THE SIGNIFICANCE OF CHEMICAL MARKERS IN THE BIOPROCESSING OF FOSSIL-FUELS

Biochemical conversion of crude oils is a multi-step process proceedin g through a series of biochemical reactions. These reactions can be ch aracterized by a set of chemical markers which are associated with the chemical composition of crude oils. Reactions with heavy crude oils i ndicate that there is an overall decrease in the concentration and che mical speciation of organic sulfur compounds, and a redistribution of hydrocarbons and organometallic species. The contents of trace metals in the crude oils, such as nickel and vanadium, also decrease. Further , heavy ends of crudes, containing the asphaltenes and the polar nitro gen, sulfur, and oxygen containing fractions, as well as the organomet allic compounds and complexes, are biochemically converted to lower mo lecular weight chemical species. In the studies reported in this paper , microorganisms used to mediate such reactions were thermophilic ( > 60 degrees C) and pressure tolerant (up to 2500 psi). These organisms are also capable of biochemical conversion of bituminous and lignite c oals in an analogous manner to their action on crude oils and follow s imilar trends characterized by chemical markers. For example, X-ray ab sorption near-edge structural (XANES) analyses of biotreated crude oil s and low grade coals show that biochemical reactions lead to decrease s in organic sulfides and thiophenes with a concurrent increase in sul foxide contents. Chemically related constituents present in heavy crud e oil fractions and low grade coals are the asphaltenes. Asphaltenes a re complex structures containing heteroatoms and metals involved in in ter- and intra-molecular bridges and stereochemical configurations. Th e chemical markers associated with the biochemical conversion of oils and coals indicate multiple biochemical processes involving chemical r eactions at sites containing heteroatoms and metals leading to a break down of the structure(s) to smaller molecular weight units. Thus, usin g chemical markers as diagnostic tools, the extent and the efficiency of fossil fuel bioconversion may be predicted and monitored, allowing for better cost-efficient field trials. Recent results in this area wi ll be presented and discussed in this paper.