Friday, January 27, 2006

Can biomass power stations mitigate climate change?

By Eike Roth

In partnership with Energie-Fakten

With the combustion of biomass, CO2 is always released into the atmosphere. The rationale of the policy maker to promote biomass is based on the observation that combustion of biomass releases exactly the amount of CO2 that was captured earlier from the atmosphere for growing the biomass. This is correct, but to conclude
therefore that the use of biomass for energy is climate neutral is incorrect,
and serves no purpose.

The proposition is incorrect

The combustion of biomass is only CO2-neutral if it takes place at the place of its origin, without any manipulation, and without the use of technical facilities. However, biomass energy is not practically usable in this way. Any effective energy use
  • uses technical facilities for combustion and, where applicable, for the conversion of the resulting heat energy into electricity or other energy carriers,
  • requires in general manipulation of biomass (harvesting, processing, transport) which use tools or technical facilities and
  • requires often also measures for improving crop yield (planting, possibly irrigation and manuring, care) which use again tools and technical facilities

To produce all these tools and technical facilities requires energy (among others) and using them consumes energy as well. These energy uses in general release CO2, and therefore the total CO2 balance is no longer in equilibrium. For example, there are several estimates that for biodiesel, these additional CO2 emissions are as large as the CO2 release from combusting diesel fuel from mineral oil. If this would apply, then biodiesel would be exactly as harmful for the climate as normal diesel, while more expensive (from an economic viewpoint, i.e including subsidies and several tax reliefs).

Furthermore, a good crop yield requires most of the time manuring leading to N2O releases. N2O is a potent greenhouse gas. Its effect on climate comes on top of the CO2 impact. Although there are still considerable knowledge gaps in this field, in a correct overall assessment, it could very well be that biodiesel – to stay with this example – is more harmful for the climate than normal diesel.

The proposition serves no purpose

The rationale of the policy to use biomass is the mitigation of climate change threat caused by anthropogenic greenhouse gas emissions. Even for the cases where biomass combustion would actually release less CO2 emissions (and other greenhouse gasses) in the atmosphere compared to fossil energy, it would still be more beneficial not to burn the biomass, but use it for carbon storage. We can then produce the necessary energy in other ways with significantly less CO2 emissions (particularly through nuclear energy). Biomass is best kept in its form to store carbon, and keep it a few centuries out of the atmosphere.

Originally published March 2004 by Energie-Fakten in German. Translation by SEAL.

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