Fermenting lawn grass

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FuelMaker
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Fermenting lawn grass

Post by FuelMaker »

I thought I'd break this out into the proper area.

I want to try fermenting lawn grass, it's an unlimited source, sounds fun to try, and it might actually make a difference to the world if a simple farm-scale fuel ethanol production can be worked out that doesn't rely on buying expensive enzymes - and I think I've got it worked out but I'd like to run the protocol by the fermenting experts here:

Background; all grasses (including lawn grass) contain a higher than usual cellulose/hemicellulose to lignin ratio. The cellulose and hemicellulose is wrapped up in lignin where it's almost impossible for enzymes to get at it. Cellulose/hemicellulose is made of long chains of glucose units with a few other things in with it.

The biggest problem is to break up the lignin so the cellulose can be saccharified by enzymes. This step is called pretreatment. Potassium hydroxide (wood ash lye) generates much less yeast inhibitors that sodium hydroxide or sulfuric acid pretreatments and works better than calcium hydroxide (slaked lime) in addition it can be done at room temperature and so saves considerable amounts of energy.

The enzyme that break down cellulose/hemicellulose is called cellulase, its actually 3 different enzymes with slightly different optimum temp/PH ranges but close enough that the ranges can be averaged out. You can buy commercial cellulase but it's not cheap, and defeats the whole "independent farm-scale" fuel ethanol production idea.

However a fungus called Aspergillus Niger produces large quantities of it. It's a relative of the Aspergillus Oryzae that sake makers use make koji to saccharify rice and can be "farmed" in the same way aerobically on a moist tray in an incubator, this is called solid state fermentation (SSF). An incubator can be easily made using a fridge, a heat source like a reptile ceramic lightbulb and temperature controller.
Neither A Niger or A Oryzae reproduce in a submerged medium, large spore counts have to be built up first via SSF before a liquid mash can be inoculated.


The protocol:

1. Boil the grass to soften and sterilize it
2. Run the grass slurry through a 3 stage garbage disposer to chop the grass VERY finely. Luckily garbage disposers act like pumps so the discharge can go right back in the tank. I can use the dishwasher intake to flush the disposer with distilled water to clear it out prior to disconnecting.
3. Pretreat it with .5% w/v potassium hydroxide (pH 8.95) at 21C for 12 hours to break out the cellulose and hemicellulose from the lignin
4. Normalize the PH to 6 with citric acid & add urea or DAP as a nitrogen source.
5. Inoculate it with aspergillus niger spores to produce cellulase and begin breaking down the hemicellulose and cellulose into fermentables
6. Ferment for 3 days at 30C while aerating and stirring the mash @ roughly 60rpm.
7. After 3 days raise the temp to 46C into the optimum cellulase activity range (which may kill the A niger) for 12-36 hours (depends on medium, will have to find out)
8. Ferment it with yeast.
9. Distill as normal.

Problems that I can see

- Sterility when the grass is liquefied in the garbage disposer. Possible fix is to run it through the disposer before boiling. I'll have to find out.
- Exterior sourcing of urea or DAP, defeats "independent farm-scale" idea. Use urine? I'll have to find out.
- Exterior source of citric acid. Possible solution is A niger is used commercially to make citric acid, need to find out if it can be adapted to farm scale production.
- Exterior source of potassium hydroxide, possible solution is wood ash lye can be easily made on the farm from hardwood ashes.
- About 20% of the A Niger output is going to be xylose, yeast can't ferment xylose. The only place I can find genetically modified xylose fermenting yeast is at the ATCC, and they want $300 for a sample. Other yeasts can ferment xylose but they have very poor ethanol and inhibitor tolerance.
- No idea how to tell if A Niger has processed all the cellulose other than maybe specific gravity or brix meter? I suspect brix meter will not be accurate because of all the other dissolved solids in the mash. Don't know of an equivalent of a "iodine test" for cellulose.

