Alcohol Fermentation

[megalomania]

I have undertaken a research project to put my lawn to work. I am interested in producing ethyl alcohol from cellulose containing materials for fuel use. While there is much information on fermentation for beer, wine, and even fuel alcohol, I am surprised at the lack of detailed information for cellulose conversion.

To bring people up to speed, cellulose makes up the vast majority of plants. Such materials as grass, wood, and newspaper would be valuable sources of fuel if only yeast could process the cellulose. Cellulose is polymerized sugar, and it must be processed to depolymerize it so that yeast may ferment it. The sources I have that discuss using regular grass seem to resign themselves to the fact that only about 7% is useful sugar, while writing off the other 93%. Theoretically you could use 100% of all your yard waste if only you could process the cellulose.

There are 3 ways in which cellulose can be converted into sugar. You can use a high strength acid process, a low acid process, or use an enzyme conversion process. It is these methods of conversion that I want hard data on. All I can find are references that these methods exist and are used, but I don’t have any information that tells me in no explicit terms how I can do it.

I am looking for companies that sell high alcohol yeast, cellulose converting enzymes or ways to culture/produce those enzymes, or yeast that can ferment cellulose. I know of some recent research that has produced a type of yeast that can directly ferment cellulose to alcohol (at Perdue University I think), and I want to know if I can get some of that yeast.

I would hate to rake up a ton of grass clippings only to have 140 pounds of sugar fermentable. I want to be able to raid the town recycling dump and turn all that newspaper into fuel. I want that $15 spent on BATF license form 2110.74 (license to distill alcohol for experimental and fuel purposes) to be worthwhile.

I am not looking for any beverage information. I am only concerned with getting the highest yield from cellulose materials. If you have any relevant information, please post it. There are a few useful books that my library no longer carries (some dumb fuck stole ALL of the alcohol fuel books damnit!) so I am out of luck in the literature department. If anybody knows of any ebookz or websites that have a pirated copy, please post em. These books are usually out of print, so they can’t exactly be bought either.

The last time I tried this I just dumped some yeast in a bottle of grass clippings in water. I got some really smelly crap, but no alcohol to my knowledge. Of course that’s what you get for not knowing anything at all. Now I am trying to go about this more systematically, but I am very disappointed at the lack of useful practical knowledge out there to get high yields from common materials. Why aren’t more people doing this, and why don’t the big companies publish more information? I have seen the phrase “proprietary information” about some cellulose conversion techniques. GRR! I think that means “classified secrets, screw you” if I guess right. Maybe this is too hard or perhaps nobody has done it yet. I hope some of you will be able to point me in the right direction.

[pyromaniac_guy]

Mega,
I know this isnt what you were asking for, but to the best of my knowlege all attempts thus far to produce alcohol fuel from biomass have resulted in a process that requires more energy to be expended than is provided by the generated fuel... if it was as simple as throwing some stuff in a vat of lawn clipings, do you think we would really give a crap about middle eastern oil????

[Eliteforum]

You have to have a license to distill alcohol?! That's outrageous!

[PYRO500]

I think that for this to work you may need to bleach the paper somehow with a substance that leaves the cellulose intact, and there should be some kind of enzyme that naturally breaks cellulose down into a simpler fermentable suger, does anyone know what the enzyme in cow's stomach's is ? The one that lets them digest grass? I think that if you could get some sort of enzyme juice running through your paper juice you could convert it to usable sugar. I tried making alccohol a few times with store bought yeast, I found that some of the diffrent packets that were in diffrent batches would ferment faster and some would stop quicker witch led me to believe the diffrent dates of yeast came from diffent batches of yeast causing some of them to perform better than others. you could get a bunch of diffrent batches of yeast and try them out cultureing the one that does best. I guess it's also possible to capture yeast from the air in a filter and randomly culture batches but I think that's needless. I beleve brewing supply companys will sell various brewing yeasts including high alcohol resistant yeast

[10fingers]

I've seen methods of converting cellulose to methanol by destructive distillation. I think this would be the easiest way of getting an alcohol from wood, cellulose, paper or other organic matter. If you're just going to use it for a fuel then methanol is just as good as ethanol.
As for ethanol I was looking into ways of making it at one time but the costs of production are much higher than what you can buy it for. The gas stations in my area are now selling 85% ethanol fuel for around $1.20 per gallon.
I do remember a process for ethanol though that used hydrochloric acid to break down the cellulose into sugars. I will have to dig through all my piles of shit to see if I can find it.
Also, I do have some plans for a reflux still for concentrating alcohol.

