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America's First Cellulosic Ethanol Plant

Posted by kdawson on Sun Jul 15, 2007 05:10 PM
from the sounds-corny-but-isn't dept.
hankmt writes "The state of Georgia just granted Range Fuels a permit to create the first cellulosic ethanol plant in America. Cellulosic ethanol produces ethanol from cellulose, which all plants have, instead of from sugar, which is only abundant in food crops. Corn ethanol only produces 1.3 units of energy for every unit of energy that goes into growing the crop and converting the sugar to ethanol. Cellulosic ethanol can produce as much as 16 units of energy for every one unit of energy put into the process. The new plant will be online in 2008 and aims to produce 100 million gallons of ethanol a year."
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[+] Science: New Wonder Weed to Fuel Cars? 484 comments
Hugh Pickens writes "Jatropha, an ugly, fast-growing and poisonous weed that has been used as a remedy for constipation, may someday power your car. The plant, resilient to pests and resistant to drought, produces seeds with up to 40 per cent oil content that when crushed can be burned in a diesel car while the residue can be processed into biomass for power plants. Although jatropha has been used for decades by farmers in Africa as a living fence because its smell and taste repel grazing animals, the New York Times reports that jatropha may replace biofuels like ethanol that require large amounts of water, fertilizer, and energy, making their environmental benefits limited. Jatropha requires no pesticides, little water other than rain and no fertilizer beyond the nutrient-rich seed cake left after oil is pressed from its nuts. Poor farmers living close to the equator are planting jatropha on millions of acres spurred on by big oil companies like British Petroleum that are investing in jatropha cultivation."
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  • by plover (150551) * on Sunday July 15 2007, @05:13PM (#19870933) Homepage Journal
    This isn't the first time I've read that corn yields 1.3 units of energy out for each unit put in (or some factor other than 1.3) But where does this number come from? And really, how far back does it go -- gas in the farmer's 4x4 inspecting his fields? Energy used to produce the fertilizer? The energy to produce the food the farmer ate?

    I'd like to know because it's so hard to compare with oil at that level. It's much easier for a consumer to simply look at the price on the pump. But that only tells us what the market is willing to bear (what the fuel is worth), not the true costs of production.

    • by aichpvee (631243) on Sunday July 15 2007, @05:17PM (#19870969) Journal
      It isn't about monetary value at all anyway. It's about corn being a poor source of material for producing ethanol because it is low in sugar. This type of ethanol works great in places like Brazil because they make it out of sugar cane.

      If it were just about the monetary cost of things even corn ethanol wins over oil, which would be $13/gallon or more if we started charging the oil companies for our military services.
      • Re: (Score:3, Interesting)

        At some point you have to say "It's not valid to count this as a cost." Why not charge military expenses to the existence of religious insanity? Why not add the cost of building roads to the price of oil? How about the cost of educating future oil company employees, or feeding them until they join the oil company?
      • Re: (Score:3, Interesting)

        You make a hell of a point. I say we fund the war through gas taxes. You want to end this war tomorrow add a $10 tax on gas to cover the cost of fighting for it. Even Congress might be on the people's side when it costs them $600 to top off their Hummer.
      • Sugar (Score:5, Insightful)

        by Mark_MF-WN (678030) on Monday July 16 2007, @12:55AM (#19873591)
        Thanks for not reading the article... or even the headline. The article is about CELLULOSIC ethanol. You know, cellulose? The stuff that isn't sugar?

        You can make cellosic ethanol from grass clippings, those bags of leaves that everyone is getting rid of each falls, fallen tree branches, corn husks, not to mention the tonnes of produce that each and every grocery store throws away every single day because it couldn't be sold.

        • These guys are going for ethanol though they also get some methanol, propanol and butanol. Look at step 2b here: http://www.rangefuels.com/conversion_process [rangefuels.com]
          --
          Solar power with no maintenance fee: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html [blogspot.com]
            • {sigh} you really must be new here. There's no need to be snide over a typo, and other than your pointless grammar-Nazism, you offered nothing of substance in your reply.
              Sorry, but going from "ethanol" to "methanol" isn't likely to be a typo, it's either an intentional manipulation to introduce FUD, or an outright error, or an example of dramatic ignorance of the topic. Wasn't sure which was the case, hence my question.


