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Published online 12 December 2007 | Nature | doi:10.1038/news.2007.375
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Oil-eating bacteria make light work of heavy fuel
Unpicking the route by which microbes produce methane could help to boost the process.
Researchers have worked out how natural bacteria deep within the Earth break down crude oil and produce methane. This knowledge could help with projects to encourage these bacteria to covert more oil, faster.
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Perhaps someone could explain to me how the injection of CO2 to the oil field to produce methane is "renewable." According to my understanding, methanogenesis requires not only CO2, but a source of reducing power (such as H2). Hydrogen, for example, is produced as a product of fermentation and anaerobic respiration, which in turn require a source of energy. In short, even if we introduce the CO2 to the system, the production of methane will depend on the catabolism of the hydrocarbons, albeit indirectly. Methanogenesis will continue only so long as hydrocarbon reserves hold out.
Methane is routinely burned at oil refineries, they view it as waste. I don't understand why that isn't a more valuable source of methane than microorganisms.
On the question of injection of CO2 to oil fields to produce methane being renewable, maybe it point to CO2 coming from the burning of fossil fuel (since this is a major source of CO2 in the atmosphere); this in a way create a cycle. But all the same, it is still open to questions. The amount of methane that is being released from refineries would be a fraction of biogenic methane that is coming from various ecosystems/biological systems as well as oil fields. Also, lets remember that CO2 is currently injected into some oil fields for enhanced recovery of oil. It is obvious that the objective here is different. But does anyone know if such CO2 is being coupled to H2 to produced methane? Probably not.
Maybe this process could be used in combination with the process of under-ground in-situ gasification to harvest hydrocarbon energy in a way that would otherwise not be economically or technically feasible. It might even be done in a way that is relatively environmentally benign. In gasification, a hydrocarbon, steam, and oxygen are combined in an exothermic reaction creating CO and H2. There are a number of experiments in the world where work is being done to harvest ultra-deep, thin, or sub-marine, coal deposits by directionally drilling into the deposit and pumping in pure oxygen to yield a syngas that can be recovered at the surface for use as a chemical feedstock or fuel. Maybe the H2 could be separated out of the Syngas, the CO shifted in a catalytic reactor with steam to produce even more hydrogen and pure CO2, the pure CO2 could then be pumped back down into the coal seam. If the energy in the coal itself (or some of the waste heat from the in-situ gasification) could be used to convert the CO2 into methane. Methane would serve just as well as coal (even better) as feed for the gasification process and yield a syngas that held a higher concentration of hydrogen to CO than the syngas produced soley from coal. All CO2 produced would wind up sequestered in the void left behind as the hydrocarbon was consumed instead of being released to the atmosphere and only pure hydrogen would be harvested out of the well. A portion of the hydrogen would be used as an energy source to run the compressors and oxygen production facilities and what is left over would be your net energy in the form of pure hydrogen. Just an idea.