Variations for best output

Some papers suggest that co-fermentations of yeast and A niger provide as good or better results than starting out with the A niger, raising the temps to optimum cellulase range and then pitching the yeast after 3 days. Still lots of variables with the aeration duration, A niger and yeast pitching rates, and time. I'll have to try them all and see what the results are.
Further research suggests that A niger can stably grow in conditions up to a pH of 11 and will rapidly acidify the mash on its own with citric, gluconic & oxalic acids. PH readjustment may not be necessary, I'll have to find out.

Equipment

A home made 55 gallon stainless temperature controlled aerated stirred tank bioreactor aka fermenter. Maybe combine the fermenter with the distilling pot into one vessel for simplicity and just change out the lid? Many pros and cons either way.

Standard four inch 48" tall VM column w/ SPP packing. Evaluate lava rock as packing for farm scale use?

So anybody see any other problems with any of it?

I can't claim credit for any of the above ideas, I've gathered them from several scientific papers I've read on optimizing A niger growth, cellulase production, cellulose pretreatments, & fuel ethanol production and kind of just glommed it all together and gave some thought on how to accomplish it.

The best single source document is this thesis: http://uknowledge.uky.edu/bae_etds/28/ he also refers to many of the papers I've read. Warning, its 140 pages and 2.6MB. It's a slog through the data presented but damn good reading.

Edit: Spelling
Edit: Added pH data
Last edited by FuelMaker on Wed Nov 18, 2015 9:57 am, edited 3 times in total.
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bearriver
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Re: Fermenting lawn grass

Post by bearriver »

Good luck with the project. If you get it working, it might be fun to perform demonstrations for students in your local school science class.

I do know that phosphoric acid is cheaper and more effective than citric acid if it is only being used as a pH buffer. It might save you a few bucks in operational cost... :idea: If it works in your application that is... :shifty:

Do you have a 55 gallon stainless tank already?
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Re: Fermenting lawn grass

Post by FuelMaker »

bearriver wrote:Good luck with the project. If you get it working, it might be fun to perform demonstrations for students in your local school science class.
I do know that phosphoric acid is cheaper and more effective than citric acid if it is only being used as a pH buffer. It might save you a few bucks in operational cost... :idea: If it works in your application that is... :shifty:
Do you have a 55 gallon stainless tank already?
Thanks, don't have a tank yet, I'm about to pull the trigger on a $200 one on ebay but I keep changing my mind between adapting a stainless drum or going with a polypropylene cone bottom tank (if I can find one that doesn't break the bank). The poly pro has the additional problem of I need to boil the grass slurry and I'm not sure how I could do that with only natural gas available to me. A heat pipe maybe? They're really tricky to build. But I'd sure like a cone bottom tank.....
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bearriver
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Re: Fermenting lawn grass

Post by bearriver »

How's this? It fully drains and the walls are rolled from stainless plate. 55 gallons, 2 inch npt drain, motor mount. There is a couple hundred pounds of stainless steel there. It does need a lid however...

PM me an offer if you are interested in it. It's turning into one of those projects that I'm never going to get done, and I'd like to see it go. It can be sitting on your doorstep tomorrow.
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FuelMaker
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Re: Fermenting lawn grass

Post by FuelMaker »

bearriver wrote:How's this? It fully drains and the walls are rolled from stainless plate. 55 gallons, 2 inch npt drain, motor mount. There is a couple hundred pounds of stainless steel there. It does need a lid however...

PM me an offer if you are interested in it. It's turning into one of those projects that I'm never going to get done, and I'd like to see it go. It can be sitting on your doorstep tomorrow.
That's beautiful, it'd be perfect. Thanks! PM on the way.


Edit, holy crap, that's a beast of a tank at a couple hundred pounds, a normal SS heavy duty closed head drum is 65lbs, and that's with 1.5mm sides and bottoms (I think)
Its making me get teary-eyed just looking at it... (sniff) :-)
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FuelMaker
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Re: Fermenting lawn grass

Post by FuelMaker »

Well, with 179 views and no dissenting opinions, I'm going to proceed with the build with the above assumptions. I'll be going with having the still and fermenter being two separate vessels.

