Well, I have always believed Bio-Diesel was better, and now it is officially scientific fact. Less imputs, lower emissions, higher energy density and larger net energy density.

And as for not being able to replace all petrol in the US? Haven't we been threw this a dozen times now? Algea could easily satiate demand for only 1% of arable land.

Trouble is only 1 company is currently making BD with algea, but I am sure it will catch on once the benefits become clear.

Now if only Toyota and Honda would come out with that Plug in Diesel Hybrid we all know is the future of transportation we could all get to the business of screwing over the Saudis.

Adam -

(a) in GHG terms, biodiesel is more attractive well-to-wheels than almost anything else out there right now. Unfortunately for US consumers, it's still diesel, which means it still generates a lot of NOx. You'll be hard pressed to find a MY 2007 vehicle to put it in (Mercedes E320 CDi is the ONLY one to limbo under the newly-lowered emissions bar, at a price tag few can afford).

Even the larger trucks and buses will have to meet Tier 2 Bin 8 or better by MY 2009, with fleet average emissions at Tier 2 Bin 5. This is already the case with LDVs today. No company wants to be in a position in which government regs limit its ability to meet market demand for any one technology. That is why VW and Honda have said they will not introduce new diesel models until they have a drivetrain that can meet Tier 2 Bin 5. Wrt NOx, which has proven hardest to deal with, that limit implies an improvement of over 87.5% over state-of-the-art turbodiesel technology (without expensive aftertreatment or HCCI). Since even the US cannot afford to run all of its trucks and buses on gasoline, that probably means SCR and area additive is coming to the US, even if EPA and CARB don't much like it.

(b) There are algae species which produce lipids, which may be used as a biodiesel feedstock. However, there are many more that produce starches instead, which can be converted into simple sugars and various alcohols far more easily than cellulose can. Ergo, it may be more useful to talk about algal fuels than about algal oil.

However, youre assertion regarding algal productivity is correct only if the pools they are grown in are artificially enriched with CO2, e.g. by bubbling scrubbed and cooled flue gases from coal-fired power plants over them. That means intensively farmed algae ponds will not be carbon-neutral.

(c) If PHEVs are a good idea (debatable on asset depreciaton, range etc.) and diesels are a good idea (debatable on emissions), the the combination must be the ultimate Good Idea(tm), right? Perhaps for in-town buses, garbage trucks etc. Not necessarily for LDVs, though: the bulk, weight and cost of the drivetrain would turn them into instant Edsels.

For countries other than the US, diesel microhybrids (e.g. Citroen C2) are useful for eliminating emissions due to idling. Lower compression ratios (14-15) would be permit lower engine weight and cost, as well as better weight distribution for subcompact diesel applications. The fuel economy gains from replacing the gasoline engine would vastly overcompensate the slight reduction in thermodynamic efficiency. The main reason compression ratios remain so stubbornly high (17-21) is the difficulty in igniting the fuel in very cold weather.

I agree, especially concerning soybeans. It is a terrible food source and would serve much better as a fuel source. Unless fermented, soy beans and soy products should never be consumed by humans (even fermented there is still a propensity for the chemicals in soy to moderately inhibit mineral and protein absorption).

Rafael-- since we're burning coal by the megaton anyway, and will continue doing so for the forseeable future, why not bubble that CO2 through an algal pond instead of just blowing it up the smokestack? Ok, so it's not carbon-neutral, but if it can reduce (or eliminate? someday?) the use of fossil petroleum in our vehicle fleet, it's gotta be better than what we're doing now! Doesn't it?

Sewage treatment plants produce sizeable amount of biogas, 50% of which (by mass, by volume it is about 35%) is carbon dioxide. Biogas could be combusted directly on lean burn high compression gaseous fuel diesel generators (due to CO2 dilution with very low NOx emissions), and after stripping from sulfur components, used to heat up anaerobic digesters, and exhaust, incredible rich in CO2, could be used to enhance algae growth. Additional advantages could be direct use of fertilizers from secondary wastewater treatment, and usually STP are surrounded by wide strips of unpopulated land due to odor nuisance, which could be used for algae ponds.
Just a thought…