Ethanol production
Ethanol production
(OP)
The press speaks of agricultural methanol as a solution for our energy dependence. What is the yield in terms of volume of ethanol per bushel of corn? What energy is required to process corn to ethanol? What is the likelyhood that ethanol from corn could replace significant portions of the crude oil based refining or petrochemical industry?





RE: Ethanol production
This subject has been studied and debated ad-nauseum. I did in-depth studies on ethanol production over 25 years ago and the outcomes were always bad for the viability or feasibility of ever producing a competitive energy source from ethanol. In order to compete the energy source has to be devoid of governmental subsidies and stand on its own economic merits.
To address your specific questions:
1. It doesn’t matter what the “yield” of ethanol is per bushel of corn. What matters is the rock bottom real price of the product alcohol – all-costs-in and including a reasonable profit for the producer. The obvious fact is that it doesn’t generate a profit, but rather it generates a net loss. Proof of this is that neither you nor I would invest in such a venture – unless, of course, we’re paid by the government with other tax payers money. This latter effect is what drives companies like Archer-Daniels and others to continue to make ethanol. They simply use our taxes to justify their production.
2. It takes more total energy to produce the fuel-competitive ethanol than the energy it contains. If you have ever gotten remotely close to the Waste Agricultural industries, you will soon realize what the term “intensive labor requirement” means – and costs. It takes hydrocarbon energy to make the fertilizer, plant the corn seeds, run the tractors, harvest the cobs, transport the grain to the fermenters, etc., etc., …….
3. I wouldn’t waste my time waiting for ethanol to “replace significant portions of the crude oil based refining or petrochemical industry”. I’ve got a lot of better and more interesting things to do – like watching all the windmills chugging along, trying to supply electricity to all the cities in the U.S.. As an Electrical Engineer, you should be in a good position to identify just how long that will take.
The next time you read a press release on the subject, just bear in mind who wrote the article and their credentials as well as experience in the engineering realities. Most of these people spent their high school days sleeping through chemistry and physics classes.
RE: Ethanol production
The American Coalition for Ethanol (ACE) claims that
"It takes only 35,000 BTUs of energy to produce ethanol that contains at least 77,000 BTUs of energy."
The latest production processes are claimed to be more energy efficient than reported in a well-known 1979 study by Professor David Pimentel of Cornell.
http://www.ethanol.org/PressRelease71905bhtm.htm
But, land & labor costs perhaps make ethanol non-competitive in the US w/o the subsidies mentioned by Art. The jury is still out IMHO.
Using waste cellulose or switchgrass will improve the economics, but a lot of technological development is needed, http://www
RE: Ethanol production
Unlike the organization you cite (ACE), I have no corn to sell nor subsidies to receive. My opinion is based on my own factual experience and studies as an energy consultant and I have no interest group that I work for or under. Besides the energy sector, I've also worked directly in the agricultural waste product industry here in the USA. My personal experience has proven to me and to everyone associated with this industry that the labor market in the USA makes collecting any substance off a farm a very costly and prohibitive labor item.
I also know more than a few things about Brazil since I've lived and worked there. I have first-hand knowledge that Brazilian alcohol is subsidized by the Brazilian government. That is the reason it exists. Otherwise, it couldn't justify its existance. What you call "cheap" turns out to be very expensive - all one has to do is review the economic status of Brazil today. It's national economy is teetering on bankruptcy. I also have difficulty trying to figure out how you can cite that the fuel in Brazil is also "cheap".
I realize that the facts I cite are not pleasing to those of us who are hoping for the energy miracle that will save us from total depletion of fossil fuels and further atmospheric contamination. However, like any other engineer who has gone through many years preaching the truth to energy consumers I'm afraid that there is no credible technology waiting "in the wings" for us to employ. Hydrogen economy, solar energy, aeolic energy, geothermal, fuel cells, natual gas substitution, Gasahol, etc., etc., have all been looked at and they simply don't offer a total solution for the future. After 30 years since the Oil Embargo of the early 1970's we're still no closer to finding an answer to the energy replacement(s) for fossil fuels. All we've done is deplete our biggest and proven option: Nuclear Energy - something the environmental nuts should be very proud of. I predict the tree-huggers will all line up for Nuclear as soon as gasoline prices hit the $3.00/gallon level and their electric bills start to go up to the roof - which won't take long at the rate we'e going.
In the meantime, the most practical and profitable use for Ethanol from sugar cane is still Rum.
RE: Ethanol production
Capital equipment investment for an ethanol plant must also be added to costs already mentioned.
I've never been to Brazil; perhaps they're on an ecologically disastrous route exploiting lands for a short-term gain. For cheap fuel, I meant the burning of bagasse. It seems they export ethanol profitably. Is it only because petroleum is currently so expensive? Or, because the US mandates it as a gasoline additive?
RE: Ethanol production
sugar cane was introduced in Brazil in the XVI century. The production increased since then, but I cannot figure out what you mean by ecologically disastrous route. Do you think they are using Amazony for sugar cane production?
Montemayor
I cannot see where Brazilian economy is teetering on bankruptcy. And even if it were true what one thing has to do with the other?
