Ethanol production 9

[JLSeagull]

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?

 

[sshep]

My prediction is that at some point people will realize that carrying fuel (i.e. chemical reactant that is burned with atmospheric O2) to power our transportation devices is unneccessary. Power comes from energy not mass. When we solve the problem of storing energy properly, we will not be burdened with carrying combustible fuels (gasoline, ethanol, or hydrogen) of any sort.

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

 

[Ashereng]

There is a group of university students in the US somewhere (San Francisco?) that is going around the restaurants and collecting waste canola oil as fuel for their vehicles (I am guessing modified diesels?). It seems to work in small quantities. The restaurants saves disposal fees, and the students get free fuel.

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?

 

[rmw]

While fvincent makes valid points about the differences between sugar and corn, sugar is a moot point in the USA. There simply isn't the real estate available to grow it. It is grown in Florida, Louisiana, and to a minor extent in Texas. There isn't any more real estate available with a climate conducive to sugar cane growing.

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

 

[UmeshMathur]

Having read this thread carefully, I had a question for the nuclear experts: Isn't it true that the main objection to nuclear plants arises from the issue of nuclear waste disposal? Now, I know that hardly any of the U238 in fresh nuclear fuel is consumed in today's reactors, but I understood that the "waste" could be reprocessed in breeder reactors and recycled ad infinitum to extinction. That would eliminate the waste disposal problem, wouldn't it? Also, wouldn't this reduce the need for additional uranium mining drastically? Don't we already have gobs of the spent fuel sitting around at each existing reactor, waiting to be shipped to some "government approved" site that doesn't yet exist?

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.

 

[sshep]

Nuclear waste disposal is a big issue- nobody wants a nuclear "landfill" in their back yard. The big problem is not the high level radioactive waste from the core, which is both small in quantity and potentially recyclable. It is disposal of the tons of medium and low level waste from metals, concrete, etc which have been in close proximity to nuclear material. This is where smart engineering design and operation would minimize such waste, and handle what is produced in a safe manner. At one time there was also great concern about the impact of possible recycle of radioactive metals back into our steel stream, but I haven't heard much of that in the last 10 years.

I still have hopes for comercial development of fusion in my lifetime, but current efforts in this direction seem limited.

best wishes,
sshep

 

[UmeshMathur]

I take it that these medium and low-level wastes are what you must dispose of when you decommission the facility? Have the French (who have a vast nuclear reactor network based on standardized designs) had trouble with this aspect?

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.

 

[moltenmetal]

UmeshMathur: MTBE is soluble to ~ 4% in water- that's 40,000 ppm. In comparison, benzene (the most significant toxicant found in gasoline) is soluble to at most 1000 ppm. It's also pungently odourous- few people would not be able to smell MTBE at 100 ppm in water. In fact it's the relatively HIGH solubility of MTBE in water, along with its environmental persistence arising from its low biodegradability, that rendered it a problem in gasoline. It moves nearly at the rate that the groundwater moves, extending in huge subsurface plumes from the point of release. Remembering that this compound was added to gasoline to reduce harmful tailpipe emissions!

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!

 

[mechprocess]

I got this off the DOE site.

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

 

[UmeshMathur]

I appreciate moltenmetal's correction concerning MTBE solubility. However, I was basing my comments on the following statement (from

http://www.efoa.org/mtbe/pdf/appendix1.pdf):

"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?

 

[moltenmetal]

UmeshMathur: you are not completely 'round the bend! You're just thinking like a technical person in a world dominated by non-technical people!

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.

 

[djack77494]

UmeshMathur,
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

 

[UmeshMathur]

Gentlemen:

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.

 

[JLSeagull]

Although this thread has drifted from the original question the responses are interesting. I too think that nuclear based electrical power is desirable. Transportation was addressed but nobody mentioned the ATF controls on alcohol production and the SDA recipes required for denaturing the ethanol.

Can anyone add to the other facts or figures to drive home the opinions regarding the viability of ethanol based motor fuel?

 

[kenvlach]

JLSeagull, despite the dogmatic tone of the naysayers, the US Dept. of Agriculture, US Dept. of Energy, Michigan State University, Minnesota Dept. of Agriculture, and some public interest groups* do show a positive energy balance for ethanol from corn. For example, see the US DOE EERE's "Net Energy Balance for Bioethanol Production and Use," available at

http://eereweb.ee.doe.gov/biomass/net_energy_balance.html

*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://www.news.cornell.edu/stories/July05/ethanol.toocostly.ssl.html

Comprehensive information on both sides of all of the issues (with many supporting links, rather than opinions) is given in Wikipedia:

http://en.wikipedia.org/wiki/Ethanol_fuel#Ethanol_energy_balance_in_the_United_States

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

 

[UmeshMathur]

Are we talking about transporation fuels only, or the more general question of an energy policy from all sources for the long term? It shouldn't be too hard to store electricity efficiently for transportation in better batteries or other devices, once some of the existing designs are improved.

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.

 

[fvincent]

The question still is:

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

http://www.figener.com.br

 

[owg]

fvincent - The sugar cane issue hinges on climate and labour cost. Study of the Brazil and the Hawaii approaches (good climate, different labour costs) may resolve this issue.

HAZOP at

http://www.curryhydrocarbons.ca

 

[fvincent]

A new link I've found brings an additional study of Patzek and Pimentel on sugar cane ethanol among other biofuel sources. Please check it

http://petroleum.berkeley.edu/papers/patzek/CRPS-BiomassPaper.pdf

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

http://www.figener.com.br

 

[bimr]

Select comments from the Patzek paper:

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.

 

[fvincent]

bimr

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

http://www.figener.com.br