[Alchemist]

Hello Mega,

If you have NOT seen this web sight check it out!

<a href="http://journeytoforever.org/biofuel_library/ethanol_manual/manual8-10.html" target="_blank">http://journeytoforever.org/biofuel_library/ethanol_manual/manual8-10.html</a>

<a href="http://journeytoforever.org/ethanol_link.html#cellulose" target="_blank">http://journeytoforever.org/ethanol_link.html#cellulose</a>

Take care!!!

<small>[ July 09, 2002, 10:36 AM: Message edited by: Alchemist ]</small>

[xoo1246]

Good page actually. Thanks.

[Mr Cool]

Eliteforum: you need a licence to distil alcohol in the UK too. Where are you from?

[megalomania]

I am only interested in ethyl alcohol, not just for fuel, but mainly as a chemical feedstock, so methyl alcohol doesn’t help me much. I have the journeytoforever.com publication printed out, actually. It is that document that I was alluding to when I mentioned they just ‘give up’ when it comes to using cellulose from grass clippings.

I know the biomass conversion to fuel is not exactly economic, but I am not doing it on a large scale. My process assumes ample supply of biomass right from the backyard, hence no transportation, harvesting, or storage costs. I also don’t pay for electricity or water, so there are no operational expenses. I would use chemical reactants from other processes that I already do or plan to do, and I would do all of this from materials I already have, so there are no start up and equipment fees (for now).

I am thinking of trying a dilute sulfuric acid process that cooks the cellulose. I have waste sulfuric acid from my electrolytic production of magnesium hydroxide for magnesium metal. I have been pitching this acid because it is contaminated with magnesium sulfate. In theory if I used a more dilute magnesium sulfate solution I could achieve exhaustive electrolysis giving me a dilute but pure acid solution. I can use this acid as is for my cellulose hydrolysis.

I have an abstract that describes a general overview of what I want to do for now…
</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica">Dilute sulfuric acid treatment at elevated temperature is a method that can be used either as a pretreatment preceding enzymatic hydrolysis or as the actual method of hydrolyzing lignocellulose to the sugars. The first established dilute-acid hydrolysis process was probably the Scholler process. This was a batch process, in which the wood material was kept in 0.5% sulfuric acid at 11-12 bar for approximately 45 minutes. The first commercial Scholler plant was built at Tornesch, Germany, in 1931. Thereafter, several other plants were built in Germany, Russia, Italy and Korea in the 1930's to produce ethanol, glycerol and fodder yeast from the provided sugar solution. The process was able to produce 0.17 g of ethanol per g of dry wood. Almost all of the dilute-acid hydrolysis processes are performed in a batch mode with a retention time of a few minutes. However, there have been some studies concerning continuous hydrolysis in plug flow reactors.

