Nanotech As Carbon Source?

In my previous post, I wrote that the most compact fuel for nanomachines would probably be diamond, in which case they'd dump carbon dioxide. Jamais Cascio pointed out that this could increase the earth's carbon dioxide load.

This is true. It's a special case of the general rule that an extremely powerful technology may either help or do harm, on each of a wide range of dimensions. In this case, molecular manufacturing should make it relatively efficient to pull CO2 out of the air and build the carbon into fuel. If nanomachines then burned the fuel, it would not add extra CO2 to the atmosphere. And stockpiling the fuel (which would be diamond dust - relatively inert) would reduce the atmosphere's CO2 load.

On the other hand, if coal was a more convenient source of carbon than atmospheric CO2, then nanomachines could continue the already-strong trend of burning fossil fuels and dumping the results. It would still be better than power plants, since the process would likely have efficiencies closer to fuel cells than to combusion, and all the other nasty stuff in coal (including radioactive elements) would be purified out before it was used as fuel.

Of course, to use atmospheric carbon dioxide, some other source of energy must be provided. Solar looks like a good candidate. Land-based solar cells in large quantity could cause habitat change and microclimate disruption. High-altitude solar cells (on aircraft) would be harder to engineer, but might supply a partial diffuse sun-shade (which might, with enough care, help to counteract some of the effects of global warming) and would not acutely affect the ground. (Even with today's technology, NASA has come close to building a high-altitude aircraft that could stay up overnight. Energy-gathering heavier-than-air aircraft should be quite feasible with diamondoid molecular manufacturing.)

It's also worth noting that mechanical energy storage devices (springs and flywheels) can have near-chemical energy density, and should be quite fast to recharge, and should require less machinery to extract the energy. So for some classes of nano-built robot, it may be better to include a mechanical "battery" than a fuel tank and conversion system.

Chris Phoenix

Tags: nanotechnology nanotech nano science technology ethics weblog blog

Comments

[chitra]

good

Note that just because something produces CO2, doesn't mean it adds to the CO2 load in the net. If the diamond fuel were made from fossil fuels, yes. But if it's made from plant matter, or from CO2 collected from the exhaust of existing fossil fuel power plants, there's no net increase of CO2.

[Tom Craver]

That was me - there really should be a check to ask if a poster intended to leave the name field blank...