X-Message-Number: 22718
From: "Mark Plus" <>
Subject: Economist mag on the photosynthetic value of fossil fuels
Date: Thu, 23 Oct 2003 17:43:45 -0700

This goes to show how way out of equilibrium we've gotten with our 
dependence on fossil fuels.  [Mark Plus]


Fossil fuels

Buried losses

Oct 23rd 2003
From The Economist print edition

The journey from plant to coal wastes a lot of energy

ROMANTICS in the coal-mining industry (or, at least, their public-relations 
flacks) sometimes refer to the black rock that powered the industrial 
revolution as  buried sunshine . As far as the energy in it is concerned, 
that is precisely true. It is all the result of photosynthesis. But, perhaps 
surprisingly, just how much photosynthesis it results from has never been 
the subject of enquiry.

That has now changed. Jeffrey Dukes, of the University of Massachusetts, in 
Boston, has attempted to do the sums and work out how much photosynthetic 
effort lies behind the useful energy that people are able to extract from 
coal, oil and natural gas fossil fuels that ultimately derive from the 
bodies of long-deceased organisms.

That derivation involves many physical and chemical steps. In the case of 
coal, plants first convert carbon dioxide in the atmosphere into 
biochemicals, by photosynthesis. After they die, given the right conditions 
of heat, pressure and time, these plants undergo a progressive 
transformation, first into peat, then lignite and finally into coal. The 
marine plankton that end up as oil and natural gas undergo similar 
transformations. Each link in these chains involves energy losses.

Further losses are incurred when people get involved. Each stage of the 
extraction, processing and consumption of a fossil fuel squanders some 
energy along the way. Fortunately for Dr Dukes, he did not actually have to 
do the experiments necessary to estimate all these losses. Earlier workers 
had done that for him. What he did have to do was spend a lot of time in 
libraries, both real and virtual, collecting and collating that information.

The result, to be published in November's edition of Climatic Change, makes 
sobering reading. Dr Dukes picked 1997 as his datum year, since all the 
statistics for it are in. His calculations suggest that less than 10% of the 
carbon content of plants is converted to coal, while the formation of oil 
and gas from plankton is less than 0.01% efficient. As a consequence, he 
calculates that the fossil fuels burned in 1997 were ultimately derived from 
400 years' worth of  primary production , as the organic material produced 
by photosynthesis is known technically.

The reason why this is sobering is not that it says much about the size of 
fossil-fuel reserves. Rather, it raises the question of whether existing 
energy consumption could be sustained in a future when a larger proportion 
of energy was derived directly from unfossilised plant matter, or  biomass  
as it is sometimes referred to in this context. Biomass is a potential 
source of both hydrogen for fuel cells and ethanol for motor fuel, but it 
would have to be converted, in a process which would, in some ways, resemble 
fossilisation. So Dr Dukes decided to try applying his methodology to this 
question, too. Of course, the conversion processes involved would be far 
more efficient than fossilisation, but Dr Dukes nevertheless calculates that 
completely replacing 1997's fossil-fuel consumption with fuels derived from 
biomass would use up almost a quarter of the Earth's primary production. 
Such an estimate is, naturally, just a first stab at the truth. But it is 
sufficiently disconcerting to warrant further investigation.

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