An our recent work contains data for one-stage dilute acid hydrolysis, where 0.5% sulfuric acid was used at temperature of 188-234 °C and a retention time of 7 minutes. The results show that a major part of the hemicelluloses (more than 80%) can be hydrolyzed by dilute acid hydrolysis at temperatures less than 200 °C, but the maximum overall glucose yield occurred at a hydrolysis temperature higher than 220 °C. In no case was a better yield than 40% of the theoretical glucose yield from glucan obtained. Dilute-acid hydrolysis in two stages is a better process alternative in terms of sugar yield. In the first stage, which should be carried out at relatively mild conditions, hemicellulose is converted to sugar monomers. In the second stage, the residual solid is hydrolyzed at more severe conditions allowing cellulose to be hydrolyzed. When dilute-acid hydrolysis is used for pretreatment of lignocellulosic materials, the process is performed in milder condition than those mentioned above. In a one-stage pretreatment, a temperature between 140 to 170 °C can be used, but two treatments at about 120 °C may also be used.</font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">I am not too keen on the 12 bar pressure (about 12 atm) which will require me to buy stuff. I could use some more detailed information than this. I will have to check and see how much pressure glass can take, but the 12 atm, or ~180 psi, is most likely too much. If I have to go with a metal system, that means I have to get large diameter stainless steel pipe to resist the acidic conditions. There is some stuff at the Hive and at Rhodium’s site about wine bottle hydrogenation (pressure rxn’s) that I will see.
For me, the amount of time spent on the reaction is not a factor. If I could get away with a few atms at 100 degrees, and just do this over the period of a few hours that would be great. I want to know if there is any experimental data that supports this before I make the investment to do the experiments myself. The above process only needs 7 minutes at 188-234 degrees, but it did not mention a pressure. I want to know which factors (time, temperature, pressure, and acid concentration) influence hydrolysis. There must be some graphs out there somewhere.

[Alchemist]

Hello again,

Mega is this what you have found so far? If NOT, here's what I have so far!

Fuel From Sawdust

CAUTION

This procedure uses hazardous materials and anyone who attempts it does so entirely at his or her own risk.
Sulfuric acid is an EXTREMELY DANGEROUS CHEMICAL. Take full safety precautions, wear safety
goggles, gloves and apron. Take the advice of your chemicals supplier on industrial-standard protective equipment
that meets the required safety specifications. Have running water nearby. Don't inhale fumes! The workspace must
be thoroughly ventilated. No children or pets allowed. Try small test-batches first to familiarize yourself with the
process.

The conversion of cellulose, such as sawdust, cornstalks, newspaper and other substances, to alcohol is a fairly
uncomplicated and straightforward process. At the moment, it is a bit expensive; but that is hardly a problem that
needs to be addressed here. Just a few years ago the idea of running a car engine on alcohol was preposterous --
it was too expensive. Of course, back then gasoline was less than 50 cents a gallon. What might be uneconomical
at this writing might be a bargain by the time you read this.

Let's say you want to make alcohol from sawdust. There are two types of alcohol you can obtain from wood --
methanol and ethanol. Methanol can be obtained from wood by high temperature destructive distillation. Methanol
is also known as wood alcohol. The other method used to obtain ethanol involves converting the sawdust to
simple sugars, the usual fermenting by yeast, and the usual distillation of the fermented solution. There are a couple
of other steps involved prior to distillation that are distinct from the standard processes almost everyone is familiar
with. To save you the trouble of trying to remember whose book you read last week or where in this one you
need to rummage around in for the supporting information, I will provide the usual cookbook instructions.

The first step involves obtaining our standard piece of chemical engineering equipment -- the discarded 55 gallon
drum. You will need more than one.

The substances you will need to conduct the chemical phase of this operation are sawdust (for example), sulfuric
acid, water, and possibly some sodium hydroxide, NaOH.

For the mechanical segment, you will need standard window screens you can buy at the hardware store, plumbing
pipes, elbows, couplings, nipples, flanges, and a welding outfit.

I will describe this just the way my partner and I did it in the lab with the exception of some of the plumbing
connections. This is necessary because you can't pick up a 55 gallon drum between your thumb and forefinger the
way we do a test tube or beaker in the lab.

Be sure that you read all the way to the end before you put your hands on the chemicals. You might be
unpleasantly surprised.

STEP-BY-STEP PROCEDURES

Pour the sawdust you intend to convert to alcohol into the drum. Don't fill the drum more than one-third full or you
will be taking a chance on part of the process slopping over the sides of the drum.

