Discussion in 'General Science & Technology' started by Carcano, Aug 23, 2008.
no apology needed
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I did not have enough time to check what they are doing in detail (and I assume the most interesting bits will be propriety anyway. However, one of the approaches of creating fuel does not depend on the depend on ethanolic fermentation, but the use of microorganisms, often bacteria, or mostly unicellular algae (though sometimes cyanobacteria are also erroneously counted as algae), which are often engineered to boost the yield of certain short-chain fatty acids, which are extractable as biodiesel. By combining this with microorganisms which secrete cellulases (polysaccharides cannot be easily taken up by the cell, they have to be cleaved outside of the cell), the algae in question can use cellulose as a carbon source. I do not know precisely what kind of organisms they use, though.
In general, enzymes are (over)produced by engineered microorganisms, in this particular case it is possible that they do not purify the enzyme but simply add the organisms in question to the mix. The reason being that (aside from being cheaper) usually the plants added to the fermenter (same goes for biogas systems) are normally not sterilized and just by adding desirable organisms in excess the chances of other organisms proliferating can be reduced.
In either the production of cellulosic etoh or oil we need to use enzymatic break down of the complex polysaccharides. (Here ignoring non-bilogical destructive distillation route). BioOil as product has the advantage of separation from water by gravity and going thru existing pipelines and no thermal input but Etoh of works in large stock of existing IC motors, which are lighter* weight than diesel motors due to their high compresion ratio ignition. Sugar cane provides ONE simple sugar by simple crushing and has MORE than the thermal requirements for distilation heat in the crushed cane. (This excess is currently burned to generate ~5% of Brazil's electricity, but could be the cellulose used for more Etoh or oil.)
Fermentation for Etoh takes time (and time is money) also the alcohol produced is toxic to the yeast making it (limits Etoh concentration to about 15% I think.) If a combined mix of enzyme making "microorganism" and algae making oil were made, would there not be some similar toxic limit for one or both these life forms? Also gravity separation of the oil may not be cosistent with the O2 requirements of the "microorganism." Or do you think that the oil would float to top and could be removed well below the toxic / O2 limits?
How fast (compared to fermatation yeast) is the oil production by Algae? What do you guess is the rate limiting step? (Making oil inside the algae cells, getting it out thru cell walls, separating from "thin" algea cells and harvesting the "fat filled" cells (if that is done), the production of the enzyme or the enzymic cleaving ot the Cellulose? etc.)
Can you comment on some of this - even your "guesses."
I think it is going to be hard to beat tropical sugar cane alcohol in the economics as the enzymes are expensive and do not yield only one type of "simple" sugar. My investment in it is an order of magnitude greater in cane alcohol than in the enzyme making companies, but they will be need either way the cleulose is used (for oil or some simple alcohol). I have not bet any thing on the destructive distilation route as that is very old and many who know more than I think the enzyme route can be improved to make fuel more economically, especailly with algae that does not directly need sunlight but uses a feed stock that did. None the less, quite a few are investing in destructive distillation plants for Etoh production. (I think and hope they are "BACKING THE WRONG HORSE.")
Am I missing some thing here? Am I asking all the important questions, or at least thinking about them? Which way do you think will we make car's bio fuel in large volumes?
*Low IC motor weight is very important for fuel efficiency as car becomes almost 10 pounds lighter for every pound removed from motor. - Why Al alloy blocks, with steel sleeve inserts for piston chambers, are sometimes used. The tank for methane storage with range of alcohol is neither small nor light. IMHO, methane will only be for vehicles that stay in the city, like cabs and light delivery trucks.
thats all good
but i thought that the thread was whether methane could be made from cane juice with less energy input and more energy output.
It is, but "Less & More than what?" is the important question. Bio fuel is a wide open horse race at present, with at least half a dozen very different horses in the race now.
Do you mean something in the line of: "If I add x mol sugar how much methane/fatty acid/ethanol" can I get respectively?
