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How about algae as a solution for your miles-per-acre problem ? By pairing a high-oil content algae with CO2 enhancement from smokestack output:

"One key is selecting an algae with a high oil density — about 50% of its weight. Because this kind of algae also grows so fast, it can produce 15,000 gallons of biodiesel per acre.

For his part, Berzin calculates that just one 1,000 megawatt power plant using his system could produce more than 40 million gallons of biodiesel and 50 million gallons of ethanol a year. That would require a 2,000-acre "farm" of algae-filled tubes near the power plant. There are nearly 1,000 power plants nationwide with enough space nearby for a few hundred to a few thousand acres to grow algae and make a good profit, he says."

http://www.usatoday.com/tech/science/2006-01-10-algae-powerplants_x.htm

Algae sounds promising. Yields could theoretically be very high. The problem is that no one has figured out how to consistently produce really high yields or how to do it cheaply. In the past there was a lot of research done on open pond algae growing systems. A lot of money was spent, but no one figured out how to produce cheap fuel from algae. Now they are focusing on closed systems (plastic covered ponds, giant test tubes, etc.) where they can control the amount of sunlight the algae gets, control the temperature and nutrient levels, and keep wild algae and other contaminants out. These systems are obviously a lot more expensive to operate than open ponds (which weren't even close to being profitable in producing algae as a biodiesel feedstock), so they'll really have to get some fantastic yields to justify the high up front and continuing costs of closed systems. I hope they succeed, but they still have a lot of hurdles to overcome before biodiesel from algae will ever be commercially viable. They might figure it out in the next couple of years, or maybe it will be twenty years, or maybe it will never work. We'll see.

I had to leave and couldn't finish my thoughts on the last post I made. I wanted to address a couple of claims made in the article you linked me to. This Berzin guy makes some very optimistic claims. Read what he says and pull out your calculator and the things he says do not add up though.

First off, he says that you can get 15,000 gallons of biodiesel per acre from algae. That's never been done, but most researchers in this field seem theorize that yields that high are obtainable. They hope to do this with high oil content varieties of algae, which as Berzin states can be about 50% oil. Anyway, Berzin says that with a 2000 acre algae farm we could produce 40 million gallons of biodiesel and 50 million gallons of ethanol. That's where his math falls apart. First off, he assumes like many others that we could possibly get 15,000 gallons of biodiesel per acre from algae (even though it's never been done), yet he claims we'd got 40 million gallons from 2000 acres from the his system. Even if we could hit that Holy Grail 15,000 gallon per acre mark, 2000 acres would only be enough land for 30 million gallons, not 40 million (if every square foot of this acreage is covered by his giant algae test tubes). Folks trying to raise money for projects like this sometimes exaggerate a little I guess. What's 10 million gallons anyway?.

He also says we could get 50 million gallons of ethanol from 2000 acres using his system, in addition to the 40 million gallons of biodiesel. Wow. That sounds a little fishy to me. Biodiesel weighs in the neighborhood of 7 pounds a gallon. If the algae is 50% oil, and they get a pound of biodiesel for each pound of oil (they wouldn't get quite that because they have to remove the glycerine from the oil), they'd have 7 pounds of spent algae left for each gallon of biodiesel they produce. Now, it takes about 14 pounds of sugar to make a gallon of pure alcohol, or roughly the same amount of starch. A bushel of corn weighs 56 pounds and it's about 70% starch. That's why they can get 2.8 gallons of ethanol from each bushel. There is about 39.2 pounds of starch in a bushel of corn, 70% of 56 lbs., divide that by 14 (how many pounds of sugar or starch it takes to make a gallon of pure alcohol), and you get 2.8. Anyway, if this guy is able to do what no one has ever done and produce 15,000 gallons of biodiesel per acre from algae, and then do even better than that and somehow produce 40 million gallons from only 2000 acres, and if he's able to somehow turn each gallon of algae oil into a whole gallon of biodiesel and not have waste any in the process, he's going to end up with about 280 million pounds of spent algae to turn into ethanol. Now, if this 100% of what remains of the algae after extracting all this oil with no waste is starch or sugar, which it couldn't possibly be, he'd have enough starch or sugar there to make 20 million gallons of ethanol, not 50 million. He'd get a good bit less if he was using cellulosic ethanol processes to produce the ethanol, and it would cost a lot more.

There is a lot of excitement around alternative energy right now and a lot of money being invested. That's good thing overall because it increases the likelihood that we'll have some major breakthroughs. Investors need to be careful though because so much of what we are hearing about alternative fuels is b.s. This Berzin guy may be on to something, but his numbers do not add up. We need to take everything he says with a grain of salt, and should do the same on all of these wild claims made about unproven technology. If it sounds too good to be true, it probably is. A lot of these people appear to be making stuff up as they go along to get people to invest in their projects. This is dangerous for investors and not particularly helpful in the overall energy debate because too many people tend to believe the fluff they read in the news and act on their beliefs without having first checked out the wild claims they've heard with a healthy dose of skepticism.

I think there is a very good chance we'll come up with some type of biofuel concoction someday that we can produce at a reasonable cost and we'll be able to provide enough fuel for several people from each acre we use to produce feedstocks. There are 43,560 square feet in an acre. That's a lot of room to work with, and there are a lot of very bright minds working on this problem. We aren't there yet though, and anyone who says he knows how to do it right now needs to be taken with a healthy dose of skepticism because many before him have said the same and been unable to come even close to delivering on their promises.