Sébastien Léger's path to venture capital began with nearly two decades at McKinsey, advising on cleantech and building decarbonization scenarios. Around 2020, driven by curiosity about the "next 40%" of technologies not yet at economic parity, he shifted focus toward startups. This exploration led to the co-founding of Slate Venture Capital, alongside two seasoned entrepreneurs and another investor, with a mission to fund and support the next generation of climate innovators.

From clothing to electronics, materials are everywhere—and they’re central to climate challenges. Léger sees advanced materials as pivotal in reducing emissions, increasing circularity, and enabling innovation in key sectors like batteries, wind turbines, and construction. Slate’s fund targets startups that help reduce, replace, or repair environmental impact, with materials playing a critical role across all three.

Slate focuses on Series A and B investments, writing checks between €4–15M and typically taking a 10% stake. Beyond capital, they offer strategic support through a unique network called the Collective Brain—a group of 80–100 experts in industrial scaling, manufacturing, and supply chains. Their investment decisions are based on:

• Climate impact: CO₂ and resource reduction potential.
• Commercial traction: Real (not R&D-subsidized) revenues and customer validation.
• Exit potential: Clear pathways to scale and acquisition.
• Team strength: Experienced founders solving real, validated problems.

Europe is home to around 2,000 climate startups, and Slate accesses them through a mix of inbound outreach, referrals, and direct participation in events like JEC World. Léger stresses the importance of long-term visibility, often engaging with startups well before they’re ready for investment.

While terms like “circularity” and “sustainability” are widely used, Léger emphasizes the need for substance over slogans. He encourages founders to frame their value proposition not just around technology, but around tangible customer and environmental impact—highlighting how their solution improves resilience, reduces waste, or supports biodiversity.

One of the key takeaways for startup founders? Focus on the problem, not the product. Léger advises against diving deep into technical details like "the best membrane or algorithm." Instead, founders should clearly articulate the problem they solve, the measurable impact they create, and their path to scale. Climate VCs want to hear about outcomes, not just engineering.

Regulation can accelerate climate innovation—but it’s not always reliable. Léger notes that while government support (especially in Europe) has driven demand in sectors like solar and wind, startups should aim to create business models that are sustainable with or without policy tailwinds.

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