Curing the oil crisis:- Starch or Sugar based Ethanol versus Cellulosic Ethanol

September 26th, 2007

Ethanol as a replacement for petroleum

Back in my undergrad degree, I did some research into the viability of using resources from Australia’s large sugar cane industry as a feedstock for ethanol production.

My research was completed about 10 years ago. I found that for Australia to fulfill its own oil demands with Sugar Cane based ethanol it would need to have the entire arable land mass of Australia under cane and that the cost of production would be around 60c per litre, or about US 2.26 per Gallon.

The Australian retail price of petrol back then was around the 60c mark. It was clearly an impractical and uneconomic proposition.

Replacing Oil with Ethanol?

I went on to spend some time with the Sugar Industry and I found along the way that really my calculations were entirely flawed.

Firstly, I’d assumed that the feedstock for my theoretical ethanol production would be something called Molasses. Molasses is relatively cheap and abundant by-product of sugar production and is often used to produce rum. It contains perhaps 5% of the available sugar produced from the processing of Sugar Cane - with the remainder generally converted into relatively high value crystal sugar (the type we use in our coffee).

Two things have changed since then - the world price of sugar has precipitously declined and the world price of oil has sky-rocketed - so the economics have changed. I thought I’d take this opportunity to cast a backwards glance and go over my figures once again.

Brazil can switch between ethanol and sugar production almost instantaneously!

Brazil (the largest producer of sugar cane in the world) has over the last 10 years or so built the capability to easily tailor their production to either crystal sugar or ethanol - basically if the oil price is high, Brazil starts producing ethanol.

Due to the enormous size of the Brazillian industry the resultant shortfall in crystal sugar tends to drive up the world sugar price - so much so that over the last 5 years or so we’ve started to see the world sugar price (WSP) follow the peaks and troughs of the oil price.

Already, without even realising it, Sugar has become an agro-industrial energy crop. The same thing has happened with corn as well - in recent years the price of maize has doubled in much the same way as the price of oil has.

This is a very different playing field to that I investigated 10 years ago - ethanol production from sugarcane is now starting to become an economic proposition of some merit.

A friend of mine in the south of India has secured the rights to build an ethanol factory in a state called Kerala, so I’ve been speaking to some experts here in Australia on his behalf about the new state-of-the-art in ethanol production.

Cellulosic Ethanol

Kerala has a rather large Coconut industry, and one of the interesting possibilities we are looking at is cellulosic ethanol, which has recently been featured in this great article from wired magazine.

This is still a technology in its infancy, but things are looking very promising. Cellulose is the stuff that makes plants stand up - it’s tough, it contains a great deal of Carbon and it’s not easy to break down.

For all our evolutionary complexity, we as humans haven’t yet developed the ability to utilise cellulose as an energy source in our diet, although that’s not the case for other organisms.

Ruminants like cows, goats and camels are capable of supporting vast populations of bacteria in their gut which digest the cellulose and produce by-products called (again, simplifying) short chain fatty acids which can then be digested by the animal as an energy source.

Termites go a step further - their guts apparently produce these enzymes in-situ without the need for a symbiotic colony of gut bacteria.

In recent years there has been a veritable explosion in the number of companies (and governments) investing in this particular technology.

What are the expected yields of alcohol per tonne of Cellulose?

It’s very hard to find definitive numbers here though that allow us to start looking at the potential economics of using cellulose from plants as a ethanol feedstock.

One article about the economics of cellulosic ethanol production states that the theoretical yield of ethanol per tonne of biomass is 114 gallons (431 litres), but in practice the real (achieved) yield is closer to 70 gallons (264 litres). Unfortunately that particular article doesn’t express ethanol production as percent dry biomass (aka dry matter) so it’s hard to compare it with other studies.

Another article I found goes into a bit more detail and compares potential cellulosic ethanol production between four feedstocks - corn stover (another name for corn stalks), alfalfa stems (lucerne), sugarcane bagasse (the dry fibre left over after sugar extraction, usually burnt as a waste material) and Oak Wood. This particular study expresses Alcohol production as litres of ethanol per tonne of dry matter - a much better measure.

Conversion efficiency (%)
Feedstock Hemicellulose
to xylose
Cellulose
to glucose
Ethanol
yield
(liters/tonne)
Alfalfa stem 96 88 228
Corn stover 92 90 298
Sugarcane bagasse 90 86 267
Oak wood 88 79 278

These figures tend to correlate well with those given in the first reference - that expected production of ethanol per tonne dry biomass is going to be somewhere in the order of 220-280 litres of ethanol. It also correlates fairly well with a ‘tool’ provided by the US Department of energy which allows you to calculate the theoretical yield of cellulosic ethanol based upon the composition of a biomass feedstock.

So.. down to some economics..

