A P P L I C A T IO N S A N D I M P L E M E N T A T I0NS
Recycling Postconsumer
Nylon Carpet
A Case Study of the Economics
and Engineering Issues Associated
with Recycling Postconsumer Goods
Lester Lave, Noellette Conway-Schempf,James Harvey,
Deanna Hart, Timothy Bee, and Christopher MacCracken
Graduate School of Zndustid Administration
Cmnegie M e l h University
Pittsburgh, PA, USA
I
KeY-Jvords
carpet recycling
landfill cover
materials properties
nylon recycling
recycled carpet plastic (RCP)
recycling economics
Address correspondence to:
Lester Lave
Graduate School of Industrial
Administration
Camegie Mellon University
Schenley Park
Pittsburgh, PA 15213, USA
lester.lave@andrew.cmu.edu
0Copyright 1998 by the Massachusetts
Institute of Technology and Yale University
Summary
Each year 3 4 billion pounds of nylon carpet are discarded
into landfills in the United States.As a case study we examine the technical and economic feasibility of recyclinga portion of this source of discarded plastic.The carpet could be
( I ) shredded for use as daily cover at landfills or as a
strengthening component of concrete, (2) sheared or
chemically processed for reuse as recycled nylon or as pure
nylon feedstock,or (3) made into a new type of plastic.We
estimate the costs of a recycling facility t o handle 450,000
Ib of discarded nylon carpet each month in Pittsburgh,
Pennsylvania.Wefound that with current technology, regulations, and markets,only the recycling of carpet from commercial settings using shearing or chemical processing is
economical and only under very narrow circumstances.We
learned four lessons from this study, First,collection costs
are high and can dominate the economics of recycling. Second, given time and incentives, collection costs can be reduced.Third, trying to recycle products not designed to be
recycled leads t o many problems. Carpet could be redesigned t o make recycling easier by making the carpet out
of a single material and using an adhesive that can be removed easily. Fourth, recycling processes should be designed to produce an existing material if at all possible,
because new materials present marketing problems.
Volume 2, Number 1
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journal of lndustriol Ecology
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A P P L ICAT I 0NS A N D I M P L E ME NTATl 0 NS
Introduction
The high levels of waste generation in the
United States have prompted consumers and industry to reconsider the fate of products when
consumers no longer desire them. Concerns over
the availability of easily accessible landfill space,
the threat of stricter regulations regarding disposal of material, and the potential for profitable
reuse of discarded products and materials have
prompted a closer look at the potential for recycling materials currently considered useless.
Changes in European regulations, such as the
EcoCycle product take-back law in Germany,
which requires manufacturers of diverse durable
products to take back their products once the
end of life is reached (Bremer-Davis 1996), have
prompted manufacturers to consider the effect of
product take-back regulation on their operations. In our judgment, states such as California,
Massachusetts, and New York will enact product
take-back regulations for some goods in the next
decade.
Postconsumer carpet is potentially attractive
for recycling: it is available in large quantities, is
easily separated from other postconsumer wastes,
and has potentially high value. Americans discard about 3-4 billion lb of carpet each year
(Gardner 1995). At present, almost all of this
carpet is hauled away and disposed in landfills,
at a cost of roughly $100 million per year. Used
carpeting accounts for about 1% by weight (2%
by volume) of municipal solid waste in the
United States (Minnesota OER 1995). Rather
than thinking of used carpet as waste that requires disposal, the carpet and plastics industries
are searching for ways to transform it into a valuable raw material.
In this article we focus on recycling postconsumer carpet with nylon face fiber (carpet is
referred to by the type of face fiber). We discuss
the costs and barriers to establishing and operating a nylon carpet recycling facility under the
prevailing economic and marketing conditions
in a large U.S. city (Pittsburgh, Pennsylvania).
We investigate the costs of collecting nylon carpet and then reusing it in three forms: (1) shredded for use as daily cover at landfills or as a
strengthening component of concrete, ( 2 )
sheared or chemically processed for reuse as re-
I I8
journal of Industrial Ecology
cycled nylon or as pure nylon feedstock, or (3)
made into a new type of plastic. A number of lessons emerge from the study, not only about recycling postconsumer carpet but about recycling
postconsumer goods more generally.
