Garden refuse composting as part of an integrated zero waste strategy for South African municipalities.
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Garden refuse has been seen to constitute a significant proportion of the total waste stream received at landfills in the eThekwini Municipal Area (EMA). With the growing demand for conserving “precious landfill airspace” as a result of limited availability of land for new landfill development, there is a shift in the mindsets of landfill operators to adopt alternative methods of treatment other than the traditional way of landfilling. As a result composting of green waste stream was seen as the most appropriate treatment solution as not only would there be a direct landfill airspace saving but the added environmental, economical and social sustainable benefits to the city. The first South African Waste Summit saw the signing of the Polokwane Declaration i.e. “Reduce waste generation and disposal by 50% and 25% respectively by 2012 and develop a plan for ZERO WASTE by 2022”. Hence, the push for composting to try and achieve waste reduction to landfills. The Dome Aeration Technology (DAT) is an advanced treatment option for aerobic biological degradation of garden refuse (Mollekopf et al, 2002, Trois and Polster, 2006). The originality of the DAT system is the use of passive aeration brought about by thermal driven advection through open windrows which is induced by thermal differences between the composting material and the ambient atmosphere (Polster, 2003). Previous work on organic waste composting using the DAT on a small scale showed that good quality compost was attainable within 6 weeks of composting (Moodley 2005). This study offers comparative performances between DAT system and Traditional Turned Windrows (TTW) in composting garden refuse and recommending the most appropriate system for integration into existing landfill operations. Full scale windrows were constructed for each system at the Bisasar Road Landfill Site in Durban, Kwa-Zulu Natal to evaluate the influence of climate, quality of compost, operational requirements and feasibility. The process monitoring for the DAT windrow showed that temperatures reached thermophilic ranges within a week of composting which confirms that of the German studies. Waste characterisation of both input and output materials are discussed for both systems with recommendations on the most practical and appropriate system applicable to that of an operational landfill are drawn. The study further concludes with potential uses of the composted garden refuse within landfill sites and its contribution to “closed loop” landfilling yet within an integrated waste management plan.