Holcim UK has created an innovative concrete mix using recycled coffee grounds to support a 12m high sculpture of a blue whale just unveiled in London’s Canary Wharf.
The Whale on the Wharf (Skyscraper) by StudioKCA was created from plastic waste recovered from the Atlantic and Pacific oceans and has been sited in a wet dock in Canary Wharf’s Wood Wharf district.
But the four-storey high structure required firm counter-weight foundations to keep it and its frame in place.
So, Canary Wharf Group (CWG) turned to Holcim UK to develop an innovative concrete to support it and the circular economy message the sculpture embodies.
Holcim experts devised a concrete mix containing biochar sourced from coppiced UK fast growing hard woods and spent coffee grounds from Canary Wharf’s cafes and restaurants to form the structural supports to anchor the sculpture in place.
Five loads (32 cubic metres) were mixed and batched at Holcim UK’s Battersea Readymix plant before being delivered to site. A specialist civil engineering diving company, DiveCo Marine Limited, then pumped the product into place under the water’s surface. The new sculpture was unveiled to the public on the 9th April.
Holcim UK, working with counterparts at the Holcim Innovation Centre in Lyon, has been testing the use of biochar in readymix concrete for a number of years.
Biochar is widely used in agriculture and is produced by heating biomass, typically sourced from surplus wood, at temperature and in the absence of oxygen, through a process called pyrolysis. The result is a black carbon rich material like charcoal. Similarly, spent coffee grounds can be turned into a carbon rich biochar when treated through pyrolysis.
The process of creating biochar can help prevent the formation of greenhouse gases which are generated when biomass waste (and used coffee) is sent to landfill and naturally degrades, releasing carbon dioxide and in some instances methane.
When biochar is added to concrete, the sequestered carbon is removed from the carbon cycle for a very long period of time - in a way, the carbon is ‘trapped’ and prevented from returning into the atmosphere as CO2. Through using biochar you also use less virgin or primary aggregate preserving natural resources for longer, as well as less waste being sent to landfill or incinerators.
The mix produced to support the whale sculpture was formulated with carbon-reducing limestone fines and GGBS. With the addition of the 'Bio-Expresso' biochar, the embodied carbon was able to be lowered by a further 66%, yielding an impressive next-generation concrete with a projected net Global Warming Potential or GWP (A1-A3), as low as 69 kg CO2e/m³.
With the two technologies combined, the total carbon reduction (A1-A3) is about 79% compared to a traditional CEMI concrete mix.
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