3. Emission factors and methods 2008

3.1   Scope 1: Direct emissions

3.1.1   Stationary combustion of fuels

In line with the reporting requirements of ISO 14064-1 and The GHG Protocol, emission factors are provided to allow calculation of CO₂, CH₄ and N₂O separately.

Table 1:      Fuel combustion emission factors (fuels used for stationary combustion) – 2008

Assumptions

The kg CO₂-e per activity unit emission factors supplied in Table 1 are derived using calorific values sourced from the New Zealand Energy Data File 2009. The calorific values used can be found in Appendix 1.

All emission factors incorporate relevant oxidation factors which are sourced from New Zealand’s Greenhouse Gas Inventory 1990–2007. Oxidation factors allow for the small proportion of carbon that remains unoxidised due to incomplete combustion, and remains as soot and ash. The oxidation factors used for each of the fuels can be found in Appendix 1.

The emission factors provided above account for the Scope 1 emissions resulting from fuel combustion. They are not full fuel cycle emission factors and do not incorporate Scope 3 emissions associated with the extraction, production and transport of the fuel.

The default coal emission factor is assumed to be the same as the sub-bituminous coal emission factor on the basis that the majority of coal use is of sub-bituminous coal. ⁶

The Automotive Gas Oil-50 ppm Sulphur emission factor (provided in the Energy Greenhouse Gas Emissions (2009) publication) has been used as the default emission factor for diesel.

Example calculation

A commercial organisation uses 1400 kg of LPG to heat one of its office buildings in 2008.

CO₂ emissions = 1400 * 2.96 = 4144 kg CO₂
CH₄ emissions = 1400 * 0.00109 = 1.526 kg CO₂-e
N₂O emissions = 1400 * 0.00875 = 12.25 kg CO₂-e
Total CO₂-e emissions = 1400 * 2.97 = 4158 kg CO₂-e

3.1.2   Transport fuels (where fuel use data is available)

Scope 1 emissions from transport occur from vehicles which are owned or controlled by the reporting organisation. The most accurate way to quantify the emissions associated with transport is by using information on the quantity of fuel used.

Emission factors for combustion of transport fuels are reported in Table 2. The emission factors are sourced from the Energy Greenhouse Gas Emissions (2009) publication.

Table 2:      Fuel combustion emission factors (transport fuels) – 2008

Assumptions

The kg CO₂-e per activity unit emission factors supplied in Table 2 are derived using calorific values sourced from the New Zealand Energy Data File 2009. All emission factors incorporate relevant oxidation factors which are sourced from Energy Greenhouse Gas Emissions (2009).

The default petrol factor is a weighted average of regular and premium petrol based on 2008 sales volume data from the New Zealand Energy Data File 2009. It should be used when petrol use data does not distinguish between regular and premium petrol.

As with the fuels for stationary combustion these emission factors are not full fuel cycle emission factors and do not incorporate the Scope 3 emissions associated with the extraction, production and transport of the fuel.

Example calculation

An organisation has 15 petrol vehicles. They used 40,000 litres of regular petrol in 2008.

CO₂ emissions = 40,000 * 2.30 = 92,000 kg CO₂
CH₄ emissions = 40,000 * 0.0136 = 544 kg CO₂-e
N₂O emissions = 40,000 * 0.0155 = 620 kg CO₂-e
Total CO₂-e emissions = 40,000 * 2.33 = 93,200 kg CO₂-e

3.1.3   Transport where no fuel data is available (based on distance travelled)

If your records only provide information on kilometres travelled, and you do not have information on fuel use, the emission factors in Table 3 can be used to calculate emissions from transport. Note, however, that factors such as individual vehicle fuel efficiency and driving efficiency mean that kilometre-based estimates of CO2-e emissions are less accurate than calculating emissions based on fuel-use data. The emission factors in Table 3 should therefore only be used if information on fuel use is not available.

Table 3:      Transport emission factors (based on distance travelled) – 2008

Assumptions

The above emission factors in Table 3 assume that all representative vehicles are petrol. The emission factors are derived by multiplying the default petrol emission factor from Table 2 by ‘real world’ fuel consumption rates ⁷for the petrol light vehicle fleet, based on information from New Zealand vehicle fleet Statistics for 2008 (Ministry of Transport). ‘Real world’ fuel consumption rates take into account ‘real world’ effects such as driver behaviour. Due to lack of data it is not currently possible to derive ‘real world’ fuel consumption rates for vehicles which use other fuels (eg, diesel, LPG). The above CO₂-e emission factors should therefore be applied to all vehicles (for which only kilometre travelled information is available), regardless of the type of fuel used.

The above emission factors are averages and therefore do not reflect the variability in fuel consumption rates between individual vehicles.

