Carbon Capture and Storage - Environmental Effects

Environmental Effects

The theoretical merit of CCS systems is the reduction of CO₂ emissions by up to 90%, depending on plant type. Generally, environmental effects from use of CCS arise during power production, CO₂ capture, transport, and storage. Issues relating to storage are discussed in those sections.

Additional energy is required for CO₂ capture, and this means that substantially more fuel has to be used to produce the same amount of power, depending on the plant type. For new super-critical pulverized coal (PC) plants using current technology, the extra energy requirements range from 24 to 40%, while for natural gas combined cycle (NGCC) plants the range is 11–22% and for coal-based gasification combined cycle (IGCC) systems it is 14–25% . Obviously, fuel use and environmental problems arising from mining and extraction of coal or gas increase accordingly. Plants equipped with flue-gas desulfurization (FGD) systems for sulfur dioxide control require proportionally greater amounts of limestone, and systems equipped with selective catalytic reduction systems for nitrogen oxides produced during combustion require proportionally greater amounts of ammonia.

IPCC has provided estimates of air emissions from various CCS plant designs (see table below). While CO₂ is drastically reduced though never completely captured, emissions of air pollutants increase significantly, generally due to the energy penalty of capture. Hence, the use of CCS entails a reduction in air quality. Type and amount of air pollutants still depends on technology. CO2 is captured with alkaline solvents catching the acidic CO2 at low temperatures in the absorber and releasing CO2 at higher temperatures in a desorber. Chilled Ammonia CCS Plants have unevitable ammonia emissions to air. "Functionalized Ammonia" emit less ammonia, but amines may form secondary amines and these will emit volatile nitrosamines by a side reaction with nitrogendioxide, which is present in any flue gas even after DeNOx. Nevertheless, there are advanced amines in testing with little to no vapor pressure to avoid these amine- and consecutive nitrosamine emissions. Nevertheless, all the capture plants amines have in common, that practically 100% of remaining sulfur dioxide from the plant is washed out of the flue gas, the same applies to dust/ash.