Chapters 5-10 show six different metrics that can be put into practice as sustainability metrics. Chapter 5 focuses on metrics especially designed to assess renewables-based energy: biofuels. The presented net energy balancing method may be the preferred method in systems where the input of renewables versus non-renewables is so obvious. Chapter 6 presents the typical environmental life cycle analysis, where a major emphasis is on emissions into the environment, rather than resource extraction from the environment. Chapter 7, on the other hand, presents a thermodynamics-based method – exergy analysis – where emphasis is put on the nature (renewable versus non-renewable) and technical potential of natural resources. Chapter 8, explaining the substance and material flow analysis method, makes clear how natural resources flow into our industrial enterprises and how they flow partially back into the environment as waste material. Chapter 9 on the ecological footprint and Chapter 10 on the sustainable process index both present a single indicator quantifying the impact that technology and mankind have on the environment, by taking into account both the nature of used resources and the generated emissions.