Le méthane et le destin de la Terre, les hydrates de méthane: rêve ou cachemar? (Methane and Earth's Destiny, Methane Hydrates: Dream or Nightmare?)

Citation

Richardson, J. (2007), "Le méthane et le destin de la Terre, les hydrates de méthane: rêve ou cachemar? (Methane and Earth's Destiny, Methane Hydrates: Dream or Nightmare?)", Foresight, Vol. 9 No. 1, pp. 73-74. https://doi.org/10.1108/14636680710727570

This handy volume by Gérard Lambert and his colleagues should be digested by anyone – geologist, extraction engineer, mining economist, government decision maker, CEO, environmental or engineering student – contemplating exploration of the globe's methane reserves. Most of us will recall methane gas from our school chemistry: a largely benign CH₄, delivered in a small tank, that was fun to play around with at the lab bench as a combustible and minor fuel.

Little did we suspect, however, its extensive availability in Nature: more than 10 billion tonnes of the stuff tucked away in ocean sediments, around the Arctic polar cap, or enclosed by permafrost. Methane hydrates are also found offshore at the base of continental slopes. They exist in such places because they have the property of combining with water to form clathrates, lattices found in crystal interstices analogous to those of ice. And a reassuring reserve of a precious natural fuel this is, just when the world's petroleum supply may be nearing its point of exhaustion.

Reassuring, yes; the gas may just play a capital role in future scenarios depicting the way that humans are likely plan the use of global energy resources. This is what the five French authors – all of them scientists – have set out to accomplish in Le méthane. Their compact book, despite a somewhat grandiose title, is a lesson in how we might, or how we should, exploit intelligently something so readily available on the planet.

The authors' first three chapters describe the methane found in the cold regions; in a fourth chapter, the quartet emphasize the function of methane as a greenhouse filter in outer space's 3 degrees Kelvin (−270°C.). Methane will be recognized by most readers one of the greenhouse gases, helping to protect (or not) Earth's surface from excessive infra‐red radiation emitted by the Sun. (There can be too much of it under certain conditions.) In terms of diminishing effectiveness as a screen/filter, methane rates third after water vapour and carbon dioxide, but ahead of nitrous oxide and a large number of other gases of extremely small concentration. As climate evolutionist Edouard Bard portrays the substance in his preface, methane is “at once the worst and the best of gases”.

The authors remind the reader of the physical law linking temperature with radiation, W= σT⁴. Here W is the radiating power of the substance concerned expressed in watts, T the temperature in degrees Kelvin, and σ is the Stefan‐Boltzmann constant of 5.67•10⁻⁸. This connotes that, if Earth were alone in space, its own geothermal flux of some 44,000 billion watts would raise its ambient temperature by some 30°C.

1 Methane as both bane and boon

Scientists seem now to understand, thanks to drilled samplings made in Greenland and Antarctica, that the greenhouse‐gas effect on the climate over the ages has been largely the result of changed concentrations in atmospheric gases – methane among them. To understand the extent of methane‐hydrate deposits that underlie this fact, the authors tell us that one need look only at the Timan‐Pechora basin in northwestern Siberia. Bordering the Barents Sea, deposits there have a permafrost depth of 600 m and cover 322,000 km² – 40 per cent of which are rich in the gas hydrates. Drilling in Alaska's Prudhoe Bay shows that the gas reserves there exceed 10¹² cubic metres, a supply that could last for quite some decades.

But, citing the economist Kenneth Boulding, the authors remind the reader that, “Anyone believing that exponential growth can continue indefinitely is either a fool or an economist”. In 2000 the world's energy consumption was around 10•10⁹ tonnes of equivalent petroleum. This figure divides itself roughly into 30 per cent petroleum, 20 per cent coal and coal equivalents, 20 per cent natural gas, 20 per cent renewable energy (mainly water, wood) and somewhat less than 10 per cent nuclear energy. Translated into consumption time at current rates, the probable fuel‐years remaining amount to: coal and lignite 500 years, natural gas 60 years, petroleum barely 40 years.

But extracting the methane hydrates is not easy. In offshore drilling for petroleum, for example, hydrate particles have often clogged extraction pipes (especially horizontal lengths of tubing), causing destructive explosions. A second hazard is spontaneous emission from marine methane deposits whereby, as the gas mixes with the atmosphere or methane‐changing bacteria, it erupts as oxidized CO₂.

The methane hydrates are there to be used, in other words, but their extraction remains to be explored and tested further in order to achieve acceptable standards of both safety (submarine earthslides may present a particular problem) and economy. Le méthane may incite future research policy, deviating into new energy provision. My only complaint with the book is that it lacks an index.