by Eric Flint
Becoming Stewards of Our World:
The Great Theme of the 21st Century,
Part One
Written by Gregory Benford
Part I: Beyond the Box
Only puny secrets need protection. Big discoveries are protected by public incredulity.
—Marshall McLuhan
The deep secret about global warming is that the conventional wisdom solution is a lie.
About 80 percent of the world's energy comes from fossil fuels (coal, oil, natural gas). They sustain economic growth, bringing political and social stability. Until we can replace fossil fuels (which will take a century, at least) or find practical ways to capture most of their emissions (a very tough job), no political system will allow the deep energy cuts that would truly affect global climate change.
Politicians are now playing the posture game. Companies are the enemy, because . . . well, they give us what we want: more. So business polishes its' image, tipping the hat toward minor adjustments. Herd behavior.
Muddling though won't work, but few will say so in public. "Cap and Trade" or carbon taxes will help, but they cannot solve the problem—demand is too great, and plausible carbon-free power will be a tiny fraction of what we need. (If all drivers in the USA swapped their car for a Prius, oil use would decline only 3%.) No economist I know thinks we can replace even our current energy sources with renewables in less than half a century. And we don't have that much time.
In 2004, world emissions of carbon dioxide (CO2, the main greenhouse gas) totaled 26 billion metric tons. CO2 emissions will grow to about 40 billion tons by 2030, most from developing countries, two-fifths from China alone. Right now China and India alone are building 850 coal-fired plants. Today's investments are going to be sunk in power plants for the next 50 to 70 years.
We are building so many new conventional coal plants that their CO2 emissions will overwhelm Kyoto emission reductions (if they even happen) by a factor of five by 2012. Likewise, we're on the wrong track with "green" nukes (which Greens oppose anyway), so long as they're burning supply-limited U-238. So, how about wind and solar electricity? Good, but intermittent. Certainly nobody's building the right electricity distribution and storage network to bring on line at the needed 30 to 50% market penetration. For land use and net energy balance reasons, ethanol is totally inadequate replacement for petroleum fuel, particularly if China and India follow US lifestyles.
These truths will not go away if we ignore or deny them anymore than global warming deniers make that truth go away. I know perception by the public is a matter of emphasis, or "spin," if you will. But political correctness is one thing. The real world is another.
And demand won't stop then, either. This problem will not "stay solved" because economies are dynamic.
Poor countries won't sacrifice economic growth just because they're lectured by the rich world. Why should they? On a per-person basis, their CO2 emissions are only about 20% of the rich countries'. In Africa, fewer than half the population even has electricity. Quietly, everywhere, fossil fuel plants are a-building faster and faster, worried about future constraints. CO2 emissions are accelerating.
The sole smart answer is to go to the tech. Save the world, right away! But existing power-generating technologies, even aggressively pushed, can't save us. Demand is too large. Research, development and deployment will take many decades.
I first realized this by serving on a Department of Energy long-range study. Our years of work appeared in a prominent paper in Science (ref). Renewable technologies exist in the sense that the science to make a nuclear weapon existed in the late 1930s, or the ability to send a crewed exploration craft to the Moon and return existed in the late '50s. But it took the Manhattan and Apollo programs to make them so. The Manhattan-scale project we called for has not materialized.
It's time to see the climate/energy challenge as a war of survival, with failure not an option. The plausible future emission levels (Fig. 1) make this clear (Fig. 2).
Projected Carbon Dioxide concentrations over time, with best-estimate temperature increases that result. We now have 380 parts per million by volume (ppmv) in our air. The realm between "a" and "b" is what we now have in temperature increase over the mid-20th Century. Source: International Panel on Climate Change
To maintain and improve our civilized lives, we will need to educate ourselves about how the life support systems that sustain us on planet Earth work, and how they could work, to run high tech civilization without savaging the remaining nonrenewable energy resources and precious biodiversity legacy of Earth.
