Sucking CO2 out of the air using bio-energy. A bad idea.

The Guardian reports today that the next IPCC report might suggest using biomass to suck CO2 out of the air, burn the trees for electricity, and then shove the CO2 under ground. Naturally these reports are full of assertions by various concerned parties, but numbers are glaringly absent.

So, here is a very straightforward calculation that can test the limits of biomass. Globally we consume fossil fuels at a rate of almost 15 terawatts, that is 15 trillion watts. Possible yields of bio-energy are relatively well understand. Without massive improvements through genetic engineering we cannot get anything above 0.5 watts per square metre. This 0.5 watts per square metre is achieved partly through subsidising bio-energy with fossil fuel based fertilizers and machines such as tractors.

100% biomass energy would require something like 15 trillion divided by 0.5 square metres. In other words 30 million square kilometres. This is roughly two times bigger than Russia. It is also six times bigger than the Amazon Rainforest. It is also around 20 times bigger than the area of the planet that is currently forest plantation.

So, converting all global forest plantation over to quick growing trees so that we can harvest them to generate electricity could offset perhaps a couple of years of growth in global carbon dioxide emissions. And this assumes that biomass is carbon neutral, a questionable assumption.

Clearly this is not much of a solution to anything.

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