Accelerated carbonation is a carbon capture solution that transforms waste carbon and residues into new materials.
Accelerated carbonation solutions are increasingly being seen as an important element in the blend of technologies essential to meeting net zero targets.
The significance of carbonation lies in that CO₂ is locked away for millions of years as limestone. 52 per cent of the world’s carbon is stored in carbonate rock. Accelerated Carbonation Technology (ACT) is able to control, manage and accelerate this process to become a real and ready carbon capture solution, transforming waste carbon and residues into new materials.
“2.01 billion tonnes of municipal solid waste are generated globally and 33 per cent of that is not managed in an environmentally sound manner,” said Paula Carey, co-founder and chief technical officer at Carbon8. “Because at least 37 per cent is dumped in either uncontrolled or controlled landfill, municipal solid waste is responsible for 5 per cent of global CO2 emissions. Less than 20 per cent of waste is recycled globally and the majority of this is in high-income countries.
“High-income countries, particularly those with limited land space generally consider Energy from Waste (EfW) a more sustainable management technique when combined with good recycling schemes. It reduces the mass of waste by 95% and provides the ability to manage the gaseous emissions more effectively than in landfill while providing electricity and district heating.”
Currently, EfW emissions are not included within measures such as the European CO2 trading Scheme (ETS) but there is increasing momentum to capture the CO2 from EfW plants. The AVR plant in Duiven in the Netherlands has been capturing CO2 for use in greenhouses for several years. In the UK, there have also been proposals to make CCS a requirement for EfWs by the mid-2020s.
ACT is a recognised means of permanent and safe CO2 storage. In the carbonation reaction, the chemical composition of the CO₂ changes and forms carbonates. In its most basic form, this can be represented in the equation: CaO + CO₂ → CaCO₃ / Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. “This demonstrates that it is a permanent and safe form of Carbon, Capture, Utilisation and Storage (CCUS) as this CO₂ can’t be released back into the atmosphere,” said Carey.
Exothermic reaction releases more energy than it consumes. Carbonation is an exothermic reaction, when the CO₂ changes to carbonate it is in a more stable state and energy is released. This means the carbonation reaction generates energy rather than requiring it. This is significant as it represents the only energy efficient CCUS solution.
ACT is recognised by the GCCA as one of the routes to NetZero, Carey says. “The potential of carbonation and re-carbonation of concrete is already being acknowledged by industry bodies. In the Global Cement and Concrete Association’s (GCCA’s) roadmap to NetZero by 2050, they specifically acknowledged the importance of carbonation and it lists six steps towards NetZero, five of which involve carbonation.”
