"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
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.