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Researchers Evaluate Greenhouse Gas Reductions from Different Cropping Systems

3 April 2007

Researchers from Colorado State University and the US Department of Agriculture, Agricultural Research Service have conducted a complete lifecycle analysis of greenhouse gas emissions from biofuel production from a variety of crops.

Study results revealed that when compared with the lifecycle of gasoline and diesel, ethanol and biodiesel from corn and soybean rotations reduced greenhouse gas emissions by nearly 40%. Use of reed canarygrass reduced emissions by 85% and use of switchgrass and hybrid poplar reduced emissions by about 115%. Hybrid poplar and switchgrass were found to offset the largest amounts of fossil fuels and therefore reduced emissions the most out of the studied crops.

Biofuels have a great potential to reduce our dependence on imported gasoline and diesel fuel. We have performed a unique analysis of the net biofuel greenhouse emissions from major biofuel cropping systems by combining ecosystem computer model data with estimates of the amount fossil fuels used to grow and produce crops for biofuels.

—William Parton, Colorado State University

Different crops vary with respect to length of plant life cycle, yields, biomass conversion efficiencies, required nutrients, net soil carbon balance, nitrogen losses and other characteristics which in turn impact management operations. Additionally, crops have different requirements for farm machinery inputs from planting, growing, soil tillage, applying fertilizer and pesticide and finally harvesting.

Parton, Stephen Del Grosso and Paul Adler from the USDA used the DAYCENT biogeochemistry model, developed by Parton and Del Grosso, to account for all of these factors as well as integrate climate, soil properties and land use to accurately evaluate the impact of bioenergy cropping systems on crop production, soil organic carbon and greenhouse gas fluxes. The study assessed soil greenhouse gas fluxes and biomass yields for corn, soybean, alfalfa, hybrid poplar, reed canarygrass and switchgrass.

DAYCENT simulates flows of carbon and nitrogen using daily weather, soil texture and land management as inputs.

Although fossil fuel inputs are required to produce and process biofuels, hybrid poplar and switchgrass converted to ethanol compensate for these emissions and actually remove greenhouse gasses from the atmosphere when the benefits of co-products are included. Greenhouse gas savings from biomass gasification for electricity generation are even greater. This research provides the basis for evaluating net biofuel greenhouse gas emissions and highlights the need to improve the technologies used for large scale conversion of biomass to energy and to more fully exploit agricultural co-products.

—Stephen Del Grosso

Bioenergy crops are able to offset carbon dioxide emissions by converting atmospheric carbon dioxide into organic carbon in biomass and soil, but the production of biofuels requires fossil fuels and impacts greenhouse gas fluxes. The primary sources of greenhouse gas emissions associated with crop production are soil nitrous oxide emissions and the CO2 emissions from farm machinery, farm inputs and agricultural processes. Colorado State and USDA scientists quantified all of these factors to determine the net effect of several bioenergy crops on greenhouse gas emissions.

The study is published in the April 2007 issue of Ecological Applications.

April 3, 2007 in Biodiesel, Cellulosic ethanol, Climate Change, Emissions, Ethanol | Permalink | Comments (26) | TrackBack (0)

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How do you reduce emissions by more than 100% as stated ? ? ?

Does this mean that with 115% GHG reduction, mass production of biofuels from switchgrass and hybrid poplar could reverse the current trend and progressively reduce GHG?

USA + Canada (as the climate warms up) have the land areas required to produce the biofuels required, once feedstock selection and productivity have been optimized.

Will we do it or let lobbies push for the development of more dirty coal + tar sands based fuels and energy?

Are the $100 billion being spent to quadruple tar sands extraction a wise investment? Wouldn't it be wiser to use half that money ($50 billion or more) to develop and mass produce switchgrass/hybrid poplar based biofuels + PHEVs + BEVs.

The 115% figure means that not all the carbon content is converted to biofuels. That extra 15% is likely to be charcoal that remains after pyrolysis thereby storing the absorbed carbon for millenia if worked into the soil.

Easy, the amount of carbon and nitrogen being sucked up, or absorbed by the switchgrass and the like, is greater than it exudes into the atmosphere. Plants soak up carbon and nitrogen, some more than others, and the process to grow, harvest, produce, and use in energy creation, is less than it soaks up.
Great study. Let's get switchgrass cellulosic ethanol going on a mass scale production already!

The 115% could mean that after the plant is harvested, some of the carbon sequestered remains trap in the soil (as roots) I've seen alternate studies with mix-species (hybrid switchgrass) that showed that more CO2 was being sequester by the plants then was produced from utilizing the biomass, which means net negative CO2 production!

