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Existing forests aren't good biofuel sources. You'd be better off mining the oceans, tbh. Neochloris oleoabundans or even industrial rapeseed are just so much m

Existing forests aren't good biofuel sources. You'd be better off mining the oceans, tbh. Neochloris oleoabundans or even industrial rapeseed are just so much more dense sources of fuel...

pfdietz 4y ago
Mining the oceans? How does that work? A forest should be a much denser source of carbon, particularly reduced carbon, than the ocean. CO2 fixed per hectare per year should be much higher in lignocellulose than in seed oils. And if the forest is already there, you don't even have to wait for it to grow. The temptation to strip mine forests will be strong.
- cbsmith 4y ago
  > Mining the oceans? How does that work? A forest should be a much denser source of carbon, particularly reduced carbon, than the ocean. Algae tend to grow in large clumps, and you can very efficiently filter for them from water. I don't think it's a great strategy, but it's more practical than extracting from forests. > CO2 fixed per hectare per year should be much higher in lignocellulose than in seed oils. Forests are definitely way better for CO2 capture, but we're talking about producing fuel here. I'm speaking in terms of the net energy produced per hectare, so factoring in the energy consumed to extract fuel, industrial rapeseed oil beats the forest every day of the week.
  - pfdietz 4y ago
    I don't know of any algae, anywhere, that are more concentrated sources of carbon than existing trees. Even if we had to grow both sides, algae are still problematic, since separating them from water is apparently quite a difficult problem. Yield of rapeseed in the US in 2020 was 2.16 tonnes/hectare/year. Yields of lignocellosic biomass (dry mass) in the US (miscanthus, eucalypt) is almost an order of magnitude higher. Above ground forest biomass in Guyana: 499 tonnes/hectare.
    - cbsmith 4y ago
      > I don't know of any algae, anywhere, that are more concentrated sources of carbon than existing trees. Even if we had to grow both sides, algae are still problematic, since separating them from water is apparently quite a difficult problem. Again, we're talking about land use for the energy you get, not the carbon it stores. Algae have a distinct advantage when it comes to metrics with land use in the denominator, since they don't use any land. ...and pulling algae from water is significantly easier than pulling biomass out of forests. I'm not sure what you're getting at there. > Yield of rapeseed in the US in 2020 was 2.16 tonnes/hectare/year. Yields of lignocellosic biomass (dry mass) in the US (miscanthus, eucalypt) is almost an order of magnitude higher. Yup, the other stuff is much heavier per hectare for sure. That doesn't make it a better source of fuel. Having more mass just means it takes more energy to move it. Step 2 is you extract fuel from it.
      - pfdietz 4y ago
        No, I was talking about the temptation of mining existing biomass. The focus on yield was a change of subject. But even then, algae is greatly overhyped, for a number of reasons. First, as I mentioned, separating it from water is something of a showstopper (and no, it's not easier than cutting down trees). Second, it rapidly reproduces, with a generation time much shorter than a growing season, so keeping out undesirable wild species is difficult. Third, high yields require a lot of CO2, to the extent that simply absorbing CO2 into a pond isn't enough; instead bioreactors with an external source of CO2 are needed. That vastly increases capital cost over a simple field (and if the CO2 is from combustion of fossil fuels, then that's a fraud not a zero CO2 source of fuel.) Evaporation of water will be a big negative. Algae might work if one can get species that grown in extremely alkaline conditions, with water that can be sprayed into the air and recovered to scrub CO2 into the solution from the air. There are algae that grow in suck alkaline lakes. To get around the wild contamination problem would likely require engineering the algae to survive some kinds of poisons, then filling the water with those poisons as well to kill everything you don't want there. This wouldn't be very environmentally friendly. You still have the water separation problem, now made harder by the water being alkaline and toxic. > Yup, the other stuff is much heavier per hectare for sure. That doesn't make it a better source of fuel. Having more mass just means it takes more energy to move it. Step 2 is you extract fuel from it. The huge problem with biomass is the land requirement. That yield for rapeseed would be crippling for that crop as a fuel source for an economy.