Let’s take a reference (underestimate) of dry matter % sugarcane biomass as ~14%. So, for every 1000kg of sugarcane, we’ll assume we’re left with 140kg of dry cellulosic materials after extraction of the sugar. Assuming 260 litres per tonne biomass, that means that we’re going to expect to produce around 36.4 litres of cellulosic ethanol per tonne of harvested sugarcane.

Now the important part - Sugarcane uses what’s called C4 photosynthesis - meaning it’s extremely effective at producing biomass from sunlight - biomass yields are very high and the plant is extremely fast growing. A typical yield of sugarcane per hectare in Australia would be ~ 70 to 150 tonnes cane per hectare per annum. We’ll take the midpoint - 100 tonnes.

This means that from cellulosic sources, we’d be expecting to produce around 3640 litres (961 gallons) per hectare of cane from a material that is otherwise considered a waste product.

What about if we used the sugar too?

Now lets look at the sugar content.

Fleay et al (2006) states that (one tonne of) “sugar yields 0.385 tonnes of anhydrous ethanol” and the specific gravity of ethanol is somewhere between 79% and 81% that of water, meaning we can expect the yield of anhydrous alcohol per tonne of sugar to be (1/.8*385)=481 litres.

In general the CCS of cane (amount of sugar in a tonne of cane expressed as percent biomass) is somewhere between 10 and 14% - and that doesn’t include the sugars available in molasses. Let’s assume that we just macerate the cane, extract the juice and ferment that (a much less energy intensive process than extracting the sugar) - we’ll make a relatively broad assumption that we’ll have around 140kg of sugars available per tonne of cane, which, at our theoretical yield of 100 tonnes per hectare equates to around 14,000 kg sugar per hectare available for fermentation and conversion to ethanol. At 481 litres per tonne of sugar, we’ll be left with around 6735 litres of ethanol per hectare.

So.. we’re left with the following figures.. from a ‘typical’ cane field with 14% fibre, 14% available sugar and 100 tonnes per hectare..

Yield of Cellulosic Anhydrous Ethanol per hectare - 3640 litres

Yield of Fermented Anhydrous Ethanol per hectare - 6735 litres

Total yield of Anhydrous Ethanol per hectare - 10,375 litres

Could Ethanol totally replace our petroleum usage?

Would this be enough to satisfy Australia’s Oil needs?

Let’s assume an annual cane yield of 40 million tonnes, or roughly 400,000 hectares under cultivation - this equates to around 4 150 000 000 litres, or 4.15 billion litres of ethanol per annum (assuming one crop cycle per year)

The energy density of ethanol is only around 70% of that of petroleum so this would equate to around 2 905 000 000 litres (2905 megalitres) of petroleum (although ethanol does have a higher octane rating, which means it burns more efficiently, so this is probably a slight underestimate). Current petroleum consumption in Australia is around 20,000 megalitres per annum, leaving a shortfall of over 17,000 megalitres per annum.

WOW! If Australia was to convert our entire sugar industry to the production of ethanol, we’d only be able to satisfy around 14% of our demand for automobile fuel (not including diesel consumption which is another 4000 megalitres). Keep in mind Australia has only 20 million people.

The scale is enormous - in QLD you can basically drive for 2000 uninterrupted kilometres and all you’ll see growing is sugarcane.

If we wanted to gross up our cane production to satisfy our demand for foreign oil (for automotive use only), we’d need to have around 2,857,000 hectares under sugar cane - the entire cropable landmass of Queensland (approx 20% of Australia’s land mass) is just below that figure. Forget about eating - we’d need to crop our whole state just to satisfy the thirst of the nation’s automobiles. That’s quite amazing and I feel the figures for a country with a much higher population density like the US would be even more compelling - these are interesting figures.

This reinforces a few things to me:-

  1. The massive scale of our oil consumption is easier to comprehend when it is expressed as biomass equivalent production (the amount of oil beneath the earth was phenomenal)..
  2. That burning that finite resource to fuel inefficient vehicles rather than using it for higher value industrial purposes for which no other economic feedstock exists (plastics, medicines etc) is perhaps not the best long term use of an amazing natural resource.
  3. That folks are going to look back at this period of history and wish we had done things a bit differently.

What are your thoughts? Where do you think the future lies? I’d be keen to hear your ideas / opinions.

___________

THE AUTHOR: Matthew holds degrees in Agricultural Science and Computer Engineering. Matt has extensive experience in the Sugar Industry worldwide and has a strong interest in Agricultural Mechanisation, Economic Modelling, Agronomics, Alternative energy, Comms Engineering / Remote Area Comms and Entrepreneurial Start-Ups. Matt is available to discuss these topics, and would welcome contact from anyone interested in discussing their business.

