Enhanced Disaggregation Method for Accurate Carbon Footprint Quantification of Construction Materials in Early-Stage Design

The overall environmental impact of the construction industry is on the rise in tandem with the ongoing rapid urbanisation. Identifying opportunities for emission reductions during the early-stage design phase is paramount, as this is when pivotal decisions and emission savings can be made. However, current methods for quantifying emissions during this phase often yield misleading results. Process Life Cycle Assessment (P-LCA) provides detailed insights, but it is also constrained by truncated system boundaries. Meanwhile, Input-Output Life Cycle Assessment (I-O LCA) provides a more complete system boundary but lacks the granularity that designers often require. To address this gap, this study - which also contributes to Subtask 2 of IEA EBC Annex 89: Ways to Implement Net-Zero Whole Life Carbon - introduces a new method to disaggregate input-output tables and applies it to the cement, lime, and plaster sectors within the EXIOBASE Multiregional Input-Output (MRIO) database. This method enhances IO sector granularity by separating these materials into distinct categories without the complexities associated with traditional matrix rebalancing. The preliminary findings offer a more detailed breakdown of carbon footprint estimates, revealing substantial variations in carbon footprints compared to the aggregated value. The aggregated value for cement remains unchanged at 1.62 kgCO ₂eq/£, while lime shows the highest emissions intensity at 2.91 kgCO ₂eq/£ and plaster shows the lowest at 0.95 kgCO ₂eq/£. The findings also show a key difference between direct and indirect emissions when comparing monetary and physical units (kgCO ₂eq/£ and kgCO ₂eq/tonne). Cement and lime have a higher share of direct emissions in physical units (92% and 91% respectively) than in monetary units (55% and 75%), while plaster shows the opposite shift, with 26% direct emissions in monetary units and 55% direct emissions in physical units.