Science - January 19, 2006

Commentary / Methane from trees

Trees produce methane and therefore contribute to global warming, wrote German researchers in Nature last week. The news was all over the front pages of the world press. Arch-conservatives in the US saw it as a reason to cut down forests as fast as possible. The scientific community was astounded. Methane production is nothing new, but it is released by bacteria that do not need oxygen. So how do trees make methane? Wb asked around.

Professor Linus van der Plas, plant physiologist:
‘Oh no. It’s not about methane is it? I’ve already been called by a number of journalists this week. It’s hardly surprising; if you read the story you’d think that a plant physiologist would be able to say something sensible about the matter. But this is not the case. It seems that the methane is not produced by enzymes, but as the result of a ‘normal’ chemical process. It is not released from living cells, but probably from materials in the cell walls, one of which is pectin. Pectin is made up of long molecules containing methyl- and methoxy-groups. These could be released in some way and then form methane. The scientists don’t know how this happens, but they have demonstrated that methane is released from purified pectin. And the process does not appear to be affected by high temperatures, as you would expect if an enzyme were involved. This has more to do with polymer chemistry than plant physiology. How it happens, I really don’t know. Try a chemist who knows more about polymer chemistry.’

Dr Maurice Franssen, organic chemist:
‘Methane from pectin? Sounds like nonsense to me. Highly unlikely in any case. But to be sure, call Jean Paul Vincken, the pectin expert in Wageningen.’

Dr Jean Paul Vincken, pectin expert:
‘I read about it in the papers. I’d be very surprised. Trees don’t really contain much pectin. And I don’t understand how you’re supposed to get methane out of it. Perhaps you should call my colleague Henk Schols. He does more with pectin than I do.’

Dr Henk Schols, the true pectin expert:
‘That’s right, if it’s about pectin you need me. That methane is released by pectin? As chemist I can’t imagine it at all. We do know that methanol is released as pectin breaks down. That happens when fruit ripens, but that doesn’t mean you get methane. No, I really don’t know how that could happen.’

Korné Versluis

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