According to the Society of Environmental Toxicology and Chemistry, life cycle analysis (LCA) is defined as "an objective process to evaluate the environmental burdens associated with a product, process, or activity by identifying energy and materials used and wastes released to the environment, and to evaluate and implement opportunities to affect environmental improvements."[1]

By breaking down the impacts of each system component across its entire life, LCA provides insights as to which components or processes create the most detriment to the environment. These insights can be used to target “hotspots,” or aspects of the system to target for maximum sustainability gains, as well as evaluate the efficiency or misplacement of existing sustainability efforts. Figure 1 illustrates the comprehensive nature of LCA.

LCA building.jpg
Figure 1: Illustration of life cycle analysis for a building.


History


LCA was developed in the United States in the 1960s by industrial ecologists, chemists, and chemical engineers seeking to understand and reduce the impact of manufacturing processes.[2] In particular, the basis for LCA was set in 1969 when researchers for the Coca-Cola Company explored differences in beverage containers to see the differences in consumption of fuels and raw materials as well as the environmental impacts of the manufacturing processes.[3]

During the late 1970s through 80s, hazardous waste management overshadowed LCA.[4] However, by the late 1980s, LCA came back to the forefront of environmental analysis tools.[5] In fact, by 1991, industrial marketing made so much dubious use of LCA that it provoked a need for clear, standardized, non-deceptive methods and communication.[6] Consequently, from 1997 through 2006, the International Organization for Standardization (ISO) developed LCA standards under the ISO 140000 series.[7]

In 2002, the United Nations Environment Programme (UNEP) partnered with the Society of Environmental Toxicology and Chemistry (SETAC) to launch the Life Cycle Initiative.[8] A three-pronged tool to support LCA, the Life Cycle Initiative offers training programs and communication venues, provides access to high quality life cycle data, and facilitates communication among LCA experts to develop widely accepted recommendations.[9]

The Life Cycle Analysis Process


The standard for the LCA process is ISO 14044, which prescribes four main steps as shown in Figure 2:[10]
LCA process 4 steps.png
Figure 2: LCA process.

  1. Goal and Scope Definition – “What are we trying to learn?”
  2. Life Cycle Inventory – “What is embedded in the product?”
  3. Life Cycle Impact Assessment – “What effects does it have?”
  4. Data Interpretation – “What does it all mean?”
Variations in the LCA process primarily concern the level of detail established by the scope definition.[11] Full LCA includes collecting and evaluating actual environmental impact data over the complete life cycle of the structure, from construction through disposal and/or recycling. A full LCA analysis delivers higher accuracy, but it also requires more time and money to complete.[12]

Once the scope of the LCA is established, an inventory analysis must be conducted. An inventory analysis breaks down each aspect involved in the product and maps the environmental impacts in terms of specific emissions for every associated process and byproduct as shown in Table 1 and Figure 3.[13]

Inventory Analysis Steps
1. Construct a process flowchart that shows the following:
  • Raw materials
  • Manufacturing processes
  • Transportation
  • Uses
  • Waste management

2. Collect data for:
  • Material inputs
  • Products and byproducts
  • Solid waste, air and water emissions

3. Calculate the amounts of each in relation to the functional unit.
Table 1: Inventory analysis steps.[14]
Inventory Analysis - Polyurethane foam insulation.jpg
Figure 3: Inventory analysis flowchart for a polyurethane foam insulation.
Once the inventory analysis is completed, an impact assessment breaks down the impacts into measurable and comparable terms.[15] Each component is classified by ascribing specific impacts, which are influenced by the scope of the LCA. Once impact categories have been determined, the categories are characterized, or converted so that a common scoring method can be used to evaluate the different impacts.[16] Optional steps include normalization, which scales the data to help determine its relative impact for a given context, and weighting.[17]

Interpretation goes on continuously through the entire LCA as a process of clarifying, checking, quantifying, and evaluating the information used.[18] The first aspect of interpretation is to identify the significant issues based on the inventory and assessment stages of LCA.[19] Next, the impact assessment is used to determine which life cycle stages or components have the most impact on these issues.[20] To ensure the reliability of the LCA, checks must be made to evaluate completeness, sensitivity, and consistency.[21] Finally, since the value of an LCA depends largely on how its results are communicated, the last aspect of interpretation involves drawing conclusions, making recommendations, and reporting.[22]

Civil Engineering Applications


HQEIn most civil engineering applications, the LCA scope will consider the environmental footprint of the component materials as the base unit, rather than breaking down each component into its most basic aspects.[23] Engineers and architects use the component environmental impacts (calculated by chemists and other specialists) to determine the overall footprint of the structure.[24] LCA tools used at the building level, e.g. for civil engineering and architectural applications, include Athena Eco-Calculator, BEES, and Athena Impact Estimator.[25] Relatedly, green building evaluation systems include Leadership in Energy and Environmental Design (LEED), HQE (La Haute Qualité Environnementale, a French standard), and EnergyStar.[26]

In civil engineering, LCA primarily appears in design as engineers attempt to meet project constraints while maximizing sustainability based on archived LCA data. Analyses include options for materials, manufacturing processes, transportation modes, waste management, and end-of-life consideration (as shown in Figure 4).

Building materials.png
Figure 4: Comparitive end-of-life analysis for structural materials.


Case Study: NJMC Center for Environmental and Scientific Education


NJMC.jpg
Figure 5: NJMC center.

