Valorization of cheese whey wastewater to achieve sustainable development goals

While several studies have focused on managing cheese wastes for bioresource recovery in developing countries, assessing the techno-economic feasibility, carbon emissions, and sustainability performance of such systems is still to be determined. This research gap was addressed by designing a reliable cheese whey wastewater (CWW) management system that could recover biogas and biochar, followed by estimating the associated profits, net present values, and payback periods. Implementing this system to treat 1 m3 CWW with a chemical oxygen demand (COD) of 56.2 g/L could generate bio-CH4 (8.71 m3), biochar (1.21 kg), pyro-oil (1.99 kg), and syngas (0.31 kg) while self-consuming about half the energy produced. The revenues of carbon credit, COD shadow price, electricity, and biochar could maintain a 6.1-year payback period and a 10.15 % internal rate of return. The environmental benefits could recoup the annual expenses accompanied by biogas/biochar utilization in agricultural, energy, and field applications, demonstrating that the system's profitability criteria were less sensitive to variations in operational costs. Although the CO2-equivalent emissions represented significant environmental burdens, the green credit of biogenic CWW could endorse the life cycle assessment's mid-point and end-point categories. Ensuring clean water and affordable energy, recovering biochar as an enriched soil amendment, and enabling policies/finances by the proposed CWW valorization approach could fulfill sustainable development goals 6, 7, and 13 in low-income nations. Future studies are required to optimize the anaerobic digestion and pyrolysis operating parameters using machine learning techniques, reducing the running costs and improving the minimum selling prices of biofuel recovery from CWW.