Stabilization Wedges (Part 4)

Okay, here are the last two of Pacala and Socolow’s stabilization wedges. Remember, these wedges are ways to reduce carbon emissions. Each one is supposed to ramp up from 2004 to 2054, so that by the end it reduces carbon emissions by 1 gigaton per year. They claimed that seven wedges would be enough to keep emissions flat:

In Part 1 of this series we talked about four wedges involving increased efficiency and conservation. In Part 2 we covered one about shifting from coal to natural gas, and three about carbon capture and storage. In Part 3 we discussed five involving nuclear power and renewable energy. The last two wedges involve forests and agriculture:

14. Stop deforestation, start reforestation. They say we could stop half a gigaton of carbon emissions per if we completely stopped clear-cutting tropical forests over 50 years, instead of just halving the rate at which they’re getting cut down. For another half gigaton, plant 250 million hectares of new forests in the tropics, or 400 million hectares in the temperate zone!

To get a sense of the magnitude here, note that current areas of tropical and temperate forests are 1500 and 700 million hectares, respectively.

Pacala and Socolow also say that another half gigaton of carbon emissions could be prevented by created by establishing approximately 300 million hectares of plantations on nonforested land.

15. Soil management. When forest or grassland is converted to cropland, up to one-half of the soil carbon gets converted to CO2, mainly because tilling increases the rate of decomposition by aerating undecomposed organic matter. Over the course of history, they claim, 55 gigatons of carbon has gone into the atmosphere this way. That’s the equivalent of two wedges. (Note that one wedge, ramping up linearly to 1 gigaton/year for 50 years, adds up to 25 gigatons of carbon by 2054.)

However, good agricultural practices like no-till farming can reverse these losses — also reduce erosion! By 1995, these practices had been adopted on 110 million of the world’s 1600 million hectares of cropland. If this could be extended to all cropland, accompanied by a verification program that enforces practices that actually work as advertised, somewhere between half and one gigaton of carbon per year could be stored in this way. So: maybe half a wedge, maybe a whole wedge!

I’ve seen a lot of argument about both these topics, and I’d love to learn more facts. Some of the controversy concerns the UN’s <a href="REDD+ program, which got a big boost in Cancún. “REDD” stands for Reducing Emissions from Deforestation and Forest Degradation — while the plus sign hints at the the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks.

Some people think REDD+ is great, while others think it could actually hurt. The Wikipedia article says, among other things:

REDD is presented as an “offset” scheme of the carbon markets and thus, will produce carbon credits. Carbon offsets are “emissions-saving projects” that in theory “compensate” for the polluters’ emissions. Offsets allow polluting governments and corporations, which have the historical responsibility to clean up the atmosphere, to buy their way out of the problem with cheap projects that exacerbate social and environmental conflicts in the South. Moreover, it delays any real domestic action where a historical responsibility lies and allows the expansion of more fossil fuel explorations and extractions. The “carbon credits” generated by these projects can be used by industrialised governments and corporations to meet their targets and/or to be traded within the carbon markets.

There’s also a lot of argument about just how much long-term impact on atmospheric CO2 a standing forest has, though everyone seems to agree that cutting one down releases a lot of CO2.

For a bit more, try:

About REDD+, United Nations.

REDD+: Reducing Emissions from Deforestation and Forest Degradation, Center for International Forestry Research.

Next time I’ll give you a update on the stabilization wedges from Stephen Pacala himself, based on a talk he gave in 2008. It’s a bit scary…

28 Responses to Stabilization Wedges (Part 4)

  1. SteveB says:

    Digressing slightly, can anyone tell me if the following method of power generation is practicable:

    1) allow an area of forest to grow naturally; trees and little furry animals alike

    2) at the appropriate time, clearcut

    3) chip and dry logs (plus any little furry animals that didn’t get out of the way in time), perhaps using waste heat from the following step

    4) burn logs and generate power, releasing only water and carbon dioxide–but good, green, recycled carbon dioxide

    5) use ash as fertilizer for next round of forest growing

    • John Baez says:

      When you say ‘practicable’, what exactly do you want to know? I can think of a couple questions:

      1) is this method of power generation carbon-neutral?

      2) how much power can we generate this way?

      As for 1), just shooting from the hip, I’d guess the answer is close to ‘yes’. However, we’d probably sequester more carbon underground if we didn’t clear-cut the forest. So we have to also ask question 2), to see if the advantages of producing power from forests outweigh the advantages of using them to sequester carbon.

