Exergy-Based Sustainability Analysis for Tile Production From Waste Plastics in Uganda

This paper presents an exergy-based sustainability analysis of manufacturing roof tiles from plastic waste in Uganda. Exergy analyses measure the sustainability of industrial processes. This work focuses specifically on the developing country context and on utilizing waste material. A summary of the current plastic waste situation in Uganda, the environmental and health issues associated with plastic waste, current means of recycling plastic waste into new products, and an analysis of the Ugandan roofing market are presented. The motivation for this study is to examine the resources utilized to improve overall exergy efficiency, reduce production costs, and reduce negative environmental impacts. The company, Resintile, is the only manufacturer of roof tiles from plastic waste in Uganda. Their tiles comprised mainly of sand and plastic waste are manufactured in an industrialized process involving drying, extrusion, and pressing. The exergy consumed at each stage including transportation is presented. The extruder consumes the majority of the exergy, but wrapping insulation around the barrel could save over 3 MJ, and a heat engine could provide over 7.5 MJ of usable exergy. The total exergy consumed to produce one batch of seventy-five tiles is over 122 MJ, the potentially recoverable exergy is over 5 MJ (4.3% of consumed exergy), and the realistic recoverable exergy is nearly 10.7 MJ (8.7% of consumed exergy). The realistic can be greater than the potential by adding a heat engine to the sand drying process to generate usable exergy rather than merely recover consumed exergy. Resintile’s plastic roof tiles save a net 86.3 kg of CO₂ from entering the atmosphere per batch of tiles and adoption of the suggested improvements to the manufacturing process would save an additional 3.8 kg of CO₂ per batch.