Study: N2O Emissions from Biofuel Crop Production Negates Greenhouse Gas Benefits of Using Biofuels
21 September 2007
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| Relative warming derived from N2O production for crops, crop residues, and forages used in the production of biofuel. Click to enlarge. |
A new study led by Paul Crutzen, winner of a Nobel Prize in Chemistry in 1995 for work on the formation and decomposition of ozone in the atmosphere, re-examines the total emission of nitrous oxide (N2O) from crop production and concludes that growing and burning many biofuel crops may actually raise, rather than lower, net greenhouse gas emissions.
N2O is a by-product of fixed nitrogen application in agriculture and is a greenhouse gas with a global warming potential (GWP) 296 times larger than an equal mass of CO2.
Crutzen and his colleagues calculated that growing some of the most commonly used biofuel crops releases around twice the amount of N2O than previously thought, thereby wiping out any benefits from not using fossil fuels and potentially contributing to global warming.
When the extra N2O emission from biofuel production is calculated in “CO2-equivalent” global warming terms, and compared with the quasi-cooling effect of “saving” emissions of fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species have more favourable climate impacts. This analysis only considers the conversion of biomass to biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment.
—P. J. Crutzen et al.
The significance of it is that the supposed benefits of biofuels are even more disputable than had been thought hitherto. What we are saying is that [growing many biofuels] is probably of no benefit and in fact is actually making the climate issue worse.
—Keith Smith, a co-author on the paper and atmospheric scientist from the University of Edinburgh
The work is currently subject to open review in the journal Atmospheric Chemistry and Physics. Crutzen has declined to comment until that process is completed. The paper suggests that microbes convert much more of the nitrogen in fertilizer to nitrous oxide than previously thought—3 to 5 percent, compared to the widely accepted figure of 2 percent used by the International Panel on Climate Change (IPCC) to calculate the impact of fertilizers on climate change.
For rapeseed biodiesel, which accounts for about 80 percent of the biofuel production in Europe, the relative warming due to nitrous oxide emissions is estimated at 1 to 1.7 times larger than the relative cooling effect due to saved fossil CO2 emissions. For corn bioethanol, dominant in the US, the figure is 0.9 to 1.5. Only sugarcane bioethanol—with a relative warming of 0.5 to 0.9—looks like a better alternative to conventional fuels.
As release of N2O affects climate and stratospheric ozone chemistry by the production of biofuels, much more research on the sources of N2O and the nitrogen cycle is urgently needed...Here we concentrated on the climate effects due only to required N fertilization in biomass production and we have shown that, depending on N content, the use of several agricultural crops for energy production can readily lead to N2O emissions large enough to cause climate warming instead of cooling by “saved fossil CO2”. What we have discussed is one important step in a life cycle analysis, i.e. the emissions of N2O, which must be considered in addition to the fossil fuel input and co-production of useful chemicals in biofuel production.
We have also shown that the replacement of fossil fuels by biofuels may not bring the intended climate cooling due to the accompanying emissions of N2O. There are also other factors to consider in connection with the introduction of biofuels. We have not yet considered the extent to which the high percentage of N-fertilizer which is not taken up by the plants, and the organic nitrogen in the harvested plant material, may stimulate CO2 uptake from the atmosphere; estimates for this effect are very uncertain. We conclude, however, that the relatively large emission of N2O exacerbates the already huge challenge of getting global warming under control.
—P. J. Crutzen et al.
Resources:
P. J. Crutzen, A. R. Mosier, K. A. Smith, and W. Winiwarter. “N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels” Atmos. Chem. Phys. Discuss., 7, 11191-11205, 2007
Algae can fix their own Nitrogen.
Posted by: clett | 21 September 2007 at 07:27 AM
Lol, why do people stick to non-fuels like corn ethanol and rapeseed biodiesel? Even a Nobel should know that these aren't biofuels.
