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Chapter 5: Ways to Calculate Tonnages

This chapter explains the different ways the weight of waste or diverted material can be measured or calculated.

Note that the volumetric and per capita methods may only be used by facilities approved to submit annual returns.

Methods applicable to all disposal facilities

Why do I need to specify how I will calculate tonnages?

The levy is calculated on the net tonnage of material disposed of at a disposal facility. To enter your returns on the levy system, you must have the information in tonnages.

Operators of facilities that do not record the weight of every load of waste, need to choose a reliable method that lets you convert the information you collect to a tonnage value. The options you can use are listed in the regulations, and described below.

What are my options for calculating the tonnage?

If there is a compliant and functioning weighbridge at the disposal facility, you must use it to measure gross tonnage, unless you have approval to use an ‘average weight per vehicle’ method.

If the facility does not have a weighbridge, you can:

  • use a compliant weighbridge located off site, or

  • measure the volume of waste and diverted material arriving at the facility and use an approved conversion factor to convert the volume to equivalent tonnage (conversion factors are listed in appendix 3).

If you have access to a compliant weighbridge (on or off site), you can apply to use an ‘average weight per vehicle’ for light vehicles and trailers, using an approved method. You can also apply for approval to use an average weight method based on assessment of the volume and use of conversion factors. This is explained in more detail in chapter 5.

Operators approved to submit annual returns can use alternative methods of assessing tonnage, as set out in chapter 5.

How do I inform you of my method for calculating the quantity of waste?

We will ask you to provide details of the method you currently use when we collect initial client set-up information.

If we don’t hear otherwise, we will assume you are using an on site weighbridge to measure tonnage.

If you wish to use a method other than weighing all waste and diverted material using an on site weighbridge, you need to ensure this is captured as part of your initial set-up information.

How do I change my method or introduce a new method?

You should notify us of any changes to your method or if you wish to introduce a new method for calculating the quantity of waste by contacting 0800 WDLEVY (0800 935389) or info@wastelevy.govt.nz

What if my weighbridge breaks down?

The Ministry recommends that disposal facilities with weighbridges have a backup plan in case of weighbridge breakdown or malfunction, for example, during power cuts.

You do not need to seek approval from the Ministry for your backup plan, but must keep records for auditing purposes. Your backup plan may include a suitable average tonnage methodology or a variation from an approved average tonnage methodology.

Using an on site weighbridge

If you are using an on site weighbridge, you must keep weighbridge records that specify:

  • the date the waste or diverted material entered the facility

  • the date and time the waste or diverted material was weighed

  • the weight of the waste or diverted material

  • gross and diverted tonnage.

Using an off site weighbridge

How should I use an off site weighbridge?

If your facility does not have a weighbridge, then you can accept waste that has been weighed using a weighbridge located somewhere else. To accept the tonnage measurement from an off site weighbridge, the customer will need to present a weighbridge ticket that shows the:

  • date and time the waste or diverted material was weighed

  • weight of the waste or diverted material in tonnes

  • registration plate details of the vehicle transporting the waste or material to the disposal facility.

We recommend that you do not accept, for the purposes of the levy, information on tickets more than six hours old. You must keep weighbridge tickets so you can provide them to us on request.

Off site weighbridges can also be used where the on site weighbridge is out of service. Off site weighbridges must be compliant with the provisions of the Weights and Measures Act 1987.

Using conversion factors

How should I use conversion factors?

You can use a conversion factor to convert the volume of waste or diverted material into weight. A schedule of these conversion factors is found in the Regulations and appendix 3 of this guide.

Formula 3: Calculating waste tonnage using a conversion factor

Assessed volume x Conversion factor = Gross tonnage

Assessed volume x Conversion factor = Gross tonnage

How do I calculate assessed volume?

You can measure the volume of waste by:

  • using a compliant measuring instrument,1 such as a tape measure, to measure the volume of the waste in the container

  • estimating the volume as accurately as possible, eg, using a container such as a skip bin with a measured volume

  • using information on the volume capacity of types of vehicle.

Using a compliant measuring instrument

You will have to measure the volume of waste or the dimensions of the container and make an assessment of how full the container is.

Formula 4: Calculating the volume of a container

Length x Width x Height = Volume in M3

Length x Width x Height = Volume in M3

Using a container of known volume

You can use a skip bin or any other container whose volume has previously been measured. Customers using your disposal facility dump their waste into the container. When the container is full, you deposit its contents into the disposal facility and record the volume of waste.

Estimating the volume using knowledge of volume capacity of vehicles

As a last resort, you can use your past experience of how much material can fit inside trailers, car boots, skip bins and other containers for which the volume can be easily calculated. Using this knowledge, you will then be able to assess as accurately as possible the volume of
that waste.

You must have formulas for this that are robust and can stand up to the scrutiny of an audit process. We do not recommend that this method is used at large landfills.

