Inventory analysis

In the inventory analysis the product system, is analysed. By this is meant the system of economic and physical processes providing the service defined by the functional unit. The aim is to quantify all the economic and physical inputs and outputs of the chosen product system. This involves quantifying all material and energy flows across the system borders. 

The methodology of inventory analysis is well-developed in comparison to the other components of LCA. Some practitioners still prefer to use the inventory as the sole base for improvements, claiming that the impact assessment step is still not sufficiently developed. While it is true that the inventory stage is sufficient to simply identify the emissions, it does not evaluate their relative environmental impacts. For this an impact assessment is necessary. 

The SETAC Code of Practice defines five important elements of an inventory analysis  

This is not a chronological order of activities. Heijungs et al. [8] propose four steps which describe tasks in a clearer chronological order  

Probably the most important step in the LCA is the inventory analysis, which carefully documents the (raw) materials necessary for the product, the emissions, required energy input and environmental burden at disposal by either recycle, disposal, etc. Here it is very useful to clearly mark the system boundaries. ISO 14040 [1] defines inventory analysis as follows  

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. 

Let us take the PE mentioned in the goal as an example. PE is produced from ethylene, as we saw in Chapter 11. The ethylene, on the other hand, comes from a refinery or chemical plant, and the ultimate source of ethylene is, therefore, crude oil or another fossil fuel. Electrical energy is required for the process. There are emissions at the various stages. The final PE is then 

For ethylene, similar data could be constructed from either an average of ethylene producers in this geography or on-site naphtha crackers. In certain cases, databases exist for certain commonly used compounds. In other cases, data are unavailable and estimates have to be made. In case of plants that produce more than one product, the total emissions are allocated proportionally to their sales. 

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FIGURE 15.3 Example of a product system, production and use of steel sheet metal, for fife cycle inventory analysis. 

ISO, F.nvironmental Management—Life Cycle Assessment—Goal and Scope Definition and Inventory Analysis (ISO 14041). 

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... 

ISO 14041 1998 (1998) Environmental Management - Life Cycle Assessment - Goal and Scope Definition and Life Cycle Inventory Analysis. European Commitee for Standardisation, Brussels, Belgium. 

The interpretation step is for a reassessment of the inventory analysis, and the impact assessment is to assure that the goals of the study were met. The LCA has applications in process and product development and improvement, strategic planning, envirorunental benchmarking, and product marketing. 

A complete inventory analysis is conducted for each segment of the fluid milk supply chain to account for all the resource inputs and the primary and secondary sources of GHG emissions (CO2, CH4, and N2O) to air, water, and soil. The resource inputs include raw materials and energy. Their impact on GHG emissions are secondary sources of GHGs. The primary sources of GHG emissions are associated with farm operations. 

The inventory tasks is to collect environmentally important information about relevant processes involved in the product system. Inventory collects information about unit processes at first and subsequently, an inventory of inputs and outputs of the system and its surroundings is carried out. The goal is the identification and quantification of all elementary flows associated with product system. Inventory analysis is the nature of the technical implementation of LCA studies. It is an essential part of a study, has high demands for data availability, practical experience in modelling product systems and, in the case of using database tools, it is necessary to master them perfectly and to understand their function [46]. The inventory phase principle is data collection that is used to quantify values of the elementary flows. This phase represents a major practical part of the LCA study, time consuming and with demands for data availability and author s experience with modelling product system studies [47],... 

Rebitzer G, Ekvall T, Frischknecht R, Hunkeler D, Norris G, Rydberg T, Schmidt WP, Suh S, Weidema BP, Pennington DW. Life Cycle Assessment Part 1 Framework, Goal and Scope Definition, Inventory Analysis, and Applications. Environment International. 2004 30(5) 701-720. DOI 10.1016/j.envint.2003.11.005... 

ISO (1998) ISO 14041 Environmental management - Life cycle assessment - Goal and scope definition and inventory analysis. International Organisation for Standardisation, Geneva... 

The aim of the Life Cycle Impact Assessment (LCIA) is to facilitate the interpretation of the results of the inventory analysis. The result of the inventory analysis is an emission profile for each alternative system. In this study the emission profile is the total of all emissions to air, water and soil from the grave-to-cradle chain for the use of cushion vinyl floor covering, including the up chain processes, like electricity production and the down chain processes, like the incineration and landfill of the waste. Such an emission profile may consist of hundreds of emissions and extractions. In LCA impact assessment the total of interventions (emissions, extractions) of a process chain is evaluated in terms of environmental problems (impact categories). 

Authors have stressed the importance of LCAs for comparing environmental and energy impacts, outlined the difficulties encountered in conducting such assessments, and provided examples of past LCAs. They addressed additional issues and also examined the usefulness of LCAs in formulating public policy. When a given pollutant arises at multiple sites, life-cycle impact analysis is often replaced by life-cycle inventory analysis (Graedel et al., 1995). 

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. 

Figure 4.4 Elements of a life cycle inventory analysis.

The key concept of inventory analysis is that all in- and outflows of matter are carefully documented. This inventory is therefore cumulative (see Figure 12.1). For example, an inventory of the PE production can be constructed from plant data (note that compounds and figures are hypothetical in Table 12.1). 

Maintaining inventory III (other, such as stock appearance and inventory analysis) 3.36... 

Ekvall, T., and B.P. Weidema. 2004. LCA methodology, system boundaries and input data in consequential life cycle inventory analysis. Int. J. LCA 9 161-171. 

ISO International Standard 14041, 1999E. Environmental management—life cycle assessment—goal and scope, definition and inventory analysis. International Organization for Standardization (ISO), Geneva. 

Ekvall, T., Key methodological issues for life cycle inventory analysis of paper recycling, /. Cleaner Prod., 7, 281-294, 1999. 

ISO ISO/TR 14049 Environmental Management—Life Cycle Assessment—Examples of Application of ISO 14041 to Goal and Scope Definition and Inventory Analysis ISO/TR 14049 International Organization for Standardization Geneva, March 15, 2000, 2000. 

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