Biofuels are made from non-food low-input biomass crops that are gasified and then liquefied, with the CO2 scrubbed out and geosequestered, leading to carbon-negative fuel.
People should stop writing about things they don't know anything about. Even a Nobel.
Posted by: Gio | 21 September 2007 at 07:38 AM
A visit from captain obvious I guess. Biofuel crops can't be made out of nitrogen demanding food crops. This also has implications on conventional farming an another plus for more green sustainable farming practices.
Posted by: Ben | 21 September 2007 at 07:42 AM
And once again, please stop writing bogus titles with "biofuels". The authors clearly distinguish between biofuels that contribute to global warming and others that don't.
Posted by: Gio | 21 September 2007 at 07:43 AM
The total volume of intensive food and feed agriculture is still much higher than that of biofuel feedstock. If what this article says is true, it would mean that N2O is already a very significant contributor to global warming. This begs the question of why none of the other scientists working on GHG research has kicked up a fuss about it. The actual significance can only be assessed when net specific GHG emissions from the entire biofuel manufacturing process are compared to those associated with dinofuel.
Perhaps Mr. Crutzen is merely weighing the modest CO2 gains of first-gen biofuel crops against the also modest increase in net N2O from their agriculture. In that case, he is simply re-inforcing the message that first-gen biofuels aren't all they're cracked up to be. Useful if you want to diversify your transportation fuel sources away from Russia and OPEC, but slightly counterproductive in terms of GHG emissions.
When it comes to using agricultural wastes as feedstocks for second-gen processes, the story should be different. After all, the N2O is released anyhow in the process of producing the primary crop - usually food or feed. Only when you start growing dedicated energy crops on land that would otherwise lie fallow is there a net increase in N2O production.
Oil algae can fix their own nitrogen, but it's legitimate to ask if they also produce any N2O in the process. The chemistry may differ from that used by soil bacteria. If the production of biofuels from algae is associated with N2O, does it amount to a hill of beans compared to the GHG emissions associated with the dinofuel they displace?
Posted by: Rafael Seidl | 21 September 2007 at 08:01 AM
This is important news. However, the most important points are in the details. To quote “What we are saying is that [growing many biofuels] is probably of no benefit and in fact is actually making the climate issue worse.” Note he says >>many biofuels<<. He does not say all biofuels. The problems with N2O could be avoided by using the right crops.
Clett mentions Algae. What about rapeseed, mustard, and all the numerous species capable of producing their own fertilizer from atmospheric nitrogen. I would like to here the opinion of an expert on this issue. How “doomed” are we with biofuels and Global Warming?
Posted by: Henrik | 21 September 2007 at 08:03 AM
Oil algea using smoke stack flue gas will in fact reduce NOx emissions.
Posted by: Ben | 21 September 2007 at 08:25 AM
Yeap.
It's stuff like this which kills the viability of Jatropha, and Soybeans.
http://greyfalcon.net/lcarough7.png
http://greyfalcon.net/n2o.png
_
That said, Algae is inheriently limited by photosynthesis itself. Running at the theoretical limit, algae could only process sunlight at 11% solar efficiency. Whats more likely is 8%, and it'd lose roughly 3/4ths that energy once it's turned into a liquid.
http://greyfalcon.net/sugarsolar
And then after that, merely using the diesel fuel in a combustion engine is wasteful.
http://greyfalcon.net/biodiesel.png
_
Meanwhile we got solar thermal arrays that can process sunlight at 50%.
http://greyfalcon.net/csp2
http://www.luz2.com/apage/12219.php
_
Or thinfilm, which can process sunlight at 10% and be printed out like newspaper.
http://greyfalcon.net/pv
__________________________
Lastly, Algae has some major hurdles.
http://greyfalcon.net/algae
http://greyfalcon.net/algae2
http://greyfalcon.net/algae3
______________
Overall, I wouldn't give a "bio based" future much credence.