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18 Comments Add your own

  • 1. JLH  |  September 26th, 2007 at 3:09 pm

    Any solution that involves burning carbon based fuels doesn’t help the climate at all. The atmosphere doesn’t care if the CO2 came from burning sugar or from burning oil pulled from the ground.

    Another parasitic energy need forgotten often is ethanol production, at least in our US corn based economy, is the production and use of fertilizers. It takes a lot of energy to bind that nitrogen and deliver it.

    I’ve been involved in the design and building of a few bio-diesel plants lately. I’m not sold on the energy profile yet, but I am sold on the publics desire to throw tax dollars at it, and me to get a part of that money. If I can’t be part of the solution, I’m going to be part of the problem, what can I say? I’m a joiner.

  • 2. theDuck  |  September 26th, 2007 at 3:18 pm

    Ah yes.. but you see, that fails to consider the source of the CO2 which you are burning JLH - in the case of agricultural crops, the plant only releases the CO2 which it has taken in during the growing process - so crop based alternative energy (assuming you also use plant based feedstocks for the production, harvest and processing of the crop) is largely CO2 neutral

    But I agree, nitrogen fertilisers put a significant spanner in the whole CO2 / energy balance equation (here in Aus the majority of N fertilisers are produced using natural gas as a feedstock).

    Realistically I think we’re facing some challenges long term whichever way we go. :-D

  • 3. theDuck  |  September 26th, 2007 at 3:44 pm

    But the N problem is not one which is insurmountable (at least with Sugar Cane). You can plant legumes like soybeans in between each ratoon of cane - basically as soon as you harvest the crop, you cultivate the inter-row and plant soybeans.

    With the right rhizobial innoculants such rotational cropping systems can produce pretty much all the nitrogen a cane crop needs, at least in tropical agriculture.

  • 4. ryan tauro  |  October 9th, 2007 at 3:26 am

    why not use dry bagasse in gasifiers and run STIG(steam injected gas turbines) to produce cheap enviornment friendly electricity& leave alcohol production to the sucrose and molasses.

  • 5. theDuck  |  October 9th, 2007 at 4:17 am

    Hi Ryan!

    Thanks for your comments!

    I’m not an expert on mill technology - but that does seem sensible (after all my hypotheticals above ignore the fact that mills need steam to run). What do you reckon the relative usable energy output would be?

    Matt

  • 6. theDuck  |  October 9th, 2007 at 4:19 am

    oh - and - by the way - the answer to the question you were seaching when you came to my site (how mant tonnes cane per hectare in India) should be somewhere between 40 and 60 tonnes from what I have observed in my travels - it’s pretty low mostly due to poor agronomics and lack of water.

    Matt

  • 7. meoow  |  November 25th, 2007 at 8:59 pm

    duuz anyone noe where i can find the production steps in volved in making ethanol from sugercane

  • 8. AAA  |  December 18th, 2007 at 8:20 pm

    This has to be one of the best articles/analysis Ive seen which is great. I enjoyed reading something from someone who isnt afraid to do some analysis from first principles.

    in regard to the comparison of burning fossil fuel vs biofuel. The important thing is the ratio of carbon below ground level to that above. Once its above ground level, it is metabolised, burnt or what have you into CO2, whether its in forests or whatever. Biofuels are about no net increase in the carbon above the ground in the carbon cycle. Biofuels also encourage the growth of plants which are the most efficient transformers of CO2 into biomass. (changes to biodiversity another issue).

    Starving people are not starving because of a lack of food. Its a lack of food in the right place. When the average body mass index in Australia drops to 18-25, then start telling me there is not enough food or sugar. Just legislate the max sugar in soft drinks from 11 down to 5%. Expensive sugar will do our health no end of good.

  • 9. Ryan  |  April 28th, 2008 at 1:13 pm

    Some of these figures are good. But I can tell you that Brazil currently uses 15.6M/Ha to grow about 430 million tonne of sugarcane. That is about 4% of Brazil agricultural land and for those of you who are wondering, none of which is Brazilian rain forest. By 2020 Brazil is expected to hit the billion tonne of sugarcane mark and produce around 65 billion litres of ethanol. Much of this expansion is at the expense of under productive grazing land and no rain forest. Currently in Queensland alone, uses 2% of its agricultural land for cropping, the rest is marginal farming. Well not all but a lot. The question is could we follow Brazil? I think it’s possible and I definitely think it is better than mining coal. http://www.kholslaventures.com is one VC company that’s making inroads into the thanol industry.

  • 10. racrac  |  April 30th, 2008 at 4:39 pm

    Hello! I’ve read from an article that cellulose must first be separated from the plant material through acid hydrolysis and then the extracted cellulose will be fermented by the Baker’s yeast. Can this extraction process produce high percentage yield of ethanol?