Next, pour what chemists refer to as 18 Molar H2SO4, sulfuric acid, over the sawdust. The commercial
designation, if you order it from a chemical supply house, would be 100% sulfuric acid. However, as low as 91%
will work. We tried 9.2 Molar, or 51%, in the lab and it simply didn't work. It just sat there and looked at us.

Make sure that you put the sawdust in first. If you don't, the sawdust will float on top of the acid -- unless you
pour in more sawdust than the acid can absorb. In that case, you will simply have to pour in more acid anyway.
It's easier to do it right the first time.

When you pour the sulfuric acid on the sawdust, the reaction is almost immediate. The sawdust and acid react in
such a fashion as to turn black almost immediately. It resembles an ugly collection of coal tar or oitch. Bubbles rise
up through the solution. The bubbling is primarily due to air pockets inside the sawdust. Even though the reaction
appears to be instantaneous, you should let the mixture sit for a day or two to allow whatever reaction doesn't
take place at once to proceed at its own leisure.

Once the reaction is complete, you can simply dump in yeast and expect the mixture to ferment. The pH of the
mixture is so low, that is the substance is so acidic, that any microorganism such as yeast that you dump in is
simply going to explode. Of course, they will be very tiny explosions.

The proper procedure here is to supply enough water to raise the pH to the proper level for fermenting or yeast
propagation -- 5.0 to 6.0. In Kentucky, where the water is lightly acidic, diluting the solution 50% by adding an
equal volume of water will raise the pH to about 3.0. In areas where the water tends toward alkalinity (or is basic,
in chemical terms) the pH will go higher. If you don't want to keep adding water, add some sodium hydroxide,
NaOH, to raise the pH up to optimum conditions.

The trick here is that this mixture must be poured into the water used to dilute it with. If you pour the water onto
the acid, a natural inclination, what you will get is a loud hissing sound followed by acid vapors rising up out of the
solution to attack you. If you add the acid to the water, the dilution factor is much greater. The same reaction will
take place but on a much smaller, safer scale.

What takes place is an exothermic reaction. That is, large quantities of heat are liberated. You can get a good idea
of how much heat is liberated by simply placing your hand on the container during various stages of the
proceedings. Briefly put your hands on the drum when the sulfuric acid is poured on the sawdust and you will
experience the same discomfort that you would if you placed your hand in the middle of a hot frying pan. You will
get burned.

Once the solution has been adjusted to the proper pH, it is time to pitch in your yeast. A small packet of
Fleischman's, available at the local supermarket, will do just fine. Watch for bubbles of carbon dioxide to appear.
They might be hard to recognize coming up through the black gunk; 72 hours, or 3 days should be enough to
allow it to ferment completely.

A word of caution. You might think that simply diluting the acid with half water before you pour it on the sawdust
would save a lot of trouble. In a way it does. You don't have to worry about distillation if you do it like that
because 50% sulfuric acid won't convert cellulose to sugar and the yeast won't ferment anything else. We tried it
in the lab and it simply doesn't work.

LIGNIN

Before you run your solution into your still, you need to get as much of the black gunk, big gobs of it, out of the
solution. Remove as much as possible. The material is lignin or the substance that bonds sugar molecules together
to make cellulose out of them. In a chemistry lab you use a buchner funnel and filter paper. A buchner funnel has
tiny holes in the base. The filter paper is placed on the bottom, covering the holes, allowing the liquid to pass and
trapping practically all the lignin. For a barnyard operation, you can punch nail holes in the bottom of a 55 gallon
drum and cover them with newspaper.

Given the fact that the chunks of lignin in an outdoor operation will be much larger than those in a lab, you will
probably want to install a series of wire mesh screens between your fermentor and the eventual, modified buchner
funnel. The screens toward the fermentor should increase in mesh size and those toward the funnel should
decrease in mesh size.

The fluid that gets past the newspaper should be yellow in color. The filter won't catch everything. In the lab, we
observed a ring of small, brown flakes that settled to the bottom of our distilling flask. This fluid contains ethanol
and it is ready to be distilled.

