline Programme can be aggregated to produce a reasonably accurate composition of waste in New Zealand. Developing national composition data using such a programme requires considerable resources and a high degree of central coordination to maximise the accuracy. The snapshots, however, taken out of context, are limited in their ability to monitor trends over time by the limitations inherent in surveying individual disposal facilities, as outlined in Section 1.2.3.

The usefulness of the SWAP Baseline Programme data for estimating national waste composition has been limited to being a series of “snapshots in time” by:

  • the reliability of some of the survey methodologies, which were contracted to four different contractors

  • the inconsistent use by the contractors of secondary categories that could have enabled the quantification of particular waste streams relevant to NZWS targets, such as green waste, or C&D materials

  • inconsistent classification by the contractors of waste sources, such as “general wastes”, “domestic collections”, and “special waste loads”

  • lack of reported information from the contractors about the source of waste to landfill.

1.3.2 Regional level data

Surveying of waste disposal within local government boundaries has been undertaken by a limited number of local authorities. Some of the known regional studies are:

  • The Auckland Regional Waste Stream Report 1995 involved WAP surveys at all major disposal facilities in the Auckland region. The study was undertaken jointly by the regional and local councils with funding assistance from the Sustainable Management Fund.

  • Rodney District Council has twice contracted Waste Not Consulting (in 2001 and 2005) to undertake SWAP surveys and gather data to estimate the quantity and composition of solid waste to landfill generated within the district.

  • Christchurch City Council conducted rotating SWAP surveys at all waste disposal facilities within its boundaries in 2003–2004.

The principal problem with regional surveys as a long-term monitoring tool is the trans-boundary movement of waste. Over time, waste from outside a region may “migrate” into local disposal facilities, or waste generated within the region may be disposed of outside of the region.

Such trans-boundary movement of waste has, for example, significantly changed waste flows within the Auckland region in recent years. Thames Coromandel District and Whangarei waste streams have been transported into the region, and recently the opening of a new landfill in Waikato has seen significant quantities of waste being transported out of the Auckland region into the Waikato facility. Without constant monitoring of such changes, time series of data taken from an individual city, district, or region are of limited usefulness, particularly for monitoring the effects of government policy on waste minimisation.

Gaining the cooperation of all private waste operators in providing tonnages and the geographical source of waste is an issue in regional level surveys. While many operators willingly give their full cooperation, some are reluctant to disclose what they consider “commercially sensitive” information, such as tonnages, that may be perceived as being of value to their competitors.

1.3.3 Facility level data

The surveying of individual waste disposal facilities is the most common level of surveying undertaken in New Zealand and was the basis for the SWAP Baseline Programme. The major disadvantage of monitoring individual facilities is the need for contextualisation of the data to understand the wider system within which the facility operates. Without knowing detailed information about the waste flows entering a facility, and how they change over time, little information can be gained regarding the effectiveness of government policy in reducing waste over time.

The waste that enters an individual facility is generally only a subset of the waste generated within the surrounding community. Waste collection and disposal, in both the commercial and council sectors, are based on limited-term contracts, and a change in contractor may result in waste flows being diverted from one facility to another. These commercially-driven changes in waste flows complicate the interpretation of facility level waste data.

Significant changes in waste flows can also occur when a new disposal facility is opened in the same community. This occurred recently in west Auckland, where an existing transfer station experienced a significant decrease in waste volume. The transfer station had undertaken SWAP surveys annually for a seven-year period, and the time-series of data that had been built up was compromised by the significant change in waste flows that occurred when the new facility opened.

1.3.4 “Catchment” level data

The concept of a waste “catchment” is based on the hydrological model of a “watershed”. While not used frequently in New Zealand, the idea of a “wasteshed” is used in many areas of the USA and is defined in Oregon law as being “an area of the state that shares a common solid waste disposal system, or an appropriate area in which to develop a common recycling system”3.

