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What are you trying to say? Where are you getting this 1% efficiency nonsense? You're talking about solar cells and comparing electricity equivalent solar energy with fuel produced from crops. You're comparing seed crops with limited growing seasons to simple algae that can be grown year around. Whether we're talking about something like soybeans or rapeseed or sunflowers or whatever, these are plants that have to be spaced out and that have an awful lot of biomass that does not contain oil. The oil is in the seeds. Some of these algae strains they are working with are a good 50% oil and can be grown year around and be continually harvested. You aren't making valid comparisons and you aren't really making any sense.

All these people are saying is that they believe they'll get 100 times as much oil from an acre than current fuel crops. That's not very specific anyway, because our main biodiesel crop, soybeans, will only yield something like 40 or 50 gallons of biodiesel per acre, but there are other crops like rapeseed that we use for biodiesel that will yield a good bit over 100 gallons per acre, and oil palms grown in some parts of the world will yield better than 650 gallons per acre. I don't know what plants they are referring to when they say they'll be able to get 100 times more oil than "conventional soil-tilled crops."

Researchers gung ho about biodiesel from algae believe they'll be able to get many thousands of gallons per acre. I've even heard estimates as optimistic as 50,000 gallons per acre, but most seem to think it will be closer to 10,000 or less. They've already gotten some pretty fantastic yields but it's been too expensive and too hit or miss so far. They haven't been able to get consistent yields on large scale yet. Open ponds haven't worked out well because they are too easily contaminated with wild algae and other things that mess up their algae crops. They've also had problems with temperature sensitivity. They haven't settled on what particular types of algae they'll end up using, or whether they'll use a salt water or fresh or brackish water variety. We really won't know if any of this will work for large scale biodiesel production until it actually happens.

Could the produce several thousand gallons of biodiesel per acre from biodiesel? It actually looks promising. Could they do it at a low enough cost to compete with petro-diesel? That seems like the bigger problem, but maybe someday they'll succeed. There are about 43,560 square feet in an acre, just a hair under 4047 square meters. That's an awful lot of room to play with. Algae is a simple plant that is extremely efficient at photosynthesis. It eats up carbon dioxide and sunlight. It doesn't have a lot of excess parts not dedicated to photosynthesis. It grows quickly and like I said can be continuously harvested, year around if conditions are right. Oil content can be very high and extracting oil from algae has to be easier and take less energy than extracting it from hard seeds they have to crush up after stripping them from the rest of the plant material. Algae can be grown several inches thick, thicker if they have a way of agitating or otherwise moving it such that that farther below the surface will get enough light. Some of it grows fine in the shade. There seems to be a lot of potential.

It was my understanding that tilled crops turn something like 10% of incident solar energy into useable chemical energy, in which case, algae couldn't possibly be 100 times more efficient. You point out that algae can be grown year-round, as opposed to during one season, and now that you say it, I doubt that that factor was included in the 10% number that I recall. It might also be that tilled crops convert 10% of *absorbed* light into useful chemical energy, which is an additional inefficiency compared to *incident* light, and the algae could score another win there simply by being darker (which they often are).