Existing forests aren't good biofuel sources. You'd be better off mining the oceans, tbh. Neochloris oleoabundans or even industrial rapeseed are just so much more dense sources of fuel...

pfdietz 4y ago

Mining the oceans? How does that work? A forest should be a much denser source of carbon, particularly reduced carbon, than the ocean. CO2 fixed per hectare per year should be much higher in lignocellulose than in seed oils. And if the forest is already there, you don't even have to wait for it to grow. The temptation to strip mine forests will be strong.

cbsmith 4y ago
> Mining the oceans? How does that work? A forest should be a much denser source of carbon, particularly reduced carbon, than the ocean. Algae tend to grow in large clumps, and you can very efficiently filter for them from water. I don't think it's a great strategy, but it's more practical than extracting from forests. > CO2 fixed per hectare per year should be much higher in lignocellulose than in seed oils. Forests are definitely way better for CO2 capture, but we're talking about producing fuel here. I'm speaking in terms of the net energy produced per hectare, so factoring in the energy consumed to extract fuel, industrial rapeseed oil beats the forest every day of the week.
- pfdietz 4y ago
  I don't know of any algae, anywhere, that are more concentrated sources of carbon than existing trees. Even if we had to grow both sides, algae are still problematic, since separating them from water is apparently quite a difficult problem. Yield of rapeseed in the US in 2020 was 2.16 tonnes/hectare/year. Yields of lignocellosic biomass (dry mass) in the US (miscanthus, eucalypt) is almost an order of magnitude higher. Above ground forest biomass in Guyana: 499 tonnes/hectare.
  - cbsmith 4y ago
    > I don't know of any algae, anywhere, that are more concentrated sources of carbon than existing trees. Even if we had to grow both sides, algae are still problematic, since separating them from water is apparently quite a difficult problem. Again, we're talking about land use for the energy you get, not the carbon it stores. Algae have a distinct advantage when it comes to metrics with land use in the denominator, since they don't use any land. ...and pulling algae from water is significantly easier than pulling biomass out of forests. I'm not sure what you're getting at there. > Yield of rapeseed in the US in 2020 was 2.16 tonnes/hectare/year. Yields of lignocellosic biomass (dry mass) in the US (miscanthus, eucalypt) is almost an order of magnitude higher. Yup, the other stuff is much heavier per hectare for sure. That doesn't make it a better source of fuel. Having more mass just means it takes more energy to move it. Step 2 is you extract fuel from it.
    - pfdietz 4y ago
      No, I was talking about the temptation of mining existing biomass. The focus on yield was a change of subject. But even then, algae is greatly overhyped, for a number of reasons. First, as I mentioned, separating it from water is something of a showstopper (and no, it's not easier than cutting down trees). Second, it rapidly reproduces, with a generation time much shorter than a growing season, so keeping out undesirable wild species is difficult. Third, high yields require a lot of CO2, to the extent that simply absorbing CO2 into a pond isn't enough; instead bioreactors with an external source of CO2 are needed. That vastly increases capital cost over a simple field (and if the CO2 is from combustion of fossil fuels, then that's a fraud not a zero CO2 source of fuel.) Evaporation of water will be a big negative. Algae might work if one can get species that grown in extremely alkaline conditions, with water that can be sprayed into the air and recovered to scrub CO2 into the solution from the air. There are algae that grow in suck alkaline lakes. To get around the wild contamination problem would likely require engineering the algae to survive some kinds of poisons, then filling the water with those poisons as well to kill everything you don't want there. This wouldn't be very environmentally friendly. You still have the water separation problem, now made harder by the water being alkaline and toxic. > Yup, the other stuff is much heavier per hectare for sure. That doesn't make it a better source of fuel. Having more mass just means it takes more energy to move it. Step 2 is you extract fuel from it. The huge problem with biomass is the land requirement. That yield for rapeseed would be crippling for that crop as a fuel source for an economy.