Carbon capture buoy scenario
Contents
Context
CO2 is a big challenge of our time.
Beside avoiding to expel more of it we also will eventually need to actively take it out eventually.
This will need to be done on an unprecedented hyper enormous scale.
As you basically need to roll back the entire industrial age for the whole world.
Scenario / story
So here's a possible scenario:
In many harbors/shipyards there will be placed nanofactories producing special very robust carbon capture bouys in high quantity.
The size of the buoys may be between 10cm and 1m perhaps.
These buoys get released and spread across the oceans in low latitudes near the equator where there's the most sun to be harvested.
The buoys deploy robust swimming foils of solar cells (leaving some light and air through for sea-life).
They use the solar energy to capture CO2 and convert it into some suitable form.
Possible are e.g. ethanol (being rather environmentally non-problematic) or ethyne (being a good stoock for mechanosynthesis of diamond).
Large scale spills are unlikely if anything they will be caused by a software error or malicious attack.
Fluids might get microcapsuled.
Once they filled their tanks they return to some harbor/shipyard and feed the harvest into the global microcomponent redistribution networks
Some fraction of the harvested carbon will be used right then and there to make more buoys for sending out.
The cycle begins anew.
Dumping excess carbon
Excess carbon will need to be dumped decentralizedly.
We burnt more carbon for transport (cars, freighter ships, planes, …) than what we can ever use for housing and streets (biggest volume sinks of civilizations martial usage).
At least today without mega-structure hive-cizies.
(Which may never come considering dropping birth rates in high wealth countries like Japan. Who knows.)
Dumping all on one ginormous pile would get us a mount Everest of carbon
so heavy that it'd cause earthquakes and maybe even deform Earths crust a good bit. Man made volcanoes. Yay!
Not seriously of course. No one would consider making one ginormous pile obviously. Well, I sure hope so.
But it's still interesting to think about is this way to get an intuitive feeling for the scale of the problem.
Bad idea: People might be inclined to code the buoys such that they dump excess carbon right form the capture site to the ocean floor.
Good idea: Combine excess carbon with silicon (of which we have an FAPP infinite amount available)
to make silicon carbide (SiC, moissanite). This is highly fire resistant very unlike many other forms of reduced carbon.
Energy conversion details
After photoelectrical energy conversion (light to electrical current) rather than a following electrochemical like in batteries a two step process
electromechanical and then chemomechanical may be preferable.
Unclear if more efficient optomechanical or optochemical energy conversions pathways options will offer themselves.
Repositioning and recovery
If a buoy drifts too far it undeploys the solar cell foil and reposition itself via some robust integrated probulsion.
Buoys that get entangled somewhere or experience some other failure will report that to be recovered.
Dangers
Overall probably a low risk geoengineering approach.
A viable system would be gargantuan in size but still need years to
change the CO2 levels significantly.
So there's no risk of a malicious software attack making
CO2 levels change to dangerously low levels withing the timespan to deal with the attack.
Local on site buoy self-replication
Of course local on site repliation would be possible if each buoy would carry a nanofactory. But that nanofactory would spend most of it's lifetime inactive and pose an obvious replication accident risk. Well cathing >10cm buoys is still more managable than (unlikely) grey goo nanobots.
