The chemical reactions and pathways resulting in the breakdown of fluorene, a tricyclic polycyclic aromatic hydrocarbon containing a five-membered ring. It is a major component of fossil fuels and their derivatives and is also a by-product of coal-conversion and energy-related industries. It is commonly found in vehicle exhaust emissions, crude oils, motor oils, coal and oil combustion products, waste incineration, and industrial effluents. [ http://www.ncbi.nlm.nih.gov/pubmed/15317800 ]