Along the Arabian Sea, the Indian city of Jamnagar is a money-making machine for Asia’s richest man, Mukesh Ambani, processing crude oil into fuel, plastics and chemicals. It’s also where the billionaire is making his newest bet: a $10 billion investment in green energy.

On a swath of arid land to the city’s southwest, Ambani’s Reliance Industries Ltd. owns the world’s biggest oil refining complex. It’s a sprawling network of plants and pipelines that can process 1.4 million barrels of petroleum a day in an operation covering half the area of Manhattan. In fiscal 2021, Reliance generated about 45 million tons of carbon dioxide emissions from its own operations, which puts the company among the top such emitters in India, according to data on other companies tracked by Bloomberg. Much of that came from its Jamnagar refineries.

Next door, in a nod to a changing — and warming — world, Ambani is now building factories that make more environmentally friendly products like solar panels, electrolyzers, fuel cells and batteries.