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The Impact Equation
From solar cells in India to gigantic carbon sponges, with Paul Needham
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.
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64. Climate moonshots in Imperial's greenhouse
39:55||Season 1, Ep. 64Alyssa Gilbert sits in a rare seat in UK climate innovation: translating world-class science into ventures that can survive the messy reality of markets, regulation, pilots, and procurement. In this episode, Alyssa shares what Undaunted at Imperial College London looks for at the earliest stages, why credibility and communication matter as much as the tech, and what actually helps founders move from “tested in a lab” to “traction in the market”. We also get into the built environment: waste-to-materials, energy management, and the very real barrier of being “the first” in a traditional sector.
63. 63 Up: From prosthetics in war zones to sitting at the feet of Madeleine Albright
25:22||Season 1, Ep. 63
63. Revolutionising prosthetics in the developing world
32:53||Season 1, Ep. 63This episode is the first in our series with Save the Children Global Ventures, the impact investment arm of Save the Children, backing bold entrepreneurs tackling some of the world’s toughest challenges. In the first episode of the series, we’re joined by Fred Carpinteiro, Founder and CEO of Amparo Prosthetics, a company reimagining prosthetic care for people with limb loss across the world. Amparo is delivering lifetime prosthetic care across 6 continents, using smart technologies to dramatically improve comfort, fit, and user experience for lower-limb prosthetic users. With over 6,000 patients fitted in more than 45 countries, and products now used in 250+ clinics worldwide, Amparo is quietly building one of the most globally distributed prosthetic care platforms.
62. The next frontier of investment
42:34||Season 1, Ep. 62In our latest episode of The Impact Equation, we’re joined by Dominic Hofstetter and Ivana Gazibara from the Transcap Initiative, an NGO focused on developing and scaling systemic investing. Most of us start with a pool of capital and ask: what can this money do? Dominic and Ivana flip it: start with the challenge, diagnose the system, then “reprogramme” how money flows to multiple initiatives at once, so capital can actually shift outcomes, not just fund isolated projects. We talk about why “single-asset” investing struggles to deliver systems change, why place-based investing is close (but not always transformative), and their big idea: the “financial backbone”; an actor designed to orchestrate coalitions across philanthropy, public finance, investment capital, insurance and corporate commitments.
60. The Builder, the Analyst & the Financier: Carbon Markets Roundtable
37:53||Season 1, Ep. 60Carbon markets tend to trigger strong reactions. For some, they’re a vital bridge - a way to fund climate action at scale while the harder work of reducing emissions catches up. For others, they feel like a distraction, or worse, a way of outsourcing responsibility. So rather than arguing for or against them, we wanted to ask a different question: What would it take for carbon markets to actually work - with credibility and scale? In our latest Impact Equation roundtable, we brought together three people working on different parts of the system: Alastair is focused on data and transparency, Shannon is building projects on the ground, and Erika is making the sector investable for serious capital.
59. Hans Stegeman, Chief Economist of Triodos Bank: Rethinking Growth, Economic Systems and GDP
45:37||Season 1, Ep. 59What if the way we think about money is fundamentally wrong? In our latest episode of The Impact Equation, Rafi and Adam sit down with Hans Stegeman, Chief Economist at Triodos Bank - one of the few banks where sustainability isn’t a bolt-on, but the organising principle. Hans’s central critique is this: we haven’t just chosen economic growth - we’ve hard-wired it into everything. Our markets, financial returns, debt system, pensions, and public budgets all depend on the assumption that the economy must keep expanding. The problem is that this version of growth is material by design, and material growth always comes with ecological and social costs. His argument isn’t that progress is bad - it’s that we’ve confused progress with GDP. No amount of “green” investing can fix a system that structurally requires ever-greater extraction, consumption, and future growth just to stay standing. So what does he want to change? Hans calls for an economy, and a financial system, that is less dependent on growth, and that fundamentally success ought to be measured in wellbeing, resilience, and social outcomes, not just economic output. In this episode, Hans challenges us to question our assumptions and what we’ve accepted as “just how the world works”.
58. Elizabeth Boggs Davidsen, CEO, GSG Impact
38:59||Season 1, Ep. 58In this episode, GSG Impact CEO Elizabeth Boggs Davidsen joins the show to share her journey from being mentored by Madeleine Albright to leading global efforts in impact investing. Drawing on her formative years working in conflict zones like Sudan and Afghanistan, Elizabeth explains how those experiences shaped her belief that traditional aid isn't enough and that we need new models to drive change. She dives into her work pioneering a $1 billion "blended finance" fund in Latin America and her time in the Biden administration, before looking ahead to the 2026 launch of the "Impact Economy Index"—a new tool designed to spark a "race to the top" for countries prioritizing people and the planet. It’s a fascinating look at how capital can be a force for good, wrapped in some great advice for anyone starting a career in social justice.
57. Gaia Vince, Journalist & Author, Nomad Century
37:42||Season 1, Ep. 57This podcast episode features Gaia Vince, a trailblazing journalist, broadcaster, and award-winning author, discussing the profound intersections of climate change and human migration. In this episode, Rafi explores Vince’s career shift from science journalism to documenting the "front lines" of our changing planet, culminating in the urgent thesis of her latest book, Nomad Century. You can buy her book here: https://amzn.to/49b8ltk