CO2 Solutions and COAL21 Ltd say tests of CO2’s enzymatic technology have indicated that the process could be applied to coal-fired power plants for post-combustion carbon capture.

CO2 is a company focused on enzyme-enabled carbon capture, while COAL21 operates the COAL21 Fund to support the pre-commercial demonstration of low emission coal technologies (such as carbon capture and geological storage).

The technology developed by CO2, according to the company, lowers the cost barrier to carbon capture, utilisation and sequestration (CCUS), positioning it as a viable CO2 mitigation tool, as well as enabling industry to derive profitable new products from these emissions. The company has built an extensive patent portfolio covering the use of carbonic anhydrase, or analogues thereof, for the efficient post-combustion capture of carbon dioxide with low-energy aqueous solvents.

A study, conducted over the past 18 months by PROCOM Consultants, examined the performance of CO2’s enzymatic technology when applied to coal-fired power plants for post-combustion carbon capture. The methodology applied by PROCOM in this study included the development of rate-based models for absorber/stripper, the validation of the enzymatic technology’s heat/mass balance and the key performance parameters and model integration of the enzymatic technology in coal-fired power plants.

The simulation software used was Aspen Plus, with two reference cases modelled US DoE SC reference case (B12B) and a Supercritical (SC) power plant from Queensland, Australia.

In both cases, the performance of the CO2’s enzymatic technology was compared to a known advanced amine technology (Cansolv). CO2 provided two unoptimised process books of its enzymatic technology at different scales based on its ProTreat® models to the PROCOM study.

The main study conclusions reached by PROCOM Consultants, according to the companies, include:

• The enzymatic technology appears well suited to coal-based industrial plants (eg iron and steel, cement) in particular for its tolerance to the oxides in flue gas and appears to have significant environmental and operational advantages over alternative post-combustion capture technologies, such as advanced amine technology;
• By using low-grade, residual thermal energy in the form of hot water, the modelled unoptimised enzymatic solvent performance yields marginally more electricity in the context of an existing coal-fired power plant in Australia compared with the advanced amine process.
• The enzymatic technology’s tolerance to SOx and NOx contaminants in the flue gas of low-sulphur coal-fired plants provides it with an estimated 30% capital expenditure (capex) advantage relative to the advanced amine technology since there is no requirement to polish this flue gas down to single digit parts per million using Flue Gas Desulphurisation and Selective Catalytic Reduction;
• Modelling has confirmed that SC coal-fired power plants in Australia have sufficient residual low-grade heat to give the enzymatic technology a slight power efficiency advantage over the advanced amine technology. Moreover, the likely further optimisation of the enzymatic technology would extend this advantage.
• In addition to being able to use residual, low-grade heat in the form of hot water as its thermal energy, the enzymatic technology could also tap into renewable energy sources such as geothermal and solar thermal sources for its energy requirements, options which are more challenging to the advanced amine technology which requires steam, according to the companies. Tapping into these sources of external renewable heat would potentially significantly reduce the thermal parasitic load of carbon capture;
• The PROCOM study confirmed the enzymatic process minimises the environmental footprint through the use of an ionic (non-volatile) and environmentally benign solvent;
• The enzymatic technology converts a portion of the oxide contaminants in the flue gas (SOx and NOx) into high-value sulphates, sulphites, nitrates and nitrites, which accumulate over time in the solvent. As a result, the periodic bleed of this nontoxic solvent creates an opportunity to recover valuable materials, such as potassium nitrate fertiliser, which reduces the overall operating cost of the enzymatic technology. This approach is not available to the advanced amine technology, and;
• Through expected optimisation, the enzymatic technology could be more favourable than amine-based processes regarding capex and overall energy requirements, and very favourable to amine-based processes regarding aspects related to management of oxide flue gas contaminants.

Richard Surprenant, CO2 Solutions’ Chief Technology Officer, said: “The detailed report prepared by Procom Consultants highlights the low-cost and environmentally friendly qualities of our process. It further confirms the major paradigm shift that the enzymatic technology represents for the carbon capture industry.

“We strongly believe that the future of carbon capture rests on modern, innovative, low environmental footprint, and low-cost technologies. It’s time to face today’s carbon challenge with 21st-century technology.”

Mark McCallum, CEO of COAL21, said the enzymatic technology developed by CO2 Solutions is an “exciting process that holds the promise of lower-cost and environmentally friendly carbon capture”.

He added: “It has demonstrated that it is possible to reduce parasitic energy loads and the overall environmental footprint. It is through the broad application of technologies such as these that we can mitigate carbon emissions from any source, including coal.”