Life cycle assessment (LCA) modelling of resource-related technologies can be challenging in the context of circular economy, bioeconomy, recycling and integrated waste management, where materials are recirculated within processes and undergo chemical-physical transformations. This implies redefinition of physical flows within the LCA model. Additionally, physical flows may have non-linear responses to changes in model parameters and background processes, involve activities such as extraction of materials and chemical substances, and directly affect emissions. However, these non-linear responses and links between physical flows within technologies are often neglected. In this study, four novel LCA modelling features are provided: i) mixing and/or redefinition of physical flows; ii) substance recirculation within physical flows; iii) integration of physical flows from background processes into foreground processes; and iv) (multi)-conditional sequence flows, while maintaining substance and material balances throughout the system. As an expansion of EASETECH, an existing user-friendly LCA software tool for modelling of environmental technologies, a “process editor” (EASETECH+) allows implementation of these four features into EASETECH. The modelling features are implemented into EASETECH as seven individual processes “modules” and applied in an illustrative case-study focusing on anaerobic digestion of source-segregated organic household waste. The case-study demonstrated that the new modelling approach for physical flows, including recirculation, links between flows from background to foreground processes and conditional flows, considerably affected both results and interpretation of the LCA modelling. The recommendation is that process-oriented LCA modelling as presented here can provide critical new insight into the environmental performance of waste technologies and systems.
- Non-linear relationships
- Mass balance
- (Multi-)conditional-sequence flow
- Recirculation and redefinition of physical flows