A decade-old technology may spell relief for the nearly 800 million tires stockpiled in landfills and the additional 270 million scrap tires generated annually in the United States.
Super Critical Fluid (SCF) technology, developed by Dr. Jagdish Dhawan of the University of South Alabama (USA), Mobile, Ala., and Dr. Richard Legendre, a retired chemistry professor, converts scrap tires into crude oil and carbon black content in its original form.
Advanced Recycling Sciences (ARS) Inc., Tustin, Calif., bought the patent last year, and its subsidiary, Tires2Oil Inc., also based in Tustin, is helping to develop the process. Applied Power Concepts (APC) Inc., Anaheim, Calif., has sub-contracted with ARS and Tires2Oil to supply the research and help develop the world's first scalable pilot plant tire recycling facility, according to the company.
The Tires2Oil process, based on the SCF technology, depolymerizes scrap rubber in a high-pressure reactor, recovering oil and carbon black in its original form. Then, it purifies the remaining oil and carbon black by removing sulfur.
Once recovered, tire oil can be used to produce materials such as chemicals, new tires and fuel. Carbon black can be used to produce new tires, rubber and activated carbon, says Sudheer Helekar, project director for Tires2Oil. According to Helekar, the process leaves no waste because everything that is recovered is reused.
Tires are made with rubber, carbon black, sulfur, steel wires and nylon threads. When melted, tires separate into oil, gas, carbon black and steel. Nylon threads dissolve into the oil, and sulfur remains with the oil, gas and carbon black.
The difficulty with pyrolysis, a common tire-recycling process, is that the recovered materials must be used immediately or they turn to waste, says Helekar. Also, he says that tire oil is unstable and has a high-sulfur content, which can lead to the production of lower-quality material. Conversely, the Tires2Oil system removes the sulfur and is expected to produce oil with potentially less than 15 parts per million (ppm) sulfur content to comply with environmental standards.
According to a Tires2Oil report, the system will produce 476,300 tons of carbon black, or 333,400 tons of activated carbon, and 5.5 million barrels of oil annually from 270 million scrap tires. Depending on the reactor used, a tire pile can take about 30 minutes to process. A typical plant will process about 3 million tires per year, Helekar says.
The Tires2Oil plant will be self-sufficient by using process gases and thermal energy. If tire oil is used to produce power, one-fifth of the power will be used to operate the plant, Helekar says.
Project cost varies between $8.5 million and $12 million, depending on the eventual use of oil and carbon black. ARS and Tires2Oil estimate that it will take about two years to recover the original costs.
But economic benefits cannot be realized until the recovered materials are used commercially. Helekar feels that further system improvements will help achieve that objective. However, the process won't be ready for commercialization until Jan. 2002.
Once the Tires2Oil process is ready for commercial use, there could be as many as 100 such plants worldwide, Helekar says. Tires2Oil hopes to eventually offer the technology to other companies to develop new plants through joint ventures and agreements.
Keith J. Fryer, president and COO of ARS, says that it is too early to determine the future of the system, but he's optimistic. “There's no doubt we're excited about the potential of the system,” he says.