This perspective isn't really new. Little noticed, we've entered a new geological era, the anthropocene. We started ten thousand years ago, swiftly changing the biosphere by converting forests to farms. Large diebacks of species surged as we spread into the new world several millennia ago. Several centuries back, we began altering the atmosphere with CO2. This now brings on considerable warming within mere decades, and is already turning the oceans more acidic, with big changes within a century from now. These radical, swift swerves will show up in the geological record.
So . . . what to do?
Answer: get outside the conceptual box.
Climate Restoration
There are at least two (barely examined) ways to stop the greenhouse impacts to come: draw CO2 from the air, or reflect sunlight. Neither has any traction so far. Governments have devoted only tiny sums to their study.
This first article deals with capturing carbon from the air. The second part will treat reflecting sunlight back into space.
The simplest way to remove carbon dioxide from the air is to grow plants—most popularly trees—since they tie up carbon in cellulose, meaning it will not return to the air within a tree lifetime.
A little-noticed 1992 National Academy of Sciences panel report clarified the muddy science behind global warming and then ventured further. Could we intervene to offset the warming? Accept that greenhouse gases will rise and find ways to compensate for them? Mitigate, not prohibit?
The older term for all such ideas is "Geoengineering." I find that most people don't know what that means. I prefer to call these ideas "Climate Restoration," because that's the goal. After all, to get a car fixed we don't go to businesses called "Combustion Engineering," we go to "Car Repair."
That 1992 National Academy of Sciences report was the only one that some scientists tried to block from publication. The subject calls up the common Western impulse to solve problems with laws rather than technologies. We endured the War on Alcohol (Prohibition), our War on Drugs is thirty-five years old and has never worked, so a War on Carbon may lie ahead. Such thinking is perfectly in keeping with the universal environmentalist position, which is best understood as a starkly Puritan ethic: "Abstain, sinner!" "The only way to slow climate change is to use less fuel," asserts Bill McKibben in The End of Nature, a book that roundly condemns such luxuries as privately-owned washing machines and oranges shipped to cold climates.
Here I shall discuss two areas I've worked in for over a decade, as chronicled in my 1999 book, Deep Time. Much has happened since, including some name changes.
Invoking engineering implies an existing craft, but neither carbon capture nor reflecting sunlight have been tried on even regional scales. Nobody envisions quick, full-scale climate mitigation. At first we should do laboratory work, carefully testing the basics of any proposed scheme. Then we can follow with small-scale field experiments to answer questions about how our current atmosphere behaves when we change its dynamics slightly. The biosphere is a highly nonlinear system, with climatic lurches before (glaciations, droughts), and unstable modes, too.
Some argue that this simple fact precludes our tinkering with "the only Earth we have." Of course, we already are—that's the greenhouse problem. Earth's climate might be chaotically unstable, so that a state with only slightly different beginning conditions would evolve to end up markedly different. Then the alighting of a single butterfly might
change our future. But we also know that the Earth suffers natural injections of dust and aerosols from volcanoes, so probably experiments which affect the planet within this range of natural variability should be allowed.
Still, suppose a big volcano erupts while you are floating artificial dust high in the stratosphere—might this plunge us into a new ice age, pronto? The proper answer is: Not if we keep our artificial dust well below the historical fluctuation rate; and without experiments we cannot make progress.
Global warming is assessed in a rather tightly knit community of scientists, mostly academic. They only study nature, while engineers dream of altering it. Both need experiments to guide them.
Leaving politics aside for the moment, this portends the inevitable emergence of a new techno-visionary community, devoted to solving global ills with global technologies. This is quite different from simply finding the polluters and forcing them to stop. Such good/bad dramas are an old theme in environmental issues; like depletion of the ozone layer and cleansing of the seas, global warming has provoked an automatic politicizing of any proposed solutions at birth.
With ozone and the seas we could comfortably point fingers at big companies or nations. Alas, the culprit in global warming is plain old us.
Capturing Carbon
Plants build themselves out of air and water, taking only a tiny fraction of their mass from the soil.
