Concrete Compass: Carbon data for project LCA
Increasingly, embodied carbon assessments are required as part of the procurement and design process, whether for early-stage design, the technical design and construction stage, or post completion of the building. This compass aims to help navigate to resources to select the most appropriate and highest quality carbon data for concrete at different stages in the design process.
Selection of carbon data at different design stages
Standards and guidance, such as EN 15941, RICS Whole Life Carbon Assessment (WLCA) standard and IStructE's How to Calculate Embodied Carbon, address the choice of construction product data for building level carbon assessments.
The first-line choice of carbon data will depend upon the design stage at which the embodied carbon calculation is being carried out. At the early design stage, ideally UK-specific sector EPDs should be used. The MPA Sector EPDs provide independently-verified carbon baseline values for different concretes and concrete products that can be used to inform design choices, before a supplier has been appointed. Later, at the technical design and construction, and post-completion phases, manufacturer specific EPDs can be used, where available.
In the absence of an appropriate sector or manufacturer EPD, the following hierarchy can be applied to select the best alternative carbon data source at each design stage. Alternative carbon data sources can also be considered if suitable EPDs are not available.
The figure above provides a hierarchy of carbon data sources for concrete and concrete products at different design stages. It should be noted that post-completion phase carbon data may differ from embodied carbon estimates provided by suppliers at the technical design and construction stage due to essential evolution in requirements of the concrete as the project, its details and programme progresses.
Data quality
Data quality is key to the accuracy of any life cycle assessment. European standard EN 15941 provides guidance on the selection of data for EPDs and LCA. Data chosen should be representative of the concrete to be used and selected based on the answers to the following questions:
Time - when the data was collected and for how long can it be assumed to remain valid. The data quality will be ‘very good’ if valid EPDs are used. The date of publication and validity are stated on the front cover of an EPD.
Geography - is the data specific to the country of manufacture or is it averaged over a wider regional or global area? The data quality will be ‘very good’ if a UK-specific EPD is used for a UK project. In the absence of a UK-specific EPD, use an EPD for a similar geographic context, or a larger region, e.g. EU for the UK. EPDs from a completely different geography (e.g. America or Asia) will have ‘poor’ data quality. This issue is especially important for concrete since it remains overwhelmingly a domestically-procured product. For example, EC3 is a buildings and materials carbon database based in the USA. EPD standards in North America differ from those in Europe, therefore many of the EPDs are not suitable for UK use.
Technology - is the data based on the same manufacturing processes or are there variations? E.g. in energy efficiency.
Other aspects of the data quality to be considered are:
Precision – what is the variability of the data, particularly if it is gathered over many production sites? Sector EPDs state the variability of the data.
Completeness – are there gaps in the data? EPDs state whether input cut-offs have been applied. Cut-offs should total less than 5% of the energy usage and mass.
Consistency of the methodology used in data gathering.
Data sources should be traceable and appropriate to use of the data.
Gross vs net - MPA cement and concrete currently report data in terms of ‘gross’ CO2 emissions, i.e. including combustion of both fossil and waste-derived fuels (also called ‘alternative’ or ‘secondary’ fuels). However, practice varies both within the UK and internationally. Users should check whether carbon data is reported as ‘gross’ CO2emissions or as ‘net’ CO2 emissions, i.e. excluding CO2 emissions from the combustion of waste-derived fuels. The difference between ‘net’ and ‘gross’ CO2 values depends upon the specific fuel mix and the proportion of waste-derived fuels used at an individual cement plant. On average, for UK-manufactured cement, ‘gross’ CO2 emissions values are 10.25% higher than ‘net’ values. ‘Gross’ CO2 values can be around 25% higher than ‘net’ CO2 values for cement plants that use a high proportion of waste-derived fuels.
Clearly, there may be overlaps between these different aspects of data quality.
Adjustment factors
Especially at the early design stage, there will be some uncertainty associated with the choice of input data. This uncertainty is quantified within the MPA sector EPDs. For cement and C28/35 ready mixed concrete the uncertainty is less than <±10%. For precast products the MPA sector EPDs have a wider range of variability, e.g., ±15% to ±20% for precast flooring. Where sector EPDs are not available, adjustment factors may be included, for example the RICS WLCA uncertainty factor.
Focus on: Environmental Product Declarations (EPDs)
An Environmental Product Declaration, or EPD, provides comparable, transparent data on the environmental impacts of a construction product. All EPDs must be independently verified by an accredited third-party prior to registration with a recognised EPD programme operator (such as EPD International or EPD Hub).
EPDs are based on a life cycle assessment (LCA) over the full product value chain, following the methodology set out in international standards. EN 15804 is the European standard for construction product EPDs. (Other regions, notably North America, EPDs follow the ISO 21930 standard). There are also complementary product category rules to apply EN 15804 to different categories of construction products, such as EN 16908 for cement and EN 16757 for concrete. Many EPD programme operators are also members of the umbrella association, Eco Platform and operate to its rules and guidelines.
Within an EPD, the climate change impact from carbon dioxide and other greenhouse gas emissions and removals is measured by the Global Warming Potential (GWP) indicator, which, according to the 2019 update to EN 15804, is sub-divided into three categories: fossil carbon, biogenic carbon, and land use and land use change. As well as carbon data, EPDs quantify a range of other environmental impact indicators, such as the depletion of stratospheric ozone, and resource use. Each impact indicator is broken down into modules and sub-modules corresponding to stages of the construction product life cycle. Modules A1-A5 cover material extraction, manufacturing and construction; modules B1-B7 use of the product in the building; and modules C1-C4 demolition and deconstruction at the end of life of the building. Finally, potential for recovery and reuse is reported in module D. Construction product EPDs should declare at least modules A1-A3, C1-C4 and D. (Cement is one of the few exceptions to this rule. It is chemically bound into the concrete and cannot be physically separated out at the end of the building life cycle.)
