The amount of carbon dioxide released from coal and wood depends on the type of coal or wood consumed and the moisture contents of both. A very rough estimate is that for each unit of coal or wood consumed, 1.5 units of CO2 are released. Higher-grade coal has higher carbon content so the amount of CO2 released per unit mass would also be higher.
The major difference between the carbon released from burning coal and wood is that the carbon being released by burning coal adds carbon to the atmosphere that has been sequestered underground for millions of years. Some would argue that burning wood is carbon neutral because the carbon released by burning the wood was subject to release anyway when the tree died and decayed, plus trees consume CO2 as they grow. It should be noted that the efficiency of the combustion appliance is also very important. Low efficiency units will produce more overall pollutants and less usable heat than efficient ones.