The Green Vehicle Guide (GVG) emissions data used to rank vehicles is 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 Ranking & Measurement for more information.
The sum of the emissions from the various stages in a vehicle’s production, operation and disposal are often collectively referred to as “lifecycle emissions”. They include emissions produced from the manufacturing process, for both the vehicle and its fuel and from transporting the vehicle to the location of its first point of sale. This information page provides guidance on how these emissions are treated on the GVG.
While the GVG data does not represent the total picture in terms of a vehicle’s environmental impact, the available data suggests that it reflects the dominant proportion of that impact (at least for conventionally fuelled vehicles).
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 reported on the GVG 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 greenhouse gas emissions) in a cars 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 product the fuel for the vehicle’s use as discussed below (but this is a relatively small proportion of the total in conventional vehicle. For example a 2010 lifecycle study1 estimated that in total around 90% of primary energy consumption occurs during the vehicle use (78%) and fuel production phase. At this stage we are not aware of significant lifecycle data for electric vehicles or plug-in hybrids. Most recent studies are indicating that the majority of primary energy consumption for electric vehicles also occurs during vehicle use.2,
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 the Environment 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.
To help users estimate their lifecycle emissions from both the production and combustion of fuel used to power their vehicle, the GVG now provides a column with an estimate of ‘Fuel Lifecycle Emissions’ for each vehicle. Estimates for are based on national average factors from the National Greenhouse Accounts and can be customised for your home state and renewable energy consumption using the ‘Advanced Options’ tool at the top right of the search results page.
The calculations for the fuel lifecycle emissions estimates in the GVG are based on Scope 1, Scope 2 and Scope 3 Emissions Factors from the NGAF, as applicable (specifically Tables 4, 40 and 41). The attached Excel spreadsheet outlines the factors and calculations to determine the final CO2 emissions figure in g/km.
1 See ‘How can our cars become less polluting? An assessment of the environmental improvement potential of cars’, Leduc, G., Mongelli I., et al, Transport Policy 17 (2010) 409-419 at: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VGG-500Y5D5-1&_user=10&_coverDate=11%2F30%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=50ecc7a76be6cc9390f1bffb46f12d39&searchtype=a
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