Welcome to European Tribune. It's gone a bit quiet around here these days, but it's still going.

Cut CO2 by 94%, Produce 540% EROEI with Switchgrass!

by Magnifico Wed Jan 9th, 2008 at 05:01:27 PM EST

Switchgrass is nothing less than amazing!

BBC News reports on a new study, Grass biofuels 'cut CO2 by 94%'.

Producing biofuels from a fast-growing grass delivers vast savings of carbon dioxide emissions compared with petrol, a large-scale study has suggested.

A team of US researchers also found that switchgrass-derived ethanol produced 540% more energy than was required to manufacture the fuel.

One acre (0.4 hectares) of the grassland could, on average, deliver 320 gallons of bioethanol, they added.

This is good news for the United States in so many ways:

  1. Fewer CO2 emissions - 94% is almost "carbon neutral"

  2. 540% EROEI - Growing "energy independence"

  3. Better than corn and soy - Less need for harmful herbicides and pesticides, such as Atrazine

  4. Native prairie grass - Improves local biodiversity

  5. Plant once - Reduces erosion and farm fuel consumption

The five-year study on switchgrass (Panicum virgatum) was led by Ken Vogel, a professor at the University of Nebraska-Lincoln and a geneticist for the U.S. Department of Agriculture. His findings are published this week by in the Proceedings of the National Academy of Sciences USA, Net energy of cellulosic ethanol from switchgrass (PDF) (Abstract).

According to Nature News, Prairie grass energy boost studied in the field. There is more energy potential in switchgrass than in other crops used in biofuels. Vogel estimated that annually a hectacre of switchgrass could produce an average of 60 gigajoules of energy if turned into bioethanol. Switchgrass had a net 540% Energy Returned on Energy Invested (EROEI). "Soya bean biodiesel, in contrast, returns 93% more energy than is used to produce it, whereas corn grain ethanol currently provides only 25% more energy. Greenhouse-gas emissions from the switchgrass would be 94% lower than emissions from petrol, they calculate -- that's nearly, but not quite, carbon neutral."

The Reuters story on the study explains how the CO2 savings is made.

Switchgrass plants sequester carbon dioxide in the ground because they have extensive root systems that remain buried after the crop is harvested, Vogel said. Steep greenhouse gas emissions reductions, of about 94 percent compared to gasoline, are contingent on burning switchgrass waste to fire bio-refineries. Unlike waste left over from corn after it is made into ethanol, switchgrass waste cannot be made into the animal feed distillers' grain.


Corn and soybeans need to be planted every year. This causes increased risk of soil erosion and the non-native crops require using herbicides and pesticides that can be environmentally harmful to wildlife and people. Scientific America reports Grass makes better ethanol than corn does. Switchgrass only needs to be planted once and is a plant indigenous plant to the vast American prairie and "once established, the fields yielded from 5.2 to 11.1 metric tons of grass bales per hectare, depending on rainfall". But, there still is a large challenge blocking the adoption of switchgrass ethanol.

But yields from a grass that only needs to be planted once would deliver an average of 13.1 megajoules of energy as ethanol for every megajoule of petroleum consumed--in the form of nitrogen fertilizers or diesel for tractors--growing them. "It's a prediction because right now there are no biorefineries built that handle cellulosic material" like that which switchgrass provides, Vogel notes. "We're pretty confident the ethanol yield is pretty close." This means that switchgrass ethanol delivers 540 percent of the energy used to produce it, compared with just roughly 25 percent more energy returned by corn-based ethanol according to the most optimistic studies.

As noted, the catch is there presently are not any biorefineries that handle the switchgrass. The refineries are currently geared toward producing ethanol from corn and soybeans. However this may be about to change. In a story about the study, Associated Press reports on the effort underway to develop cellulosic ethanol:

Renewable Fuels Association spokesman Matt Hartwig said this latest study adds to the evidence supporting the development of cellulosic ethanol.

"It underscores that cellulosic ethanol production is not only feasible, it is essential," said Hartwig, whose group represents ethanol producers.

Nebraska Ethanol Board Projects Manager Steve Sorum said the industry is excited about the prospects for cellulosic ethanol because the feedstocks for it, such as switch grass, are cheaper to grow. Plus some of the byproducts created in the process can be burned to generate electricity.

