Biofuels Report: Forests or Fuel
1st March, 2007
The world’s forests are natural carbon ‘sinks’ that remove and store atmospheric CO2. So why, in the name of saving the earth, asks Renton Righelato, are we cutting down these precious resources to make way for fuel crops?
Most analyses of the benefits of biofuels focus chiefly on the crop/fuel cycle, ignoring the value of longterm carbon ‘sinks’ such as forests and grasslands. Yet, to be comprehensive, our approach to climate change must also look at the alternative of maintaining or restoring these areas, compared to destroying them and turning them over to arable production of fuel crops.
When arable land is restored to forest instead of using it for biofuel production, carbon stores build up in the soil and vegetation and outweigh the emissions avoided by the production of biofuel (see illustration). Converting cropland to tropical forest can sequester 20-30 tonnes CO2/hectare per year – two- to threefold higher than the emissions avoided by sugarcane-derived bioethanol. In temperate regions, forest regrowth is slower but the rates of carbon sequestration are still two- to threefold higher than the avoided emissions from biofuels produced from temperate crops. The sequestration rates fall as forests mature, but only after 50 to 100 years might the cumulative avoided emissions exceed the carbon...
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