At this point go back and scrape the lignin off the screens and remove the lignin-saturated paper from your funnel.
This is the fuel to fire your still with. There won't be enough to get the whole job done, but it will help and it does
eliminate the problem of what to do with all that black gunk. Just be sure you give everything a chance to dry out
before you try to light it.

The alcohol you get from distilling the yellow fluid is identical to that obtained from sugar or starch. We obtained
190 proof ethanol the first time through a fractionating column. The yield-per-pound appeared to be quite good.
According to most of the chemical literature we read prior to conducting this experiment, the commercial yield of
cellulose is far inferior to that of corn or other common feedstocks. However, a ton of cellulose (saw dust) is free
for the asking

In place of the sodium hydroxide, NaOH, that we used in the lab, you can substitute common garden variety lye
to adjust your pH. If you spill sulfuric acid on yourself -- it is a strong acid and it will burn -- dilute it with water
and scrub with soap. However, the soap should be one that lathers very well because the acid is a very strong
acid and the soap is a very weak base, or neutralizer. Lather the soap up well and use a lot of it.

Once you have distilled the alcohol, you can raise the temperature under your column and boil off the water.
Because the sulfuric acid has a much higher boiling point than water, you are simply repeating the distillation
process to recover whatever unused sulfuric acid is available from the bottom of your still. You can't recover
much of it because H2SO4 loses the two hydrogen atoms, or protons, in the initial reaction and is no longer
sulfuric acid.

In a commercial plant, the elements involved in the reaction could be recovered in the following fashion. It is a
process too long and involved to go into in detail here:

S02 + H20 ---- H2S04

P.S., check this sight also!

<a href="http://www.ott.doe.gov/biofuels/newsearchdb.cgi" target="_blank">http://www.ott.doe.gov/biofuels/newsearchdb.cgi</a>

<small>[ July 09, 2002, 05:57 PM: Message edited by: Alchemist ]</small>

[Mr Cool]

Mega: Is the increased pressure really necessary do you think? I can't see what it might achieve, other than stopping anything from boiling away. It can't be affecting any equilibria to any significant degree because there shouldn't be much of a pressure change during the reaction, there's no gas produced or anything.
IMHO, it could be done for longer, at a slightly lower temperature under reflux.

That thread about depolymerising teflon has got me thinking... I wonder if there's any way to depolymerise poly(ethene) effectively? Then you could react the ethene with steam to make ethanol, and you'd be doing your bit for the environment by getting rid of non-biodegradable plastic!

[megalomania]

Thanks for that info, Alchemist, and no I did not have that one. That link you gave at the end is a big tease, none of those publications are available except maybe for a price :( . That process strikes me as rather wasteful. If indeed most of the sulfuric acid is destroyed, I wonder what kind of sulfate is made in its place? Acid recovery is a key to doing this right. I have not yet found any data that deals with the acid recovery, although the above info is close when it mentions using the acid as a pH reducer and then recovering it after fermentation. That makes good sense.
I wonder if that process could be improved by cranking up the heat. I have seen some data that says low temperatures (30 degrees) can be fine if a very high concentration of acid is used. If a lower concentration is employed, perhaps heating will do the trick.

I suspect the high pressures are just for industrial scale procedures. They want to process things quick, and at great efficiency with a minimum of energy. Pressure is an easy thing to do if you already have all the equipment. From what I gather it is difficult to penetrate into the crystalline structure of cellulose. I hypothesize that the pressure helps the acid penetrate the structure better, and of course minimizes the time required to complete the reaction.

