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Comment by belorn | Hacker News Reader

People claim that burning biomass is a net-zero effect on the climate because whatever get burned had once collected the carbon from the air. Then we have people arguing that cows are one of the main contributor to global warming because we feed them grass. In cases with produce that get rejected for once reason or an other, it may either go into animal feed or biomass depending on who is paying the more, and thus the greenness of it changes drastically.

So why are counting the methane from cows in isolation, while biomass is the sum of carbon released minus carbon extracted?

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Methane is a lot more powerful of a greenhouse gas than CO2. Turning CO2 from the atmosphere back into CO2 is net even. Turning CO2 into methane is net-bad.

Since methane is a much more potent greenhouse gas and has a much shorter half-life in the atmosphere compared to CO2, I wonder if it might actually save us. We could render the planet inhospitable early enough to be forced to address the problem without shackling future generations with the fallout like we are doing with CO2.

That's ... not great ... but only viable if methane itself doesn't move the climate past a tipping point to runaway greenhouse effects.

See "clathrate gun hypothesis", for example.

https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis

Do you know what the half life of methane in the atmosphere is? I did a search for it but couldn't find it.

9.1 years according to https://en.wikipedia.org/wiki/Atmospheric_methane

That's funny.

https://www.foodsource.org.uk/building-blocks/agricultural-m... claims

> it is a relatively short-lived GHG, with emissions breaking down after an average of around 10 years.

Looks like someone didn't understand what half-life means, or is being misleading.

On average, a molecule of methane breaks down in less than 10 years. That is a true interpretation.

Half life implies that one half of the mehane molecules decay in that period (or that a single one has a 50% of decaying).

Depends on what 'average' you mean I guess. It is true for the median of course. However, if the time for an individual molecule to decay is exponentially distributed, you can solve for lambda to find its expected lifetime is 13.1 years. That being said, I'd say this is a less useful interpretation.

When methane is oxidized it produces carbon dioxide

Doesn't it essentially decay to CO2 eventually anyway? In the long term barring it is equivalent to CO2 per carbon molecule. Granted there are Nth order effects of short term heating.

That CO2 probably came from a cow eating grass so in theory it's not a long term problem either. In practice we are destroying ecosystems faster than they can recover.

How much methane do you get out of 1kg biomass vs how much co2 if you burned it? Methane is indeed a more potent (if shorter lived) greenhouse gas, but one would guess that some amount end up either in the cow or as manure which then act as a natural fertilizer. Natural fertilizer is also an object which commonly get classified as having zero carbon footprint, which again, is a bit odd. The manure has zero carbon if used as natural fertilizer, but the meat from the same cow does not.

Methane produces CO₂ when it "decays" (not really decay, but still), so I think "shorter lived" is misleading.

Not true. The main thing that happens is that methane reacts with hydroxyl radicals in the atmosphere to produce water, formaldehyde, and ozone:

https://en.wikipedia.org/wiki/Atmospheric_methane#Removal_pr...

> [I]t would be wrong to assume that the FAO figure is totally scientific. Not only does it rely on evidence which is acknowledged to be uncertain. It is also based on a unit, known as the "CO2 equivalent", which assumes that the emission of one tonne of methane is equivalent to the emission from 25 tonnes of CO2 > [S]ince methane degrades quickly, stable emissions of methane lead to a stable level of methane in the atmosphere and no increase in global temperature. > There is something deeply untrustworthy about a metric which views methane as being many times more harmful than CO2, when only a small reduction in methane emissions is required to stabilise its presence in the atmosphere, whereas a massive reduction in CO2 emissions is required to achieve the same.

Source : https://www.thelandmagazine.org.uk/sites/default/files/Is%20...

We should obviously be worried about other green house gasses, but methane is a particularly bad green house gas in the short term.

>......The IPCC reports that, over a 20-year time frame, methane has a global warming potential of 86 compared to CO2, up from its previous estimate of 72. Given that we are approaching real, irreversible tipping points in the climate system, climate studies should, at the very least, include analyses that use this 20-year time horizon.

https://thinkprogress.org/more-bad-news-for-fracking-ipcc-wa...

This source is trash. The 25 factor comes from the relative impact over the next 100 years for emitting both.

It already factors in (relatively) fast breakdown, which the quoted text then attempts to double count.

Stabilization isn't some intrinsic goal.

I'm sure you can find a coal industry trade publication waving its hands just as well to shift the blame to agriculture.

The source may not be 100% honest, but the point still stands: a small decrease in methane would suffice.

> Stabilization isn't some intrinsic goal.

I think we both know this, now it is certainly easier if that's all what's needed (as opposed to some drastic reduction).

> I'm sure you can find a coal industry trade publication waving its hands just as well to shift the blame to agriculture.

Well yeah, for sure.

No, the point does not stand. Not at all!

The fact that there's methane breaking down in the atmosphere right now does not matter at all. It's the wrong mental model.

Each kilogram of methane you emit today is as bad as 25 kilograms of carbon dioxide over the next hundred years. That's it.

The battle for global warming is going to be won or lost over the next 100 years, easily. We'll have the energy to capture our current emissions and turn back the clock by then.

This is a good question.

Biomass consumes then produces CO2, which is net neutral. The concern with cows, whether it is valid at the levels it exists or not, is with methane, cows consume plants formed from atmospheric carbon dioxide but some nontrivial amount is emitted as methane which has many times more greenhouse effect.

> because whatever get burned had once collected the carbon from the air.

(Not an expert, just guessing here)

That is a long-term part of it. Specifically, biomass is a lot better than fossil fuels because you are not introducing any more carbon into the long-term cycle. But it is not all about the amount of 'above ground' carbon. In the short term, what matters more is 'carbon in the atmosphere'. Here, biomass is net-zero only if either the plants being burned are re-planted (i.e. wood pellets) or the biomass would have rotted away anyway (food remains).

On the other hand, cows take up a lot of acreage that could be used to capture a lot more carbon if the fields weren't filled with just grass. Besides, the actual practice of keeping cows is quite resource intensive. And, as others have said, cows produce methane.

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