Emission factors measure the amount of green house gasses released by a process or activity. Typically, there are individual emission factors for each green house gas, although often they are consolidated into the CO2 equivalent emission. Precise emission factors are published by many agencies. We just describe the principles. Emission factors are crucial in determining the carbon footprint of an organisation.
Emissions from Burning Fuels
The burning of most fuels produces green house gas emissions, though in different amounts. Values for CO2e vary from 204t/MWh for natural gas to 329t/MWh for use of coal in industrial processes.
Emissions from Electricity
|Electricity Emission Factor||Avoided Emission Factor|
|t CO2e / MWh||t CO2e / MWh|
|Oregon||0.148||0.781||Low emissions due to use of hydro|
|Colorado||0.913||0.900||High emission factor due to predominance of coal|
|Austria||0.197||0.558||Low emission factor due to hydro|
|UK||0.476||0.643||Balanced energy mix|
|Germany||0.541||0.829||Balanced energy mix|
|France||0.083||0.849||Ultra low emission factor due to use of nuclear energy|
|Peru||0.148||0.826||Low emission factor due to use of hydro|
|India||1.005||0.900||High emission factor due to predominance of coal|
Emissions from photovoltaic cells:The manufacturing of solar cells is energy-intensive; the purer the silicon used the more energy is required. The CO2 emissions from that process, however, are believed to be compensated for after just one year of operation.
Emissions from nuclear energy:There is a lot of debate about the figures, especially around processing of uranium from mining to enrichment. Additionally, fossil fuels are required for backup generators used during downtime, waste disposal and de-commissioning.
In official fuel disclosure data, however, those emissions from nuclear or renewables can be neglected and assumed to be zero.
Emission Factors for Other Activities
For many processes and activities, it is very difficult to determine exactly how much fuel is burnt. In addition, green house gas emissions do not just stem from burning fossil fuels. They are side effects of many other processes both man-made and natural. Therefore, factors have been published that convert easily observable volume of an activity to estimated emissions. We have lsited some examples:
|Category||Sub-Categories||Observable Unit||Emission Factor CO2e|
|Passenger Transport||Size: e.g. Medium Sized Car||Distance travelled in km||0.2128 kg/km|
|Freight Transport||Weight class and load factor. E.g. 7.5 - 17t, 50% loaded||Distance travelled in km||0.75 kg/km|
|Refrigerator / Aircondition||
Type of refrigerant and type of euqipment
E.g. HFC-134 in a domestic fridge
|Installation||Weight of euqipment in kg||10 kg/kg|
|Operation||Weight of equipment in kg and time of operation in years||3 kg / (kg year)|
|Disposal||Weight of equipment in kg||8 kg/kg|
E.g. Paper, Hotel, pesticides, fish, computer services, education - i.e. pretty much everything
|Money spent in £||
Paper: 1.3 kg / £