Comment by moralestapia | Hacker News Reader

Comment by moralestapia | Hacker News Reader

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Good idea and I do not diminish their creativity, findings and methods.

The reason why this and many other CO2 sequestration techniques don't work to solve the carbon pollution problem is that they always measure "gains" on a very narrow context, irl the inputs to the system incur some carbon emissions as well.

If you account for (just off the top my head):

* Grinding the limestone down to dust

* Limestone transport from whenever is sourced to the ships

* Extra weight of limestone on the ship (they say 12 TEU for a 10k container ship, small but not insignificant)

* Any difference in propulsion efficiency due to this change in the fluid dynamics that has to be compensated by ... burning more fuel (but this one could actually be negligible)

You might be emitting much more carbon than the one your system was designed to absorb.

You cannot beat the 2nd law of thermodynamics.

Smaht[1] people have been trained to quickly and loudly dismiss perpetual motion machines, but also buy the whole "revert carbon emissions" scam which is proven impossible by the exact same principles.

Btw, this is an accurate litmus test to see if someone actually understands what's going on or if its just another smaht guy parroting back what xi's been told to.

1: smaht. smart in appearance but actually dumb

Atmospheric CO2 cannot be converted back into hydrocarbons without expending more energy than the fuel originally released in combustion. Atmospheric CO2 can be converted into stable minerals that no longer drive global warming, at an energy cost less than the fuel released when it first burned.

See this chapter from the IPCC Special Report on Carbon Dioxide Capture and Storage:

https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapte...

In particular, section 7.2.2, "Chemistry of mineral carbonation." The carbonation of magnesium and calcium silicates is thermodynamically spontaneous but kinetically hindered. The kinetic hindrance is why an additional energy input is needed to draw down atmospheric CO2 in less than geological time: the mineral's accessible surface area must increase dramatically for fast silicate weathering. The thermodynamic spontaneity is why the additional energy input can be small compared to the original energy embodied in the fuels that generated the CO2.

Dirk Pässler (carbon-drawdown.de) did some back-of-the-napkin calculations for their experiments (enhanced weathering of basalt dust on cropland):

> In the end we calculated the actual emissions to be 44,6 tons CO₂, due to the fact that we drove more truck kilometers than we had planned. This is less than 10% of 1217 t basalt’s CDR potential of 509 t CO₂. In summary: The mining and transport emissions are one order of magnitude smaller than the CDR effect, even with 300-500 km transport distances. This will only get better in the future with more green energy, electric trucks and optimized logistics.

https://www.carbon-drawdown.de/blog/2022-12-14-how-cdr-with-...

>If rock powder was produced exclusively for ERW applications, a proportional share of the scope 1-3 emissions of the mining facility will be attributed by the methodology.

They purposely ignore what could be the most carbon intensive step in their process. But it's good they considered all other steps and gave an estimate of them.

This feels like the difference between science and engineering. Although to be fair to you, this paper really feels like somewhere on that spectrum and not fully on the side of science. It's similar to how every battery advancement doesn't always make it to manufacturing.

To address the things that you thought of off the top of your head: * Anything done on land will be less carbon intensive as we transition to renewables. * Trains are incredibly efficient at transport, and depending on the quarry might already be established. * Boats are so good at shipping heavy weights because of those hydrodynamics, so as long as some reduced returns are okay (reduced cargo space), there's plenty of space on those cargo ships. The real limiter is stability of steering in canals and depth of ports/canals.

>This feels like the difference between science and engineering.

I really like that analogy and will adopt it going fwd. Thanks.

Indeed, very interesting science, cool paper and much more of this research is definitely needed.

This begs a follow up study, perhaps by a different team, where they measure the feasibility of it; including, yes, the points you address.

Simple solution to all those. Have sustainably powered collection craft that slowly follow a set path, and have them release the limestone into the sea to build up artificial reefs. The reef and the resulting ecosystem can help improve fish stocks in the ocean and encourage diversity.

All that and who will pay for it? Politicians? They use taxpayers money. Companies? They will pass on the bill to the customers. So in the end same group will experience higher prices. I can't wait for all the poor becoming poorer.

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