Posted by: GreyFlcn | 21 September 2007 at 08:36 AM
Yeap.
It's stuff like this which kills the viability of Jatropha, and Soybeans.
http://greyfalcon.net/lcarough7.png
http://greyfalcon.net/n2o.png
_
That said, Algae is inheriently limited by photosynthesis itself. Running at the theoretical limit, algae could only process sunlight at 11% solar efficiency. Whats more likely is 8%, and it'd lose roughly 3/4ths that energy once it's turned into a liquid.
http://greyfalcon.net/sugarsolar
And then after that, merely using the diesel fuel in a combustion engine is wasteful.
http://greyfalcon.net/biodiesel.png
_
Meanwhile we got solar thermal arrays that can process sunlight at 50%.
http://greyfalcon.net/csp2
http://www.luz2.com/apage/12219.php
_
Or thinfilm, which can process sunlight at 10% and be printed out like newspaper.
http://greyfalcon.net/pv
__________________________
Lastly, Algae has some major hurdles.
http://greyfalcon.net/algae
http://greyfalcon.net/algae2
http://greyfalcon.net/algae3
______________
Overall, I wouldn't give a "bio based" future much credence.
Posted by: GreyFlcn | 21 September 2007 at 08:37 AM
Henrik,
Nitrogen fixing crops may provide some biofuel potential, but I am unaware of any being considered during these preliminary stages. The crops you mentioned are not N-fixers. Which demonstrates once again that crop rotation has to be considered the only sustainable solution with its concomitant decrease in average yearly yield.
Posted by: Kevin | 21 September 2007 at 08:39 AM
So, switching from fossil liquid fuel to Ethanol/Butanol agro-liquid fuels to feed our ICE liquid fuel guzzlers may not be as good an idea as many led us to believe. Didn't we already know that?
Massive electrification of most transportation vehicles, home HVAC, public, commercial and industrial applications is the logical mid-term solution.
Producing and distributing more clean electricity is not even a major challenge. Most technologies are all there or have been around for a long time.
Let's use agriculture to (better) feed all of us and the 10 billions soon to be. We should not have to make a choice between feeding ICE fuel guzzlers and human beings.
Massive agro-fuel production will quickly double and triple the price of food. Poorer people will go hungry while we keep driving our Hummer like vehicles.
Oil wars will be replaced by agro-land wars.
Progressive installation of (home built) 50 000 new large (5 MW) wind mills + 100 large up-to-date nuclear plants could supply all the extra electrical energy required in North America for a few decades.
Posted by: Harvey D | 21 September 2007 at 08:54 AM
GreyFlcn and Harvey D,
Can electricity make orgnaic matter? Can electricity make plastics and replace industrial oil uses? We could replace all industrial oil uses with waste biomass alone, that adds no NOx (that is not already being added) and acts as a carbon sink.
Posted by: Ben | 21 September 2007 at 09:09 AM
==Can electricity make orgnaic matter? Can electricity make plastics and replace industrial oil uses?==
Can electricity make hydrocarbons?
Yes actually.
http://greyfalcon.net/h2car
Not efficiently enough for energy purposes, but good enough for materials manufacturing.
Posted by: GreyFlcn | 21 September 2007 at 09:17 AM
==Nitrogen fixing crops may provide some biofuel potential, but I am unaware of any being considered during these preliminary stages.==
Nitrogen fixing plants?
You mean like soybeans, and jatropha?
Posted by: GreyFlcn | 21 September 2007 at 09:18 AM
Heh, double post.
But anyways, the abstract link at the bottom is broken.
Here's the corrected link.
http://www.atmos-chem-phys-discuss.net/7/11191/2007/acpd-7-11191-2007.html
I thought the comments section was rather interesting.
Posted by: GreyFlcn | 21 September 2007 at 09:21 AM
GreyFlcn,
Your link leads me to here: http://www.theoildrum.com/node/2397
you mind point out what your talking about in there?
