Inventory of Carbon & Energy methodology for concrete

Contents

Summary

This methodology represents embodied energy, carbon dioxide (CO2) and CO2e emissions associated with the use of concrete. 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

Emissions model

The methodology is based on factors which describe the quantities of energy and CO2 which are 'embodied' within unit quantities of concrete. By multiplying a quantity of concrete by these factors, an estimate of the embodied energy and emissions associated with that quantity can be calculated.

In addition, the methodology enables the calculation of energy and CO2 emissions embodied in reinforcing steel or the precasting process where appropriate. These are enabled by additional factors which are combined with the baseline concrete factors in order to derive new per unit concrete factors for scenarios which use reinforced or precast concrete. The additional factor for reinforcing steel is proportionate to the density of steel contained within each unit of concrete.

Model data

Embodied energy and emissions vary between different types of concrete, owing to, among other things differences in composition. This methodology represents 82 different concrete types, each differentiated by their type (e.g. block, standard ready mix, nominal proportions) subtype (e.g. 10 MPa compressive strength, 1:2.5:5 cement:sand:aggregate, PAV1) descriptors and the details of any replacement material used (e.g. 25% blast furnace slag).

Each specific type of concrete 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)

For some types, unit CO2e emissions are not explicitly defined. 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.

Additional values are provided for determining embodied emissions and energy associated with reinforcing steel and precasting of any concrete type:

  • embodied energy per unit mass for precasting (MJ/kg)
  • embodied CO2 per unit mass for precasting (kg/kg)
  • embodied energy per unit mass per unit density of steel ((MJ/kg) / (kg/m3))
  • embodied CO2 per unit mass per unit density of steel ((kg/kg) / (kg/m3))

Activity data required

Embodied energy and emissions are directly proportionate to the mass of concrete used, which therefore must be available in order to calculate. If requiring the impact of reinforcing steel to be included, the density of the steel (i.e. mass of steel per volume of cement) must also be specified. If the concrete under consideration is precast, this must be declared also.

Calculation and results

Embodied energy and emissions are calculated by multiplying the specified quantity of concrete used by the available factors. Any additional effect of reinforcing steel or precasting are also incorporated. Up to three values are returned representing the embodied energy, and CO2 or CO2e emissions attributable to the specified quantity of concrete (and steel).


Additional information

Autoclaved aerated blocks

In the case of Autoclaved aerated concrete blocks, the published data for embodied energy and/or CO2(e) is provided in terms of a range of values. As such, the data is represented here in terms of three scenarios: the upper and lower estimates, and the average (mean) of these.

Reinforcing steel associated factors

The additional factors for embodied energy and CO2 emissions associated with reinforcing steel are quoted in the ICE source documentation in relation to a unit of 100 kg [steel] per m3 [concrete]. These factors are represented here on a simpler kg/m3 basis and are therefore scaled by a factor of 100.


Related methodologies

Several other methodologies sourced from the ICE database are available. The bulk of the ICE database represents several hundred distinct materials, emissions and energy for which can be calculated on the basis of mass or area.

In addition, there exist several methodologies which provide data and calculations specific to particular types of materials: timber (including biogenic CO2 emissions) and windows.

Details of the sources of data for the ICE database are also available.


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