The category /transport/car/generic/ipcc/us/alternativefuels contains data on greenhouse gas emissions associated with alternatively-fuelled (ethanol, cng, lpg) US cars, sourced from the IPCC Guidelines for National Greenhouse Gas Inventories.
The IPCC methodology for greenhouse gas emissions associated with 'mobile combustion' recommend calculating CO2 emissions on the basis of fuel consumed, whereas those of CH4 and N2O vary more directly with other factors such as vehicle type, emissions control standards, and distance travelled. Therefore, this category provide a number of options for calculating car-associated greenhouse gas emissions, depending on which combination of fuel consumption, fuel efficiency and distance are specified.
To use this category, set the vehicle fuel type using the fuel drill options. For some alternative fuels, IPCC methodology provides a range of emissions factors. Where necessary, the factorType drill option to specify usage of lower, upper or mean emissions factor estimates.
Users can then choose between specifying only fuel consumption, or both fuel consumption and distances travelled.
Specifying fuel used only
Set the volume of fuel consumed using the fuelConsumed profile item value. If required, the occupancy profile item value can be specified, representing the number of passengers for which emissions are accountable. If no occupancy is specified, Discover assumes an occupancy of 1. The returned amount represents 'CO2 emissions' associated with that volume of fuel shared amongst all passengers.
Specifying fuel used and distance travelled
If both fuel consumed and distance travelled are specified, Discover can use the IPCC methodology to calculate both CO2 and non-CO2 (i.e. CH4 and N2O) emissions, and therefore the returned value represents CO2e emissions (i.e. total greenhouse gas emissions expressed as the quantity of CO2 which would produce the same global warming effect).
If specifying values for distance and fuel consumption, both the distance travelled and the fuel consumed can be specified in a number of different ways, as described below. In any case, the occupancy profile item value can be specified, representing the number of passengers for which emissions are accountable. If no occupancy is specified, Discover assumes an occupancy of 1. The returned amount represents CO2 emissions associated with that volume of fuel shared amongst all passengers.
Setting the fuel consumed
To set the fuel consumed, users can specify the volume using the fuelConsumed profile item value. Alternatively, users can specify the rate at which their vehicle consumes fuel using the fuelEfficiency profile item value. In this case, Discover calculates the total fuel used from this 'efficiency' value together with the value for distance travelled (see below). CO2 emissions are based on this fuel consumption, while non-CO2 emissions are calculated directly from the distance travelled.
Setting the distance travelled
To set the distance travelled users may specify a total distance using the distance profile item value. Alternatively, users can specify a number of journeys of some fixed or average distance, by setting the distancePerJourney and numberOfJourneys profile item values. The total distance will then be calculated from these two profile item values.
If a specific number of journeys is taken on a regular basis, users can additionally choose to specify a frequency interval associated with the numberOfJourneys profile item value by specifying one of the following options using the frequency profile item value: