Greenhouse Gases and Advanced Nanotechnology

by Eric Drexler on 2009/01/01

The greenhouse gas problem is far more intractable than most people think, and although there is a solution in sight, we will need a technological revolution to implement it. To be more specific:

  • Most people believe that cutting CO2 emissions in half would reduce CO2 levels, but this is wrong: Levels would still rise.
  • In the most optimistic conventional scenarios — even with swift, innovative, and successful efforts to remake the human world — CO2 levels climb higher and stay higher through the end of this century.
  • Nonetheless, molecular manufacturing capabilities based on advanced nanotechnology will make it possible to reduce CO2 concentrations to pre-industrial levels within a short time span.
  • This can resolve the dilemma of economic development and climate change.

I wrote a brief essay on this in response to The Edge Foundation’s 2009 Annual Question: “WHAT WILL CHANGE EVERYTHING? What game-changing scientific ideas and developments do you expect to live to see?” Last year’s question was “WHAT HAVE YOU CHANGED YOUR MIND ABOUT? WHY?”; respondents, answers, and press comments are presented here. I found it difficult to answer this one (too many possibilities!), but I did better this time.

The 2009 answers are under a press embargo until midnight, Eastern Standard Time, so I’ll keep my finger off the publish button for another hour or so…. And here’s the link:

Knowledge Spreading

Below are a few excerpts with added links and commentary:

Carbon stays in the atmosphere for a long time.

To many readers, this is nothing new, yet most who know this make a simple mistake [see below]. They think of carbon as if it were sulfur, with pollution levels that rise and fall with the rate of emission: Cap sulfur emissions, and pollution levels stabilize; cut emissions in half, cut the problem in half. But carbon is different. It stays aloft for about a century, practically forever. It accumulates. Cap the rate of emissions, and the levels keep rising; cut emissions in half, and levels will still keep rising. Even deep cuts won’t reduce the problem, but only the rate of growth of the problem.

In the bland words of the Intergovernmental Panel on Climate Change, “only in the case of essentially complete elimination of emissions can the atmospheric concentration of CO2 ultimately be stabilised at a constant [far higher!] level.” This heroic feat would require new technologies and the replacement of today’s installed infrastructure for power generation, transportation, and manufacturing. This seems impossible. In the real world, Asia is industrializing, most new power plants burn coal, and emissions are accelerating, increasing the rate of increase of the problem.

In fact, the mistaken idea that CO2 behaves like a typical pollutant seems deeply entrenched in people’s thinking (if you find it in your thinking, please make an effort to dig it out). I was disturbed to read a recent article in Science (here, if you’re a subscriber) in which John Sterman describes a study in which a group of MIT students (from my own school!) flubbed this completely. After reading a description excerpted from the IPCC‘s “Summary for Policymakers”, they still misunderstood the problem, mistakenly thinking that limiting emissions would limit CO2 levels. From the Science article, with emphasis added:

The dynamics are easily understood using a bathtub analogy in which the water level represents the stock of atmospheric CO2. Like any stock, atmospheric CO2 rises when the inflow to the tub (emissions) exceeds the outflow (net removal), is unchanging when inflow equals outflow, and falls when outflow exceeds inflow. Participants were informed that anthropogenic CO2 emissions are now roughly double net removal, so the tub is filling.

Yet, 84% drew patterns [graphs of emission control policies and their effects] that violated the principles of accumulation…. Nearly two-thirds of the participants asserted that atmospheric GHGs [greenhouse gases] can stabilize even though emissions continuously exceed removal–analogous to arguing a bathtub continuously filled faster than it drains will never overflow. Most believe that stopping the growth of emissions stops the growth of GHG concentrations. The erroneous belief that stabilizing emissions would quickly stabilize the climate supports wait-and-see policies but violates basic laws of physics.

Training in science does not prevent these errors. Three-fifths of the participants have degrees in science, technology, engineering, or mathematics (STEM); most others were trained in economics. Over 30% hold a prior graduate degree, 70% of these in STEM. These individuals are demographically similar to influential leaders in business, government, and the media, though with more STEM training than most.

The way to remove CO2 quickly is to pump it, but this is a project too large to undertake with today’s manufacturing infrastructure. However, as I note in the Edge essay,

If we were good at making things, we could make efficient devices able to collect, compress, and store carbon dioxide from the atmosphere, and we could make solar arrays large enough to generate enough power to do this on a scale that matters. A solar array area, that if aggregated, would fit in a corner of Texas, could generate 3 terawatts. In the course of 10 years, 3 terawatts would provide enough energy remove all the excess carbon the human race has added to the atmosphere since the Industrial Revolution began. So far as carbon emissions are concerned, this would fix the problem.

A few specifics:

  • Nanosystems provides a physical analysis of a class of selective, thermodynamically efficient molecular pumps. Devices like these provide one option for satisfying the first condition I mentioned.
  • Excess atmospheric CO2 is expected to be about 1 trillion tons in the time frame of interest, and the amount of energy required to collect and compress this to liquid density is about 1021 Joules.
  • This is equivalent to 3 terawatts of electric power for 10 years, comparable to the total world electric generating capacity today.
  • Solar arrays with an aggregate area equivalent to a 250-km square would provide ample power (assuming cells of mediocre photovoltaic efficiency, but placed in sunny locations).
  • Advanced molecular manufacturing capabilities will make it practical to produce the necessary hardware to solve the greenhouse gas problem by removing the excess greenhouse gases, reversing net emissions.

Regarding molecular manufacturing, as I note in the Edge essay:

The U.S. National Academies has issued a report on molecular manufacturing, and it calls for funding experimental research. A roadmap prepared by Battelle with several U.S. National Laboratories has studied paths forward, and suggests research directions. This knowledge will spread, and will change the game.

{ 7 comments… read them below or add one }

mitchell porter January 1, 2009 at 10:18 am UTC

Climate change seems to be on its way to becoming the central theme in world politics, at least for the developed world, at least for a time. Energy, sustainability, international relations, politicized science, it has everything. Judging by what the opinion leaders talk about, the global solution envisaged is a mixture of carbon capture for coal, carbon free energy sources, land use management, and a global cap-and-trade system which deals in carbon permits. It is a system that could do the job, but it requires new social and technical infrastructures, and it would be especially challenging politically and economically to aim this system at, say, the restoration of preindustrial atmospheric conditions. The European and Australian experience suggests that the system will be created in a form which initially implies moderate emissions cuts and which offers favored treatment for the emissions-intensive industries, apparently with the hope that later on, deeper cuts will look politically, economically, and technologically feasible. So climate politics is a process which could go on for decades before stabilizing.

For some time I have been of the view that the advent of advanced molecular manufacturing is an event which could mark the end of an epoch defined by climate politics, not just because it could make regulation of Earth’s atmospheric composition much easier, but because all the other issues arising from that technology would become the new cultural and political center of gravity. (I would like to observe in passing that not only could we draw down all that industrial-era CO2 with the envisaged solar-powered artificial carbon sinks, but in theory we could then maintain Earth in the climate of the Holocene Optimum for millions of years, by releasing greenhouse gases in quantities calibrated to offset the effects of the slow orbital variations responsible for the ice-age cycles.)

The question therefore arises: what role can and should advanced nanotechnology, and the prospect of advanced nanotechnology, play in the era of climate politics? Because if you proceed rapidly towards the advanced nano solutions, you are also hastening the arrival of all those other problems characteristic of the nano era. At the same time, one does not wish to see the world spend trillions of dollars unnecessarily. Then again, the degree to which the prospect of cheap artificial carbon sinks should permit a slackening of other mitigation efforts depends on the time to its reality. One might propose as a principle that adaptation spending should be calibrated to warming that is already “in the pipeline” (i.e. implied but not yet realized by existing anthropogenic perturbations), and that conventional mitigation spending should be calibrated to the magnitude of further anthropogenic warming influences expected in the time before advanced nanotechnology.

Meanwhile, where can the nano solution fit into the existing discourse on mitigation methods? It is a form of artificial carbon sink. One has natural carbon sinks, like plants, soil, and ocean; artificial sinks co-located with a source, such as proposals for carbon capture at coal-fired power stations; and then artificial carbon sinks proper. The leading proposal in the final category right now is a form of mineral geosequestration in which one seeks to accelerate natural geological carbon uptake by many orders of magnitude (by pulverizing the rock so as to increase the surface area, and by controlling ambient conditions so as to chemically and thermodynamically speed the process).

I think the significant political fact is that there is presently no place in the envisaged global system for geosequestration. There is a diplomatic discussion right now about incorporating carbon capture and storage into the “Clean Development Mechanism”. I would suggest that all proposals for artificial carbon sinks should try to hitch a ride on that discussion. Here one needs to make a distinction between artificial carbon sinks which are produced and operated cheaply, and artificial carbon sinks which are expensive to produce and operate. The first type is really the end of the story; at that point it’s just a matter of finding the real estate. But the second type by definition has a cost, and the point of getting artificial carbon sinks a seat at the diplomatic table is to ensure that their cost of operation can potentially be funded by the carbon finance system being created.

I think it would also be of interest to see whether specific nanotechnologically-inspired ideas about carbon drawdown can be combined with the existing proposals for accelerated mineral geosequestration. I would be rather wary of advocating, as climate policy, R&D aimed at the truly advanced sequestration systems described in this post, because despite the efforts made to decouple the idea of molecular manufacturing from the bogey of self-replication, I have to think that significant progress towards the former do inescapably bring us closer to the latter, and thus closer to something like Robert Freitas’s aerovores; and I don’t think that the problem of destructive nanotechnology can sensibly be dealt with as a subproblem of climate change mitigation.

