Making ethanol from crops other than corn is more than a theory to Lee McClune. It's reality.
The Knoxville, IA, farmer and part-time engineer has worked for years to develop a harvesting machine and on-farm processing system that can convert sweet sorghum into ethanol. Now he's on the verge of launching his Sorganol system (originally featured in this magazine in November 2005).
“Our newly formed company has already built four harvesting machines, and all the other components of the system are nearly completed,” says its inventor. “We've also got lots of interest and an order for 10 harvesters, so once we get the final bugs worked out this fall, we'll move forward with manufacturing and marketing this winter.”
On-farm production is what makes this ethanol-making process unique. The Sor-Cane Harvester, with header and feed rolls similar to those of a forage chopper, cuts and presses the sorghum. That extracts its high-sugar juice, which is filtered and pumped into a storage tank behind the harvester. From there, the juice is transferred to a tank wagon or bladder, where bioagents are added and fermentation takes place.
Depending on the volume of juice in storage and air temperature, complete fermentation takes as little as two to three days, says Danielle Bellmer. The Oklahoma State University food and bioprocessing engineer worked with McClune to test the practicality of the on-farm concept. She thinks it will work.
“Once the juice is fermented, it is very stable and can sit in a sealed container for many months before it is distilled,” says Bellmer.
McClune is also building the final part of the system — a mobile biorefinery system.
“My original idea was to make a harvesting and storage system that was affordable for one farmer to own, and then he could potentially share a distilling unit with other growers,” he says. “Or he could contract to have the distillation done. Now there is so much interest in this concept that, depending on how many acres of the crop you planted, and especially if you staggered plantings, one farmer could justify owning a distillation unit.”
He estimates that his two-row harvester will cost about $75,000, while a 10,000- to 20,000-gallon storage bladder would run between $4,000 and $6,000. The capacity and cost of the distiller has yet to be determined.
But McClune says the process is profitable. “Figuring conservatively, with an ethanol yield of 800 gallons per acre from sweet sorghum, if you can market the ethanol at $2.40/gallon, that's $1,920/acre in revenues — more than double the payback that you could get from corn ethanol.”
Sweet sorghum is ideal for making ethanol because of its high sugar content, notes Bellmer. “You're starting out with liquid sugar.”
The catch, she says, is that you need to start the fermentation process within a day (ideally within hours) of harvesting the juice. “That's why the in-field process is critical to making the system work.”
The crop yields fairly consistently, she adds. “We've had very different types of growing conditions over the past three years, and sweet sorghum yields have stayed relatively stable. The crop seems to be drought-resistant.”
It's also been successfully grown in many parts of the country — from Florida, where as many as three cuttings can be taken, to Iowa, where McClune says his own trials show it can be harvested up to a month after a killing frost with little loss of juice yield or quality.
“The crop benefits from good fertility, but is not nearly as input-intensive as corn,” he says. “When it's planted following soybeans, you may not even need to apply much nitrogen. The crop requires a 60-60-60 fertilizer.”
There's a lot of juice to handle when harvesting — typically about 5,000-7,000 gallons/acre, which varies in sugar content from 17% to 21%. The sweet juice is converted to a solution of 10% ethanol. “That leaves you with a lot of leftover liquid with some nutritive value, but we still need to do analysis of it. I recommend farmers spray it on fields.”
McClune has even found uses for the fibrous plant material that comes out of the harvester. “It can be dried and burned to power the distiller unit, or it makes an excellent livestock feed — cattle love it.”
Because seed supply has been a limiting factor, McClune is working to be able to provide it to growers, as well. Currently, there are about eight varieties of sweet sorghum, available mostly from breeders at universities, including Mississippi State and Texas A&M, at a cost of $4-8/lb. But McClune's also working on a seed harvester that could be used prior to harvesting the juice.
“If you can save your own seed, that would make the whole system even more sustainable and practical,” he says.