      As for 2), I don’t have the figures, but I believe growing trees and then burning them is a terribly inefficient way of turning solar power into either heat or electricity.

      Why do I believe this?

      I’m quite sure we can generate more power using vegetation that grows faster: trees grow more slowly than grasses like bamboo or switchgrass. But even these are quite inefficient ways of harvesting solar energy! David MacKay has summarized the situation for Britain as follows:

      Even leaving aside biofuels’ main defects—that their production competes with food, and that the additional inputs required for farming and processing often cancel out most of the delivered energy—biofuels made from plants, in a European country like Britain, can deliver so little power, I think they are scarcely worth talking about.

      Other countries get more sun. But still, growing plants to convert the sunlight into power seems rather inefficient. Here’s some data from the Azimuth Project article Biofuel.

      • A crop growing at the rate of 1 kilogram per square meter per year, with an energy content of 17 megajoules per kilogram, captures only 0.28% of the average incident solar energy of 200 W/m2.

      (This figure is from the US. The global average is more like 150 W/m2.)

      * The fast growing crop of Miscanthus (a kind of tall grass) is expected to have a growth rate of 3.7 kg per square meter per year. So, maybe it captures roughly around 1% of the solar energy.

      • Even the highly efficient sugarcane crop stores only 1% of the annual incident light as biomass.

      • Claims are, however, being made that bamboo will yield 15 kg/m2, e.g. by Bamboo Sur. If this is true, maybe it captures roughly 4% of the solar energy.

      • Zhu et al. have estimated that the maximum conversion efficiency of solar energy to biomass given an atmospheric CO2 concentration of 383 ppm and a temperature of 30°C is 4.6% for C3 photosynthesis and 6% for C4 photosynthesis: these are two ways that plants photosynthesize. But the highest efficiencies observed across a full growing season for C3 and C4 crops are quite a bit less: 2.4% and 3.7%, respectively.

      • According to recent projections, it may be possible to grow algae at a rate of 12 kilograms per square meter per year with 30% oil content by mass. Assuming that the oil portion of the algae has the high energy density of 33 megajoule per kilogram, the resulting annual solar energy conversion efficiency of 4.2% is more than twice what’s been demonstrated so far.

      • By contrast, solar power can be turned into heat energy at efficiencies of up to 70%!

      • Or, electricity can be generated from solar power either by a solar-thermal process or a photovoltaic module with efficiencies in the range of 10 to 42%. This is much higher, but we also need to take production costs into account.

      • Commercial photovoltaic modules with efficiencies approaching 20% are already available, and lab-scale multijunction tandem cells have shown efficiencies slightly greater than 40%.

      Of course, it’s easier for poor people to grow bamboo than to build solar cells! And, it takes energy to build solar cells. So, the efficiency of converting sunlight into usable power isn’t the only consideration.

    • Florifulgurator says:

      There are enough forests dying of bark beetle infestation. The decaying trees re-release stored carbon. Instead they should be pyrolized, the wood gas used for energy and the remaining char coal sequestered. Char coal does not decompose and is very useful in agriculture: Voila, CO2 negative energy!

      • John Baez says:

        Indeed, we’ve got a lot of trees dying from bark beetle infestations in Southern California. I tend to blame global warming; other opinions differ.

        For more on the virtues of charcoal for sequestering carbon, see:

        Biochar, Azimuth Project.

        Florifulgurator helped write this, so he doesn’t need to read it!

        In the Guardian, James Lovelock wrote:

        I said in my recent book that perhaps the only tool we had to bring carbon dioxide back to pre-industrial levels was to let the biosphere pump it from the air for us. It currently removes 550bn tons a year, about 18 times more than we emit, but 99.9% of the carbon captured this way goes back to the air as CO2 when things are eaten.

        What we have to do is turn a portion of all the waste of agriculture into charcoal and bury it. Consider grain like wheat or rice; most of the plant mass is in the stems, stalks and roots and we only eat the seeds. So instead of just ploughing in the stalks or turning them into cardboard, make it into charcoal and bury it or sink it in the ocean. We don’t need plantations or crops planted for biochar, what we need is a charcoal maker on every farm so the farmer can turn his waste into carbon. Charcoal making might even work instead of landfill for waste paper and plastic.

        Incidentally, in making charcoal this way, there is a by-product of biofuel that the farmer can sell. If we are to make this idea work it is vital that it pays for itself and requires no subsidy. Subsidies almost always breed scams and this is true of most forms of renewable energy now proposed and used. No one would invest in plantations to make charcoal without a subsidy, but if we can show the farmers they can turn their waste to profit they will do it freely and help us and Gaia too.

