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8. Unique emissions factors

Climate Change (Unique Emissions Factors) Regulations 2009: 14–17

8.1   Overview

A waste combustion participant may apply for approval to use a unique emissions factor (UEF). This allows a waste combustion participant to use an UEF if it considers that its fuels have particular properties or the firm has better fuel combustion efficiencies than are assumed in the default emissions factors.

There are two methods provided to calculate a UEF for waste combustion. The resulting UEF would then be used in either standard reporting option 1 or option 2 above. A participant seeking a UEF for any class of waste that is entirely biomass must use the periodic source testing approach. A participant applying for a UEF for a class of waste that consists of, or contains, non-biomass can use either approach.

The standard testing option develops an emissions factor for CO2 from specified testing of fuel samples for carbon content and gross calorific value. The samples must be representative of the fuel being combusted over the course of a year.

The periodic source testing option requires the estimation of total emissions over a measurement period (not necessarily a year) in accordance with the same method prescribed in section 7 above. A UEF can then be developed by dividing total emissions by the amount of energy consumed during that measurement period.

Samples must be taken at a sufficient frequency and duration to ensure that extrapolations provide representative estimates of emissions across the full range of operating conditions.

Read a description of this figure

An overview flow chart of the methodological options for developing a unique emissions factor for waste combustion activities in the SEIP Regulations.

8.2   Applications

The UEF must be based on the sampling, testing and calculation methods set out in regulation, the results of which must be independently verified.

An application for approval of a UEF must:

  • describe the class of waste covered by the UEF, with well-defined parameters so that the fuel may be easily identified and accounted for separately from fuel that is not within the class
  • be accompanied by a verifier’s statement and a plan for ongoing testing
  • be submitted to the Chief Executive of the Ministry for Economic Development by 31 January in the year following the first year to which the UEF relates.

8.3   Eligibility

An application may only be submitted if the UEF differs from the default emissions factor that would otherwise apply by more than the estimated uncertainty. As defined in regulation, this is the uncertainty associated with sampling and testing used to establish the unique emissions factor, estimated at a 90 per cent confidence level.

The participant is required to estimate the uncertainty around the unique emissions factor and submit this information to the verifier.

8.4   Verification

The sampling, testing and calculations undertaken to develop a UEF must be independently verified. A recognised verifier must review the records provided by the applicant and assess these against the process outlined in the regulations to establish and calculate the UEF. A list of recognised verifiers will be posted at www.eur.govt.nz.

8.5   Use of a unique emissions factor

Details of approved unique emissions factors, including the name of the participant and any conditions of approval, will be published in the New Zealand Gazette.

If approved by the Chief Executive of the Ministry of Economic Development, a unique emissions factor may be used until:

  • there is a material change in any of the information or factors on which the Chief Executive’s approval was based, or the relevant legislation, or
  • any conditions to which the approval is subject cease to be met or complied with.

To help determine when a material change might occur, participants are required to submit a plan for ongoing sampling and testing with their application. The Chief Executive may also grant approval subject to any conditions considered appropriate. This could, for example, include a requirement to submit the results of ongoing testing.

Example 1: standard option

Information to collect How to collect
  • representative samples of the class of waste that the UEF is sought for
  • standard sampling techniques
  • tonnes of obligation fuel component of any used or waste oil combusted, if sought
  • through documentation with used or waste oil supplier
  • carbon content, gross calorific value, biomass content
  • through testing of the samples

Step one: sample and test

Future Energy wishes to apply for a unique emissions factor for the used tyres it combusts. The firm takes several samples of tyre materials. It considers the samples it has taken are representative of the range of used tyres that it combusts.

These samples are tested for carbon content, calorific value and biomass content.

