To capture CO2, just add calcium silicate

BusinessGreen: Carbon 8 Systems claims to have found a way to permanently capture and store carbon emissions whilst treating hazardous waste ash. How does this work?
Dr Paula Carey: It's actually a very simple process called carbonation. Industrial waste, such as the ash you get from municipal incinerators, contains calcium silicates which react vigorously with CO2 to produce calcium carbonate, or limestone as it is more commonly known. This process occurs naturally but because of the relatively low concentrations of CO2 in the air the reaction can takes years. We've developed a process based around the mixture of calcium silicates, water and the right concentration of CO2 that speeds the reaction up so it takes about 15 minutes. We have some patent coverage for the process and are working to commercialise the technology.

How do you see this process being applied practically?
The most obvious application is for incinerators where you are producing CO2 from the chimney while also producing the ash you need to capture much of that CO2. Applying the technology to an incinerator means you would not only cut carbon emissions, the process would also treat the waste ash and make it less hazardous and the net result is limestone which can be reused as aggregate for the construction industry.

How big a reduction in carbon emissions could this technology deliver? We estimate that 70,000 tonnes of ash would absorb between 10,000 and 20,000 tonnes of CO2. Beyond that the only constraint on how widely you could apply the technology would be the availability of the ash and the demand for the aggregate.

What is the business case for incinerator operators and waste management firms to use the technology?
By treating the hazardous ash at the same location as it is created you can save a huge amount in transport and treatment costs. On top of that you can sell the aggregate that is created as the end product for £20 to £30 a tonne. From Carbon 8's perspective we can envisage a business model where we are paid to take the ash off an incinerator's hands, generate carbon credits by capturing the CO2 and then sell on the aggregate.

How close is the company to commercialising the technology?
The biggest challenge is capturing the CO2 from the chimney, though carbon capture systems for doing that are absolutely feasible and we are working on developing the technology. When it comes to using the process to just treat the hazardous ash we can simply use bottled CO2 and we had a field trial last week using that process, following up on trials that we did several years ago. We are also working with a waste company to get a full pilot using bottled CO2 up and running in the next two to three months.

Realistically how big an impact could this technology have on UK carbon emissions?
We are talking about saving millions of tonnes rather than tens of millions of tonnes due to the limitations in terms of availability of ash and demand for the end product. But the potential application of the technology is still huge. It would be expensive retrofitting any system to existing incinerators, but we are going to see more incinerators built and we are already talking to waste firms about this technology being included in their designs.

Could it also be applied to biomass energy plants as well as incinerators?
Absolutely. What we are looking at is a genuinely carbon negative process. If you consider the advantage of biomass projects are that they are carbon neutral as emitted carbon had been absorbed as the biofuel grew then adding a technology that captures the CO2 when it is emitted and takes it permanently out of circulation is a carbon negative process.

About Dr Paula Carey

Dr Carey is the commercial director of Carbon8 Systems as well as an academic a t the University of Greenwich. She has a research background in geology and natural materials for the construction industry.

She and Dr Colin Hills, a fellow geologist from Greenwich, formed the company in 2006.

You can see a video of Dr Carey explaining the carbonation process in more detail here.