Embodied emissions of hempcrete wall systems in residential buildings: a comparative case study from Australia

In Australia, embodied greenhouse gas emissions associated with the extraction, production, transportation, and disposal of building materials accounted for 16% of building-related emissions in 2019 and are projected to rise to 85% by 2050 as operational emissions decline. This shift underscores the urgent need to decarbonise material lifecycles. Among various biobased alternatives, hempcrete has drawn growing interest for its renewable, carbon-sequestering properties and thermal performance benefits. However, limited empirical studies have quantified its embodied emissions performance under real-world conditions. This study aims to evaluate and compare the embodied emissions performance of hempcrete external walls against two common wall systems (brick veneer and lightweight steel cladding) by using a process-based life cycle assessment. A real-world case study of a single-storey dwelling in Narara Ecovillage, New South Wales, was used to quantify cradle-to-grave emissions across production, transport, construction, use, and end-of-life stages. Results show that the hempcrete wall system emitted 49.57 t CO₂e, 19.9% lower than brick veneer (61.81 t CO₂e) and 92.5% lower than lightweight steel cladding (927.34 t CO₂e). The dominant source of emissions was long-distance material transport, although substantial carbon sequestration occurred during manufacture (growing), construction and use stages. The comparative analysis highlights the potential of hempcrete in reducing embodied emissions, especially when paired with local sourcing and prefabrication strategies. This study contributes to evidence-based decision-making in low-carbon residential design and supports the inclusion of biobased materials in Australia's decarbonisation efforts.