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Comment by hn_throwaway_99 | Hacker News Reader

I think this is cool from an academic perspective, but I have a very difficult time believing the energy needed to crush rock, and distribute it over fields, makes this a net benefit.

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That depends on the energy source, and how much is available. If for example we convert to 100% wind/solar/battery, we'll end up with a large oversupply of zero-carbon electricity in the summer.

This may be a dumb question, but if we're collecting volcanic rock, could we not tap into geothermal energy from the volcano to get cheap energy?

The argument is basically that we will need extra energy to go towards carbon capture one way or the other. Energy in, carbon reduced. This may or may not be a feasible way to do that.

It seems reasonable to assume that many places where there is easily accessible volcanic rock are also places where geothermal is possible, but the connection between rocks like basalt and volcanoes can be more temporally distant that you may be thinking.

If I go to a beach in the US Pacific North West, I can pick up basalt rocks/boulders/pebbles, but they last were in contact with an active volcano millions of years ago (approx 12mya is the usual number given locally, if memory serves)

That is only true if we also convert to 100% w/s/b the w/s/b material sourcing, fabrication, distribution…

The energy use is surprisingly low and distances of 100-300 km can remain highly efficient, even with diesel trucks and avg grid power. By intentionally developing/utilizing crushing plants near clean energy and farmland, this can be made even more efficient.

See Potential and costs of carbon dioxide removal by enhanced weathering of rocks https://iopscience.iop.org/article/10.1088/1748-9326/aaa9c4

Environmental life cycle assessment of CO2 sequestration through enhanced weathering of olivine https://legacy.projectvesta.org/wp-content/uploads/2019/06/E...

Enhanced Weathering: An Effective and Cheap Tool to Sequester Co2 https://link.springer.com/article/10.1007/s10584-005-3485-y

We'll need to remove CO_2 from the atmosphere on a massive scale.

Both the low and intermediate IPCC scenarios, SSP1-2.6 and SSP- 2-4.5, rely on it. It will be essential to keep our planet recognizable by 2100.

Luckily the jittery/cyclic output of renewables is ideal for this. In the grand scheme of things it also solves the storage issue to a large degree, since massive overbuilding of (peak) capacity is necessary.

> Both the low and intermediate IPCC scenarios, SSP1-2.6 and SSP- 2-4.5, rely on it.

This is a huge issue that people do not understand, there is currently no plan for this CO2 removal and I was horrified when I realised that all our climate projections assume that a massive industry will just spring into existence

Liming is pretty common in agriculture already. If you need 10um particles it'll be a problem. If 100um is ok, then it's not a big deal (and transport dominates).

dunno! it's gonna be rich in iron and magnesium, which you need to grow plants anyway. I would think transportation cost would be the dominant factor but olivine is common everywhere

Hydro-powered rock crushers? Wikipedia gives an example of a waterwheel-powered machine that crushed tin ore in Cornwall in the 1800s.

Maybe mixing the crushed rock in with seeds when they’re already being planted?

More than likely using the water source to generate electricity that then powers whatever modern machinery you'd ever need is going to be significantly more efficient.

Windmills were used to crush grain too, but wind turbines are orders of magnitude better in terms of a solution.

Indeed, the largest active olivine quarry is in Norway, it's all hydro!

And then load it onto a sailing ship - carbon neutral!

I'm not kidding either.

There's already a large amount of this available and energy can be sourced from renewable supplies.

Also worth noting that life cycle assessments take into account the gray emissions produced while sequestering CO₂ so the removal should be the net CO₂ removal (although not sure if that's the case in this article).

It depends on the feedstock, and how far you truck it (last mile) but in general this is one of the most bang-for-the-buck CDR approaches, with yields of 5-10x CO2 removed vs CO2 required.

Maybe not at first, but over 75 years? Maybe so.

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