              Your inappropriateness aside, are you actually claiming that the Federal Government does not subsidize the conversion of corn into motor fuel? Huh. That's a remarkable degree of ignorance,

              And, that's a remarkable degree of "where the fark did you get that from what I wrote?".

              given the nearly forty billion dollars that Congress has given in such subsidies in the past decade. Your taxpayer dollars at work. In any event, just so you won't think that I'm making this up

              Yeah, whatever. Far as I'm concerned, better we subsidize biofuels from US sources, than give money to countries who hate us, so, yeah thanks for the link and all that but I don't see it as a problem. In fact I think we should subsidize the infrastructure for same, so we can get this stuff into production and stop pretending we like the arabs.

              You seem to have taken my question about "Methanol, who said anything about that, we're talking about Ethanol here" and expanded it into a series of assumptions, some amusing, and some outright wrong.

              I wonder why you do that.
              • If we stopped keeping sugar prices artificially high, and especially if we let Cuban sugar in, it would be amazingly cost-effective.)

                Cuban sugarcane is one reason the trade embargo hasn't been ended long ago, and why Brazilian sugarcane isn't being imported into the US. US sugarecane farmers, centered around Lake Okeechobee, FL, hold a lot of political clout.

                Falcon
    • by evanbd (210358) on Sunday July 15 2007, @05:26PM (#19871045)

      Comparing prices also gets subsidies (especially corn subsidies, but also renewable energy subsidies) involved.

      Those numbers certainly ought to include the energy content of the fertilizer -- it's decidedly non-trivial in comparison to the output energy, though I don't have a reference handy so I won't go quoting numbers. Most fertilizer is ammonium nitrate (or other nitrates), which is made from atmospheric N2 + H2 from fossil fuel sources (mostly natural gas, but also oil and coal to some extent). The ammonia is oxidized to nitric acid and reacted with more ammonia to form fertilizer AN, or used directly as anhydrous ammonia.

    • This is the ratio of fossil energy put in to energy out. Most of the fossil energy input for corn comes from nitrogen fertilizer which is produced using natural gas (though it does not need to be http://mdsolar.blogspot.com/2007/04/smelling-salts .html [blogspot.com]) and fuel used for harvesting and planting. Some distilleries also use natural gas. Forest waste products to be used here don't have any fertilizer inputs and much of the fuel used for harvesting would have been used anyway. Brazil is achieving some very impressive values for this ratio in its biodiesel production: http://mdsolar.blogspot.com/2007/05/juicing.html [blogspot.com]. On the energy out side, everything is really stored solar power.
      --
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    • But that only tells us what the market is willing to bear (what the fuel is worth), not the true costs of production.

      Actually, it's especially easy with gas. The 'demand curve' is so steep, usually quantity demanded remains very constant regardless of price (at least, in the short term, obviously).

      This is noted by gas taxes: the burden is almost entirely bore by the consumer, so an extra 18 cent tax adds nearly 18 cents to the price of gas because the companies know we'll pay it. In addition from gas taxes end up being nearly proportional to the rate.

      Compare this with something like cigarettes taxes: The companies actually reduce the price of cigarettes and end up paying (I'm guessing here, from my days as a smoker) roughly half of the tax. This is directly related to the demand curve and the nature of the market. In addition, revenues are not nearly proportional to the tax rate increase because people generally do buy many fewer cigarettes when they cost more. The companies have to balance the tax burden with their loss of revenues, and they hire really smart guys to do this.

      By the way, the emboldened words in this post are there to indicate trends and averages.
    • by Gibbs-Duhem (1058152) on Sunday July 15 2007, @06:52PM (#19871601)

      It comes from a selection of five papers from the late nineties which did the calculation in a number of ways. Generally, they attempt to account for the entire manufacturing process, from energy in oil used in fertilizers to fuel for farm equipment, to transport of the ethanol or corn, to the refineries that distill out all the water. I do not believe they go so far as to account for feeding the farmer, but I honestly suspect that is a very minor correction, as much as I like farmers.

      However, there is a fairly well known outlier which claimed to do a better job of accounting for processing costs. Pimentel and Patzek attributed what they claim are more accurate inputs to the agriculture, transport, industrial, and distribution components of the manufacturing process, giving the also oft-quoted value of around 25% energy *loss*. Ordinarily, people would probably dismiss that one given the seemingly overwhelming amount of contrary evidence, but Pimentel and Patzek are very well-respected scientists. It's difficult for me, as an energy researcher, to know who to believe. I suspect it's nigh impossible for people who only study this passingly.

      Personally, I'm inclined to believe that even if Pimentel et al are wrong, 1.3 is just way, way too low to be reasonable. Improvements to technology (as this plant represents), are the only way that ethanol can ever be practical. We'll see soon enough if it's as good as they claim.

      http://www.news.cornell.edu/stories/July05/ethanol .toocostly.ssl.html [cornell.edu] has a summary of the debate.

