Fuel data input
How to use this tool
Background to audit calculations
The three main greenhouse gases associated with road transport are carbon dioxide, nitrous oxide and methane. Although all three contribute measurably to climate change, in most cases, the majority of transport greenhouse gas emissions are composed of carbon dioxide. Given also the fact that carbon emissions data are more readily available than both nitrous oxide and methane emissions, for the purposes of this audit tool, only carbon dioxide emissions are assessed.
Any audit of carbon emissions must include direct emissions as, for most powered transport modes, these will form the majority of total emissions. A more thorough analysis, however, should also include indirect emissions as these form a significant proportion of total emissions generated – in the case of light-duty vehicles, indirect emissions account for around 10-20% of life cycle emissions.
Furthermore, in cases where electric vehicles are used (eg electric cars, trains, etc), all emissions associated with these modes are produced upstream at the power station, and are therefore classed as indirect. These need to be included within an inventory as carbon emissions emitted at all locations contribute to global warming (unlike other air pollutants whose impacts are more local).
In most cases (e.g. petrol and diesel cars), indirect emissions associated with the fuel cycle exceed the level of emissions generated during vehicle manufacture, assembly and disposal. However, quantifying vehicle production and disposal emissions is also made difficult due to the lack of data in the public domain. For these reasons, only fuel cycle indirect emissions are usually assessed. These emissions are then added to the emissions produced during vehicle operation (i.e. tailpipe emissions).
The strength of this approach is that it is able to quantify the carbon emissions for a large range of vehicle fuels (petrol, diesel, liquefied petroleum gas and electricity) and vehicle technologies (combustion engines, battery-electric and hybrid-electric vehicles).
CO2 audit – methodology
Within the overall framework outlined above, therefore, the method used by this audit tool is to assess the amount of CO2 emissions by applying known factors to the quantity of fuel consumed. Not only does his approach provide one of the most accurate methods of CO2 assessment, it also relies on data that is available to most fleet managers. The emission factors use by this tool are as follows:
| Fuel | Direct CO2 emissions | Indirect CO2 emissions |
|---|---|---|
| Diesel | 2.63 kg/litre | 0.51 kg/litre |
| Petrol | 2.32 kg/litre | 0.41 kg/litre |
| LPG | 1.50 kg/litre | 0.22 kg/litre |
| Electricity | 0.00 kg/kWh | 0.53 kg/kWh |
References:
- DEFRA (2007) Act on CO2 Calculator: Public Trial Version: Data, Methodology and Assumptions Paper V1 June 2007
- Concawe (2006) Well-To-Wheels Analysis Of Future Automotive Fuels And Powertrains In The European Context. Report by Concawe, Eurcar and the EU Joint Research Centre, 2006; SMMT Annual CO2 Report: 2006.
- Camden (2006) Life Cycle Assessment of Vehicle Fuels and Technologies. Conducted by Ecolane on behalf of the London Borough of Camden.
