Why Does Abiotic Oil Contain Biological Material? Thomas Gold Resolves the “Petroleum Paradox”
In the process of up-gassing from the Earth's mantle hydrocarbon fuels pick up biological material from sedimentary rock layers
This substack article is an extract from my book The Truth About Energy, Global Warming, and Climate Change: Exposing Climate Lies in an Age of Disinformation.
In resolving what Gold called “The Petroleum Paradox,” i.e., that hydrocarbon fuels contain biological material, Gold came to realize that the deep, hot biosphere was not manifested just by deep-sea hydrothermal vents. The deep, hot biosphere extended miles into Earth. An August 1984 paper published in Scientific American by a group of scientists led by Guy Ourisson at the University of Strasbourg found that the quantity of biological debris in petroleum was astonishingly large.[1] The Strasbourg scientific team “expressed the conventional view that biology was essential for the production of hydrocarbons.” What Gold came to understand was that petroleum “could be food for a prolific microbial life and thereby create the association between petroleum and biology.”[2] In November 1984, Gold published a reply to Ourisson’s research in Scientific American. Gold’s response letter read, in part, as follows:
A widespread early bacterial flora may have arisen when hydrocarbon outgassing of the earth provided a source of chemical energy in the surface layers of the crust where oxygen was abundant owing to the photodissociation of water and the loss of the hydrogen to space. Methane-oxidating bacteria (and possibly oxidizers of hydrogen, carbon monoxide, and hydrogen sulfide) may have been able to thrive in the crustal rocks. In the course of evolution, photosynthesis, with all its complexity, may well have been preceded as a source of energy by hydrocarbon outgassing. The flora the outgassing sustained gave oil and coal its distinctive biological imprint.[3]
One of the molecular signatures of life that Ourisson’s team found in oil was hopanoids that Gold described as “slightly oxygenated and enriched versions of the hydrocarbon molecules known as hopanes, which contain anywhere from about 27 to 36 atoms of carbon arranged in contiguous rings in a single molecule.”[4][MOU1] [MOU2] Gold realized that hopanoids are prominent in oil. The Ourisson study also noted the amount of hopanoids was huge. They projected the global stock of hopanoids would be 1013 or 1014 tons, more than the estimated 1012 tons of organic carbon in all living organisms. Gold recognized that the presence of the hopanoids confirmed his theory of the deep-hot biosphere. He wrote:
Hopanoids are prominent in all of the numerous samples of petroleum that have been tested for them. This includes samples drawn from sediments of widely ranging ages and from all over the world. And there is no dispute that these molecules are derived from the membranes of once-living cells.[5]
Gold commented that “Ourisson and his colleagues were puzzled, however, by the fact that whereas living trees and ferns and algae are known to contain hopanoids at the lower end of the carbon-number spectrum only bacteria contain the higher-carbon molecules, such as C35 and C36.”[6] The Ourisson team found another interesting molecule (a terpenoid), common in hydrocarbons, “is also present in bacteria known to make their living by oxidizing methane.”[7]
All this made sense to Gold. He concluded the following:
The biogenic molecules discovered in natural hydrocarbons throughout the world can all be linked to constituents of bacteria or archaea, and none is linked exclusively to macroflora or fauna. There is thus no evidence in these observations that anything other than a substantial microbiological contamination of oils is required to explain all the molecules observed. And this means, in turn, that there is no evidence that any surface life must be invoked to explain the presence of these biological molecules in subsurface hydrocarbons.[8]
Equipped with the theory of the deep, hot biosphere as the solution to explain the petroleum paradox of why organic material is found in petroleum, Gold began estimation on how deep into Earth the biosphere extended and how much biomass the deep, hot biosphere might support. He estimated the biosphere might extend five to ten kilometers (approximately three to six miles) below the surface. He also calculated that the “biomass originating and contained within the deep hot biosphere would be equivalent to a layer of living material that would be approximately 1.5 meters thick if it were spread out over all of the land surface.”[9]
Gold noted that deep biomass of this magnitude would be “somewhat more than the existing flora and fauna of the surface biosphere and it comports with the worldwide estimate of biological debris—hopanoids—calculated by the Ourisson team to be present in all crude oils.”[10] With these realizations, Gold explained biological material was in crude oil not because organic material produced the oil and not because the petroleum gathered biological debris on its way to the surface. The biological debris was present in crude oil because bacterial microorganisms fed off the hydrocarbons.
In March 1992, Gold published his findings in the Proceedings of the National Academy of Sciences in the first publication that Gold entitled “The deep, hot biosphere.” He wrote the following about the startling and highly controversial findings:
There are strong indications that microbial life is widespread at depth in the crust of the Earth, just as life has been identified in numerous ocean vents. This life is not dependent on solar energy and photosynthesis for its primary energy supply, and it is essentially independent of the surface circumstances. Its energy supply comes from chemical sources, due to fluids that migrate upward from deeper levels in the Earth. In mass and volume it may be comparable with all surface life. Such microbial life may account for the presence of biological molecules in all carbonaceous materials in the outer crust, and the inference that these materials must have derived from biological deposits accumulated at the surface is therefore not necessarily valid.[11]
Gold’s theory of deep-Earth bacteria does more than simply offer a solution to the petroleum paradox. His approach to understanding deep-Earth bacteria also supports the proposition that deep-Earth hydrocarbons play an essential role in Earth’s food cycle, as well as Earth’s energy and climate cycles.
[1] Guy Ourisson, Pierre Albrecht, and Michael Rohmer, “The Microbial Origin of Fossil Fuels,” Scientific American, Volume 251, Number 2 (August 1984), pp. 44-51, https://www.jstor.org/stable/24969433.
[2] Thomas Gold, The Deep Hot Biosphere, p. 83.
[3] Thomas Gold, “Letters,” Scientific American, Volume 251, Number 5 (November 1984), pp. 6-10, https://www.jstor.org/stable/24969468.
[4] Thomas Gold, The Deep Hot Biosphere, p. 83.
[5] Ibid., p. 84.
[6] Ibid.
[7] Ibid.
[8] Ibid.
[9] Ibid., p. 86.
[10] Ibid.
[11] Thomas Gold, “The deep, hot biosphere,” Proceedings of the National Academy of Sciences of the United States of America, Volume 89, Number 13 (July 1, 1992), pp. 6045-6049, https://www.pnas.org/content/89/13/6045.short.
[MOU1]Closing quote mark missing. My guess is that it belongs here. If not, place it where it should be.
[MOU2]Yes – End-quote placement is right.