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The idea being that producing the biofuel took carbon from the atmosphere (in particular algae crops [1]), vs releasing co2 that had been sitting harmlessly und

• WalterBright 3y ago
  Let's say you have a log from a tree you just chopped down. You have the same amount of wood dug up as coal. Each emits the same CO2 when burned. Where is the net decrease in CO2? What difference does it make being fossilized?
  • bryanlarsen 3y ago
    Carbon neutrality means "no net increase" not a net decrease.
    • WalterBright 3y ago
      I do know what the words mean. Throwing the log in a landfill (or building a house with it) would accomplish the same thing, and is a heluva lot cheaper.
      • bsk26 3y ago
        Except it'll probably still decay into co2 in the landfill while the coal underground is stable
        • WalterBright 3y ago
          Block off the oxygen supply (like how coal became coal) and they won't decay into CO2.
      • OkayPhysicist 3y ago
        The difference is that no one is paying me to bury a bunch of logs. The fact is, there is ample demand for high density energy storage. People want to go places, people want stuff brought to them. Until battery technology makes a massive leap into the realm of eating roses and shitting rainbows, combustible fuels are the only economically feasible option. In that realm, our options are A) keep digging up fossil fuels, then burning producing a bunch of C02, or B) capturing a bunch of C02, turning it into biofuel, then burning it to release the same amount of C02. Put in simple math terms: Fossil fuels: net CO2 = CO2 from energy to extract + CO2 from burning Biofuels: net C02 = CO2 from energy to extract + (CO2 from burning - CO2 from growing) = CO2 from energy to extract
        • WalterBright 3y ago
          Your equation overlooks simply growing trees. Build houses with the lumber instead of burning them.
          • bryanlarsen 3y ago
            Have you run the numbers on that? It takes 10 years to grow a tree. How many trees does it take to sequester gigatonnes of CO2? Some trees are useful, that many trees aren't.
            • WalterBright 3y ago
              > How many trees does it take to sequester gigatonnes of CO2? Are you saying biofuels are not only ineffective at reducing CO2 emissions, but impractical as well?
  • rainsford 3y ago
    I'll caveat this by stating I'm not an expert in the area, but the obvious difference seems to be that I can keep growing more trees to burn, while the only way to keep burning coal is to dig up more of it. Burning a tree may release the same amount of CO2 as burning the coal, but the carbon in the tree was taken out of the air during the growing process, so the total amount of CO2 hasn't changed over the lifetime of the tree. Burning the coal releases previously stored carbon without a way to "re-store" it since new coal isn't being created at nearly the rate we're burning it. Really burning the tree would have the same problem if you were burning them far faster than new trees were growing, but the idea is that you don't do that. The problem with fossil fuels is have no way of restoring it remotely as fast as we're burning it, so the net amount of carbon in the air has to go up.
    • WalterBright 3y ago
      Nobody said you had to burn the trees you grow. If you want to remove CO2 from the air, just grow the trees. There's no difference between burning the tree you grew and burning the tree you dug up in the coal bed.
  • OkayPhysicist 3y ago
    You're missing the fact that I'm also growing said trees. If I plant a bunch of trees to sell the lumber as firewood, I turn around and plant more trees so I can sell more wood in the future. Those trees capture the C02 released by the first batch, and then I sell them again. This is especially true with algae ponds, because 1) there's no chance there was an existing algae pond that would put me 1 batch in the hole on carbon neutrality and 2) it takes a lot less energy to grow and harvest. In contrast, digging up coal has no carbon recapture stage. I dig up coal, it gets burned, releasing C02, I dig up more coal. No one's saying biofuel is carbon negative. But it's pretty close to carbon neutral.
    • WalterBright 3y ago
      > You're missing the fact that I'm also growing said trees. But you can grow trees and capture carbon anyway, and not burn them.
      • OkayPhysicist 3y ago
        Sure. But the conversation here is about biofuel. Leet's say I want to fly to London because I'm sick of the gorgeous weather in California. In order for aviation to exist, we need energy storage substantially denser than what batteries can currently provide. Our options are A) Biofuel, which captured CO2 in its development, or B) Fossil Fuels, which did not. A) is objectively the superior option, because buying said biofuel puts an economic incentive on the guy making the biofuel to keep capturing more CO2 to make more biofuel, resulting in ~about carbon neutrality. B) releases a bunch of CO2 that has been sequestered since long before you or I ever existed. If you want to pay purely to sequester carbon, go for it, buddy. Nobody's stopping you from going to your local tree farm, buying a tree, and burying it. That's your perogative. But your buried tree doesn't get me to my Jack the Ripper street tour or whatever.
        • WalterBright 3y ago
          Burning a log you just cut is no different from burning a log you dug up. You've accomplished nothing whatsoever in reducing CO2 emissions.