Energy Recovery

The same microbes that degrade oil could allow oil companies to extract difficult-to-recover energy from oil fields and oil sands through existing infrastructures, according to a new study (Nature, DOI: 10.1038/nature06484.)

Natural biodegradation in subsurface reservoirs makes oil viscous, thereby complicating and raising the cost of recovery and refining. Steven Larter of the University of Calgary, Alberta, and colleagues at universities and oil companies, found that naturally occurring anaerobic microbes dominate the degradation of oil in reservoirs. The scientists made their discovery by comparing the carbon isotope signatures of microbially degraded oil samples from reservoirs to samples degraded in lab-grown microcosms.

The biodegradation is actually a methane-generating process, Larter notes. The microbes first oxidize the alkanes in oil with water to produce acetate and hydrogen. Then the microbes break down the acetate to carbon dioxide and H₂. Finally, they combine H₂ and CO₂ to produce methane.

Oil companies know that converting the residual oil in drained reservoirs to methane would enhance final energy recovery, but putting the idea into practice has been thorny. Larter suggests that injecting phosphorus-rich fertilizer such as industrial wastewater into the fields and sands could stimulate the anaerobic microbes to produce methane, which would be less energy intensive to recover than oil.

Theoretically, the microbes could be manipulated to produce hydrogen fuel rather than methane, but that's a long shot, Larter adds.