Comparison of local and centralized biowaste management strategies – a spatially sensitive approach for the region of Porto (narrated slide show)

<p>The increasing concern with carbon and nutrients cycling creates a need for cost-effective, straightforward and environmentally sensible biowaste management strategies. Centralized systems have struggled to comply with those needs and decentralized systems treating waste at source promise local nutrient circularity and increased resource sovereignty. The large scale performance of decentralized systems remains unclear, especially concerning the local sink capacity to assimilate the treatment products. This study aimed to compare centralized and decentralized systems for the region of Porto and assess whether the creation of additional urban farms can reduce costs and impacts. Spatial analysis was used to assess waste generation, compost bin locations, peri-urban and potential urban farmland available, and collection and driving requirements. The carbon footprint of different scenarios was determined using life-cycle assessment. The results show that localized composting lead to cost savings over centralized systems and that most districts had limited sink capacity for compost application. Although additional urban farms added significant sink capacity, their impact on cost and carbon footprint were little. The carbon footprint of centralized systems was heavily dependent on the type of grid electricity and the productive use of waste products outside city boundaries, with anaerobic digestion being the most climate-friendly option overall in the future. Localized composting can be improved through better home composting practices and cities may benefit from tailoring the treatment systems to specific districts, creating additional jobs while reducing cost and climate impacts overall.</p>

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