Thursday, January 10, 2008

Isobutanol - a Breakthrough in Biofuel production?

A paper has just appeared in the science magazine Nature, which reports that appreciable yields of isobutanol (IB) and other higher chain alcohols (1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol), can be produced by fermenting glucose with genetically modified E.coli. Such higher-chain alcohols have a greater energy density than ethanol and are much less prone to absorb water from the atmosphere, being consequently less corrosive toward engine parts. Liquid fuels should be applauded, since they can be handled within largely existing infrastructures and they do not require the fabrication of new engineering on a staggering scale to do this, unlike hydrogen. Since such liquid fuels can be burned in diesel engines, rather than requiring fuel cells for which there is insufficient platinum to provide more than a small percentage of the current number of the 600 million vehicles on the world's roads, this tried and confirmed means is quite adaptable for the purpose.

However, the question of scale remains. The overall reaction for the conversion of glucose to IB may be represented thus:

C6H12O6 --> C4H10O (IB) + 2 CO2 + H2O.

Since the respective molecular weights of C6H12O6 and IB are 180 and 74, if the process were 100% efficient, we might expect a yield of 74/180 = 0.41 g IB/g of glucose. The actual yield is found to be 51%, and so we get 0.41 x .51 = 0.21 g of IB/g of glucose.

The world uses 30 billion barrels of oil each year. Taking the accepted conversion factor of 7.3 barrels per tonne of oil, this amounts to 4.1 x 10^9 tonnes.

There is a difference in the proportion of oil that is used to run transportation and for other purposes, and e.g. the US uses more of it for heating-oil. It is reckoned that 68% of US oil goes for transportation while the value is closer to 72% in Europe (UK). I shall therefore assume 70% for transport as a world average. Hence, 0.70 x 4.1 x 10^9 = 2.87 x 10^9 tonnes of oil are used to underpin world transport per year.

The heat of combustion of IB is 36.0 GJ/tonne (compared with about 30 GJ/tonne for ethanol) and it is reckoned that on an oil equivalent basis, crude oil can be costed-in at 42 GJ/tonne. Therefore we would need to produce (42/33) x 2.87 x 10^9 = 3.65 x 10^9 tonnes of it annually. Since 0.21 g of IB can be made from each g of glucose, we therefore need (1.0/0.21) x 3.65 x 10^9 = 1.74 x 10^10 tonnes of glucose.

If we assume a good yield of 16 tonnes of "sugar" per hectare from beet or cane (corn sugar yields are nowhere near this), we need 1.74 x 10^10/16 = 1.09 x 10^9 hectares of arable land to grow it on, or 1.09 x 10^7 km^2. That's 10.9 million km^2 and should be compared with the total of 14.9 million km^2 there is available over the entire surface of the Earth.

Hence we may deduce that the enterprise would require 10.9/14.9 = 73.0% of all of it. That's three-quarters! Since we still need to grow food for a rising world population and it is reckoned that without oil and gas to make fuels and run modern "industrial" agriculture that 14.9 million km^2 can only support 3 billion people or less than half the world's current population, the idea of using this technology or indeed any other means for turning food crop-land over to crops for biofuels on a large scale just seems crazy.

In pointing out such matters of scale I have been accused of autarky, when suggesting the dearth of land upon which the UK might be self-sufficient to some extent in terms of fuel production, as we are quite a small set of islands. For example, similar reasoning suggests that to produce the IB equivalent of 60 million tonnes of oil that we use each year just for transportation (and another 23 million tonnes is used for heating and as a chemical feedstock for industry) would require 179,000 km^2 of arable land or nearly three times the 65,000 km^2 we have altogether. "Surely you can just import it all from elsewhere," is the general theme, but the sums above show this simply doesn't stack-up on a world scale. It is striking how annoyed some people become when they are presented with hard numbers that fail to support their pet modes of energy salvation; that some technology will snatch us from the jaws of death at the eleventh hour: yet, this seems to me increasingly unlikely.

