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Comment by doctor_eval | Hacker News Reader

This doesn’t make sense to me.

First, the CO2 released from burning farmed plants does not increase the CO2 in the atmosphere. It’s a cycle.

Second, climate change will also cause food prices to increase. There is going to be an equilibrium point at which the increased cost of food due to land use changes outweighs the benefit of reduced emissions, but that point is almost certainly not zero.

In theory, farmers could replace corn with rapeseed at no cost to consumers if doing so mitigates climate change, the main problem is that the net cost of doing so needs to be averaged out over decades :(

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On your first point, that is not quite correct. While the CO2 released will eventualy come back, it takes an enormous amount of time. It may be a cycle but what matters is the CO2 concentration in the athmosphere or more precisely the radiative forcing at a given time.

If I burn a plant that contains 10 kg of carbon and then grow a plant that contains 10 kg of carbon then in terms of carbon in the atmosphere it should be a net zero effect. Plants take carbon out of the atmosphere to grow after all.

> If I burn a plant that contains 10 kg of carbon and then grow a plant that contains 10 kg of carbon then in terms of carbon in the atmosphere it should be a net zero effect.

No, because the plant you burned would have pulled more CO2 from the atmosphere if it had stayed alive, there's plenty of CO2 around already to feed other plants in the mean time. So the net effect is negative. If you can't grasp the logic, think about what happens if you burn all the plants. Some will grow back, but not all.

That’s ridiculous. We’re talking about plants specifically grown, using agricultural techniques, for biochar or food.

The entire industry is predicated on growing a predictable mass of plants per unit area. If we can’t do that then we have much bigger problems than the CO2 cycle.

> We’re talking about plants specifically grown, using agricultural techniques, for biochar or food.

And you believe this can be done in a CO2-neutral way, even if we assume the CO2 is recovered quickly and never accumulates in the atmosphere? Ridiculous, modern agriculture is far from even "low emission"...

That plant would pull in more CO2 and increase its own biomass based on it. When that plant then dies two-three-five years later then all of that carbon gets back into the atmosphere anyway.

>If you can't grasp the logic, think about what happens if you burn all the plants. Some will grow back, but not all.

The only way they don't grow back is if desertification happens or humans start using that area. Otherwise, the plant life returns on its own. Chernobyl is overrun by plants.

> When that plant then dies two-three-five years later then all of that carbon gets back into the atmosphere anyway.

No. If it fully decomposes at some point, arguably. But plants are eaten by various organisms (= C becomes part of the organism), are used for building houses, become fossilized. All of these make these "cycle" claims invalid.

> The only way they don't grow back is if desertification happens or humans start using that area.

No. Plants can also become extinct (= no seeds survive) or stop growing in some places due to more aggressive competition.

>But plants are eaten by various organisms (= C becomes part of the organism), are used for building houses, become fossilized. All of these make these "cycle" claims invalid.

That organism will soon die and decompose as well. Fossilization is rather uncommon nowadays. The only one of those where we could and do put a lot of carbon is buildings. However, even those end up rotting over time.

Most of the coal formed at a time where lignin didn't break down. We don't live in such a time. We can't repeat the same process. It doesn't really matter whether the carbon is released back into the atmosphere in 2, 5, 50, 100 years. It'll still be released and contribute. Stashing carbon into those forms is not a solution.

it takes one growing season for the rice, wheat, sugar cane, and soybean they were using.

> First, the CO2 released from burning farmed plants does not increase the CO2 in the atmosphere. It’s a cycle.

Widespread nonsense.

The CO2 emitted through burning plants does not magically turn into plants again. Plants have limited capacity to draw CO2 from the atmosphere and there's plenty of that around already, indistinguishable from "industrial" CO2. Any CO2 added through fires increases atmospheric CO2, any plant burned doesn't increase, but decreases the chances of CO2 removed from the atmosphere in the future.

>First, the CO2 released from burning farmed plants does not increase the CO2 in the atmosphere. It’s a cycle.

But you can say the same about burning coal.. That CO2 will eventually be consumed by plants and stored there as carbon.. only it will take quite some time

Except it won't, dead plants decompose and release their carbon back in to the atmosphere whether you burn it or not. Coal comes from an age where atmospheric carbon was much higher and nothing had evolved to decompose wood, digging it up and burning it means a net increase, growing something and burning it is net neutral.

Technically it will, because there are geological processes that more or less permanently remove carbon from the atmosphere, but they take geological time (tens of thousands of years).

Coal was laid down well before the current atmospheric equilibrium. The CO2 in coal and other fossil fuels has essentially been removed permanently from the atmosphere.

Until we dig it up and burn it, anyway.

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