Sorum said the key will be developing an economic way to break down the cell walls of cellulose-based fuel sources...

Last year, the Department of Energy announced plans to invest $385 million in six ethanol refineries across the country to jump-start ethanol production from cellulose-based sources, a process that has not yet been proven commercially viable.

When $385 million for cellulose ethanol production is compared to the opportunity costs due to the Bush administration's war in Iraq, our country's "jump start" is laughable. Kansas and Nebraska has spent $7.2 billion on the war and the entire country together has spent over $484.2 billion on it. To me, the nation's priorities are obviously wrong.

Changing to switchgrass-based ethanol would have additional environmental benefits. Growing native prairie grasses can help preserve our country's biodiversity and help reduce erosion and the use of pesticides and herbacides. According to Land of Biofuels? an article in this month's Minnesota Conservation, a journal published by the Minnesota Department of Natural Resources:

From tilling to fertilizing to irrigating to distilling, corn ethanol production consumes large amounts of fossil fuels and water -- offsetting some of the biofuel benefits of being local, renewable, and carbon neutral. And the increased demand for corn puts pressure on farmers to convert grasslands to cornfields. Soil erosion and water pollution increase when grassland is plowed and fertilized for corn. And few animals find cornfields to be as satisfactory for habitat as native grasslands and brushlands...

First, many plants -- particularly native perennial plants -- need far less fossil fuel input to grow, so production of ethanol from native plants would generate less CO2. Prairie grasses, such as switchgrass, big bluestem, prairie cordgrass, and Indiangrass (or better yet, a mixture including wildflowers), also provide superb wildlife habitat. Grasses help soil stay in place and filter polluted runoff. If plant species and genetic makeup, land, and harvest regimen were coordinated to maximize natural resource potential, native vegetation managed for cellulosic biofuels could provide far better homes for ducks, deer, songbirds, prairie chickens, and other native species than row crops.

"We think [biomass harvest] can have a positive benefit, particularly if it means something that's in row crop production now is converted to grass, or if it means we have lands that are decadent that we can then use biomass harvest as a management tool to increase the productivity of those lands for wildlife," says DNR farmland wildlife program leader Bill Penning. For instance, Penning says, DNR currently invests hundreds of thousands of dollars each year in brushland management for brushland-dependent wildlife species such as sharp-tailed grouse. If brush becomes a commodity, management could start to pay for itself.

"That's a win-win situation for us," Penning says. "We couldn't ask for anything more."

Neither could I. Switchgrass is amazing. Let's solve the challenges with cellulosic ethanol, start planting prairie grasses, and get those bio-refineries built. I cannot wait for this future for America and the heartland!

Oh, give me land, lots of land under starry skies above,
Don't fence me in.
Let me ride through the wide open country that I love,
Don't fence me in.
Let me be by myself in the evenin' breeze,
And listen to the murmur of the cottonwood trees,
Send me off forever but I ask you please,
Don't fence me in.

by Magnifico on Wed Jan 9th, 2008 at 05:04:21 PM EST
As the people on Daily Kos have noted 540% doesn't include solar...  so if you want to attack the diary because of this... have at it — but it misses the point.
by Magnifico on Wed Jan 9th, 2008 at 05:17:53 PM EST
Has anyone made the calculation of how many barrels per day would be possible by harvesting all the grass possible?

I have strong doubts it gets even near to 10%. Unfortunately, biofuels are the new agrobusiness ploy. Though it focuses on corn ethanol, the magnitudes are the same, so I recommend you read this at the Oil Drum.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Wed Jan 9th, 2008 at 05:25:17 PM EST
Indeed. This is the key question with regard to biofuels. How much land is needed to replace what percentage of current consumption?
by nanne (zwaerdenmaecker@gmail.com) on Wed Jan 9th, 2008 at 05:38:20 PM EST
[ Parent ]
Another key question is how much is it going to take out of the soil?

Any idiot can face a crisis - it's day to day living that wears you out.
by ceebs (ceebs (at) eurotrib (dot) com) on Wed Jan 9th, 2008 at 05:58:42 PM EST
[ Parent ]
I don't know if that is a major issue. Switchgrass was once one of the dominant plant species of the tallgrass prairie, so it is probably capable of being sustainably cultivated.

