A glowing green “liquid tree” in Kerala might offer a new tool in the fight against urban air pollution. Inside a 1,000‑liter bioreactor, billions of microalgae absorb CO₂ far more efficiently than ordinary trees—thanks to their rapid growth and unique carbon‑concentration mechanisms. Researchers and startups are testing how these living systems can clean city air, while also producing useful biomass for products like protein‑rich cookies. But despite the promise, experts stress that reducing pollution and planting real trees remain essential.