The original ethanol program was in fact heavily subsidized. That was during militar government 30 years ago, as you probably know. But I have no information that the current phase of the program is based on such policy. Or at least such subsidies are only indirect (or hidden), associated only to the current obligation of adding 20% to 25% of ethanol to gasoline. The price/cost distortion associated to that is minor, however.
The main difference between original program (1975) and current situation is productivity: productivity increased from 2,204 to 5,500 liters of hydrous ethanol per hectare between 1975 and 1999. Today it reaches 6,000 liters/hectare
Naturally the viability of ethanol as option to petroleum depends on the oil costs. Current situation in Brazil shows a certain equilibrium in prices of gasoline and ethanol (energy basis). Some distortion in taxes does exist (gasoline has higher taxes in Brazil than ethanol). On the other hand Brazilian currency is overvaluated at least 20%, what makes oil cheaper.
fvincent
RE: Ethanol production
HAZOP at www.curryhydrocarbons.ca
RE: Ethanol production
Patzek shows that growing corn crops is environmentally disastrous because it takes fuel to grow corn and it is not sustainable because you will eventually destroy the soil by mining out the organic material. The amount of hydrocarbon fuel is fixed and the politically based decision to produce ethanol will accelerate the rate of depletion.
RE: Ethanol production
The following analysis supports Montemayor's comments on Brazil:
(ht
Kenvlach,
If the use of ethanol is such a good ideal, then why are there so few country's in the world trying to do it?
RE: Ethanol production
Regards
StoneCold
RE: Ethanol production
I don't think the analysis you mentioned does support Montemayor's comments on Brazil. Do you? What exactly?
As to your comments on why so few countries go after ethanol, I guess productivity is a key question. I cannot see much room for harvesting sugar cane in Europe, China or even USA (except some Southern states or Hawaii). As to Thailand, Australia, India and Brazil...
The analysis of Patzek is very interesting, however. But sugar cane ethanol would give very different figures, I guess.
fvincent
RE: Ethanol production
Montemayor's comments may have exaggerated Brazil problems, but the cia study does show that there are problems there:
"Brazil's foreign debt (a mix of private and public debt) is large in relation to Brazil's small (but growing) export base."
Characterized by large and well-developed agricultural, mining, manufacturing, and service sectors, Brazil's economy outweighs that of all other South American countries and is expanding its presence in world markets. From 2001-03 real wages fell and Brazil's economy grew, on average, only 2.2% per year, as the country absorbed a series of domestic and international economic shocks. That Brazil absorbed these shocks without financial collapse is a tribute to the resiliency of the Brazilian economy and the economic program put in place by former President CARDOSO and strengthened by President LULA DA SILVA. In 2004, Brazil enjoyed more robust growth that yielded increases in employment and real wages. The three pillars of the economic program are a floating exchange rate, an inflation-targeting regime, and tight fiscal policy, all reinforced by a series of IMF programs. The currency depreciated sharply in 2001 and 2002, which contributed to a dramatic current account adjustment; in 2003 to 2005, Brazil ran record trade surpluses and recorded its first current account surpluses since 1992. Productivity gains - particularly in agriculture - also contributed to the surge in exports, and Brazil in 2005 surpassed the previous year's record export level. While economic management has been good, there remain important economic vulnerabilities. The most significant are debt-related: the government's largely domestic debt increased steadily from 1994 to 2003 - straining government finances - before falling as a percentage of GDP in 2005, while Brazil's foreign debt (a mix of private and public debt) is large in relation to Brazil's small (but growing) export base. Another challenge is maintaining economic growth over a period of time to generate employment and make the government debt burden more manageable.
RE: Ethanol production
Thanks. I have read the text too, following the link you mentioned. And yes, there are problems. No question about that.
Anyway, the question is still the same: what has government debt to do with the increasing production of ethanol? I cannot see the connection... The only menace to (sugar cane) ethanol is a cut down on the oil price.. In this case, the mills just switch to sugar production (as they are flexible) and the fuelflex cars use gasoline...
fabio vincent
www.figener.com.br
RE: Ethanol production
You are still mining nutrients from the soil. "Although sugar beets are grown in many areas of the U.S., they must be rotated with nonroot crops (1 beet crop per 4 year period is the general rule)."
http
You cannot store sugar crops like you do for corn:
"But sugar crops must be dealt with fairly quickly before their high sugar and water content causes spoilage. Because of the danger of such spoilage, the storage of sugar crops is not practical."
http://www.ienica.net/crops/sugarbeet.htm
And probably the biggest problem with sugar is that it is not economical to grow sugar crops in the US. So you would have to import the sugar as well.
RE: Ethanol production
fabio vincent
www.figener.com.br
RE: Ethanol production
I see your point now.
Patzek demonstrates in his study that growing crops is environmentally disastrous because it takes fuel to grow corn and it is not sustainable because you will eventually destroy the soil by mining out the organic material.
Patzek also states that the amount of hydrocarbon fuel is fixed and the politically based decision to produce ethanol will only accelerate the rate of depletion.
