12AX7
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Energy research chemistry
An experiment I've been contemplating (but won't have time for before college this year) is cellulosic ethanol. The general idea is to hydrolyze
cellulose, poly-(beta)-glucose, into sugars (glucose and other short bits) that yeast can ferment. This can be done with cellulase, which is
expensive, or acid, which is cheap.
I was considering:
- Take a bucket full of grass clippings (or sawdust, but grass clippings have an ironic appeal, see below),
- Chop it up real fine if possible,
- Digest in boiling 1% sulfuric acid (pH ~ 1) until hydrolyzed (hours/days/weeks?); one goal: find time*temp required for conversion,
- Neutralize acid in some reasonable manner, adjusting pH suitable for yeast,
- Ferment, yielding a maybe ~10% EtOH mash,
- Use a combination of distillation, and dehydration if necessary, to obtain 95% ethanol (pot still is cheap but slow to reach 95%, so I'd probably
use some dessicant),
- Blend purified ethanol with gasoline and add to lawnmower to cut more grass.
Whatever's leftover from the process (if any) goes on the shelf as net profit.
The overall goal of this project is, can one mow grass with a grass-powered mower, and is a net energy gain possible?
To be completely fair, it takes a lot of heat to boil the acid and distill the mash, so grass-fired boilers should be used for the process.
(Alternately, renewable energy sources such as solar or geothermal could be used, but that's probably a little impractical, being whole "energy
research" projects in themselves. They are options for industrial production.)
The nice thing about an experiment like this is, one could concievably do it simply as a hobby, but unlike many hobbies, it also serves a purpose,
investigating, on a small scale, what industry is up to today.
Tim
Tim
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watson.fawkes
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Consider using a solar collector to raise the temperature of the hydrolysis stage. A parabolic trough collector allows easy transfer via slurry.
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Magpie
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Also could obviously use solar drying of the grass.
Your project reminded me of an alcohol plant that was built at Port Hadlock, WA and operated during 1911-13. I quote from a brochure provided by the
Old Alcohol Plant Resort:
"Based on the works of Louis Pasteur, The Classen Chemical Company processed alcohol from sawdust using a French distilling process known as the
Bergius Process. The process began with wood waste which was shredded into chips then dryed in a steam dryer until it contained no more than 1%
moisture. The dried wood was mixed with cold 40% hydrochloric acid. The cellulose was converted to glucose (This conversion was known as
saccarification). At this point a byproduct known as lignin was extracted. A mixture of glucose and acid was moved to an evaporator, where the acid
was recovered and reused..........
The sugar rich solution was then introduced into fermentation tanks. Special yeast was grown and incubated by a biologist........... The sugar/wood
in the fermenting tanks, known as wort, was innoculated with the yeast strains, producing a beer of 8% alcohol. When the beer was ready, it was moved
from the beer well into the distillation process. The distillation yielded fusel oils, 190 proof (95%) industrial ethyl alcohol and spent wort for
cattle feed."
The plant only ran two years because of severe competition, including the Hawaiian molasses producers.
I thought this interesting piece of history might be useful as well as entertaining. There is a resort hotel on the site now, reusing much of the
plant buildings.
[Edited on 1-9-2008 by Magpie]
[Edited on 1-9-2008 by Magpie]
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Twospoons
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Well, since one can power a goat entirely on grass, I guess there must be a reasonable amount of energy present 
If the objective is merely a grass-powered lawnmower, and the method is up for debate, why not a steam driven lawnmower heated by burning dried grass?
That cuts out a lot of processing.
Also you could have a grass fired stationary steam (turbine?) engine driving a generator to charge batteries for an electric mower. That would allow
you to optimise all parts of the cycle.
When I was 15 I tried anaerobic fermentation of grass to get methane. The yield was poor, and the resulting muck had a pong you wouldn't believe.
[Edited on 2-9-2008 by Twospoons]
[Edited on 2-9-2008 by Twospoons]
Helicopter: "helico" -> spiral, "pter" -> with wings
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not_important
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| Quote: | Originally posted by Twospoons
...
When I was 15 I tried anaerobic fermentation of grass to get methane. The yield was poor, and the resulting muck had a pong you wouldn't believe.
