Efficiency of Biofuel production

Proponents of biofuels claim that amount of fuel produced by the processes is greater than the amount of fossil fuels consumed in producing this fuel. I won't dispute this claim at this time, but I would like to point out an aspect of the problem that I haven't seen discussed so far. It involves a bit of algebra, which I will walk through. If you have no patience for algebra, you can just take my word for it and skip the next two paragraphs.
Let e be the efficiency of the process (amount of fuel produced divided by amount of fuel consumed), expressed as a fraction. The amount of fuel consumed should include *all* the fuels consumed by every operation involved; manufacturing fertilizer and pesticides, running the tractors and combines, delivering the crop to the distillery, *everything* except sunlight. I realize that these processes consume different types of fuels than what is produced, but I am assuming for now that there is a rule for expressing an amount of one type of fuel equivalent to an amount of a different type of fuel. The fraction e should be greater than one, or else the process is a net loss in terms of energy. Before someone claims that this is impossible, remember that sunlight is an input to the plant growth process that is not a form of fuel consumption. All of the net energy "profit" in the manufacture of biofuels comes from sunlight.
If c is the amount of energy consumed by the process (expressed in terms of fuel), p is the total amount of fuel produced, and n is the net amount of fuel left over for sale, then we have the following two equations: e = p/c (definition of efficiency), and n = p-c (net fuel production is total fuel production minus the fuel consumed by the process). I would like to express total production in terms of net production, or p in terms of n. The first equation can be re-arranged into c = p/e, and plugged into the second to yield n = p-(p/e) or n = p*(1-(1/e)). Isolating p we get: p = n/(1-(1/e))
OK, finally I can get to the point. "Total production equals net production divided by the quantity one minus the inverse of efficiency" means that much more biofuel than you would expect must be made in order for the process to be self-supporting in terms of energy. I have heard claims from ethanol advocates that the ethanol production process is anywhere from 140% to 160% efficient. I will pick a value in the middle and assume that e = 1.5. In this case, 1/(1-(1/e)) is 3. In other words, you must grow three times as much fuel as you hope to sell, and end up using two thirds of your total production just running the process. If we intend to replace a significant amount of our petroleum consumption with ethanol consumption, then enough fuel crop must be grown to produce *three times* that much ethanol. Do we have that much cropland available?
Of course, what is happening in practice is that farmers row the fuel crops using petroleum fuels in their equipment, buying fertilizer manufactured in factories that are powered by coal-fired generators, etc. There is the dilemma: If you run the biofuel industry on fossil fuels, you don't save much in terms of either energy or atmospheric carbon; if you run the biofuel industry on biofuels, you have to use a *stupendous* amount of cropland. Running the fertilizer, pesticide, and distillation processes off of non-fossil fuel energy sources such as wind, solar, or nuclear helps, but I have to wonder if it wouldn't be more efficient to use these energy sources to synthesize fuels directly, and skip the agriculture. Using waste biomass as feedstock is great until your business gets big enough that you start creating a *demand* for waste biomass, and have to bid against competing buyers. (One unexpected side effect of thermal de-polymerization is that turkey guts acquired monetary value.)
Does anyone know what sort of efficiency values are being claimed for algae-based biofuels? If you can get "e" up to 3, you only need to produce 50% more fuel than you intend to sell.
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Paul Ciszek wrote:

Of course, what is happening in practice is that farmers row the fuel crops using petroleum fuels in their equipment, buying fertilizer manufactured in factories that are powered by coal-fired generators, etc.

Who says they have to do that ?
Graham

Eeyore wrote:

Paul Ciszek wrote:
Of course, what is happening in practice is that farmers row the fuel crops using petroleum fuels in their equipment, buying fertilizer manufactured in factories that are powered by coal-fired generators, etc.
Who says they have to do that ?
Graham
That they do speaks volumes about the efficacy of biofuels.

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CJT wrote:

Eeyore wrote: Paul Ciszek wrote:
Of course, what is happening in practice is that farmers row the fuel crops using petroleum fuels in their equipment, buying fertilizer manufactured in factories that are powered by coal-fired generators, etc.
Who says they have to do that ?
That they do speaks volumes about the efficacy of biofuels.

