This methodology represents embodied energy, carbon dioxide (CO2) and CO2e emissions associated with the use of various materials as specified on the basis of mass quantities. The data and calculation methodology is sourced from the Inventory of Carbon & Energy (ICE), version 2.0 life cycle dataset, produced in conjunction with the University of Bath.
The methodology is based on factors which describe the quantities of energy and CO2 which are 'embodied' within unit quantities of various materials. By multiplying a quantity of material - in this case, a mass quantity - by these factors, an estimate of the embodied energy and emissions associated with that quantity can be calculated.
Embodied energy and emissions vary between types of material because of each material's differing raw material and manufacturing requirements. This methodology represents 266 different materials scenarios, each differentiated by their material name (e.g. cement, plastics, steel) and type and subtype descriptors (e.g. 6-20% fly ash (CEM II/A-V), Low Density Polyethylene Film, recycled).
Each specific type of material is represented by up to three data values, representing:
- embodied energy per unit mass (MJ/kg)
- embodied CO2 per unit mass (kg/kg)
- embodied CO2e per unit mass (kg/kg)
In addition, each material is described by a life cycle analysis boundary, indicating the stages in the material life cycle which are represented by the energy and CO2 factors, and in most cases author notes on the sourcing of the data.
Activity data required
Embodied energy and emissions are directly proportionate to the mass of material used, which therefore must be available in order to calculate.
Calculation and results
Embodied energy and emissions are calculated by multiplying the specified quantity of material used by the available factors. Up to three values are returned representing the embodied energy, and CO2 or CO2e emissions attributable to the specified quantity.
Data specified as a range of values
In some cases, the published data for embodied energy and/or CO2(e) for a particular material is provided in terms of a range of values (e.g. bitumen, slate). This arises where the range of values in the sample data is large, and/or the sample size is small. In these cases the data is represented here in terms of three scenarios: the upper and lower estimates, and the average (mean) of these.
Cements with a mixture of replacement fly ash or ground granulated blast furnace slag (GGBS) are also represented in the source documentation by a range of values. In this case, the range does not derive from data uncertainty, but, rather, represents the range in the proportion of fly ash or GGBS. As described above, these scenarios are represented here in terms of upper, lower and mean values for each percentage range.
The data for nylon carpet and carpet tiles is provided in the source documentation on the basis of area quantities (i.e. kg [CO2] per m2). This data and calculation basis is available here. The per kg data for these materials (i.e. kg [CO2] per kg) were derived from the per m2 data using the area density values (i.e. kg per m2) which are provided for each of the carpet types in the original source documentation.
Several other methodologies sourced from the ICE database are available. While this methodology deals with mass-based material quantities, material life cycle emissions can also be calculated on the basis of area, which is appropriate for materials such as paint, carpet, photovoltaic cells and roads. (Mass-based calculations are nevertheless available for paint and carpet in the present methodology).
In addition, there exist several methodologies which provide data and calculations specific to particular types of materials, for example concrete, timber (including biogenic CO2 emissions) and windows.
Details of the sources of data for the ICE database are also available.