1. 16CEN.ACS.ORG APRIL 20, 2015
IN 2009, a company called SNRG Corp.
announced the purchase of an advanced
rubber devulcanization technology. The
firm said it would use the process to build
afacilityinHoustontoextract80millionlb
of recycled rubber per year from scrap
tires.
“The technology being acquired by the
company is unique, proven, and ready
for commercial production,” SNRG
proclaimed.
The Houston plant was never built, nor
were most of the facilities trumpeted over
the years as being able to turn the environ-
mental problem of old tires into valuable
raw materials.
Undeterred, a new batch of companies
is embarking on a fresh round of projects
intended to extract devulcanized rubber or
carbon black from spent tires. The backers
of these projects insist they have solved the
technological and economic problems that
hobbled high-tech tire recycling in the past.
Thankfully, the huge mountains of bald
tires that blighted the American landscape
in the 1970s and ’80s no longer exist. Only
about 75 million scrap tires languish in
piles today, down from close to 1 billion in
1990, according to the Rubber Manufactur-
ers Association (RMA).
Still, old tires continue to be generated
in prodigious volumes. In the U.S. alone,
about 230 million car and truck tires are
discarded every year, says RMA, which
gathers detailed statistics on the topic. And
one notorious tire pile, outside Denver, still
holds close to 30 million tires.
Although tires are almost half rubber,
the rubber can’t simply be melted down
and reused as many polymers can be.
That’s because the rubber is vulcanized—
cross-linked with sulfur in a process
invented by Charles Goodyear in 1839.
Vulcanization imparts needed mechanical
properties but is not easily reversed.
Almost 96% of the scrap tires created
in 2013 did find markets, RMA says. More
than half of them were burned for their
energy content in electric utility boilers,
paper mills, and cement kilns. About a
quarter were ground into so-called crumb
rubber, which is added to asphalt or used in
playgrounds and sports surfaces.
But proponents of devulcanization and
carbon black recovery argue that incinera-
tion and playground surfaces are stopgap
measures that don’t
adequately capture
the value of the use-
ful materials in scrap
tires.
Sam Visaisouk,
chief executive of-
ficer of Tyromer, a Canadian developer
of devulcanization technology, notes that
the market for the 20-mesh crumb-sized
rubber used in playgrounds is already
oversupplied. And backers of alternative
technologies claim that some countries are
looking to outlaw tire-derived fuel on envi-
ronmental grounds.
AT PRESENT, the most advanced commer-
cial-scale tire recycling in the U.S. is prac-
ticed by Lehigh Technologies. The Tucker,
Ga.-based firm uses cryogenic milling to
break down end-of-life tires and other
postindustrial rubber into micrometer-
scale powders as small as 300 mesh. Last
September, Lehigh raised $8 million from
investors including the Japanese synthetic
rubber maker JSR.
Lehigh operates what it calls the world’s
largest micronized rubber powder facility,
with 140 million lb per year of capacity.
Depending on the application, Lehigh says,
the recycled rubber can be added to new
products in amounts of up to 40%.
According to CEO Alan Barton, Lehigh is
enjoying annual sales growth rates of 30%.
Customers, the firm says, include six of the
world’s top 10 tire manufacturers, which
have incorporated the firm’s micronized
rubber into more than 250 million tires to
date. Barton expects JSR to help Lehigh
make inroads in Europe and Asia and
eventually set up manufacturing in those
regions.
Visaisouk and others seeking to develop
tire-recycling technologies don’t begrudge
Lehigh its success to date. “The problem
is so big there will be more than one solu-
tion,” Visaisouk says.
Still, he says, even when finely ground,
vulcanized rubber such as Lehigh’s can
generally be incorporated into new tires
and other rubber products at only a few
percent without affecting performance.
Vulcanization is a thermosetting process
that renders rubber unable to be remelted
and reused at high concentrations.
Many breakthroughs have been pro-
claimed over the years in the pursuit of
devulcanization. “Since the day Charles
Goodyear discovered vulcanization,
people have been trying to reverse it,” says
THE ELUSIVE DREAM
OFTIRE RECYCLING
Undeterred by past failures, companies pursue high-
tech approaches for RAW MATERIAL RECOVERY
MICHAEL MCCOY, C&EN NEW YORK CITY
CCT
HOT MESS
Pyrolysis of
shredded tires
happens in circular
beds at CCT’s
plant in Germany.
BUSINESS

2. 17CEN.ACS.ORG APRIL 20, 2015
“Since the day Charles Goodyear
discovered vulcanization, people
have been trying to reverse it.”
Michael Blumenthal, a former RMA vice
president who now runs the scrap tire
management company MarShay.