    • Re: (Score:3, Insightful)

      What they fail to figure is the opportunity cost of turning all of that cellulose into ethanol vs. its current use, which is largely animal feed and compost that is used to make products, as cover for off seasons, and to enrich soils for another season of crops. What is the energy cost of destroying your soil or offsetting the loss in other areas of the economy?

      The number comes from estimates that agricultural analysts make about the energy inputs of farm production. Human inputs are generally not considere
    • by Jerf (17166) on Sunday July 15 2007, @08:13PM (#19872177) Journal
      There's one and only one way to find out if ethanol-from-corn is a net win, or in fact any other alternative energy proposal: Strip it of all subsidies and throw it out into the marketplace. (More advanced students will note that we also need to internalize the appropriate externalities.)

      If it is in fact an energy-positive process, the extra energy can be sold. If the process is economically viable, then pretty much by definition of "economically viable" they will be able to run at a profit. If it is not, then they will eventually go out of business.

      Now, my point is not that this is desirable. It must be the ultimate goal of any alternative energy production system, but in the short-term you can make good arguments about subsidizing things to get over start-up costs, experiment with multiple things before we know which is the correct answer, etc. My point is simply that you can do math from now until the last drop of oil is pumped out of the ground and you won't really know whether such a marginal process is truly net-positive.

      That's the beauty of money; it's hard to wrap your mind around it, but if you just let it do its thing, it will automatically account for labor costs, equipment costs, etc., and with some judicious law making (which has a roughly 0% chance of happening) it can account for the externalities as well, and the final result will be obvious and unambiguous. It can even account for corruption and mismanagement etc., which are really real risks, not illusions. It's the only way to go from theory to reality.
  • by lecithin (745575) on Sunday July 15 2007, @05:15PM (#19870943)
    But hey, it is something.

    How would hemp do?
    • by Suicyco (88284) on Sunday July 15 2007, @06:56PM (#19871637) Homepage
      See here:

      http://fuelandfiber.com/Hemp4NRG/Hemp4NRGRV3.htm [fuelandfiber.com]

      Hemp is one of the top producers of biomass per acre. It is much better than corn and can be grown on fallow fields as well. And you can't even smoke this type of hemp, it grows 10-20 feet high and is all stalk with a clump of seeds at the top. Of course, nobody ever smoked this form of hemp, even when it was one of the primary cash crops of the south prior to the 1930's.

      Too bad, since hemp is evil. It makes you rape white wimin: http://www.oddfrog.com/paper.htm [oddfrog.com]
    • Re: (Score:3, Informative)

      Hemp, while good, isn't the best. It'd work in most climates, at least, and is certainly better than a lot of choices for yield per acre.

      Switchgrass is one of the better ones. It grows everywhere and is very disease, drought, etc resistant. You can't kill the shit even if you try and it requires very little, if any, maintenance. For longer term crops, depending on the environment type, poppler and willow are good choices. The nice thing about fast-growing trees is that if your refining process gets tied up,
    • How would hemp do? (Score:5, Informative)

      by falconwolf (725481) <falconsoaring_2000&yahoo,com> on Sunday July 15 2007, @09:30PM (#19872583)

      In 1892 Rudolph Diesel designed his engine and ran it on vegetable oil. He used hemp oil amoung them. Then in the 1930s Henry Ford built a vehicle not only using hemp [wikipedia.org] in the construction but was fueled with alcohol made from hemp, hemp he grew on his Iron Mountain Estate. Hemp was found to be a good source for fuel. Also in the 1930s MIT did a study showing an acre of hemp produced more paper than an acre of forest. Eventually some who felt threatened by hemp's industrial uses pushed to make it illegal and via the 1937 Marijuna Tax Act [wikipedia.org] and between them they were successful.

      Falcon
      • by Dunbal (464142) on Sunday July 15 2007, @05:31PM (#19871087)
        you would then have all these people getting upset over people smoking it instead of using it for fuel.

