John Deere is working on an 8R tractor that mounts its reliable 9.0-liter engine but that is powered by E98 ethanol instead of diesel. Deere said the prototype ethanol engine has torque like its diesel cousin. And the ethanol-powered engine also eliminates the need for DEF.

For corn farmers who have put forward their crop since the late 1970s as ethanol additive for gasolines, ethanol-powered farming equipment gives them a new message: "Not only do we grow it. We also use it."

The diesel version of the 8R tractor is already a top seller for Deere.

"This is a standard 8R platform. But what we've done is we've taken the current 9-liter engine that we use in every 8000 series tractor and we've converted it over to ethanol," said Harold (Buddy) Kavalier, ethanol champion, large tractor engine research strategist at John Deere Power Systems. "To my knowledge, it's one of the first -- if certainly not the first -- heavy-duty, ethanol-powered engine in the market, on a high-horsepower perspective. Some of the older tractors would run on alcohol or be capable of running ethanol, but not at this power level."

This E98 8R prototype mounts a 350-horsepower spark-ignited engine and is said by Deere to have similar power characteristics in the field as its diesel equivalent. And because of ethanol's lower emissions compared to diesel, the engine does not require DEF.

"The customers we've had run this, when they get out of it, they were shocked. It was not what they expected they were going to see in terms of performance," Kavalier said. "The bottom-end (torque) would be a little different than the diesel. But it doesn't take far into the power curve, (that this engine) compares quickly with the diesel (tractor). And the customers that we've had run it, they're like, 'At the bottom end, it is a bit more challenged. (But) we're never going to run down there anyways.' So, I think for a lot of customers, this will work great, and they can eliminate diesel exhaust fluid (and) source fuel more cheaply."

Deere has long been a proponent of renewable fuels. It renewed its intention to pursue renewable fuels during a keynote presentation at the 2023 CES in Las Vegas. Deere's work builds on other work to adapt compression-ignition engines for high-ethanol blends.

Deere is gradually making its work known. It put a few of its E98 tractors into the field last year in Illinois and Iowa, and then also in Brazil. Deere displayed its E98 8R last spring at the large Agrishow in Brazil and just last week at the Commodity Classic in San Antonio, Texas.

The E98 has demonstrated good qualities under load like a tillage tool hitting heavy soils or from grain wagons that go from empty to full in a short time.

"We logged a number of hours on (the E98 8Rs) last fall with three different customers, and we never really had any major issues. There were a few things that we're still working, but in general, the tractor performed. We had no downtime, is what I'll tell you," Kavalier said.

Deere will be putting additional units into the field this year. But it has not announced an initial commercial production date. That is likely to be some time off. Deere has given its E98 8Rs program a tagline, of sorts. Signage around the tractor at the Classic proclaimed "Homegrown Horsepower" to the crowds.

"We're a little early," Kavalier said. "Normally, we wouldn't show a tractor like this for a number of additional years. But the reason we're showing this is to get that market feedback early from customers. If this is something that they're interested in, we can chase it."

E98 is typically a fuel used in performance racing and motorsports. It is blended with a 2% denaturant, often gasoline. It is not the ethanol used to produce E10 or E15 blends. There are no government statistics on how much E98 is produced annually in the U.S., but one source estimated that it would be in the lower millions of gallons annually.

For agriculture uses, E98 requires mechanical adaptations -- timing and turbocharging to push the pistons down with more force, and injectors and pumps to deliver high ethanol flows to sustain torque.

"The (9L) is one of the great engines out there for reliability and durability. So that's why we started with a 9-liter," Kavalier said. "From a building block standpoint, it's mainly the cylinder head deck on up is where things change. Different air system. Different fuel system. We've got spark plugs and plug wires. Of course, some of those parts will be maintenance components, and that's something we've got to still work our way through."

There are other considerations:

-- Cold starts. In colder climates, it is more difficult for higher-concentration ethanol to vaporize. "There were some cold start challenges initially. I would say we're feeling like we're over the hump on a lot of that," Kavalier said. Flexible-fuel cars capable of burning E85 fuels have sensors that detect ethanol content and adjust fuel delivery. In cold weather, engine control units (ECU) provide a more highly enriched fuel.

-- Compression. Ethanol's high-octane rating allows for high compression without "knocking." But there are challenges in designing an engine that balances high pressure with durability.

-- Lubricity. Diesel acts as a natural lubricant. Ethanol has almost no lubricating properties. Ethanol also attracts moisture and can be corrosive to some rubbers, plastics and some metals. But this is an issue not new to industry at all. There are chemical formulations, additives and coatings to manage ethanol's less-desirable characteristics.

On a BTU basis, ethanol and diesel differ.

"The ratio is about 1 to 1.72. So, for every gallon of diesel, you need about 1.72 gallons of ethanol, roughly, on a BTU count," Kavalier said. "But what I would note, we can get the 1.72 gallons (of ethanol) cheaper than 1 gallon of diesel. I would put that in the range of between 15% and 30% to be transparent. We're working on that in the marketplace, trying to make sure that we thoroughly understand. But we already have that source fuel. We've sourced fuel cheaper. It'll certainly be cheaper in the Corn Belt, but we think there's opportunities to do it in other places."

The characteristics of ethanol also raise logistical challenges. Deere acknowledges that. It is working with the National Corn Growers Association, Iowa Corn Growers and with E98 producers (few ethanol producers produce E98), even manufacturers of fuel trailers.

There are questions about transport. As ethanol looks a little more like gasoline to regulators, the U.S. Department of Transportation may have some say in how that transportation is conducted.

Ethanol requires new storage practices on the farm. E98 can be stored in a single-wall tank, but with a pump that can handle the corrosive effect of the fuel. Storage containers cannot contain materials such as zinc, brass, lead and copper. Rubber and cork fittings must be considered. Tanks and lines should be constructed from stainless steel and polypropylene, which is resistant to the corrosive effects of ethanol.

A consideration is the storage tank itself. Pouring E98 into used tanks raises the risks of fuel contamination. And because 1.7 gallons of ethanol equals the energy output of 1 gallon of diesel, storage systems may have to be larger -- also a consideration in fuel transport to the field.

Dan Miller can be reached at dan.miller@dtn.com

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