The Impact of Shipping:
Beyond the Regional Radius

Image courtesy of Polaris Materials Corporation

Specifying materials extracted, manufactured, or assembled in proximity to a project site can have many benefits, including supporting the local economy and minimizing the impacts due to transporting building materials. Over the last 20 years, LEED has encouraged design teams to focus on selecting regional materials and in turn, design and construction teams are now adept at documenting a project’s regional content.

However, as we become more aware of the importance and urgency of embodied carbon, we must look past a prescriptive approach based only on a regional radius to better understand what products result in the lowest total embodied carbon. While regional materials boost local economies and minimize the impacts associated with shipping and transportation, teams must assess possible tradeoffs between regional production and distant suppliers that provide higher quality products or processes.

The impact of shipping construction materials is most frequently proportional to weight and not all shipping modes produce the same environmental impact. For example, transporting one ton by truck emits nearly 10 times as the CO2 as transporting on a barge. This graph shows the effects for each transportation method available in Tally. This leads to the question, is there a case where materials from greater distances result in a net carbon benefit?

Image courtesy of Polaris Materials Corporation

We recently faced this question when performing a whole building life-cycle assessment (WBLCA) for City of Hope, a medical office building in Duarte, California. The project, and concrete framed medical office building, used WBLCA to minimize embodied carbon and to achieve the LEED WBLCA credit. Our initial WBLCA found that the concrete frame was responsible for the majority of the embodied carbon in the WBLCA scope.

While using supplementary cementitious materials (SCMs) is a typical strategy to minimize embodied carbon, a fly ash shortage and logistical concerns meant that the team must also consider other strategies. To decrease the cement content in the high early strength mixes, the concrete supplier submitted a mix design that included coarse aggregate from British Columbia, a high-quality aggregate with a high compressive strength.

While a local quarry for concrete aggregate is just over two miles from the project site and the team examined whether using a coarse aggregate source from Vancouver, British Columbia— nearly 1300 miles away—could result in an improved environmental impact. Our analysis considered both the transportation impacts and savings from reduced cement content. The use of this aggregate, in lieu of the lower-quality aggregate common in California and neighboring states, reduced the cement quantity required to reach a high early strength for the post-tensioned concrete floor slabs without the use of SCMs.

This illustrates the need for project teams to ask suppliers for material specific product data through producer specific EPDs (Environmental Product Declarations). While specifying local materials may provide benefits, teams seeking to minimize embodied carbon must make more robust quantitative comparisons that consider not only transportation impacts, but also any impact reductions a non-regional supplier may achieve through manufacturing or procurement optimization.