The catch, IMO, is in the "tallgrass prairie":

Tallgrass prairie - Wikipedia, the free encyclopedia

The tallgrass prairie is an ecosystem native to central North America, with fire as its primary periodic disturbance. In the past, tallgrass prairies covered a large portion of the American Midwest, just east of the Great Plains, and portions of the Canadian Prairies. They flourished in areas with rich loess soils and moderate rainfall of around 30 to 35 inches (760 to 890 mm) per year.

For non-Americans, this covers the American corn belt (among other regions), so large-scale switchgrass cultivation in its original range would necessarily come at the expense of food cultivation.

The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman

by dvx (dvx.clt št gmail dotcom) on Thu Jan 10th, 2008 at 03:46:57 AM EST
[ Parent ]
Ah, a new marketing tactic. Use percentages rather than ratios.

you are the media you consume.

by MillMan (millguy at gmail) on Wed Jan 9th, 2008 at 07:17:54 PM EST
What would be the ratio for this study?
by Nomad on Thu Jan 10th, 2008 at 04:43:20 AM EST
[ Parent ]
540% = 5.4

you are the media you consume.

by MillMan (millguy at gmail) on Thu Jan 10th, 2008 at 04:45:45 AM EST
[ Parent ]
spectacularly non-spectacular.

Can people write this convincingly about the EROEI when the refineries still need to be tinkered?

by Nomad on Thu Jan 10th, 2008 at 05:04:03 AM EST
[ Parent ]
EROEI should include all inputs at point of purchase to final product outputs at point of sale to be in any way meaningful. I don't know if this was done. If it was, the 5.4 rate for a non-depleteable resource is not too bad. It gives you a yield rate of 81%. As in, of the production, 19% needs to be saved as fuel for processing of next years crop, while 81% can be distributed for other uses. There is still the little issue of production per unit land area, and available land area, in order to determine final production capacity.

One acre (0.4 hectares) of the grassland could, on average, deliver 320 gallons of bioethanol, they added.

So, at a 81% yield rate, we have 260 gallons of ethanol per acre, or 2430 litres/hectare. Supposing a car with 40mpg, we can compute 10400 miles = 16744 km of travel per acre. The US average is 231 miles/week per vehicle (according to the EPA), or 12012 miles per year. This is 1.16 acres per car. I find (quick search, don't know about accuracy) 1.2 acres per person required for food production at current US dietary habits. So 1 car ~ 1 person in terms of land use.
by someone (s0me1smail(a)gmail(d)com) on Thu Jan 10th, 2008 at 05:28:32 AM EST
[ Parent ]
Nice... that's about the clearest proof of the proposition "cars or people" I've read yet.

The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman
by dvx (dvx.clt št gmail dotcom) on Thu Jan 10th, 2008 at 05:33:46 AM EST
[ Parent ]
Note that, for corn ethanol with its EROEI of 125% (compare 540%), and a yield rate of 20% (compare 80%) we have 1 car ~ 4 people - at US levels of consumption! Globally, well... More like 1 car ~ 10 people using corn ethanol.

We have met the enemy, and he is us — Pogo
by Migeru (migeru at eurotrib dot com) on Thu Jan 10th, 2008 at 07:06:32 AM EST
[ Parent ]
Let me include some more on EROEI (Energy Returned On Energy Invested) and 'yield rates'. First a plot, EROEI vs. yield/reinvestment rates:

I.e., assuming we can use the ethanol output as input energy for future crops, what percentage can we sell on, and what percentage do we need to reinvest in next years crop? As we see, the curve is very steep at first, and then flattens out quite a bit. A doubling of EROEI from 2 to 4 is quite a different beast than from 50 to 100, at least in terms of net production. (For both cases I cut my cost of fuel in half, but the first one yields me a net production gain of 50%, while the latter only 1%)

So, for the question of when do higher total production for a crop per unit land area win out over higher EROEI for some different crop, it all depends where on these curves we are sitting. Thus, one must not be blinded by either high EROEI numbers, nor by high gross production numbers alone, but always consider both together.