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Methanogenic fermentation is difficult to do on a small scale with any sort of efficiency. The acid forming and the methane forming bacteria do
better if they are in separate tanks as they prefer different conditions including temperature; on a small scale it is difficult to maintain the
proper temperatures without heaters. The amount of air trapped in the feedstock and fermentation vessel also reduces yield, unless the feed was first
finely ground.
The small scale units often produce ammonia and amines from the proteins and other nitrogen containing organics, and reduce some sulfate to sulfide.
In large scale units this is easier to avoid.
Separating the CH4, CO2, H2, N2, and short chain fatty acids is also difficult, large scale production may use pressurised water or selective
permeability membranes to accomplish this.
A good anaerobic fermentation will reduce the BOD by 95%, with most of the feedstock carbon ending up in the CH4 and CO2, and almost all the rest in
cell mass.
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kclo4
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If the grass were dried, it could be turned into a powder much more easily.
Boiling a large can of grass and dilute acid I'd bet would take a long time to get a decent amount to hydrolyze. If time really isn't a big deal, I'd
imagine one could set it in a black garbage can in the sun for several weeks in the summer.
Also the waist could be used as a fertilizer. The sulfates of whatever it was neutralized with could be good for some plants, as well as all the other
material left in it.
How about Burning some of the grass to heat the acid/grass mix (haha) and using the ash to neutralize the acid to allow the yeast to turn the sugars
into alcohols.
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crazyboy
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For larger scale I believe other crops like switch grass are better suited because they take no water suck CO2 and make lots of energy.
I first two problems 1. finding a suitable base that won't kill yeast 2. economic boiling of grass for long periods of time.
Good luck!
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Panache
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Doesn't methanol get formed in the airless pyrolsis of dry timberr at 450C or something. Methanol for many years was referred to as 'wood alcohol'
because they got it from wood. so you minimise your chemical use (ie no acid) however you need 450C and a nitrogen flush.
Wait if you linked one of each process you could use the CO2 from the fermentation as your sheilding gas.
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Rosco Bodine
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| Quote: | Originally posted by Twospoons
Well, since one can power a goat entirely on grass, I guess there must be a reasonable amount of energy present
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The solution is now clear A team of goats pulling a reel type mower like a
dogsled . The machine operator
walks behind, shouting "Mush !!" while endeavoring to
step over any "goat mush" which may also be discharged
during normal operation Two, four, or six "goatpower"
models are easily envisioned  You could wear a
Santa suit and try to think of them as reindeer
As a side enterprise , maybe build lightweight carbon composite rickshas which can be pulled by goats also,
when they are not occupied with mowing, sort of an
Amish "sport model" , more maneuverable and
grass efficient.
[Edited on 2-9-2008 by Rosco Bodine]
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not_important
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I believe the methanol mostly comes from Me-O-aromatic groups in the lignins, meaning you'll need woody materials.
You can combine acid hydrolysis with pyrolysis of the high lignin waste from that,. Boiling is not needed, and higher temperatures tend to produce
condensation products from both the cellulose and lignin so most processes avoid heating (think 30 to 50 C). Percolation is used to remove the sugars
before much of them have a chance to further react; there is some work on using permeable membranes to separate the acidic solution from the sugars to
make this more economic.
Heating is used in the pretreatment of the biomass. Steam explosion is one such method, biomass is treated with high pressure steam to heat it to 250
C for a few seconds, then the pressure is released to convert the plant matter into a porous shredded form for the hydrolysis step.
There are dozens of books and thousands of papers on this topic, much moneyhas been spent over the last century to increase yields of sugars and
useful byproducts from such processes.
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blogfast25
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Tim:
It's certainly an interesting project that should keep you going for a few weeks - lol.
My guess is that you won't reach self-sufficiency: not enough "sugary stuff" in grass, I think.
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ScienceSquirrel
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Have you considered growing sugar beet instead?
The beet could be thinly sliced and extracted with water to form a very sugar rich wort.
There are special Turbo yeasts that will ferment out very strong liquors ( up to ca 20% ABV ) and this would make your distillation step quite
efficient.
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12AX7
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| Quote: | Originally posted by Twospoons
Well, since one can power a goat entirely on grass, I guess there must be a reasonable amount of energy present
If the objective is merely a grass-powered lawnmower, and the method is up for debate, why not a steam driven lawnmower heated by burning dried grass?
