Phoenix Motorcars and UQM to Develop Plug-In Series Hybrid Sport Utility Truck
Maryland Governor Signs Clean Car Bill Adopting California Emissions Standards

USDA Research Suggests the Amount of Corn Stover Available for Ethanol Production Must Be Reduced to Preserve Soil Quality

The US Department of Agriculture’s Agricultural Research Service (USDA ARS) has undertaken a large-scale, five-year project to determine the amount of crop residues (e.g., corn stover, cover crop) that must remain on the land in order to maintain soil organic carbon (SOC) and sustain production.

The Renewable Energy Assessment Project (REAP), which began last year and runs through 2011, is conducting a series of experiments to estimate the amount of residue needed to maintain soil organic carbon and productivity. Focusing on factors including tillage and residue removal and conducted under several environments, these experiments will measure biomass production, grain yield, and change in soil organic carbon.

There are nine ARS locations participating in REAP in eight states, from Alabama to Indiana to Oregon.

Some initial results already suggest that twice as many cornstalks have to be left in the field to maintain soil organic matter levels, compared to the amount of stalks needed only to prevent erosion. In other words, when factoring in soil quality as well as erosion, the amount of biomass feedstock available for cellulosic ethanol production is cut in half.

As an example, a 213-bushel-per-acre corn yield leaves farmers an average four tons per acre of cornstalks after harvest. Farmers could then harvest about two tons of cornstalks per acre for conversion to ethanol—but only from land with low erosion risks, using little or no tillage. If the same farmers rotate with soybeans as recommended, they can only remove half again as much biomass for ethanol production, or just one ton per acre, to compensate for the lower biomass left by soybeans.

In determining the amount of crop residue required for the conservation of soil quality, REAP is:

  • Estimating the trade-off between the short-term economic return to growers who harvest crop residues as biofuel or biomass product feedstock versus the long-term benefits to soil, water, and air resources associated with retaining crop residues to build soil organic matter and sequester carbon.

  • Developing algorithms to guide the amount of crop residue that can be sustainably harvested as feedstock for biomass ethanol and bio-based products without degrading the soil resource, environmental quality, or productivity.

  • Developing management strategies (e.g., no tillage) supporting sustainable harvest of residue.




So there is no point in high yield cellulosic ethanol production if you wreck the soil in 5 years.

You will want to maintain the soil quality ad infinitum, which is a bit trickier.
Perhaps as the amount of CO2 in the atmosphere increases we will be able to take more of the stover out of the fields.
Or just find another crop for biomass and / or liquid fuel production.


Some folks at UCSD have figured out how to make syngas directly from the CO2 in the air. It's in a very early research phase, so who knows where the tech will end up on the economic scale.


Cervus: very interesting article ... have you brought it to Mike's attention?


Correct me if I am wrong--my knowledge is somewhat limited in this area--but if the stover was used as feedstock for a gasification system, would'nt there be nitrogen and carbon byproducts available to be applied to the fields?


Doubling the amount you leave on the field only halves the amount you take away if the amount left/taken is one/two thirds. I'd guess that only the amount left doubling is true.


Switchgrass makes more sense in the US for Butanol as does algae for biodiesel. Corn and ethanol are pure economical and ecological stupidity. It's a net loss for everyone except the democrat-liberal-leftist-socialist-communists (all really just the same) politicians.


Tim: back to PoliSci 10 you go. They aren't all same, they only seam that way to someone on the lunatic right. (but then the lunatic right never really liked democracy any more than communists). You can be center or left of center and still be smart enough to realize that corn ethanol is a bad joke. As I recall most of the States pushing ethanol are in the mid-west, an area that voted heavily republican in the last presidential election. However, if you are growing corn for food, you might as well use whatever percentage of the stover for fuel can be taken without degrading the soil.


The problem may be the technology, not the crop. If the stover was gasified some of the char could be returned to the soil or used to upgrade poor soil elsewhere. That is a faster cycle that ploughing-in stover or leaving it to rot on the surface. All the phosphorous will be in a closed loop though nitrogen may have to be added such as a legume rotation.


Back of the envelope calculation:
10 billion bushel annual corn crop
divide by 213, per above, 47 million ton of cornstalks.
divide by 4, per above, 11.8 million ton of cornstalks usable
1 ton feedstock = 89 gal ethanol per Iogen
11.8 million ton of cornstalks = 1 billion gal ethanol.


All they need is a decade of gm mods to the corn to both make it self ferilizing and make it produce more stover.. remembrt as a food crop stover was likely paired down alot. In the new gens we will likely see more leaves thicker stalks and taller stalks to increase yield maybe 500 percent.

Heck in 30 years the celulose corn may look more like a bushy tree then corn.. 25 foot tall 6 inch diamter stalks 4 foot long thick and wide leaves and little or no corn.


Soil is an eco-system, so it might be a more complex issue than simply maintaining a carbon / nitrogen balance in the soil.

Harvey D.

Growing plants to produce fuel for inefficient ICE vehicles may not be a long term worthwhile proposition.

Electric dominant PHEVs and pure BEVs would be better, regarless of how the electricity is produced. Of course, non or least polluting sources such as (hydro, solar, wind, waves, geothermal, etc) should be favoured.

Using fallow or harmful agricultural, forestry, industrial and domestic wastes to produce essential paints, plastics, textiles, related recyclable materials and (by exception) essential fuels may be justified and sustainable.

