Coal Technolgies

Clean Coal. Why this is not possible

No such thing as clean coal

I was speaking to students at Castro Valley High School and one of the teachers remarked sarcastically there is no such thing as clean coal. Suggestions have been made that coal can be part of a clean energy future by using novel methods to produce “clean” coal. I thought it would be appropriate to discuss the premise and let you decide if clean coal is truly an option.

Coal for those of you who might be curious

Coal is plentiful, cheap, and readily converted into electricity. Coal is a rock which comes from plants which lived millions of years ago, in swamps. Over time the decaying plant matter created peat which is subsequently mined.

Coal exists in various forms. The differences arise from the age of the plant matter, how the heat and pressure have affected the decaying plant matter. Lignite is formed from plants which lived about 1 million years ago, older coal is sub-bituminous and still older deposits are bituminous coal. Anthracite is the oldest and hardest form of coal comprised mainly made of carbon.

Before the coal is burned the rock is crushed into tiny bits almost like dust. This coal is then loaded into furnaces, where it is burned to produce electricity. Converting the coal to dust makes the coal easier to burn.

The reality of Clean Coal

The most prominent coal cleaning technologies include: Pulverized coal combustion (PCC), Pressurized fluidized bed combustion (PFBC), and Integrated gasification combined cycle (IGCC).

I will spare you the gory details of meaning of the terms within these technologies. Their commonality is during these processes gasses including sulfur dioxide and particulates from the flue gas (combustion exhaust gas from the combustion produced at power plants) are cleaned but not removed. The amount of these materials is reduced but not eliminated entirely.

Thus, producing energy using clean coal is not possible.  Coal fulfills about 25 percent of primary energy requirements at the global level and coal-fired power generation accounts for about 39 percent of electricity production worldwide.  The use of coal going away any time soon is not realistic. Minimizing its significant environmental impact is a good thing overall. But be clear – the term “clean coal” is a misnomer.