I suspect it says more about the rigid thinking of ADM.
Graham

"Eeyore" wrote in message

Paul Ciszek wrote:
Of course, what is happening in practice is that farmers row the fuel crops using petroleum fuels in their equipment, buying fertilizer manufactured in factories that are powered by coal-fired generators, etc.
Who says they have to do that ?
Graham They could also go back to using straight biomass like the original farm

tractors. Using steam.......or a gas turbine with a gasifier. Or in the short term ICE converted for a gasifier..... Biomass power has come a long way in the past 100 yrs. or so. With some of those improvements a steam or ??? tractor should be equal to or better than the stuff now sitting down at the dealership. Most the old steam tractors where made to burn straw ,stalks,and/or wood. The tractor because of thespeed the engine rolled over had the torque of a ICE with at least three times the horsepower. And on tractors....... wieght for traction and useable torque is the whole ballgame. Some tractor pulls won't even let you run steam tractor because a 10nhp Case. Will come out of the hole with 100hp and pull like a 300-500 hp diesel while turning 200rpm. And worse yet, a lot less noise while doing it .....crowds tend to equate noise to power. And can't understand why it did a full pull on every try.......at 5mph. The largest steam tractor ever built (A German Ottomeyer.....Zeven plough engine........many of your steam locomotive builders also did tractors ) was in the 50's had a nominal horse rating of 32.Intermitant of 310 and pulled like a 1200hp diesel.

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On Apr 14, 6:57 am, nos...@nospam.com (Paul Ciszek) wrote:

Proponents of biofuels claim that amount of fuel produced by the processes is greater than the amount of fossil fuels consumed in producing this fuel. I won't dispute this claim at this time, but I would like to point out an aspect of the problem that I haven't seen discussed so far. It involves a bit of algebra, which I will walk through. If you have no patience for algebra, you can just take my word for it and skip the next two paragraphs.
Let e be the efficiency of the process (amount of fuel produced divided by amount of fuel consumed), expressed as a fraction. The amount of fuel consumed should include *all* the fuels consumed by every operation involved; manufacturing fertilizer and pesticides, running the tractors and combines, delivering the crop to the distillery, *everything* except sunlight. I realize that these processes consume different types of fuels than what is produced, but I am assuming for now that there is a rule for expressing an amount of one type of fuel equivalent to an amount of a different type of fuel. The fraction e should be greater than one, or else the process is a net loss in terms of energy. Before someone claims that this is impossible, remember that sunlight is an input to the plant growth process that is not a form of fuel consumption. All of the net energy "profit" in the manufacture of biofuels comes from sunlight.
If c is the amount of energy consumed by the process (expressed in terms of fuel), p is the total amount of fuel produced, and n is the net amount of fuel left over for sale, then we have the following two equations: e = p/c (definition of efficiency), and n = p-c (net fuel production is total fuel production minus the fuel consumed by the process). I would like to express total production in terms of net production, or p in terms of n. The first equation can be re-arranged into c = p/e, and plugged into the second to yield n = p-(p/e) or n = p*(1-(1/e)). Isolating p we get: p = n/(1-(1/e))
OK, finally I can get to the point. "Total production equals net production divided by the quantity one minus the inverse of efficiency" means that much more biofuel than you would expect must be made in order for the process to be self-supporting in terms of energy.

Has anyone done this for gasoline?

I have heard claims from ethanol advocates that the ethanol production process is anywhere from 140% to 160% efficient. I will pick a value in the middle and assume that e = 1.5. In this case, 1/(1-(1/e)) is 3. In other words, you must grow three times as much fuel as you hope to sell, and end up using two thirds of your total production just running the process. If we intend to replace a significant amount of our petroleum consumption with ethanol consumption, then enough fuel crop must be grown to produce *three times* that much ethanol. Do we have that much cropland available?
Of course, what is happening in practice is that farmers row the fuel crops using petroleum fuels in their equipment, buying fertilizer manufactured in factories that are powered by coal-fired generators, etc. There is the dilemma: If you run the biofuel industry on fossil fuels, you don't save much in terms of either energy or atmospheric carbon; if you run the biofuel industry on biofuels, you have to use a *stupendous* amount of cropland. Running the fertilizer, pesticide, and distillation processes off of non-fossil fuel energy sources such as wind, solar, or nuclear helps, but I have to wonder if it wouldn't be more efficient to use these energy sources to synthesize fuels directly, and skip the agriculture. Using waste biomass as feedstock is great until your business gets big enough that you start creating a *demand* for waste biomass, and have to bid against competing buyers. (One unexpected side effect of thermal de-polymerization is that turkey guts acquired monetary value.)

