Determination of the Least Impactful Municipal Solid Waste Management Option in Harare, Zimbabwe

Abstract

Six municipal solid waste management (MSWM) options (A1–A6) in Harare were developed and analyzed for their global warming, acidification, eutrophication and human health impact potentials using life cycle assessment methodology to determine the least impactful option in Harare. Study findings will aid the development of future MSWM systems in Harare. A1 and A2 considered the landfilling and incineration, respectively, of indiscriminately collected MSW with energy recovery and byproduct treatment. Source-separated biodegradables were anaerobically treated with the remaining non-biodegradable fraction being incinerated in A3 and landfilled in A4. A5 and A6 had the same processes as in A3 and A4, respectively, except the inclusion of the recovery of 20% of the recoverable materials. The life cycle stages considered were collection and transportation, materials recovery, anaerobic digestion, landfilling and incineration. A5 emerged as the best option. Materials recovery contributed to impact potential reductions across the four impact categories. Sensitivity analysis revealed that doubling materials recovery and increasing it to 28% under A5 resulted in zero eutrophication and acidification, respectively. Increasing material recovery to 24% and 26% under A6 leads to zero acidification and eutrophication, respectively. Zero global warming and human health impacts under A6 are realised at 6% and 9% materials recovery levels, respectively.

Framework for Decentralizing Municipal Solid Waste Management in Harare, Zimbabwe

“…The options for treating these MSW fractions generated should be focused on AD of biodegradable MSW fraction, recycling of at least 20% and incineration of at most 80% of the non-biodegradable fractions. The focus on the mentioned MSW treatment is informed by study findings from [35] which identified the option incorporating AD of organic fraction of MSW, at least 20% and at most 80 percent recycling and incineration of the non-organic MSW fraction generated in Harare respectively being the least environmentally impactful option. Composting of the biodegradable MSW fractions could also be considered after AD due to the better environmental performance and overall edge of AD over composting resulting from its renewable energy production capabilities and other associated benefits noted by [36].…”

“…For example, in Harare only 9.6% of the MSW generated in Harare is recycled translating to only 23,000 tons of the over 467,000 tons generated. At least 20% of the nonbiodegradable MSW equivalent to at least 56,000 tons has to be recycled [35] thus double the current recycling level. To meet this target therefore, recycling could be done at household, institutional and community level.…”

“…The incineration of MSW generated in Harare is likely to be done at institutional, community or industrial scale. In addition to the better environmental performance of incinerating MSW generated in Harare compared to its landfilling observed by [35], authors in [37] reported the suitability of MSW generated in Harare to be treated via incineration with a lower heating value of between 10100 kJ/kg and 9320 kJ/kg giving an estimated 3.8 ×106 GJ per annum. The lower heating value and incineration efficiency thus could be enhanced by the source separation of biodegradable MSW.…”

“…Annual MSW and specific MSW fraction generation figures for Harare City and its surrounding ULAs[35] …”

Assessment of the Municipal Solid Waste Transfer Stations Suitability in Harare, Zimbabwe

“…WTS apart from their costs abatement capabilities they could possibly bring about reduced environmental impacts of future MSWM systems that could be implemented in Harare city, Chitungwiza, Ruwa, Epworth and Norton. In [22], the authors observed that the recycling of atleast 20% of the recoverable materials contributes to significant reductions of environmental impacts (acidification, eutrophication, human health and global warming) of MSWM options that could be earmarked for future implementation in Harare city, Chitungwiza, Ruwa, Epworth and Norton. WTS have largely been reported that they can act as platforms for recycling and materials recovery hence their incorporation in future MSWM systems as platforms for recycling and materials recovery will result in reduced environmental impacts.…”