Economic-balance hybrid LCA extended with uncertainty analysis: case study of a laptop computer

The emergence of Life Cycle Assessment (LCA) on the global stage as a design and policy tool increases the importance of assessing and managing uncertainty. This article develops and implements uncertainty methods for hybrid LCA. Hybrid LCA combines a bottom-up construction of the supply-chain based on facility-level data on material/energy use with a top-down economic input-output (EIO) model to account for processes for which direct data were unavailable. For the bottom-up part of the LCA, we account for variability in process and usage pattern data by developing parameter ranges. For the EIO side we develop a method to assess price uncertainty. These methods are explored through a case study examining energy use and carbon dioxide emissions of manufacturing and use of a laptop computer, a 2001 Dell Inspiron 2500. Results show that manufacturing the computer requires 3010-4340 MJ of primary energy, 52-67% less than the energy to make a desktop computer, and emits 227-270 kg CO₂. The manufacturing phase represents 62-70% of total primary energy of manufacturing and operation. This indicates, as for desktop computers, that mitigating manufacturing energy use, for example through extending lifespan, can be an important strategy to manage the life cycle energy of laptop computers. Results also indicate that truncation error from excluded processes in the bottom-up process model is significant, perhaps particularly so due to complex supply chains of information technology products.