The default emission factor (for vehicles of unknown size) is the same as that for medium vehicles (1600 – <2500 cc) ⁸.

Example calculation

An organisation has three vehicles which it owns. They are all large vehicles and travelled a total of 37,800 km in 2008.

CO₂ emissions = 37,800* 0.306 = 11,567 kg CO₂
CH₄ emissions = 37,800* 0.00181= 68 kg CO₂-e
N₂O emissions = 37,800* 0.00206 = 78 kg CO₂-e
Total CO₂-e emissions = 37,800* 0.310 = 11,718 kg CO₂-e

3.1.4   Refrigerants

Greenhouse gas emissions from hydrofluorocarbons (HFCs) are associated with unintentional leaks and spills from refrigeration units, air conditioners and heat pumps. While quantities of HFCs reported in a business emissions inventory may be small, HFCs have very high global warming potentials (commonly 1300 to 3300 times more potent than CO₂) and emissions from this source may therefore be material. In addition, emissions associated with this sector are growing significantly as they replace hydrochlorofluorocarbons (HCFCs). ⁹

Scope 1 emissions from refrigeration occur from refrigeration units which are owned or controlled by the reporting organisation. If the unit is leased, associated emissions should be reported under Scope 3 emissions.

Emissions of HFCs are not calculated using emission factors, rather they are determined by estimating leakage from refrigerant equipment. Maintenance engineers can be asked to provide the actual amounts that are used to top up equipment (ie, to replace what has leaked).  The Ministry recommends three alternative methods for estimating leakage, depending on the equipment and available information.  The 2008 guidance describes these methods in detail.  These methods have not changed, and rather than repeat the text here, the user is referred to the 2008 version of the Guidance for Voluntary, Corporate Greenhouse Gas Reporting, ¹⁰ and the associated GHG Protocol HFC tool (WRI/WBCSD 2005).  The 2008 version of the Guidance for Voluntary, Corporate Greenhouse Gas Reporting however, makes an incorrect statement about the global warming potential of R22.  For global warming potential of R22 readers are directed to the IPCC National Greenhouse Gas Inventory Guidelines. ¹¹

If you consider it likely your emissions from refrigerant equipment and leakage is a material proportion of your total emissions (ie, >5 per cent), then you should include them in your emissions inventory. You may need to carry out a preliminary screening test to determine materiality.

3.2   Scope 2: Electricity indirect emissions

3.2.1   Purchased electricity

An emission factor for the consumption of purchased electricity (by end users) is calculated on a calendar year basis, and accounts for the emissions from fuel combustion at thermal power stations. It also includes a relatively small proportion of fugitive emissions from geothermal generation.

The emission factor for the consumption of purchased electricity and the emission factor for transmission and distribution line losses have been aligned with the definitions used in the GHG Protocol.

The electricity emission factor covers purchased electricity which has been bought from an electricity supplier who sources its electricity from the national grid. ¹²

Table 4:      Emission factor for the consumption of purchased electricity – 2008

Assumptions

As with the fuels for stationary combustion emission factors, this emission factor does not incorporate emissions associated with the extraction, production and transport of the fuels burnt to produce electricity.

This emission factor does not account for the emissions associated with the electricity lost in transmission and distribution on the way to the end user. Under the reporting framework of The GHG Protocol the emissions associated with transmission and distribution line losses are Scope 3 emissions. Table 5 contains an emission factor for transmission and distribution line losses.

The emission factor in Table 4 is derived from the net electricity generation data (as opposed to consumption data) in the New Zealand Energy Data File 2009. This is explained in more detail in the section below covering transmission and distribution line losses.

Notes on the use of electricity emission factors

The emission factor provided in Table 4 is an average over the calendar year to which the emission factor relates and is used for reporting the annual emissions associated with the consumption of purchased electricity.

A grid-average emission factor best reflects the CO₂-e emissions associated with the generation of a unit of electricity, purchased from the national grid, in New Zealand in 2008.

Retailer-specific electricity factors for grid electricity may be considered in the future. At this stage, however, there is insufficient information to prepare such factors and no clear consensus on the advantages of this approach. It is suggested users contact the Ministry for advice on carbon neutrality claims by electricity retailers.

The grid-average emission factor cannot be used for calculating abatement by intervention or reducing the use of thermal generation (eg, for an offset project). A marginal emission factor is more appropriate in these circumstances, because it is designed to take into account the change in electricity generation at the margin. Users wanting more information on marginal electricity emission factors are advised to contact the Electricity Commission. A report on Carbon Abatement Effects of Electricity Demand Reductions is also now available on the Ministry for Economic Development’s website. ¹³

Example calculation

An organisation uses 800,000 kWh of electricity in 2008. Their Scope 2 emissions from electricity are:

Total CO₂-e emissions = 800,000 * 0.195 = 156,000 kg CO₂-e

3.3   Scope 3: Other indirect emissions

3.3.1   Transmission and distribution line losses for purchased electricity

The transmission and distribution line losses emission factor accounts for emissions from the generation of the electricity lost in the transmission and distribution network due to inefficiencies in the grid. Under The GHG Protocol reporting framework, emissions from the generation of electricity that is consumed in a transmission and distribution system should be reported as a Scope 3 emission by end users.