Yes that is a good question and also how long to make a fixed combustion energy in a 10,000 liter vat making it (fermentation vs "no light" algae, especially, but as this is a methane* thread it too)? After it is made, how long and how much energy to get it into barrels?
As a physicist, who know H2O is highly polar molecule and Etoh is not, why is their not some permable material with fine electric grid on both sides that can "pump the water out" instead of distill the Etoh out of the water?
* I can not get very excited about bio methane as doubt if it can compete economically with natural gas, which is at high pressure for the pipeling already in many cases. Also as stated in my post 63 footnote it is a "city use" only fuel for vehicles IMHO.
Hmmmpf. Efficiency of a fermenter with mixed biota (with at least one of the major contributors unknown). That is kind of a toughie.
I recall a paper using cyanobacteria to harvest biodiesel. Maybe the efficiency is listed there somewhere. I would have to dig through my folders and check whether I got some values somewhere, just to get some ideas. I guess with my schedules I would probably need a week or two to get back to you.
i think carcano had hinted to that in the first post
"Perhaps but only for one other "horse" in this race to find the economical winner.
From his OP link:
" ...There are about 1500 CNG refueling stations in the US, which is about the same number of commercial stations offering E85 ethanol blends. ..."
I woulds guess there are more than that in the state of Sao Paulo alone, perhaps just the city of Sao Paulo! Here it is call GNV (Gas Natural Vehicular)
Some car, mainly taxis, are "tri-flex" can use three different fuels. US has a long way to go but Brazil has been using Alcohol for more than thirty years.
Anybody who watches US television will have seen T. Boone Pickens very expensive commercials for his plan to solve the energy crisis.
Hes on a self-funded crusade (just like Al Gore) to replace the natural gas now used to generate electricity with wind power.
The natural gas will be re-directed for use in vehicles;
Hes convinced the numbers will work.
Trouble is...even if all domestic natural gas was used for vehicles there would only be enough for sixteen years, thereabouts.
The output is about the same for ethanol and methane.
The difference is the input of energy.
Can you expand on the "input energy" What is it and how much? In the out put "being the about same" do you consider ontly the energy in the fuel or the MPG it can make in the car designe for it? Specifically, are you considering the extra weight the methane tank and it effect on MPG, especially in a small light weight car (like US needs)?
Note that the frame, springs etc. make adding X pounds to the motor, fuel tank, or drive shaft ,etc. make at least 5X more pounds in total car weight.
Where does this come from? - I find it hard to believe. Many new "horizontal drilled" wells are going into old oil well and extending them radially to collecting natural gas. etc.
Also it would be hard to stop using Natural gas for electric power, with out great increase in the cost per kWhr. This is because gas trubine are cheap and can thus have low duty cycles (Sit idle 95% of the time) as they are only used for peak power loads. If you expand base load generation to be big enough to handle these peaks that expensive expansion will also be udees only 5% of the time, but the capital cost of it is 100% of the time. Alrady more than half of the cost of your electric power is the capital cost (not counting the distribution system as that is alredy sized for the peak loads.)
I do not know accurately the cost increase but guess the elimination of gas turbine peaking generation by larger base load type of generators would add at least 35% more to your electric bill.
I'm considering only the caloric value of the fuel energy output.
The input energy is how much energy is required for conversion from sugar to methane, or sugar to ethanol. The purpose of the thread is to invite comparison...meaning I dont have any reference to exact numbers.
I'm guessing however that conversion to ethanol requires far more energy on account of the heat required for distillation.
Now currently, there is only ONE production methane powered car and thats the Honda GX, which uses a lightweight composite tank...one third the weight vs. the aluminum tanks Ive seen in conversions.
due to current limited resources for natural gas in the united states. legislation has been in affect (for years like 20-30?) to limit natural gas use as an enegy source for electrity accept during peak hours. problem is with the decline in new coal powered plants the natural gas turbine generators have been running longer or all the time. this has been the major contributer to the increase of natural gas prices here in the us. in the us we do not currently have the natural gas wells to implement natural gas for use in transportaion as a solution. we very well may not have the natural gas period. so yes if we were to switch to natural gas use for tranportation i suspect that we would see a new crisis.
