A Note on Life Cycle Analysis

In the previous chapters, thermodynamic analysis is used to improve processes. However, as pointed out in Chapter 9 (Energy Conversion), the exergy analysis did not make any distinction between the combustion of coal and natural gas and, as a result, could not make any statements regarding toxicity or environmental impact of exploration, production and use of the two fuels. A technique that can do this is LCA. What exactly is life cycle analysis In ISO 14040 [1], life cycle analysis (or life cycle assessment) is defined as the compilation and evaluation of the inputs, outputs and potential environmental impacts of a product throughout its life cycle.  

LCA is a tool to evaluate and analyze the environmental burden of a product throughout all stages of its life. Thermodynamic analysis, on the other hand, is not restricted to a product, but is equally well applied in the analysis of processes. A product and a process are separate entities, but they are related since the purpose of a process is to manufacture a product. Because of this, thermodynamic analysis can easily be used for a product (e.g., lost work per unit weight product, as in the polyethylene (PE) case study, Chapter 11). 

The environmental burden covers all impacts on the environment and includes extraction of raw materials, emission of hazardous and toxic materials, land use, and disposal. In certain cases, the analysis only takes into account the burden up to the gate of the producing facility and, in other cases, the analysis takes into account the actual disposal of the product. In the former case, the analysis is termed a cradle-to-gate analysis, while in the latter case it is referred to as a cradle-to-grave analysis. 

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Jensen WB (1997) A note on the term Chalcogen . J Chem Educ 74 1063-1064 Fischer W (2001) A second note on the term Chalcogen . J Chem Educ 78 1333 Fthenakis V, Wang W, Kim HC (2009) Life cycle inventory analysis of the production of metals used in photovoltaics. Renewable Sustainable Energy Rev 13 493-517 Waitkins GR, Bearse AE, Shutt R (1942) Industrial utilization of selenium and tellurium. Ind Eng Chem 34 899-910... 

The engineer s selection of the products herein specified are predicated on a thorough examination of design criteria, construction methods, and comparative extended life-cycle analysis. Deviations from the specification will not be permitted except as noted in I.B.3 below. 

The second and more common hardware FMEA examines actual system assemblies, subassemblies, individual components, and other related system hardware. This analysis should also be performed at the earliest possible phase in the product or system life cycle. Just as subsystems can fail with potentially disastrous effects, so can the individual hardware and components that make up those subsystems. As with the functional FMEA, the hardware FMEA evaluates the reliability of the system design. It attempts to identify single-point failures, as well as all other potential failures, within a system that could possibly result in failure of that system. Because the FMEA can accurately identify critical failure items within a system, it can also be useful in the development of the preliminary hazard analysis and the operating and support hazard analysis (Stephenson 1991). It should be noted that FMEA use in the development of the O SHA might be somewhat limited, depending on the system, because the FMEA does not typically consider the ergonomic element. Other possible disadvantages of the FMEA include its purposefiil omission of multiple-failure analysis within a system, as well as its failure to evaluate any operational interface. Also, in order to properly quantify the results, a FMEA requires consideration and evaluation of any known component failure rates and/or other similar data. These data often prove difficult to locate, obtain, and verify (Stephenson 1991). 

Resource and environmental profile analysis (REPA), the forerunner to the current practice of life cycle assessment, focused on quantifying the energy requirements and emissions of a product or process but not the impacts on human health or the ecosystem. Ideally, according to the originators of REPA, the analysis would be linked to a risk assessment of emissions related to a process or product [91,92]. It is worth noting, with respect to the theme of this book, that REPA originated in 1969. Environmental life cycle considerations did not formally enter into product development or modification before that time. 

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