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Alcohol From Sawdust...

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  • BOKAKOB
    Fuel From Sawdust by Mike Brown (submitted by Keith Addison (From Acres, USA, 19 June 1983) The conversion of cellulose, such as
    Message 1 of 1 , Jul 30, 2003
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      Fuel From Sawdust
      by Mike Brown (submitted by Keith Addison <keith@...>
      (From Acres, USA, 19 June 1983)

      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



      I can be wrong I must say
      Cheers, Alex...
      A


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