This resource aims to guide policymakers and procurement professionals in collecting high-quality embodied carbon data. Policies targeting the reduction of carbon emissions associated with building products require the disclosure of embodied carbon data to inform policies and verify whether reduction targets or incentive requirements have been met.
Environmental product declarations (EPDs) are independently-verified documents based on international standards that report the environmental impacts of a product. These declarations can be used to track supply chain-specific product data and compare products if the products are functionally equivalent and have aligned scopes.
Measuring embodied carbon requires an LCA
To understand the embodied carbon or supply chain carbon emissions of a product, you need a life cycle assessment (LCA) of the product. LCA is a method for quantifying the environmental impacts of a product throughout its life cycle that can be applied to any product. The primary stages include:
- Product (A1-A3), which includes extraction and upstream processing of materials, transportation, and manufacturing impacts
- Construction (A4-A5), which includes transport to the site
- Use (B), which includes maintenance and replacement
- End-of-life (C), which including demolition and disassembly as well as waste processing and transportation
- Beyond the life cycle (D), which includes potential benefits from reuse, recycling, and/or energy recovery
Greenhouse gas emissions, including carbon dioxide, are added up over the product’s life cycle and reported as global warming potential (GWP). GWP is expressed in carbon dioxide equivalents (CO2e), and is an agreed-upon definition for expressing a product’s carbon footprint.
Environmental Product Declarations (EPDs) are the right tool for disclosure and transparency
To be effective, an agreed-upon methodology for measuring and calculating the embodied carbon of products must be used consistently. In the building industry, EPDs are this agreed-upon tool and methodology.
An EPD is a “nutrition label” for a product’s environmental footprint. Just like with a food nutrition label, you need to know what you are looking for to know whether a product is healthy: looking at an EPD on its own won’t tell you whether or not a product is good for the environment.
EPDs provide environmental data based on a life cycle assessment (LCA) that was independently verified in accordance with ISO 14040 and ISO 14044. EPDs may report a variety of life cycle impacts in addition to global warming potential (GWP), such as acidification, eutrophication, ozone depletion, and smog formation. EPDs also typically include additional manufacturer and product data, such as ingredients, manufacturing processes and locations, and resource use.
Figure 1. Flow of data from the supply chain to an EPD and project submittal. (*) indicates areas where specificity and other minimum data requirements are set by the Product Category Rule. Policies can add requirements to strengthen data reporting.