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How is waste composition measured?

Waste composition data in New Zealand comes from visual or sort-and-weigh surveys. Such surveys provide a snapshot of waste composition at that time.

The Ministry for the Environment developed the Waste Analysis Protocol (WAP) in 1992 to guide the collection of statistically robust information on waste composition in New Zealand. Waste materials were classified into one of eight categories.

The Ministry reviewed and revised the WAP in 2002 and it became known as the Solid Waste Analysis Protocol (SWAP). The SWAP retains the core methodologies of the earlier protocol but has four additional categories. The WAP paper, metal, construction and demolition, and other categories were split into more detailed categories in the SWAP.

Waste composition categories used to report solid waste composition

WAP primary category SWAP primary category Description
Paper Paper Recyclable paper, such as newspaper and cardboard, and non-recyclable paper, such as milk containers and waxed paper
Nappies and sanitary Disposable nappies, feminine hygiene products and paper towels
Plastic Plastic Both recyclable and non-recyclable plastics
Organic Putrescibles Kitchen/food waste, green waste, other organic waste such as food processing waste
Metal Ferrous metal Metal products predominately made from steel
Non-ferrous metal Other metal, such as aluminium, copper, lead
Glass Glass Recyclable glass, such as bottles and jars, and other products including glass, such as televisions and computer monitors
Construction and demolition Rubble Concrete, rocks, plasterboard and ceramics
Timber Timber lengths, furniture, sawdust
Other Textiles Clothing, carpet
Rubber Tyres, foam mattresses
Potentially hazardous Potentially hazardous Material with potentially toxic or eco-toxic properties or having properties requiring special disposal techniques (includes sewage sludge, paint, medical waste, solvents, asbestos and oil)

The SWAP data programme began in 2002 to measure waste composition at four indicator sites – Silverstream, Kaikoura and Green Island landfills, and Matamata transfer station – using the new protocol. This established baseline waste composition data for New Zealand. These four sites were re-surveyed in 2007–2008 to enable the detection of any trends over time.

Cover material is excluded from the analysis because it is used for landfill management. A large quantity of potentially hazardous contaminated soil disposed of at Silverstream Landfill during the survey period was also excluded because it was a one-off disposal that was unusual and significantly skewed results for that landfill.

The waste composition of the indicator sites can be compared with those of a larger sample of landfills to determine how well the indicator sites reflect wider waste disposal patterns.

Want to know more?

The SWAP Baseline Programme describes how waste composition is measured in New Zealand and presents data from waste surveys and audits.

This information has come from the Solid waste composition environmental report card.

Return to composition of solid waste page

Last updated: 31 July 2009