This methodology represents greenhouse gas emissions associated with the freighting of goods in the geographic contexts of the US, UK and other regions. The data and calculation methodology is based on those provided in the Greenhouse Gas Protocol worksheet GHG emissions from transport or mobile sources (version 2.2), published in June 2011.
The emissions methodology is based upon emissions factors which describe the rate at which greenhouse gas emissions are produced during the freighting of goods in relation to distance travelled and the quantity of goods freighted. These emissions factors represent emissions associated with individual units of freight, which can be contrasted with similar transport-related emissions factors which describe emissions on the basis of entire vehicles (e.g. entire ship or lorry).
Emissions - expressed in terms of mass (e.g. kg) - are calculated by multiplying these rates (mass emitted per mass distance; e.g. kg CO2 per ton mile) by a distance (e.g mile) and quantity (e.g. ton) freighted.
The rate at which freight transportation produces greenhouse gas emissions varies with the mode of transport, depending on factors such as the fuel efficiency (i.e. the distance achieved per unit of fuel consumed) of the particular type of vehicle (e.g. lorry, plane, train, ship) as well as the typical freight loading. Fuel efficiency may be related factors such as the type of fuel used (e.g. petrol, diesel, biofuel, electricity) and the physical dynamics of the transportation context (i.e. road, rail, water, air). The loading of freight indicates the extent to which the emissions of the entire vehicle can be 'shared' between units of freight. Therefore, emissions factors for a broad range of generalised freight transport scenarios are provided.
A total of 75 specific types of freight transport scenarios are represented and are differentiated by transport type (i.e. air, heavy goods vehicle, plane, rail, ship), vehicle size (e.g. gross vehicle weight) and region (UK, US, other regions).
Aside from air freighting, which is represented by a CO2 emissions factor only, each freight transport type is represented by three distinct emissions factors which differentiate greenhouse gas emissions into the following types:
- CO2 emissions
- CH4 emissions
- N2O emissions
Activity data required
According to this methodology, greenhouse gas emissions are directly proportionate to the distance and quantity (mass) of freight transported, both of which therefore must be specified in order to make an emissions calculation.
Calculation and result
The returned quantities for this methodology represent CO2, CH4, N2O and CO2e emissions associated with the activity data (distance/fuel) specified. CO2e emissions represent all three gases, converted using these global warming potential). The individual quantities for CH4 and N2O represent absolute quantities rather than CO2e quantities. For some scenarios within this methodology, emissions factors for CH4 and N2O are not available. In these cases values of zero are returned for the respective gases together with a notification comment. CO2 and CO2e values are returned as normal.
Other Greenhouse Gas Protocol transport methodologies are available representing general transport fuel consumption, fuels consumed in specific transport contexts, passenger/public transport, and road transportation in the UK (with heavy goods), US and other regions.
The CO2 emissions factors contained within this methodology are presented in a mixture of units (i.e. kg [emissions] per short ton mile; kg [emissions] per tonne kilometer) in the original Greenhouse Gas Protocol source documentation.
For consistency, all CO2 factors are presented within the Discover platform in a common default unit: kg [emissions] per short ton mile. Emissions factors were converted using the tonne-kilometer-to-short-ton-mile conversion factor provided in the Reference - EF Fuel Use worksheet of the source documentation, i.e.
emission factor kg per short ton mile = emission factor kg per tonne kilometer * 1.45997231943488 tonne kilometers per short ton mile
Users of Discover can, of course, choose to specify their consumption in any appropriate unit with Discover handling any required conversions.
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