VAASPHALT.ORG 21 The EPD contains data specific to a mix, organized into tables. Table 4 of an EPD for asphalt mixture quantifies a set of environmental impact indicators associated with raw material extraction and processing (A1), transporting those materials to the asphalt plant (A2), and plant operations (A3). The indicator that most people are focused on is global warming potential (GWP-100), which measures greenhouse gas (GHG) emissions as reported in carbon dioxide equivalents (CO2 Equiv.). The “100” refers to a 100-year time scale, which characterizes how short-lived GHG compounds, such as methane, may impact global warming over 100 years after being emitted. Other indicators provide information about emissions that cause acid rain, smog, and eutrophication (nutrient loading of water bodies), among others. Resource Use Indicators, shown in Table 5 of an EPD for asphalt mixture, quantify information related to the energy and materials used during the three stages of the asphalt mix production life cycle. A variety of factors break down energy. Some of these, such as renewable versus non-renewable, are fairly straightforward. Recognizing that some materials, such as asphalt binder, are combustible and have energy content, energy is also broken down into energy used as fuel versus energy used as a material. Energy is further broken down into primary or “first use” energy and secondary or “recycled” energy used as a fuel, (i.e., combusting used oil as a burner fuel). Table 5 also shows the total secondary material content as well as the consumption of fresh water. What Are the Requirements? For EPDs, a set of Product Category Rules (PCR) were established based on the expertise of a group NAPA assembled to identify how energy and other metrics would be assessed. For instance, the PCR for asphalt mixtures had to adhere to the International Organization for Standardization (ISO) Standard 14025 and ISO Standard 21930. Once developed, PCRs undergo a public comment period and are then peer-reviewed and approved by an additional panel of experts. Numerous data sets are necessary for the PCR for asphalt mixtures. Data provided by the mix producer, referred to as “primary data,” include information about asphalt plant operations and materials used in the mix. These data sets include the amount of fuel a plant uses over a calendar year, the amount of electricity, the volume of water, the source of aggregates and asphalt, and the haul distances from the raw material sources to the asphalt plant. The EPD program also relies on background data to quantify the environmental impacts associated with the upstream manufacturing of raw materials. Currently, aggregates and asphalt binders do not have an EPD for each product, such as a #8 or #78 stone or PG 64S-22 or PG 64E-22 binders. Therefore, industry averages are used until those PCRs, and the resulting verified EPDs for each unique material, are developed. NAPA has also worked on a software program to simplify EPD development. NAPA and third-party vendor WAP Sustainability launched the Emerald Eco-Label program, which has since been independently verified and is highly respected among industry, agencies, and life cycle assessment (LCA) practitioners due to its thoroughness and ease of use. What Have We Learned from EPDs? As with any new process, there are many lessons learned. The biggest lessons from the creation of EPDs by asphalt contractors have been tied to the production processes or the “cradle to gate” portion of the LCA process. Within this are the extractional upstream production of the input materials (i.e., aggregates, binder, reclaimed asphalt, additives, etc.), the transport of the materials △ continued from page 19 Cradle-to-Gate Transport (A2) Materials (A1) End of Life (C1–C4) Maintenance & Rehabilitation (B2–B5) Use (B1, B6, B7) Construction (A4–A5) Production (A3) Figure 4. Life Cycle Diagram continues on page 22 △ CAN YOU SPELL EPD? While an EPD seems simple on the surface, no two asphalt mixes, plants, or companies are the same. Each one has unique characteristics. So, the question often asked is how can two mixes be compared if nothing is exactly the same?
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