Sensor sorting technology for scrap, having matured over the
past five years, can create ever-more-subtle types of
nonferrous scrap. But just how far does one need to sort? Well,
Globalized manufacturing has limited such technological
sophistication to niche assignments in advanced countries'
scrap industries, according to Adam Gesing, principal at Gesing
Consultants Inc., Tecumseh, Ontario.
"It's not always the case, but the problem is when the
Chinese are in the market you can't compete," Gesing said.
"It's a totally economic choice, but it's a biased economic
choice. If you were a shredder, why would you sort if you could
sell the mixed material for more money than you could sell the
products for in the North American market? The prices for
sorted material by parent metal in North America and in Europe
were less than what the Chinese and the Indians were paying for
zorba." Zorba is the unsorted nonferrous goulash that gets past
But China's hand-sort strategy might have begun losing some
of its advantage. "While we are decreasing wages here to meet
China, the Chinese wages are rising to meet ours," Gesing said.
"Eventually the Chinese will replace the hand sorters on the
docks in Guangzhou (the capital of China's southern coastal
province of Guangdong) with particle sorters" that use sensor
Sensor sorting can work economically for U.S. scrap
consumers willing to buy lower grades of material, Gesing said.
However, the medium-term prospect is dim for such investments
because of global restructuring.
"If the assembly plant is in China and the component
manufacturing plants are being shifted to China, then the
smelters are going to follow. The only people that will be left
on our continent are the shredders," he said. "At that point it
doesn't matter if the sorting plant is in Michigan or is
sitting in Guangzhou, where all the scrap is arriving by
One issue is how far you need to sort before scrap goes into
the melt. "You do need to sort by parent metal. And that's
doable by hand, by the way it feels in the hand, by the color,"
Gesing said. "From aluminum, there is only one alloy you can
make from old scrap-380 (for engine blocks). As long as there
is enough market for your lowest common denominator alloy,
anything more you're doing (to sort) is a waste."
The evolution of sensor technology has made heavy media
separation obsolete, he said. Such technology uses fluids or
aerated sand to segregate shredded materials by density.
The final breakthrough around 2005 was the X-ray sensor with
dual energy levels, Gesing said. "With the advent of the
sensor-based approach, I think it would be easier to operate a
sensor-based system than a sand-based system."
Every shredder needs eddy-current sorting because the metal
content is too low without it, according to Gesing. If the
settings aim at a very high metal content, in the 90-percent
range, the price is better. However, certain sorts of metals
also have been eliminated by so high a target using eddy
"The further you're going to ship it, the more it makes
sense to upgrade the scrap" by ratcheting up the ratio of
metallics to nonmetallics in the eddy current's output, Gesing
said, noting that recovering scrap prices are reviving the
market for sensor sorting.
"It has probably changed enough that it actually makes sense
to do it. The question is to whom does it make sense? To a
shredder operator? At this point, probably not," he said. "It
does make sense to the alloy producer in the aerospace
industry-to make sure that production scrap can be refined back
into aerospace alloys. That cannot be done by hand sorting.
You're sorting by alloying elements."
He also sees room for expanded sensor sorting on the intake
side of secondary smelters. "That's a way to get your hands on
low-grade metal (from dealers and brokers) that they can
upgrade and survive," he said.
A longtime observer from an adjacent industrial niche said
several smelters have shaped their intake procedures around
major quantities of media-flotation twitch. These are typically
plants that supply molten alloy to the auto industry and favor
scrap that doesn't need adjusting before melting. Those
smelters are unlikely to abandon twitch, the source said.
But for most scrap consumers, "twitch in itself is
constrained by the price of aluminum cast scrap. If I'm paying
70 cents (per pound) for old cast, I can't pay 80 cents for
twitch. I've got to shred the cast and get out the 1- to
2-percent marginal iron. But crushed cast, metallurgically, can
be a more desirable item than twitch," he said. "The Far East
assesses the (shredded) product to remove all of the industrial
metals from the car efficiently. We are still in that mindset
of wanting to produce a steel product out of the car and an
aluminum product out of the car."
Electronic scrap's unique problems can be dealt with by
sensor technology, but the economics can be tricky, according
to Gesing. "The problem with electronic scrap is that in order
to liberate mono-material pieces you need to shred it finer. If
you shred it finer to go to sensor sort, then your throughput
goes down. The question then is the economics of doing a
particular separation," he said. "If you have a fraction with
precious metals, that makes all the sense in the world. And
once you're doing a slow sort of finer particles, your sensors
can spot and divert more effectively aluminum burdened with
So a slow sort, once chosen for the precious metals, can
eliminate most aluminum contaminants. As for the contaminated
aluminum stream, "you can reshred that portion to liberate
those particles," Gesing added.