The emission factor for transmission and distribution line losses is the difference between the generation and consumption emission factors reported by the Ministry of Economic Development on their website. ¹⁴

Table 5:      Transmission and distribution line losses for purchased electricity – 2008

Assumptions

This emission factor covers grid purchased electricity, bought by an end user. It is an average figure and therefore makes no allowance for distance from off-take point, or other factors that may vary between individual consumers.¹⁵

This emission factor does not incorporate the emissions associated with the extraction, production and transport of the fuels burnt to produce the electricity.

Example calculation

An organisation uses 800,000 kWh of electricity in 2008. Their Scope 3 emissions from transmission and distribution line losses for purchased electricity are:

Total CO₂-e emissions = 800,000 * 0.020 = 16,000 kg CO₂-e

3.3.2   Transmission and distribution losses for distributed ¹⁶natural gas

The transmission and distribution losses emission factor for distributed natural gas accounts for fugitive emissions, from the transmission and distribution system, which occur during the delivery of the gas to the end user.

This emission factor is derived based on information from the Energy Greenhouse Gas Emissions (2009) and New Zealand Energy Data File 2009 publications.

Table 6:      Transmission and distribution losses for distributed natural gas – 2008

Assumptions

This figure represents an estimate of the average amount of CO₂-e emitted from losses associated with the delivery (transmission and distribution) of a unit of gas per unit of gas consumed through local distribution networks for 2008. It is an average figure and therefore makes no allowance for distance from off-take point, or other factors that may vary between individual consumers.

This figure assumes that all losses are attributable to gas consumed via local distribution networks. A small amount (<1 per cent) of emissions is attributable to losses occurring from delivery of gas to consumers who are directly connected to a high-pressure transmission pipeline.

This emission factor is therefore appropriate for use by customers who receive their gas through a local distribution network, and is not intended for customers who receive gas directly from the transmission system, or directly from a gas producer via high-pressure transmission lines.

This emission factor does not cover the emissions associated with the extraction and production of the gas.

Example calculation

An organisation uses 1000 gigajoules of distributed natural gas in 2008. Their Scope 3 emissions from transmission and distribution losses are:

Total CO₂-e emissions = 1000* 5.342 = 5.342 kg CO₂-e

3.3.3   Taxis and rental cars

Business travel in taxis and rental cars are likely to be a common source of Scope 3 emissions for most businesses. As with Scope 1 emissions from transport, the most accurate way to calculate emissions is based on fuel consumption data. However, this information may not be easily available, particularly for business travel in taxis. Table 7 provides emission factors for rental car and taxi travel, based on kilometres travelled, as well as an emission factor for taxi travel based on dollars spent.

Table 7:         Emission factors for travel in taxis and rental cars (based on distance travelled) – 2008

Assumptions

The emission factors for taxis and rental cars are the same as those found in Table 3 and the underlying assumptions are the same.

The default emission factor for rental cars is the same as that for medium vehicles
(1600 – <2500 cc). Data from the Motor Industry Association New Vehicle Sales database showed that for the period January 2002–July 2008, 60 per cent of rental vehicles purchased were in the medium vehicle size class.

The default emission factor for taxis is the same as that for large vehicles (>= 2500 cc) from Table 3. Data from the Motor Industry Association New Vehicle Sales database showed that for the period January 2002–July 2008, 84.2 per cent of taxis purchased were in the large vehicle size class.

The dollars spent emission factor is based on a national average figure of $2.50 per kilometre travelled. This figure is sourced from Taxicharge New Zealand and includes GST.

Example calculation

An organisation uses rental cars to travel 12,000 km in 2008. It also spends $18,000 on taxi travel.

Total CO₂-e emissions from rental cars = 12,000* 0.234 = 2808 kg CO₂-e
Total CO₂-e emissions from taxi travel = $18,000*0.124 = 2232 kg CO₂-e

3.3.4        Air travel

The emission factors provided in Table 8 are intended for use by organisations wishing to report their air travel emissions, based on the distance travelled per passenger. The emission factors provided follow those published by the UK Department for Environment Food and Rural Affairs (DEFRA) in their 2009 Guidelines to DEFRA / DECC's GHG Conversion Factors for Company Reporting. These are deemed to be the most suitable emission factors currently available. The DEFRA publication discusses the emission factor methodology in more detail, including changes in methodology over time.