That greater energy input may be true, but the crushed cane stocks easily supply it. In fact, they also currently make 5% of Brazil's electric power. I.e. this extra heat energy has essentially negative cost as they sell the electric power.
In contrast the enery input for compressing the methane for injection into pipeline will consume electric power, and add to its cost. The real world is interested not the the energy efficiency but the profits. Also note that 99% the electric power for methane compression was made with heat. - I bet you did not consider that.
With counter flow heat exchangers the distallation heat can be very efficiently recovered to heat the input H2O/Etoh stream entering the still. This could recover almost all of it but is not done for economic reasons (The big heat exchangers required have capital cost.) There is not much possiblity of recovery of the heat that made the electric power for methane compression - Not the compression for pipeline, not the compression for filling car tank from a filling staion tank at lower pressure and it will be at least part of the time if not always. (Put a big high-pressure tank in your neighborhood, not mine, and I am even less happy to be driving behind that methane delivery truck on a hot summer day.)
SUMMARY: I bet in principle distillation could be the energetically more efficient than methane production. In fact, it may already be when you consider the heat that made the electric power for methane compression as small counter flow heat exchangers are normally used to warm the input H2O/Etoh stream entering the still, but this is motivated more to help condense of the alcohol vapor, I think, than for the recovery of thermal energy.
You may be correct. I do not follow the natural gas supply (but as they get it by drilling and I do follow that industry some) I still have my doubts. They were strengthen a few minutes ago when I read:
"When currency traders finally concluded a round of interest rate cuts was a greater probability, they took a fancy to the good old American dollar. Its value surged against the euro, British pound and Australian and Canadian dollars. Commodity prices also felt the impact and slumped in response to the exodus from hard assets.
In the melee, the price of natural gas futures slumped from $13.75 to $7.62 per British thermal unit between early July and late August. The price of the U.S. Natural Gas Fund (amex: UNG - news - people ), which reflects the price of natural gas, made a similar move, declining from an all-time high of $63.89 to $36.36 recently."
Such a great drop in price in so short a time hardly seems consistent with an impending shortage. Percentage wise that is much greater drop than oil -Fact that we are not finding any more cheap oil is why. I think we are still finding lots of gas with the new horizontal drilling in old fields I mentioned in prior post. Most oil wells just "flare it off" as worthless. All of Brazil's off shore wells do that. It would be easy and cheap (using it as the fuel for refrigeration and compression) to transfer it to an ocean tanker - it is shipped all over the world in cold tank ships. Flaring and that too would not be the case if it were in short supply.
The caloric value is equivalent to its energy output.
just to show some quick figures here is a link to the current issues in the us. http://sunhomedesign.wordpress.com/...nd-the-coming-chill-in-americas-living-rooms/ sure its a little more doom and gloom than necessary. but in reality the us ng is basically tapped and done.
and the stock market doesn't necessarily show current demand. though it is a good source for reality, my thoughts are "put your money where your mouth is". costs are a good indicator as to what the worlds population feels. we have seen trends in the market that do not reflect what actually exists. buy low sell high. i think what is being experienced is a return to reality. the same applies to oil. in reality we have no shortage as of yet. soon people will start selling their oil futures (cashing out) and the price will drop to a more realistic cost.
Not quite, depending on how complex you want to go. It depends on the one hand on the community in the fermenter (because not all carbohydrates will be used for ethanol, lipid, or methane production, respectively), the pathways used for methanogenesis (e.g. whether it starts with CO2, acetate, or maybe another intermediate possibly generated in the fermenter) and so on. Ethanol and lipid production can often be done with a pure strain, however methane production is usually conducted with communities. Recently a few publications came out with metagenome analyses of such communities found in methane plants.
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