Montemayor is just saying that Brazil is already a debtor nation. Why would one desire to borrow additional money to subsidize a losing economical proposition?
It is the same issue as in the US. Your are benefitting the few who make up the sugar (or corn) lobby with government largess at the expense of everyone else through higher taxes.
RE: Ethanol production
RE: Ethanol production
Have you ever had the opportunity to check the energy balance of ethanol production derived from sugar cane? I guess you'd be surprised. The fact that corn derived ethanol is non-economical should not take you to conclude that all other sugar sources are not feasible. There is a wide gap between the two industries.
Sugar cane is 10-12% sugar. No starch. Just grinding and fermenting and concentrating...Ok, plus fertilizers, transport of the crops, goods and workers, equipment production, and so on...
The last numbers I have concerning the energy ratio for the production of sugar cane ethanor are: available energy divided by energy expenditure (all included: fertilizer, etc) equal to 8. That compares to 1.2 of corn ethanol.
Ok, according to Patzek the numbers are worse for corn, that is, only 0.9 (you lose energy when producing corn ethanol). Let's be conservative and apply the same reduction factor to the sugar cane. Instead of 8 we still have 7.2. More conservative? 6? 5? Still interesting, isn't it?
As to the debtor nature of the country, just take into account that a significant fraction of the new ethanol plants in Brazil are owned by European or American companies. No subsidies. Their risks...
fabio vincent
www.figener.com.br
RE: Ethanol production
Even when the stillage is worked up as fertilizer and the corn DDGS is sold as animal feed the economics do not come right.
The problem is that every farmers co-operative wants to get in on the deal, and they base their capital cost estimates on wildly optimistic and unrealistic views. They announce their plans to the press and there is a huge hullabaloo, and then after a few months it all goes quiet. A friend of mine, who has a business supplying columns and heat exchangers, told me he has stopped even quoting on the jobs because the farmers get upset when he tells them he cannot build columns out of old oil drums.
Ethanol's time will come, but at the present oil price it is not yet viable. The only people who can afford the ethanol are the drinkers! djack77494 is right on the money with the comment on nuclear power. It is already happening, but people just don't like to talk about it. When we have cheap electricity from the nuclear plants that we can turn into steam in electrode boilers, maybe we can make cheap ethanol.
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com
RE: Ethanol production
Codes for connecting to the Grid are still being developed by each state and should be completed by 2009. The best site for all information on renewable energy is the doe.gov. Just drill down from that site to where ever your interest takes you.
I commend Bush for talking about renewable sources such as liquefied coal, methanol, solar just because those areas can be used to recover energy and thereby reduce fossil fuel demand. Key to that are the Grid connection capabilities.
I see the future automobile power plants running on hydrogen fuel cells but only after those nuclear power plants get built. CNN thinks hydrogen is free. Hydride beds will be used as container devices for our cars.
Case in point. If renewable bio fuels are to exist, then we need a massive nuclear power source to provide the balance of energy that doesn't exist right now to make that happen.
Therfore, Montemayor is correct when he says
"All we've done is deplete our biggest and proven option: Nuclear Energy - something the environmental nuts should be very proud of"
RE: Ethanol production
I grew up in little east Tennessee town called Oak Ridge where nuclear energy was first brought to industrial scale. If we hadn't followed a national energy strategy based on 50 years of fear, we wouldn't have an energy crisis now, and fusion technology would likely be here already.
just my opinion,
sshep
RE: Ethanol production
If we can utilize "waste" biomass as a fuel source, I can see that alternative fuel having a chance. Using "virgin" biomass fuel, such as ethanol, is tougher - since you have to spend energy to make it before you use it.
I don't know all the facts in the ethanol debate. But I do know that most people are for recycling waste canola oil as an alternative fuel source. Aside from powering cars, canola is also used in burners to produce heat (e.g. hot water heater, space heater in the garage, etc.)
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Ethanol production
Brazil on the other hand has two or three crops a year, and their cost of labor (field harvesting labor) is cheap.
I once saw an article in a Brazilian paper extolling the virtues of sugar cane/ethanol/etc, it casually mentioned that one other benefit of ethanol from sugar cane was that it provided a lot of employment. Imagine that....a career chopping sugar cane stalks in the field. Oh Boy.
rmw
RE: Ethanol production
If I understand this correctly, the only objection to breeder reactors is that they produce fuel containing plutonium that could potentially be diverted (e.g., by terrorists) to making nuclear weapons. However, in our country, we have made lots of weapons grade material for decades under close government supervision. Why would this arrangement not be feasible for commercial breeder reactors? Isn't the existing waste stockpile enough for our electricity needs for another 75-100 years if we go with this route?
I just need to know where this logic is flawed, if it is. Of course, the reason why this is pertient in the present discussion is that sacrificing our agricultural topsoil in an insane march to make ethanol will deprive succeeding generations of this immense resource, 50% of which has already been lost to poor agricultural practices (failure to practice soil erosion control), etc. Lest people forget, as Professor Galbraith reminded Pres. Kennedy repeatedly, the great strength of the US economy arises from its agriculture.
