A Consequential Life Cycle Assessment of Coconut Shell Ash as a Supplementary Cementitious Material

Concrete is essential in construction, but its production is energy-intensive and polluting. This study investigates using coconut shell ash (CSA) as a supplementary cementitious material (SCM). This approach not only prevents waste but also recovers energy from the combustion of coconut shells. India was selected as a case study, being the third-largest coconut producer and the second-largest cement manufacturer.The research employs a Consequential Life Cycle Assessment (LCA) to systematically evaluate the environmental performance of these novel concrete mixes, alongside a comprehensive assessment of the pozzolanic activity of the ashes, and mechanical properties to confirm structural suitability. We conducted an extensive global sensitivity analysis (GSA) on the system parameters, since we are assessing a future scenario and the model is uncertain, particularly concerning the current treatment in India.Including CSA in the concrete mix significantly reduces flexural and compressive strength, primarily because the ash lacks effective pozzolanic properties and acts mainly as an inert filler that retains water, hindering optimal cement hydration. Results demonstrate significant reductions in environmental impacts across 13 of 16 assessed impact categories, primarily due to the substitution of heat and electricity from incineration. These results are confirmed by the GSA.While incinerating coconut shells in India significantly reduces the GWP, primarily due to energy recovery, the resulting ashes are not suitable as a SCM due to their poor mechanical performance, lack of pozzolanic reactivity, and high carbon content.