Thanks. There's still lots of problems though.
From 1978 to 1996, the U.S. Department of Energy\ufffds Office of Fuels Development funded a program to develop renewable transportation fuels from algae. The main focus of the program, know as the Aquatic Species Program (or ASP) was the production of biodiesel from high lipid-content algae grown in ponds, utilizing waste CO2 from coal fired power plants. Over the almost two decades of this program, tremendous advances were made in the science of manipulating the metabolism of algae and the engineering of microalgae algae production systems. Technical highlights of the program are summarized below:
[...]
Over the course of the program, efforts were made to establish the feasibility of large-scale algae production in open ponds. In studies conducted in California, Hawaii and New Mexico, the ASP proved the concept of long term, reliable production of algae. California and Hawaii served as early test bed sites. Based on results from six years of tests run in parallel in California and Hawaii, 1,000 m2 pond systems were built and tested in Roswell, New Mexico. The Roswell, New Mexico tests proved that outdoor ponds could be run with extremely high efficiency of CO2 utilization. Careful control of pH and other physical conditions for introducing CO2 into the ponds allowed greater than 90% utilization of injected CO2. The Roswell test site successfully completed a full year of operation with reasonable control of the algal species grown. Single day productivities reported over the course of one year were as high as 50 grams of algae per square meter per day, a long-term target for the program. Attempts to achieve consistently high productivities were hampered by low temperature conditions encountered at the site. The desert conditions of New Mexico provided ample sunlight, but temperatures regularly reached low levels (especially at night). If such locations are to be used in the future, some form of temperature control with enclosure of the ponds may well be required.
[...]
A major conclusion from these analyses is that there is little prospect for any alternatives to the open pond designs, given the low cost requirements associated with fuel production. The factors that most influence cost
are biological, and not engineering-related. These analyses point to the need for highly productive organisms capable of near-theoretical levels of conversion of sunlight to biomass. Even with aggressive assumptions about biological productivity, we project costs for biodiesel which are two times higher than current petroleum diesel fuel costs.
[...]
Algal biodiesel could easily supply several \ufffdquads\ufffd [7.5 B gallons] of biodiesel\ufffdsubstantially more than existing oilseed crops could provide. Microalgae systems use far less water than traditional oilseed crops. Land is hardly a limitation. Two hundred thousand hectares [772 sq. miles] (less than 0.1% of climatically suitable land areas in the U.S.) could produce one quad of fuel. Thus, though the technology faces many R&D hurdles before it can be practicable, it is clear that resource limitations are not an argument against the technology.
So the process uses injected CO2 from power plants, presumably to reduce CO2 in the atmosphere and to increase the growth rate of the algae. Thus some way of collecting and transporting the CO2 would be needed. If CO2 were just taken from the air, then the algae production would be less.
While it seems to be a promising technique, it's never going to be cheaper than oil pumped from the ground. That's not an argument against it, per se. It needs a lot of area. It needs a lot of water. It needs a lot of light, CO2 and warm temperatures for best efficiency. 20 years of research is a long time. All of these factors don't preclude the use of biodiesel from algae, it's just that it's not a clear win for this technology. We'd have to see numbers on other alternatives to see whether this was a better choice than shale oil or something else.
Their numbers do seem to add up though:
50 g of algae per square meter per day. 1 sq mile = 2.6 M square meters. Assuming 100% conversion efficiency of algae to biodiesel and 7.6 pounds per gallon of oil, then for 7.5 B gallons/yr you would need:
7.6 pounds / gal = 3447 g / gal of oil
7.5e9 gal / yr = 2.59e13 g / yr of algae required per quad (at 100% eff.)
50 g * 365 days = 18,250 g / m^2 / yr of algae per square meter per year
2.59e13 / 18,250 = 1.42e9 m^2 = 528 sq miles for 7.5 B gallons/yr
Current US road diesel consumption is ~ 33 B gal/year (2000 number cited earlier), so 528 * 33 / 7.5 = 2323 sq miles. Still not a huge amount, even recognizing that the algae to oil efficiency is closer to 50% than 100%.
I think that the main problems with this technique are:
1) Water.
2) CO2 collection, storage and transport.
Farming the algae in pens in the sea somewhere around the equator help would solve the water requirement and temperature control problems. But if CO2 injection is necessary to get reasonable oil generation rates from the process, then some land-based process would probably be needed. Water is already a problem in the southwest. Moving an additional ~ 1-10 M acre-feet of water out to the desert every year would put a huge strain on the system. Even if the algae could tolerate brackish water, an infrastructure would be necessary to get the water from the sea (or wherever), and what would be done with the salts, etc., that remained?
Your [link|http://www.unh.edu/p2/biodiesel/article_alge.html|UNH] article from 2004 addresses some of these issues. It uses the efficiency numbers from the NREL study, but it doesn't seem to mention the necessary collection of CO2 from power plants so I don't know whether they're ignoring that cost or not using it. But the numbers don't seem to add up:
At the cost of $80,000 per hectare, that would work out to roughly $308 billion to build the farms.
The operating costs (including power consumption, labor, chemicals, and fixed capital costs (taxes, maintenance, insurance, depreciation, and return on investment) worked out to $12,000 per hectare. That would equate to $46.2 billion per year for all the algae farms, to yield all the oil feedstock necessary for the entire country. Compare that to the $100-150 billion the US spends each year just on purchasing crude oil from foreign countries, with all of that money leaving the US economy.
If the cost of biodiesel is twice that of natural diesel, how would the total annual cost be one third to one half that of imported oil? (Yes, the timeframes of the reports are different, but it still seems that something doesn't add up.) He does assume that all transportation vehicles will convert to biodiesel, leading to a natural reduction in fuel requirements (due to the increased efficiency of the diesel), but that's something that won't happen in less than 10 years...
If biodiesel were really 1/3 to 1/2 the cost of diesel people would be jumping all over it. My cynical mind tells me that even with oil at $55/bbl, biodiesel is still more expensive than diesel. IIRC, the costs of a barrel of oil from oil shale always increased with the price of oil as well (you need natural gas or petroleum to run the process, transport it, etc.).
If/When oil goes to $150/bbl in a few years, some of these alternatives will become more attractive, but the economics will likely continue to be biased toward the stuff pumped from the ground. The political balance will, however, tilt more strongly toward alternatives.
My $0.02.
Cheers,
Scott.