Posts Tagged ‘Biomass’

Biofuels produce twice as much carbon dioxide per kWh as natural gas

October 31, 2013

Of course, carbon dioxide is proving to be of much less importance to global warming than the alarmists would have us believe. Sharply increasing carbon dioxide concentrations have had no impact on global temperatures for the last 17 – 18 years and the supposed link between man-made carbon dioxide emissions and global temperatures is looking very shaky.

It has been another “feel-good” assumption that burning wood, peat, bioethanol and biofuels in general are “carbon neutral”. But that is just wishful thinking. “… only about half as much CO2 per kWh is released when using natural gas rather than wood”.

“Both this and the original method used models of the forest. Models are by definition simplifications. The simplifications a researcher makes will vary according to the issues at hand, the questions being asked. You realise how much earlier analyses have oversimplified things when more refined models yield completely different answers.” 

ScienceNordic reports that scientists from the Cicero Centre for Climate Research and the Norwegian University of Science and Technology used a new method for quantifying the contributions of bioenergy to global warming as compared to fossil energy such as oil and gas.

But further research now indicates that the real climate effect of wood burning is less advantageous.

“By refining their method I determined that the emission of one kg of CO2 from biomass is the equivalent of about 1.25 to 1.5 kg fossil CO2.  So it’s much higher and less climate friendly,” says Bjart Holtsmark, a researcher at Statistics Norway.

In other words, if Holtsmark’s calculations are correct, the climate impact of using slow-growing forest wood for fuel is greater than the burning of fossil fuel, given a 100-year time frame.

Holtsmark says that the original method failed to account for how logging leaves behind dead tree parts. When trees are cut, a considerable amount of tree “waste” remains in the forest to rot and oxidise – and emit CO2.

“This aspect of the carbon balance sheet for bioenergy needs to be included,” he says. “The usual practice in forestry is to take out the trunks, while leaving the branches, treetops, stumps and roots. But the trunk only comprises half the tree’s living biomass.”

He explains that even if the branches and tops are taken out with the trunks, the stumps and roots will be left behind to oxidise into CO2. …… 

…. Holtsmark also asserts that the combustion of timber releases more carbon dioxide per kWh of heat energy than oil and gas.

“For example, only about half as much CO2 per kWh is released when using natural gas rather than wood. When this is taken into account, the picture for bioenergy from slow growing forests becomes even less advantageous.”

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