ethanol redux

This is in reference to this column. In it, Cecil derides ethanol saying that all it does is make ADM rich at tax payer expense. He also says that claiming that ethanol provides more energy than it takes to make is a violation of the laws of thermodynamics. Whether or not it’s true that corn ethanol is energy positive is debatable, but it isn’t impossible prima facie because we’re talking about an open system. The calculations only take into account the energy that you have to pay for to produce ethanol, not the energy imparted into the system by the sun.

But what I really want to know is if his criticisms are true for cellulosic ethanol. If you don’t know, this process turns cellulose into sugar via enzymatic action and then turns the resulting sugars into ethanol the old fashioned way. I know that since I can’t buy it yet, it isn’t ready for prime time, but will it be? How soon? What barriers stand in the way of its economic viability?

Thanks for your help,

Most ethanol in Australia is produced in Australia by the fermentation of molasses and wheat by-products. You’re effectively recycling waste products some of which is burnt to produce the energy.
The main barrier is consumer acceptance, we are told adding ten percent to you gasoline is safe for your but people just don’t believe it after some undeniable engine failures due to using too much.
Give us an engine designed to run on ethanol and I’ll happily run as strong a blend as available but till then the refineries can keep their ethanol.
Regards Charlie

Rob the open/closed energy aspect doesn’t affect the net energy balance issue of harvest energy input vs produced energy output. Cecil’s point was it requires more energy to harvest and produce ethanol than it contains. If it costs 90,000 BTU of petroleum energy to produce each gallon of ethanol which contains 77,000 BTU, we’re consuming more energy than we’re producing. How much stored solar energy ethanol contains is no more relevant than how much stored geologic energy petroleum contains. What counts is total production energy input vs total output energy.

However that’s not the biggest problem with ethanol working on a sufficiently large scale to make a meaningful difference in world (or U.S.) energy posture.

The big problem is there’s not enough land to produce the needed ethanol, no matter what method is chosen. Ethanol clearly works on a small scale. However we have a big problem and need a big solution.

Very roughly, the world uses about 100 quadrillion BTUs of transportation energy per year. To supply that via ethanol would require 1.3 trillion gallons of ethanol per year. An optimistic average ethanol yield per acre using efficient feedstocks is say 500 gallons per acre per year. Therefore it would take 2.6 billion acres – roughly the entire continental United States – just for ethanol production. What about just supplying 1/2 that amount via ethanol? Even for that, there’s not enough new arable land. Also even supplying 100% of the world transportation energy still doesn’t solve the petroleum problem.

The transportation sector only constitutes about 50% of petroleum consumption, even that gigantic step wouldn’t solve the root problem. Conventional oil would still run out.

Finally, a reply! Regarding the efficiency of ethanol production, I cannot debate whether or not ethanol production is efficient. I was merely pointing out that there is no violation of the laws of physics if the net energy output is positive. I also want to know how much cellulosic ethanol changes things. Is it efficient? By how much? If not, what would need to happen and how likely is that? Also, how much of the 10^14 BTUs goes to the US? How much of that is used for transportation?

I don’t think ethanol is the silver bullet which will save us, but I do think that it might be part of the solution. Conservation, nuclear, wind, water and solar (if costs come down and efficiency rises enough) energy need to supply more of our energy needs, and I feel like hybrid vehicle systems running ethanol could help. It doesn’t have to be ethanol, but that is currently the most viable alternative fuel.

Thanks for your help,

And you were right to do so; it’s simply false to invoke the 2LoT on the equation of fossil fuel required to produce ethanol; when the energy in the ethanol doesn’t come from the fossil fuel - it comes from the sun. I’ve seen and commented on this flawed agument several times here on the board and elsewhere.

It is entirely possible to produce ethanol from plant matter without burning any fossil fuels at all, indeed without burning anything.

Well, you are going to burn glucose cutting down the corn. :slight_smile:


Cellulosic ethanol is more efficient from an energy in vs energy out standpoint, however the yield and acreage problem remains. There just isn’t enough extra arable land to produce the massive quantities of ethanol needed to make a big difference in the overall energy problem.

The world uses about 400 quadrillion BTUs of energy per year, of which very roughly 25% (100 quadrillion BTUs) are transportation. The U.S. uses about 25% of those numbers, which is roughly consistent with the share of economic production – energy consumption in developed countries is roughly tied to economic output.

The energy problem can be divided into transportation and non-transportation. In general non-transportation energy comes from sources (coal, nuclear, hydro) which will last quite a while. By contrast transportation energy comes mostly from petroleum, which may hit peak production within a few years, then begin declining.

