Cocoon Carbon is a materials company transforming waste from steel manufacturing into a vital and valuable ingredient for cement – decarbonising two hard-to-abate sectors at once.
Their beachhead is the US steel industry and their Series A will fuel their traction there – but the R&D is based in the UK, so we went to their west London lab to talk to Dr William Knapp, co-founder and Chief Science Officer at Cocoon.
We unpack Cocoon’s journey and uncover what investors such as 2150 VC see in their trajectory.
Q: What has fundraising been like?
The first round was tough, we spoke to about 100 investors before getting a term sheet.
More recently, it’s been even more competitive. Commodity-based businesses are harder to fund right now, especially with so much focus on AI.
That said, we’ve been fortunate. One investor tracked us for two years before leading our round, which made a huge difference.
Q: What advice would you give to angel investors backing early-stage startups?
I’d say focus on companies that are building something tangible and solving real-world problems. It’s easy to get caught up in hype cycles, but industries like infrastructure, materials, and energy have enormous, often underappreciated value. Just look at data centres, where the real value isn’t just AI software, but the physical systems behind it like cooling, hardware, and power.
The second thing is patience. In deep tech and industrial sectors, the journey is longer. Returns don’t come overnight, but the outcomes can be very significant if you’re willing to stay on course.
Finally, think about what expertise you can bring beyond capital. The best angel investors actively support founders, whether that’s through technical insight, industry connections, or helping navigate challenges.
Q: Who are your customers?
We work with two main categories, large global cement manufacturers, there are only about 10 major players worldwide, often with dedicated innovation teams. As well as ready-mix concrete manufacturers who operate with a much smaller, regional, and highly diverse businesses.
The contrast is huge. The large firms are structured and global, while ready-mix companies can range from small family operations to regional networks.
Q: How do you approach partnerships and sales?
Typically, we first get buy-in from senior leadership, VP or C-level, by communicating the overall vision.
Then we’re passed to technical teams who ask, “Does it actually work?” That’s where I come in to explain the science and application.
If they’re convinced, we move back up to leadership to negotiate agreements.
Q: What makes your business model compelling?
One key point: we don’t rely on carbon credits.
We operate with a price competitive product in a commodity market, which means there’s already huge demand. Our challenge is integrating across the value chain, from steel manufacturers and slag processors to cement producers.
We’ve done a good job of actually aligning that value chain and sitting in the middle of it, and owning our technology, aligning incentives and upgrading a low-value byproduct into something much more valuable.
Q: How has scaling the technology been?
Scaling has been a big journey.
We started with experiments producing about 1 kg of material, and then transitioned to the MPI, which is like 50 kilos, then 200 kilos in their other furnaces. And now we have this pilot plant in South Carolina that we’re doing the QC from.
It’s difficult because we’re working with molten materials and you can’t easily replicate industrial conditions in a lab. Having a pilot plant has been critical for generating enough material to validate our process properly.
We’re becoming more satisfied that we’re hitting those targets repeatedly now. Because of the great work that the engineers have done deploying the pilot system.
You have to integrate into the subcontractors on the steel manufacturer’s site, the slag handlers. And then you also have to sell that product to either a cement manufacturer or any mix operator.
Q: What led you to start Cocoon?
Initially, the idea came together with my co-founder Eliot who I met on the March cohort. He was drawn to solving big problems, like decarbonising steel and cement, and that resonated with me.
A lot of people advised me that a founding team should include someone with commercial experience, especially in startups. Eliot [as founder of healthtech startup Thriva] brought that, plus he’s just great to work with.
As we developed the idea, it became clear we needed an engineer. Carbon13 had plenty of talent, and that’s where Freddie came in. He aligned well with our mission and constantly asks challenging questions which is exactly what you want in a co-founder.
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