M-LS by O.C.O Technology: a carbon-negative limestone aggregate created with residues from waste to energy residue

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United Kingdom
Brandon, Avonmouth, Leeds
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When waste to energy plants process non-recyclable waste to generate energy, they create a by-product called air pollution control residue (APCr) – a hazardous waste in the form of solid ash. O.C.O Technology has pioneered Accelerated Carbonation Technology (ACT), to recycle this residue into M-LS - the World's first carbon-negative aggregate for construction.

The process involves:

  1. Blending APCr and other wastes to form a reactive mixture
  2. Stabilising the reactive mixture with liquid CO2 and water
  3. Combining the stabilised mixture with binders and fillers
  4. Pelletising the combination
  5. Curing the pelletised combination to create the M-LS.

The UN's 6th Global Environmental Outlook for the pan-European region recognises the O.C.O Technology, stating that such "aggregates, which have a structure similar to natural limestone, meet European ‘end of waste’ regulations and materials performance standards, and make a demonstrable contribution to the developing European circular economy." For more information, view O.C.O Technology's website here.

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The construction industry uses this aggregate to produce masonry units, precast concrete, ready-mix concrete, screed, and other products.

Every tonne of this material saves 1.4 tonnes of non-replaceable natural aggregate.  The carbon-negative aggregate captures more CO2 than is emitted during its manufacture.  Every one thousand tonnes of M-LS permanently captures the same amount of carbon dioxide as 4000 trees in a year.

O.C.O Technology has developed a network of UK facilities to recycle 150,000 tonnes of APCr each year, with factories in Avonmouth, Leeds and Suffolk.