I found that ‘graph’ I wanted that compares temperature, acid concentration, and time. Its actually a data table, but I will be graphing the data to extrapolate some optimal conditions. These experiments make no mention of pressure, but I assume some is involved to achieve these kinds of temperatures. Anyway, to sum up the data they used sulfuric acid at 0.2 to 0.6%, cooked it for 8-20 minutes, and had the temp at 160-180 degrees. They found that concentration resulted in the biggest gain, with 0.4% being the best. The worst effect was temperature, the higher the temp got, the lower yields were if done for longer periods of time. This is good news from my perspective. Their best trial was 0.04% acid cooked to 170 degrees for 14 minutes. This resulted in 16.42 g of sugars per 100 g of wood. The higher temperatures favor the production of harmful byproducts like frufural alcohol, which can in turn hinder fermentation.
These experiments were geared to hemicellulose hydrolysis. Hemicellulose requires less harsh conditions to depolymerize. The % of hemicellulose in grass is about 15-25% and in wood it is about 20-30%. At best you can get around 75-90% of the hemicellulose converted into fermentable sugars. These experiments achieved 75% conversion. This may be a useful temporary measure to boost sugar concentration. The amount of acid is quite low, so recovery is not a big deal. The temperatures are reasonable, and the time is quite short. 15% more sugar is better than nothing. This would not help me if I use paper, and of course still leaves the bulk of the good stuff unusable.
This method may be a good pretreatment for the concentrated process though. After hydrolyzing the hemicellulose you could then subject the cellulose to more vigerous conditions. I did some more research and found that is exactly what they do industrially. This is a ‘pretreatment’ step for them. The conditions necessary to hydrolyze cellulose also destroys the hemicellulose products, and turns them into harmful fermentation hindering byproducts.

I do wonder if the conversion of cellulose is really worth it. This is the big problem that faces industry, and why it costs so much. Even under the best process they get about 50% conversion. Perhaps industry is only concerned with high yields, where I would be satisfied with a lower level of conversion. One must remember that industrial and laboratory conditions are rarely the same.

[Mr Cool]

What about a biological approach? Get some cow dung, cultivate the bacteria from it on grass clippings, paper, sawdust etc (to favour the ones that use cellulose), and use these to break down cellulose. I'm presuming, of course, that they do hydrolise the cellulose into sugars. A mixture of these bacteria and yeast may produce alcohol, or immobilise the cellulose-converting bacteria in some gel (I've forgotten the name of the gel used), and fill a tank with them. Fill it with cellulose-rich stuff, drip water in at the top and let water drip out the bottom, hopefully with sugars. Add yeast to this, and get alcohol.
Obviously it needs more thought than I can give it at this time of night (or is it morning now?!), but it's another potential option.

[Sam]

If my memory serves me correctly, disstillation of different things produces different flavours (obviously).

Vodka is from potatoes and grain.
Japanese rice wine from rice.
Mexican tequila is from (some) cactus.
and thats all i can remember at the moment.
I have a diagram that shows how to evaporate the alcohol but i dont know how to put it up here.
You need a condenser, a thermometer, a bunsen burner, a beaker, and thats all I can remember, if anyones interested I'll look it up, but if not, then I wont bother.

[cutefix]

The chemistry involved is simple:from a biochemical point,
Reduce cellulose to sugars by means of cellulases.Then add another enzyme (from yeast or bacteria) to convert the sugars to alcohol.There are other ways of doing this.
To convert cellulose to alcohol you must first convert these polysaccharides to simple fermentable sugars.Just as what alchemist said lignin should preferably be removed first.
Then an infusion made of the cellulose fibers are treated with cellulase enzyme.
Once it is broken down into digestible sugars;then you can pitch in yeast(preferably the distiller type because it can produce more alcohol than bakers or brewers yeast).
There are enzyme companies that are expert in these matter
See this one:
<a href="http://www.novozymes.com/cgi-bin/bvisapi.dll/portal.jsp" target="_blank">http://www.novozymes.com/cgi-bin/bvisapi.dll/portal.jsp</a>
There are detailed ways to do it
These URL looks informative,please check it out:
<a href="http://www.fao.org/docrep/w7241e/w7241e0b.htm" target="_blank">http://www.fao.org/docrep/w7241e/w7241e0b.htm</a>

[James]

I read in a book (don't remember the title it had a yellow cover with a breakdown of a still on the front) that there were a couple of organisms that might be useful. Clostridium Thermocellum and Thermoanaerobactor Ethonaculus (the names are probably spelled wrong).

