Which process significantly reduces sulphur dioxide emissions?

The combination of limestone with flue gas is a well-established method known as flue gas desulfurization (FGD). This process involves injecting limestone (calcium carbonate) into flue gas generated by power plants burning fossil fuels, such as coal. When limestone reacts with the sulfur dioxide present in the flue gas, it forms calcium sulfate, which is a non-toxic material that can be safely disposed of or even used in various industrial applications.

This method is highly effective in significantly reducing sulfur dioxide emissions, which are a major contributor to air pollution and acid rain. Implementing this process helps in complying with environmental regulations aimed at limiting these emissions and improving air quality.

In contrast, combustion of coal inherently produces sulfur dioxide as a byproduct, non-catalytic dehydrogenation doesn't primarily deal with sulfur compounds, and although biofuels can have lower sulfur content than traditional fossil fuels, they do not necessarily eliminate sulfur dioxide emissions entirely. Thus, the combination of limestone with flue gas stands out as the most effective method among the given options for reducing sulfur dioxide emissions.