Background
Characteristics of Postconsumer Carpet
in the United States
Typical carpeting is constructed of multiple
layers. The face fiber of residential carpet makes
up about 45%-50% of the weight ofcarpet (35%
for commercial carpet). The other components,
by weight, are primary and secondary backing
(lo%), adhesive (6%-lo%), and calcium carbonate or other fillers (30%-40%) (Schut 1993;
Williams 1994; Leaversuch 1993; Minnesota
OER 1995).'
Each of these layers is composed of different
materials. Generally, the backing is polypropylene, and the adhesive is latex. The only material with much recycle potential at the moment
is the face fiber. The quantity of carpet that is
discarded will reflect the sales of new carpet 3 to
20 years ago. Table 1 summarizes two estimates
for 1994 face-fiber market share (Costello 1995;
Williams 1994). We assume nylon 6,6 is 45%
and nylon 6 is 30% of discarded carpet.
Of carpet sold in the United States, approximately 70% is for replacement of old carpet.
About one-third of carpet sold in the United
States is used in commercial applications such
as offices, retail stores, or other commercial
places; the other two-thirds is used in residences (Costello 1995). In general, commercial
installations (such as hotels or office buildings)
Table I Two estimates of 1994 face-fiber market
share
Material
AUiedSignaf
Monsanto
36%
44.2%
29%
14.5%
10.5%
1.1%
~
Nylon 6,6
Nylon 6
Polypropylene
Polyester
Wool and acrylic
26%
26%
11%
1%
Source: Costello (1995), Williams (1994).
A P P L I C AT1 0 N S A N D IMP L E M E N TAT1 0 N S
contain more carpet than a single residential
installation.
T h e principal tasks required to recycle
postconsumer carpet are:
collection, sorting, handling, and storage
of the carpet;
transformation of the carpet materials
into a valuable material; and then,
marketing the recycled material.
Collecting Postconsumer Carpet
The first task in recycling is collecting the
postconsumer carpet. Buildings with large quantities of discarded carpet, such as large commercial offices, are preferable targets for several
reasons. First, the larger quantities of carpet
available reduce the per-unit hauling costs. Second, either the owner knows the type of face fiber or the large quantity justifies testing prior to
removal. Knowing the type of face fiber means
that the recycler, that is, the business collecting
the carpet and doing the first level of processing,
can arrange to acquire only the desired carpet
types. Third, the carpet owner must pay about
$50 per ton for hauling and disposal of the carpet. T h e current tipping fee in Pittsburgh is
about $30 per ton or $O.O15/lb. Thus the owner
should be willing to pay the recycler up to
$0.025/lb to collect the carpet, or would deliver
it to the recycler and pay $0.015/lb in lieu of a
tipping fee.
Because it has more face fiber than commercial carpet, residential carpet is attractive to recyclers. Recycling it, however, presents major
problems. Compared with commercial installations, the quantity is lower and the face fiber is
not known. Distinguishing different face fiber
types, particularly nylon 6 versus nylon 6,6, is
difficult by visual inspection. Thus the recycler
is likely to get all types of face fibers, not just the
desired nylon. Equipment is available that can
distinguish fiber types, but the equipment is ex$600 for a n infrared unit
pensive-about
(Costello 1996)-and because there is no current need to identify the face fiber, this equipment is not likely to be in the hands of carpet
installers. This means that a recycler accepting
all discarded residential carpet, but recycling
only nylon-faced carpet, would have to pay to
1
dispose of the 25% of the recovered carpet that
does not have nylon face fiber.
In many cities, such as Pittsburgh, the municipal solid waste (MSW) service will collect
small quantities of discarded carpet free of
charge from residences. The recycler would have
to pick up the carpet from the landfill, residence,
or carpet store. In cities where residential carpet
is collected with trash, most of the residential
discard carpet would be sent to landfills. Recovering the carpet at the landfill is dirty, difficult,
and dangerous (and usually requires a permit
from the organization operating the landfill). If
the recycler wanted to collect carpet directly
from the residence, the carpet installers could
notify the recycler about the place and time
when the discarded carpet would be removed
during the installation of new carpet. This individual pickup would be the most expensive collection option. We estimated that a truck would
make a round trip of 10-50 miles (16-80 kilometers) taking one to two hours to pickup and
unload 50 square yards (200 lb) of carpet. A t
$0.50 per mile for the truck and $10 per hour for
the driver, the cost is $15 to $45 or $0.075$0.225/1b. We assume collection costs of $O.lO/
Ib for individual residential pickup.