        There is no chance that carbon capture and storage from industry or power stations will make a dent in CO2 accumulation, even if we had the will and money to do it. But we have to grow food, so why not help Gaia do the job of CO2 removal for us?

        Biochar should probably be on Pacala and Socolow’s list of stabilization wedges, but it’s not.

        • DavidTweed says:

          This is not something I’m expert in, but I get the impression that ploughing non-edible parts of crops into the ground is important for returning certain chemicals back into the ecosystem (eg, according to wikipedia on soil fertility nitrogen, phosphorus and potassium, boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulfur, and zinc). Maybe this is incorrect, or there are other reasons why it doesn’t matter but I’d like to see some evidence that locking away carbon dioxide in biochar doesn’t also lock away other stuff.

        • John Baez says:

          I’d like to see some evidence that locking away carbon dioxide in biochar doesn’t also lock away other stuff.

          Good point, David. One small piece of evidence is that this article:

          Terra preta, Wikipedia.

          claims that biochar really helped boost soil productivity in the Amazon.

          Perhaps the other chemicals you mention are largely in the form of water-soluble stuff that gets leached out of the charcoal via groundwater at a reasonably quick rate.

          It’s easy to imagine that being true for various salts, like potash.

      • John F says:

        Charcoal does decompose eventually. Aerobically it decomposes much like many other polaromatics, especially with white rot and other wood rot fungi. Wengel et al., 2006, STE, “Degradation of organic matter from black shales and charcoal by the wood-rotting fungus Schizophyllum commune and release of DOC and heavy metals in the aqueous phase”.

        Anaerobically is always slower but can happen. Godsy et al., 2001, “Methanogenic biodegradation of charcoal production wastes in groundwater at Kingsford, Michigan”
        You would think that if anyone knew how to make charcoal it would be Kingsford.

        • Phil Henshaw says:

          The use of biomass for charcoal has been studied worldwide I think, but the interesting thing is the cost. A nice study estimated ~$160/tonCO2 as the cost to sequester CO2 with charcoal(from Nicholas Grey, published in SSPP,

          He was proposing that as a benchmark price for carbon pollution pricing generally, equal to the cost of burring it by present methods. The real problem, though, comes when you then estimate the cost of sequestering the average carbon produced by $1 of GDP.

          One dollar of GDP produces .47kg of CO2 on average, so at $.16/kg that’s a cost of ~$.08/dollar of GDP. It seems that sequestration that way would cost 8% of GDP…!

        • John Baez says:

          Thanks for the info on the cost of producing charcoal, Phil! I added it to a new section on costs in our biochar page.

          This paper gives the price of commercially manufactured bulk charcoal. I wonder if biochar that’s only good enough to stick underground can be produced more cheaply. It sure doesn’t need to be in the form of cute little briquettes.

          (I imagine that “bulk charcoal” ain’t cute little briquettes, but I don’t know what it looks like, and much work people put into into making it “nice”.)

          There are also economies and diseconomies of scale to consider. If we try to sequester lots of carbon by making charcoal, that means increasing charcoal production by a factor of 100, or 1000, or… I don’t know! So, using the 2009 price of bulk charcoal (about US$553 per tonne) to estimate costs could easily be off by a factor of 10.

        • Florifulgurator says:

          It seems Gray has forgotten to account for the energy harvested when producing charcoal. E.g. with proper design you can drive a car on wood gas, plus produce char coal. A more modern design would produce elctricity using a micro gas turbine in a hybrid car. For stationary use at home one could also use the heat. — That would be real modern technology. For the aspiring c21st technologist, here’s the open source Gasifier Experimenters Kit.

        • Florifulgurator says:

          John F wrote:

          Charcoal does decompose eventually.

          Your sources are about decomposition of byproducts of char coal production, like pyroligneous acid (wood vinegar) and polycyclic aromatic hydrocarbons.

          Some of these byproducts are valuable chemical resources, e.g. the “stone age super glue” birch tar.

          Other stuff, like many PAHs are toxic. That’s a troubling point I haven’t yet fully checked: You wouldn’t want much PAH in your soil. Luckily it is biodegradeable. That’s why I give my char coal composts 2-3 years before they go into the garden.

        • John F says:

          Charcoal and even coal biodegrades aerobically. Phanaerochaete chrysosporium, Polyporus versicolor, Poria monticola, Nematoloma frowardii, Neosartorya fischeri are among the organisms published as growing on and degrading chunks of coal. For most materials, charcoal and coal included, one of the best ways of degrading them is to grind them up and mix dilutely in topsoil in windrows.