The US uses one quarter of the world's recovered oil, and so if 68% of that goes for transport, this amounts to: 0.25 x 0.68 x 30 x 10^9 barrels/7.3 barrels/tonne = 698.6 million tonnes oil equivalent. To produce this would need:

(1.0/0.21) x 698.6 x 10^6 x 42/33 = 4.23 x 10^9 tonnes of sugar, grown on: 4.23 x 10^9/16 tonnes/ha = 2.65 x 10^8 ha = 2.65 million km^2 of arable land. This amounts to (2.65/14.9) x 100 = 17.7% of all arable land on earth, or about one sixth of it. For interest, the total area of arable land in the US amounts to about 1.83 million km^2, to take an autarkic view, and so even the US could not be self-sufficient in fuel to any degree using this kind of technology, clever though it is since higher alcohols are usually only produced in minute quantities during fermentation processes.

Interestingly, these higher alcohols are also known as "congeners" and are thought partly responsible for the well known hangover if we drink too much in the way of alcoholic beverages, rather than the ethanol itself. It appears we are due for the mother of all hangovers in consequence of consuming too much energy, and the only cure will be relative abstinence.


Related Reading.
(1) http://nature.com/nature/journal/v451/n7174
(2) "Efficient Biofuel Made From Genetically Modified E.Coli Bacteria." http://www.sciencedaily.com/releases/2008/01/080106202952.htm

26 comments:

Anonymous said...

I am currently writing an article on whether or not isobutanol is the best alternative to petrol and diesel as motor fuel. After reading your article I am questioning whether it really matters as it seems that the Earth will run out of all forms of energy sooner rather than later.

I really liked your article and am taken aback by your use of hard figures, which make it impossible to ignore the energy crisis we face.

energybalance said...

Isobutanol is closer to diesel in terms of its calorific value - about 90% of it, as opposed to 70% for ethanol. However, the figures do show that we are highly limited in how much of it we might produce, certainly if we don't want to use land for fuel that is needed to grow crops for food.

This has been an eye-opener for me too, in realising just how much energy we do use as a human species, and what would be entailed in replacing current versions by alternative, i.e. "renewable" sources!

Regards,

Chris Rhodes.

energybalance said...

Isobutanol is closer to diesel in terms of its calorific value - about 90% of it, as opposed to 70% for ethanol. However, the figures do show that we are highly limited in how much of it we might produce, certainly if we don't want to use land for fuel that is needed to grow crops for food.

This has been an eye-opener for me too, in realising just how much energy we do use as a human species, and what would be entailed in replacing current versions by alternative, i.e. "renewable" sources!

Regards,

Chris Rhodes.

Anonymous said...

Just a thought, how about useing ethanol more efficient. Since ethanol and gas do burn differant and have differant properties, lets take advantage of what ethanol can do. Use a low proof (50% ethanol/ 50% water), high compression engines. If we can get 50% or higher efficiency, then 1 gallon of ethanol can replace 1 gallon of diesel along with very low emissions. Sound Good. :)

energybalance said...

This is an interesting thought indeed and it raises a few questions.

If you dilute the ethanol 50:50 with water then the energy content of the fuel is halved to around 15 GJ/tonne.

i.e. about one third that of hydrocarbon fuels.

Agreed, in a diesel engine more miles are obtained per gallon (tank to wheel) than is the case in spark ignition engines which use petrol.

But why not just use pure ethanol? The other point is that such a water-rich mixture would prove highly corrosive to engine parts at high temperature which is a drawback to ethanol generally since it absorbs water very readily.

Regards,

Chris.

Anonymous said...

Using hydrous ethanol allows higher compression without pre detonation. The water keeps the combustion temp down to almost eliminate NOX and Particulates. The water also absorbs the heat energy and gives increase thermal efficiencies. We are not using traditional spark for ignition. We feel new engines can be produced around the issue of corrosion.

energybalance said...

That's very interesting. I should like to learn more about the technology?

Regards,

Chris Rhodes.

Anonymous said...

I keep hearing comments from critics that bio-fuel production consumes more energy than it produces, however they seem to forget that bio-fuels are to a large part concentrated solar energy in chemical form, and that any production of bio-fuels that reduces fossil fuel consumption reduces net carbon emissions. How can any alternative to fossil fuels be a bad thing even if efficiency is significantly reduced.

energybalance said...

The issue of energy-return over energy invested is controversial, and in principle I agree that any source of fuel (beyond oil) is a good thing.

However, replacing that 30 billion barrels of oil per year that the world gets through can't be done using fuel-crops, because there isn't enough arable land worldwide.

