Understanding Embodied Carbon
Embodied carbon calculator refers to the calculation of the carbon dioxide (CO₂) emissions associated with materials and construction processes throughout the entire lifecycle of a building or infrastructure. This includes all CO₂ created during the manufacturing of building materials (material extraction, transport to the manufacturer, manufacturing), transporting those materials to the job site, and the construction practices used.
Essentially, embodied carbon is the carbon footprint of a building or infrastructure project before it becomes operational. It also accounts for the CO₂ produced during the maintenance of the building and its eventual demolition, transportation of waste, and recycling.
Distinction Between Embodied Carbon and Operational Carbon
Embodied carbon is distinct from operational carbon—the carbon that comes from energy, heat, lighting, etc., during the building’s use. Advances in reducing operational carbon have highlighted that embodied carbon is becoming a larger portion of a building’s overall carbon footprint. According to recent data from the World Green Building Council, the focus on embodied carbon is critical as the world’s greenhouse gas emissions from construction activities are substantial.
Importance of Embodied Carbon in Construction
The global building stock is expected to double by 2060, equivalent to adding an entire New York City to the planet every month for the next 40 years. This rapid growth necessitates a significant focus on embodied carbon. For instance, cement, a key ingredient in concrete, is a major emitter of CO₂ in the built environment. Cement production alone contributes approximately 7% of the world’s CO₂ emissions, making it the largest contributor to embodied carbon in the built environment.
Tackling Embodied Carbon
Embodied carbon is anticipated to account for nearly 50% of the overall carbon footprint of new construction from now until 2050. To address this, several organizations, including Architecture 2030, Structural Engineers 2050 Challenge (SE2050), the Carbon Leadership Forum, and the World Green Building Council, are committed to eliminating embodied carbon from buildings by 2050. A key strategy in reducing embodied carbon is to modify how concrete is specified, shifting towards performance-based concrete specifications.
A Guide to Calculating Embodied Carbon
Structural engineers play a crucial role in reducing embodied carbon by incorporating embodied carbon calculations at every design stage. This enables engineers to target carbon reductions through material selection, specification, efficiency, and reuse. The Institution of Structural Engineers has developed a guide titled “How to Calculate Embodied Carbon,” which offers a structured approach to these calculations.
Lifecycle Modules and Stages
Understanding lifecycle stages, in line with BS EN 15978 (2011) and BS EN 15804 (2019), is essential for calculating embodied carbon. These standards define the amount of carbon released at different stages of a material or product’s life. The fundamental principle of an embodied carbon calculation is to multiply the quantity of each material or product by a carbon factor (measured in kgCO₂e per kg of material) for each lifecycle module considered.
Calculating Quantities and Carbon Factors
Material quantities can be estimated in various ways depending on the design stage and available tools. Early design stages may rely on estimates based on experience or quick calculations, while later stages might use structural analysis or building information models (BIM) for more accurate quantities. The carbon factors used in these calculations should be as accurate as possible, derived from sources like environmental product declarations (EPDs) from manufacturers.
The Role of Embodied Carbon Calculators
Using an embodied carbon calculator is critical for making informed decisions that reduce the carbon footprint of construction projects. These calculators allow for the quick estimation of the embodied carbon of a structure even at the concept stage, enabling quantitative comparisons of design options alongside other components of sustainable design.
Embodied Carbon in Different Materials
Concrete
The embodied carbon of concrete varies significantly depending on its composition and manufacturing process. Factors such as the cement content and the percentage of Portland cement (PC) replacement influence the carbon factor. For instance, the embodied carbon factor for concrete can range widely based on these variables.
Steel
Steel is another major contributor to embodied carbon. The carbon factor for steel depends on the recycled content and the production method. For example, UK-produced rebar has a different embodied carbon factor compared to rebar produced in other regions with different manufacturing practices.
Timber
Timber presents an interesting case as it can sequester carbon, effectively removing carbon dioxide from the atmosphere through photosynthesis and storing it within the wood. This sequestration must be accounted for in embodied carbon calculations, particularly when reporting carbon for different lifecycle stages.
The Benefits of Using Embodied Carbon Calculators
Employing an embodied carbon calculator offers several benefits for the construction industry:
- Informed Decisions: By understanding the embodied carbon emissions of different materials, project teams can make better choices to minimize the carbon footprint.
- Early Design Stage Interventions: Calculating embodied carbon early in the design stage allows for adjustments that can significantly reduce overall emissions.
- Compliance and Reporting: Many sustainability frameworks and regulations now require carbon accounting for building projects. Using an embodied carbon calculator ensures compliance with these standards.
- Supply Chain Optimization: Identifying high-carbon materials enables better engagement with the supply chain to source low-carbon alternatives.
Transport and Construction Factors
Transport Emissions
The transport of materials from the manufacturer to the construction site contributes to embodied carbon. The embodied carbon factor for transport depends on the mode of transport (road, sea, rail, air) and the distance traveled. For example, locally manufactured materials have a lower transport carbon factor compared to those transported from overseas.
Construction Site Activities
Emissions from construction site activities, including the use of machinery and site offices, also contribute to the embodied carbon. These emissions can be estimated from on-site electricity consumption and fuel use and should be monitored throughout the construction process.
Strategies for Reducing Embodied Carbon
- Material Selection: Opt for materials with lower embodied carbon values. For instance, using recycled steel or concrete with lower cement content can significantly reduce emissions.
- Efficient Design: Design buildings to use materials more efficiently, reducing waste and optimizing structural elements.
- Local Sourcing: Minimize transportation emissions by sourcing materials locally.
- Innovative Materials: Explore alternative materials like cross-laminated timber (CLT), which can sequester carbon and reduce overall emissions.
- Recycling and Reuse: Incorporate recycled materials and plan for the reuse of building components at the end of their life.
To Summarise
Addressing the embodied carbon in construction is essential for mitigating climate change and reducing the global greenhouse gas emissions from the built environment. By using tools like the embodied carbon calculator and adhering to standards and guidelines, engineers and architects can make informed decisions that significantly reduce the carbon footprint of their projects. Embracing these practices not only helps combat global warming but also leads to more sustainable and efficient construction processes, benefiting the environment and society as a whole.