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Legit question here, not snark. How could this possibly be better than something like an algae based biofuel? Have self-replicating, solar-powered machines do t

by pfooti 9y ago

Legit question here, not snark. How could this possibly be better than something like an algae based biofuel? Have self-replicating, solar-powered machines do the CO2 extraction and reduction work on their highly specialized membranes. Then use the product? I get that this sounds fancy, but I'd be surprised if they can be even close to energy neutral pulling power from the grid to reduce the CO2 into hydrocarbons. At best, their plan just externalizes the carbon cost to the generator infrastructure (which could be renewable, sure, but again: plants are solar-powered as well).

coredog64 9y ago
AIUI, getting algae to scale is a big problem. Not 'nuclear fusion' hard, but difficult all the same. We've got more experience with mechanical and chemical processes at industrial scale, so this is easier.
88e282102ae2e5b 9y ago
I've only looked into this a little bit, but I think one problem is that you're limited by either nitrates or phosphates, depending on whether the algae are being grown in ocean water or fresh water. Either way you have to supply some kind of nutrient, which has to be either mined or synthesized in some energy-intensive fashion.
- timmaxw 9y ago
  Could you recover those nutrients when you convert the algae into diesel?
dredmorbius 9y ago
Scale and parasites. Algae are, at best, about 10% efficient at converting sunlight to fuel. To meet present U.S. petroleum neds, you might, say, put grow ponds on the east and west coasts. They would have to extend 1500 miles north-south and be about 60 miles across. That is an ambitious project, to put it mildly. Then you'd need to fertilise the ponds, drain effluent, and keep anything other than you (or your fuel harvesters) from munching on all those gigajoules of hydrocarbon energy. Fisher-Tropsch seawater-sourced synfuel would reqire a few square km of plant, and roughly 180 miles squared of solar power feed. In a world of grossly intractable fuel / energy alternatives, that's not completely beyond reason. https://www.reddit.com/r/dredmorbius/comments/22k71x/us_navy_electricitytofuel_synthesis_papers_and/ https://www.reddit.com/r/dredmorbius/comments/22k71x/us_navy...
gwbas1c 9y ago
Algae based biofuels need a lot of land. This process uses less land.

by pfooti 9y ago

coredog64 9y ago

AIUI, getting algae to scale is a big problem. Not 'nuclear fusion' hard, but difficult all the same. We've got more experience with mechanical and chemical processes at industrial scale, so this is easier.

88e282102ae2e5b 9y ago

I've only looked into this a little bit, but I think one problem is that you're limited by either nitrates or phosphates, depending on whether the algae are being grown in ocean water or fresh water. Either way you have to supply some kind of nutrient, which has to be either mined or synthesized in some energy-intensive fashion.

timmaxw 9y ago
Could you recover those nutrients when you convert the algae into diesel?

dredmorbius 9y ago

Scale and parasites. Algae are, at best, about 10% efficient at converting sunlight to fuel. To meet present U.S. petroleum neds, you might, say, put grow ponds on the east and west coasts. They would have to extend 1500 miles north-south and be about 60 miles across. That is an ambitious project, to put it mildly. Then you'd need to fertilise the ponds, drain effluent, and keep anything other than you (or your fuel harvesters) from munching on all those gigajoules of hydrocarbon energy. Fisher-Tropsch seawater-sourced synfuel would reqire a few square km of plant, and roughly 180 miles squared of solar power feed. In a world of grossly intractable fuel / energy alternatives, that's not completely beyond reason. https://www.reddit.com/r/dredmorbius/comments/22k71x/us_navy_electricitytofuel_synthesis_papers_and/ https://www.reddit.com/r/dredmorbius/comments/22k71x/us_navy...

gwbas1c 9y ago

Algae based biofuels need a lot of land. This process uses less land.