Measuring sustainability of technology is complex. One reason for this has to do with sustainability itself: it is a broad holistic issue with environmental, economic and social dimensions. A second reason for the complexity is the large number of levels at which the sustainability concept can be applied, and thus the definition of the technology to be assessed. Do we want to assess a product, a service, a production process, a production facility, a company or an industrial sector? Chapter 3 deals with these critical questions in a clear manner. As a third focus for our attention we have to be aware that ‘technology’ is not an isolated system delivering only one product. Modern technology is usually embedded in an industrial ecosystem delivering a set of products, ending up in so-called joint production. This allocation issue is well discussed in Chapter 4: several methods, which allow attributing resources and emissions to a single product or service, are described.