I think I like the yield/reinvestment rates better than EROEI considering this.

Quick reference table:

by someone (s0me1smail(a)gmail(d)com) on Thu Jan 10th, 2008 at 10:47:33 AM EST
[ Parent ]
Quick reference formulas: EROEI x Reinvestment = 100%, Yield + Reinvestment = 100%

We have met the enemy, and he is us — Pogo
by Migeru (migeru at eurotrib dot com) on Thu Jan 10th, 2008 at 11:00:52 AM EST
[ Parent ]
Well, to be fair, this 3 times better than corn ethanol, which has an EROI of around 1.3.

The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman
by dvx (dvx.clt št gmail dotcom) on Thu Jan 10th, 2008 at 05:31:09 AM EST
[ Parent ]
I didn't mean to argue on the potential switchgrass has in the biofuel debate. The issue is with data presentation.

A long, long time ago, I once debated (and I think I lost) with afew and Mig about the decrease of dietary minerals in foodwares - which were presented in percentages. This is somewhat similar: 540% is essentially correct - but to the unfamiliar eye it looks an astounding number. It smells like a promotional ploy.

by Nomad on Thu Jan 10th, 2008 at 06:42:26 AM EST
[ Parent ]
I can't get the pdf of the study from PNAS, the file seems to be broken. The abstract is available though, as are data tables. Another source is this article to complement the BBC one.

In favour of the study, I'd say two things:

As I pointed out to dvx yesterday in the Salon, a good reason for not dismissing cellulosic ethanol out of hand is that its feedstocks do not require prime arable land. Thus one of the researchers involved:

Major Net Energy Gain From Switchgrass-Based Ethanol

Vogel said he does not expect switchgrass to replace corn or other crops on Class 1 farm land. He and his colleagues are developing it for use on marginal, highly erodible lands similar to that currently in the Conservation Reserve Programs. All the fields in this study met the criteria that would have qualified for this program.

Secondly, this was a fullsize field study over several years in real farm conditions. Previous studies concerned only the postage-stamp-sized plots used in research stations. So this one is more realistic.

Then the doubts set in:

The study claims almost double the biomass tonnage/ha compared to experimental plots. This, they say, is due to higher "agricultural inputs". That, in clear terms, means more nitrogen, enough to double the yield. It's important to note that the estimated ethanol yield/ha depends on this increase in biomass. Either you throw nitrogen at your switchgrass, or you don't get nearly as much ethanol out. Nitrate pollution of soil and water is a major problem and the sustainability of high nitrogen inputs is doubtful.

Next, the ethanol output is (unlike the biomass yield) not measured in real circumstances but estimated.

Major Net Energy Gain From Switchgrass-Based Ethanol

caution should be used in making direct ethanol yield comparisons with cellulosic sources and corn grains because corn grain conversion technology is mature, whereas cellulosic conversion efficiency technology is based on an estimated value," Vogel said.

To be more precise, there are no industrial processes actually on line that could be used; cellulosic ethanol is still at the experimental stage. We are constantly assured, as by the authors of this study, that industrial plant will be installed in a few years' time, and there are subsidies for it etc... But it isn't there yet, methods are far from fixed, and the results of this study (bar the field trials in real farm conditions) are entirely virtual.

Even going on these virtual ethanol output numbers, even highly nitrogen-stimulated switchgrass does not produce as much per hectare as maize (corn). My calculation from the data tables comes to 2,660 l/ha compared to around 3,150 l/ha for corn in the same areas as the trials. In fact, this study places switchgrass at the level of wheat:

Now, it may be on marginal cropland, but if it's using high nitrogen input and still only yielding an output similar to wheat, it sounds a bit like an also-ran.

As for EROEI, the 5.4 (540%) figure depends both on the preceding outputs (biomass and estimated ethanol), and on that old chestnut energy inputs. They will of course be suspected of simplifying and minimising agricultural energy inputs, though I see from the data tables that they quote uber-skeptics Pimentel and Patzek on one or two energy measures. More importantly, their estimation of energy used in the industrial transformation process can only be questionable, since no one knows quite what the process will be yet. The study bases its calculations on the burning of remaining switchgrass biomass instead of natgas in the biorefineries: this is a hypothesis at this stage.

