Economic resilience evaluation of wastewater resource recovery in Qatar's fertilizer market

Commercial fertilizers production represents a substantial contributor to greenhouse gas emissions when it comes to irrigated agriculture, and can, in some instances, hold the biggest share of emissions associated with the practice. With the intensification of climate change, energy intensive Haber-Bosh process, and declining phosphorus reserves, there is a need to adopt alternative and sustainable methods to meet farming nutrient requirements while reducing the burden on the environment, and while maintaining reduced economic costs. Using wastewater treatment plants byproducts, treated sewage effluent and sludge, can represent an effective mitigation strategy to reduce these emissions. In addition to that, sludge can be converted into soil amendment which can also substitute for conventional fertilizers. This study aims to evaluate the economic resilience of substituting commercial fertilizers with treated wastewater and sludge produced from wastewater treatment plants. The economic resilience of directing treated wastewater to the agricultural sector in the State of Qatar for fertigation purposes and converting sludge into biochar using pyrolysis modeled in Aspen Plus is compared with that of urea production. The economic resilience is assessed using the redundancy ratio as well as a price comparison under carbon taxation, thus internalizing the environmental cost of carbon emissions. Results indicate that treated sewage effluent and sludge biochar maintain stable redundancy ratios from 2017 to 2021, suggesting a dependable supply that could reduce reliance on traditional fertilizers. The introduction of a carbon tax, ranging from $0.03 to $0.1 per kg of CO2, markedly shifts cost competitiveness in favor of sludge biochar, highlighting its potential as an economically and environmentally superior alternative. the substitution of conventional fertilizers with treated sewage effluent and sludge biochar in Qatar presents a viable pathway to enhance agricultural sustainability. The study emphasizes the need for policy frameworks that support the integration of these practices, ensuring that Qatar's agricultural sector remains resilient in the face of environmental and economic challenges.