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Trying to make ethanol out of grass, what chemicals could I use to break down the grass into simpler sugars? Answered

Grass is made up of starchy carbohydrates which I think would not be converted to ethanol by yeast. What could I use to break down the starch into simpler sugars?



8 years ago

Do you actually need ethanol? You might be able to make methanol.


8 years ago

+1 and an AWFUL lot of research is going into that very question.

Jack A Lopez

8 years ago

Potatoes are starchy, but not grass. Grass is cellulose-y, as Lemonie has already mentioned.

Nonetheless, whatever your starting material,  it may just be a matter of finding the right enzyme.

An enzyme is a kind of catalyst made by some living thing. The enzyme itself is not alive, but some living thing (plant, animal, bacteria, fungus, etc) produced it.

The names of enzymes typically end in the suffix "-ase", and the prefix is the thing that enzyme breaks down. For example: Urease breaks down urea. Cellulase breaks down cellulose. Twinkie-ase breaks down twinkies. And so forth.

You can buy enzymes from certain chemical suppliers, and then you mix some amount of this enzyme together with the stuff you want to break down in a big vat, usually mixed with water, at the temperature and pH at which that enzyme works best.

Please note that I've never tried this, but I have read about it.   Supposedly it will work... if you can get past the dreaded "lignin", and also the ROUSes,  but I'm pretty sure they're just a legend.

I was searching for some good links to explain this stuff, and most of them seem to coming from here:


More specifically:


From Chapter 5, of the Mother Earth ethanol manual:


Preparation: Chop straw or soft material. Wood must be fine sawdust or treated with 400 deg F steam for 2 hrs.

Additives (Enzymes): Add a 1% caustic solution; hold at 140 deg F for 3 hrs. to separate lignin.

Preboil: Draw off lignin, neutralize.

Cook: Cook at 140 deg F for 4 hrs. in 1% solution of Biocellulase**.

Cool Down: Remove sugar liquid.

Culture: Reduce temp. to 90 deg F; add brewer's yeast; agitate for 10 min.; cover.

Comments: Results: 2.5% alcohol. Acid hydrolysis is an alternative but expensive method.

Ah! I forgot about the legendary acid hydrolysis method!  Maybe they explain what that is here:


8 years ago

No, grass is made up of cellulosey carbohydrates.

That is the problem.