              But like, chill out, man. I mean, who needs to drive to work after smoking one of these, man? I use less fuel by staying at home. Hemp is a win.... god I am hungry
      • Re: (Score:3, Informative)

        Your understanding is a little twisted. It isn't "producing C02", it's shortening the carbon cycle to the point where we are using plants that have grown as recently as a few months ago for energy. The carbon in the plants was removed from the atmosphere by said plants. There may be no net reduction in C02 in the atmosphere over time by using cellosic alchohol, but burning fossil fuels presents a dramatically different situation. The carbon in fossil fuels has been buried for millions of years. This process
      • In theory, the CO2 that is released from burning the ethanol is reabsorbed by the plants used to make the ethanol, so there's no net CO2. This is why ethanol and biodiesel fuels are the darlings of many environmentalists. In practice, there are other CO2 costs involved, such as (probably) fertilizer, transportation costs, conversion costs, etc. (By "costs" here, I'm referring to CO2 output and nothing else. Of course, there are other costs involved as well.)

        Still, it's probably much better than burning fossil-fuels with respect to CO2 output.

        • Re: (Score:3, Informative)

          When you use forest waste products there is no fertilizer involved so this really reduces the amount of fossil fuel input. They do need quite a lot of heat input for their process so they may be less efficent than enzyme processes, but they are ready to go into production now.
          --
          Solar power without the permit hassles: http://mdsolar.blogspot.com/2007/01/slashdot-user s -selling-solar.html [blogspot.com]
        • Re: (Score:3, Interesting)

          In theory, the CO2 that is released from burning the ethanol is reabsorbed by the plants used to make the ethanol, so there's no net CO2

          In theory, the place where you are growing corn or sugar cane was already occupied by CO2-absorbing plants, either natural ones or food-destined ones. If we remove natural forest to plant sugar cane / corn, it's even worse: we're destroying stuff just to get fuel, instead of just taking it from the underground.

          This is why ethanol and biodiesel fuels are the darlings of ma

          • by StarKruzr (74642) on Sunday July 15 2007, @07:48PM (#19872019) Journal
            The existence of advocacy for both cellulosic ethanol and algae-derived biodiesel shoots your ridiculous envirowhackery full of holes.

            Biodiesel is not a carbon SOURCE. Petrodiesel is a carbon source in that it takes carbon that was NOT part of the biospheric carbon cycle before and MAKES it part of the carbon cycle.

            This is not hard to understand. Try retaking 9th-grade earth science, chief.
          • Re: (Score:3, Insightful)

            If we remove natural forest to plant sugar cane / corn, it's even worse: we're destroying stuff just to get fuel, instead of just taking it from the underground.

            You do realize that a oil wells, pipelines, refineries and all the other related infrastructure is going to destroy a lot more natural plant life than a farm, right?

            And since lots of US farmland is actually fallow to keep food prices up, using that land for fuel crops would probably be a good idea.

            They don't give a crap about the environment an

  • Cellulosic? (Score:5, Funny)

    by Icarus1919 (802533) on Sunday July 15 2007, @05:23PM (#19871013)
    What the hell kind of adjective is that? It's bullshity.
  • by gregor-e (136142) on Sunday July 15 2007, @05:25PM (#19871041) Homepage
    DOE has ponied up $385 million [energy.gov] to six different cellulosic ethanol plants, one of which is Range Fuels.
  • Skeptical (Score:5, Interesting)

    by Bombula (670389) on Sunday July 15 2007, @05:26PM (#19871049)
    You have to be careful of these kinds of companies' claims. I remember getting interested in a biodiesel-from-algae-grown-vertically project run by an outfit called Global Green Solutions (www.globalgreensolutions.com). They claimed to be able to get 150,000 gallons per acre per year, which is 1000 times the output of oil palm and other biodiesel crops - and 15 times more than other folks' projections for regular algae ponds. It all sounded great, until the basic calculations showed that their 'projections' would have meant converting 85% of the TOTAL solar energy directly into stored energy in the fuel - a physical impossibility. I called their bluff, and they just shrugged and said, "our 100-million-gallon-per-year plant will be open next year and then you'll see." Well, it's now next year, and you can imagine what happened. Nothing.
    • Re: (Score:3, Interesting)

      I think your math was off...

      1 gallon of BioDiesel is about 130,000 BTUs or energy. 150,000 gallons is thus 19,500,000,000 BTUs.

      Realistically, sunlight energy at ground level is about 100 watts per square foot, plus or minus. At 43,560 sq.ft. per acre, that's 4,356,000 watts per acre of raw sunlight.

      Assuming a cautious 5 hours a day, every day, of sunlight at that wattage, a year will net you 4356000 watts * 365 days * 5 hours/day * 3600 sec/hour = 28,618,920,000,000 total incident joules of sunlight.

