Why was it again forests are good for the climate? Not (as many people think) because they would act as net carbon sinks (although sometimes indeed they locally and temporarily do) – but because they are semi-permanent carbon stores.

That means the world´s forests are good because they keep hundreds of gigatonnes of pure carbon locked in biomass. Despite the fact that biomass growth (and CO2 uptake) equals biomass decay (and oxidation to CO2) there is still value in the delay time in between, which permanently keeps very large amounts of carbon away from the atmosphere – so we can enjoy our present world’s moderate climate that life is accustomed to.

Some have thought however that we can make better use of this natural forest carbon cycle. If we harvested some of the biomass and burned it for energy – we’d just speed up the natural rotting processes a bit – but if done ‘sustainably’ – we may also stimulate biomass growth and of course would need to burn less fossil biomass, such as coal, the type that adds ‘fresh’ carbon to the atmospheric equation – truly disturbing a balance.

This however sounds better in theory than in practice, a recent forest biofuels study in Nature Climate Change shows. It could lead to higher than anticipated CO2 emissions – so perhaps it’s not worth additional side effects, like potential biodiversity loss.

Another October study on that same subject, published in Forests, estimates there may however still be a significant net CO2 gain of between around 70 and 110 percent if one were to compare (including the entire production chain) forest-biomass-derived ethanol with gasoline. [Fermenting willow would apparently be best…]

But if climate mitigation is what we’re after, renewable biofuel production is still perhaps not the wisest way to ‘use’ forests, that same study says.

‘Wood products displacing fossil intensive building materials’ may have larger benefits, not so much because building your home and furniture from wood (and maintaining it so it won’t rot) is indeed also favourable in CO2 terms (as the indirect forest carbon store would then actually increase – and because this would require less carbon-intensive materials as cement and concrete) – but because this transition is much more likely to be cost-effective.

That is another way of saying fossil fuels are still too cheap [thanks in part to subsidies] – and that’s one of the major obsticles preventing us from solving the climate problem.

The researchers hope that the production of such high-grade forest wood products can be combined with woody biofuel production, to maximise the climate gains – at minimised financial costs.

© Rolf Schuttenhelm | www.bitsofscience.org