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emission inventories and commodity flow maps

examples of emission inventory and commodity flow projects


As discussed below, conducting thorough emission inventories and creating commodity flow maps is complicated because the necessary data are not collected cohesively or comprehensively.

An inventory of pollutant releases is the backbone of any assessment of environmental performance and of identification of high-priority pollutants. However, quantifying environmental releases of compounds is complicated by a lack of comprehensive data on releases. There is no single source of data that contains a complete inventory of emissions. Further, separate sources of data do not in general contain information on a discrete segment of emissions; instead, sources of data tend to have areas (e.g. compounds, media) that overlap. Nevertheless, several sources of data must be combined in conducting a complete emission inventory for most compounds. Data sources might include the United States ' Toxic Chemical Release Inventory (TRI), the Canadian National Pollutants Release Inventory (NPRI), and other industry- or compound-specific sources of information.

An overview of the scope of some of these sources of data and their relationships with each other is depicted in Figure 1, taken from a project that focused on Southwest Lake Michigan (SWLM). Release data for this project were drawn from the TRI, the Biennial Report System (BRS), which provides information about hazardous waste management, and the Aerometric Information Retrieval System (AIRS), which provides information on releases of criteria air pollutants and hazardous air pollutants. As shown in the figure, some data sources overlap, while information on some emissions and wastes is not available. Emissions data from small sources is particularly difficult to obtain, but there is generally a defensible way to estimate such releases, such as using census data on employee counts or population combined with published research about releases from a limited geographic area.

Commodity flow mapping, which is becoming a common endeavor in the field of industrial ecology, can provide information on quantities and sources of material that is being wasted or it can be used to identify industries where a substitute for an environmentally problematic compound would be most effective. Developing commodity flow maps is challenging, partly because current data on production, trade, and process inputs can be difficult to obtain and are not available in any one source. Generally, it is only feasible to trace a single element, because compounds are transformed in processes. For example, one can trace the flows of a metal through the economy because no matter what compounds the metal is incorporated in, it will still exist as the metal. If it is known that x pounds of the metal enter a process as feed and y pounds of the metal exit in the product, then it is known that losses of the metal are x-y. This is not the case for compounds, which are capable of reacting with other compounds and forming new compounds.

examples of emission inventory and commodity flow projects