Waste flows are subject to forces analogous to those which define watersheds. In the same way that surface water flows downwards towards a common outlet to the ocean, so does waste tend to flow towards common “sinks”, which may be transfer stations or landfills. These flows tend to be defined by economics, with waste generally being transported to the most economic disposal facility, which is generally the closest facility. “Closest” may be determined in terms of either geographical distance or, in a major metropolitan centre, travel time. In areas with competing disposal facilities in relatively close geographical proximity, differences in gate charges can over-ride transport costs, resulting in waste being transported to the less expensive facility.

Waste catchments will vary greatly in scale. A small rural catchment may involve no more than a single landfill. In a larger catchment, several transfer stations may feed into a single landfill. In large metropolitan areas with more than one landfill, waste flows are influenced by ownership of each landfill, but, as a whole, the multiple landfills may still comprise a distinct catchment area.

In New Zealand, waste catchments may be defined by geographical features to a greater extent than in other countries. Landfills are generally situated for their proximity to population centres, and in New Zealand these are often separated by topographical features, such as major ranges of hills, which would serve to discourage waste transport.

While watersheds can be accurately delineated, waste catchments are likely to be somewhat “fuzzy” around the boundaries, with border areas from which waste is regularly transported in different directions. As long as the “fuzzy” areas are of a relatively small size, this lack of definition will not significantly affect the overall results.

The principal advantages to monitoring at the catchment level are seen as being:

  1. The ability to consistently capture data on all waste disposal within the catchment area, and not have the data subject to the changes in waste flows which reduce the reliability of facility-level study. These data can be extrapolated up to the national level, and monitored in a consistent manner to establish trends.
  2. The opportunity to monitor on a scale which can be adequately resourced over the long-term. While New Zealand as a whole represents a single waste catchment, it would require substantial resources to gather the necessary detailed waste data from throughout the country.
  3. The option of conducting in-depth investigations into particular elements of the waste stream that are of interest. By understanding the full picture of waste disposal within a catchment, surveys of specific materials within specific waste streams can be extrapolated more accurately. More precise data from SWAP surveys on specific waste materials is also possible by focussing the surveying on specific waste streams. For example, a material such as plastic pallet wrap could usefully be investigated by conducting a SWAP survey that includes solely commercial waste and uses specific secondary categories. The results of such a survey would be more precise than a more general SWAP survey and could be accurately extrapolated up to the overall waste stream by using the detailed information on waste sources that would be available.
  4. An ability to contextualise the information by working long-term with a small number of council officers and facility operators.

1.3.4.1 Identification of “indicator waste catchments”

The 2005 Waste Not Consulting report recommended that MfE identify several “indicator catchments” that would serve as the basis for a significant portion of an ongoing waste monitoring programme in the same way that the biological sciences use indicator organisms to assess the health of ecosystems. It was suggested that it could be cost-effective and produce reliable results if MfE was to concentrate its resources on a limited number of indicator waste catchments.

The SWAP Baseline Programme was based on “indicator” facilities, with the results of the SWAP surveys being made publicly available on the basis that they were considered representative of other facilities. The establishment of indicator catchments is a development of this concept to a more holistic level that takes into account the limitations of the facility level research.

Appropriately-selected indicator waste catchments could be treated as a microcosm of the country as a whole and be studied in-depth over time. Problematic issues, such as the quantification of cleanfill disposal, can be addressed and studied more readily at the catchment level and those results extrapolated to a national level. Specific waste streams, such as packaging in commercial waste, can be investigated with purpose-designed SWAP surveys, the results of which can be integrated with other existing data on the catchments.

Indicator waste catchments would ideally have the following attributes:

  • identifiable waste flows that are contained within a discrete area

  • little “leakage” into or from surrounding catchments (i.e. movement of waste in or out of the catchment)

  • cooperative local authorities within the catchment with a commitment to long-term waste monitoring

  • cooperative disposal facility operators

  • adequate record-keeping by the disposal facility operators

  • compatible systems of record keeping

  • a functional scale i.e. the number of disposal facilities being suitable for the resourcing available for monitoring.

1 Waste Not Consulting (2005) Waste Composition and Construction Waste Data, prepared for Ministry for the Environment, Wellington

2 Jennie Franke, MfE, 2006, personal communication

3 www.deq.state.or.us/wmc/solwaste/countycontact.html

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