2011-12-19 07:57:59Intermediate rebuttal #134 "Breathing contributes to CO2 buildup"
perseus

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I've not got a response to my query on this rebuttal, on the basic rebuttal forum. Perhaps I posted it in the wrong place.

D134 "Breathing contributes to CO2 buildup" By breathing out, we are simply returning to the air the same CO2 that was there to begin with.

I think we need to correct this one with the caveat that although breathing in itself might not be considered to contribute to net CO2 due to absorption of CO2 by the plant feedstock, the whole range of processes required in the production of food does indeed emit significant GHGs to the environment.  This contribution is very large, a similar amount to world transportation.

This may at first sound pedantic. However, the rebuttal in its present form is essentially the same argument that 1st generation biofuel manufacturers used

'CO2 emitted from a vehicle is replaced by the CO2 absorbed by the feedstock, so the biofuel is carbon neutral',

but we know this is misleading.

We criticise Spencer as well.

"It is a little known fact that the extra carbon dioxide (and methane, an especially potent greenhouse gas) emitted by joggers accounts for close to 10% of the current Global Warming problem."
20 June 2005 (Source)
By breathing out, we are simply returning to the air the same CO2 that was there to begin with.

The premise of the rebuttal to Spencer is that breathing shouldn't be taken in isolation from the entire chemical cycle. However, on this basis we must include the nutrients and planting of the crops which of course include the GHG emissions released by fertilisers, tilling and possibly deforestation, such as N20 and CH4. (He is of course literally wrong but we know what he means here. I don't think he is referring to joggers farting mentioning methane!)

The bottom line is that breathing increases with exercise which requires more food, and food (particularily those involving meat production) does indeed generate significant net GHGs to the environment.

According to these calculations walking at 3mph generates almost a quarter of life cycle emissions per mile than that of driving, assuming the typical US diet. Obviously this could be drastically reduced by eating vegan foods.

It is based on this calculator

It would be logically consistent if we could agree that all biofuels were carbon neutral, but I guess we would be quickly writing a rebuttal in that case, so we can't have it both ways?   The bottom line is that food currently contributes around the same as transportation fuels in terms of GHGs and CO2 is one of those emissions.