Microalgae-based direct air capture systems for carbon dioxide emission reductions in developing megacities: A techno-economic and policy analysis

The dense urban population and subsequent residential activities significantly drive carbon emissions in megacities. Developing megacities face additional challenges due to technological gaps and financial constraints, making it difficult to implement effective CO 2 capture infrastructure. Existing solutions, such as conventional direct air capture (DAC) and urban tree planting, are often hindered by high energy demands and limited space, rendering them less practical for these densely populated megacities. This article analyses the state-of-the-art of microalgae-based DAC systems, including economic and policy assessments to aid in urban carbon sequestration in developing megacities. Microalgae-based DAC systems offer a sustainable alternative for urban carbon mitigation, achieving photosynthetic efficiencies 10–50 times greater than those of urban trees and capturing up to 1.83 kg CO 2 per kilogram of biomass. Integrating these systems into urban infrastructure can support carbon neutrality goals and generate economic value through biomass production and carbon credit sales, although detailed economic analyses are often lacking in the literature. A structured approach is essential for implementing microalgae-based DAC in developing megacities, focusing on technical feasibility, economic viability, and supportive policy frameworks. This integration not only supports achieving carbon neutrality and aligns with global climate initiatives but also promotes innovation and sustainable industrial growth.