Most fuel desulfurization methods currently used are chemical and/or physical processes. Many of these processes, such as hydrodesulfurization, typically require hydrogen and high temperatures and pressures, and hydrogenation catalysts are often poisoned by the hydrogen sulfide formed in the reaction.

The patents available for license cover novel methods of biological desulfurization of bitumens to remove difficult to process sulfur compounds using low-temperature biological reactors similar to waste-water treatment plants. Thus high-sulfur non-conventional feedstocks could be converted to lower sulfur products prior to shipment to a refinery or as part of a refinery pretreatment step.

One of the EMULSOx patents covers a microorganism recovered from a petroleum waste settling pond that demonstrated up to 47% sulfur removal from distillate versus control samples. The organism shows good specificity for sulfur removal versus others tested for comparison.

Another of the patents covers a means for using bitumens in an emulsion form as fuel in a furnace to generate steam. This steam can then be used to extract bitumens from tar sands or to generate electricity. This patent covers a method for controlling emissions and boiler fouling when burning bitumen based fuels in boilers or combustors.

Biocatalytic Desulfurization (BDS) was suggested as early as the 1950s, and has been more recently explored beginning in the early 1990s. Earlier efforts on BDS were generally focused on high-value feedstocks like distillates.

Although the application of BDS to heavy feedstocks will, according to Energy & Environmental Partners president James Valentine, require additional work on biocatalyst and process design (hence, cost), the current market prices provide the financial upside.

Resources:

• U.S. Patent No. 6,124,130: Microbial catalyst for desulfurization of fossil fuels

• U.S. Patent No. 5,593,889: Biodesulfurization of bitumen fuels

• U.S. Patent No. 5,122,353: Reduction of sulfur emissions from coal-fired boilers

• Riding the fossil fuel biodesulfurization wave; Daniel J. Monticello; CHEMTECH July 1998, 28(7), 38-45.