That cuts out a lot of processing. |
The goal is to interface with existing infrastructure, so it has to be a gas lawnmower. The medium can be ethanol, butanol or whatever, but ethanol I
think is the simplest to do right away.
| Quote: | Originally posted by kclo4
If the grass were dried, it could be turned into a powder much more easily. |
Indeed. Dry grass is also needed for the boiler. If you have the area (and little enough rain!), solar heating is just fine for drying and heating
the hydrolysis. I can just imagine, like, a greenhouse with a couple of black garbage cans inside stewing something most unpleasant.
| Quote: | | Boiling a large can of grass and dilute acid I'd bet would take a long time to get a decent amount to hydrolyze. If time really isn't a big deal, I'd
imagine one could set it in a black garbage can in the sun for several weeks in the summer. |
If it takes a lot of time, that could be an issue. If you need to mow every two weeks (that's been pretty well true around here, up until the dry
season), then you need to dry and process that at the same rate.
| Quote: | | Also the waist could be used as a fertilizer. The sulfates of whatever it was neutralized with could be good for some plants, as well as all the other
material left in it. |
Indeed. Without a goat in the process, there's no need to feed it with the wastes (like how used brewer's grain goes to cow feed, usually). The lawn
will love it.
I was thinking ground up local dolomite, but:
| Quote: | | How about Burning some of the grass to heat the acid/grass mix (haha) and using the ash to neutralize the acid to allow the yeast to turn the sugars
into alcohols. |
Not a bad idea. Grass ash should be rich in stuff like potassium and magnesium carbonates, and it would be an excellent replacement for some (or all,
if enough is produced) of the dolomite.
| Quote: | Originally posted by crazyboy
For larger scale I believe other crops like switch grass are better suited because they take no water suck CO2 and make lots of energy.
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Agreed. On the home scale, the best resource is grass clippings (sadly, switchgrass doesn't look good in the lawn). For that matter, you could even
ask your neighbors for grass clippings and pool resources. Although distributing stuff like fertilizer after the process would be a little more
troublesome. Hey, combination mower/spreader? (And you'd get paid for mowing lawns, so it's already profitable.)
I guess the logical conclusion would be town- or city-scale collection (which could involve other cellulosic yard wastes, which are usually composted
these days I think), and the goal would be first to power your own fleet of riding lawnmowers, then whatever excess is produced you sell on the market
at spot price.
Tim
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chloric1
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And if you do this on a community scale you could accumulate enough byproduct that separation into chemical commodities becomes profitable? Is there
not an article somewhere from the 1920's where furan can be extract from corn husks? Fusel oil yields butanol and pentanol. I am sure acetals,
aldehydes, and ketone are prevelent also. So aside from economics it looks good but it could also reduce foreiegn oil dependence to some degree. Just
some points to consider.
Fellow molecular manipulator
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kclo4
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Urea to nuetralize?
Isn't it Furfural? http://en.wikipedia.org/wiki/Furfural
"Furan can be obtained from furfural by oxidation and decarboxylation of the resulting furan-2-carboxylic acid, the furfural being derived by
destructive distillation of corn cobs in the presence of sulfuric acid.[4]" - wikipedia.
Also I was wondering, since it needs to be neutralized would Urea work? Seems it would form Ammonium Sulfate after a while.
I wouldn't think Urea Sulfate would last to long in those conditions, but perhaps it would. This would be good because Urea is cheap, and it would
leave the resultant mixture a great fertilizer.
Keeping in mind it would already have all the micro nutrients and the macro nutrients as well.
There is potential to get all product and no waste from it I think. It doesn't seem like something worth perusing however.
You'd get Fuel, Chemicals, Fertilizer and also perhaps people could pay a small fee of having you pick up their green waste products?
I bet you'd be better off going to peoples houses that have messy fruit trees and gathering the already simple sugars in the fruit.
People with peach, apricot, apple, etc often cannot pick, gather or use all of them. So this leads to them falling off into their lawn and making a
mess. They would be more then happy to have someone gather them I bet.
Orchards probably get a lot of nasty fruits on the ground as well.
[Edited on 7-9-2008 by kclo4]
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12AX7
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Keep in mind the foodstuffs industry already has its waste going to places, like hog feed (cf. Dirty Jobs). Although I dont know that it's all going
there.
Tim
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