          The fate of biochar is an active area of research.
          Nguyen et al., 2008, (in Long-term black carbon dynamics in cultivated soil. Biogeochemistry 89, 295-308.)
          found that biochar amended in agricultural soil degraded a lot in 30 years. The “magic agricultural processess” suppositions were recently put to rest in Nguyen et al., 2010. Temperature sensitivity of black carbon decomposition and oxidation. ES&T 44, 3324–3331.
          also at

          Click to access ES&T%2044,%203324-3331,%202010%20Nguyen.pdf

          It has been found by some researchers that the better effect of adding biochar to soil is to increase humification e.g.
          Liang et al., 2010, Black carbon affects the cycling of non-black carbon in soil. Organic Geochemistry 41, 206–213.

          Dias et al., Bioresour. Technol. 2010 101(4):1239-1246.

        • Florifulgurator says:

          John F,
          it seems you are confusing black carbon (soot) with char coal:

          The “magic agricultural processess” suppositions were recently put to rest in Nguyen et al., 2010. Temperature sensitivity of black carbon decomposition and oxidation. ES&T 44, 3324–3331.

          Note that one of the authors of this paper is Johannes Lehmann, the leading authority and advocate of biochar. Quoth paper:

          Black carbon (BC) is a highly recalcitrant form of C in soils and accounts for a considerable proportion of SOC, for example up to 45% (by mass) in German Chernozemic soils (7, 8), up to 35% in a range of US agricultural soils (9), and on average 20% for a continental-scale analysis of Australian soils (10).

          Chernozem black earth results from carbon matter (e.g. soot) generated in oxygen rich vegetation fires. In contrast, biochar is generated by oxygen-free pyrolysis.

          For more on biochar recalcitrance (mean residence time 1000 – 4000 years), plus an explanation of the other Nguyen et. al. paper (also coauthored by Lehmann) click here or buy the book by Lehmann & Joseph and see chapter 11. The intro chapter is freely available here.

        • John Baez says:

          Whatever you guys figure out — I’ll put it on our biochar page!

        • John F says:

          I think we agree to an extent. My point being that it, whatever form of black carbon, soot, char, coal, it degrades eventually. Bury it deep enough, or anaerobically, and it lasts a long time (for instance, there are coal mines …). But I don’t think we’re talking about refilling old coal mines with char.

          If you just mix with topsoil, it is degrading within decades, maybe centuries for chunks. That *is* extremely recalcitrant compared to say aliphatic petroleum, but not in the context of centuries of climate change.

        • Florifulgurator says:

          John F, methinks we don’t fully agree:

          You haven’t yet shown me a paper that says that biochar/charcoal (not soot or pyrolysis oils etc.) would degrade within decades.

          E.g. Amazonian terra preta is centuries (up to 2000y) old fertile human made soil that still contains comparably large amounts of char.

          But I’m with you in finding it worthwhile to examine the proportion of the faster (decades) degrading stuff in charcoal. That sure depends much on the char production process (temperature, residual oxygen), the feedstock and on the soil where it is worked in. E.g. resin rich wood (like fir) produces different char coal than hardwood (like beech). This is all quite difficult to quantify, and it looks soil science is just at the beginning here.

          Quantifying degradation gets even more difficult because of synergistic effects with soil life. The paradigmatic enigma is the apparent ability of terra preta to grow and sequester more carbon.

          E.g. arbuscular mycorrhizal fungi produce glomalin that stabilizes soil – and these fungi seem to love porous char coal.

          Little is known of the role plant species play in influencing accumulation of the fungal protein glomalin, even though it is composed of photosynthetically fixed carbon transferred directly to the fungi. Physical protection of soil structure by glomalin leads to soil aggregate stabilization. Aggregate stabilization in turn sequesters plant organic matter (OM) in recalcitrant pools and result in net OM storage in the soil.

          (From abstract here)

          This is just one synergistic effect.

          Alas I’ve started to compare my “super char coal soil” (50% char, against conventional wisdom) with conventional garden soil only late last summer. It turned out superior – but it looks the main reason is that it holds more water.

        • Phil Henshaw says:

          John, Yes indeed, for sequestration that “There are also economies and diseconomies of scale to consider.” is particularly relevant. It just gives you a way to establish a true market price point at present. It gives you the cost of sequestering the carbon for the average $1 of GDP, by the present cheapest standard method. If you were to spend $.15 per $1 globally, that would be 15% of GDP!!!