Focus on: EPDs for concrete
There are a number of sources that provide third-party verified EPDs for cement and concrete.
The international standard governing data quality for EPDs and building LCA, EN 15941, distinguishes between two main types of EPD: manufacturer specific EPD, and collective EPDs that average data over more than one manufacturer - such as the sector EPDs produced by MPA. Within each type, there is also a subtype hierarchy to describe whether the EPD is for a specific product, an average product or a typical representative product (i.e., a typical product which is representative of a certain product group), and - for manufacturer specific EPD only – whether the EPD is for one plant or an average over several of the manufacturer’s plants.
Figure 2: Types of EPD (adapted from EN 15941)
MPA Sector EPDs
MPA has published a number of sector EPDs for representative cement, C28/35 ready mixed concrete and precast concrete products. Full details and links are available here. These are based on data related to UK based manufacturing and are thus most appropriate for projects based in the UK.
Concrete Manufacturer EPDs
Many MPA members have published EPDs for their own products. Some manufacturers are now able to produce EPDs for ready-mixed concrete on demand.
Manufacturer EPDs can be requested directly from the manufacturer or found by searching in one of the following EPD databases.
- Eco-Portal is the central database for EPDs published through EPD schemes which are members of the Eco-Platform (a non-profit association for EPD schemes worldwide). Initially the database focussed on EPDs that comply with the European standard EN 15804, although it has since extended globally. This is a good starting point to search for EPDs for UK projects.
- EPD Hub is a relatively new construction EPD certification scheme, associated with the One Click LCA software, that verifies and certifies EPDs to EN 15804. The EPD Hub EPD Library includes EPDs from several UK concrete manufacturers, for both ready-mixed concrete and precast concrete products.
If third-party verified EPDs are not available, other sources of generic carbon data can be used to calculate the embodied carbon of concrete building elements, especially at the early design stage. Note that some of these data sources only provide upfront embodied carbon data, corresponding to EPD modules A1-A3, rather than the full suite of environmental indicators over the whole product lifecycle required in EPDs.
EPD background LCA datasets
Ecoinvent and Sphera Managed LCA content (formerly GaBi) are background LCA datasets, each with ca. 20,000 datapoints, from multiple sources, describing the environmental impacts of different products and processes. They form the basis of almost all EPD and LCA studies and software worldwide. Direct access to the database requires a licence. Alternatively, most EPD and LCA tools allow the user to interrogate individual datapoints.
Built Environment Carbon Database (BECD)
Launched in 2023, the BECD is designed as a free-to-use repository of product LCA data, both EPDs and other generic data, that fully complies with the RICS Professional Standard on Whole Life Carbon Assessment (2023). (It also contains whole-life carbon assessments of built assets). However, it is currently incomplete and the EPD descriptions do not align with EN 15941 (for example, EN 15941 is clear that the term ‘generic EPD’ should no longer be used).
ICE database
The ICE Database published by Circular Ecology is well-known as it is one of the oldest databases in the UK, first published in 2008. It primarily contains generic carbon data and so should only be used when EPDs or other more recent industry data are not available.
Manufacturer self-declared carbon data
Many ready-mixed concrete manufacturers have software tools that follow the EN 15804 standard or another defined methodology. Such tools can be used to create self-declared carbon data - on demand - that complies to the ISO 14021 standard for self-declared environmental claims. Such data has the advantage of being product specific, e.g., using the exact batch mix, and can provide accurate carbon data in the technical design and construction or post completion stages, if no EPD is available.
As already noted, some manufacturers can create EPDs on demand for ready-mixed concrete.
Focus on: Benchmarks
LCCG market benchmark
The Embodied Carbon of Concrete: Market Benchmark document, published by The Concrete Centre on behalf the Lower Carbon Concrete Group (LCCG), is based on upfront (A1-A3) embodied carbon data for all normal weight ready-mixed concrete produced in the UK by MPA members in the previous calendar year, supplemented by data from contractors and independent concrete suppliers. The data is based on gross CO2 emissions, calculated to EN 15804. Note that the current benchmark excludes any precast concrete products. The latest Market Benchmark document is available here.
For further information on benchmarking schemes refer to Making the Grade article, Concrete Futures, spring 2024.
Other carbon sources
As interest in carbon data continues to increase, it is difficult to provide a comprehensive list of carbon data sources. The following is a brief description of data sources which may be familiar but are not included in the data selection hierarchy.
MPA Fact Sheet 18 Embodied CO2e of UK cements
Fact Sheet 18 is a well-known MPA publication that provides embodied CO2e data for UK cement, additions and cementitious material, together with embodied carbon ranges for factory made cements and combinations commonly available in the UK. First published in 2011 (before EPDs had been created for the mineral products and materials referenced), the latest version was published in 2025. It is not included in the hierarchy as it provides data for cements rather than concrete, but it does indicate how supplementary cementitious materials can be used to reduce embodied carbon. View the factsheet here.
This information provides the base data for The Concrete Centre's TCC-BS 8500 tool which simplifies the specification of concrete to BS 8500 by allowing the user to input the exposure classes, design strength and cover.
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