[jbstack]

"People aren't going to starve to fill their gas tank so you need to grow more corn to offset that used for biofuel. To do that can require destroying other carbon sinks (wetlands are the example given, sometimes dried and then burned) to turn them into fields"

This doesn't make any sense to me. With petrol, you are transferring carbon from a store to the atmosphere every time you use it for energy. With a wetland, you only destroy it once (thus releasing carbon from the store) the first time you use it to produce corn. Every time after that you're capturing carbon (in corn) and then releasing it again (when burning the biofuel).

Yes, it's an oversimplified analogy (there are many more subtleties such as the amount of carbon in wetland vs corn, the carbon requirements of the production and retail process of petrol vs biofuel, etc.). But even if we made the model more complex, it's still fundamentally two entirely different scenarios. One is just a continuous release from carbon stores while the other aims to restructure a carbon store so that it can release and capture in a cycle.

[griffzhowl]

I think the idea is that the wetland or forest or whatever is a carbon sink in the sense that they have a net negative effect on carbon in the atmosphere each year. Growing corn and then burning it would at best be net zero if no further atmospheric carbon were produced by the production processes, fertilizers etc., which it is. So the differences between the two scenarios is net negative versus net positive atmospheric carbon each year.

[RivieraKid]

A forest or wetland is a carbon sink only in the growth phase. In a long-term equilibrium, it's carbon-neutral, like biofuels.

[karolinepauls]

The world is more complicated than a 17th century lab experiment in combustion.

Forests sequester carbon through forest fires producing charcoal. Humans could actually cut down old trees, dry them, and convert them to charcoal later used for soil enrichment.

Wetlands capture carbon by incorporating wood from dead trees in anoxic conditions.

> When plant productivity exceeds decomposition, net soil carbon accumulation occurs. This process eventually leads to the formation of deep peat deposits, which can accumulate for thousands of years.

https://link.springer.com/article/10.1007/s44246-024-00135-y (first search result for wetland carbon sink)

[lazytitanic]

> Forests sequester carbon through forest fires producing charcoal

Forgive me if I misunderstand, but the carbon in the charcoal resulting from forest fires isn't sequestered any more than the same carbon in the forest when in its un-burned state. The only difference is that, once you have a forest fire, a lot of the carbon is also just released into the atmosphere as CO2 in smoke.

[lithocarpus]

His point is charcoal doesn't decompose. It's very long term sequestered once it gets into the soil.

[RivieraKid]

Dead trees and other plants in a mature forest are decomposed and in that process, carbon is released back into the atmosphere.

[lithocarpus]

His point is charcoal doesn't decompose which is why we find soil with 5000 year old charcoal in it. It's basically permanently sequestered.

[RivieraKid]

Is it something that commonly happens in forests? I think mature forests today are approximately carbon neutral.

[lazide]

Bwahaha, this is so ridiculous.

Show me the megatons/year of charcoal being produced by the worlds forests eh?

We could process them yes, but we can also just make them into timber - or burn them for energy. Or just bury them somewhere under a bunch of clay. Oh, and now we’re back to this thread.

[karolinepauls]

It's as ridiculous as the comparison of the most recent 12k years of the holocene to the age of plant life on the Earth.

As for using lumber for timber, when eventually disposed it would have to be turned into charcoal rather than burned for energy or let decompose in conditions that don't sequester carbon.

You also missed the point about using charcoal for soil enrichment.

[lazide]

There is zero chance this makes a difference at the scales required. That is my point. Or are you proposing somehow making billions of tons of lumber into charcoal a year, and stopping it from further decay?

There isn’t enough room. Let alone equipment.

and it sure isn’t what happens naturally.

[griffzhowl]

Most of the land in question isn't a mature ecosystem in equilibrium, and if it is there are other arguments against turning that into cornfields. But let's say the worst case is that it's carbon neutral.

The point is that biofuel production isn't carbon neutral. Maybe it could be theoretically, but in practice it takes energy inputs in the production process like in the fertilizers, processing of crop into fuel, and transport/distribution, which makes it net positive for atmospheric carbon.

[circlefavshape]

I don't think that's true - my understanding is a forest produces soil continuously, and that's a carbon sink

[pfdietz]

Soil too eventually reaches an equilibrium where carbon injection and carbon oxidation are in balance.

If what you thought was true, imagine a forest sitting there for millions of years. Where would this permanently sequestered carbon be going? Soils do not become unboundedly thick.

[circlefavshape]

hmmm ... but forests don't actually sit there for millions of years, right? and either way soils get eroded and ultimately end up on the ocean floor

https://ijw.org/wild-carbon-storage-in-old-forests/

[Geee]

Well, that's what oil and coal are. Oil is formed from marine biomass, and coal is formed from plants.

[pfdietz]

The rate at which these are formed over time is very very small. Almost all carbon fixed by photosynthesis is oxidized over a much shorter time scale.

[anticensor]

Coal no longer forms, oil is still forming but far slower than the rate consumed.

[RivieraKid]

This was true in the carboniferous period, when the organisms able to metabolize the lignin in trees haven't evolved yet, so the dead trees ended up as coal.

[jkhdigital]

Except that industrial-scale agriculture in general requires quite a bit of exogenous petrochemical inputs—not just the fuel to power the machines that do the work, but also the fertilizer.

[pfdietz]

The energy for fertilizer is mostly in the nitrogen fertilizer. The energy input here is to make hydrogen for the Haber-Bosch process. This hydrogen can come from renewable sources ("green hydrogen"), and this would be an excellent way to counter long term variability in renewable output.

That the hydrogen currently comes from natural gas is no argument it must come from natural gas, any more than cars currently using petroleum derived fuels would imply they must use petroleum derived fuels.

[bluGill]

Still far less carbon than used for gasoline