What about ecological logs?
These logs are cleaner for the environment because of their low pollution emission rate. Since these logs are very dense they offer a better heating efficiency and they have less moisture then normal logs. A cord of green wood offers the same energy value as a cord and half of conventional wood.
On the other hand this type of wood is designed to be burned in efficient appliances such as EPA wood stoves or high-performance fireplaces. This type of wood should not be used in a regular fireplace. If you have an old wood stove or a masonry fireplace, it is recommended to use natural wood.