"Technically possible but not economically viable," American Honda Motor Co. concluded after examining whether its plastic gas tanks could be used as fuel or as a fuel ingredient when vehicles are discarded.
The success story of automobile recycling has been shadowed for decades by the problem of the associated nonmetallics plastics, rubber, glass, foam and so on, collectively called fluff.
Honda's comment can be applied to the entire field of trying to make fluff economically useful. Interesting technologies exist, but the crunched numbers aren't alluring. That could change if landfill rules become more onerous, fluff's energy content benefits from a jump in oil prices or engineers come up with a breakthrough in response to increasingly stiff vehicle recycling edicts in Europe.
Bassam Jody of Argonne National Laboratory, involved in shredder residue issues since 1990, has written an overview of the field. He lists nearly 200 papers, articles and books written by vehicle residue researchers from 1957 to 2006. Tallied year by year, the flow of titles peaked in 1999, then waned. Although the problem hasn't been solved, shredder fluff is no longer a hot topic. Unless there's a breakthrough in the economic or regulatory factors, the stuff will continue to go to landfills.
At California's Department of Toxic Substances Control, Bob Boughton hopes for some eventual romances between the seven vehicle shredders and 11 cement kilns in the state. Cooperation between the two types of activity might simplify fluff disposal, he said.
Cement is made in kilns at temperatures higher than ordinary combustion. Burning fluff in incinerators to generate electric power raises concerns about trace substances that can affect people's health. Kilns potentially solve most of those concerns because the very high temperatures neutralize polychlorinated biphenyls (PCBs) and avoid the possibility of dioxins as a combustion by-product. And if the fluff contains trace levels of heavy metals, the interaction with kiln dust creates a bonding that prevents the heavy metals from leaching in landfills. Cement makers can obtain useful raw materials from some of the fluff components lacking energy content. That's helpful because the portions of fluff with energy value—plastics, light rubber and foam rubber—are less than half the fluff stream emerging from shredders.
Boughton has looked into the economics and chemistry of creating fuels from shredder residue suitable for cement kilns. He said the operator of the equipment making the fuel should be able to break even financially. If the raw fluff includes significant traces of copper, selling the recycled copper could boost a break-even facility into one making a profit. That leads to an irony of competing technologies. The traditional sorting equipment used by shredders can't capture all the ground-up copper, as Boughton noted. However, recent improvements in sorting have pushed the recovery ratio for copper higher at those shredders implementing the new technology, so the copper recycling bonus envisioned by Boughton might soon vanish.
However, cement kilns are an industry closely watched by environmental regulators. Boughton says kiln operators would want to satisfy themselves that fluff-derived fuel and raw material aren't significantly impaired by mercury from switches or PCBs from capacitors in older cars, or even lead from wheel weights.
His rough statistics for U.S. shredders put output at 15 million tonnes a year, of which 3 million tonnes are fluff. If 1 million tonnes of that fluff became fuel, it could supply 6 percent of the cement industry's energy, according to Boughton.
He said the California Department of Toxic Substances Control ranks shredder fluff third among high-volume wastes as a potential source of pollution, behind automotive lubricants and discarded electronic equipment.
An intriguing hint of another line of research comes from American Honda in Torrance, Calif., which said it is in touch with a project involving high-temperature treatment of shredder residue. "The project will evaluate various aspects of gasifying shredder waste to produce methanol, ethanol and biodiesel fuels," the company said. "The fuels will operate machinery on site and generate electricity, which may be sold back to local municipal grids."
American Honda declined to elaborate on who is running the project, or where. At one point it seemed that Changing World Technologies Inc., West Hempstead, N.Y., might fit that description. The company has a Philadelphia offshoot, Thermo Depolymerization LLC, known to be working on fuel from shredder fluff. But the chairman and chief executive officer, Brian Appel, seemed almost indignant in replying to AMM via a publicist to shoot down that surmise. "They are referring to a gasifier, which is a renamed incinerator. Not us," Appel said.
The Changing World Technologies approach is known as thermal depolymerization, creating short molecular chains out of longer ones using heat and pressure in the presence of water. The company's major plant, in Missouri, applies that strategy to food manufacturing wastes. Shredder fluff is one of the alternate feedstocks being examined by the company's research and development arm in Philadelphia.