Forests cover about a third of the land, and have shrunk by a third in the last ten thousand years. (They have grown back some over the last half-century in the United States, mostly because marginal farms were abandoned and the trees reclaimed the land.) Like the ocean, land plants hold about three times as much carbon as the atmosphere. While oceans take many centuries to exchange this mass with the air, flora takes only a few years.
As tropical societies clear the rain forest, the temperate nations have actually been growing more trees, slightly offsetting this effect. In the U.S., we have lost about a quarter of our forest cover since Columbus, with a rebound since 1950. Replanting occurs mostly in the south, where pine trees are a big cash crop for the paper industry. But globally we destroy a forested acre every second. Just staying even with this loss demands a considerable planting program.
Trees soak up carbon fastest when young. Planting fast-growing species will give a big early effect, but what happens when they mature? Eventually they either die and rot on the ground, returning nutrients to the soil, or we burn them. If this burning replaces oil or coal burning, fine and good. Even felling all the trees still leaves some carbon stored longer as roots and lumber.
About half the U.S. CO2 emissions could be captured if we grew tree crops on economically marginal croplands and pasture. More forests would enhance biodiversity, wildlife and water quality (forests are natural filters), make for better recreation and give us more natural wood products.
Even better, one can do the cheapest part first, with land nobody uses now. This would cost about five billion dollars a year. A feel-good campaign would sell easily, with merchants able to proclaim their eco-virtue ("Buy a car, plant a grove of trees.")
In the short run, this would probably work well. But trees take water and land is limited, so this is a solution with a clear horizon of about forty years. Soaking up the world's present CO2 increase would take up an Australia-sized land area, i.e., a continent. But most such land is in private hands, so the job cannot be done by government fiat in its own territories. Still, a regional effort could make a perceptible dent in overall carbon dioxide levels.
But . . . leaves absorb more sunlight than grasslands. Some climate modelers argue that adding forests will actually increase warming in the long run, because most of the CO2 gets drawn down by young trees, which then absorb more sunlight later, warming their areas. So it's not a certain measure.
Coping With Carbon
Seen in the largest perspective, our current atmospheric buildup of CO2 stems from our first great invention, the discovery of fire. Given that, our eventual discovery of fossil fuel, and our short political time horizons made a greenhouse problem inevitable.
Can we offset our greenhouse effects by using our second great invention, agriculture? Robert Metzger (engineer and writer) and I explored this with collaborators six years ago and found that we can, with some help from the wheel.
Farming is the largest scale human activity, covering about 10% of the globe's land area and employing billions. Leveraging this large effort offers a way to help draw CO2 from the air.
The trick is to use a simple fact: growing a field of corn captures about 400 times as much carbon as humanity adds, per year, to the entire column of air above that field, from ground to space. If we could plant corn over 1/400th of the Earth's surface, every year we could draw back out what we put into the air by burning. (To see this, check the sidebar.)
Carbon Above a Cornfield The carbon-drawdown of a cornfield calculation begins with assumptions. At harvest time, an average acre of corn has a dry mass of 10 tons in the crop (grain, stalks, leaves and roots). This mass has an average carbon content of 40%, so the crop has 4.0 tons of carbon in it. The carbon got locked up in the plants by photosynthesis-driven chemistry. In the air above the cornfield, humans add CO2 every year, in the amount of 1.6 parts per million of air molecules (ppm) per year. Taken all the way to space, this means there are 10 kg of carbon in the column of air above the cornfield. (Getting this demands using the masses of CO2 and air, and multiplying by the height of the atmosphere.) Then one acre of corn incorporates as much of our annual increase in carbon stored in the air column above 400 acres.
So there is a lot of carbon hovering over our heads. It gets drawn down into vegetation like corn every year, only to be returned to the air when the bulk of the vegetation rots. The annual oscillation in CO2 in the whole atmosphere reflects this storage in the northern hemisphere, where most of the land is; in winter the CO2 returns to the air. Harnessing this prodigious storage method could give us great leverage over the global CO2 imbalance. Just keep the vegetation from rotting back into the air by hiding it.
