The Deeper View: December 2012

HYDROCARBONS ARE DEAD! LONG LIVE HYDROCARBONS!

By Robert Hazen

Executive Director and Principal Investigator, Deep Carbon Observatory,Senior Staff Scientist, Geophysical Laboratory, Carnegie Institution for Science

Thirty-five years ago astrophysicist Tommy Gold, distinguished Professor at Cornell University and scientific gadfly, published a shocking, heretical little piece in the pages of the Wall Street Journal: “Rethinking the origins of oil and gas” (June 8, 1977). It was a troubled time of gasoline shortages and crippling prices at the pump—a time not unlike today. Yet Gold espoused the optimistic view that we will never run out of hydrocarbon fuels. Petroleum, he argued, is produced in prodigious quantities deep within Earth, synthesized not by biology (as geologists had long claimed) but rather by Earth’s inner heat and pressure. Hydrocarbons, the key ingredient of petroleum, incessantly rise from the distant mantle, refilling oil reservoirs from below. Such processes, operating for billions of years, have generated thousands of year’s supply of oil.

The scientific community was quick to express outrage. Some decried Gold’s end run around the convention of peer review; newspapers are not the place to spring novel ideas on the experts. Others railed against the unsubstantiated premise of Gold’s deep oil model, which flew in the face of textbook orthodoxy. And the Soviets were furious, too, claiming (justifiably, it turns out) that they had had the idea first.

Decades of new research have not supported Gold’s deep oil theory. Perhaps most damning was Gold’s own foray into deep hydrocarbons. In 1983 he convinced the Swedish State Power Board to drill exploratory wells into the Siljan Ring Complex, a 368-million-year-old meteorite impact site where the fractured granite country rock boasts carbon-filled cracks and seeps of methane—the fuel usually sold as “natural gas”. Petroleum geologists never drill in granite, but Gold painted a vivid picture of great wealth lying just out of reach. Seven years and $40 million later, the 4-mile deep hole had yielded a paltry few dozen barrels of hydrocarbons—far less than all the lubricating oils pumped down during years of drilling. Tommy Gold claimed vindication, his many scientific detractors remained unconvinced, and thousands of disappointed investors lost their money.

Gold continued to hawk his idiosyncratic brand of Earth science, most famously in his popular 1999 book The Deep Hot Biosphere. In pointed prose he explained how deep microbial ecosystems feast on abiotic petroleum and thus leave an indelible trail of biomolecules—chemicals that less open-minded scientists misinterpret as evidence for biogenic origins. Until his sudden death in June 2004, Gold never waivered from his view that what we mistakenly call “fossil fuels” are a virtually unlimited resource from Earth’s deep interior.

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It turns out that Tommy Gold may have been right (at least partially right). Astonishing discoveries of vast subsurface microbial ecosystems and natural gas deposits resonate with some of his most controversial ideas. One of nature’s more remarkable chemical compounds is methane ice—a frozen mixture of water and natural gas that, when lit with a match, burns with a bright orange flame. Though known as a curiosity for more than two centuries, the true geological distribution of these natural gas reservoirs was unknown until recently.

The extent of methane hydrate is mind-blowing, with hundreds of confirmed gigantic deposits in permafrost zones and in marine sediments on the continental shelves. Surveys are still in progress, but with twenty quadrillion (that’s a 2 followed by 16 zeros) cubic meters of methane in total estimated deposits, methane hydrates now represent more than 30,000 years of North American natural gas consumption. These hidden reservoirs hold chemical energy roughly equivalent to all other known petroleum, coal, and natural gas reserves combined. And, in spite of conventional wisdom about fossil fuels being biologically produced, at least some of that methane appears to come from deep abiotic sources.

It’s fiendishly difficult to extract methane from methane ice. Only a small fraction of known reserves—perhaps a 600-year supply—come from sandy deposits that may be somewhat simpler to exploit. For a time, perhaps for decades to come, the efficient production of methane by gas shale fracking will provide the cheapest source. But new technologies will emerge, and vast reserves of methane ices will still be there, waiting.

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These natural gas discoveries, whether biological or not, have profound implications for our time. In the US for instance, some commentators decry the lack of a visionary government energy policy, a reliance on foreign oil, or perceived impediments to exploiting fully the nation’s vast coal deposits. Others take a longer view, looking at the historical record. Jesse Ausubel of the Rockefeller University, one of the visionaries in this kind of thinking, points out that economies of scale, not government edicts, have always been and will always be the great driver of energy policy. The most abundant and cheap fuel wins. Consider a sequence of historical examples: wood to bituminous coal in the early 19th century, bituminous coal to anthracite coal in the mid 19th century, anthracite coal to petroleum at the beginning of the 20th century. Now, given the plentiful supplies and relatively cheap cost of methane, Ausubel posits that a swift, irreversible switch from petroleum and coal to natural gas is inevitable—a transformation that may dominate global energy use for half a century or more.

Virtually unlimited supplies of hydrocarbons—check. Possible abiological origins of at least some of those hydrocarbons—check. So maybe Tommy Gold’s controversial newspaper piece a third of a century ago wasn’t so wacky after all. The ground beneath our feet still holds surprises, for we are still learning the story of Earth.