"Plastic shopping bags make a fine diesel fuel"
2014-02-12 by Diana Yates, Life Sciences Editor for the University of Illinois Public Affairs News Bureau
Brajendra Kumar Sharma (center) a senior research scientist at the Illinois Sustainable Technology Center at the U. of I., with research chemist Dheeptha Murali (left) and process chemist Jennifer Deluhery, converted plastic shopping bags into diesel fuel. Image courtesy L. Brian Stauffer.
Plastic shopping bags, an abundant source of litter on land and at sea, can be converted into diesel, natural gas and other useful petroleum products, researchers report.
The conversion produces significantly more energy than it requires and results in transportation fuels - diesel, for example - that can be blended with existing ultra-low-sulfur diesels and biodiesels. Other products, such as natural gas, naphtha (a solvent), gasoline, waxes and lubricating oils such as engine oil and hydraulic oil also can be obtained from shopping bags.
There are other advantages to the approach, which involves heating the bags in an oxygen-free chamber, a process called pyrolysis, said Brajendra Kumar Sharma, a senior research scientist at the Illinois Sustainable Technology Center who led the research. The ISTC is a division of the Prairie Research Institute at the University of Illinois.
"You can get only 50 to 55 percent fuel from the distillation of petroleum crude oil," Sharma said. "But since this plastic is made from petroleum in the first place, we can recover almost 80 percent fuel from it through distillation."
Americans throw away about 100 billion plastic shopping bags each year, according to the Worldwatch Institute. The U.S. Environmental Protection Agency reports that only about 13 percent are recycled. The rest of the bags end up in landfills or escape to the wild, blowing across the landscape and entering waterways.
Plastic bags make up a sizeable portion of the plastic debris in giant ocean garbage patches that are killing wildlife and littering beaches. Plastic bags "have been detected as far north and south as the poles," the researchers wrote.
"Over a period of time, this material starts breaking into tiny pieces, and is ingested along with plankton by aquatic animals," Sharma said. Fish, birds, ocean mammals and other creatures have been found with a lot of plastic particles in their guts.
Whole shopping bags also threaten wildlife, Sharma said.
"Turtles, for example, think that the plastic grocery bags are jellyfish and they try to eat them," he said. Other creatures become entangled in the bags.
Previous studies have used pyrolysis to convert plastic bags into crude oil. Sharma's team took the research further, however, by fractionating the crude oil into different petroleum products and testing the diesel fractions to see if they complied with national standards for ultra-low-sulfur diesel and biodiesel fuels.
"A mixture of two distillate fractions, providing an equivalent of U.S. diesel #2, met all of the specifications" required of other diesel fuels in use today - after addition of an antioxidant, Sharma said.
"This diesel mixture had an equivalent energy content, a higher cetane number (a measure of the combustion quality of diesel requiring compression ignition) and better lubricity than ultra-low-sulfur diesel," he said.
The researchers were able to blend up to 30 percent of their plastic-derived diesel into regular diesel, "and found no compatibility problems with biodiesel," Sharma said.
"It's perfect," he said. "We can just use it as a drop-in fuel in the ultra-low-sulfur diesel without the need for any changes."
The research team also included Bryan Moser, Karl Vermillion and Kenneth Doll, of the USDA National Center for Agricultural Utilization Research, in Peoria, Ill.; and Nandakishore Rajagopalan, of the ISTC at the U. of I. A report of the new study appears in the journal Fuel Processing Technology. The paper, "Production, Characterization and Fuel Properties of Alternative Diesel Fuel From Pyrolysis of Waste Plastic Grocery Bags," is available online here [http://www.sciencedirect.com/science/article/pii/S0378382014000290].
"Put a plastic bag in your tank"
2014-01-27 from [http://www.sciencedaily.com/releases/2014/01/140127122831.htm]:
Achyut Kumar Panda, Raghubansh Kumar Singh. Thermo-catalytic degradation of low density polyethylene to liquid fuel over kaolin catalyst. International Journal of Environment and Waste Management, 2014; 13 (1): 104 DOI: 10.1504/IJEWM.2014.058803---
Researchers in India have developed a relatively low-temperature process to convert certain kinds of plastic waste into liquid fuel as a way to re-use discarded plastic bags and other products. They report full details next month in the International Journal of Environment and Waste Management.
Many pundits describe the present time as the "plastic age" for good reason and as such we generate a lot plastic waste. Among that waste is the common polymer, low-density polyethylene (LDPE), which is used to make many types of container, medical and laboratory equipment, computer components and, of course, plastic bags.
Recycling initiatives are in place in many parts of the world, but much of the polyethylene waste ends up in landfill, dispersed in the environment or in the sea.
Chemist Achyut Kumar Panda of Centurion University of Technology and Management Odisha, India is working with chemical engineer Raghubansh Kumar Singh of the National Institute of Technology, Orissa, India, to develop a commercially viable technology for efficiently rendering LDPE into a liquid fuel.
Given that most plastics are made from petrochemicals, this solution to plastic recycling brings the life-cycle full circle allowing a second use as an oil substitute.
The process could, if implemented on a large enough scale, reduce pressures on landfill as well as ameliorating the effects of dwindling oil supplies in a world with increasing demands on petrochemicals for fuel.
In their approach, the team heats the plastic waste to between 400 and 500 Celsius over a kaolin catalyst. This causes the plastic's long chain polymer chains to break apart in a process known as thermo-catalytic degradation. This releases large quantities of much smaller, carbon-rich molecules.
The team used the analytical technique of gas chromatography coupled mass spectrometry to characterize these product molecules and found the components of their liquid fuel to be mainly paraffins and olefins 10 to 16 carbon atoms long. This, they explain, makes the liquid fuel very similar chemically to conventional petrochemical fuels.
In terms of the catalyst, Kaolin is a clay mineral - containing aluminum and silicon. It acts as a catalyst by providing a large reactive surface on which the polymer molecules can sit and so be exposed to high temperature inside the batch reactor, which breaks them apart.
The team optimized the reaction at 450 Celsius a temperature with the lowest amount of kaolin at which more than 70% of the liquid fuel is produced. In other words, for every kilogram of waste plastic they could produce 700 grams of liquid fuel.
The byproducts were combustible gases and wax. They could boost the yield to almost 80% and minimize reaction times, but this required a lot more catalyst 1 kg of kaolin for every 2 kg of plastic.