Clean Coal
Clean coal is an attempt to make coal a cleaner process, as the name implies. To have a complete clean coal process, the only thing that can be done is to capture pollutants after they have been released. One way of doing this in an electrostatic precipitator. This device uses and electric current to attract fine particles, like smoke and particulates. This unit does take some energy to run and only removes those things, not the dangerous gases or lead.
Another commonly used method is wet scrubbers. Wet scrubbers can remove everything electro static precipitators can and more. These machines can remove volatile organic compounds, lead, and mercury. However, they are not always used because they are expensive. They also use a lot of water and energy.
Coal is sometimes gasified as well. This is done to remove pollutants and creates a multitude of products, including methane, a cleaner burning fossil fuel. All of these methods have some things in common. One is that none of them completely solve the problem and have draw backs that were not originally there. Another is that the only attempt to clean up the "Use" part of coals life. The extraction process is just as dirty as before and once all the pollutants have been pulled out, they still have to be disposed of. The final problem with these solutions is that they are expensive. This means companies do not adopt them often unless forced to by government. This pushes the cost of coal onto the consumer. However, if we look away from coal we start to see solutions.