How do I apply the conversion factors?

Once you have calculated the volume of waste in the container (using one of the methods outlined above), you will need to identify its contents. This is critical to calculating its weight.

You can identify the contents by:

  • asking the customer

  • checking yourself, if the contents are easily visible

  • making an educated guess, if the container has come from a known supplier.

The operator’s judgement of the contents plays a large role, as most loads arriving at disposal facilities are mixed loads and it will be up to the operator to use his or her discretion to ensure that the appropriate conversion factor is applied.

Once you know what the waste is made up of, you multiply its calculated or estimated volume by the appropriate conversion factor.

Example 7: Gross tonnage calculated using conversion factors

Example 7: Gross tonnage calculated using conversion factors
Car boot with rubbish from clean up at home:

  • Car arrives at the disposal facility.
  • Measure volume capacity (in cubic metres) of the car boot using a measuring instrument.
  • Apply relevant conversion factor in Regulations for waste carried in rubbish bags or cars: 0.130 tonnes/m3.
  • The tonnage of waste to be disposed of is: Volume of car boot (m3) x 0.130 tonnes/m3

Example 7: Gross tonnage calculated using conversion factors

High density waste, such as a truck and trailer with abattoir waste:

  • Truck arrives at the disposal facility.
  • Measure volume of material (in cubic metres) carried by the truck using a measuring instrument.
  • Apply relevant conversion factor in Regulations for high density waste: 1.5 tonnes/m3.
  • The tonnage of abattoir waste to be disposed of is: Volume of truck x 1.5 tonnes/m3.

Using the average tonnage system

An average tonnage system allows you to weigh a sample of the light vehicles delivering waste to the disposal facility, and calculate an average weight of waste carried either for light vehicles as a group, or for specific types of light vehicles (eg, cars, vans). Then you would record the number of each type of light vehicle delivering waste and apply the average weight per vehicle to these vehicles, rather than weighing every vehicle. This method cannot be used for assessing diverted tonnage.

You may use an average tonnage system to calculate the gross tonnages entering the disposal facility. You may wish to use this method if it is not feasible to weigh all vehicles coming in and out of your facility, for example if you have a single weighbridge and/or large numbers of private vehicles delivering waste directly to the facility.

We allow the average tonnage system to be applied to light vehicles, generally vehicles that have a vehicle mass of 3.5 tonnes or less, or to trailers towed by those vehicles. The provision relates to the motor vehicles classes listed in appendix 2 of this guide. Note that while the majority of vehicles in the vehicle classes listed are less than 3.5 tonnes, some of the heavier passenger vehicles may weigh slightly more than this.

How do I apply to use the average tonnage system?

As explained earlier, you must have approval from the Secretary for the Environment to use the average tonnage system for levy returns.

Before applying for or switching to use an average tonnage system, we would recommend that you call or email the Ministry for the Environment Levy Administrator on 0800 WDLEVY (0800 935389) or info@wastelevy.govt.nz for assistance and further guidance about average tonnage systems.   

Application forms can be found on the Online Waste Levy System (OWLS): www.wastelevy.govt.nz.  The form specifies the information that must be provided, including survey data.

What if I want to start using an average tonnage method?

If you want to switch to an average tonnage method, you must apply for approval before you start using it. More information on the average tonnage method and how to apply to use it is provided below, , plus we recommend you phone or email the Ministry for the Environment Levy Administrator on 0800 WDLEVY (0800 935389) or info@wastelevy.govt.nz.

How do I calculate average tonnage?

The most straightforward way to calculate the average load weight for light vehicles is by weighing a number of light vehicle loads, either at random or consecutively.

The load weight of each vehicle must be worked out by weighing the vehicle before and after the waste has been dropped off. Operators can use either an on site or off site weighbridge or conversion factor. We strongly recommend you use a weighbridge.

The average load weight is then calculated by dividing the sum of the net load weights by the number of vehicles surveyed.

It is important that the timing of the survey caters for fluctuations over time in the type and weight of material received at a disposal facility. For example, during the week, it is more likely that commercial users will use the facility, while at weekends more householders are likely to bring waste.

We recommend that when undertaking a survey:

  • measurements should take place on both weekdays and on weekends

  • measurements should be taken during what you consider to be a ‘typical’ period. For example, surveys during summer holidays or following a major storm would probably not deliver results typical of waste flows throughout the year

  • at least 100 light vehicle loads are surveyed to provide a sufficient degree of accuracy for us to approve your application

  • you can calculate average load weights for specific vehicle types and these do not need to be the same groupings as the vehicle classes listed in appendix 2. For example, you could combine utes (class MA) and 4 wheel drive vehicles (class MC) as a vehicle type

  • if more specific vehicle types are weighed (such as cars, utes and trailers), there will be less variability in the load weights, and fewer than 100 loads of each vehicle type may need to be measured.

