These unit processes can easily be distinguished as the process record contain links to the relevant processes. The environmental load connected to making the hot iron is described in a series of other unit processes. This means the unit process starts at the point where molten iron comes in from another process. The unit process for making steel contains transport of hot metal, and other input materials, to the converter, the steel-making process and casting. Whereas a unit process contains only emissions and resource inputs from one process step, plus references to input from other processes. a system process only contains inputs and outputs to and from the biosphere per reference product, so per individual output to technosphere. What is the difference between unit and system processes?Ī system process can be calculated out of unit processes and is not an independent dataset. For this reason, they are also known as an aggregated life cycle inventory (LCI). In other words, a system process is a single, cradle-to-gate aggregation of all environmental flows caused by the provision of the reference product. System processes are the result of the compilation and quantification of inputs and outputs for a product throughout its life cycle (ISO 14040:2006). There are also aggregated versions of processes. In a database such as ecoinvent, all unit processes are documented to describe their scope. After all, adding more detail does not always offer significant value.

Many unit processes do not represent the smallest known process step. The scope of a unit process can vary, and there are often several possible approaches to defining the scope and level of detail of life cycle elements.

Unit processes describe a distinct part of a life cycle, not a whole life cycle in themselves. What is a unit process?Ī unit process is the smallest element in the life cycle inventory analysis for which input and output data are quantified (ISO 14040). In this article, you will learn what unit and system processes are and what the differences between them are. In SimaPro desktop, the ecoinvent libraries are divided into unit and system processes.

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