Shell to Expand Port Arthur Refinery To Be Largest in US
Three Fuel Cell Pandas to Mantova for Zero Regio

Study: N2O Emissions from Biofuel Crop Production Negates Greenhouse Gas Benefits of Using Biofuels

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.




What we can do is:
Lightweighted Cars
Diesels w/ modern catalytic converters
Plugin Electric Hybrids
Electric Vehicles

What we can't do is:


It's primarily all about changing the demand-side efficiency of our cars.

Any fuel change is purely for compatibility purposes.


Ah yes, another relatively short term is gasoline powered HCCI engines.


Does anyone have any good numbers on the lifecycle emissions of biofuels coupled to CCS?

I read that the NETL and USAF recently studied Coal+Biomass-to-Liquids + Carbon-Capture-And-Storage.

CTL+CCS limits CO2 emissions to a level approximately equivalent (+4% to -5%) to that of the existing petroleum-based fuel supply chain.

If the coal is left out and we stick to BTL+CCS, wouldn't we be going carbon-negative?


I'm not really interested in four words: "You can't do that."

Good, let's look at ways to expand government and increase taxes for the common good. :)


I wouldn't give much credence to CCS either ;D

Playing russian roulette with the earth's biggest carbon sink, and hoping blindly that it doesn't tip things too far, or rebound and push us back the other way, is a rather scary thought.


Besides which, according to this report above, the BTL+CSS would actually be more damaging than CTL+CSS.

And coal-to-liquid is rather scary in itself.


Then of course you have to factor in all the INDIRECT emissions.

And then you get into all the fun impossibilities of doing biomass in the first place, regardless of the emissions.

gavin walsh

GreyFlcn, you clearly have a very negative viewpoint of all biofuels, probably more so than is justified by both the current state of development and future developments (ie second and third-gen fuel crops which will not compete with food crops). That is fine, but please avoid spamming this thread with your links; pick the links that you think are most important, and add them in one go.

"I'm not really interested in four words: "You can't do that."

Good, let's look at ways to expand government and increase taxes for the common good. :)"

jack, it's not clear to me how what cervus said ties in to your response, can you expand on this overly cryptic answer.



Do not misconstrue my words. In this context, "you can't do that" only refers to scientific research similar to what is actually in the article. It has nothing to do with politics, only technology. And I refuse to get into a political argument with you.


I'm going to agree with Gavin and say that you seem overly pessimistic about biofuels. However, I agree that PHEVs, HCCI, DiesOotto, and some limited BEVs will likely have a role.


Do not misconstrue my words. In this context, "you can't do that" only refers to scientific research similar to what is actually in the article. It has nothing to do with politics, only technology.

"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."

You say you're interested in what we can do and tired of people who say "you can't do that." It's a solutions orientation, and I applaud it. However, I think it's fairly apparent that you maintain that attitude with respect to any number of things, so I guess I was just taken aback that you would make such a statement.

Also, why such an attitude should be restricted to "technology" and not human endeavors generally seems an arbitrary distinction.

No need to respond. It was just an observation.


Yeah falcon,

What a senior moment forgetting about glycine max (soybean), it being a N-fixer, but I don't think that the Euphorbiaciae (of which jatropha is a member) can reduce di-nitrogen.


It is only tip of the iceberg.

Agriculture emits much more GHG than combustion of fossil fuels, it is well researched and well downplayed fact. To put numbers into perspective, just released research estimates CO2 emissions from human respiration being 0.6 GT carbon per year, domesticated animals respiration releases 1.5 GTC, plus 1 GTC from decomposition of human and domesticated animals waste; total 3.1 GTC per year. Compare it to 7 GTC emitted by combustion of fossil fuels. Presented numbers do not include huge emissions of methane from domesticated animals farting and belching (regular cow emits close to 600 liters of methane daily), and emissions of GHG associated with growing food for humans and feed for animals:

Politicians do not really give a hood about it. Initial intentions to address GW readily deteriorated into meaningless campaign to tax emissions of CO2 from fossil fuel combustion – no more no less. Examples are plenty:

GHG emissions of New Zealand cattle (farting&belching!) accounts for 60% of total country GHG emissions, and NZ addressed the issue by imposing this week cup&trade system on emission of CO2 from fossil fuel combustion;

Diesel engines contribute to warming more than comparable gasoline engines (due to emissions of Black Carbon –diesel soot, which is very potent heating agent), but European politicians prefer to overlook it and promote diesel proliferation to reduce their addiction to Middle East oil.

