Please note that this blog no longer accepts comments (there was
too much spam coming in!). If you're reading this blog and want to
respond then please use the contact form on the site.
You can also follow me on twitter.
My latest Mind and Matter column from the Wall Street
What does the word "renewable" mean?
Last week the Intergovernmental Panel on Climate Change released
a thousand-page report on the future of renewable energy, which it
defined as solar, hydro, wind, tidal, wave, geothermal and biomass.
These energy sources, said the IPCC, generate about 13.8% of our
energy and, if encouraged to grow, could eventually displace most
fossil fuel use.
[Image from Climate Quotes here, hat-tip Sam Patterson]
It turns out that the great majority of this energy, 10.2% out
of the 13.8% share, comes from biomass, mainly wood (often
transformed into charcoal) and dung. Most of the rest is hydro;
less than 0.5% of the world's energy comes from wind, tide, wave,
solar and geothermal put together. Wood and dung are indeed
renewable, in the sense that they reappear as fast as you use them.
Or do they? It depends on how fast you use them.
One of the greatest threats to rain forests is the cutting of
wood for fuel by impoverished people. Haiti meets about 60% of its
energy needs with charcoal produced from forests. Even bakeries,
laundries, sugar refineries and rum distilleries run on the stuff. Full marks to renewable
Haiti, the harbinger of a sustainable future! Or maybe not: Haiti
has felled 98% of its tree cover and counting; it's an ecological
disaster compared with its fossil-fuel burning neighbor, the
Dominican Republic, whose forest cover is 41% and stable. Haitians
are now burning tree roots to make charcoal.
You can likewise question the green and clean credentials of
other renewables. The wind may never stop blowing, but the wind
industry depends on steel, concrete and rare-earth metals (for the
turbine magnets), none of which are renewable. Wind generates 0.2%
of the world's energy at present. Assuming that energy needs double
in coming decades, we would have to build 100 times as many wind
farms as we have today just to get to a paltry 10% from wind. We'd
run out of non-renewable places to put them.
You may think I'm splitting hairs. Iron ore for making steel is
unlikely to run out any time soon. True, but you can say the same
about fossil fuels. The hydrocarbons in the earth's crust amount to
more than 500,000 exajoules of energy. (This includes methane
clathrates-gas on the ocean floor in solid, ice-like form-which may
or may not be accessible as fuel someday.) The whole planet uses
about 500 exajoules a year, so there may be a millennium's worth of
hydrocarbons left at current rates.
Contrast that with blue whales, cod and passenger pigeons, all
of which plainly renew themselves by breeding. But exploiting them
caused their populations to collapse or disappear in just a few
short decades. It's a startling fact that such "renewable"
resources keep running short, while no non-renewable resource has
yet run out: not oil, gold, uranium or phosphate. The stone age did
not end for lack of stone (a remark often attributed to the former
Saudi oil minister Sheikh Ahmed Zaki Yamani).
Guano, a key contributor to 19th-century farming, was renewable
fertilizer, made from seabird dung harvested off Peruvian and
Namibian islands, but it soon ran out. Modern synthetic fertilizer
is made from the air and returns to the air via denitrifying
bacteria, yet few would call it a renewable resource. Even fossil
fuels are renewable in the sense that they are still being laid
down somewhere in the world-not nearly as fast as we use them, of
course, but then that's true of Haiti's forests and Newfoundland's
cod as well.
And then there is nuclear power. Uranium is not renewable, but
plutonium is, in the sense that you can "breed" it in the right
kind of reactor. Given how much we dislike plutonium and breeder
reactors, it seems that the more renewable nuclear fuel is, the
less we like it.
All in all, once you examine it closely, the idea that
"renewable" energy is green and clean looks less like a deduction
than a superstition.