      19.50E9
      • Re:Skeptical (Score:5, Informative)

        by Bombula (670389) on Sunday July 15 2007, @08:27PM (#19872249)
        Here's another calculation:

        The energy contained in 150,000 gallons of diesel @85% = 150,000 gallons/year x 133,000 BTU/gallon x .000293 kwh/BTU = 5.8MMkwh/year acre. The energy falling on one acre of land = 5kwh/m2 - day x 365 days/year x 4046 m2/acre = 7.4MM kwh/year - acre. 5.8/7.4 = .78. That is about 78% efficiency in converting sunlight to liquid energy.

        I incorrectly remembered the 85% figure, which is a different measure, but it's still in the same neighborhood.

        Looking at your calculation, you seem to have forgotten to convert BTUs into joules. 1 BTU = 1,054 joules. That put your calculation out by a factor of 1000. You got 0.07%, when the actual number is closer to 70%.

        I wish you were right though.

  • Nip / tuck (Score:5, Funny)

    by Zombie (8332) on Sunday July 15 2007, @07:18PM (#19871825) Homepage
    Hmm? America making fuel from cellulite? What a good idea. There's certainly plenty of it.
  • by Soong (7225) on Sunday July 15 2007, @07:36PM (#19871943) Homepage Journal
    just sayin, that'd be awesome.
  • by r_jensen11 (598210) on Sunday July 15 2007, @07:39PM (#19871959)
    I know that the existing ethanol production systems have enormous tolls on our groundwater supply. How does using cellulose compare? Remember: there is more to the environment than just emissions. One of the last things we need is the Great Plains to become The Great Dunes
  • I'm worried (Score:3, Insightful)

    by bagsc (254194) on Sunday July 15 2007, @07:43PM (#19871983) Journal
    If cellulosic ethanol works, say goodbye to things that are mainly made of cellulose, like rainforests. You think Indonesia gives a shit where the ethanol they sell you comes from? There's something much worse than global warming, and that's deforestation. If this technology works, its more dangerous than nuclear power to the ecology, and we need to be very careful who learns how to use it.
    • Re: (Score:3, Insightful)

      See your point, and I share in your general concern. However cellulosic ethanol, as produced using Range Fuel's proprietary technology, can be produced from just about any green biomass.. including corn stalks, cobs, switchgrass, sugar cane, agricultural waste, pig shit and wood chips/sawdust.

      What encourages me about this is we will be able to produce a very efficient, clean burning fuel domestically. As will just about any country that can grow wheat straw, corn or whatever else. Remember this is just

  • First? (Score:3, Interesting)

    by dbIII (701233) on Sunday July 15 2007, @07:58PM (#19872075)
    Hang on - I'm way over in Australia and more than six months ago I heard a radio interview with people running an ethanol plant on cellulose in the USA (North Dakota or Montana - not sure which state). Australia's ABC science show ran the story but the podcast and transcripts have most likely gone by now.
  • by heroine (1220) on Sunday July 15 2007, @08:09PM (#19872143) Homepage
    The fuel cell laptop was supposed to appear a few years ago. Still waiting for that one. Coal liquefaction was supposed to appear a few years ago. Still waiting for that one. Now a startup is promoting cellulose liquefaction.
  • by J.R. Random (801334) on Sunday July 15 2007, @09:05PM (#19872451)
    That is by far our most perpetually renewable resource.
  • by Animats (122034) on Sunday July 15 2007, @10:50PM (#19872991) Homepage

    OK, first we get past the blogodreck from some site that wants traffic, and look at the Range Fuels site. [rangefuels.com]

    This is funded by Kosla Ventures, which is Vinod Kosla's venture capital fund. That's a good sign; he has a decent track record as a VC. (He was one of the founders of Sun, but he later invested in Excite.) Anyway, they're not looking for money; they've got that.

    People have been working on cellulostic ethanol for a while. It's not that hard to do; it's hard to do cost-effectively. Here's an overview of the known approaches. [purdue.edu] Range Fuels uses a heat-driven process, which of course takes energy to run, but is standard chemical engineering. There's other R&D underway to develop a bioengineered enzyme that will digest cellulose at commercially feasible rates. Such enzymes have been created, but they're too slow and making the enzymes costs too much. Work continues.

    Anyway, this doesn't look like the big cellulostic ethanol breakthrough. But it's progress.

