There was a time when farmers used every bit of a corn plant:

• Grain would feed the hogs.

• Cobs could fuel the kitchen stoves.

• Stalks could feed cattle or provide bedding.

That time may come again.

Ethanol producers are increasingly using corn stover to power their plants, and they're working on using the stover itself to make the fuel.

Now, agribusiness companies Monsanto Co., Archer Daniels Midland Co. and Deere and Co. see profits in stover and are collaborating on research into economical ways of harvesting, processing and using the stuff, including as substitutes for petro-chemicals.

"We're back to the future," said Darrin Ihnen, who farms near Sioux Falls, S.D. He provides stover to a Poet LLC ethanol plant for powering the facility and has started feeding some to his cattle instead of alfalfa.

Stover already is valuable to farmers because it adds organic matter to the soil, boosts fertility and protects the ground from erosion. But the amount of stover being left in fields each fall is growing as corn yields increase, and it makes sense for farmers to find a way to make money off of it, because some of it needs to be removed anyway, the companies said. A 200-bushel-per-acre corn crop, which is common today, produces 3.8 dry tons of stover an acre. The 300-bushel crops of the future will produce 4.7 dry tons of stover, according to Monsanto, the seed giant.

"We're trying to figure out ways to convert stover from a management cost into a source of assets," said Mike Edgerton, a Monsanto official who recently briefed a National Research Council panel on the research. If there's too much of the crop residue on the ground, seeds may not germinate properly, and Monsanto estimates farmers spend $15 to $30 managing the stover.

For Monsanto, finding farmers a market for stover will keep them planting corn. ADM, a corn processor, sees a business opportunity in converting the stover to biofuels, industrial chemicals and a feed that could replace some grain in cattle diets. Deere and Co. sees a market in the equipment needed to collect the stover.

"As yields increase, there's more stover out there and we can remove it," said Ihnen, who is president of the National Corn Growers Association. "It will be up to each individual farmer whether they want to (sell) it or not. Monsanto and ADM are not forcing us to sell stover. We'll react to the market just like we do with corn."

Poet is leading the ethanol industry in trying to commercialize the use of stover as a replacement for corn starch in making ethanol. Poet plans to use cobs to make ethanol at its Emmetsburg plant and has been working with farmers on methods to harvest the cobs.

In the meantime, many ethanol plants such as Poet's are starting to use stover for power, said Paul Gallagher, an economist at Iowa State University.

Two years ago, Monsanto, ADM and Deere started collecting stover from about a dozen farmers in Benton and Linn counties. Some of the stover was studied as a replacement for coal in a power plant and some was used for cattle bedding. After the bedding is soiled with manure, it's gathered and used to produce methane gas for generating electricity.

ADM has tested the stover as a fuel source in its Cedar Rapids corn processing plant. It also is processing stover into a cattle feed product and into petroleum chemicals used in making plastics.

ADM, long one of the largest producers of corn ethanol, is researching ways to either ferment stover into ethanol or to convert the crop residue thermochemically into conventional motor fuels, including gasoline.

Officials with the companies said a number of economic incentives drive their research:

• The cost to farmers of managing the residue.

• The prospect of higher oil prices.

• Federal biofuels policy, which requires the use of fuels not made from food crops and grades fuels based on their greenhouse gas emissions.

Using stover to power a corn ethanol plant gives it a better score in reducing greenhouse gas emissions. Congress could give the stover industry yet another push if it passes climate legislation that increases the cost of fossil fuels and forces utilities and factories to look for alternatives to coal.

Monsanto's research found that stover had about one-tenth the carbon emissions as coal and about one-fifth as much as natural gas. Stover is likely to be more expensive than coal, though Monsanto officials aren't revealing what the price difference is.

Leif Solheim, who oversees the research for ADM, says the new stover research uses are getting closer to profitability as the companies work to lower the production costs and oil prices rise. The idea is to "develop stover as a commodity crop," he said.

The question for farmers is how much they can make off the stover. An Iowa State University study estimated it would cost farmers at least $50 a ton to harvest and truck the stover to market.

Ihnen wouldn't disclose what Poet is paying him for his, but he estimates farmers would have to be paid $30 to $60 a ton to make it worth selling the stover. An extra ton an acre is how much Monsanto predicted farmers will have when yields reach 300 bushels an acre.

"Can I afford to leave $30 to $60 in the field?" he said. "It's definitely going to be another income source for a grower."

Mark Heckmann, who farms near West Liberty, has been following the stover research projects for the Iowa Corn Growers Association and said the possibilities are promising.

"Iowa is corn country," he said. "We're the No. 1 state. It behooves us to exhaust every possibility to utilize that corn stalk in the best manner."