System boundary selection in life-cycle inventories using hybrid approaches

Area of Science:

• Environmental Science
• Industrial Ecology
• Sustainability Assessment

Background:

• Life-cycle assessment (LCA) evaluates environmental impacts across product supply chains.
• Current ISO standards present practical difficulties in defining system boundaries and process inclusion criteria.
• Exclusion criteria are often subjective, lacking scientific basis and potentially compromising result validity.

Purpose of the Study:

• To critically examine system boundary definition challenges in LCA.
• To introduce and advocate for hybrid approaches as a solution to boundary selection problems.
• To ensure ISO compliance while broadening system boundaries in LCA studies.

Main Methods:

• Discussion of current LCA methodologies and ISO standards regarding system boundaries.
• Exploration of economic input-output (EIO) analysis for system boundary assessment.
• Proposal and description of hybrid input-output-assisted LCA approaches.

Main Results:

• Subjective system boundary decisions in LCA can lead to invalid or incomplete environmental impact assessments.
• EIO analysis demonstrates that excluded processes can significantly contribute to overall impacts.
• Hybrid LCA methods provide a framework for scientifically defining boundaries and ensuring ISO compliance.

Conclusions:

• Hybrid input-output-assisted LCA methods effectively address the system boundary selection problem.
• These approaches enable broader system boundaries and maintain compliance with ISO standards.
• Implementing hybrid methods enhances the scientific rigor and reliability of LCA studies.