The evolution of the ability to break down a plant's protective lignin largely stopped the geologic burial of carbon that formed present-day coal deposits—and may provide secrets to making biofuels from inedible parts of plants.
http://www.scientificamerican.com/article/mushroom-evolution-breaks-down-lignin-slows-coal-formation/
http://www.scientificamerican.com/article/mushroom-evolution-breaks-down-lignin-slows-coal-formation/