This has to be one of those sophistries and nonsense accounting "savings" so favored by environmental cynics with an axe to grind. Whereby a gram of CO2 from a long dead plant or animal is somehow different from a gram of CO2 from a recently dead plant or animal, and accounted for differently.

Saying that a recently dead plant gram of CO2 is "recycled" when taken up by newly growing plants while a long dead plant's gram of CO2 when taken up from a newly grown plant is not "recycled", is pure stupidity if not malicious cupidity.

Furthermore a moments reflection shows that it is actually contra-indicated.

To the newly growing plant a gram of needed CO2 is indistinguishable what ever the source of the CO2.

But re-introducing and making available, the long dead plants CO2 to the biosphere, helps to remedy the stunted plant growth of this era. All it does is raises the overall trace of CO2 from a trace to a trace plus a smidgen of a trace.

This now newly available CO2, "fertilizes" all plant growth, producing more growth by any and all plants, and is obviously to be preferred to all but professional worry warts or cynical exploiters of FEAR.

Stan,

Where are you going with your argument? I can understand that yes we don't know how long the CO2 sequestered by the plants stays in the soil, but besides that I don't see where your going.

Stan, the difference is there was more CO2 in the atmosphere when those long dead plants went under. So for us to be putting that CO2 back into the atmosphere is still recycling, however it's adding to the amount of CO2, where as taking it from a recently dead plant isjust putting CO2 back into the atmosphere that was already there.

Stan is operating from a standpoint of complete climate change denial. Therefore he doesn't care how much CO2 is in the air. To him everything from climate change to the poisoning of his precious bodily fluids is a communist plot.

I have some numbers from biodiesel factories in Argentina. The energetic balance is positive aprox. 30% considering seeding, harvest, crushing, processing,... etc.It means that if 1 liter of biodiesel has 10.000 kcal, you have to spend 7.000 kcal in making it.
In another, way when you burn 1 liter of biodiesel in your car you may consider that you are burning 1,7 liters (more or less).With fossil fuel may be 1,15 depending on the well efficiency.
With the point of view of global warming fossil fuels may be better if the earth has enough plants to deal with CO2 (corn,soy... for food destination or forests like amazonian).
With the point of view of sustainable mobility neither of both are able with actual consumes. Consider next or existing peak oil and deforestation of jungles for biofuels.It´s not the same the carbon capture of an acre of forest than an acre of soy.

I would agree with Tom Deplume on this one, to a point. There would be charcoal left over after pyrolysis (a boon for Webber, lol).

However I can't imagine that so much waste in the form of charcoal exists and instead have to assume that the researchers were counting carbon fixation in the soil via roots in their calculations. If this was so, their calculations were erroneous as the roots would be broken down and metabolized aerobically (thus releasing C02).

According to the recent David Tillman study at the U of Minnesota mixed prairie grasses will sequester 1.8 tons per acre of carbon in the below ground parts. The carbon will continue to increase at that rate for an indefinate period of time, they think on the order of 100 years. Soil will hold huge amounts of carbon, in a very stable state, as evidenced by the "Terra Preta" studies done at Cornell. Also check the EPRIDA site for similar supporting information.

An answer to global climate change may be to sequester carbon this way since the biomass can still be harvested at a rate of 4 tons per acre or more.


Stan is only correct that CO2 quality is the same from fossil fuels or synthetic fuels made from biomass.

Timing is where Stan's argument goes astray.

A fossil fuel was made from CO2 CO2 from the atmosphere long ago. That has nothing to do with removing CO2 today.

In contrast, biomass growth removes CO2 today, tomorrow, and everyday.

If there is too much CO2 in the atmosphere which removal is of interest now - fossil or biomass?

The consumption of fuel, fossil or synthetic, fuel has nothing to do with CO2 removal. It concerns emission.

Linking emission and removal by happy talk, 'recycling', spawns confusion. Our concern is not about the life experiences of a CO2 molecule, it is about the CO2 quantity in the atmosphere.


Biological carbon sequestration was quite intensively researched some time ago. It was proved that it is way more efficient and cheap means to remove CO2 from atmosphere than any carbon tax, cup-and-trade, or any other fossil fuel conservation measure. Some plants have incredibly deep and massive root systems, which bury carbon deep into soil practically forever. Regular grapevine has it roots penetrate soil for twenty meters. I recall one DOE study (sorry, can not find it now) where it was demonstrated that conversion of part of Argentinean pampa to some particular shrub with massive roots growing down for more than 30 meters will permanently sequester more carbon than all world fossil fuel emissions combine – for couple of decades.

