Estimating Non-road CO2 Emissions

The Green Vehicle Guide (GVG) ratings for both air pollution and greenhouse are based on tailpipe emissions measurements from specific vehicle models, and do not incorporate the other environmental impacts that may occur in the production of a vehicle, or the production of the fuel used in the vehicle.  The tailpipe measurements are undertaken in accordance with the certification tests each model must undergo to demonstrate their compliance with the Australian Design Rules (ADRs) before they are allowed to be sold in Australia.  This approach ensures that all models are compared on a common basis under controlled conditions.  See the information page on Ratings & Measurement for more detail on how the ratings are calculated.

In November 2010, amendments were made to the GVG website to enable the listing and rating of electric vehicles and plug-in hybrid vehicles.  These amendments include a new Fuel Production Emissions “calculator” on the Advanced Search page, which, if activated by a website user, estimates non-tailpipe CO2 emissions from the relevant fuels (including electricity) consumed by the individual models included in the search.

In light of these changes, we thought it would be useful to provide some advice regarding the emissions that can be produced from the processes to manufacture a motor vehicle and to produce the fuel to run the vehicle.  The sum of the emissions from the various stages in these processes are often collectively referred to as “lifecycle” emissions.  This information page provides guidance on how these emissions are treated on the GVG. 

The information below indicates that while the GVG ratings do not represent the total picture in terms of a vehicle’s environmental impact, the available data suggest that they reflect the dominant proportion of that impact (at least for conventional vehicles).

Lifecycle Emissions from Vehicle Manufacture

Like any manufactured product, the production of a motor vehicle can have environmental impacts, including the energy and emissions from the vehicle manufacturing process.  The level of recyclability of vehicle components, as well as the percentage of recyclable material used in the manufacture of the vehicle can also affect its overall impact.  These elements are not factored into the GVG ratings.  This is because objective, numerical values for these different factors do not exist at an individual model level and are never likely to, given the complexity, uncertainty and high costs associated with life cycle analysis.

To date, examinations of lifecycle environmental impacts of conventional vehicles indicate that the largest proportion of energy consumed (and associated carbon dioxide (CO2) emissions) in a car's normal lifecycle occurs during its operational (use) phase, and not from its production, nor the embodied energy in the materials from which it is made.  While this proportion will vary from manufacturer to manufacturer, plant to plant, model to model, and with fuel type, various studies report that the vehicle operation phase (at least for a conventional vehicle with an internal combustion engine) consumes around 85-90% of lifecycle energy use.  These estimates usually encapsulate the energy consumed to produce the fuel for the vehicle’s use as discussed below (but this is a relatively small proportion of the total in conventional vehicles).  For example, a recent lifecycle study[1] estimated that, in total, around 90% of primary energy consumption occurs during the vehicle use (78%) and fuel production (12%) phases.  At this stage, we are not aware of significant lifecycle data for pure electric vehicles or plug-in hybrids. More recent studies are indicating that the majority of primary energy consumption for electric vehicles also occurs during vehicle use. [2] [3]

Lifecycle Emissions from Fuel Production

The extraction, production and transport of the fuels on which vehicles operate requires energy and in the process, emissions of both air pollutants and greenhouse gases are produced.  While accurate figures are not available for the traditional air pollutants, the National Greenhouse Accounts Factors (NGAF) published by the Department of Climate Change and Energy Efficiency provides a set of factors which enable the estimated energy consumed in these processes to be converted to emissions of CO2 in grams.  These CO2 figures can subsequently be converted to a value in grams of CO2 per litre of fuel, and ultimately grams of CO2 per kilometre (using the GVG’s fuel consumption value for the vehicle).  The NGAF also provides factors for electricity to enable estimates of CO2 emissions from recharging a vehicle to be calculated.

On the matter of recharging electric vehicles, users can of course achieve a zero emissions outcome by choosing to recharge their vehicle using 100% renewable energy.  The major emerging charging infrastructure providers for electric vehicles in Australia have also committed to basing their systems on renewable energy.  However, if a user chooses to simply recharge an electric vehicle from the grid without electing to use renewable energy, the emissions produced from recharging will be highly dependent on the location of the power source.  Consequently, the GVG requires  users interested in these emissions  to nominate the relevant State or Territory in the Fuel Production Emissions “calculator” on the Advanced Search page (the location has no effect on the calculation for petrol, diesel or LPG). 

The estimated CO2 emissions from these calculations are listed separately in the new Fuel Production Emissions column on the Search Results page.  They are not counted in the determination of the Greenhouse Rating which (as explained in the Ratings & Measurement information page) is based on the Combined CO2 tailpipe emissions value obtained from the standardised ADR test conducted on all vehicles.

The calculations for the fuel production emissions estimates in the GVG are based on Scope 2 and/or Scope 3 Emissions Factors from the NGAF, as applicable (specifically Tables 4, 39 and 40).  The attached spreadsheet outlines the factors and calculations to determine the final CO2 emissions figure in g/km. 

[2] See 'Contribution of Li-Ion Batteries to the Environmental Impact of Electric Vehicles', Notter, N., et al; Environmental Science & Technology, 44:17 (2010) 6550-6556 at: http://pubs.acs.org/doi/abs/10.1021/es903729a

[3] See 'Preparing for a Life Cycle CO2 Measure', Patterson, J., Alexander, M. & Gurr, A., Low Carbon Vehicle Partnership, 25 August 2011 at: http://www.lowcvp.org.uk/assets/reports/RD11_124801_5%20-%20LowCVP%20-%20Life%20Cycle%20CO2%20Measure%20-%20Final%20Report.pdf

 
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