Does approval for using average tonnage expire?

Approval to use the average tonnage system will be granted for a specified period of three years or less. We recommend that you apply to renew your approval at least a month before your current term expires. This will give the Secretary time to respond to your application before your current approval expires.

If further approval is not granted by the time the previous approval expires, you must use an assessment of the weight of each vehicle load, either on site weighbridge, off site weighbridge or conversion factors, and let us know which one you’ve chosen.

Methods relating to annual returns

Using volumetric surveys

This method can only be used by facilities approved for annual returns.

What are volumetric surveys?

Volumetric surveys are a well-established method that uses topographical measurements to measure the volume of waste in a disposal facility. To estimate the annual tonnage received, a survey must be done at the beginning and end of the year.

Unless you already do topographical surveys, using this method is likely to be an expensive option.

How do I estimate tonnage from a volumetric survey?

To get tonnage figures, first you must measure the volume of waste deposited into the landfill during the year, from the topographical survey.

Next you must apply the appropriate conversion factor specified in the Schedule to the Regulations (see appendix 3). To select the appropriate conversion factor, you will need to know the density of the landfill. Density is estimated by excavating a hole of a measured size and weighing the waste that has been removed. Several samples need to be excavated and weighed to arrive at a reliable average density figure.

Appropriate documentation should be kept for using volumetric surveys for waste levy-related calculations. The documentation should include survey results signed off by a registered surveyor, and waste density measurements signed off by the disposal facility operator.

Using per capita waste disposal

This method can only be used by facilities applying to submit annual returns, and it can only be used to assess expected net tonnage.

When would I use per capita waste disposal as an estimate?

If your facility is unstaffed and records are limited, per capita waste disposal may be used. This method is only suitable for facilities receiving no more than 1000 tonnes of waste per year from small, isolated communities.

How does the per capita method work?

This method estimates the tonnage received, or expected to be received, in a facility by estimating the population of the facility catchment (ie, the number of people for whom this facility is the most convenient means of disposing of waste, who would use it regularly to dispose of most of their waste), and multiplying that population by standard per capita waste generation figures.

How do I estimate the catchment and population?

You do this by marking out the catchment on a map (using local knowledge about the waste disposal behaviour of residents and the proximity of other disposal facilities) and using Statistics NZ census data to determine the population of the catchment.

Census data are available at various scales, with ‘meshblocks’ being the smallest unit for which data are recorded. In rural areas, the ‘census area unit’ contains a few hundred individuals. Statistics NZ publishes maps of the boundaries of the census area units, and these can be cross-referenced to the waste catchment to estimate the population of the catchment.

Statistics New Zealand: www.stats.govt.nz
Phone: 0508 525 525 (toll free in New Zealand)
Hours: 8.00 am to 5.00 pm, Monday to Friday (excluding public holidays)

The quantity of waste disposed of per person will depend on whether or not your facility is used for wastes other than those generated by residential and agricultural activity. As part of the assessment process, you therefore need to determine if the disposal facility is used:

  • only by local rural residents

  • by residents of small rural centres

  • for cleanfill disposal

  • for disposing of construction and demolition material

  • for disposing of commercial/industrial waste.

If your facility is in a remote rural location, it is unlikely to be used regularly for any waste other than residents’ domestic waste. In this case, we recommend that a waste disposal rate of 0.260 tonnes per person per year is used.

If your facility receives wastes from both residential and farming activity, as well as the small-scale commercial and industrial activity typical of small population centres, we recommend that a figure of 0.500 tonnes per person per year is used.

If your facility receives wastes from special wastes, cleanfill, or medium- to large-scale industrial wastes, we recommend that you use a figure of 0.750 tonnes per person per year should be used for calculating its expected net tonnage.

Example 8: Waste disposal rate for residential waste only

An isolated rural disposal facility only receives domestic waste from rural residents. At a waste disposal rate of 0.260 tonnes per person per year, the expected net tonnage would be calculated by multiplying the assessed population by 0.260 (tonnes per person).

Example 9: Waste disposal rate for residential, farming and small-scale industrial and commercial waste

A smaller disposal facility close to a small rural centre receives only waste from rural residents and the rural centre. At a waste disposal rate of 0.500 tonnes per person per year, the expected net tonnage would be calculated by multiplying the assessed population by 0.500 (tonnes per person).

Example 10: Waste disposal rate for special wastes, cleanfill and medium-large scale industrial waste

A smaller disposal facility close to a small provincial centre serves local residents, and also receives waste from a saw mill and a freezing works. At a waste disposal rate of 0.750 tonnes per person per year, the expected net tonnage would be calculated by multiplying the assessed population by 0.750 (tonnes per person).


1 A compliant measuring instrument is one that complies with the Weights and Measures Act 1987.