Therefore the most immediate energy problem is conventional petroleum. Other energy sources (esp. coal) will last over 200 years at current consumption rates.

The problem is petroleum is a global resource. US road vehicles gasoline consumption is only 44% of total US oil consumption, 11% of total WORLD oil consumption, 16.7% of total US energy consumption, and only 3.9% of world energy consumption.

Even if EVERY gasoline CAR in the US switched overnight to Mr. Fusion, peak oil would still happen, just a few years later. That is the shocking reality.

The only alternative transportation energy source I’m aware of which could be scaled upward to the gigantic level required and within a meaningful timeframe might be biodiesel from high-yield algae. At least mathematically it can produce the required output from the available acreage. Whether it’s actually possible would require further study:

Note above consideration of petroleum is from conventional sources. There are large stores of non-conventional petroleum in the form of tar sands and oil shale, plus huge amounts of methane in methane hydrates. There will likely be a large environmental cost to obtaining these, but unlike some nightmare scenarios, the oil supply won’t simply stop when conventional petroleum runs out.

What I was after when I started this thread was to know how cellulosic vs. traditional ethanol changed things vis-a-vis Cecil’s column. Given your figures, how much land is required to grow fuel for 85% of the gas burning vehicles in the fleet, assuming they could all run on E85?


Cecil’s concern was mainly energy balance, not land acreage required. It’s true cellulosic ethanol would greatly change the energy balance aspect, and in that respect his article is incomplete. Unfortunately that doesn’t solve the acreage problem, so ultimately the ethanol feasibility problem remains.

There’s just not enough land, even when using agricultural wastes for cellulosic ethanol production. This was extensively studied by Battelle Labs, who found the limit was about 50 billion gallons of ethanol per year. IOW producing this amount would use all available agricultural waste streams and all US unused agricultural land. To produce more would require removing acreage from food crop production. (350k .pdf):

Now, 50 billion gallons per year is a lot – in fact a 10x increase from current U.S. ethanol production (4 billion gallons per year). However the U.S. alone burns about 210 billion gallons of gasoline per year. Ethanol contains about 62% of the energy as gasoline, so this would offset 31 billion gallons of gasoline consumption per year.

That would reduce U.S. gasoline consumption by 15%, which is a big decrease. Due to decreased demand, it would decrease gasoline prices, near term. However it wouldn’t change the big picture. U.S. road vehicle gasoline consumption only constitutes about 11% of world oil consumption, so world consumption would only decrease by 1.7%. Oil is a global resource, and peak oil ( would still happen, almost unchanged time-wise.

Out of curiousity, what’s the other 56%? Heating oil? Plastics? Other energy usage of some sort?

I don’t have the specifics, but crude oil is used for many things besides gasoline for road vehicles: diesel, heating oil, heavy lubrication oil, plastics, fertilizer, jet fuel, etc. If every gasoline vehicle on earth vanished overnight, it would eliminate less than 1/2 of world petroleum consumption.

How does technology like that of BRI Energy change things, assuming that they can do what they say they can?

Also, what if some of the transportation energy were shifted to the grid, via plug-in hybrids or something? One heartening things is that according to your figures, grid capacity would only have to increase about 16%.


BRI is apparently converting unused municipal wastes to ethanol. That was considered in the above Battelle study, and using all available unused waste plus all unused arable crop land would produce about 50 billion gallons of ethanol per year (in the US). A huge increase, but far too little to solve the big problem.

We must always differentiate between something that works on a small or even medium scale, vs something that solves the main problem of petroleum running out (or greenhouse emissions, depending on your priority).

We must also differentiate between something the US or western Europe could do, vs a global solution. E.g, rapidly industrializing nations such as China and India consume much more energy per GDP dollar than western countries. Without major efficiency improvements, as they continue industrializing, they will soon consume more energy than the US does. Already China consumes more coal than the US. The point is if every car in the US and Europe switched to ethanol, the growth in energy consumption by other rapidly-industrializing countries would absorb this savings in a very few years. Conventional petroleum is a finite global resource.

You can shift some to the grid via plug-in hybrids or even battery electric vehicles (BEVs). Despite having a bad rep, BEVs would work quite well in many environments, as the US average commute distance is only 11 miles.

However – such changes may make us feel good about “doing something”, but (even if adopted on a huge scale) aren’t enough to significantly affect the big problem.

