“Substance flow analysis (SFA) focuses on material flows of just one, chemically defined substance, or a limited group of such substances through the metabolism of a relatively extensive, predefined geographic region. Within this region, all significant economic sources acting as the driving forces behind induced substance flows are considered. “Substances,” as chemical elements and their compounds, comprise the “material” under study. Typical examples in existing research include nutrients such as nitrogen and phosphorous, chromium, mercury, lead and other heavy metals, carbon, water, and organochlorine compounds.” (Daniels and Moore 2001)

There are a fair number of SFA studies done on an urban scale. Recurring substances in these studies include nitrogen, phosphorus, and metals. Compared to other material flow studies, SFA work requires a more detailed, nuanced understanding of the inner workings of the city under study. Instead of just focusing on the total input and output, SFA studies generally look at specific uses of the substance, which will include details on the types of consumers, as well as transformation that may happen within the city. In this regard, SFA can be much more useful for policy guidance, but it will require a greater depth of data that may be hard to come by.