Russian natural gas supplied to Europe emits more GHG than, say, use of Polish coal (due to no less than 5% of NG venting in Russia NG industry; NG (methane) is 23+ times more potent GHG than CO2), yet Europe increases import of this clean-burning and convenient HC fuel.

Same with US corn ethanol. It barely has positive EROI, and considering that distillation is almost universally is fueled by coal, and taking into account N2O and soil organic decomposition CO2 emissions during corn growing, corn ethanol is substantial net contributor to GW.

It just happened that corn ethanol is extremely beneficial from other points of view: good PR, reduction of oil import, best invented way to subsidize rural America, good leverage to keep corn prices from periodic collapses, improved food security (25% of corn harvest used to produce corn ethanol in US could be easily switched to food&feed in case of emergency).

My estimations are that corn ethanol in US will reach about 10% of current US gasoline consumption by volume, substituting up to 5% of crude oil demand. Further increase will be slow, but steady: increased corn yields, optimized to fuel production corn hybrids, GM yeasts, cellulosic ethanol, etc. This number will be much higher for Brasil, and much lower for Europe.

Current backlash in European zeal for biofuels is easily explainable: unlike US corn subsidies used by local farmers, European subsidies largely subsidize Indonesian and Brazilian farmers. What for? It destroys rainforest, does not reduce GW, and contributes not much to EU energy security.

In US too, vicious campaign is underway to undermine stock price of ethanol producers. Ethanol producers already saturated mandated quantities of ethanol, and ethanol prices are dropping fast, operational margins of ethanol producers are dropping even faster. I have no doubt that mutual funds and banks, which “experts” are most active in ethanol producers bashing will load-up their stock for cheap, and will get hefty profit when stock rebound in 2008, when Democratic Congress will finally pass stalled legislation to increase biofuel usage requirements.

So, not to worry. Biofuels will not be derailed, just slowed to sustainable level of growth.



In the long term I don't have a problem with biomass being used only as a carbon source, but in the short term in a peak oil event we might need it for energy as well.


Greyflcn, you do realize that the Davis study represents, shall we say, an extreme outlier? There are 3 main isues with it. 1) Nearly everyone else finds that N2O production rates for nitrogen fixers are much lower than that from fertilizer application. 2) They use a precision far too high to be warranted -- if you know the nitrification/denitrification literature you know that there is a very large variance in the rates. 3) Even if we give them points 1 and 2, it's completely irrelevant: nobody grows soy for biodiesel. Nobody would want to grow soy for biodiesel -- the yield is too low.

That is not to dismiss the Davis study out of hand, rather a call to "add it to the database". That's all we can really do with nitrogen budgets anyway; we can't point to any particular study and generalize from the numbers in that study with any confidence.

But you seem to be interested in the topic. If you go through the N2O literature you will find that N2O production rates vary by factors of 5-10 (if you include the Davis study it's more than that). It depends on a range of conditions which apparently control the microbial population. I would not trust any bottom-up inventory that 1) relied on just a few studies for numbers, and 2) does not put large caveats on the results. But since you're interested you might also find the nitrogen chapter in Jacobson et al's Earth System Science to be of interest. And the rest of the book as well -- it's a good one.


==Greyflcn, you do realize that the Davis study represents, shall we say, an extreme outlier?==
Well, if you include this report, then perhaps the USDavis study was actually underestimating things.
Besides which, the USDA studies even admit that they assume the N2O from nitrogen fixation doesn't even exist.
I'm much more compelled to believe that the studies which practically ignore land use and nitrogen fixation are inherently flawed.

I'd even go off the say that they are likely intentionally being distorted to play politics. As is much of the climate science thats been coming out of the GOP.

