The emissions calculation methodology is based upon emissions factors which relate mass, volume, or energy-based quantities of biofuel with their associated quantity of greenhouse gas emissions.
Because the fuels represented in this category are derived from recently grown biomass, the direct emissions they produce on combustion are mostly benign from the point of view of atmospheric warming: the carbon released from the biofuel has only recently been sequestered from the atmosphere (during plant growth) and therefore does not represent a net contributor to atmospheric CO2 concentrations. As such, emissions according to this methodology are differentiated into two types:
- 'direct' emissions represent those greenhouse gases emitted during combustion which do cause a net contribution to atmospheric CO2 concentrations.
- 'indirect' emissions represent those greenhouse gases emitted in association with stages in the fuel production chain such as raw material extraction and delivery, and therefore considered to 'embodied' within the fuel.
- 'life cycle' emissions are the sum of direct and indirect emissions which contribute to atmospheric CO2 concentrations.
- Emissions which are 'outside of scopes' are equivalent to the CO2 absorbed from the atmosphere during growth of the biomass. These do not cause a net contribution to atmospheric CO2 concentrations
Emissions factors relating to the following calculation requirements are available for each biofuel type:
- direct emissions by mass: direct CO2e emissions per unit fuel mass
- indirect emissions by mass: indirect CO2e emissions per unit fuel mass
- life-cycle emissions by mass: total/life-cycle CO2e emissions per unit fuel mass
- non-scope / biogenic emissions by mass: biogenic CO2 emissions per unit fuel mass
- direct emissions by volume: direct CO2e emissions per unit fuel volume
- indirect emissions by volume: indirect CO2e emissions per unit fuel volume
- life-cycle emissions by volume: total/life-cycle CO2e emissions per unit fuel volume
- non-scope / biogenic emissions by volume: biogenic CO2 emissions per unit fuel volume
- direct emissions by energy: direct CO2e emissions per unit fuel energy
- indirect emissions by energy: indirect CO2e emissions per unit fuel energy
- life-cycle emissions by energy: total/life-cycle CO2e emissions per unit fuel energy
- non-scope / biogenic emissions by energy: biogenic CO2 emissions per unit fuel energy
How to use this category
Choosing a specific activity type
To use this methodology, specify the fuel type using the fuel drill down choice.
Activity data required
Since emisisons according to this methodology are directly proportionate to fuel quantity, the quantity of fuel used must be specified using either the mass, volume or energy profile item values.
Results and calculation
CarbonKit returns the quantity of greenhouse gas emissions associated with the quantity of fuel specified. The following discrete amounts are returned:
- directCO2e: direct CO2e emissions
- indirectCO2e: indirect CO2 emissions
- lifeCycleCO2e: life-cycle CO2e emissions
- bioCO2: biogenic CO2 emissions
The CO2e emissions factors contained within this methodology are presented in a mixture of units. Each fuel is prepresented by per unit energy emissions factors of the form kg [emissions] per GJ. In addition, biodiesel and bioethanol are represented by volumetric emissions factors (kg [emissions] per litre), while biomethane is represented by a mass-based one (kg [emissions] per kg).
For consistency, and user flexibility, all fuels have been provided with a full suite of volumetric, energetic and mass-based emissions factors. The mass-based factors for biodiesel and bioethanol, and the volumetric factors for biomethane, were derived from the existing mass/volume factors using density values published in the same DEFRA GHG Conversion Factors source documentation.
Users of CarbonKit can, of course, choose to specify their consumption in any appropriate unit with the CarbonKit handling any required conversions.