  • 11. theDuck  |  May 2nd, 2008 at 12:36 pm

    @Ryan - My intention here is not to pooh-pooh ethanol as a solution, but just to say that it is not, at least not under current methods of growing the feedstock and producing the ethanol, going to be a bolt-on solution for the looming energy crisis.

    I don’t know if you’ve ever read ‘twilight in the desert’ but the contentions in that book are enough to scare any fair minded person out of their complacency. Peak Oil has well and truly come and gone, and we must be prepared very quickly if we’re to avert an economic catastrophe.

    It’s also enough to make my mouth water re: the opportunities approaching for the sugar industry.

    I actually first joined the sugar industry 10+ years back because of my passion for alternative energy - I could see massive potential there. Unfortunately it’s a bit difficult for a researcher / engineer / scientist like myself to maintain a career path / obtain a good income within the research arm of the Australian sugar industry so I’m now putting that passion aside and moving to the mining industry.. ironically.

    I read the Khosla website and are familliar with their work. Personally I feel that producing ethanol from maize is a ridiculous waste of resources and tantamount to environmental vandalism when C4 plants like sugarcane can do a much better job with far fewer inputs and greater yields.

    I’m leaving the industry with the knowledge that it’s likely that we have a massive future.

    At times I wonder whether that future will be realised within the industry.

    It seems to me that the last 100 years has been spent breeding a top-heavy beauracracy (within the milling and growing sectors) with inertia, stonewalling and complacency as central tenets of their management philosophy - that’s frustrating when you just want to get things done, and it’s the reason that we’ve been losing good people in droves.

    M

  • 12. John Clark  |  June 1st, 2008 at 3:06 am

    Matt,

    I have been doing research in developing a process of conversion of sugar cane to biodiesel. Interesting enough, lab experiments have shown high conversion rates of bagasse, as cut stalks, molasses, and refined sugar to CH4 and C2H4 leaving H2O and unbound C. By usining GTL (Gas to liquid) process, the Methane and Ethylene high value diesel fuel is obtained.Cetane of 50+.

    Do you know of any similar work being done?

  • 13. theDuck  |  June 2nd, 2008 at 11:07 am

    Hi John,

    I haven’t actually come across anything similar before but I’d be interested to know more - certainly I know of various folks that use an ethanol diesel blend to power agricultural equipment, but I’ve never heard of or seen Biodiesel being produced directly from bagasse.

    I’d be very interested to know more - and, indeed, if you’d like a place to write up your invention I’d be more than happy to host it here at utheguru.

    cheers,

    M

  • 14. terence  |  June 11th, 2008 at 1:09 pm

    an australian company is currently building a plant to produse ethanol from sawmill and sugar cane waste.
    Willmott Forests owns half of Ethtec who have the worldwide licence for the process from Apace Technolgy

  • 15. Mary Fay, M.D.  |  July 8th, 2008 at 2:22 pm

    Thanks for this informative site.
    A friend of mine who is a lawyer recently purchased one of the “run your car on water” instructions, spending about 49$. I glanced through it and found it basically almost unintelligible and even if it were, so difficult to do that 99% of the people reading it would be unable to follow the directions.
    That anyone would buy this manual, which basically defies the laws of thermodynamics, is beyond my comprehension.
    That there isn’t a website devoted to telling people not to waste their money on this scam, also defies comprehension.
    What is the alternative to fossil fuel?
    People are so desperate and pressed for cash that we have to answer this question soon.
    Do you see anyway for ethanol to become a real contender in this fight? And, do you see anyway for regular humans to produce high enough purity ethanol in sufficient volume to run their vehicles? What source of sugar would you use, and what energy source for distillation?

  • 16. marilyn clinton  |  September 4th, 2008 at 7:09 pm

    ccl3+nacl4=li+o=s+hbr=h2o=288n.2.b.16n.lipo3+hli=hb+n=h2o+br+nclli1+sop=ixy+n=rna+b=dna+c=ixy+d+ca=enes+o=h2o.
    cures blindness from industrial alcohol.

  • 17. Maika  |  November 24th, 2008 at 11:24 pm

    hello! thanks for the information in here. i would like to ask. i’m a high school student and am planning to use ‘Production of Cellulosic Ethanol from Musa paradisiaca linn. (Saba) Peelings’ as my research/thesis title.

    Is it possible for me to make ethanol from Banana peelings ?

    How will i extract sugar from the Banana peel?

    How much sugar will i have to extract from the peelings to make a big amount of ethanol ?

    thank you for your help. Please e-mail me at maiks_23@yahoo.com for you answers . i really need your help . thank you and God bless you!

  • 18. Oil Crash  |  June 13th, 2010 at 3:25 pm

    I understand that Hubberts peak is true and that we are now past the point of peak oil. I believe many of the current events have to do with this fact and it won’t be long before the main stream media and population wake up and understand what is going on. For me and my family, we are preparing for the next era.

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