The title of the thread is misleading. Wood releases the same amount of CO2 whether it is burnt or decomposes naturally on the ground. new growth takes up this CO2 that has been released into the atmosphere. That is why burning wood as a source of heat or gassifying it as a transportation fuel or for electrical production is carbon neutral.
The problem with fossil fuels is we are releasing tremendous amounts of carbon that have been out of the cycle for millions of years and adding to our levels. This higher level of CO2 acidifies the ocean.