We need to grow food too, and the issue is do we feed cars or humans. There are figures that suggest growing algae and converting that into fuel by hydrothermal liquefaction might be the better bet.

My own feeling is that we will relocalise into smaller communities that need far less in the way of transport, and that fuel cold be produced on the small scale to supply each community - I wrote before about a "village pond" idea where each community produces its own algae and thus fuel.

Each community could also produce its own biochar, adding up collectively to around one billion tonnes per year, out of the apparently 8.5 billion tonnes of carbon emitted into the atmosphere by our burning of fossil fuels.

Regards,

Chris.

Costas Lambropoulos said...

Hello all,

the last comment about local communities creating own bio-fuels is 'hitting the nail on the head'.

It is also my belief that bio-fuels can very quickly make a big difference in agricultural communities.

I am convinced that bio-fuel projects are social engineering projects as well.

We are working on a 100% organic process in creating B100 bio-diesel that can be used in diesel engines without the need to modify the fuel system.

Foodstuff from any kind of veg oil /PPO (recyclable / algae / rapeseed), anything available to the local community can be used.

In the island I am at the moment (Kefalonia in Greece) 580 tonnes of oils are collected annually for recycling.

This will go long way for creating fuel for the oil-fired central heating systems for the houses, diesel for the agricultural engines and the fishing / tourist boats... and the rest of energy needs can be taken care by utilising wind and solar power...(when the politician allow it)...there are 12 Wind Turbines up on the top of the mountain working for 3-4 years now and they still not allowed to be connected on the local electricity grid!!!

Bio-diesel won't solve the global CO2 problem if we create it in massive plants (central production) because we increase the 'wheat to wheel' CO2 used transporting PPO from the fields / recycling centres to a central place and transporting fuel wherever.

Local communities can create and use the fuel locally in smaller plants, enhancing the autonomy of the local communities and decreasing their dependency to the fuel producing countries.

As the Roman used to say 'bit by bit my citizens Rome will be built'...in the same way millions of small independent plants will be creating the fuel locally (in a 100% organic manner) will create a collective difference and creating wealthier local economies..

Your comments?

Take care and have a fantastic day





Small plants will also be replicable under licence and no chemicals will be required in the process (or ethanol from fossil fuel) or need to be disposed of chemicals after the process is complete.

energybalance said...

Hi Costas,

thanks for this interesting information. My feeling is that small communities are the way to go, in the sense of needing less transportation in the first place and also providing much of what they do then need locally. That would indeed - in my opinion - include, biodiesel, algae and other forms of biomass fuel.

Regards,

Chris.

Paul Roman said...

Thinking that we have to grow extra crops is a bit funny to me. the amount of waste product that comes off all farms is enormous. The ships that get to port and prices are to low get offloaded to dumps to keep prices high. Lets just take the waste and make fuel.

energybalance said...

Hi Paul,

I quite agree, there is the problem of growing food crops vs. fuel crops, i.e. we can't feed engines and people and it makes a lot of sense to turn our waste into fuels.

There are methane producing digesters of course but in principle waste could be turned into liquid fuels too.

Regards,

Chris.

illuminoughti said...

It is important to differentiate the the several technologies that are associated with biofuel production, here. This arguement applies to all agricultural based biofuels. It also demonstrates the inefficiency of crop diversion at all. I would assert that this same demonstration can be made for all current biofuels which are dependent on use of arable land. It is simply non-sustainable.
If one really looks at the potential solutions available, only an aquacultural solution is viable as a replacement for fossil fuels. Once you realize that the origin of fossil fuels was aquatic, the solution to the problem becomes much clearer. Simply because we have not developed aquacultural methods in the west does not mean that the rest of the world is so technologically backward. There are numerous aquaculture based solutions in the pipeline all over the world. The oceans can be made productive, so too can non-arable land using seawater. Usage of waste streams from society has only begun to be tapped: CO2, along with NOx sequestered washed from stack smoke in H2O from the ocean or even sewage must be considered as a feedstock. The first shift has to be in the way of thinking about the problem.

Anonymous said...

Apparently there is a way to produce
isobutanol that does not require any agricultural input "sugar" and could be one of several technologies that will help us to grow our fuel and save all those precious carbon atoms for a better use than simply burning them.
http://www.pddnet.com/news-ucla-researchers-produce-liquid-fuel-isobutanol-121109/

David said...

