People traditionally think of taxation and the environment as two separate spheres.
Government engages in taxation to generate the revenues it needs to function.
Government gets involved in the environment to protect the public interest, usually using regulation. Very simply, green taxes use the tax code to adjust the prices of products or activities. Through taxes, we can increase the cost of activities or products that damage the environment. We can decrease the cost of activities or products we want to encourage for environmental reasons. This is not an entirely new concept.