Eric Boyd January 2, 2009 at 5:17 pm UTC

Have you given any thought to where you would PUT the 1 trillion tons of compressed CO2? At liquid (water) density 1 kg = 1 liter, so you’re looking at like 10^16 litres, or about 10,000 cubic kilometers. That’s one hell of a huge pressure cylinder. I think it would be better to somehow make the CO2 into a solid so that you can just make a mountain chain…

Eric Drexler January 2, 2009 at 9:57 pm UTC

Eric —

The main challenge with respect to infrastructure and thermodynamic cost is of course the first step, to collect CO2 that has dispersed in the huge volume of the atmosphere, but as you suggest, the choice of how to store it afterward is also important.

The most common proposals for carbon sequestration involve injection of liquid CO2 into geological formations. These proposals immediately raise complex questions that differ depending both on the mode of storage and the details of specific geological formations. Advanced fabrication capabilities — the starting point for this discussion — will open a wider range of possibilities, including incorporation of CO2 into closed-cell porous solids.

Quantitatively, the problem is somewhat smaller than is indicated by the numbers you quote (there’s a slipped decimal point), and the actual total volume is (merely!) 1,000 km^3; in the scenario mentioned, the rate would average 100 km^3/yr. To place this in perspective, the rate at which the Greenland ice sheet is melting into the sea increased from 90 to 220 cubic kilometers per year in the decade leading up to 2006.

John Thompson January 4, 2009 at 3:26 am UTC

I think “jay” is joking. But I didn’t get my STEM training in school. Humanities major. Nonetheless, this accumulation of CO2 has always made sense to me.

For years I wondered, why accumulation isn’t the topic. Last year or year before, it started on NPR with acidification of the oceans. (I’m sure the coral reefs made oceanographers aware of CO2 accumulation many years ago. And permafrost and glaciers melting also! )

U of Hawaii posted a study on volcanoes that basically said humans are adding CO2 at a 100 times the rate of volcanoes.

So resistance is moot. Rising methane would blow up the atmosphere and end agriculture. Maybe?

I guess coal would work dandy with where we are at (as insane as that sounds). I first thought, we need a smart grid and renewables to make this nano manufacturing project a reality. But we’ll need all the power we can get.

Saw Aubrey’s essay on The Edge Foundation. The basic gist was, we’ll have the ability to do amazing things like you suggest. At the same time, human nature itself will determine whether we do them or not.

Big fan Dr. Eric!

Eric Drexler January 5, 2009 at 5:16 am UTC

A public service announcement:
One or more comments was accidentally deleted during a purge of robo-spam, not as a result (this time) of a content-filtering policy.

Paul Baclace January 5, 2009 at 10:36 pm UTC

Wallace Broecker, the Columbia University professor who is credited with coining the term “global warming”, has a project to sequester CO2 by combining it with silicate rocks to form carbonate rocks. Physicist Klaus Lackner, and engineer Allen Wright are part of the team and they have VC funding.

See the PNAS paper “Carbon dioxide sequestration in deep-sea basalt”

Even if sequestering is implemented, the thing that worries me about climate change is that we ultimately want a planet-wide climate control loop that performs a measure/integrate/decide/act loop. However, the error bounds on the assumptions leave plenty of room for bickering, and the timescale of the integrate part of the loop is said to be 13 years (to filter out natural variability). The decide and act parts are currently measured in decades, but future cycles could be reduced to (say) 2 years.

Given the long timescale of the control loop and large error bounds on the actual dynamics, the error correction needed to reach a stable equilibrium will take many ~15 year cycle iterations.

Nanotech could help by improving measurements or by efficiently (energy and cost) sorting atmospheric molecules to get the CO2 out. Even better, nanotech could help create an energy storage and distribution system that does not use the atmosphere as a waste dump.

Amy Raine September 30, 2009 at 4:40 pm UTC

I actually have several questions:

What is your view on Nanotechnology being used for landfill clean up / garbage disposal? Would it be possible for Nanotechnology/nano systems (trying not to use the term “nanobot”) to break down garbage/nanosystems that have expired, into compounds that are safe and possibly sold on the market? This would suggest that the Nanosystem recycling unit be in a closed well contained factory for easy recovery/shipment of such materials. Do you know of any companies / college programs researching out this landfill/garbage nanotechnology recycling possibility?

I have heard of Project Kaisei where they are looking to capture deris from the Pacific Ocean and potentially creating biodiesel fuel from it. However, no clear leadership in the area of landfill/garbage recycling.

Please advise and thank you.

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