          The idea isn’t really to propose a solution directly, but to propose a more meaningful problem. If, as the author of the study intended, you want to set a realistic price for carbon sequestration, it’s better to start from an established market price for a real service, rather than just make one up based on judging what would be a “bearable cost” determined politically.

          That hardly anyone is even suspecting that this might have game changing economic consequences is just a bonus.

      • Frederik De Roo says:

        Florifulgurator said:

        they should be pyrolized, the wood gas used for energy and the remaining char coal sequestered

        Do you have some figures about how much energy the pyrolysis process consumes? (I haven’t looked through all the articles on the wiki yet, so apologies if it’s somewhere in those links.)

        From Pyrolysis, Wikipedia:

        Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. Pyrolysis typically occurs under pressure and at operating temperatures above 430 °C

        • Frederik De Roo says:

          Ah, I hadn’t seen Phil’s comment yet. Maybe it’s somewhere behind his link, as the cost for sequestering a ton of carbon dioxide probably includes the energy consumption of the pyrolysis process.

        • Florifulgurator says:

          Perhaps I shouldn’t have said Pyrolysis… From :

          In a wood fire, the visible flames are not due to combustion of the wood itself, but rather of the gases released by its pyrolysis, whereas the flame-less burning of embers is the combustion of the solid residue (charcoal) left behind by it.

          So, just flush or suffocate the embers when the flames are dying. I guess you then still have harvested most of the fire’s available energy.

          BTW, there are meanwhile many projects to supply the 3rd world with char producing, clean burning top-lit updraft gasifier stoves. The motivation is mostly to reduce indoor smoke health risks. I made one myself out of a steel thermo bottle, which I feed with wood pellets. It’s my c21st camping stove. The flame is amazing. Alas starting it takes some fireologic ingenuity and produces a little smoke…

        • “they should be pyrolized…” might have drastic effects on the Sulfur cycle. See the two last references by Donald E. Canfield, James Farquhar and Victor Brovkin, Vladimir Petoukhov, Martin Claussen, Eva Bauer, David Archer and Carlo Jaeger.

    • John F says:

      besides the “allow to grow” process you asked about and John Baez answered thoroughly, you may next ask about artificial growth. It turns out that having leaves competely covering every surface still does not generate near enough biomass or fuel or whatever you measure. The problem is that the limited photosynthetic capacity (Google “photosynthetic capacity” of leaves limits their carbon fixation ability. The great scientist Freeman Dyson imagined a genetically engineered supertree
      free from some natural limits but the numbers still don’t work out to produce nearly enough fuel for us. In addition, living plants can’t always photosynthesize at maximum capacity – they have other things that need doing: night respiration, growth, reproduction, etc.

  2. Leaving aside the real driving forces; human nature (greed-altruism), economy (rich-poor) and politics (right wrong incentives for import – export on national and regional levels). I would opt first for the former and ameliorate REDD+ to contain even more incentives and a working monitoring system both scientific trough eg and tru indepentent NGO´s and UN

  3. Breakthrough promises $1.50 per gallon synthetic gasoline with no carbon emissions

    By Mike Hanlon

    05:26 January 26, 2011

    I think that this from Harwell/Rutherford Lab.
    These are good scientists. If this is really true, it’s a game changer!

    • DavidTweed says:

      Let’s hope that this materialises. However, it’s important to remember that default practice in biofuels seems to be “announce early and announce incredibly overoptimisitcally”: most biofuels startups shut down before they’ve even produced fuel from a non-laboratory scale plant, let alone actually at the price they’ve publicised, as described in this post here.

  4. Phil Henshaw says:

    But if cheap energy came back, admittedly dubious, wouldn’t we just use it as we have… to multiply our control of environmental systems we don’t understand the real behavior or limits of? That’s really where all our environmental impacts are coming from, the direct effect of using energy to ever increasingly change nature to fit our needs, unaware of the consequences and the changing profitability of ever increasing scale effects.

    Is getting back to freely multiplying that the solution, or is it realizing how unprofitable that kind of investment becomes in the end?

  5. new_biochar_land says:

    The world is a great place, but it is falling apart and we all are responsible for this. Be responsible now and try to make it better.

    Biochar, one of the newest options, can contribute to atmospheric CO2 reduction. Find out more:
    The Biochar Revolution is exactly what it says !

  6. In Part 5, see Pacala reconsider the “stabilization wedges” plan based on new evidence.

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