
106 Principles of Sustainable Energy Systems
Figure 2.5 shows a basic schematic of the PCA methodology. The individual sequen-
tial steps in the process are separated out, and all inputs and outputs are identied for
each process in the trajectory. Inputs and outputs include the product as it is trans-
formed, the utilities, U, services, S, materials, M, and equipment, E, as well as possibly
joint products, JP, and other outputs, OO. A PCA can be done for any one part of a
process chain, for example, from natural resources, R, to consumer products, P, or the
PCA can be done for the whole lifespan through the steps of consumer end use and dis-