Horace Heffner wrote:
In 2003, the biologist Jeffrey Dukes calculated that the fossil fuels
we burn in one year were made from organic matter "containing 44 x
10^18 grams of carbon, which is more than 400 times the net primary
productivity of the planet's current biota". In plain English, this
means that every year we use four centuries' worth of plants and
animals.
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Does this data look right?
No, but maybe I am missing something or he does not mean what I think
he means. Pimentel and others have shown that within the US we use
roughly twice as much fossil fuel energy as the annual growth of all
plants on US soil. (And about five times more than all crops and
forests.) Our per capita energy consumption is the highest in the
world; around four times higher than average. On the other hand, our
population density is moderate, so other countries probably use
somewhere between 1 and 2 times their annual plant growth. I am sure
the multiple is not 400.
Perhaps Dukes means that it took 400 years of ancient forest growth
to produce the coal and oil we consume in one year. In other words, 1
part in 200 of ancient forest was preserved in the form of coal, oil
and peat. This seems excessively high. I do not recall numbers but I
have a feeling it is more like 1 part per 1000, or lower.
Anyway, there is no question that if we ran our automobiles
exclusively on biomass we would all starve to death. In practical
terms, given the efficiency of today's automobiles, we could not
supply more than 2 or 3% of automobile fuel with today's crops, even
if the most optimistic scenarios for future bioconversion pan
out. Even if we capture every joule of biomass energy, there is
nowhere near enough to make a significant contribution. Woolsey and
others have suggested that biomass would be enough if we use
lightweight plug-in hybrids. This is true, but so would other
unconventional sources of energy such as hydrogen based liquid
synthetic fuel from wind or nuclear power.
- Jed