So, yes, as some have pointed out, the big splash numbers (540%!!!) are being used to publicise switchgrass and biofuels at a point where part of the public at least is becoming aware of the food v fuel problem.

In conclusion, I don't think cellulosic ethanol should be dismissed, but this glorified field trial doesn't prove much yet.

by afew (afew(a in a circle)eurotrib_dot_com) on Thu Jan 10th, 2008 at 08:13:02 AM EST
Even going on these virtual ethanol output numbers, even highly nitrogen-stimulated switchgrass does not produce as much per hectare as maize (corn). My calculation from the data tables comes to 2,660 l/ha compared to around 3,150 l/ha for corn in the same areas as the trials. In fact, this study places switchgrass at the level of wheat:
This brings up an interesting issue, which is the possibility of a tradeoff between EROEI and yield per hectare.

Is it possible to get data for this, even possibly for the same crop grown by different methods or under different conditions?

We have met the enemy, and he is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Jan 10th, 2008 at 08:21:06 AM EST
[ Parent ]
Do you mean seeking some optimal point between inputs and yield? I think that's a textbook exercise as far as cost management in farming goes.

But a great deal of agricultural input (whether seen as cost or energy) is surface-linked and invariable. The amount of energy spent on tilling a unit of surface will be the same whatever the yield. (Tilling methods may differ, but in this study the least energy-wasteful method, no-till sowing, is used, which is as it should be). Same goes for most of harvesting (though a higher yield will call for marginally more energy use than a lower).

The key variable would be fertiliser, especially nitrogenous. A typical calculation would be a base amount of N / ha + so much per added tonne aimed for. In an EROEI calculation it would be the energy required to produce the fertiliser + to spread it.

In this study they're aiming for as high a yield as possible because they're aware that the land use problem is now acutely posed. The hitch with that is that chucking nitrogen at a problem creates another, worse problem.

A point in favour of switchgrass compared to wheat or corn (it now occurs to me I should have pointed this out) is that it is perennial. I don't know if the study supposes it should be left permanently in place, or renewed, say, once every five years; but even in the latter case inputs required for sowing would be divided by five compared to wheat, an annual. And corn of course calls for another type of input, irrigation (and the energy associated with that).

Not sure I've answered your question.

by afew (afew(a in a circle)eurotrib_dot_com) on Thu Jan 10th, 2008 at 11:18:20 AM EST
[ Parent ]

I'm not talking about finding the optimal point but about having a plot of EROEI vs. yield per hectare. Is that a linear function? I doubt it because to extract a higher yield per hectare you probably have to use more intense energy inputs (machines as opposed to animal or human labour, etc), degrading EROEI. Lower yields per hectare may require less energy spent on fertilizers, hence a higher EROEI, and so on.

We have met the enemy, and he is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Jan 10th, 2008 at 11:27:15 AM EST
[ Parent ]
In fact I'm sure I haven't, given your conversation above with someone, where "yield" is a different beast.
by afew (afew(a in a circle)eurotrib_dot_com) on Thu Jan 10th, 2008 at 11:27:18 AM EST
[ Parent ]
My question was more along the lines of your answer. Though if the process is to be made sustainable, at some point you have to replace the fossil fuel inputs by a fraction of the ethanol production, and then "someone's yield" becomes important.

We have met the enemy, and he is us — Pogo
by Migeru (migeru at eurotrib dot com) on Thu Jan 10th, 2008 at 11:32:22 AM EST
[ Parent ]
OK. Then the main point is that agricultural inputs have an invariable part -- the needs of tilling, sowing, harvesting -- that is calculated per surface unit. Then a variable part above that, calculated per tonne/ha targeted. This variable part will be mostly fertiliser (in the case of switchgrass).

Once harvested, I think the energy inputs in transport and refining would be per tonne of biomass.

by afew (afew(a in a circle)eurotrib_dot_com) on Thu Jan 10th, 2008 at 11:43:18 AM EST
[ Parent ]
All we need is a gasoline price of $5 to $6/gallon and EtOH or other biofuels from switchgrass can be economically viable. While plentiful and reasonably ecologically viable, it's not cheap. Reasonable in price - yes, but not cheap. Nor will it ever be "cheap". But that's OK, at least by me. Unfortunately, my 2 cents worth does not matter much in this debate.

