In January I sat down with Elliot Brooks, Co-founder and CEO of climatetech startup Cocoon to discuss the company's journey, the challenges of scaling a hardware climate startup, and how they are tackling one of the biggest contributors to global emissions – concrete.
In our conversation on the Angel Insights podcast, Elliot shared valuable insights into how Cocoon is repurposing industrial waste to create a low-carbon cement substitute that can drastically cut CO₂ emissions.
Concrete is the foundation of our modern world – literally. It is the second most consumed material after water and forms the backbone of our cities, roads, and infrastructure. Yet, few people realise that concrete production is one of the most significant contributors to global CO₂ emissions. Cement, a key ingredient in concrete, accounts for 90% of the emissions associated with concrete and is responsible for roughly 7-8% of global greenhouse gas emissions.
Enter Cocoon, a startup emerging from the Carbon13 program, which is on a mission to decarbonise concrete by upcycling industrial waste into a low-carbon cement substitute. By leveraging byproducts from the electric arc steelmaking process, Cocoon can replace up to 30% of traditional cement used in concrete, achieving an astonishing 90% reduction in CO₂ emissions per ton of material compared to conventional cement.
How Cocoon is solving a multi-billion-ton problem
Cocoon’s innovation comes at a time when the world desperately needs scalable solutions to curb industrial emissions. The key to their approach is finding value in industrial waste streams. Their process takes steel slag – a byproduct that is often discarded or used as low-value aggregate – and transforms it into a high-value supplementary cementitious material (SCM).
This is a win-win scenario for
Steel plants: Cocoon provides a revenue share model, converting a cost-heavy waste disposal process into a profit center.
Concrete producers: Cocoon offers a cost-competitive, high-performance cement alternative, eliminating the need for carbon-heavy traditional cement.
The environment: by reducing cement use, Cocoon helps tackle one of the most pressing climate challenges at scale.
As Elliot put it during our conversation: “We’re taking something that is currently considered waste and turning it into a high-value product that dramatically reduces emissions. It’s a win-win for everyone.”
Scaling up: a clear path to impact
Cocoon’s journey showcases how deep tech and industrial innovation can create both environmental impact and substantial financial upside. But companies like Cocoon don’t emerge overnight—they require early-stage capital and deep domain expertise to succeed.
That’s where Carbon13’s SEIS fund comes in. Carbon13 specializes in launching and scaling startups that can achieve at least 10 million tons of CO₂ savings within 10 years. By investing in the fund, investors gain exposure to a portfolio of high-impact, high-growth startups like Cocoon—businesses tackling the most pressing climate challenges while positioning themselves for strong returns.
As Elliot highlighted in the podcast: “Hardware startups take time, but if we move fast and get this right, the impact will be massive. The demand is there—we just need to scale.”
The future of concrete is low-carbon
In five years, Cocoon envisions a world where millions of tons of CO₂ emissions are avoided through widespread adoption of their technology. The global construction industry is waking up to the reality that sustainability and profitability must go hand in hand—and Cocoon is poised to be at the center of this transformation.
For investors looking to back innovative climate solutions with strong commercial potential, Cocoon’s story is proof that hardware-driven climate startups can move fast and scale big. And by investing in Carbon13’s SEIS fund, you’re not just betting on one company—you’re backing an ecosystem designed to create the next wave of world-changing climate tech startups.
Learn more about Cocoon on its website
Listen to our conversation on the Angel Insights podcast
Find out more about the Carbon13 SEIS Fund.
The Carbon13 SEIS Fund
Our latest investment opportunity is an SEIS fund focused on returns with purpose, building and backing early-stage businesses addressing Earth’s vital life support systems.
This fund, Carbon13's 7th SEIS fund portfolio, will invest in pre-seed companies that are expected to be eligible for SEIS, and enable investors to claim a suite of tax reliefs such as 50% income tax relief on up to £200,000 invested, and 50% exemption from capital gains that arise in the same year. Tax reliefs are subject to status and change.
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The Access EIS Fund
Our fund co-invests with proven angel investors to build large portfolios of hand-picked companies for our investors. It’s a high risk investment, and we can’t guarantee that every startup will be a unicorn, but we’re confident that our approach is the smartest on the market. Even better, we can show you the data to prove it.
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