It is not expected that contaminants typically present in flue gases will affect produced CO2 purity, since the enzyme-accelerated chemical capture with potassium carbonate is highly selective towards CO2. In particular presence of trace contaminants such as SOx and NOx will not affect neither the quality of the produced CO2 nor the performances of the capture unit. Almost all the SOx in flue gases will react with the potassium carbonate contained in the solvent and it is transformed in stable salts; a portion of the circulating solvent is continuously purged, in a small bleed stream, avoiding accumulation of the stable salts in the solution.

Therefore, an increasing concentration of SOx will correspond only to an increase in potassium carbonate consumption. In industrial applications, the bleed stream is filtered in order to recover and recycle the enzyme contained in the bleed stream back to the circulating solvent. NOx have similar effects, but with high NOx concentration it is expected also to have an impact on the life of the enzyme (this will be one of the objects of investigation during the pilot test campaigns). Presence of H2S could affect the performances of the enzymatic solvent if concentration is above 50 ppmv (which is a concentration well above maximum for emissions into the atmosphere therefore it is not expected to face such high concentrations). Other potential contaminants are expected to be partially absorbed in the direct contact water cooling column installed before the absorber.