Rethinking life-cycle assessment, this paper proposes system expansion to avoid co-product allocation. Addressing the challenge of how to partition resource consumption and emissions across multiple products from the same process, the article argues that system expansion offers a superior approach for prospective LCAs. It addresses the controversial issue of how resource consumption and emissions should be divided among these co-products when assessing only one. Using examples like joint production of chlorine and sodium hydroxide, the authors demonstrate the implementation of system expansion. They emphasize issues such as handling near-to-waste by-products and material recycling. The model covers diverse co-product scenarios, including credits for material recycling and downcycling, all with the same theoretical model and practical procedure. This methodology streamlines prospective life-cycle assessments, aligning with international standards and reducing the impact of arbitrary allocation choices.
Published in the Journal of Industrial Ecology, this paper is highly relevant to the journal’s focus. Addressing co-product allocation in life-cycle assessment aligns with the journal’s interest in industrial sustainability. The topics of renewable energy and environmental engineering fit within the journal's scope.