Systematic integration of LCA in process systems design: Application to combined fuel and electricity production from lignocellulosic biomass

This paper presents a methodology to integrate life cycle assessment (LCA) in thermo-economic models used for the optimal conceptual design of energy conversion systems. It is illustrated by an application to a thermo-economic model developed for the multi-objective optimization of combined synthetic natural gas (SNG) and electricity production from lignocellulosic biomass. The life cycle inventory (LCI) is written as a function of the parameters of the thermo-economic model. In this way, the obtained environmental indicators from the life cycle impact assessment (LCIA) are calculated as a function of the decision variables of process design. The LCIA results obtained with the developed methodology are compared with the results obtained by a conventional LCA of the same process. Then, a multi-objective environomic (i.e. thermodynamic, economic, environmental) optimization of the process superstructure is performed. The results highlight the important effects of process configuration, integration, efficiency and scale on the environmental impacts.

Research highlights▶ Systematic methodology to integrate life cycle assessment in process systems design. ▶ Applied to combined fuel and power production from biomass in multiobjective optimization framework. ▶ Importance of proper choice of objective functions and functional unit in polygeneration systems. ▶ Results show influence of process integration, logistics and support materials on LCA indicators. ▶ Though increased efficiency reduces impact, thermodynamic and environmental optima do not correspond.