Posted by: Ben | 21 September 2007 at 09:23 AM
Isn't it true according to the above that, for levels of nitrogen oxides to be greater tomorrow than they are today, we'll have to either use more nitrogen compounds per acre on existing farmland, or boost the quantity of farmland under cultivation?
Assuming boosting the quantity of land under cultivation is more likely, biofuels can only be deemed a significant cause of trouble if they take up a significant quantity of that land.
But then there's the "food versus fuel" argument, standing in contradiction to this, i.e., the claim that there is a limited quantity of arable land, and that more biofuels will result in less food.
So if we had 50% biofuels use on arable land under cultivation, and we decided to stop doing so because it produced nitrogen oxides, would we instead let the land lie fallow again? Probably not. And then our nitrogen problems are the same as they were. So if there is a zero-sum relationship between food and fuels, it seems to be that's a much more serious problem.
But if, as pointed out by others, second generation feedstocks require no fertilizers, this latter threat diminishes significantly.
Does anyone know if net land under cultivation increases over time as food demand increases? This certainly isn't true in the USA, but it could be true globally, no?
Posted by: Jim G. | 21 September 2007 at 09:24 AM
==We could replace all industrial oil uses with waste biomass alone==
No we couldn't.
We could replace roughly 0.3% to 0.7% of all of our petroleum needs if we used all availible US waste tallow and waste vegetable oil.
Thats nothing.
http://www.youtube.com/watch?v=OriWEUW_TZI
http://gristmill.grist.org/story/2007/8/9/161921/0550
Posted by: GreyFlcn | 21 September 2007 at 09:25 AM
====GreyFlcn,Your link leads me to here: http://www.theoildrum.com/node/2397
you mind point out what your talking about in there?====
Sure thing, the H2Car process is one which uses waste CO2, and Hydrogen from water electrolysis to create a syngas. This syngas is then turned into liquid hydrocarbons.
It's not very effective for energy purposes. But it does create hydrocarbons for material manufacturing using electricity.
Posted by: GreyFlcn | 21 September 2007 at 09:28 AM
I've seen much high numbers then .3-.7%:
http://www.timberbuysell.com/Community/DisplayAd.asp?id=1462
http://www.ieabioenergy.com/MediaItem.aspx?id=5586
http://www.liebertonline.com/doi/abs/10.1089/ind.2007.3.120
Posted by: Ben | 21 September 2007 at 09:34 AM
I'll have to read through those.
But my guess is that those are using the Perlack study.
One which essentially suspends disbelief with it's amazingly unrealistic assumptions.
http://venturebeat.com/2006/11/05/why-cellulosic-ethanol-will-not-save-us/
Posted by: GreyFlcn | 21 September 2007 at 09:36 AM
Or more likely.
The "enough to run industrial processes"
Is assuming just the industrial processes.
Since industrial processes actually don't use much petroleum. It's almost all electricity.
_
But enough of my assumptions, lemme sit down and read this report.
Posted by: GreyFlcn | 21 September 2007 at 09:39 AM
And what are you burning to make the waste CO2? We could turn waste biomass into bioproducts energy postive without the need for a energy imput like electrolysis (Biomass combined with electrolysis and outside energy imputs in hydrogen assisted biomass pyrolsis could be used to enhance the carbon usage efficency to 100%).
Posted by: Ben | 21 September 2007 at 09:40 AM
Heh, well for the sake of argument, how about we assume we'll use biomass only for material processing.
And forget the silly concept of using biomass as an energy source.
Posted by: GreyFlcn | 21 September 2007 at 09:43 AM
I'm not really interested in four words: "You can't do that."
Why is it that so much scientific research ends up focused on those four words?
I'm not interested in what a few people think we can't do. I want to know what we CAN do. Identifying problems is well and good, but I don't see any solutions suggested here.
Posted by: Cervus | 21 September 2007 at 10:19 AM