The principal objective of this research project as to investigate the potential for anaerobic bioconversion of low-rank coal. The research was divided into three phases, including: (a) assessment of biodegradation and coal chemistry, (b) anaerobic bioconversion of ''model''low-rank coal constituents; and (c) anaerobic bioconversion of coal. A literature review of coal chemistry and microbially-mediated processes related to coal bioconversion was performed. Initial lab studies were conducted with selected ''model''compounds, including simple aromatic constituents (phenol, cresol, catechol) as well as more complex aromatic compounds (naphthol, 9-phenanthrol, dibenzothiophene) which may be components of low-rank coal. Analytical procedures were developed for efficient extraction, separation and quantization of the test ''model''compounds. Additional studies with a benzene-derived extract of a low-rank coal sample were performed. Extraction and quantization procedures were developed to assess bioconversion potential. Preliminary toxicity experiments with ''model''compounds revealed partial inhibition of growth of selected pure bacterial cultures as well as inhibition of microbial consortia at concentrations above those used in our test system. For most of the test compounds, little or no inhibition (toxicity) was noted. Overall results suggest that complex aromatic constituents which may be representative of low-rank coal structure are relatively recalcitrant to microbial attack by natural microbial populations. 88 refs., 14 figs., 23 tabs.