Developing a Sustainability Framework for the Second Life of Palm Oil Clinker

Palm oil constitutes a main agricultural commodity for the country, therefore the large quantity of palm oil clinker (POC) produced as a waste at the refineries is not unexpected. Upon the discovery of the rock-like but porous POC as being strong and robust enough as substitutes of aggregates, they have since become popular alternative materials in road pavement and concrete. However, POC is also potentially viable in other civil engineering applications for a second life, and this includes brick-making, soft soil stabilisation and greywater filtering. (i) Powdered POC was found to contribute to greater strength gain than cement in baked clay bricks, promising a cheaper yet more environmental-friendly building material. (ii) Admixed with soft clay soil, ground POC was found to effectively dry and strengthen the originally weak soil through induced cementation, similar to those achieved by using commercial binders, like cement and lime. (iii) Crushed POC replacing conventional sand in a greywater filter for domestic kitchen sink discharge showed evidence of effective cleansing, where the filtered water met the requirements of Standard B effluent suitable for release into public waterways. While the experimental results strongly suggest the huge potential of restoring POC to a useful second life in various civil engineering applications, encompassing the ‘rebirth’ from cradle-to-grave in a sustainable framework is essential as assessment and justification for its continued viability. By putting the materials and methods in a birth-to-death cycle, from production, application to end-of-life management, the relevant causes and impact are reviewed and examined. The inter-related societal, economic and environmental aspects are then incorporated in a holistic 2-pronged life cycle and functionality analysis. In short, the sustainability framework features not only technical soundness of the POC’s second life, but considers in detail the other consequential and accompanying factors throughout the ‘second’ life cycle of POC.