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Researcher Investigates Tropical Maize as Biofuel Crop; “Sugarcane of the Midwest”

Early results from research by University of Illinois crop scientist Fred Below indicate that tropical maize—the form of corn grown in the tropics—may be an efficient biofuel crop for the US Midwest. Below began investigating maize in search of novel genes for the utilization of nitrogen fertilizer and was hoping to discover information that could be useful to American corn producers.

Maize requires few crop inputs such as nitrogen fertilizer. It also is easier for farmers to integrate into their current operations than some other dedicated energy crops because it can be easily rotated with corn or soybeans, and can be planted, cultivated and harvested with the same equipment that US farmers current utilize. Finally, tropical maize stalks are believed to require less processing than corn grain, corn stover, switchgrass, Miscanthus giganteus and the scores of other plants now being studied for biofuel production.

The long summer days in the Midwest delay flowering of tropical maize, according to Below, which causes the plant to grow very tall—14 or 15 feet tall compared to the 7-1/2 feet height of conventional corn—and produce few or no ears. Without ears, these plants concentrate sugars in their stalks, resulting in 25% or more sugar in the stalks in the forms of sucrose, fructose and glucose than corn.

This differs from conventional corn and other crops being grown for biofuels in that the starch found in corn grain and the cellulose in switchgrass, corn stover and other biofuel crops must be treated with enzymes to convert them into sugars that can be then fermented into alcohols such as ethanol. Storing simple sugars also is more cost-effective for the plant, because it takes a lot of energy to make the complex starches, proteins, and oils present in corn grain. This energy savings per plant could result in more total energy per acre with topical maize, since it produces no grain.

Below said that his early trials also show that tropical maize requires much less nitrogen fertilizer than conventional corn, and that the stalks actually accumulate more sugar when less nitrogen is available. Nitrogen fertilizer is one of major costs of growing corn.

The sugarcane used in Brazil to make ethanol is desirable for the same reason: it produces lots of sugar without a high requirement for nitrogen fertilizer, and this sugar can be fermented to alcohol without the middle steps required by high-starch and cellulosic crops. But sugarcane can’t be grown in the Midwest.

Growing tropical maize doesn’t break the farmers’ rotation. You can grow tropical maize for one year and then go back to conventional corn or soybeans in subsequent years. Miscanthus, on the other hand, is thought to need a three-year growth cycle between initial planting and harvest and then your land is in Miscanthus. To return to planting corn or soybean necessitates removing the Miscanthus rhizomes.

—Fred Below

Below is studying topical maize along with doctoral candidate Mike Vincent and postdoctoral research associate Matias Ruffo, and in conjunction with U of I Associate Professor Stephen Moose. This latest discovery of high sugar yields from tropical maize became apparent through cooperative work between Below and Moose to characterize genetic variation in response to nitrogen fertilizers.

Currently supported by the National Science Foundation, these studies are a key element to developing maize hybrids with improved nitrogen use efficiency. Both Below and Moose are members of Illinois Maize Breeding and Genetics Laboratory, which has a long history of conducting research that identifies new uses for the maize crop.

Moose now directs the longest-running plant genetics experiment in the world, in which more than a century of selective breeding has been applied to alter carbon and nitrogen accumulation in the maize plant. Continued collaboration between Below and Moose will investigate whether materials from these long term selection experiments will further enhance sugar yields from tropical maize.

In terms of biofuel production, tropical maize could be considered the Sugarcane of the Midwest. The tropical maize we’re growing here at the University of Illinois is very lush, very tall, and very full of sugar.

—Fred Below


fred schumacher

Plant phenology is primarily tied to growing degree days. It's total accumulated heat that determines what growth stage the plant is in. That's the phenomenon this study taps into. Take a a tropical plant and move it toward higher latitudes and it will grow taller because of longer daylength in summer and will not go into sexual reproduction because total absorbed ambient heat is too low.

The same trick works well with switchgrass, which is a very winter hardy warm-season (C4 photosynthesis pathway) perennial. Move a cultivar north and it will not invest energy into seed production (the part of plant biology that requires high fertility levels) and will grow a tremendous amount of stalk.

This is what REAP-Canada discovered in their trials in Quebec. The greatest biomass producing cultivar was Cave-in-Rock, which has a southern Illinois point of origin. The lowest producer was Dacotah, a northern, North Dakota origin selection.

Rafael Seidl

@ Fred Schumacher -

if I understand you correctly, the implication is that the introduction of tropical maize is unlikely to result in inadvertent cross-breeding.

My only question is why this variety of maize has not been considered before. After all, corn has been the primary ethanol feedstock in the US for many years, though demand has admittedly skyrocketed in response to the EPA withdrawing its legal cover for MTBE last year.