My statement was all US gasoline (not petroleum) consumption amounts to about 17% of total world energy consumption. That includes world consumption of heating oil, diesel, wood, etc, not just utility generation. The world consumes about 400 quadrillion BTU (4.22E20 joules, 1.18E17 watt hours) per year. Thus 17% of this is 20,000 trillion watt hours, or equivalent to about 2,300 nuclear power plants of 1GW each. That’s more than the entire total US utility generation capacity, which was 4E15 watt hours in 2004: Electricity - U.S. Energy Information Administration (EIA)

There is some unused “off peak capacity” on the grid, but not enough. Unused capacity margin varies from 14% to 20%. That’s enough for thousands of BEV cars, which is still a drop in the bucket against the big picture.

What is the solution? It’s possible there’s no solution, and certain there’s no easy one which is economically, technically and environmentally attainable in the remaining timeframe before peak conventional oil.

However oil won’t simply run out, as there are vast non-conventional sources such as oil shale and tar sands. Tapping these will likely have a large environmental and economic cost, but since the fabric of modern society runs on petroleum, that must be measured against the disruption of running out.

The only renewable transportation fuel I’ve seen which is theoretically scalable in a useful timeframe to the vast level required for a meaningful difference is biodiesel from high-yield algae. Whether that’s actually possible or whether there are unseen problems would require further research.

For non-transportation energy, hydro, nuclear, plus remaining coal will last for centuries at current consumption rates. So the energy situation is very different for transportation (largely petroleum) vs non-transporation sectors.

Ah, I didn’t notice that you mentioned road gasoline use, specifically. So if all of the diesel vehicles on the road (presumably mostly semis) also converted to some non-petroleum fuel, would that help significantly?

On the matter of peak oil being a global problem, I certainly agree that even if the US cut off all of its oil usage, the easy oil would still run out. But from a purely selfish standpoint, it wouldn’t be our problem any more. And from an altruistic standpoint, if we can reduce our oil usage, so can everybody else (though it might take longer in some parts of the world).

It’s also possible that there are many solutions, no one of which is enough, but which, all taken together, are. People can use smaller cars, or carpool, or use public transportation (much of which is powered on the grid, and therefore uses no petroleum at all). What waste material we have can be converted to diesel, ethanol, or other fuels. Some folks can use plug-ins. None of these will, by itself, solve the problem, but they’ll all help. And get together enough things that help, and eventually, the problem is solved anyway.

Yes, the more petroleum usage you replace the more it helps. However there are limits on what’s possible. There’s probably no solution available within the remaining time to peak oil. Even a gigantic crash program would take a decade or more to filter through the system.

Even if 100% of US gasoline vehicles were powered by nuclear fusion, peak oil would still dramatically impact the US (and world) economy, since we use petroleum for many things besides gasoline. Whether only gasoline increased to $15/gal or every petrochemical product likewise increased, you’re still impacted. There’s huge non-transportation petroleum use – more than for transportation. Fertilizer, plastics, road asphalt, tires, pesticides, detergents – we are surrounded by items made from petrochemicals. Ethanol for transportation doesn’t solve this. Even with all US gasoline vehicles replaced with alternatives, peak oil would still be a big problem for the US.

This is a common notion, but is unfortunately incorrect. If every car on earth vanished overnight and was replaced by flying carpets that ran on zero point energy, peak oil would still happen, only delayed a few years. Transportation gasoline (in the US) accounts for about 44% of US petroleum consumption. World transportation gasoline consumption is an even smaller % of world petroleum consumption, since the world burns preportionally less gasoline as a % of total petroleum consumption.

If you overnight magically replace all cars on earth with perfect clean alternatives, on a world wide basis that would only reduce petroleum consumption about 33-40%. The world would still be using petroleum at huge rates, just for other things – jet fuel, diesel, heating oil, plastics, fertilizer, etc. Since petroleum consumption increases about 2-3% per year (scales with economic output), in about 25-30 years you’ll be right back where we started (in terms of total consumption rate). And during that period, we’re still consuming petroleum at fantastic rates, only somewhat less than before. IOW 66% of a gigantic consumption rate is still huge.

You can even mathematically place an upper bound on the time difference to exhaustion of conventional petroleum based on all cars worldwide being eliminated. It’s shockingly less than you’d expect.

There are about 1.2 trillion barrels of recoverable conventional petroleum left. We’ll optimistically assume it’s all recoverable at current rates and extraction costs to the last drop. Current world consumption is 31 billion barrels per year. That’s 38 years at current rates, but consumption increases at about 2% per year. Thus we use the formula for compounded expenditure of a fixed amount:

n = int(log(P0*r/A + 1) / log(1+r)), where

P0 = the initial fixed ($1.2E12 barrels)
A = the initial amount withdrawn (31E9 barrels/yr)
r = the rate of increase of the withdrawal (2%)
n = resultant number of years supply

At current consumption rates that gives 28 years to total exhaustion of conventional petroleum. If all cars were magically replaced overnight, world petroleum consumption would drop to about 20.5 billion barrels per year. Using the above equation, that gives 39 years to total exhaustion of conventional petroleum. So eliminating all cars yields only an 11 year difference, and even that requires a magic impossible solution.