[megalomania]

I am looking for the e-book (actually a zipped pdf file) called The Home Distillation Handbook, by Ola Norrman. I went to the website that is supposed to have it, <a href="http://partyman.se/HbBok/home_distilling_handbook.html" target="_blank">http://partyman.se/HbBok/home_distilling_handbook.html</a> and for a moment there I thought they were a bit nieve offering it for download first, and then asking for payment. But alas the file is not there, instead it is now on <a href="http://www.home-distillation.com/" target="_blank">http://www.home-distillation.com/</a> . The first link will automaticially transfer you after a minute or so (and quite sneakely you can't use your back button).

I of course want the english version. Does anyone have it?

[blazter]

while i dont have the specific book your looking for i do know of some web sites that probably have the same sort of information on them.
<a href="http://www.moonshine-still.com/page2.htm" target="_blank">http://www.moonshine-still.com/page2.htm</a>
this site is pretty much all devoted to plans for building various reflux stills that would be fairly large scale (compared to lab distillation aparatus). doenst get into theory of operation much but has some good practical advice.
<a href="http://www.homedistiller.org/" target="_blank">http://www.homedistiller.org/</a>
this is a fairly complete guide, which includes both information about fermenting and then distilling. also includes plans for reflux stills and gets into some theory of operation. includes useful calculation tools to predict fermentation outcomes and various things like that. this is probably the most complete guide to distilling that i've seen on the web

[Jumala]

Mega tryes to win the nobel price. lol

I believe this problem is an older one. I´m certain that many scientists do research for a proceed to convert cellulose in a single sugar or more convenient direkt into a kind of fuel.
The two possibilities are:
A method to do the job already exist,-

then it must be too inefficient otherwise it would be in use everywhere. (To make biodiesel from rapeseed must be efficient because it is a little cheaper than
normal diesel in germany)

The method don´t exist,-

then there are to much technical or biological/chemical problems.

In both cases , who will find the perfect method get the nobel price and will be rich from selling patent licences.
(Only when the large oilcompanies don´t kill him)

And for everyone who want´s to make a good fruit liquor or whiskey
this side and their links could be interesting.
<a href="http://www.turbo-yeast.com/intro.html" target="_blank">http://www.turbo-yeast.com/intro.html</a>

[10fingers]

Here are some patents related to this subject;
1. Pretreatment process for the conversion of cellulose to ethanol. Patent #6,090,595
2. Process for pretreating cellulosic substrates and for producing sugars therefrom. Patent #4,237,226
3. Method for increasing of cellulose in lignocellulosic materials, particularly hard woods, agricultural residues and the like. Patent #4,461,648
4. Prehydrolysis of lignocellulose. Patent #5,424,417
5. Method of treating biomass material. Patents #5,221,357 #5,366,558 #5,536,325 #5,628,830

[Jaxx]

Hey Mega, if yer after a yeast that can with stand high ethanol concentrations i think you can get it from liquor home brew kits. I have seen these kits in the UK and they claim to have a final alcohol percentage by volume of 20 or 21 % alc.

Good luck with this ambitious project of yours!

[kingspaz]

i think that yeast converts simple sugars like glucose, fructose and sucrose or even starch to alcohol. the problem is getting a yeats that can process cellulose which has lots of cross linking between lengths of glucose chains.

[megalomania]

I have found a few places that sell distillers turbo yeasts, but I am still looking for some speciality yeasts. After an initial hemicellulose hydrolysis you end up with mostly pentose sugars. I was dissapointed to find out that regular yeasts either have a hard time or simply can not use pentose sugars.

I keep finding research on special strains of yeasts and other microbes, but nobody seems to have them for sale. I may have to do it the old 1980's way and write letters to the various government agencies asking for sources.

[organikum]

mega you might have a look at this page:
<a href="http://www.dsmz.de" target="_blank">http://www.dsmz.de</a>

They sell also to individuals if you ask the right way.
Hope it is not to late to get your boyscoutgroup´s project running.
ORG