Weaning cars and trucks off of gasoline and diesel made from fossil fuels is a difficult task. One promising solution involves biodiesel, which comes from natural oils and fats, but it is costly. Using a microwave and catalyst-coated beads, scientists have devised a new way to convert waste cooking oil into biodiesel that could make it more affordable.
They report how they did it in ACS’ journal Energy & Fuels.
Biodiesel has many advantages over traditional fuels. It is renewable, biodegradable and emits less carbon dioxide. It can also easily take the place of conventional diesel without the need for carmakers to modify engines. However, producing biodiesel at a low cost remains a challenge. Waste cooking oil is currently the most appealing source because it doesn’t compete with the demand for virgin cooking oil. However, the process to convert it to fuel is complicated and expensive. Aharon Gedanken and colleagues wanted to find a simpler and less expensive method.
The researchers developed silica beads coated with a catalyst and added them to waste cooking oil. Then, they zapped the mixture with a modified microwave oven to spur the reaction of the beads with cooking oil. In just 10 seconds, nearly 100 percent of the oil was converted to fuel. The researchers could also easily recover the beads and reuse them at least 10 times with similar results.
- Today most U.S. biodiesel is produced from soybean. But despite its value as a protein source, soybean only provides the equivalent of about one barrel of oil per acre.
- A team led by the University of Illinois has engineered sugarcane plants to produce 12 percent oil by weight, and expect to reach 20 percent in the future. This could provide 17 barrels of oil per acre.
- Biodiesel from “oil cane” could reduce the cost of biodiesel production from $4.10 to $2.20 per gallon and provide additional environmental and economic benefits.
America’s oil consumption far exceeds that of every other country in the world. What’s more, it’s unsustainable.
Therefore, in 2007, Congress mandated a move away from petroleum-based oils toward more renewable sources. Soybeans, an important dietary protein and the current primary source of plant-based oils used for biodiesel production, only yield about one barrel per acre. At this rate, the soybean crop could never quench the nation’s thirst for oil.
To address this issue, the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) program called for high-risk, high-reward projects that could develop new drop-in fuels in its PETRO program. A team led by University of Illinois researchers answered the call by imagining and successfully achieving a way to produce large quantities of oil from sugarcane. Their most recent study demonstrates the economic benefits of this technology relative to soybean oil.
“We thought that if we could go back to the drawing board, we’d need a very productive crop. And we would also need something that could grow on land that isn’t being used intensively for food. We came up with sugarcane and sweet sorghum,” recalls Stephen P. Long, U of I crop scientist and lead investigator on the project.
The team altered sugarcane metabolism to convert sugars into lipids, or oils, which could be used to produce biodiesel. The natural makeup of sugarcane is typically only about 0.05 percent oil. Within a year of starting the project, the team was able to boost oil production 20 times, to approximately 1 percent. At the time of this writing, the so-called “oil-cane” plants are producing 12 percent oil. The ultimate goal is to achieve 20 percent. Oil cane has additional advantages that have been engineered by the team. These include increased cold tolerance and more efficient photosynthesis, which leads to greater biomass production and even more oil.
“If all of the energy that goes into producing sugar instead goes into oil, then you could get 17 to 20 barrels of oil per acre,” Long explains. “A crop like this could be producing biodiesel at a very competitive price, and could represent a perpetual source of oil and a very significant offset to greenhouse gas emissions, as well.”
In their analysis, the team looked at the land area, technology, and costs required for processing oil-cane biomass into biodiesel under a variety of oil production scenarios, from 2 percent oil in the plant to 20 percent. These numbers were compared with normal sugarcane, which can be used to produce ethanol, and soybean.
An advantage of oil cane is that leftover sugars in the plant can be converted to ethanol, providing two fuel sources in one.
“Modern sugarcane mills in Brazil shared with us all of their information on energy inputs, costs, and machinery. Then we looked at the U.S. corn ethanol industry, and how they separated the corn oil. Everything we used is existing technology, so that gave us a lot of security on our estimates,” Long says.
