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Participation at the CILCA conference

7 September 2023

X International Conference of Life Cycle Assessment in Latin America (CILCA 2023)
Dates: 24-28 July 2023

On July 2023, URBAG participated at the X International Conference of Life Cycle Assessment in Latin America (CILCA 2023) with the presentation “Unlocking the potential of municipal solid waste compost for urban and peri-urban agriculture: Nutrient recirculation in metropolitan areas”. Juan David Arosemena presented his work which focuses on the potential of Organic Municipal Solid Waste (OMSW) compost to supply macronutrients, such as Nitrogen (N), phosphorus (P) and Potassium (K). It was the tenth edition of this conference, which is intended for users of tools based on life cycle thinking at different levels.

Unlocking the potential of municipal solid waste compost for urban and peri-urban agriculture: Nutrient recirculation in metropolitan areas

Abstract: Urbanization is exacerbating pressures associated with food demand and the generation of organic municipal solid waste (OMSW). Urban agriculture (UA) has emerged as a viable alternative for cities to tackle these issues by growing crops locally and utilizing compost from OMSW to recycle nutrients. This research aims to determine the potential of OMSW compost to supply macronutrients (nitrogen (N), phosphorus (P) and potassium (K)) required by UA crops, the benefits of substituting mineral fertilizer, and minimize organic waste from a life cycle perspective. To demonstrate this, the Metropolitan Area of Barcelona (AMB) serves as a case study, for which official georeferenced data on agricultural crops was analyzed to determine NPK demand, while centralized compost production was used to establish the compost supply. A life cycle assessment (LCA) was performed to determine the impacts of meeting the total yearly NPK demand with mineral fertilizer only and by replacing it with different OMSW compost supply scenarios (current and goal). Uncertainty was addressed by considering different rates of Nitrogen mineralization in soil and NPK content (minimum and maximum) from compost characterization of different OMSW facilities considered. According to the findings, the annual NPK demand for the AMB amounts to 1,519 tonnes of NPK (769 of N, 158 of P, and 592 of K). Hence, the current OMSW compost system can potentially supply 7% of the total NPK demand. However, if the compost production is increased in line with the waste management program goals of the AMB, the compost system can potentially triple the supply to 21%. LCA results indicate that the compost scenarios outperformed the mineral fertilizer only scenario, with impact decreases ranging from 33% (Mineral Resource Scarcity) to 78% (Fossil Resource Scarcity), when considering the scenario where 21% of the nutrient need is met by compost. Environmental savings were registered due to compost production, as the avoided burdens associated with preventing landfilling and energy recovery from biogas resulted in avoided impacts equal to 9% of the total net carbon footprint of the MSW system in the AMB. More savings were registered in eutrophication related categories when analyzing the comparison between the separated inorganic forms of NPK with what was recovered from compost. With this study, policymakers can take informed decisions based on a life cycle perspective, planning around the opportunities and benefits a city can provide in terms of nutrient circularity and the potential synergies between urban agriculture and municipal waste management.