Goodyear Tire & Rubber itself revealed
in 1999 that it had patented a devulca-
nization process based on the solvent
2-butanol. In the laboratory, Goodyear
said, the process recovered up to 80% of
the rubber in a used tire, but it was never
commercialized.
A 90-page report commissioned in 2004
by the state of California found companies
and institutions offering roughly 25 me-
chanical, chemical, ultrasonic, microwave,
and biological techniques for devulcaniz-
ing rubber. But the report also found reli-
able information hard to come by and no
plants operating at commercial scale.
“All things considered under current
and likely near-term future conditions,”
the report concluded, “devulcanization
faces an uphill struggle to be competitive
with virgin rubber.”
Tyromer’s solution is to use supercriti-
cal carbon dioxide to rapidly swell rubber’s
molecular framework, preferentially elon-
gating the sulfur bonds for easy cleavage
by shear force inside an extruder. The Ca-
nadian firm claims that new tires or other
rubber goods can contain up to 20% of its
devulcanized rubber without affecting
performance.
Visaisouk was in New Jersey recently to
receive a piece of imported equipment that
has since been shipped to Tyromer’s site in
Waterloo, Ontario. He expects the firm’s
plant to be running by May 1 with a capacity
to devulcanize more than 6 million lb per
year of crumb rubber.
His eventual goal is to sell similar sys-
tems to crumb rubber producers looking to
market a higher-value product. Visaisouk
also claims to be working with two of the
top four tire companies to incorporate
Tyromer’s product into their tires. But like
other executives in the field, he says he
can’t name names.
Another Canadian firm, Phoenix Inno-
vation Technology, opened an 8 million-lb-
per-year plant in a Montreal suburb last fall
to manufacture a devulcanized product it
calls regenerated rubber. “We break 60%
of the sulfur bonds with minimal damage
to the rubber,” says Phoenix CEO Stephen
Murphy.
Phoenix accomplishes this, according
to Murphy, by carefully controlling tem-
perature and shear force in its regenerator
via infrared temperature sensors and a
customized cooling system. The result-
ing rubber can be used in tire applications
such as tractor and mining vehicle tires and
in nontire applications such as conveyor
belts, he says.
THE IDEA OF devulcanizing rubber back to
its original form has an elegant simplicity,
but the reality is complex, MarShay’s Blu-
menthal cautions. Tires contain a mixture
of natural, styrene-butadiene, butyl, and
polybutadiene rubbers plus carbon black,
antioxidants, stearates, and other materi-
als. Breaking carbon-sulfur bonds across
that range of ingredients without damaging
the polymer isn’t easy.
That’s why another cohort of companies
is focused on recovering carbon black, a
tire-reinforcing agent that is created by
the incomplete combustion of an aromatic
oil mist in a hot gas stream. The result is a
finely divided carbon powder that is incor-
porated into tires at up to 30% by weight.
In February, officials from a company
called Delta-Energy announced plans to
build a $45 million carbon black recovery
facility on the site of a former International
Paper plant in Natchez, Miss. Delta-Energy
is a 2005 spin-off of the RJ Lee Group, a
materials characterization and industrial
forensics firm that employs more than 250
scientists.
William Cole, Delta-Energy’s vice presi-
dent of product management, explains that
his company started as an internal materi-
als science challenge at RJ Lee. Scientists
there developed a catalytic pyrolysis tech-
nique that decomposes shredded tires into
carbon solids and a hydrocarbon liquid that
petrochemical companies can use as a raw
material.
Delta-Energy started producing carbon-
black-like products in 2008 at a small facil-
ity in North Dakota. The equipment was
recently relocated to Mississippi, where it
will complement the larger facility planned
for the site. “Natchez puts us strategically
closer to our suppliers and customers,”
Cole says.
A German tire-recycling company, Pyro-
SOURCE: Rubber Manufacturers Association
WHERE OLD TIRES GO Burning for energy
value is the largest U.S. use for scrap tires.
WHERE THEY COULD GO New companies see opportunity in
alternative uses for scrap tires.
Scrap tires generated in 2013 = 233 million
Tire-derived fuel
53%
Ground rubber
24%
Land disposal
8%
Exported
6%
Other
9%
TECHNOLOGY
Micronized
rubber
Devulcanization
Carbon black
recovery
SELECT PLAYERS
Lehigh Technologies
Phoenix Innovation
Technology, Tyromer
Delta-Energy,
Ecolomondo,
Pyrolyx, Reklaim
PROS
Commercially
proven; accepted by
tire industry
Of interest to rubber
industry; potentially
high-value product
Semicommercial;
applicable to variety
of raw materials
CONS
Rubber is still
vulcanized; low level
of incorporation in
finished products
Poor track record;
polymer blends
present challenge
Capital-intensive; tire
industry has yet to
embrace recovered
carbon black
SOURCE: C&EN

3. 18CEN.ACS.ORG APRIL 20, 2015
GUAYULE GETS READY
TO HITTHE ROAD
Companies are looking to the DESERT SHRUB as
an alternative to tropical rubber trees
ALEXANDER H. TULLO, C&EN NEW YORK CITY
BRIDGESTONE
BUSINESS
lyx, wants to get even closer to supplies. In
February, it announced plans to build a tire
pyrolysis facility in Hudson, Colo., on the
site of the largest U.S. tire dump.
