This year’s National Recycling Award for Best Recycled Product went to Carbon8 Aggregates. Andrea Lockerbie looks at why
Carbon8 Aggregates (C8A) has taken a novel laboratory-based technology, known as Accelerated Carbonation Technology (ACT), through to commercial reality, producing a lightweight, carbon-negative aggregate from Air Pollution Control residues (APCr). It has done this by developing the first APCr recycling plant in the UK and Europe, located at Brandon in Suffolk. The plant is permitted to recycle 18,000 tonnes of APCr per year, which solves the long-standing problem of Energy from Waste (EfW) plants being unable to deliver ‘zero waste to landfill’.
The judges said: “This is an impressive technology development. It demonstrates real innovation, building on a project trial and offers real export potential.”
During the mass burn process, a typical EfW plant will produce 10,000 tonnes of APCr, which is approximately 3% of the waste input by weight. APCrs are classified as a hazardous waste. The residues are produced by the injection of lime into the flue gas to react with the acidic gases and capture the particulates in filter bags.
Currently, the vast majority of the APCr produced in the UK - approximately 150,000 tonnes - goes to landfill either via treatment with water, treatment with waste acid, washing or directly into long-term storage in salt mines.
C8A has developed the only full recycling option commercially available in the UK. The patented Accelerated Carbonation Process treats the APCr by reacting the calcium and magnesium compounds in the waste with carbon dioxide to form carbonates, thereby permanently capturing carbon dioxide. The formation of the carbonates helps bind the fine-grained particles of APCr together and also chemically stabilises heavy metals in the waste by reducing the pH of the system, thereby reducing the leaching of the problematic metals such as Lead or Zinc.
After initial treatment with waste carbon dioxide, the APCr is mixed with cement, sand and water and formed into pellets, again in a carbon dioxide environment, so that further carbon dioxide capture takes place.
A tonne of APCr will permanently capture around 10% of its weight of carbon dioxide depending on the EfW plant source. The aggregate manufacturing process produces no emissions and no waste, uses water obtained from rain water harvesting and uses waste carbon dioxide captured, by Air Liquide, from the processing of sugar beet.
C8A believes its aggregate is the only product recycled from APCr with End of Waste status. All the production is currently being used in the manufacture of dense and medium dense blocks at the Lignacite blockworks where the C8A plant is located. In the future it hopes to build further plants and be able to modify the process to use waste materials as replacement for the sand and cement, as well as capture carbon dioxide directly from flue gas.
Paula Carey, technical director, Carbon8 Aggregates
“I think we won the award because our product is really innovative and it solves a nationwide problem in the waste management industry. It’s an aggregate that is made from the waste from EfW plants and it means that EfW can now be ‘zero waste’.”
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