Saturday, 6 April 2019

How to cut UK carbon dioxide emissions by nine million tonnes a year.


 The UK dumps nine million tonnes of wood in landfill sites a year according to this source. That wood eventually rots down and the carbon in the wood is converted by microbes to carbon dioxide. But that’s carbon dioxide which is produced to no effect: that is, the wood could be used to heat buildings or generate electricity. Ergo if the wood was used for the latter purposes rather than being left to rot, millions of tonnes of coal and oil currently used to generate electricity would no longer be needed.  So the net amount of carbon dioxide produced by the UK would decline by roughly nine million tonnes. 

Of course given that wood consists of hydro-carbons, a significant proportion of wood consists of hydrogen rather than carbon. But that doesn’t make much difference in that that hydrogen could be used to generate electricity rather than just letting microbes mess around with it. 

Obviously the above is a very crude calculation. It is over-optimistic in that….

1. Some of the wood dumped in landfill has a significant water content. By the time that was dried prior to burning, that would cut the above 9 million to a smaller figure.

2. Transporting the wood to electricity generating plants results in carbon dioxide emissions.

But against that, the above “don’t let wood just rot” policy could be extended to woodlands: i.e. why not make it illegal to let trees and branches above a certain diameter just lie on the ground rotting away?

Of course rotting wood in woodlands does return some minerals to the soil and those minerals would be lost under the above “don’t let wood just rot” policy. But against that, the ash that results from burning wood contains some of those minerals, so that could be returned to woodlands. 

P.S. I’m not an expert on this, but wood which is buried in landfill presumably is somewhat starved of oxygen, which means it won’t produce much carbon dioxide when rotting. I.e. aerobic bacteria presumably don’t thrive under-ground. On the other hand there are anaeorobic bacteria, and they presumably produce methane when rotting the wood. Methane of course is an even worse global warming gas then carbon dioxide.

But to repeat, I’m not an expert on this. The above article is just a kite flying exercise. 

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