Robert Schwartz

Yet another reason to believe that deriving fuel from food crops is a bad idea.

Mark A

Harvey D has a firm grasp on the obvious!!

And Wintermane, how do you propose to make corn plants self fertilizing?? Self watering too? 500% increase? The corn would have to be 30 foot tall!! What kind of farm equipment do we have that could handle this sort of an increase??

A successful corn crop takes tremendous amounts of fertilizer, and very ample amounts of water. And modifying corn to produce more stover, and I have to assume, less "ear" is counter to what the corn industry has been developing over the last century and a half. (Sorta like taking fine piece of furniture and cutting it up to make a good pile of sawdust in that you are sacrificing the valuable portion of the corn plant to make extra corn "waste"!)

Back to the stover/residue issue. Farming requires a fine balance in reincorporating the "stover/residue" back into the soil to create humus. This humus also protects the soil from erosion for the other half of the year when corn cannot be grown. This humus also grabs, and helps retains soil moisture that would otherwise be lost at a much higher rate without this residue. A very fine balance is needed to grow corn, which is a hard crop to make a successful of, even when all the conditions are right. A Katrina type national disaster, or major drought, at the wrong time in the corns growing cycle spells the end of that crop. Cant just give it a do-over. It doesnt help that alot of our most productive croplands have become over-run by our urban sprawl, leaving the less productive to make up the difference. And yes, I have planted corn in my lifetime.

Growing crops to feed our fuel tanks, instead of our bellies, will NEVER be a good idea in my mind.


I agree with Harvey D , biofuels from crops aren´t sustainables in the way most people is thinking.
They will only be justified in a little percentage of available soil, just to have the fuel for the next harvest and strategic uses , in a closed circle that can secure food for next generations.
Personal transportation should be done from really renovable sources.


With some work they can make most plants do what clover does and thus make them fertilize the soil. As for 500 prtcrnt.. as you just said they spent 100 years reducing stover so gm can bring it back and then some rather fast.
As for the water... who knows what the new "corn" will need.. it will after all just be a titanic mutant grass.

Mark A

Clover has nitrogen fixing "nodes" which "fix" nitrogen into the soil. Will your "new" corn plant be a clover/corn hybrid? Can that be genetically modified "rather fast"? I wonder what the seed would look like, and whether our current farm equipment could plant it in the precise ways in which current corn seed is planted, as far as seed spacings and soil depths?

And can we reverse modify our corn genetics "rather fast" to undo what has taken 150 years to do? Also, when this corn gets hot, will it just sweat to create the water it needs? Could this be the Godzilla of corn plants, out of control?

I am sorry and dont mean to offend, but your comments are hilarious! It is risky to introduce new plants into a new environment. Witness the Japanese Kudzu plant in the Southeast US. It is now a major weed, in some cases growing over entire vehicles and houses. Google it. Its also risky to majorly modify our existing corn seed as used for our food. Cross pollinization across differing farms, over time, could wreck our current fragile food supply. Too risky in my mind.

Soil quality must be maintained in our cropland. Our farmers must be good stewards of our land, and not take more from it than it has to give. We cant survive another dust bowl like we had in the 1930's. We, as a society, are too weak compared to our ancestors of the 30's.


This is about what we estimated when reviewing the billion ton U.S. estimate. About 1/2 of the stover could be used with no till farming.

DS, I think you may be off by a factor of 10. It is more like 10 billion gallons per year from cellulose. If we need 15 billion gallons per year to get to E10, I would rather do it with cellulose from corn stover than from corn.


You forget some very basic math. If you transfer the plants energy from corn kernels to stalk and leaves and get a plant twice as tall and twice as woody and twiceas bushy and twice as wide you get 8-1600 percent more plant matter per plant. And yes they can BREED all those aspects.. or use gm to cheat it faster.

As for kudzu.. depending on its celulose content it might become a fuel crop as it sure doesnt need any vare at all. Hell mayve they will makr a cordzbean plant thats a combo corn soybean kudzu.. maybe add grapes and rises and mint to it to realy s[iff it up...

Charlie H.

This is one of the reasons I'm not too supportive of biofuels. Renewable: yes. Carbon nuetral: mostly. Not petro based: haray! But they deplete the soil, which makes it nonrenewable. unless crops were rotated..

Patty O



Very interesting read


Using alfalfa makes sense to me. It's a nitrogen-fixing legume and the leftovers can be used for glue, fodder, and paper. If we go PHEV (plug-in hybrid), most of our energy will come from the grid, necessitating less production of
bio-fuels, and leaving corn for Post Toasties and tortillas. 25% of our nitrogenous fertilizer is derived from Mideast oil, so I like the idea of using nitrogen-fixing legumes; however, switchgrass and miscanthus can be planted on marginal land and need little fertilizer.


The interesting part of switchgrass, other biomass gasification is that you can get hydrogen to make NH3 to make nitrogen fertilizer. So, you have a biomass plant that is an energy plant that is a fuels plant that also makes fertilizer to grow more biomass.


Miscangus [elephant grass] should also be examined as a corn rotation crop for preserving corn soil quality. Miscangus yields 1360 gallons cellulosic ethanol per acre compared to 400+ gals per acre for corn. Sure some stover should be retained but there's plenty of other cellulosic ethanol sources as well. We have to build more cellulosic ethanol energy plants.

The comments to this entry are closed.