In-depth analysis of nitrogen flow in urban system in Low Income Countries: The case of Yamoussoukro in Côte d’Ivoire

Abstract

In-depth analysis of nitrogen flows (NF) using Material Flow Analysis (MFA) was curried out to assess the impact of the current urban sanitation system in the city of Yamoussoukro in Côte d’Ivoire. The aim of the study was to develop resource recovery mitigating option for a sustainable management of the sanitation system. MFA simulations were improved by integrating R.3.0.1 and STAN 2.5 in the research framework. With a context of limited data, NF were efficiently assessed using Monte Carlo simulation in R with 1,000 iterations, based on probability distribution and statistics of input parameters. About 905 tons of nitrogen per year are discharged from the sanitation system including waste water, solid waste and faecal sludge. The discharged nitrogen degrades the urban environment and increases human exposure to health risk. To address sustainable mitigation measures, three resource recovery sanitation technology scenarios were developed. The first scenario integrates lagoons and composting plants while the second and third scenarios include unplanted and planted drying beds respectively together with co-composting. The first scenario allows potential reuse in agriculture, of 89.3% (808.6 tons) of total nitrogen produced per year which would otherwise be discharged to the environment. This scenario was thus found to be the most ecologically relevant and low-cost option. The study highlighted relevant statistical estimations, reduction of time and energy consumption in simulations, MFA potential for environmental risk mitigation and  improved agriculture by nutrient recovery. This productive urban waste management option could be helpful for urban planners in developing cities.

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Keywords: Material Flow Analysis; Nitrogen Flows; Urban Waste Management; Monte Carlo simulation, Côte d’Ivoire, Sensitivity analysis