Finally, whatever happened to real energy and transportation fuel conservation? We still consume a lot more energy per capita than even the Europeans, who are quite offended if we are pleased to declare that their lower energy usage is caused by their having a standard of living that is lower than ours.
RE: Ethanol production
I still have hopes for comercial development of fusion in my lifetime, but current efforts in this direction seem limited.
best wishes,
sshep
RE: Ethanol production
My suspicion is that our public is so scientifically illiterate that even mention of the word "nuclear" drives them berserk. Look at what happened to MTBE, which happens to be used undiluted in certain medical procedures. There, instead of fixing leaks in underground gasoline storage tanks, which according to some may impart a residual odor to the groundwater (and most people can't even detect it, thanks to the extremely low solubility of MTBE in water), we decide to decommission an entire industry. This after we had coerced our refineries to spend an unbelievable amount of money for building a nationwide network of MTBE plants.
This issue too is pertinent, since we are now discussing ethanol as an alternative to MTBE.
I guess that we as engineers must accept our share of the blame for failing to educate the public about just how nasty the energy future will become unless we get rid of the kind of thinking that appeals only to the illiterates and Luddites.
RE: Ethanol production
That said, we in North America spend billions to dispose of soils contaminated with polyaromatic hydrocarbons (from historical "town gas" plants etc.), while we permit people to buy cigarettes- far greater sources of PAH injestion than anyone could imagine getting from soil. Logic and commonsense just don't enter into the environmental equation in the way we technical people think they should!
That point corrected, your post brings up important points about nuclear energy. Unlike a coal plant, a nuclear plant does not broadcast its harmful waste across an enormous area which may even extend across national boundaries- unless it goes the way of Chernobyl. The waste is contained and the technological problem of nuclear waste disposal isn't all that challenging. The radioactive exposure to people from the radioactive emissions of coal combustion (from C13 and radionucleides trapped in the coal) have probably exceeded all the released emissions from the peaceful use of nuclear energy- not to mention the particulate, acid gas and CO2 emissions from coal combustion!
That said, fission plants have to be constructed on an enormous scale to make them sensible. These projects are so enormous and costly that they're at the margins of humans' current ability to manage them as projects. Waste results. Furthermore, the downside of a major nuclear reactor incident is so enormous that operators of these plants are often given exemption from liability for these events. A private for-profit enterprise operating a potentially dangerous process under exemption from liability is a dangerous thing in my opinion. More dangerous than massive coal consumption? I'm still not decided on that one.
The only energy option that doesn't harm the environment is conservation. Why we would not invest at least $1 to fund conservation measures for every $1 we spend to build new generation capacity is totally beyond me!
RE: Ethanol production
http://gif.inel.gov/roadmap/
Generation IV" nuclear energy systems are an ensemble of nuclear reactor technologies that could be deployed by 2030 and present significant improvements in economics, safety and reliability and sustainability over currently operating reactor technologies. Although existing designs, which are denoted as Generation II and III, provide a reliable, economical and publicly acceptable supply of electricity in many markets, further advances in nuclear energy system design can broaden the opportunities for the use of nuclear energy.
The technology roadmap describes the required system research and development (R&D) necessary to develop each of the six selected Generation IV systems and the approximate time to completion
RE: Ethanol production
"Since most of the MTBE in use is in gasoline, then the most likely scenario in the environment is that
gasoline containing MTBE will come into contact with surface water or groundwater or rainwater. Huttunen
(1997) determined the solubility of MTBE in water at 20oC using a 1/10 sample to water ratio, both from
synthetic mixtures of aliphatic and aromatic hydrocarbons and from gasoline. MTBE, from gasolines
containing approximately 1, 4 and 11% by mass of MTBE, dissolved in water to give concentrations of 300,
1100 and 2100 mg.l-1. These concentrations are significantly lower than the solubility of pure MTBE in water."
Of course, I was in error regarding the level at which an MTBE odor can be detected in water. Can carbon adsorption beds remove dissolved MTBE to any meaningful extent?
My real point, of course, is that leaking underground gasoline storage tanks are the real culprit and should be detected and removed forthwith. Couldn't ethanol from gasoline enter the groundwater system in much higher concentrations through the same mechanism, as it is 100% soluble in water?
On the safety issue, I believe that one of the greatest concerns in a nuclear plant is the loss of cooling accident (LOCA). If we located these facilities below large man-made lakes or dams to assure water supply at all times, one would think that the probablity of a LOCA would be rendered minuscule.
In my original post, I was also attempting to advocate diminished reliance on fossil fuels into the indefinite future. Oil and gas are already becoming expensive and scarce and coal plants release a lot more than just CO2, as moltenmetal has already shown. Coal mining accidents have probably killed far more people than all nuclear plant and uranium mining accidents combined.
The frustration I feel is that unending reliance on unstable sources of fossil fuels seems the most reprehensible of all choices, especially if alternative sources that are far less problematical are available. The point made in mechprocess' post makes a lot of sense. However, should we wait for a lot more R&D before changing directions? This entire issue requires vision and leadership, and a way must be found to diminish the influence of the special interests over national decision making. Am I completely off the bend here?
