Including exergy analysis in industrial ecology: The case of combined cycle power plants with CO2 capture

Life cycle analysis for material processing is an estableshed part of industrial ecology. A similar analysis of energy needs in industrial processes is still under discussion in this field. We argue that exergy analysis can play a role in industrial ecology. Several indicators are then relevant, and we calculate three. The first is the fraction of renewables of all exergy inputs. The second is the exergetic efficiency of the process. The third is an environmental efficiency, which is the quotient of exergy inputs for the production process and the sum of all exergy requirement for abatement of emissions and to close the material cycles. These indicators evaluate the short and long-term perspectives of the process, ot its sustainability. Results arepresented for a standard natural gas-fired combined cycle power plant and for a power plant that operates on hydrogen rich fuel produced by an auto-thermal reformer. Per kWh electricity produced, the latter type of power plant has a smaller end emissionof carbon dioxide and smaller exergy efficiency, When the processes that close the material cycles are taken into account, the power plants gain similar indicators. We conclude that the calculations offer useful premisses to a public discussion about such power plants.