At present, U.S. gasoline pump prices are around $3 or more per gallon, = $0.79/liter (this is a European based entity, after all), and there are some places with higher prices (up to $1/liter). As the peak Oil juggernaut lurches onwards in time, we will be cruising on past the $1.58/liter barrier, and then biofuels from swithcgrass and just about any other kind of cellulose will make sense. But since you can make big profits on crop derived EtOH and other fuels at present prices, crop to energy applications will be extremely profitable at $6/gallon, also, unless this is legislatively dealt with. Thus, when switchgrass derived fuel is economically viable, major grain prices will have doubled, due to the price equivalency of oil and crops that now and for now on will exist.

But at least switchgrass does sort of put an upper limit on liquid fuel prices, sort of like wind turbines could put an upper limit on the price of electricity, especially if we get some renewable feed-in laws in (at least part of) the U.S. Otherwise, with this marginal pricing, electricity prices will still be determined by Ngas pricing, and that is eventually going to mimic oil pricing.

Also, for switchgrass, it is quite possible to make methane  (=Ngas) by frying the grass in an oxygen-free environment, then taking the syngas and after some processing, convert it to either gasolines, EtOH, MeOH or methane. You can also combine wind turbines with switchgrass frying and water electrolysis (to get additional H2) and make CH4 or other things. Since a lot of switchgrass could be harvested in the US in places far removed from urban areas, and getting Ngas to distant markets is relatively easy (much easier than putting a stainless steel pipeline down for H2 transportation, as a carbon steel pipe with H2 is not a viable or safe option), something else to consider.

C6H10O5 ---> C + 5 CO + 5 H2 (or some variation like
        ---> 3C + 3CO + 2H2O +3H2)

3CO + 3H2 + 3H2 (wind turbines/water) -> 3"CH2" + 3H2O
3CO + 3H2 + 6H2 (wind turbines/water) -> 3CH4 + 3H2O

Highly simplified, but perhaps that gets the idea across.


by nb41 on Thu Jan 10th, 2008 at 11:18:19 AM EST
I doubt that the prairie could long withstand intensive removal of the grass for biofuel. It survived for thousands of years by being a contained system : Grass grew, died, rotted back into soil, except when it was eaten by buffalo and converted into manure.

Start a programme of removing nutrients for mthe soil on a regular basis and the soil will be leached of everything except sand. welcome to the dustbowl of 2050.

keep to the Fen Causeway

by Helen (lareinagal at yahoo dot co dot uk) on Thu Jan 10th, 2008 at 03:51:16 PM EST
That's certainly a problem: I'd guess that you'd be able to get around it to some extent with clever cultivation techniques - some sort of long term rotation might well do the job - you need plants that are going to put back the nutrients you take out with the switchgrass and I guess you can use whatever is left after you process it as a fertiliser: in the end you're taking out pure hydrocarbons of some sort so most of the rest should be left for reuse as fertiliser.

But I'm guessing that rotations  would cut yield down massively. By half? A third?

by Colman (colman at eurotrib.com) on Thu Jan 10th, 2008 at 04:02:14 PM EST
[ Parent ]
The study of course assumes switchgrass fields are being conducted in a conventional way with fertiliser (in this case chemical) spread regularly. To get the yields the study needs for its numbers, the amount of nitrogen in particular poses other sustainability problems (as discussed above).

The residue after fermentation has already been counted into the process as fuel for the biorefinery in replacement of natgas. Otherwise the EROEI goes pop.

In other words, switchgrass conducted sustainably would have considerably lower yields, leading to the need for more surface and more base energy used in tilling/harvesting (and again the EROEI suffers).

Switchgrass on marginal land may be better than using food crops for ethanol, but it doesn't look like a miracle cure.

by afew (afew(a in a circle)eurotrib_dot_com) on Fri Jan 11th, 2008 at 01:31:46 AM EST
[ Parent ]

Go to: [ European Tribune Homepage : Top of page : Top of comments ]