In this episode, we go deep into chemistry and mining with Paul Needham, CEO of ARCA, a company using carbon mineralisation to turn mine waste into giant, permanent carbon sponges. In 2025, Arca signed a 10-year deal with Microsoft to remove 300,000 tonnes of carbon from the atmosphere. Certain rocks naturally react with CO₂, pulling it out of the air and locking it away forever as stone. ARCA has found a way to massively accelerate that natural process, transforming mining tailings from an environmental liability into a climate solution. Paul's no stranger to scaling impact: he previously built Simpa Networks, bringing pay-as-you-go solar to hundreds of thousands of people in rural India. In this episode we learn about scaling pay-as-you go solar in India and how carbon mineralisation turns mining waste into carbon removal at scale.