RE: Ethanol production
Further to your points about MTBE: though you can do much to mitigate leakage and spillage by design etc., if you use gasoline leakage and spillage WILL happen. When gasoline leaks into the subsurface, the "sample to water" ratios are a lot higher than 1/10 where partition between water and the parent gasoline sample become important. The partition situation for compounds in a real soil/water system is a lot more complex than the fuel/water system studied in that paper anyway because soil organic content is involved. Regardless, 1 ppm much less 2000 ppm is more than enough MTBE to render water useless for most purposes, and regulatory limits for MTBE are orders of magnitude lower than 1ppm in most jurisdictions.
The solubility of MTBE combined with its low molecular weight render carbon adsorption a poor treatment option. MTBE's solubility and volatility combine to make it at once a poor air stripping candidate and a poor sorber on gas-phase activated carbon as well. There are other options for treating MTBE such as UV/peroxide oxidation, but they're not inexpensive. So MTBE in spilled gasoline IS actually a real technological problem. Sufficient reason to ban its use? If there were no alternatives, certainly not! But there ARE alternatives.
The ethanol in spilled gasoline would be much less of a toxicological concern than the gasoline itself- perhaps even the least of your worries. But I'm with the others here. Everything I've read and all I understand about the process of making anhydrous fuels-grade ethanol tell me the same thing: agriculturally-sourced ethanol is a poor candidate as a fossil fuel replacement from an energetic standpoint. Corn or grain-sourced ethanol is pretty much an agricultural subsidy program masquerading as an alternative fuels program. The jury is still out on cellulose-sourced ethanol. And the fermented mixture from sugarcane still has the same problem: too much water, which costs significant energy to remove. Frankly, until we've satisfied all our STATIONARY energy needs (electrical generation, district heating etc.) with renewables, going after transportation fuels is pretty stupid from an energetic point of view.
RE: Ethanol production
I disagree with moltenmetal - you are completely "off the bend". The source of my opinion is from your statement that, "This entire issue requires vision and leadership, and a way must be found to diminish the influence of the special interests over national decision making." You state that as a possibility, hence my opinion.
You make some excellent points regarding both the MTBE and nuclear power issues that I would support. Given that MTBE has the unfortunate characteristics of being overly soluble in water and readily detectable in a very negative way (and somehow the impact of this combination was not anticipated), it is not the optimum choice for a fuel additive UNLESS the proper steps are taken to mitigate the negative impact. In hindsight, perhaps we should have required double-walled fuel tanks or other robust leak prevention measures as a prerequisite to MTBE usage. Wouldn't that have been insightful? Attack the true cause of the problem rather than being batted around by kneejerk reactions for quick, spare-no-expense "solutions".
Nuclear energy is probably similar. A single design, well engineered nuclear power plant with well developed support systems (e.g. maintenance, procedures, etc.) should be capable of safe effective operation. We can't and shouldn't do a custom basic design for each plant with the greatly increased risk of commiting new errors. Waste disposal is solvable, though I believe government intervention is needed. Inherently safe designs (which you visualize as the lake beneath the fuel rods design) are achievable. And, as you correctly point out, orders of magnitude more people have been killed in operations related to fossil fuel (esp. coal) production and use than in nuclear power operations. All of which support my argument that you are indeed "off the bend"
lol,
Doug
RE: Ethanol production
This entire thread has been an education for me, even at my age. Luckily, I can still escape into the world of model-based control and dynamic simulation to stave off complete senility.
RE: Ethanol production
Can anyone add to the other facts or figures to drive home the opinions regarding the viability of ethanol based motor fuel?
RE: Ethanol production
http://
*real ones not funded by agribusiness, just opposed to foreign oil & interventionism. However, most public interest groups favor conservation, e.g., higher CAFE's.
However, even best agricultural and ethanol production from corn practises max out at an energy balance ratio of 2. Higher figures are given for cellulosic biomass production and biodiesel from soybeans. A small plant in Ottawa Canada is producing 1 million gallons a year of cellulosic ethanol (from Wikipedia below], and given the research efforts of the US DOE et al., this should eventually become major. And of course, plant wastes & ethanol are much less of a groundwater pollution threat than petroleum.
But, I'm doubtful that ethanol from corn represents sustainable agriculture (IMHO plant 'waste' should be returned to the soil to maintain the humus level), and many of Profs. Pimentel and Patzek concerns are certainly valid. http://ww
Comprehensive information on both sides of all of the issues (with many supporting links, rather than opinions) is given in Wikipedia:
http:
As to the nuclear energy tangent, the US auto industry in the 1950's envisioned cars powered by mini reactors. Check out the Ford Nucleon (one exists, at the Henry Ford Museum in Dearborn Michigan): http://en.wikipedia.org/wiki/Ford_Nucleon
Pretty hilarious in retrospective.
Re "Power comes from energy not mass. When we solve the problem of storing energy properly"
-- Energy comes from mass, via one reaction or another!