Keep in mind, this is the same DOE which decided that Geothermal and Hydropower deserved to have 0 subsidies. And is giving more subsidies to nuclear than all efficiency and renewable programs combined.

==Nobody would want to grow soy for biodiesel -- the yield is too low.==
Thats where the massive subsidies come in to play.

==but I don't think that the Euphorbiaciae (of which jatropha is a member) can reduce di-nitrogen.==
Jatropha fixes nitrogen. It's the main reason why it is capable of growing on soils with little fertilizer input. (i.e. It's major selling point)


Way I see it.
Things play out like this.

Bush pushes for 35 billion gallons of "alternative fuel" by 2030.

Bush insists that this fuel not actually reduce emissions. And that it could be anything as long as it creates liquid hydrocarbons.

GOP heavily promotes biofuels/hydrogen. (i.e. Two near impossible supply-side solutions)

OPEC says they are going to constrict their production because of biofuels.

USDA/EIA admits cellulosic ethanol is not likely anytime in the next few decades.

Exxon and Shell comment that because biofuels and hydrogen won't work quickly enough, that we need to create a "temporary" crash program to build up Coal-to-Liquids.


It's called bait and switch.

Promote a fake solutions that "sounds" good, but has no chance of becoming a reality. And then switch to a "temporary transition fuel". And then forget the first part ever existed.

It's also a great way to speak only about fake solutions, and score points for appearing to be "green".

And to drain money/attention away from what could otherwise be successful growth in demand-side energy efficiency. (Like Diesel, Hybrids, and Electrics)


I would greatly disagree about cellulose ethanol:


And you'd be disagreed back at by the EIA / USDA


Then again, I guess you thought that the only limitation to cellulosic ethanol was the enzymes.

Thats like saying the only limitation to corn ethanol is the bacteria.

Jim G.

Above, under what we "can" and "cannot" do, biofuels have been presented as one side of a mutually exclusive choice while diesels, hybrids and phev's are listed as part of the contrary side. So these latter are presumably fossil fuel diesels and hybrids?

No reason one can't oppose coal-to-liquids yet remain openminded about biofuels. Likewise, there's no reason to believe a future with EV's isn't a future with biofuels. It's totally possible the future will contain a mix of these two.


//Besides which, according to this report above, the BTL+CSS would actually be more damaging than CTL+CSS.

And coal-to-liquid is rather scary in itself.//

1. Lol, the Crutzen paper only looks at a few first-generation crops. Sugarcane is clearly not a problem. And I'm sure tropical woody biomass (plantation forests like Eucalyptus) are no net contributors either (or their N2O emissions don't negate their CO2 reduction potential).

2. Secondly, do you really think coal is cleaner than gasoline? How bizarre. I thought coal was a bit more heavy on the CO2. (Crutzen compares with gasoline, not with coal).

3. So we have: sugarcane, other grasses and tropical woody biomass turned into biofuels reduces CO2 compared to gasoline, with the reduction not impacted too much by the N2O tradeoff for these crops (see Crutzen). Since gasoline has far lower CO2 emissions than coal, and the tropical biomass has lower overall emissions than gasoline, we can safely conclude that tropical biomass slashes emissions compared to coal.

In short, if you gasify tropical biomass (grasses like sugarcane - no prob according to Crutzen - or trees like Eucalyptus) and you sequester the CO2, you definitely have a carbon-negative fuel.

There's nothing scary about Biomass-to-Liquids, neither about CCS, especially if you use remote geosequestration sites, which is possible with decentralised BtL production. We could have a winner here.

So I'm gonna ask my question again: any good LCAs on BtL+CCS?

I've read a few papers which show that 'Bio-energy with Carbon Storage' can bring atmospheric CO2 levels back to pre-industrial levels by mid-century, if implemented on a global scale today.