The analysis showed that oil cane with 20 percent oil in the stem, grown on under-utilized acres in the southeastern United States, could replace more than two-thirds of the country’s use of diesel and jet fuel. This represents a much greater proportion than could be supplied by soybean, even if the entire crop went to biodiesel production. Furthermore, oil cane could achieve this level of productivity on a fraction of the land area that would be needed for crops like soybean and canola, and it could do so on land considered unusable for food crop production.
The current full production cost of biodiesel from soybean is $4.10 per gallon ($1.08 per liter). Using oil cane instead, that cost decreases to $3.30 per gallon for 2 percent oil cane and to $2.20 per gallon for 20 percent oil cane. The ethanol produced from 1-, 5- and 10 percent oil cane would add to the cost benefit.
Although $2.20 per gallon does not represent a large savings over the current price of gasoline in the United States, Long cautions consumers and politicians to look at the bigger picture.
“We know from our past experience that it’s not going to last,” he says. “We need to start building for a future when gas is no longer as low as $1.50 per gallon, and we need to avoid any future dependency on other countries for our oil. We are lucky to have the land resources to do this and, in doing so, to ensure that future generations have a supply of oil that is domestic and renewable.”
The U.S. Department of Energy’s Ames Laboratory has created a faster, cleaner biofuel refining technology that not only combines processes, it uses widely available materials to reduce costs.
Ames Laboratory scientists have developed a nanoparticle that is able to perform two processing functions at once for the production of green diesel, an alternative fuel created from the hydrogenation of oils from renewable feedstocks like algae.
The method is a departure from the established process of producing biodiesel, which is accomplished by reacting fats and oils with alcohols.
“Conventionally, when you are producing biodiesel from a feedstock that is rich in free fatty acids like microalgae oil, you must first separate the fatty acids that can ruin the effectiveness of the catalyst, and then you can perform the catalytic reactions that produce the fuel,” said Ames Lab scientist Igor Slowing. “By designing multifunctional nanoparticles and focusing on green diesel rather than biodiesel, we can combine multiple processes into one that is faster and cleaner.” Contrary to biodiesel, green diesel is produced by hydrogenation of fats and oils, and its chemical composition is very similar to that of petroleum-based diesel. Green diesel has many advantages over biodiesel, like being more stable and having a higher energy density.
An Ames Lab research group, which included Slowing, Kapil Kandel, Conerd Frederickson, Erica A. Smith, and Young-Jin Lee, first saw success using bi-functionalized mesostructured nanoparticles. These ordered porous particles contain amine groups that capture free fatty acids and nickel nanoparticles that catalyze the conversion of the acids into green diesel. Nickel has been researched widely in the scientific community because it is approximately 2000 times less expensive as an alternative to noble metals traditionally used in fatty acid hydrogenation, like platinum or palladium.
Creating a bi-functional nanoparticle also improved the resulting green diesel. Using nickel for the fuel conversion alone, the process resulted in too strong of a reaction, with hydrocarbon chains that had broken down. The process, called “cracking,” created a product that held less potential as a fuel.
“A very interesting thing happened when we added the component responsible for the sequestration of the fatty acids,” said Slowing. “We no longer saw the cracking of molecules. So the result is a better catalyst that produces a hydrocarbon that looks much more like diesel. “
“It also leaves the other components of the oil behind, valuable molecules that have potential uses for the pharmaceutical and food industries,” said Slowing.
But Slowing, along with Kapil Kandel, James W. Anderegg, Nicholas C. Nelson, and Umesh Chaudhary, took the process further by using iron as the catalyst. Iron is 100 times cheaper than nickel. Using iron improved the end product even further, giving a faster conversion and also reducing the loss of CO2 in the process.
“As part of the mission of the DOE, we are focused on researching the fundamental science necessary to create the process; but the resulting technology should in principle be scalable for industry,” he said.