As he does so often, Freeman Dyson had the basic idea first. In 1977 he proposed storing away trees. ("Can We Control the Carbon Dioxide in the Atmosphere?", Energy J. 2, 287–291.) Much has been done since.
Lately, two distinct approaches emerged for hiding away (sequestering) CO2 from the air:
1.Pre-emission carbon sequestering.
Take carbon out before burning fuel or letting vegetation rot. The Department of Energy studies only capturing carbon during the burning process, then packing it away under pressure. One can inject it into deep saline reservoirs, as is done by a Norwegian energy company, STATOIL. They separate CO2 from natural gas at high cost and inject about a million tons per year into the open spaces where they got the oil a kilometer below the North Sea ocean floor. Other possible sites include active and depleted oil and gas reservoirs, and mined cavities in salt domes. The danger here is that many domes leak, because millions of wildcatter drillings have punctured them.
2. Post-emission carbon sequestering.
This means sucking CO2 from the air after burning the fuel. This is intrinsically better, because it can reduce present levels, the only way to do so besides growing more trees (which is a good, though limited idea). This makes nature a partner in doing the work.
There's a little-noticed secret here, too. We put about 7.4 GtC (giga-tons of Carbon, C—where giga- means a billion) into the air. But only around 3.5 GtC gets permanently into our atmosphere. So nearly half goes somewhere else—most likely, the oceans and the land, though we know this only poorly.
Still, this missing half means that nature hides a lot of carbon, too. By capturing carbon after the burning, directly from air, we get the benefit of nature's work before we do ours. We bat last, in other words, in the cleanup position.
The Metzger-Benford (MB) idea appeared in Climatic Change 49: 11–19, in 2001. It's simple, low tech:
Collect crop residues
after the harvest. Take only the easy bits from above ground and those that are not needed to control soil erosion. Float this downstream on This barges to use as little fuel as possible, out into river deltas or the deep ocean. Drop it overboard. Let gravity take it below the "thermocline," so that the carbon the residue releases into the oceans does not return to our air for at least a thousand years, and perhaps longer.
This has big advantages. It:
(a) uses biomass that is now mostly left to rot in the fields,
(b) demands no new land,
(c) uses residues that can be gathered and shipped with the same equipment and people used to bring in the crop,
(d) requires no new technologies or transport systems to gather and ship the residues, and it
(e) is a post emission process.
Further, available crop residues increase with population growth since food production rises with population.
Why put it in the sea? Because the deep oceans already sequester the vast bulk of the world's carbon—over 99%. The oceans are not CO2 saturated, they can hold much more, and the deep ocean circulates carbon back to the surface in millennia. Carbon left 4 km down will not return to our air for about 8000 years. The deeper we put it, the better.
Even this is a worst case. Residues left exposed on the ocean floor have their decay byproducts easily enter into the waters. Embedding them beneath the ocean floor during sinking, or by subsequent covering from silting or other covering mechanisms, as in river deltas, makes this time much longer. Below ocean depths of about 1 km lies the thermocline, where there is little oxygen and temperatures are only a few degrees above 0 C. This oxygen-starved environment mixes with surface waters very slowly.
Simply dropping baled waste, with weights attached to ensure that trapped air does not make the bales float, should then sequester the waste. (The weights could be made of carbon-rich solid wastes that, left on land, would normally decay into CO2; this sequesters more carbon.) To make doubly sure, and extend the sequestering time, one might shape the waste into cylinders with conical weight heads. These 'carbon torpedoes' would penetrate the bottom sediments to several meters, sealing in decay products. This may prove particularly useful, since then trapped methane or CO2 can attain the concentration where stable hydrates of methane or CO2 form, securing the carbon for very long times. Simply offloading farm waste into an actively depositing river delta like the Mississippi's can bury it within days as later river silt falls upon it. This, too, secures the carbon for a long while.