Based in Munich, Pyrolyx has developed
a process for continuous recovery of car-
bon black from shredded tires. It is in the
midst of merging with another German
firm, Carbon Clean Tech (CCT), which
has operated a 10 million-lb-per-year re-
covered carbon black facility in Stegelitz,
Germany, since 2012. Unlike Pyrolyx, CCT
uses a batch process.
After the merger is complete, Pyrolyx
plans to build a continuous-process plant
at the Stegelitz site, according to Ulrich
Sattler, the firm’s chief operating officer.
In addition, Pyrolyx has signed a letter of
intent with CH2E, the owner of the Hud-
son tire dump, to build what it says will be
the world’s largest recovered carbon black
plant right next door.
Both Sattler and Cole acknowledge
that their product isn’t exactly the same
as virgin carbon black. CCT’s material, for
example, includes a broader distribution
of particle sizes and may contain some ash.
But both executives say their products can
work as well as the original. “We can sup-
plement or completely replace,” Cole says.
Given the tire industry’s desire to be-
come more sustainable, executives from
tire-recycling companies of all stripes say
the time is right for recycled raw materials.
Yet they also admit they must overcome
a healthy amount of skepticism regarding
the technological and economic viability of
their processes.
The tire industry executives who are in
a position to strike agreements with recy-
cling firms have seen their share of past
failures, Tyromer’s Visaisouk acknowledg-
es. “Senior people have been burned in the
past by believing devulcanization works,”
he says. “ ‘It’s too good to be true,’ is what
everyone tells me.”
Indeed, Blumenthal, the former RMA
executive, has seen plenty of hype and
failure during his 30 years in the scrap tire
industry. For now he is reserving judgment
on the new technology. “I can’t say that
it won’t work,” he says. “What I can say is
that in the past it has not worked.”
Still, Blumenthal holds out the pos-
sibility that technology and economics
will eventually come together to make
advanced tire-recycling technology a real-
ity. “At some point in the future,” he says,
“someone is going to figure out how to
make this work.” ◾
guayule. The war didn’t last long enough to
sustain the program. Only a few hundred
tons of rubber were produced from fields
in California and wild shrubs in Texas be-
fore the project was discontinued (C&EN,
March 29, 1948, page 926).
Big tire companies such as Bridgestone
and Cooper Tire & Rubber Co. as well as
little start-ups such as Yulex are now taking
up the cause again. Seeing a payoff from
diversifying their sources of natural rubber,
they say they are committed to long-term
research of ways to economi-
cally grow and extract rubber
from guayule.
Naturalrubber,knownchem-
ically as cis-1,4-polyisoprene,
is as essential as ever. “A lot of
synthetic work was targeted toward mak-
ing a replacement for the natural product,”
says Bill Niaura, director of new business
development for Bridgestone Americas.
“Those decades of work have shown we’re
not that good yet.”
Natural rubber is still a must for truck
and airplane tires. Niaura explains that
natural rubber strain-crystallizes as a
HOME ON THE RANGE
Bridgestone is growing
guayule at a research
farm in Eloy, Ariz.
FOR THE PAST CENTURY, tire manu-
facturers have sought alternatives to the
natural rubber grown on Southeast Asian
rubber plantations. Dependence on a
single region for the critical raw material
has made their supply chains vulnerable to
blight, infestation, bad weather, political
instability, and, in the 1940s, war.
When Japan cut off rubber supplies in
World War II, the U.S. government had to
act fast to establish a domestic synthetic
rubber industry. The effort not only de-
livered rubber but also helped
establish the modern petro-
chemical industry.
Butthereisnotruesubsti-
tuteforthereal,naturalitem.
Tothisend,rubberproducers
havelongtriedtoextractrubberfromthe
guayule—pronouncedwhy-yoo-lee—shrub
(Partheniumargentatum),nativetothearid
southwesternU.S.Effortstodevelopgua-
yule,however,havebeensporadic,flaring
upintimesofcrisisandthenvanishingjust
asfast.
During the war, the U.S. set up the
Emergency Rubber Project to cultivate
cis-1,4-Polyisoprene
(natural rubber)
n