2.2. Research range and determination of system boundary
The life cycle of the iron and steel industry includes rawmaterial
extraction (mainly iron ore and coal), iron and steel production
processes, steel product consumption, recycling, and transportation.
Thus, life cycle-based water footprints can be utilized to
assess the effects of products or businesses on aquatic environments
during the whole product or business life cycle. However, the
water footprints of some inputs (e.g., raw materials and supply
chain) upstream of steel production are difficult to obtain for enterprises.
In addition, the extraction and transportation of raw
materials can be very different depending on the sources and are
typically not well documented, and the consumption of iron and
steel products varies dramatically depending on the end use (e.g.
buildings, pipes, automobiles, and appliances). Finally, the water
used in the installation and decommissioning of the steel mill is not
typically tracked, so there is no data available for this aspect. Given
the multi-decade life of most steel mills, this is likely a small fraction
of the overall water footprint, and thus it is not considered
here. Fig. 2 illustrates the research boundary (the object of the
study is in solid lines). The production processes are utilized as the
main body, which is the most important part that manufacturers
should consider when they decide to alleviate water risk, in industrial
water footprint assessments. Thus, we focus on the water
footprint assessment in the production process of a steel enterprise.