Does this mean that midwestern farmers could theoretically produce feedstock for the production of table-grade suger? Is the mix of sugars in the stalks similar to the mix in cane sugar or beet suger? That could increase sugar supplies and possibly cut costs in the U.S. This is getting off the subject of automobiles, but I rather detest high fructose corn syrup, and would be very happy to see the re-substitution of real sugar into more of our commercial food products.


NBK - Like you I detest the fact that high-fructose corn syrup is in our food supply. I am convinced it should be banned. Use it to make fuel.

The price of sugar is supported in the US. If it were not it would be about 10% of it's current price.

Paul Dietz

Like you I detest the fact that high-fructose corn syrup is in our food supply.



Frankly, I think high fructose corn syrup makes Coke -- among other things -- taste bad. I've had Coke made with real sugar, and I think it's much better. It's available in parts of Europe, as well as in major U.S. cities around the Jewish holiday of Passover -- many observant Jews will not consume corn products on that holiday, and Coke puts out a line of sugar-based sodas every spring to attract their business.

Others also think that high fructose corn syrup is more unhealthy than table sugar, because it contains a different mix of sugar molecules than table sugar usually does. Basically, high fructose corn syrup is a roughly even mix of glucose and fructose, while cane sugar is mostly sucrose. I'm not sure of the soundness of these health claims, and make my point only on the issue of taste.

Paul Dietz

Basically, high fructose corn syrup is a roughly even mix of glucose and fructose, while cane sugar is mostly sucrose. I'm not sure of the soundness of these health claims, [...]

Sucrose is a dimer of fructose and glucose, and is hydrolyzed in the stomach into those two simple sugars. So the claims are rather dubious, and you are right to doubt them.


Paul - I take the totally unproven position that HFCS is responsible for the marked increase in Autism in our society. There is a direct parallel with it's introduction.

Take an open mind into a google search on it and see if you still feel the same.

Paul Dietz

Luces: so, your position is that if the sucrose had been substituted for HFCS in drinks, etc., the increase in autism would not have occured? Despite the fact that after digestion they are almost chemically identical (minor difference in the fructose/glucose ratio)? 'Preposterous' is the word that springs to my mind.

Rafael Seidl

@ Lucas -

a correlation, assuming there is one, does not represent causality. You'd have to eliminate an awful lot of confounding factors to substantiate your hunch.

What is true is that HFCS is a cheap ingredient that adds a lot of empty calories. Refined sugar is at least as bad in terms of nutrition but it costs more. Many consumers try to minimize their food budget, apparently so they can afford a bigger, thirstier car that can better accomodate their ever-expanding girth.

Ergo, the issue isn't junk food per se, it's wrong-headed consumer priorities and even more wrong-headed government subsidies for domestic corn and sugar producers plus trainee programs at fast food chains. But you won't find a single politician making that case in an election year. Or in any other year, for that matter.

Corn syrup is produced by fermenting corn starch into pure glucose. High fructose corn syrup is a mix of 30-60% fructose (produced by fermentation of corn glucose into fructose) and regular corn syrup, and has around the same nutritional qualities as table sugar. There are differences: it tastes different than table sugar, it helps the food to retain moisture, and the main difference: sucrose is broken down into fructose and glucose by the enzyme sucrase, by which the body regulates the rate of sucrose breakdown. Without this regulation mechanism, the body has less control over the rate of sugar absorption into the bloodstream.

Generally, bad reputation of corn syrup is undeserved. It is questionable fashion of American food producers to sweeten processed food to very high level, and habit of drinking sugared soft drinks and juices instead of water which overload our diet with unnecessary sweet calories.


Sugars in sugar cane, sugar beet, and tropical maize should be processed immediately upon harvest, other vice sugar content deteriorates very quickly and harvest begin to rot. In tropical climate of Brazil sugar cane is harvested all year round, but in temperate climate both tropical maize and sugar beets are harvested seasonally, and should be processed immediately. This is the reasons why beet sugar factories are working in highly intermittent cycle, and can not compete in open market with sugar cane.

For biofuel production purposes corn grain has very serious advantages: grain is dry granulated concentrate of starch (around 60%), protein, and oil. It could be conveniently handled, stored for years, cheaply transported to great distances. Corn ethanol plants could work all year round on single harvest of corn grain collected thousand miles from the plant. Tropical maize does not have such advantage.


Sorry, last post was mine.

fred schumacher

In northern sugar beet production areas, like North Dakota and Minnesota, sugar beet harvest is closely regulated to meet plant production capacity, while the weather is warm. Once normal night time frosts set in, all the beets are harvested and allowed to freeze in huge, aerated piles (called "beet dumps"). Northern climates have the advantage of freezing crops for storage prior to processing.

Regarding cross-polination of tropical maize -- my father-in-law once brought back some corn kernels from Guatemala. He planted them in his North Dakota garden. The stalks grew 12 feet tall and tassled, but did not pollinate nor make cobs. The same plants grew 3 to 4 feet tall in their native Guatemala and produced cobs.


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