Rahul Basu

Biological production of methane from bituminous coal

Abstract Biogasification of coal offers significant economic and environmental benefits for the continued utilization of coal resources. Several consortia from various natural sources associated with coal have been shown to produce methane from media containing only coal as the organic carbon source. Methane production of these samples has continued to increase with time. The cultures have remained viable and have continued to produce methane after 5 successive transfers to media containing coal as the sole carbon source. Methane quantities of 4 and 5 volume percent methane (0.03 and 0.04 mmol per tube) have been observed from Pittsburgh and Wyodak coals. Serum tube experiments were scaled to larger column experiments that also indicated that methane is produced from medium containing coal as the only carbon source.

Microbial Conversion of High-Rank Coals to Methane

It has been demonstrated recently that certain bacteria and fungi are capable of directly or indirectly converting low-rank coals into liquid and gaseous fuels. The Bureau of Mines has found preliminary evidence that indicates that microbial consortia are responsible for generating methane from bituminous coal. Building on this work, a study was undertaken to test selected anaerobic microbial consortia for their ability to degrade and produce methane from bituminous coals. Five consortia were collected from natural sources, including coal strip ponds, mine treatment areas, chemical waste deposits, and sewage sludge. Three coals were incubated into various media containing inocula from the consortia. At least three of the consortia showed an ability to produce methane from hard coals in the absence of yeast extract.

Removal of carbonyl sulfide and hydrogen sulfide from synthesis gas byChlorobium thiosulfatophilum

The anaerobic, photosynthetic bacteriumChlorobium thiosulfatophilum utilizes CO2 as its carbon source and operates at the mesophilic temperature of 30‡C. It requires incandescent light for growth and compounds such as H2S, S‡, S2O32−, or H2 as a source of electrons. Of these compounds, H2S as sulfide is the preferred electron donor, with other compounds utilized only when sulfide has been depleted from the medium. The organism is also capable of indirectly utilizing carbonyl sulfide (COS), since COS reacts with water to form CO2 and H2S. This work presents kinetic information on the rate of growth ofC. thiosulfatophilum, as well as the rates of uptake of both H2S and COS. The growth is dependent on light intensity according to a Monod type relationship.

Conversion of hydrogen sulfide to elemental sulfur byChlorobium thiosulfatophilum in a CSTR with a sulfur-settling separator

Chlorobium thiosulfatophilum may be used for the bioconversion of hydrogen sulfide to elemental sulfur or sulfate. Sulfur is the preferred product because of problems in the disposal of sulfate. A CSTR with a sulfur-settling separator has been used to preferentially produce and recover elemental sulfur. The simple nutritional requirements of the bacterium and differences in densities and average cell and sulfur particle sizes make a CSTR with a sulfur-settling separator attractive. A bench-scale study has been carried out to determine the optimum process conditions to maximize H2S conversion, cell growth, elemental sulfur production, and to minimize sulfate production. The liquid effluent typically contained about 425–550 mg/L elemental sulfur. The sulfate concentration was maintained at levels below 100 mg/L. It was possible to remove up to 57 Μmol min−1 L−1 of H2S from the gas stream. An experiment over a period of 392 h showed stable performance.

Effect of furfural on ethanol production by S. cerevisiae in a cross-linked immobilized cell reactor

Abstract Furfural, a browning reaction product, inhibits yeast ( Saccharomyces cerevisiae ) growth and metabolism at low concentration levels in batch culture. The performance of an immobilized cell reactor (ICR) in the presence of 0–2.0 g 1- −t of furfural was examined. Cell growth in the ICR, with and without furfural in the media, indicated that either furfural did not impair glucose utilization, or that the negative effects of furfural were negated by increasing cell density in the reactor. Ethanol yields were constant at 0.48 g ethanol per g glucose regardless of the furfural concentration in the media. Although the specific productivity in the ICR decreased with furfural concentration, the productivity based on liquid hold-up remained constant. Furfural was depleted in the ICR during the experimental operation. Thus, furfural levels of 2.0 g I −1 or less can be tolerated by the yeast for ethanol production in the ICR without negatively affecting reactor performance.