Viridor, Taunton, U.K., has announced that its energy recovery facilities (ERFs) have taken a significant step closer to becoming a fully “zero-waste-to-landfill”’ solution thanks to innovative technology that treats Air Pollution Control residue (APCr).

A ten-year contract has been signed with Carbon8 Aggregates Ltd. for the removal, treatment and recycling of APCr from Viridor’s ERFs in Exeter, Cardiff, Ardley and Peterborough, U.K., supplying around 25,000 metric tons of APCr from the four sites per year. The contract includes an option for a five-year extension at the discretion of those involved.

APCr is a byproduct of the filtering process to clean exhaust gases before they exit the facility through the flue stacks. Traditionally this material has to be disposed of in an appropriately licensed landfill site. Using its dedicated tanker fleet, Grundon Waste Management Ltd. will remove the APCr and transport it to Carbon8 Aggregates Ltd. The residue will be treated with waste carbon dioxide (CO2) in specialist mixer vessels. The CO2 reacts with the lime content of the APCr to form a carbonated compound similar to limestone which chemically immobilizes the heavy metals present in the APCr.

The treated residue is mixed with various binders and fillers prior to being pelletized with more CO2 to form a lightweight aggregate material ranging in size from 2 millimeters – 20 millimeters. The whole process means the resultant aggregate is carbon-negative, as the quantity of CO2 captured in the process is greater than the embodied CO2 in the cement and other materials and the power consumed in the production process, even accounting for transport impacts.

The aggregate has met the three key criteria of being a distinct and marketable product, that can be used in exactly the same way as virgin aggregates and can be used with no worse environmental impact than virgin aggregate.

This product has various applications but is principally used in the production of building blocks. Given its innovation and carbon negative credentials the aggregate has won numerous awards and has allowed Lignacite – one of Carbon8’s outlets for the aggregate – to develop the world’s first carbon-negative building block called the Carbon Buster.

This development will allow Viridor ERFs to continue in their pursuit of a zero-waste-to-landfill solution, and to ensure that output materials are fully recycled. The company is already committed to recycling the incinerator bottom ash from its ERFs.

Stuart Sim, Viridor EfW director, says “We’re excited to be amongst the leaders within the industry making this happen. We’re committed to giving the world’s resources new life, and seeing our residues recycled and become carbon-negative products within the construction industry really demonstrates clear progress on resource efficiency in this important and growing part of our sector.”

Richard Skehens, chairman of Carbon8 and former CEO of Grundon Waste Management says, “We are
delighted to have been awarded the contract with Viridor. The investment by Grundon into the Carbon8 Aggregates business recognized the huge potential for recycling APCr into aggregate, thereby providing a genuine zero-waste-to-landfill option. This contract asserts Carbon8’s position as the market leader in APCr recycling.”

During 2015, Carbon8 will be constructing a new APCr facility in Avonmouth, U.K., to support this ten-year contract. The facility is expected to be operational by the end of the year and is the first element of Carbon8’s plans to build three more plants in the U.K. by December 2016.