-- storing energy properly perhaps refers to batteries, flywheels, compressed air...? Anyhow, battery development hasn't lived up to expectations, and Ford & GM have scrapped electric vehicle programs despite happy trial users, a sure indicator of unprofitability. The current emphasis on hybrids as a stepping stone to hydrogen-powered ICs & fuel cells suggests that transported fuel will be with us for a long time.
Finally, dissolving methane or natural gas into a liquid fuel will increase its energy density and make it cleaner burning. This can be done at a much lower pressure than with hydrogen or CNG so safer, could be done at the gas pump to minimize modification of existing infrastructure, would reduce the need for petroleum imports, etc.
http://www.nasatech.com/Briefs/Aug04/MSC22873.html
Earlier work at the University of Oklahoma, but only a brief summary: http://www.otd.ou.edu/tech/98NOR019
RE: Ethanol production
For the massive amounts of gasoline we consume, wouldn't a huge acreage need to be devoted for ethanol production even with a low ethanol/gasoline ratio? Also, what do we all think about the issue of long-term (over several decades) damage to the agricultural topsoil if we make ethanol a major source?
Do we as engineers feel that the nuclear option is not worth pursuing at all? Personally, I think that the commercial realities of power production will soon start hitting us heavily in the pocketbook unless we consider doing something different, and soon. The smart solution is to chart an energy policy that takes technological realities into account while also looking at raw material costs and environmental impacts. However, we must first agree that our present course is flawed or at least that it needs significant modification.
I believe that was what Pres. Bush was emphasizing in his latest State of the Union message. The new demands for petroleum from the developing countries will likely keep the cost sky high for a long time to come. You'll pardon me for recalling that crude oil sold for $3.50 a barrel, nearly 1/20th the current price, when I was studying engineering.
It is clear that we have a significant divergence of opinion in this thread on ethanol as a viable fuel source for the long term.
RE: Ethanol production
I - Fossil energy input for corn ethanol production > output energy as corn ethanol produced *
* according to the several sources hereabove listed
II - Fossil energy input for sugar cane ethanol production < output energy as sugar cane ethanol produced **
** according to some sources I have been checking
In the term fossil energy input all the production stages and insumes are taken into account. That means fertilizers and other chemicals, electric power, steam from oil other gas fired boilers, diesel trucks, tractors, passenger buses, etc
From all I could read about corn ethanol, thanks to the several sources hereabove given, I doubt corn ethanol will ever succeed without distorsive subsidies.
But sugar cane ethanol seems to be another reality. I am somewhat disappointed that nobody went after additional information to support or to deny such conclusion I modestly posed here.
Some aspects about Brazilian economy were here appointed as if they were obstacles to sugar cane ethanol production. I could not take such objections seriously, sorry. Several times this country was near financial collapse and despite that this specific sector of the economy faced no crash. Private inversions continued due to the external market.
So if you do allow me to conclude this way: saying Mr Corn Ethanol and Mr Sugar Cane Ethanol are the same is saying Grouxo Marx and Karl Marx are the same, too.
fabio vincent
www.figener.com.br
RE: Ethanol production
HAZOP at www.curryhydrocarbons.ca
RE: Ethanol production
http:
In this paper the authors analyse thermodynamically the entire production cycle of sugar cane ethanol up to the final usage as engine fuel converted to shaft work.
Please notice that they use the exergetic method taking into account the solar energy (exergy in the case) as the primary source. It is in my opinion a twisted analysis since solar energy is free and all losses mean nothing.
Their analysis concludes that if ethanol could be used in fuel cells (60% efficiency) the balance would be positive.
A simple energetic analysis excluding solar energy input is not there presented.
If you can comment...
fabio vincent
www.figener.com.br
RE: Ethanol production
1. The current intensive industrial practices of sugarcane cultivation started in Brazil about 15-20 years ago, and their long-term effects on the sustainability of today’s high yields are unknown.
2. The only option that gives a marginal benefit is the conversion of the sugarcane ethanol to hydrogen used in 60%-fficient fuel cells to produce electricity (Deluga et al., 2004), but such cells do not exist, see Appendix A.
Note that Patzek said in the earlier corn paper that "Real fuel cells are 2-3 orders more expensive than a car engine, 10 times less reliable, and may never be mass-produced (Keithand Farrell, 2003; Dresselhaus et al., 2003; Bossel et al., 2003; Davis et al., 2002)." "The 60%-efficient fuel cell car does not exist now, or in the future (Bossel, 2003b; Patzek and Pimentel, 2006)."
1. Biomass-for-energy plantations are environmentally costly and inefficient engineered systems, and their long-term high yields are uncertain and questionable.
2. Locally-produced electricity from biomass seems to be the best option that could make a prolific acacia and sugarcane plantation “sustainable,” if their immediate environments were not degraded by the toxic ash and air emissions.
While the results for sugar cane production are somewhat better than for corn, the overall ethanol efficiency as presented in the Patzek paper are dire.
RE: Ethanol production
you probably understand the meaning of exergy and so you are able to understand that all the cumulative exergy consumption of table 28 (from Nitrogen down to seed and BOD) could be used to produce directly useful work. However you also know that part of such exergy would also be lost in any energy conversion system. If you dream to make another profitable use of the total extra exergy (63 GJ/ha-yr)you would obtain only 38 GJ/ha-yr with the same non-existent fuel cell or even only 15-18 GJ/ha-yr with an engine.
