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Adding fuel to growing sorghum for ethanol

Driven by rising ethanol production and Canada’s status as a net importer of corn, industry researchers are stepping up efforts to find an additional feedstock for the biofuels market.

Among the potential candidates is sorghum. Primarily grown for silage, forage and sugar production, sorghum is often cited as a promising crop because it costs less to grow than corn and it can thrive in conditions that are less than ideal for good corn production.

Besides being used for food and feed consumption, more sorghum is being used in various ethanol production methods in the US.  Similar to corn, the starch from grain sorghum, also known as milo, is converted by enzymes into sugar, which is fermented to produce alcohol. Another method uses the sugar from the stalks of sweet sorghum.

“It’s like sugar cane; there is juice in the stem, and if you extract this juice and ferment the sugar, it can be made into ethanol,” says Om Dangi, chief executive officer of Agriculture Environmental Renewal Canada (AERC). The Ottawa-based company specializes in the development of sorghum hybrids for both grain and silage. The research program, started by Dangi in 1994, has developed hybrids to grow in Eastern Canada’s climate. He says sorghum can be grown easily from Thunder Bay, Ontario, to Quebec City.

One area that has been touted for sorghum production is Ontario’s tobacco belt in southwestern Ontario. Jim Todd, transition crop specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs, says the sandy soils in the region are capable of growing a great corn crop if there is adequate rainfall. “But when it gets dry and hot, it isn’t an ideal location. Sorghum requires 30 percent less water than corn to sustain the same amount of dry matter,” explains Todd, noting that sorghum also needs 30 percent less fertilizer than corn.

Economics still trump interest
Although sorghum has demonstrated its agronomic potential, GreenField Ethanol, Canada’s leading manufacturer of the biofuel, has run tests to determine if the crop can be profitable for ethanol production. Mark Schwartz, business development manager in GreenField’s engineering technology group, says their interest is not about replacing corn but about supplementing it with another source. “We’re looking at an additional crop or feedstock, mainly from areas where they do not grow corn to any extent, so that we can make more ethanol. That’s the main thing.”

Schwartz says GreenField was approached by AERC to study the potential of one of its grain sorghum hybrids in conjunction with corn at its plant in Tiverton, Ontario. For Greenfield, the main objective was to determine how sorghum would affect its core business. “We wanted to see two things: how much ethanol we could get out of the grain versus the corn, and what the DDGs (dried distillers grain) looked like.”

The tests revealed that the sorghum produced eight to 10 percent less ethanol than corn. In its favour, Schwartz says the sorghum fermented well and produced a quality, gluten-free ethanol, which would be good for beverage ethanol. He also says the DDGs had a high protein level and good palatability. 

As for grain sorhgum’s potential as an additional feedstock for ethanol, Schwarz says it would have to be contracted at a discount to corn to compensate for the lower yield and excess production cost. “It made good ethanol, just less than corn. Based on the last trial, we could bring sorghum into Tiverton if they could provide it in a structured way that would be 10 percent less than the cost of corn.”

Whereas GreenField has been testing grain sorghum, other research involves sweet sorghum, which produces a sugar-rich juice that can be easily converted into ethanol. North Americans may be familiar with sweet sorghum’s syrup or “molasses”, but China and India have been leaders in producing ethanol from the crop. The simplicity of converting sweet sorghum to biofuel also creates the biggest constraint for using this method in Canada. Jim Todd says the main challenge becomes handling the crop after harvest because the sugar has to be fermented immediately. “It’s a good crop for ethanol production, but if you can’t reduce the amount of fermentation that occurs from wild yeast that is around before you get it to the ethanol plant, then the quality of the feedstock is reduced.”

Another limitation is that only one crop can be grown in a year, thus restricting the year-round feedstock supply to an ethanol plant. One solution is to process the juice on the farm. Sorghum growers in the US are studying this application and have designed harvesting equipment that squeezes the sorghum stems on the farm. The juice would then be allowed to ferment in tanks in the field. The next step involves reducing the amount of water, by boiling or filtration, to make transporting the material more economical.

Other challenges to overcome
Searching for ways to reduce the costs of handling sweet sorghum is just one hurdle. Dangi says the concept of farmers processing it in the field raises another potential challenge. In this scenario, farmers would be producing alcohol at the farm gate, which Dangi says is not permitted. There would also be questions about on-farm processing and how that would affect property tax assessments.

The emerging biomass sector is another possibility for the crop. Dangi says that sorghum could be fed into a bio-digester at an ethanol plant. Once the crop has been pressed to remove the sugar-rich juice, the leftover plant material could be fed into an anaerobic digester to produce methane-containing biogas that could be converted into electricity. Such a method would require private-sector involvement to develop the technology as well as sorghum hybrids for that purpose.

Although sorghum’s role in the future of Canada’s ethanol industry appears to be uncertain, the drive to find more cost-effective and additional feedstocks will continue as the industry strives to become less dependent on corn-based ethanol. “I was an advocate for sorghum grain because Ontario is a net importer of corn, and you have a lot of corn grown in certain areas,” says Schwartz. “So if you grow another grain, that is good for everybody’s business.”

November 30, 1999  By Blair Andrews


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