Too many things going on in a fermenter: Stirrer, heating element, cooling coil, product sample out, airlock, etc to also have a still attached to it. I drew it out to scale and it'll all fit, but is pretty crowded and would be a rat bastard to clean.

Chemtainer's got a cone bottom polypropylene open top tank that'd be an awesome fermenter and won't break the bank too bad, and the polypro routine service temp is rated up to 212F so I can boil the mash in it too. I'll be using atmospheric pressure superheated steam direct injection from a monotube boiler as the heating source.
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Re: Fermenting lawn grass

Post by FullySilenced »

Seems like i read an article from Sweden or Norway about them doing that... along with the leaves and tops from tree harvesting...

do some reading on the net... but it makes wood alcohol... lots of methonal don't ever drink anything made in the still after you make some of this kinda product...

I will also ask why your not on one of the fuel forums instead of a hobby forum... cause we really don't do this kind of thing here... :roll:
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Re: Fermenting lawn grass

Post by FuelMaker »

FullySilenced wrote:Seems like i read an article from Sweden or Norway about them doing that... along with the leaves and tops from tree harvesting...

do some reading on the net... but it makes wood alcohol... lots of methonal don't ever drink anything made in the still after you make some of this kinda product...

I will also ask why your not on one of the fuel forums instead of a hobby forum... cause we really don't do this kind of thing here... :roll:
Nope it definitely makes ethanol. (see the linked paper) You might be thinking of wood gasification which does make methanol via pyrolysis, completely different.

And this is a hobby, and I'm in the "Alcohol as Fuel" section and there really aren't any hobby fuel ethanol forums. 99.8% are all about starting up big plants and the fuel forums that do exist nobody talks much on them, I've been lurking there too. I'm just a basement experimenter puttering away...

That'll also probably make potables too now and again.
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Re: Fermenting lawn grass

Post by ShineonCrazyDiamond »

FuelMaker wrote:
FullySilenced wrote:Seems like i read an article from Sweden or Norway about them doing that... along with the leaves and tops from tree harvesting...

do some reading on the net... but it makes wood alcohol... lots of methonal don't ever drink anything made in the still after you make some of this kinda product...

I will also ask why your not on one of the fuel forums instead of a hobby forum... cause we really don't do this kind of thing here... :roll:
Nope it definitely makes ethanol. (see the linked paper) You might be thinking of wood gasification which does make methanol via pyrolysis, completely different.

And this is a hobby, and I'm in the "Alcohol as Fuel" section and there really aren't any hobby fuel ethanol forums. 99.8% are all about starting up big plants and the fuel forums that do exist nobody talks much on them, I've been lurking there too. I'm just a basement experimenter puttering away...

That'll also probably make potables too now and again.
Fuel maker, you are more than welcomed here. If anything, you are providing us with information as well.
Also, I know how it reads, but I don't think FS meant anything by it. Probably was trying to help you.

Our maybe he was just frustrated because he couldn't incorporate nuking fuel into your process. :ebiggrin:
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You reached for the secret too soon, you cried for the moon.
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Re: Fermenting lawn grass

Post by Texas_Brew »

So how did it turn out? Any successful fermentation yet? I like the idea of running small engines on ethanol I just think that retrofitting the carburetors might be more difficult than the production. But if you pull it off. You will be legal so long as you get the permit for home distillation for fuel purposes.
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Re: Fermenting lawn grass

Post by bilgriss »

Another interested party here....
cob
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Re: Fermenting lawn grass

Post by cob »

it looks like the first corn waste plant started up in iowa in 2014.

search....Cellulosic ethanol....

PNNL has been trying to develop an enzyme to copy the

enzyme that termites use to break down cellulose into a digestible form.
be water my friend
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