Analysis and Modeling of Wastewater Reuse Externalities in African Agriculture

Abstract

Wastewater reuse has been identified to alleviate freshwater scarcity, improve crop yield and sustain the environment. This study analysed and modeled wastewater reuse externalities in the context of African agriculture. Data were retrieved from FAO-AQUASTAT (2015). Descriptive statistics and correlation analyses were performed to analyse the potentials of wastewater and determine the relationship between the environmental implications of treated effluent respectively. Cost-Benefit Analysis (CBA) and Stochastic frontier cost functions were modeled for estimating the economic/environmental trade-offs of wastewater reuse and costs of wastewater treatment. The descriptive results indicated that Northern Africa, which is the most vulnerable region, has the greatest potentials of wastewater reuse. The quantity of effluent from treatment plants was inversely proportional to the treatment capacity between Northern and Southern Africa. Correlation analysis results show that "area of land salinized" had a highly positive significant correlation with the quantity of treated wastewater used (r=0.69). CBA was modeled to account for treatment cost, health cost, cost of soil reclamation, aquifer damage cost, increased crop yield and aquifer recharge. A conceptual Stochastic Frontier Model (SFM) was also developed in this research as no previous studies took into account inefficiency parameters (negative externalities) accompanied with wastewater reuse. African regions living above water-poverty line must however not wait till when freshwater will become a limiting resource. The significance of salinity in this study calls for the use of appropriate agronomic practices to remediate saline soils. Stochastic frontier is recommended to be applied to empirical data for further studies considering the valuation of externalities. In conclusion, this study puts wastewater on the policy agenda by emphasizing its impacts in agriculture.

Keywords: Wastewater, Africa, Externalities, Cost-benefit analysis and Stochastic frontier model.