Sustainable Engineering: The Future of Structural Design

Structural engineers face significant challenges in the 21 st century and among them, global environmental challenges must be a priority for our profession. On a planet with finite natural resources and an ever-growing built environment, engineers of the future must consider the environmental, economic, and social sustainability of structural design. To achieve a more sustainable built environment, engineers must be involved at every stage of the process. To address the broad issue of sustainability for structural engineers, this paper is divided into three sections: 1) Global environmental impact: The trends in steel and concrete consumption worldwide illustrate the growing environmental impact of structural design. In particular, the emissions of greenhouse gases due to structural materials are a primary global concern that all structural engineers should consider. 2) Solutions for today: There are many steps that each structural engineer can take to mitigate the environmental impact of structural design. Furthermore, there is growing demand for engineers who are knowledgeable of environmental issues in construction. This section presents several options that are available today for engineers interested in reducing environmental impacts. Case studies will illustrate examples of more sustainable structural design. 3) Challenges for the future: Although short-term solutions exist to reduce the environmental impact of construction, there are significant long-term challenges that we must address as a profession. By facing these challenges, we can take a leadership role in matters of vital global importance. In summary, the paper identifies the global sustainability challenges facing our profession and suggests possible solutions. The conclusion is that structural engineering has an enormous global environmental impact and our profession should work harder to offer solutions to society. Working for a more sustainable built environment is in the best interest of our profession as well as the interest of future generations. Copyright ASCE 2005 Structures 2005 Downloaded 10 Oct 2008 to 128.95.45.136. Redistribution subject to ASCE license or copyright; see http://www.ascelibrary.org/ 2 Global Environmental Impact On a planet with finite natural resources, the human population is growing and the rate of resource consumption per person is growing. This cannot continue indefinitely. In 1974, a landmark study by an interdisciplinary research group at MIT illustrated the various global scenarios that may occur depending on a range of possible technological, economic, and social assumptions (Meadows et al. 1974). Almost all of the possible scenarios predicted a collapse of natural resources followed by a collapse of human populations and decreased quality of life. Recently, a 30-year update reconfirmed the key conclusions of this study and illustrated the grave challenges facing global society in the future (Meadows et al. 2004). Increasing greenhouse gas levels, rising global temperatures, rising sea levels, and dramatic resource depletion have all occurred at increasing rates in the last 30 years. The growing need to address these challenges has become more accepted in the last decade and civil engineers have begun to play an important role. Since the 1987 Brundtland report defined sustainable development as meeting “the needs of the present without compromising the ability of future generations to meet their own needs,” the concept of sustainability has become an ethical standard and a goal for both government and industry (Brundtland 1987). Though civil engineers have not provided global leadership on this issue in recent decades, it is clear that the profession of civil engineering will play an integral role in achieving more sustainable development in the future (ASCE 2001). Over the last 200 hundred years, the definition of civil engineering has evolved from “directing the great sources of power in Nature for the use and convenience of Man” (Chrimes 1991) to a more recent definition that “Civil engineers are the custodians of the built and natural environment” (Agenda 2003). This shift illustrates the fundamental change in the relationship between engineers and the natural world. Man and nature are not separate entities. Engineers today must design for a planet with limited natural resources, complex problems with no clear answers, and increasing environmental concerns. As a testament to the growing awareness of sustainability for structural engineers, the International Association of Bridge and Structural Engineers (IABSE) dedicated a recent issue of Structural Engineering International to sustainable engineering design. In particular, the emissions of greenhouse gases due to structural materials are a primary global concern that all structural engineers should consider. The trends in steel and concrete consumption worldwide demonstrate the growing environmental impact of structural design, as illustrated in Figure 1. The production of Portland cement has doubled in less than 30 years, and this exponential growth is expected to continue well into the next century (Chaturvedi and Ochsendorf 2004). Furthermore, each ton of cement is responsible for approximately one ton of CO2 emissions and the cement industry alone contributes about 7% of global CO2 emissions. 2 2 There is some debate about the contribution of cement production, with estimates ranging from 5% to 10% of total global CO2 emissions. Copyright ASCE 2005 Structures 2005 Downloaded 10 Oct 2008 to 128.95.45.136. Redistribution subject to ASCE license or copyright; see http://www.ascelibrary.org/ 3 Figure 1: World production of cement and steel (Chaturvedi and Ochsendorf 2004) Governments around the world are seeking to reduce CO2 emissions in an effort to limit global warming. Many governments aim to go well beyond the goals of the Kyoto Protocol; for example, the United Kingdom has pledged to reduce CO2 emissions by 60% by the year 2050. The construction industry and the built environment are responsible for a large percentage of total global CO2 emissions, and therefore efforts to reduce global carbon emissions will require a strong emphasis on improving the sustainability of civil engineering.