Moving towards resource efficiency and circular economy in the brick manufacturing sector in Zimbabwe

摘要

The life cycle assessment of the ABC (Pvt) Ltd brick manufacturing plant has considered land use, fossil resource scarcity, water consumption, global warming and fine particulate matter formation as the impact categories for assessment, with clay mining and coal as the input flows with the highest significant contributions to environmental load. The phase of clay mining (65.8%) is significantly impacting on all the investigated impact categories followed by brick moulding (24.8%) and brick roasting (9.4%) phases, respectively. Hotspots were assessed to identify potential for resource efficiency and circular economy at ABC bricks, Zimbabwe. It can be concluded that ABC is severely polluting the air with emissions above the Environmental Management Agency (EMA) standards for SO2, CO, PM and NOx thus putting kiln workers at risk of respiratory diseases. The calculated Air Quality Index (AQI) ranks CO as the most affecting pollutant with an average score of ∼600. Clay production efficiency was also determined, and an analysis revealed that extrusion and clamping stage contributed highly to the clay losses during brick moulding. Therefore, focus must be placed on these process steps to reduce raw material losses. Furthermore, an environmental waste (fly ash) was used in different weight percentage ratios of 10%, 20% and 100% to substitute clay. The increase of the fly ash content in the brick making process proved to significantly reduce the environmental load among the selected impact categories. ABC uses clay as its main raw material hence the high demand for clay. Strategies should include accounting of used clay daily and raw materials substitution. If ABC uses fly ash from its brick kilns and from other thermal power plant boilers to mix with clay in brick production, then the quantity of clay demanded will be reduced. Using fly ash will reduce rate of clay extraction while at the same time solving the problem of fly ash disposal in Zimbabwe. This circular option will ultimately result in reduced pit expansion, hence reducing top-soil loss and environmental degradation. It should not be disregarded that top-soil loss in turn affects food security. By adopting appropriate technologies, implementing resource efficiency, and designing circular economy patterns, the brick manufacturing sector in Zimbabwe may not only reduce production waste but also comply with enforced environmental protection legislation.