Reversible Bio-Based Prefabrication as a Carbon Sink: Whole-Life Cycle Assessment of a Straw Passive House in Germany

To accelerate building sector decarbonization, construction systems must combine high operational efficiency with bio-based carbon storage and circular design. This study evaluates a technological framework for reversible bio-based prefabrication through a whole-life cycle assessment (EN 15978) of a Passive House in Lindow, Germany (120 m2 GFA, 50-year service life), using Ubakus, DesignBuilder, and Ökobaudat. Integrating annually renewable straw insulation with a lightweight timber frame and mechanical connections creates a major biogenic carbon sink during production (A1–A3: −174.30 kg CO2e/m2 GFA). Off-site panelization limits transport and assembly impacts (A4–A5) to 8.67, while maintenance accounts for 2.17. The operational heating demand reaches 12.95 kWh/m2·year, and the total energy demand is 535.19 kg CO2e/m2 GFA over 50 years (B6). Design for disassembly with 50% component reuse lowers the net end-of-life impact (C + D) by 42% compared with standard incineration (118.9 vs. 204.6). Consequently, reversible bio-based prefabrication achieves a net whole-life carbon footprint (A1–D) of 490.59 kg CO2e/m2 GFA and a PENRT of 11,013.28 MJ/m2 GFA. These findings demonstrate that integrating prefabricated straw construction with passive-house design creates a scalable biogenic carbon sink building solution that substantially reduces whole-life carbon emissions and supports European climate targets.