Over the past 20 years, the term sustainability has flirted with a buzzword status. There is agreement among many that the roots of development are in the United Nations (UN). In 1980, the UN produced the World Conservation Strategy1 which focused almost exclusively on environmental perspectives. However, in 1987, the UN produced the Brundtland Commission Report2 which started pivoting away from only an environmental focus to a more holistic focus. In the report, the Commission defined sustainability as meeting the needs of the present without compromising the ability of future generations to meet their own needs. However, it wasn’t until 2002, when the UN hosted the World Summit on Sustainable Development3 where the three pillars of sustainability were explicitly defined as economic, environmental and social. This write-up will provide a brief overview of the economic, environmental, and social pillars and will wrap up with a handful of examples of how they can apply to our roads.
The economic pillar of sustainability focuses on understanding how much a project costs in terms of dollars, and how to compare one project to another. A key component of the economic pillar is the life cycle, which includes materials, design, production, construction, use and end of life. There are four common tools available to quantify the economic pillar. First, a Life Cycle Cost Analysis4 (LCCA) incorporates both initial and discounted future costs. Second, leveraging present, future or annual worth provides flexibility of the concept of time in cost comparison. Third, the rate of return is the most common when issuing bonds for infrastructure projects. Fourth, the benefit/cost ratio is a popular service analysis technique. The LCCA is the most common tool used in the pavement industry.
The environmental pillar of sustainability focuses on understanding the impact of a project on the environment. While there are many different tools available, such as the Ecological Footprint, the Water Footprint and Planet Boundary, the most common tool is the Life Cycle Assessment (LCA). An LCA quantifies the material and energy flows going into a process and measures the waste and pollution flows coming out of the process. Materials can be virgin or recycled, and energy can come from renewable and nonrenewable fuel sources; while wastes can be hazardous or non-hazardous and can come in a gas form, a liquid form or a solid form. The wastes can be converted into ecological impact, using concepts such as ozone layer depletion, acidification, smog and eutrophication, which is the process of gradually increasing plant nutrients in an aging aquatic ecosystem. Once an LCA is performed, a Product Category Rule is written, which provides rules on interpreting an LCA. Finally, an Environmental Product Declaration (EPD) is produced based on the LCA and PCR. An EPD is similar to nutrition information on the side of a cereal box, but instead of a health impact, an EPD summarizes the environmental impact.
The social pillar of sustainability is much more difficult to quantify, but there have been significant strides in the past 10 years to do so. Like the concept of sustainability itself, the UN has taken a large role and has produced many documents related to the social pillar revolving around poverty, governance, health, education, inequality, opportunity barriers and other social issues. In addition to the work at the UN, the Human Development Index attempts to capture human well-being beyond the typical economic measures by measuring life span, life health, knowledge and a decent standard of living. Another tool, the Social Impact Assessment, can be seen as a Safety Data Sheet for the social pillar and captures five aspects of the social pillar: life cycle, culture, community, quality of life and health.
There are countless examples in published literature on various facets of these three pillars. For example, Braham (2016)5 found that Full Depth Reclamation was economically competitive with traditional maintenance and rehabilitation techniques (mill and fill or remove and replace), often costing less than a mill and fill strategy but providing a significant structural gain. Poor and Braham (2022)6 found that using a blend of treatments (fog seal, micro surfacing, thin HMA overlay, chip seal + fog seal and Cold In-Place Recycling) produced an estimated savings of ∼500,000 GJ of energy and ∼35,000 tonnes of greenhouse gas emissions compared to a traditional mill and fill strategy. While these are just two examples, they do indicate how using more tools in the toolbox can reduce both the economic and environmental impact of caring for our roads, and that being proactive rather than reactive saves money and reduces emissions and energy use.
References
- UN World Conservation Strategy (1980) https://portals.iucn.org/library/efiles/documents/wcs-004.pdf
- UN Brundtland Commission Report (1987) https://sustainabledevelopment.un.org/content/documents/5987our-common-future.pdf
- World Summit on Sustainable Development https://www.un.org/en/conferences/environment/johannesburg2002
- Life-Cycle Cost Analysis in Pavement Design (1998) (https://www.fhwa.dot.gov/pavement/lcca/013017.pdf)
- Braham (2016) https://journals.sagepub.com/doi/10.3141/2573-07
- Poor and Braham (2022) https://www.astm.org/jte20220272.html
Dr. Andrew Braham graduated from the University of Wisconsin with his B.S. and M.S., and from the University of Illinois with his Ph.D. He worked with Koch Materials Company for two and a half years, and performed a post-doc at Southeast University in Nanjing, China. He is currently a Professor in the Civil Engineering Department at the University of Arkansas, where his teaching and research focus is on asphalt emulsions, pavement maintenance and rehabilitation, and sustainability. You can find out more about Dr. Braham at www.andrewbraham.com
Written by Andrew Braham, Ph.D., P.E.
Aug 21, 2023
