Ilka Loubser

More than 8% of all concrete produced is wasted. This is an alarming trend considering that concrete production uses a vast amount of non-renewable materials and emits 7% of all carbon emissions. New Zealand is strongly echoing a global trend of increased government regulation to address the issue, with current legislative changes underway that will heavily penalise landfill disposal. 

The majority of concrete waste is returned to batch plant yards, making concrete manufacturers key players in treating concrete waste. With limited ability to prevent or minimise waste, the only viable alternatives available to manufacturers are to send waste to landfill or to employ reuse and recycling strategies. Therefore, manufacturers currently have a critical need for a systematic evaluation of concrete waste treatment by reusing or recycling. This is to determinewhether concrete waste treatment is more beneficial than sending waste to landfill, and to establish which treatment alternative provides the most sustainability benefits whilst beingpractically feasible to implement. 

This study aimedto provide thisevaluation by usinga case study of a New Zealand concrete manufacturer to determine the most sustainable and practically feasible waste treatment alternative. An Analytical Hierarchical Process was used to evaluate sixtreatment alternatives against a range of criteria. Alternatives included current practices employed by the case study and viable options identified from literature. Members of the case study pivotal in the selection and delivery of a treatment strategy were selected as research participants. Theyweighed the decision criteria and qualitatively assessed alternatives against social, technical, and operational criteria. Economic and environmental criteria were quantitatively assessed. 

The results of the evaluation indicate that economic criteria dominate decision-making, that recycling is a worthwhile undertaking, and that a mechanical reclaimer system is the preferable treatment alternative for a concrete manufacturer. A sensitivity analysis was performed on the results and found that the reclaimersystem becomes more preferable once the new landfill fee regulations take effect. It was demonstrated that widespread adoption of the reclaimer system by concrete manufacturers can significantly reduce concrete waste and deliver valuable sustainability benefits.