But of course, such measures are unacceptable. Too many peoples will lose their jobs if the problem will be solved.

Don't know Andrey...

"permanently sequester more carbon than all world fossil fuel emissions combine – for couple of decades."

Definitely a communist plot.

How can you get 115%. Let say you produce energy with biomass. You produce 100 gallons of biodiesel but trucking cost you 15 gallons. 85%

Now in the process of producing a coproduct that would require normally had a trucking and process heating cost of 30 gallons, your cogeneration process produces 100 gallons of biodiesel but trucking now only cost you 15 gallons. 115%

I have seen 800% when methane is captured and anaerobic bacteria produce nitrogen rich compost. Anaerobic digestion of dairy farm manure is an example.

I repeat "is not the same an acre of soy than an acre of trees".
Soy is one of the crops used for biodiesel. When soy is harvested little organic material remains in the surface and roots are very little also. Soy is well known as a soil degrader and could be tolerated in rotation with corn or others (and hard fertilization)just as a food provider but not for biofuels.
In a forest there are meters of roots for long term carbon sequestration and meters of branches and leaves in the surface acting as surface multipliers.

You can tell Kit P. is a troll, because he asked a question that had already been answered up-thread.

Either that, or he just plain doesn't read well.

I am neither a Holocoust nor climate "denier". But I certainly am a bovine excrement assertions denier.

I think the trace CO2 increase in the atmosphere is basically harmless, unless continued for a millenia or more. CO2 levels won't be increasing for millenia.

In the atmosphere, CO2 levels will be falling in absolute numbers in less than two decades. CO2 levels in the rest of the biosphere will continue to increase for a longer period.

None of the Cassandras ever heard of a curve more sophistiacated than a linear projection. All they can say is the trend line is up, and it will go up forever. Bovine passture patties!

On this blog if you cna't see the coming of the PHEV ands HEV vehicle, you are truly, truly blind. Adoption of the PHEV will decrease fossil fuel consumption by 60-70%. If you truly believe that the excess of man's CO2 is accumualting in the atmsophere I might agree with you.

But only until other balancing forces come into effect, with the lag appropriate to bring them back into balance. Meanwhile the coming sheer decrease in contribution will surely slow/stop the increase and start the decrease. An example of the balancing effects bringing it back into balance is the increase in the mass of the biota sequestering CO2 due to the fertilizing produced by higher CO2 levels.

To tranlate for simpleminded marxists waterrmelons, who took over the environmental movement, that means the reforestation of the world is happening. Go find some other scare factor to try to get you back into power. This scare won't work for much longer.

North America is now more heavily forested than anytime in the past century and the biota mass (forests) are still expanding.

Follow thew consequences of those conversions.

Yet none of the cassandra do at all. It would ruin theri scare.

I would agree that sometimes there is a bit too much scare-mongering on climate change in the media and in many respects I think global warming is/ should be irrelevant to the argument for renewable energy/ fuels and energy efficiency. However, if it increases people's awareness of alternative energy solutions, reduces the amount of wasted energy and improves their waste management in general, I'm happy to live with a little irritation.

It makes sense (and I'm not even talking environmentally here) to source energy/ fuels that are easily replenished (from a variety of inputs) and to make production clean, efficient and economically viable.

As with everything, there is bad science, groups with their own agenda and con artists, but I applaud the efforts and ingenuity researchers are showing to make renewables a reality. We're not there yet and I don't think there should be a "one size fits all" solution, but studies like this may help us gauge how efficient our fuel production can be and what reliance we should have on the different feedstocks used in fuel production - monocrops are not a good move.

As usual New Media Blogger Extraordinaire Engineer Poet tags the internet with his elitist know-it-all. The question Kit P attempted to answer hasn't been answered, but rather grasped at by the IQ-point destroying blithering of Internet Comment Proles.

And the real answer is: Certain biofuels displace 115% of the amount of fossil fuels used to produce them. TADA! New reduction (that would be the +15% over 100%) of atmospheric carbon. There, now stop asking silly questions as I only have enough IQ points left so as to be mildly brilliant.

Mark did provide a real answer, just not a very good one. To understand the benefits of co-products and soy beans sucking nitrogen out of the air, requires more than a simple example. Increased organics in the soil indicate billions of bacteria with a 20:1 C:N ratio gluing soil together to prevent soil erosion while reducing the amount of chemical fertilizer needed.

In the case of the 115%, I think that it means that you get a bonus above the inputs equal to 115% of the inputs. Therefore it could even go over 200%.

the kit will run in the neighborhood of 15K according to reports.

wow. whoops--i posted to the wrong page.

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