Uncharted Territory

December 8, 2008

Biofuel Payback Periods – Update

Filed under: Biofuels, Global warming — Tim Joslin @ 5:34 pm

Even though the BBC report, “Palm oil offers no green solution”, was clearly written by a computer programmed without regard to punctuation or sentence structure, it appears that at least some researchers have started to realise that:

(1)  The critical resource when considering the wisdom – or lack of it – of promoting biofuels is the land required for growing the biofuel crop.

Land stores a lot more carbon if left uncultivated (e.g. as forest) than it does if it is cultivated (e.g. used to grow biofuel crops).  Clearing land for cultivation may therefore be said to incur a “carbon debt”.

(2)  The critical concept in evaluating the value of biofuel crops in slowing global warming (or, more likely, making the problem worse) is the payback period for the carbon debt.

The crucial question is:

“For how long would we have to grow biofuels in order to justify the decision to cultivate the land rather than allow it to revert to its natural state?”

The BBC therefore reports that:

“The lead author of the study […,] Finn Danielsen of Denmark’s Nordic Agency for Development and Ecology [said:] ‘Our analysis found that it would take 75 to 93 years to see any benefits to the climate from biofuel plantations on converted tropical forestlands’…”

My money’s on us running practically everything on cheap renewable electricity long before those 75 to 93 years are up.  Otherwise we’re toast, and all bets are off.  So we never will grow biofuel crops for those “75 to 93 years” – even if we don’t degrade the soils long before then.

But “75 to 93 years” is likely an underestimate, since conceptual problems are still evident.

Unfortunately, as evidenced by the BBC report, researchers still think just in terms of how long it would take to pay off the carbon debt from clearing the land.  As I argued in the Biofuel Papers – sigh! – this is only part of the story.  The Beeb notes that:

“On a positive note, the researchers found that grassed areas where forest had been destroyed in the past, the land farmed and then abandoned, did become a net absorber of carbon after 10 years of being planted with palm oil.”

But the land in question was already “a net absorber of carbon”, since it was slowly reverting to its natural state – presumably forest.  Duh!

In short, you need to take account of the opportunity cost of growing biofuels.

And not only that.  If you clear land to plant a biofuel crop such as oil palm trees, you also need to take account of the damage done (i.e. planetary heating) by the extra carbon in the atmosphere over the years during which there is more carbon in the atmosphere than there would have been if you hadn’t cleared the land.

Oh well, I guess we’re slowly getting there.  At least we’re starting to take account of the land required for biofuel crops.

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1 Comment »

  1. […] but naive public procurement crashing into commercial interests to that which has led to the biofuel disaster. Garnished with the hopeless optimism that accompanies new technologies, of course. During the […]

    Pingback by The Electro-Kinetic Bandwagon « Uncharted Territory — June 18, 2009 @ 7:46 pm


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