Did you see the flaw?
Furthermore the entire study is based on ethanol plants with cogeneration power plants of very low efficiency. This is not correct. Modern plants - the ones the study should have focused at - consists of high pressure boilers which generates surplus of power to the grid (not taken in account in the study). There is no heat used to dry bagasse. It is burnt directly. Furthermore the Diesel use in the cumulative exergy consumption table is certainly above the best practices of such plants: the average round trip of the trucks is not close to 160 km...I'd say it is only 50 - 80 km.
Last but not the least, the average specific production of ethanol is 6500 l (not only 5500 l) and the trend is the increase of such production. Some cumulative exergy consumption would reduce significatively then.
I would read carefully the numbers of the study and criticize them before just echoing Patzek conclusions. He devoted some attention to the question, naturally, but I dare say he is not much used to modern sugar cane ethanol plants...
fabio vincent
www.figener.com.br
RE: Ethanol production
HAZOP at www.curryhydrocarbons.ca
RE: Ethanol production
Dave: If the following violates any site rules please delete it.
APPENDIX: EFFICIENCY OF A FUEL CELL SYSTEM
In their Science paper, Deluga et al. (2004) claim the
following:
. ..Further, combustion used for transportation has .20% efficiency
as compared with up to 60% efficiency for a fuel cell . . . The
efficiency of these processes for a fuel cell suggests that it may be
possible to capture >50% of the energy from photosynthesis as electricity
in an economical chemical process that can be operated at
large or small scales. (p. 996)
Following Deluga et al.,Patzek (2004) used 60 percent as
an estimate of the overall efficiency of a hydrogen fuel cell car.
Even this optimistic estimate could not make the industrial corn-ethanol
cycle sustainable to within a factor of two. Not so with
sugarcane ethanol. It might be called somewhat sustainable if
the path from the ethanol to electric shaft work were 60 percent
efficient.
First, we assume that the cane ethanol-water mixture used to
generate hydrogen is analytically pure C2H5OH and H2O. Thus,
there are no other contaminants to poison 65 the delicate catalyst
that will convert this EtOH-H2O mixture to hydrogen, carbon
dioxide and carbon monoxide (Deluga et al., 2004). The catalyst
is made of a rare-earth metal, rhodium,66 and a Lanthanoid,
cerium. 67 The catalytic reaction is claimed to have 100 percent
selectivity and >95 percent conversion efficiency. We assume
the conversion efficiency h1=0.96.
After Bossel (2003) we summarize efficiency of a Proton
Exchange Membrane (PEM) fuel cell as follows. In fuel cells,
gaseous hydrogen is combined with oxygen to water. This process
is the reversal of the electrolysis of liquid water and should
provide an open circuit voltage of 1.23 V (volts) per cell. Because
of polarization losses at the electrode interfaces the maximum
voltage observed for PEM fuel cells is between 0.95 and
1.0 V. Under operating conditions the voltage is further reduced
by ohmic resistance within the cell. A common fuel cell design
voltage is 0.7 V. The mean cell voltage of 0.75 V may be representative
for standard driving cycles. Consequently, the average
energy released by reaction of a single hydrogen molecule is
equivalent to the product of the charge current of two electrons
and the actual voltage of only 0.75 V instead of the 1.48 V corresponding
to the hydrogen high heating value.68 Therefore, in
automotive applications, PEM fuel cells may reach mean voltage
efficiencies of
h2=0.75 V/1.48 V =0.50 [10]
However, there are more losses to be considered. The fuel cell
systems consume part of the generated electricity. Typically, automotive
PEM fuel cells consume 10 percent or more of the
rated stack power output to provide power to pumps, blowers,
heaters, controllers, etc. At low power demand the fuel cell efficiency
is improved, while the relative parasitic losses increase.
The small-load advantages are lost by increasing parasitic losses.
Let us assume optimistically that for all driving conditions the
net power output of an automotive PEM fuel cell system is about
h3=0 9 of the power output of the fuel cell stack.
Depending on the chosen drive train technology, the DC
power is converted to frequency-modulated AC or to voltage-adjusted
DC, before motors can provide motion for the wheels.
Energy is always lost in the electric system between fuel cell
and wheels. The overall electrical efficiency of the electric drive
train can hardly be better than h4=0 9.
By multiplying the efficiency estimates, one obtains for the
maximum possible tank-to-wheel efficiency of a hydrogen fuel
cell vehicle
h=h1*h2*h3*h4=0.96 ×0.50 ×0.90 ×0.90 =0.38 [11]
or 38 percent. This optimistic estimate agrees exactly with an-other
analysis (31 to 39 percent) (Fleischer and Ørtel, 2003), and
is significantly less than the 60 percent used by the promoters
of a hydrogen economy and hydrogen fuel cell vehicles.
65 The commercial ethanol fuel is very dirty by chemical catalysis
standards, but we will ignore this unpleasantness.
