Innovations and strategies for sustainable wastewater-integrated microalgal biodiesel production

• Biodiesel Production from third generation feedstock Microalgae. • Wastewater-driven microalgae cultivation lowers costs and enhances sustainability. • Transesterification using reusable heterogeneous catalyst is discussed. • Hybrid systems and strain optimization emerge as scalability breakthroughs • Various techniques for enhanced lipid extraction using cost efficient methods. The increasing need for developing a sustainable and renewable fuel has been one of the prime concerns in the world over the past few decades. This review proposes that microalgae have the ability to be scalable, cost efficient, eco-friendly and sustainable for biodiesel production simultaneous contributing to the treatment of wastewater. This integrated framework highlights new business opportunities for energy, wastewater, and bioproduct industries, where cost reductions from the current US $4–6 per liter to projected values near US $1.5 per liter could make microalgal biodiesel increasingly competitive with fossil fuels that can be sufficient for large scale industrial application. This review synthesizes progress in cultivation strategies, lipid extraction methods, and scale-up innovations, while outlining future directions such as wastewater-driven strain optimization, development of hybrid cultivation systems, and resolution of techno-economic and policy barriers essential for industrial deployment. Ultimately this review focuses on an array of approaches to accomplish reasonably priced, eco-friendly and sustainable way to produce biodiesel from microalgae and reduce the greenhouse effect based on critical analysis.