Table 8:      Emission factors for air travel (based on distance travelled) – 2008

Assumptions

The emission factors contained in Table 8 are based on representative flight distances of: domestic 463 km, short haul 1108 km, and long haul 6482 km. The domestic emission factor should be applied to all domestic flights; the short haul emission factor to flights less than 3700 km; and the long haul emission factor should be applied to any flights greater in length than 3700 km.

DEFRA endorses a nine per cent great circle distance uplift factor to take into account non-direct (ie, not along the straight line between destinations) routes and delays/circling. This figure comes from the IPCC’s Aviation and the Global Atmosphere, Section 8.2.2.3, and is based on studies on penalties to air traffic associated with the European ATS Route Network. This figure is likely to be overstated in New Zealand (initial estimates from Airways New Zealand is that this figure is likely to be less than five per cent); however in the absence of a New Zealand-specific figure it is recommended that those wishing to take a conservative approach apply the nine per cent uplift factor by multiplying the factors in Table 10 by 1.09.

The emission factors provided above do not include radiative forcing (ie, non-CO₂ climate change impacts). The total climate impacts of aviation due to radiative forcing have been estimated by the IPCC to be up to two to four times those of CO2 alone. However, the science in this area is currently uncertain and a multiplier is not used for New Zealand’s national greenhouse gas inventory reporting. As the emission factors contained in this guide are intended to be consistent with New Zealand’s national greenhouse gas inventory reporting, it is not currently deemed appropriate to apply a multiplier to account for radiative forcing.

Example calculation

An organisation makes a number of flights from Auckland to Sydney (2171 km each way). The total distance travelled was 217,100 km.

Total CO₂-e emissions from air travel = 217,100* 0.0946 = 20,538 kg CO₂-e

3.3.5   Waste to landfill

The emission factors and methodologies provided below will help organisations in estimating their emissions from waste disposed of at a landfill. Emission factors are based on figures from New Zealand’s Greenhouse Gas Inventory 1990–2007 and methodologies are derived from IPCC good practice guidance. The base equation methodology provided on page 19 is termed “tier 1” under the IPCC 1996 guidelines and assumes all the potential emissions in a tonne of waste are released in the year of disposal.

Methodologies to determine emissions from wastewater treatment and solid waste incineration are not covered by this guide, as emissions are assumed to be negligible at the individual organisation level (with some exceptions for large industrial wastewater producers).

The anaerobic decomposition of organic waste in landfills generates methane (CH₄). Inventories should be adjusted to account for the landfill gas that is collected and destroyed.¹⁷ The methodologies outlined below provide for such adjustment depending on whether an organisation’s waste is sent to a landfill with (or without) a landfill gas collection system.

Methodologies

Two methodologies for determining a solid waste emission factor are provided. Choice of methodology depends on organisational knowledge of waste composition. It is preferable to know the composition of waste as it allows emissions to be more accurately quantified.¹⁸

Base equation

The base equation used in deriving the waste emission factors, as taken from the 1996 IPCC Good Practice Guidelines, is as follows:

Interpretation

Table 9 provides methodologies for four scenarios where composition of an organisation’s waste is / is not known, and is sent to a landfill that has / does not have a landfill gas collection system.

If the organisation has data on individual waste streams, but doesn’t know if the waste is going to a landfill with a gas collection system, then the default should be the factors for “without landfill gas recovery” (ie, overestimate rather than potentially underestimate).

If the organisation does not know the composition of its waste but knows it is going to a landfill with a gas recovery system, then it should use the default “mixed waste” emission factor found in Table 9 unless it is an office-based organisation. Note that this will be an inaccurate emission factor at the organisation level, as it assumes the organisation’s waste matches the national average mixed municipal waste composition. If an organisation has an advanced diversion system (to recycling and composting) then this methodology will overestimate emissions. If an organisation has no diversion system, then it could underestimate emissions.

Default emission factors for “office waste” are provided in Table 9. These should be used by office-based organisations that do not have information on the composition of their waste. The higher emission factors reflect the higher proportion of organic matter (eg, paper and food) found in office waste. The default office waste emission factors assume no diversion has occurred so if an organisation has an advanced diversion system then this methodology will overestimate emissions.

Table 9:      Emission factors for waste to landfill – 2008

Assumptions

The emission factors provided in Table 9 are based on 2007 data, however we recommend that they are used for the 2008 reporting period, as this is the most current data available.

Example calculation

An organisation disposes of 30 tonnes of garden waste to a landfill with a gas recovery system in 2008.

Total CO₂-e emissions from waste to landfill = 30,000* 0.545 = 16,350 kg CO₂-e = 16.35 tonnes CO₂-e