Most farmers above a certain age probably received a dose of castor oil sometime in their early lives. From what I remember, we wished we could have poured it anywhere but down our throats.
Back then, dumping it in the fuel tank of a tractor or pickup truck would have been the last thing on our minds. But alternative fuel experts are beginning to ask if doing just that might help meet the nation's growing need for biofuels.
When you mention biodiesel, most people think of soybean or cottonseed oil or something less esoteric like chicken fat. If they're really into alternative fuels, they might list sunflowers or canola, crambe or flax or the oil from tung nuts or tallow trees. But castor oil?
“If you look at the state of Mississippi, soybeans are what we normally think of as oil for biodiesel,” says Herb Willcutt, Extension agricultural engineer with Mississippi State University. “But there are a number of vegetable and animal fats that have the potential to be used for biodiesel.”
Speaking at a meeting sponsored by the Chemical Producers and Distributors Association in Memphis, Tenn., Willcutt said all of these products yield varying amounts of oil that can be refined and mixed with petroleum diesel (B2, B5 or B20) or used as a standalone fuel.
One reason soybeans usually head the list is that they're relatively plentiful, accounting for about 50 percent of all the vegetable oils worldwide. Another is that soybean growers have been aggressively promoting the use of soy oil in biodiesel through the United Soybean Board and the American Soybean Association.
In general, a bushel of soybeans produces 10.7 pounds or 1.33 gallons of soy oil (compared to 47.5 pounds of meal). So a field that harvests 30 bushels an acre would yield about 40 gallons of soybean oil, depending on the method of extraction.
“They're telling us that out of 36.96 million bushels of soybeans from an average crop in Mississippi, we would expect to be able to get about 26 million gallons of soybean oil,” said Willcutt. “That's not all of the soybean oil going into biodiesel; that's the excess above the food demand that's there.”
He said studies show that if all of the soybean oil produced in the United States were used for biodiesel, it would meet about 12 percent of the U.S. trucking industry's fuel needs.
“Most cottonseed oil is converted into something else — cooking oil primarily,” he said. “Soybean oil would provide a shallow layer in a deep bucket when it comes to use as a motor fuel.”
The benefits of growing the demand for soybeans for biodiesel can't be discounted. “USDA marketing studies show that a 100-million-gallon increase in use could increase the price of soybeans about 10 cents per bushel,” Willcutt notes.
If the total U.S. soybean crop of about 3 billion bushels per year could be converted to biodiesel, it would produce roughly 4.2 billion gallons or 7.5 percent of U.S. yearly demand for diesel fuel.
The price of soy oil as a biodiesel feedstock ($1.85 per gallon on today's market) represents about 75 percent of the current cost of a gallon of biodiesel, according to Willcutt. Add to that 30 cents per gallon for processing, 20 cents for transportation and 15 cents for other, and “we're saying $2.40 to $2.50 to produce a gallon of 100 percent biodiesel.
“Think about how that compares with the cost of fuel at the pump? After you subtract all the taxes and tax rebates and so on, we're probably at break-even with off-road, on farm diesel at $2.30 to $2.40 per gallon.”
Willcutt says that anything that can be done to reduce the feedstock cost of the soy oil below $1.85 per gallon will help make biodiesel more competitive with petroleum diesel.
Using grant money from the federal government, Mississippi State has begun conducting research on a number of alternative crops, including winter annuals like canola, camelina, hesperis, black mustard, crambe and flax, summer annuals such as castor and sunflower and perennials such as tung and tallow trees.
The tallow tree can produce 12,500 pounds of nuts per acre with about 5,000 pounds or 40 percent of that being vegetable oil. The tung tree can yield 8,856 pounds of nuts and 1,770 pounds or about 20 percent oil.
Farmers can harvest about 1,600 pounds of canola per acre. With an oil content of 41.5 percent, that translates into about 111 gallons of vegetable oil. Camelina, black mustard, crambe and flax can also yield varying quantities of oil.
Castor has attracted the attention of MSU researchers because with its oil content at 50 percent and its relatively high crop yield of 1,695 pounds per acre, castor beans can supply up to 141 gallons of castor oil per acre. That compares to 50 to 60 gallons per acre for soybeans.
“Castor oil is a summer-grown crop that fits well in Mississippi and other parts of the southern United States,” says Willcutt. “The plants will produce 141 gallons of oil and about 131 gallons of biodiesel. You'll hear various comments about how much fuel you'll get. The rule of thumb is you're putting 10 percent methanol and sodium hydroxide into the process to make biodiesel and coming out with about 90 percent biodiesel after the glycerine is removed.”
He said the only downside of extracting oil from the castor bean is that the process leaves a white powdery substance called ricin, which is a potentially deadly toxin.