Last month we reviewed embodied carbon, what it is, why it’s important, and how to reduce its impact in buildings. We also looked at how it is measured and documented, facilitating transparency in comparison of materials and products, and how that starts with life cycle assessment (LCA) and environmental product declarations (EPDs). Let’s build on that knowledge with a focus on how an LCA is conducted for a material and how the results are used to create an EPD.
How They Are Created and Why They Are Important
An LCA is a comprehensive accounting of the environmental impacts of a material, product or process, from “cradle” (material extraction and pre-processing) to “grave” (end-of-life, recycling or disposal), including the production, distribution and use stages in between. The analysis looks at the primary inputs, including raw materials, energy and water, and outputs, like solid waste, and pollution emitted to air and water. The environmental effects of these inputs and outputs are measured in impact categories:
- Global Warming Potential (GWP)–Greenhouse gas emission impacts, expressed as carbon dioxide equivalent emissions per unit of product (embodied carbon).
- Ozone Depletion Potential (ODP)–Stratospheric ozone layer thinning from emitted substances, like chlorofluorocarbons.
- Acidification Potential (AP)–Acidification of soils and water from gases such as nitrogen and sulphur oxides.
- Eutrophication Potential (EP)–Impact on aquatic life from nutrient releases (e.g., nitrogen or phosphor containing compounds) that feed algal blooms and deplete oxygen.
- Photochemical Ozone Creation Potential (POCP)–Photochemical ozone (smog) in the lower atmosphere from gas emission catalyzed by sunlight.
- Abiotic Depletion Potential–Elements (ADPE)–Depletion of non-fossil natural resources.
- Abiotic Depletion Potential–Fossil Fuels (ADPF)–Depletion of fossil fuel resources.
EPDs are central to the material transparency and embodied carbon initiatives of sustainable building professionals and contribute to requirements in major green building rating systems, including LEED and Living Building Challenge, so having an EPD can be a competitive advantage for a product.
Some European LCA standards also measure toxicity to humans and the environment. While there are various standards governing the creation of LCAs, the process generally starts with defining the goal of the exercise and the boundary for the analysis. The boundary is often defied as cradle to grave, accounting for the full life cycle, but sometimes is limited to a cradle-to-gate analysis, stopping where the finished product leaves the factory, when the range of assumptions for distribution, longevity of use and end-of-life are highly varied.
The next step is to conduct a life cycle inventory (LCI), identifying the material elements included in each life cycle stage. This is followed by an impact analysis that quantifies the environmental effects in each impact category during each stage within the boundary. Finally, an LCA includes interpretation, outlining what the results mean and potential opportunities to reduce impacts. An LCA is conducted using software tools like SimaPro and GaBi.
While there are several reasons a building material manufacturer might perform an LCA, one of the primary motivators is to create an EPD for each of its products. EPDs are central to the material transparency and embodied carbon initiatives of sustainable building professionals and contribute to requirements in major green building rating systems, including LEED and Living Building Challenge, so having an EPD can be a competitive advantage for a product.
An EPD is a voluntary declaration, independently verified and registered, that communicates transparent and comparable information about the life-cycle environmental impacts of a product. The creation and certification of an EPD is prescribed by the International Standards Organization (ISO) 14025 standard. The first step in creating an EPD is to prepare an LCA based on Product Category Rules (PCR). PCRs are documents that provide rules and requirements for developing an EPD for a specific product category (e.g., rollformed metal cladding). They are an important element of ISO 14025 because they enable transparency and comparability between EPDs for similar products. The creation of a PCR is typically commissioned by a trade organization and executed by a program operator, an organization accredited to develop PCRs and verify EPDs.
The results of an LCA are presented in a standardized format in a draft EPD. The prescribed content includes a description of the organization and product, identification of the PCR used, presentation of LCI and LCA data, and the scope and boundary. An EPD can be either industry-wide or product specific. Industry-wide EPDs are created by a collection of manufacturers, typically for standardized products (e.g., light-gauge metal framing) that vary little between manufacturers, while product specific EPDs are used for unique and proprietary products. The LEED Building Product Disclosure & Optimization credit places more value on product specific EPDs. Whole building life cycle assessments and the Embodied Carbon in Construction Calculator (EC3) tool both pull data from multiple EPDs to estimate the embodied carbon and other environmental impacts of entire buildings.
Generating an EPD is a very involved process, but they have real value for both manufacturers and specifiers. As discussed last month, the building industry’s response to the climate crisis is incomplete without significant reductions in embodied carbon. Limiting the environmental and climate impacts of buildings begins with measuring and transparently reporting the key indicators for individual materials. This allows architects and contractors to make informed material choices, but more importantly, it gives material producers the opportunity to show leadership in addressing climate change and to differentiate their products ahead of emerging mandates, including:
- The Buy Clean California mandate recently went into effect, setting embodied carbon limits for materials, including structural and reinforcing steel, for state-funded projects. Six other states may follow, and several major municipalities have adopted comparable purchasing requirements.
- A German steel producer recently announced a new “green steel” plant, operating on renewable hydrogen, with vehicle manufacturers as their customers, responding to consumer demands.
- The European Union recently proposed a “carbon border adjustment,” a form of carbon tax that would disadvantage imports with high embodied carbon.
Given these trends, prudent companies will want to stay ahead of the curve, inventory their environmental impacts and innovate on ways to reduce them, starting with LCAs and EPDs.
Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with over 30 years of experience in sustainable building design. He is a senior consultant with Intertek Building Science Solutions in Portland, Ore. To learn more, follow Scott on Twitter @alanscott_faia.