WHO says that a source for ethanol - or even isobutanol - has to be found on dry land? Nearly 70 percent of the Earth's surface is covered by oceans. SURELY there is a species of plant - somewhere in the ocean - that could be easily converted to one of the appropriate alcohols, and used to fuel our engines.

energybalance said...

Hi David,

there is certainly interest in harvesting seaweed (macroalgae) and microalgae for conversion to fuels, including ethanol. In principle, seaweed could be garnered from the oceans and microalgae grown in tanks which avoids the competition with using crop-land for either food or fuel crops.

All such strategies will take huge amounts of engineering to bring them to fruition however, and it is debatable how much time/conventional energy there is for the task.

Regards,

Chris,

Anonymous said...

Hydroponically grown, genetically engineered algae, cultured in tubes stacked in tall towers with good southern exposure, located in places where the land isn't usable for regular agriculture. That's the way to go for churning out large quantities of isobutanol or any other designer alternative to gasoline with anywhere near the same energy density. Fermenting food, grains and corn, into ethanol to mix with gasoline and lower the efficiency of gasoline engines, plus all the energy the ethanol requires to produce above the amount gasoline requires to refine from crude oil - that simply makes no sense at all.

energybalance said...

Agreed, using land to grow "fuel crops" makes no sense beyond the small scale. Fuel and food production must fall into conflict otherwise. You propose a GM-means to produce algae, using photobioreactors, maximising the solar flux by having them facing south.

I think you have a valid strategy here.

Very true too what you say about lowering the energy of hydrocarbon fuels by mixing them with biofuels, and indeed the exact energy costs of ethanol production remain a highly vexed issue.

Regards,

Chris Rhodes

Kentbiofuel said...

Hi,

Great Blog! Would this be Fourth Generation Bio Fuel then?

There is not enough first generation fuel being used.

This short video explains how anyone anywhere can refine their own biofuel

http://kentbiofuel.blogspot.com/2011/01/how-to-make-bio-fuel-out-from-waste.html

I have really been inspired to do more by your site! The Science and the Data is First Class...

Thank You!

Warm Regards,

Tim
http://kentbiofuel.blogspot.com

energybalance said...

Hi Tim,

since this involves a "GM bug", then yes it would be fourth generation as in Craig Venter's schemes.

Kind regards,

Chris Rhodes

Anonymous said...

Hi Chris,

It seems I stumbled upon this post a little after-the-fact. I love these sorts of numerical approximations. They give a good sense of whether things are even worth looking further into. So I do this a lot, myself.

I wanted to point out that the land area of the earth is actually 149 million km^2, not 14.9 million (wikipedia.org/wiki/Earth). This is a consequential difference. What was going to require 73.0% of land now requires "only" 7.32%. That percentage grows to about 34% when you look only at arable land (31 million km^2, .../wiki/arable_land). That is still unacceptably high, for all the reasons you go on to state. But a *portion* of that might not be.

Cheers,
Nick

energybalance said...

Hi Nick,

I'm not talking about the total area of land, which is about 30% of the grand total of 500 million km^2, but the area of quality crop (arable) land which is about 10% of that or 15 million km^2.

Now I accept that more land might be used to grow stuff on, and so I accept that 31 million km^2 figure. That noted however, the problems we are alluding to remain.

Cheers,

Chris

energybalance said...

My last comment, on reading it back, isn't as clear as it might be! What I mean is 500 million km^2 as total earth area and so 30% of that gives 150 million km^2. The rest being covered by water.

We then have even if there is 30 odd million km^2 of land that can be used to grow crops on, the issue of growing crops to feed cars or people. We can't do both.

Cheers,

Chris

Anonymous said...

How about the clippings from roadside mowing, wind damaged trees and land that lays fallow to stabilize food prices, are they taken into concideration in the formulas? How much does the Department of Agriculture pay farmers not to plant land? It seems that part of tjis crisis is avoidable, just the ineffinicity of our government..

energybalance said...

I don;t think they are but with new technology could provide "sugars" for fuel. The situation in Europe in regard to farmers being [aid to produce or not produce is infamous, leading to e.g. potato-mountains and wine-lakes!

I think that we will need all sources of fuel, particular that produced on the local level but a depletion of say 5%/year in conventional crude oil would be very hard to substitute by biofuels.

Chris