66 Rhodium is a precious metal whose price is about
US$30 000/kg, 3 ×more expensive than gold, http://www.kitco.com/
charts/rhodium.html.
67 The nanoparticles of cerium dioxide are called ceria, and cost
$250/kg, http://www.advancedmaterials.us/58N-0801.htm
68 According to Faraday’s Law, the standard enthalpy of combustion
of hydrogen, H 0
f =.285 9 kJ/mol, can also be expressed as an elec-trochemical
potential (“standard potential”) U 0
=.H 0
f /ne F =1.48
V with ne =2 being the number of electrons participating in the con-version
and F =96485 Coulomb/mol the Faraday constant.
HAZOP at www.curryhydrocarbons.ca
RE: Ethanol production
It seems that you are overly critical. Patzek states that the information on sugarcane ethanol production has not been well described. You on the otherhand seem to be trying to get more precision out of the limited information that is available.
Rather than being focused on the efficiencies of a few processes in the ethanol cycle, you should look at the big picture.
You are also throwing out a lot of terms. Cogeneration is a good example. Cogeneration (also combined heat and power or CHP) is the use of a power station to simultaneously generate both heat and electricity. It remains a mystery as to who you will sell the steam to that you are generating in your power station.
Modern power plants are not orders of magnitude more thermally efficient than older plants.
You also seem to agree with Patzek's theory: No matter how efficient the engine is that transforms the industrial ethanol cycle’s output into shaft work, the cycle remains utterly unsustainable and unattractive as a source
of fossil fuel.
And further. that "Locally-produced electricity from biomass seems to be the best option that could make a prolific acacia and sugarcane plantation “sustainable,” if their immediate environments were not degraded by the toxic ash and air emissions."
RE: Ethanol production
RE: Ethanol production
Old sugar cane ethanol plants have a very small surplus of power generation (let's assume a value as high as 3,3 GJ/ha-yr). Modern ones have higher surplus (I'd say 20 GJ/ha-yr). So the question is not only the power generation but the comparison between surplus supplied to the grid which should be accounted as credits for the ethanol production. The reason for the increase in the surplus is in the fact that a pure Rankine cycle operating between 22 bar/300oC with a few stages turbine (50-55% efficiency) generates half of the power produced by a 60-80 bar / 480-520oC pure Rankine cycle with 75-80% efficiency turbine. That is the trend.
As to the question of the use of the steam, if I have understood it clearly, you probably know that part of the steam is extracted from the turbines and sent to the ethanol plant and the rest is condensed after leaving the turbine exhaust, generating extra power.
I could add some other mistakes: vinasse is not simply treated. It is a source of biogas (0,1 Nm3/ liter of ethanol) or nutrients. Besides all the power used to run the waste water plant comes from the power plant.
I am not overly critical: if the study intends to be a reference on the use/production of ethanol, the numbers must be obtained from modern plants. The methodology used by Patzek is very interesting. No doubt about that. But why to take a low efficiency plant as reference instead of a modern plant? Why should one assume that the extra exergy consumption could be compared directly to the mechanical work at the shaft of an engine fueled with ethanol? Doesn't it bias the conclusions?
I do look at the big picture but I notice some blurred points. After removing or correcting these spots the picture is suddenly other... Just that..
Regards
fabio vincent
www.figener.com.br
RE: Ethanol production
HAZOP at www.curryhydrocarbons.ca
RE: Ethanol production
I'm not an expert on the topic. But a question for you guys. Doesn't it seem like an awfully convoluted process to grow a crop, throw 95% of the plant away, ferment what's left, throw 80% (I'm guessing here) of that crap away, distill whats left, etc.? Isn't there some woody plant where they could just grow the plant, harvest it, chop it, and throw it in a unit coal train and run it to the power plant? That sounds so much simpler.
By the way, someone up there mentioned they don't grow sugar in the US- last I heard, they were growing sugar beets in CO and MT among other places.
Another issue that rears its head is available water. There is real estate in the US to grow a lot of crops, only groundwater is being exhausted in a lot of dry areas.
RE: Ethanol production
It would seem to be more sensible to use plants to capture atmospheric CO2 and solar energy, dry them using solar energy, and then burn them to make electricity and/or heat. Return the ash to the land. That's as close to renewable as you're going to get, and makes the most energetic sense- but only if you use the energy quite close to the point of agricultural production. And even this process isn't sustainable at high yields because it will require energy input in the form of nitrogenous fertilizer, whether that comes by means of crop rotation or by gasifying the same biomass to make hydrogen (to make ammonia to make nitric acid to make fertilizer) instead of using natural gas for that purpose.
If transportation costs are figured into the equation, doing something to get rid of the enormous amount of useless bound water and to increase the energy density of the biomass is required. Anything you do there, whether that be fermentation, pyrolysis or merely drying and pelletizing, will tend to reduce the net conversion efficiency of solar energy capture you end up with. In essence, that's what harvesting the corn is about- you don't need to transport the wet, bulky stalks. But to then do a wet fermentation of the grain in an attempt to make anhydrous ethanol makes little sense to me, even if a proper juggling of the numbers can make it appear to be marginally better than doing nothing and using fossil fuels instead.