I think that clean coal is good and a step in the right direction, but ultimately coal is not a renewable energy resource. It will be unavailable in the future and I think that we as human beings need to find better more efficient ways to gather energy. There are many different ways we can get our energy.
Bio-fuel produced from algae would be the best replacement overall in terms of global warming and least harmful effects on the environment. It is also the most feasable alternative fuel source currently known to society. It is easy to grow and we have the technology to create more farmland and rapidly grow and use this algae.