Good. Less waste is a good thing. But waste plastic (with a lower water content, and typically shipped abroad and dumped in less developed countries) is potentially even more valuable and harder to otherwise dispose of, more toxic etc.

Does anyone know what sort of efficiency values are being claimed for algae-based biofuels? If you can get "e" up to 3, you only need to produce 50% more fuel than you intend to sell.

I've seen no precise figures -- probably because so much depends on how you contrive the process and what your model assumes -- plainly algae from bioreactors attached to flue gases from various production outputs would be different from a farm attached to a sewage plant or open raceway ponds in various locations.
This much we know -- one can produce algae with zero fossil fuel input. Indeed, depending on the economic model one adopts, one can produce algae with NEGATIVE fossil fuel input, since in some cases what one uses as feedstock would demand fossil-fuel energy to remove (e.g. sewage, run off into watercourses, flue gases etc).
You don't need algebra to work out you're ahead on that.
Fran

'Refining' oil seeds to biodiesel doesnt take a lot of heat or distilling...just some warm water. Seems like the main energy consumption is the tractor fuel... which could be biodiesel.. So anything 'left over' after plowing is profit right? One square mile is 640 acres... oilseeds can yield 100 gal per acre, so we have 64000 gal gross. Tractor needs to make 3 or 4 passes across the field... a 10 foot tiller needs 528 miles to cover the field. Anyone know how many mpg a tractor gets? If its 1 mpg you need 528 gal to plow the field. 1500 gal to do it three times. You still have 62000 gal left to sell. Pretty efficent so far.

On Apr 14, 9:04 am, "BobG" wrote:

'Refining' oil seeds to biodiesel doesnt take a lot of heat or distilling...just some warm water. Seems like the main energy consumption is the tractor fuel... which could be biodiesel.. So anything 'left over' after plowing is profit right? One square mile is 640 acres... oilseeds can yield 100 gal per acre, so we have 64000 gal gross. Tractor needs to make 3 or 4 passes across the field... a 10 foot tiller needs 528 miles to cover the field. Anyone know how many mpg a tractor gets? If its 1 mpg you need 528 gal to plow the field. 1500 gal to do it three times. You still have 62000 gal left to sell. Pretty efficent so far.

If we use CO2 (onsite industrial emissions) enriched algae and achieve could yields of 8,000 (and possibly as high as 15,000) gallons per acre bio diesel PLUS 5,000 (or more) gallons of ethanol (or butanol) from the same acre while using the low grade "waste heat" from the "adjacent" industrial processes to run the drying and refining processes (and, if well thought out, possibly some mechanical activity like pumping, stirring, etc) ... there would be very limited transportation except for finished fuel ....
And of course, there is the post process residue that might be marketed as feed or fertalizer.
There appears to be no immediate market competition for process "inputs" as in tradition agri fuels (like corn sugar cane, soye) and no impact on food chain.
Wouldn't "e" be much higher in this algae culture approach?
A side benefit is that a significant amount of CO2 (and other pollutants) from the industrial process would be recovered and recycled. A properly matched industry/farm could recover up to 40% of the industrial CO2 emissions (sunlight limited).

And on tractors....... wieght for traction and useable torque is the whole ballgame. Some tractor pulls won't even let you run steam tractor because a 10nhp Case. Will come out of the hole with 100hp and pull like a 300-500 hp diesel while turning 200rpm.

You're a little off here. You don't want an very heavy tractor in your field. All that weight is good for pulling power but it compacts the soil and can not be used when there's much wetness, it'll sink.
It MIGHT be possible. If you have noticed the very large tractors in use today you have seen that they have 8 and even 12 wheels to spread the weight out so you could possibly do that with a steam tractor.
What I think is the major factor in steam not being used is the fact that steam engines do not operate using the KISS principle. An internal combustion engine is very simple to start, run and not damage. To keep it running all the operator has to do is make sure it is fueled. Also today you almost have to try to damage one. If the oil gets low or the temp too high they shut down. Steam engines on the other hand require a lot of hands on care to keep them running. You also have the problem of transporting fuel to the fields but water as well.

In article , BobG wrote:

'Refining' oil seeds to biodiesel doesnt take a lot of heat or distilling...just some warm water. Seems like the main energy consumption is the tractor fuel... which could be biodiesel.. So anything 'left over' after plowing is profit right?

There is also the fossil fuels consumed in manufacturing the fertilizer, pesticides, and if the seed is purchased from Monsanto rather than grown on the farm, I'm sure there is lots of energy used in producing that.
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