    • by Vader82 (234990) on Sunday July 15 2007, @05:46PM (#19871175) Homepage
      I don't mean to be contrary, but spewing carbon into the air isn't a bad thing. Its introducing EXTRA carbon into the air that hasn't been there for millions of years thats a bad thing. If we stopped pumping oil out of the ground today and instead used biofuels of whatever variety you like (biodiesel, ethanol, etc) that would be enough. The carbon in the air would get sucked up by plants as they grow, we would harvest said plants for the energy they have locked up, and we would use it.

      The carbon-hydrogen class of molecules have excellent energy storage properties, from methanol (CH4) up to octane (C8H18). Some have higher energy density, cleaner burning, etc. Humanity has around 100 years of investment into the internal combustion engine and it would be wise not to do away with that until we've found something SIGNIFICANTLY better. And by significantly, I don't mean 20-30%. I'm thinking more like 100-300% before it really looks worthwhile.

      Anyhow, if we stopped introducing EXTRA carbon back into the surface carbon cycle thats been sitting locked away for the last 10M+ years that'll be enough to do one of two things: stop any potential increase in surface temperatures OR show us that there is a different cause than CO2 causing warming.
        • Re: (Score:3, Insightful)

          And that's only 85% if you consider industrial waste from a turkey processing plant to be "usable energy". If you consider the fact that they can run off of completely useless waste products, and feed 15% of their output back into the plant to power it, this is essentially free energy, AND a reduction in landfill contents.
    • Re:Free energy (Score:4, Informative)

      by Terminal Saint (668751) on Sunday July 15 2007, @06:08PM (#19871317)
      That's for one unit of energy WE use to produce it; all that solar power that goes into it is what we're getting out.
    • No, you idiot. (Score:4, Informative)

      by MrTrick (673182) on Sunday July 15 2007, @06:24PM (#19871411) Homepage
      X amount of raw cellulosic product in, plus 1 unit of energy to power the process.
      The output is enough ethanol to generate 16 units of energy.

      In practice, these plants often loop part of the output back to power itself, so the process is simplified to:
      X of raw cellulosic product in, 15 units of energy out.

      Which is pretty cool.
        • by Dogtanian (588974) on Sunday July 15 2007, @06:46PM (#19871573) Homepage

          America is one huge continent. The USA is the only country that splits it.
          Wrong; they are called "North America" and "South America" in the UK, and probably many other countries too.

          Why do you think there are 5 rings in the olympic symbol? The 5 continents: America, Europe, Africa, Asia and Oceania.
          Let me tell you something; at its thinnest point, the connection between North and South America is significantly narrower than that between Africa and Asia.

          More significantly, I have *never* seen a truly convincing argument or explanation as to why Europe and Asia are (or were ever) considered separate continents- it seems to be a cultural distinction, which has nothing to do with physical geography. At any rate, North and South America are *far* more separate then Europe and Asia are.

          Ironically, you can see this in the picture that you linked to.
          • Re: (Score:3, Informative)

            The continents I was taught were:
            • Eurasia.
            • Africa.
            • North America.
            • South America.
            • Australasia.
            • Antarctica

            According to Wikipedia, Australasia is actually a part of Oceania, although the only time I've seen the term Oceania used before has been in 1984, to refer to the the Americas, the British Isles, Australia, and a few other scattered bits of the world.

            In the linked map, this is the '6 continent' model, although their map calls the south-eastern continent 'Australia,' rather than 'Australasia,' which ca

    • Re: (Score:3, Informative)

      Actually, plants get carbon from the air, and they do it for "free" (solar energy by way of photosynthesis). It's nitrogen that's the issue. It takes energy (and quite a bit of it) to reduce atmospheric nitrogen to a form that plants can use for protein. Fertilizer supplies nitrogen. That's where the carbon "footprint" comes in, since industrial fertilizer production burns carbon (or some alternative energy, of course).
    • Re:Carbon neutral? (Score:5, Informative)

      by jeff4747 (256583) on Sunday July 15 2007, @08:10PM (#19872157)

      Plants mine soil for carbon.

      There's your problem, right there.

      Plants mine the air for carbon. They literally suck up CO2 in their leaves and use sunlight to break it into C and O2. (Technically the 02 from CO2 is turned into glucose, and two Os from H2O are released as O2)

      Plants mine soil for other minerals they need to grow, mostly nitrogen to make amino acids.

      Petroleum-based fertilizers are primarily Ammonium nitrate, which contains no carbon at all. In fact, carbon would be an undesirable contaminant in fertilizer.

      In addition, there are bacteria that are able to get nitrogen out of the atmosphere, and several species of plants incorporate these bacteria in a symbiotic relationship. If you use the bacteria, you don't need nearly as much fertilizer.