The NJMC Center for Environmental and Scientific Education in New Jersey (Figure 5) is one of the
few documented U.S. examples of whole-building LCA. The building is constructed of wooden beams and columns, stick framing, and concrete masonry units.[27] Sustainable design features included a
165-unit rooftop solar panel array, ceiling solar tubes, recycled building materials, a recyclable and locally manufactured standing-seam metal roof, and energy-efficient heating, lighting ,and water systems.[28]

The scope of the LCA was to compare the new NJMC center with typical buildings in the impact categories of ozone depletion, acidification, and eutrophication (excessive nutrient runoff) potential, emphasizing primary energy consumption and global warming.[29] Excluded from the analysis: bathroom supplies, furniture, lab equipment, site work outside of the building footprint, landscaping and outdoor utilities, and any impacts from planning and design.[30] Impacts were calculated on a functional unit of per square foot, and life cycle stages were estimated to be defined by material placement, operation through a 50-year lifespan, and decommissioning.[31]

To perform the inventory analysis, data was collected from multiple US databases depending on the location of origin of the building components. Allowances were given for recycled materials.[32] The mass distribution for the project life cycle is shown in Figure 6.[33]

NJMC life cycle mass distribution.png
Figure 6: NJMC life cycle mass distribution.
Impact assessment was performed using two different methods. Some differences in the results were accounted for by the fact that the methods considered different chemicals in their assessments.[34] Figure 7 shows the impact of each life-cycle stage across each impact category. The higher placement impact resulted from the quantity of materials used in the foundation, photovoltaic cells, concrete foundation caps and floor slab, roof decking, and standing seam metal roof.[35] The operational impact is lower in proportion, and impacts from decommissioning are almost negligible.

NJMC impact distribution.png
Figure 7: NJMC life cycle impacts across each category.
The results were interpreted as follows:[36]
  • Linoleum, which is often considered a green material because it is manufactured from renewable feedstock, carries a large eutrophication burden because of the way it is produced.
  • The life-cycle ozone depletion potential of NJMC is minimal.
  • The life-cycle primary energy consumption of the NJMC is much less dominated by the operations phase than in conventional buildings, due to the energy efficiency of the NJMC and the solar panels.
  • The LCA also highlighted how building material choices may inadvertently shift impacts across impact categories and/or geographies.
  • As predicted building lifespan increases, the primary impacts shift from the construction phase to the operations phase.

Among the conclusions drawn by the NJMC design team, LCA was judged to be a valuable tool for quantifying the benefits of a green building.[37]

Recent Research


Following are synopses of recent research linked to LCA in civil engineering:
  1. High performance fiber reinforced cementitious concrete (HPFRCC) may improve the sustainability of bridge decks by lengthening their service life, as well as by incorporating greener materials.[38]
  2. Pavement overlays are designed as maintenance strategies to extend the service life of roads. Compared to traditional concrete and hot mix asphalt overlays, an engineered cementitious composite (ECC) overlay reduced total life energy by 15% and 72%, greenhouse gas (GHG) emissions by 32% and 37%, and costs by 40% and 58%, respectively.[39]
  3. Disaster resilience is not currently an evaluated aspect of LCA, but arguments have been propounded that susceptibility to hazards such as hurricanes, tornadoes, earthquakes, flooding, fire, and blast should be considered.[40]

References


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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
  2. ^

    Bayer, C., Gamble, M., Gentry, R., and Joshi, S. (2010). AIA Guide to Building Life Cycle Assessment in Practice, The American Institute of Architects (AIA), Washington, DC.
  3. ^ (2011). “History.” Australian Life Cycle Assessment Society (ALCAS), < http://www.alcas.asn.au/about-lca/history> (Dec. 2, 2015).
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    (2011). “History.” Australian Life Cycle Assessment Society (ALCAS), < http://www.alcas.asn.au/about-lca/history> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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  21. ^ Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
  22. ^ Ruggles, R., Phansey, A., and Linder, B. (2015). “Life Cycle Assessment,” chapter 4. Sustainable Design Guide, Dassault Systèmes SolidWorks Corp., <https://www.solidworks.com/sustainability/ sustainable-design-guide.htm> (Dec. 2, 2015).
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    Bayer, C., Gamble, M., Gentry, R., and Joshi, S. (2010). AIA Guide to Building Life Cycle Assessment in Practice, The American Institute of Architects (AIA), Washington, DC.
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  26. ^ Horvath, A. (2012). “Life-cycle Assessment in Civil Engineering.” Proc. Consortium on Green Design and Manufacturing, University of California, Berkeley. <http://lca-construction2012.ifsttar.fr/downloads/ intro/Intro_Horvath.pdf> (Dec. 2, 2015).
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    Bayer, C., Gamble, M., Gentry, R., and Joshi, S. (2010). AIA Guide to Building Life Cycle Assessment in Practice, The American Institute of Architects (AIA), Washington, DC.
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    Bayer, C., Gamble, M., Gentry, R., and Joshi, S. (2010). AIA Guide to Building Life Cycle Assessment in Practice, The American Institute of Architects (AIA), Washington, DC.
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  38. ^ Lepech, M.D., and Victor, C.L. (2006). “Sustainable Infrastructure Engineering: Integrating Material and Structural Design with Life Cycle Analysis.” Advances in Cement and Concrete X: Sustainability, Environmental Change Institute (ECI), 55-60.
  39. ^ Zhang, H., Keoleian, G.A., and Lepech, M.D. (2008). “An integrated life cycle assessment and life cycle analysis model for pavement overlay systems,” 907-912. Life-Cycle Civil Engineering, Taylor & Francis Group, London.
  40. ^ Roberts, K. and Comber, M. (2015). “Looking at the impacts of LEED and resilience.” Civil + Structural Engineer, < http://cenews.com/article/9967/the-future-of-incorporating-lca> (Dec. 2, 2015).