For the two responses to my challenge; thank you, and also for the comment on last week's blog. I am going to leave the challenge open for another week, and add a further comment on biofuels.
There is little or no difference between a plan to do something and a theory on what should be done, and for producing biofuels there is no shortage of alternative theories as to what should be done. The question now is, should some basic analysis be done on the various options before we send vast sums of money after them? One argument is, until you do the research you cannot analyse the situation well enough to come to a conclusion. I would agree that you cannot make close decisions, and as noted in my previous blog, there will probably be a number of good solutions to this problem implemented. But surely we can avoid some obvious mistakes? Unfortunately, if the analysis is weak, it can be a mistake to "avoid obvious mistakes" when in fact they are not mistakes. Notwithstanding that, I can't help feeling that much of the money devoted to biofuels research is not well-spent. There is an adage, you can be fast, you can be cheap, you can be efficient; choose no more than two. I believe available capital is scarce in terms of the size of the problem and we want the solution to work. Accordingly, we should be more reluctant to jump onto the latest fashionable exercise.
The most obvious biofuel is ethanol, and the production of ethanol from fermentation of sugar is a technology that has been operating for about 6,000 years, so we have learned something about it. Currently, fuel ethanol is produced in Brazil from its sugar cane, in the US from corn, but growing crops for ethanol is not considered a likely solution, if for no other reason than with an expanding population, food becomes a priority. Of course, waste food can always be converted to fuel, but the size of the fuel requirements requires the bulk of the fuel to come from somewhere that does not compete with food production.
A more likely answer is to produce ethanol from cellulose by first fermenting the cellulose to make glucose. Also, because "biotech" has been very fashionable, this has received a lot of funding, but I believe any reasonable analysis will show this route is suboptimal. Most plant biomass contains polyphenols, such as tannins and lignins. The question is, why? The usual answer is that lignin binds cellulose and lets trees grow tall. I would argue that is a side-benefit, and the original reason for polyphenols to be incorporated into plant material is to make them more difficult to digest. Those that get eaten less reproduce more frequently and evolve to support that trait. In other words, lignocellulose has been optimized by evolution to avoid being digested by enzymes. Yes, nothing is perfect and we can find enzymes that will hydrolyse woody biomass, but the hydrolysis is slow. Ethanol manufacturing will seemingly commence with immense tanks of wood chip slurry that take days to ferment. If all the cellulose is converted to glucose, then the lignin, which is about a third of the mass, will be left as a finely divided and very wet sludge that is difficult to filter and which will contain a reasonable fraction of the glucose. In practice, much of the crystalline cellulose will not hydrolyse, but will merely expand the sludge.
Is this the correct way to go about the problem? It seems to me that theory suggests it is not, yet it appears that in recent times more money has been sent chasing this option than any other single option. Perhaps someone knows something I do not know and I am wrong in the assessment, but if so, whatever that is is not widely known.
