Comparative Cradle-to-Gate Life Cycle Assessment of Burnt Clay and Fly Ash Bricks in Pakistan

Abstract

The study compares traditional burnt clay brick with fly ash brick in Pakistan, based on cradle to gate environmental performance, using an attributional LCA. The functional unit chosen in the plant was 1000 brick of the standard size at the plant gate. The model was developed in openLCA 2.6.1 using the ReCiPe 2016 Midpoint (H) method. Foreground inventory data were obtained from secondary sources, limited primary information and production estimates from literary sources, and ELCD datasets and proxy processes were used to represent background systems. Transportation, construction, use and end-of-life stages were not included and fly ash was assumed to be an industrial by-product with zero burden. Fly ash bricks reduced global warming potential from 466.72 to 197.41 kg CO2-eq per 1000 bricks, representing a 57.7% reduction. The reduction of fine particulate matter formation was 95.8%, for fossil resource scarcity 92.3%, for terrestrial acidification 96.0% and for water consumption 56.6%. Burnt clay bricks showed coal-fired kiln operation as the primary hotspot, while cement production and electricity generation were the primary hotspots for the fly ash system, respectively. The human carcinogenic toxicity and ionising radiation were, however, higher in the case of fly ash bricks. Overall, fly ash bricks had smaller impacts in most categories at the production stage, while more regional primary data and transport modelling and alternative allocation scenarios are required to enhance the comparative assessment for future use.