In reality oil extraction rates will decrease, and peak oil will impact things much sooner, but this gives an idea of the problem scope.

So how does algae help? Do you need to use it in concert with all the other non-petroleum technologies or can it pick up most of the slack on its own? I haven’t had time to finish the pdf you posted yet, so forgive me if this question is answered there.


A key point is whether any alternative energy can be scaled upward to the gigantic level required for a meaningful difference. With biofuels that equates to fuel yield per acre. Algae has by far the highest fuel yield per acre of any biofuel – 250 times that of soybeans, 50 times that of corn ethanol, and about 25 times that of sugar beets or sugar cane.,

Another key point is where you grow the feedstock crops. Corn requires a certain climate and soil type, and hence competes with food crop acreage. Some other higher yield ethanol crops such as switchgrass can grow on marginal land not well suited to many crops. However algae ponds can be sited in desert locations not used for anything.

In theory biodiesel from algae could power the entire U.S. vehicle fleet (assuming all cars were diesel), grown in a small area of the dessert southwest. The advantage over ethanol is it’s doable in the available real estate and has much better energy balance. A disadvantage is it requires diesel engines, but the technology for that is off the shelf and very refined. Like ethanol it could use the existing distribution and infrastructure (pipelines, trucks, filling stations, etc). By contrast hydrogen would require totally new everything.

There could be hidden problems with biodiesel from algae if used on a gigantic scale. However those are hidden and currently unknown. By contrast the problems with ethanol (esp. from corn) are known and mathematically obvious, even now.

Ethanol per se isn’t totally bad – if you use the highest yield production such as switchgrass plus use cellulose production and waste stream sources, scale it to the maximum available real estate and production, it could provide maybe 15% of US vehicle fuel. That’s significant but only a relatively small % of the overall transportation energy problem.

The problem with Cecil’s article is it focuses almost exclusively on the energy balance issue, not the other issues that impact viability of ethanol, or any other biofuel.

Terrific contribution to the board, Joema, and I hope you stick around and join up! I, for one, would gladly kick the can if you’re short of the readies …

This doesn’t mean that a complete solution is impossible, just that if it exists, it must also take into account those other uses for petroleum. For anything you can name that uses petroleum, I can name a way to make it without petroleum. In fact, the biodiesel you mention could probably be used for many of them. It’s just a question of making it practical. And partial solutions are still better than nothing: If we converted all road vehicles to non-petroleum fuels, for instance, then when oil production does decline, road transportation costs would not be one of the things affected.

The problem is the non-transportation petroleum makes the problem twice as hard. Even invoking magical solutions for 100% of the world’s transportation petroleum doesn’t solve the non-transportation consumption. That shows how difficult the problem is.

The issue isn’t how to make it without petroleum, but rather how to make the gigantic quantities needed in an economic, sustainable fashion. Yes you can produce small quantities of plastics, road asphalt, etc. without petroleum. However the world usage of those is on a titanic, gigantic industrial scale. There are many solutions that work well on a small basis but cannot be scaled to the gargantuan level required. I’m not aware of any technology that could replace most non-transportation petroleum at the current usage levels.

Partial solutions can be worse than nothing if they’re the wrong solutions. Cecil pointed out one example of this in his corn ethanol column. A partial solution that diverts attention and resources into a blind alley is ultimately harmful. There are several likely examples of this, including corn ethanol and hydrogen fuel cells.

You’re right that biodiesel from algae could theoretically be further scaled up to handle, say, heating oil. I don’t think you could make road asphalt or plastics from biodiesel, but am not sure. I think the petroleum components for those are already removed from the crude oil input stream before conventional diesel is made.

Yes, converting a significant % of road vehicles to non-petroleum fuels seems a good idea, if that can be achieved within a meaningful timeframe relative to conventional oil exhaustion. If you pursue technologies that can’t be scaled upward to the huge levels required or which take several decades to implement, it does little good – peak oil has already long happened.

Note this assumes a conventional view of peak oil. The pragmatic truth is it’s unlikely any substitute will be ready in time, and non-conventional petroleum sources will be tapped, including tar sands and oil shale. There’s probably 100+ years of those available at current consumption rates, although environmental and economic costs of extraction will be high.