As filters and scrubbers themselves require considerable energy to operate, their use reduces the overall energy efficiency of power plants, meaning greater emissions of carbon dioxide for a given electrical output.

Technical solutions exist in the form of filters and scrubbers installed at the plant level, but their use requires political determination because the additional costs of installing and operating the equipment must be borne by customers and utilities.

And, while technological innovations like scrubbers on smokestacks and catalytic converters on cars have reduced local air pollution substantially, the problem of CO₂ emissions remains. Indeed, it is the main reason for the world s clamor for a return to renewables.