Why There's No New Coal When Reserves Run Out & How That Could Help Biofuels

Funghi that can decay lignin evolved, putting an end to the formation of coal depositsviknanda/CC BY 2.0

Although peak coal gets less attention than peak oil, the issue is gaining attention. The world consumes 6 billion tons of coal per year (2010 data),with coal consumption trending upward. The largest user of coal, China, faces the imminent depletion of national coal reserves at current use rates, raising disturbing political, social, and environmental issues about neighboring Mongolian coal reserves.

No one hopes that new reserves being cooked up deep within the earth could offer new sources of what is essentially a dirty fuel. On the contrary, many hope that we leave remaining coal deposits under the earth and turn to renewable energy sources instead.

The value of this science on coal deposit formation lies not in finding new coal, but in its contribution to our wider understanding of how genomics applies to bioenergy and environmental issues.

You Can't Interrupt What Never Started

The World Coal Association reflects the current explanation for coal deposits:
The energy we get from coal today comes from the energy that plants absorbed from the sun millions of years ago... When plants die, this energy is usually released as the plants decay. Under conditions favourable to coal formation, the decaying process is interrupted, preventing the release of the stored solar energy. (emphasis added)

Let's ignore the attempt to "spin" coal as a source of solar energy. Focus instead on the WCA's description that something interrupted the decay of plants to leave remains of lignin piling up as a precursor to the formation of coal. This represents the textbook explanation for the existence of coal reserves. But that explanation fails to clarify why the rate of coal deposition declined suddenly at the end of the Permo-Carboniferous period.

Rewriting the Textbooks on Coal

Clark University biologist David Hibbett and his colleagues hope that their studies of fungal genomes will rewrite the geology and biology textbooks. Using techniques that can predict the evolutionary tree by using genetic mutations as a sort of molecular clock, Hibbett's team calculates that the species of fungus that can decay lignin evolved after the period in which lignin piled up. So coal reserves do not result from abiotic conditions that deterred decay, but from the absence of any organisms capable of breaking down the complex lignin.

Genomics Help Solve the Bioenergy Dilemma

Explaining why there will be no new coal deposits when current supplies run out may not appear to solve any of humanity's energy problems. But understanding the evolution of species capable of naturally taking advantage of the wealth of solar energy captured by plants on planet earth could help us to better benefit from that solar energy ourselves.

In particular, the current state-of-the-art in biofuels pits nutritional demands against energy needs -- food vs fuel -- for exactly the same reason that coal deposits originally developed: we do not have good ways of using the complex parts of the plants either for energy in our bodies, or for energy for our machines. The more we learn about the species that can use these complex forms of solar energy, the better the probability that we can also tap into deposits of solar energy without starving ourselves.

Tags: Coal | Energy | Peak Oil | Solar Energy | Solar Power


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