Class of waste Mean carbon content
tC/t		 Mean non-biomass fraction Mean gross calorific value TJ/t Emissions factor for carbon
tCO2-e/tC		 Emissions factor
(tCO2-ee/TJ)
Used tyres 0.85 0.95 0.027 3.6641 109.58
Emissions factor CH4         0.663
Emissions factor N2O         1.305
Emissions factor CO2e         111.6

Step two: calculation

Using the data above, the firm calculates the UEF for which it seeks approval:

UEF = EFCO2 + EFM+N where EFCO2 = (mC x EFC x mNB) / CV
       =          (0.85 × 3.6641 × 0.95) + 1.969
                                 0.27
                    = 111.6 tCO2-e / TJ

Step three: estimate uncertainty

The firm estimates the uncertainty associated with the sampling and testing undertaken, at a 90 per cent confidence level, to be plus or minus 9 per cent. The expected maximum emissions factor is

1.09 × 111.6 tCO2-e / TJ = 121.6 tCO2-e / TJ

As the DEF that would otherwise apply is 150.99 tCO2-e / TJ for used tyres, this UEF passes the eligibility threshold.

Example 2: periodic source testing

Information to collect How to collect
  • volumetric flow rate from the stack
  • pressure of the gas stream in kilopascals
  • temperature, in Kelvin, of the gas stream
  • periodically from direct measurement of stack gas emissions
  • CO2, CH4 and N2O concentrations in the gas stream
  • at the same time that the information above is collected
  • a  representative estimate of the non-biomass CO2 fraction in the gas stream
  • by sampling and testing or automatically through installed equipment
  • tonnes of obligation fuel component of any used or waste oil combusted, if sought
  • through documentation with used or waste oil supplier
  • gross calorific value of any obligation fuel combusted, if sought
  • through representative sampling and testing
    expressed as a weighted average
  • total energy output by the combustion process over the year in terajoules
  • through standard operation monitoring, such as from the amount of steam produced or water vaporised
  • no standards are stipulated, but for reference, a commonly used standard is ASME PTC 6-2004
  • estimated efficiency of the particular equipment
  • through operational estimation and monitoring
  • no standards are stipulated, but for reference, a commonly used standard is ASME PTC 6-2004

Step one: taking measurements to estimate greenhouse gas mass rates

Future Energy wishes to apply for a unique emissions factor for a particular boiler that combusts used tyres using the periodic source testing method. The firm takes several measures of stack emissions’ characteristics over a period of 12 weeks. It considers the measures it has taken are representative of the full range of operating conditions of the plant over the full year.

These measurements are used to calculate the mass rate of each greenhouse gas per second. The firm also wishes to use the data it records on energy produced and the estimated efficiency of the boiler to determine the amount of energy that is consumed, as it does not have a weighbridge.

Class of waste combusted Representative mass rate tonnes per second Non-biomass CO2 Time
(seconds)		 Emissions
(tCO2-e)
  CO2 CH4 N2O      
Waste – consisting of or comprising non-biomass 0.0444 1.111e-5 6.389e-7 0.55 6,652,800 165,331
Total           165,331
Class of waste combusted Energy output Efficiency Total emissions tCO2-e Emissions factor
(tCO2-e/TJ
Waste – consisting of or comprising non-biomass 1250 TJ 0.73 165,331 94.92
Total        

Step two: calculation

Using the data above, the firm calculates the UEF for which it seeks approval:
UEF        =          total emissions / energy consumed

total emissions =          (0.0444 x 0.55 x 6,652,800) + (1.111e-5 x 21 x 6,652,800) + (6.389e-7 x 310 x 6,652,800) = 165,331 tCO2-e

total energy consumed = 1250 / 0.73 = 1712 TJ
UEF = 165,331 / 1712 = 96.57 tCO2-e/TJ waste

Step three: estimate uncertainty

The firm estimates the uncertainty associated with the measurements and estimates of energy produced and boiler efficiency, at a 90 per cent confidence level, to be plus or minus 25 per cent. The expected maximum emissions factor is

1.25 ×96.57 tCO2e / TJ waste = 120.7 tCO2e / t waste

As the DEF that would otherwise apply is 97.53 tCO2-e / t waste, this UEF does not pass the eligibility threshold.