A few references:

Kraxner F.; Nilsson S.; Obersteiner M.1, "Negative emissions from BioEnergy use, carbon capture and sequestration (BECS)-the case of biomass production by sustainable forest management from semi-natural temperate forests", Biomass and Bioenergy, Volume 24, Number 4, April 2003 , pp. 285-296(12

Peter Read and Jonathan Lermit, "Bio-energy with carbon storage (BECS): A sequential decision approach to the threat of abrupt climate change", Energy, Volume 30, Issue 14, November 2005, Pages 2654-2671

Which states:

"Abrupt climate change (ACC) is an issue that ‘haunts the climate change problem’ but has so far been neglected by policy makers. This may have been because of an apparent lack of practicable measures for effective response, apart from risky geoengineering. If achieved on a sufficiently large scale, a portfolio of Bio-Energy with Carbon Storage (BECS) technologies, yielding a negative-emissions energy system, may be seen not only as benign geoengineering, free of the risks associated with other geoengineering, but also as one of the keys to being prepared for ACC. The nature of sequential future decisions is discussed; these will need to be taken in response to the evolution of future events, which is as yet unknown. The impact of such decisions on land-use change is related to a specific bio-energy conversion technology. The effects of a precautionary strategy, possibly leading to eventual land-use change on a large scale, is modeled using FLAMES (see Appendix A). Modeling shows that, using BECS, and under strong assumptions appropriate to imminent ACC, preindustrial CO2 levels can be restored by mid-century. Addressed to ACC rather than gradual climate change, a robust strategy related to Article 3.3 of the Convention may provide the basis for rapprochement between Kyoto Parties and other Annex 1 Parties."

Finally, let's not forget that new crops are already being designed to store more CO2. A few days ago a group of plant engineers announced they've developed an Eucalyptus that captures *three times* more CO2 than normal varieties. And Eucalyptus is already a monstrously effective carbon sink.

Nobody is going to tell me that the N2O emissions from a biomass plantation based on such crops, used in a BECS/BtL+CCS system is going to contribute to global warming.


//Nobody is going to tell me that the N2O emissions from a biomass plantation based on such crops, used in a BECS/BtL+CCS system is going to contribute to global warming.//

Correction (since we could have a winner, and since this thread could become truly historic, ahem, we must write things correctly): nobody is going to tell me that the N2O emissions of such a plantation are going to offset the overall global warming reduction potential of a BECS/BtL+CCS system based on these crops.



Bring CO2 levels back to preindustrial levels by mid-century? If that system is as good as you say, that seems more like "geoengineering", something we should approach with great caution. We would also run the risk of running down our CO2 levels too low, which wouldn't do us any good either--I don't think we want another Ice Age. Perhaps there is an optimal level between what we started with and what we have now that should be investigated, should that tech by deployed globally.



I agree with most of your items at the “what we can and what we can’t do list”. However, I don’t agree that we can’t do biofuels. We are doing it and it is decreasing the free world’s dependence on energy from regimes that are dictatorial and intolerant. Such regimes should have no leverage or means of pressure over the free world. To import energy or food from non-democratic countries is playing hazard with democracy and this should be brought to an end no matter the cost.

Furthermore, the biofuels industry is in its infancy. You mention that commercial cellulosic ethanol is decades away. This is not true. It is only about 18 months from happening. Poet will start doing it in 2009 with a 25 million gallons a year facility.
Other ethanol producers are doing similar projects. After 2010 you will see an exponential growth in commercial cellulosic ethanol not just in the US but globally. And this business will become more and more profitable. The reasons are 1) cellulosic biomass is cheap 2) it is abundant 3) because oil will continue to rise in price, 4) because conversion efficiency from biomass to ethanol will continue to improve.

With regard to this newly discovered relation between N2O from some (but not all) biofuels and Global Warming there is no reason to worry at all. Firstly, the current production of biofuels is minimal. Only about 1 million barrels per day and therefore its GW impact will be minimal as well. We should worry much more about the 80 million barrels a day of crude oil and the annual burning of some 6 billion tons of coal. Biofuels production can be made completely GW neutral by use of renewable energy for its production and by using the right species for growing the necessary biomass.


Yeah, GF, stop trying to cloud up this discussion of a scientific study with other scientific data! ;)


One of the rules of the internet states that one can always find articles and reports to back up their ideology. Believe it or not there is a huge load of scientific reports both bias for and against biofuels, science in these fields have become politicized and untrustworthy.

The comments to this entry are closed.