Concrete is responsible for roughly 8% of global CO₂ emissions. Now a UK partnership has shown it can be carbon-negative.
Holcim UK and Canary Wharf Group (CWG) have produced what they’re calling the UK’s first net-zero concrete, using biochar derived from spent coffee grounds collected from Canary Wharf coffee shops and coppiced hardwood.
The Numbers
The initial trial pours in April 2025 achieved an 80% reduction in net Global Warming Potential (GWP A1–A3) compared to traditional CEM I concrete — landing at 69 kgCO₂e/m³.
By September 2025, further optimization of the coffee-biochar mix pushed the results into carbon-negative territory: a projected net GWP of -14 kgCO₂e/m³ when fossil emissions and biogenic carbon storage are assessed together.
That’s not a lab result. Those were full-scale pours — two-metre-deep raft slabs on CWG’s Bank Street site.
How It Works
When biochar is mixed into concrete, the carbon absorbed by trees and coffee plants during growth gets locked into the building material itself. The concrete becomes a permanent carbon sink.
The development involved a collective of industry heavyweights: Arup, Ramboll, Thornton Tomasetti, and researchers from Queen’s University Belfast and the University of Cambridge.
Another trial mix used graphene, achieving 50%+ carbon reduction while delivering higher strength and improved durability — potentially meaning less concrete needed per application.
Why This Matters for CDR
Biochar in construction is an emerging carbon removal pathway that solves two problems at once: it creates durable storage (concrete lasts centuries) and uses waste streams (spent coffee grounds, coppiced wood) as feedstock.
The materials will be monitored for two years by CWG’s expert collective, including Skanska and Arup, to establish verified long-term performance data. If the results hold, this could open a new market for biochar beyond soil amendment.
The global concrete industry pours roughly 14 billion cubic metres per year. Even modest biochar adoption at this scale would represent meaningful carbon removal.
Source: Holcim UK Press Release · Aggregates Business