Life-cycle inputs/outputs

Life-cycle Inputs and Outputs 195 Table 5 (continued) ... 

LCIA operates on the inventory of elementary flows for the product life cycle (input of resources and output of emissions) into potential impacts on the environment. These inventory flows are translated into scores for indicators that represent impact on human health, natural environment, and natural resources within a number of predefined impact categories (EC-IRC 2011). 

The assessor then quantifies the inputs and outputs for each step (or unit process) in the product or process life cycle. Inputs may derive from direct process knowledge, literature values, databases maintained by industry organizations or governmental agencies, or measurements. Outputs are estimated using mass balance calculations, noting uncertainties and assumptions. These calculations quickly become quite complicated due to the number of steps in the life cycle and the inputs and outputs that occur at different times and places. As a result, LCA commonly requires software tools [99,100]. Further, it may be worthwhile to perform a sensitivity analysis at the conclusion of this phase and reiterate the calculations with a refined set of assumptions. 

Flow-sheet models are used at all stages in the life cycle of a process plant during process development, for process design and retrofits, and for plant operations. Input to the model consists of information normally contained in the process flow sheet. Output from the model is a complete representation of the performance of the plant, including the composition, flow, and properties of all intermediate and product streams and the performance of the process units. 

Life cycle assessment (LCA) is a compilation and evaluation of inputs, outputs, and the potential environmental impacts of a product system throughout its life cycle. The LCA methodology is comprehensively described based on the ISO 14000 series standards. References are also given to I.CA information sources. 

Another problem of EGAs is that they are non-site-specific. The reasons for this lie in the fact that they include the whole life cycle of systems with resources which may originate in different countries and waste products and emissions which may distribute globally. They deal with factual inputs, outputs and the environmental impact potentials of the system under investigation on a global, and, in some cases, regional scale. Yet, they do not address the intrinsic risks resulting from the system itself. However, a combination with risk assessment methods can be used to close this gap. 

Carbon footprint is most appropriately calculated using life-cycle assessment or input-output analysis [3,4]- In this sense it is based on the ISO 14040 [4] and ISO 14043 [5] norms, on life cycle assessment (LCA). Specific norms for carbon footprint of enterprises and products are ISO 14064 (part 1,2, and 3) [6-8], ISO 14067 [9], and PAS 2500 [10]. Carbon footprint calculation process is shown in Figure 1. 

In addition to energy and environmental outputs in each step, energy and environmental inputs from raw materials use are also included. Generally, life cycle flows include all raw materials used for extraction. Likewise, life cycle flows from intermediate energy sources such as electricity, back to the extraction of coal, oil, natural gas, limestone, and other primary resources should be included. 

For a full life cycle assessment, the basic principle is that each material and energy input into the system should be traced back to natural resources obtained from the environment, or to releases into the environment. These are termed elementary flows , and they represent inputs into or outputs from the system being analysed. In an analysis of this type, it may be relatively straightforward to assign a material value to a flow of (for example) water effluent into the environment, but what may be less certain is the environmental impact of such a flow in a quantitative sense. 

The benefits of using economy input-output life-cycle analysis (EIO-LCA) to estimate economy-wide discharges are significant. LCA is a systematic tool that is used to provide information on the consequences of alternative products and processes, thereby facilitating effective environmental decision-making. This is generally achieved... 

The core of LCA is a cradle-to-grave life-cycle inventory analysis that is fundamentally an engineering exercise describing a chemical, material, and energy accounting balance for the entire product system. The various inputs and outputs are collected or inventoried for each unit operation in the defined system (see fig. 4.4). A key qualifier in the figure is the definition of the system boundary, as it will directly affect the quality of the final results and conclusions. The inventory practice and methods are relatively well defined. 

Industry use of LCA as a tool to improve environmental performance is increasing. An LCA quantifies energy and resource inputs and outputs at all stages of a life cycle, and then determines and weighs the associated impacts to set the stage for improvements. 

This comprehensive approach allows for efficient integration between processes, different phases of product life cycle, and integration between different sites in the supply chain. This integration provides opportunity for efficiency in that process owners are integrated with each other s needs and expectations. Duplication of effort is avoided and efficiencies gained. Quality outputs from one process become reliable inputs into the next process. Management and leadership will have access and insight into compliance, infrastructure, and performance metrics of all processes on a comparable basis. This provides leadership the opportunity for risk-based resource allocation to appropriate areas of the enterprise. 

Part III, "Case Studies" (Chapters 9 through 12), takes these illustrations a bit further, namely, by demonstrating the analysis for some of the most important processes in industry energy conversion, separations, and chemical conversion. Chapter 12 briefly discusses the concept of life cycle analysis, which aims to compare the consolidated inputs and outputs of a process or a product "from the cradle to the grave" [9], and its extension to include the minimization of process irreversibilities in a so-called exergetic life cycle analysis [10]. 

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."... 

Inventory analysis involves data collection and calculation procedures to quantify relevant inputs and outputs of a product system. These inputs and outputs may include the use of resources and releases to air, water, and land associated with the system. These data also constitute the input to the life-cycle impact assessment. 

Next, Cornelissen extended the LCA study to include the effect of depletion of natural resources making use of ELCA, the exergetic life cycle assessment. In this analysis a full mass and energy balance was made, that is, a first law analysis. Exergy values for all mass and energy streams were included in accordance with the Tables 6.1, 6.2, 6.3, 7.1, 7.2, 7.3 and 7.4 in Chapters 6 and 7. This analysis clearly showed where work was available in inputs and outputs and where it was lost. He could show that the cup scored less favorable than the mug in terms of depletion of natural resources (817 MJ vs. 442 MJ). 

Life-cycle inventory (LCI) deals with the material inventories of each phase of a product life, namely by tracking the variation between input and output flows. 

Fig. 1 Phaeocystis life cycle diagram. Solid-line ovals Phaeocystis life cycle stages dashed-line ovals other ecosystem components. Solid arrows life cycle transitions hollow-line arrows inputs to or outputs from Phaeocystis. ><]...

Hollow-line arrows in Fig. 1 represent hypothesized flows to or from non-Phaeocystis components of the larger ecosystem. In some cases these serve as controls on life cycle flows, and in other cases they are boundary inputs or outputs of the Phaeocystis life cycle. Three main outputs from the Phaeocystis life cycle are represented. Two are grazing on solitary cells (upper left), and grazing on all size classes of growing colonies (upper right). The third is viral lysis (left center), which is an output process usually emphasized in viral studies. However, infection, an input process, must occur for viruses to complete their life cycle... 

The total energy efficiency of the plant, which is determined by the total available output energy and total input energy, reaches 72.6%. These heat balance data are available for LCA (life-cycle assessment). 

LCI is the methodology for estimating the consumption of resources, the quantities of wastes, the emissions, the traffic accidents, the noise, etc., that are associated with each stage in a product s life cycle. The material and energy flows are modeled between the processes within a life cycle. The overall models provide mass and energy balances for the product system, its total inputs and outputs into the environment, on a per functional unit basis. 

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