Installers often take the discarded carpet to a
large waste receptacle, known in the United
States as a “dumpster,” at a carpet store or warehouse. At present, recovery from the dumpster is
unpleasant, because the carpet is mixed with
other trash and is often wet, because large
dumpsters are not covered. Although recovery
by such a strategy is possible, it is unpleasant for
the workers and not highly desirable. We estimate the cost of removing discarded carpet from
the dumpster and then hauling it to the recycler
to be about $O.lO/lb. The collection costs can be
reduced by scheduling pickups at adjacent locations, using special containers at carpet stores, or
by charging residences.
The recycler might arrange for the store to
place the discarded carpet in a dry location separated from trash; this solution would be ideal,
but space was scarce at the stores we inspected.
The stores we inspected did not view pickup of
discarded carpet by a recycler to be very attractive. A typical trash collection contract has a fee
that rises much less than proportionally with the
Lave, Conwoy-Schempf,Harvey, Hart, Bee, and MacCracken, Recycling Nylon Carpet
I19
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AP P L ICAT10 NS A N D I M P LE M E NTAT I0NS
size of the dumpster. Thus stores would not save
much by switching to a smaller size dumpster.2
Recycling regulations or prodding from manufacturers should get most stores to find a place to
store the carpet for pickup.
In summary, commercial nylon carpet might
be delivered to the recycler with a payment to
the recycler of $0.015/lb compared to residential
nylon carpet that would have to be picked up at
a cost of at least $0.10/lb. We assume that only
nylon carpet would be accepted from commerical
installations while, for residential carpet, the recycler would incur the cost of disposing of undesirable (nonnylon) carpet.
Transforming and Processing Discarded
Nylon Carpet
We have investigated three different ways to
reuse discarded carpet:
shredding carpet into small pieces,
recycling the face fiber into a high-value
plastic, and
recycling the entire carpet into a lowvalue plastic.
A carpet recycler would choose among these
three alternatives on the basis of the net profit
expected from each. We now estimate the cost
and revenue from each approach.
1. Shredded Carpet Uses
Shredded carpet fiber can be used as filler in
concrete applications or landfill cover applications (Herlihy 1994). For both uses, the value of
carpet fiber is low, hardly greater than zero. In a
modern landfill, the compacted trash must be
covered by dirt or some other material every day
to minimize odor, litter, and pests. Because carpet fiber saves landfill space, it is preferred to
dirt as a daily cover (U.S. EPA 1992). The demand for carpet fiber in this application is virtually unlimited. Thus the price of disposing of
undesired carpet or carpet backing should be no
greater than the cost of shredding the carpet and
transporting it to a landfill.
The Cost of Shredding Carpet
Once carpet has been collected, the cost of
shredding for an operation of this size is estimated
I20
lourno1 of Industrial Ecology
to be no more than $0.045/lb, including unloading, handling, and shredding (Costello 1996).
Alternatively, the cost of hauling and disposal in
a landfill is about $0.025/lb. Thus, with a hauling
cost of $O.Ol/lb, the landfill operator would have
to pay at least $0.03/lb for the recycler to find
shredding superig to landfilling. We could find
no indication that landfill operators would be
willing to pay this much for this material.
2. Recycling as Nylon or Conversion
to a Nylon Feedstock
Pure nylon is a valuable material selling for
$1-$3/lb. Currently, there are two viable technologies for high-value recycling of nylon recovered from carpets. AlliedSignal and BASF have
developed processes for transforming nylon 6 in
carpet back into caprolactam, the feedstock for
nylon 6 (Herlihy 1994). At an AlliedSignal
demonstration plant, the resulting feedstock is
so pure that it can be remade into carpet, rather
than processed for less-demanding, lower-value
uses. Some of the materials, such as calcium carbonate and adhesive, must be disposed of at a
standard landfill at a cost of about $0.025/lb.
Nylon 6,6 carpet, which has the largest market share, is difficult to transform back to original feedstocks because of the combined nature of
the component substances (monomers). The
most attractive use for nylon 6,6 is as mechanically reground nylon feedstock, which is less
pure than virgin nylon 6,6. Pellets of pure
reground nylon, using scrap fiber from the
manufacture of new carpet, currently sell for
about $0.40/lb (Costello 1996). Pellets made
from used carpet are contaminated with dirt and
other plastics and sell for much less.
The Costs of Separating the Face Fiber
from the Carpet
Given the current technology and economics, only the face fiber of carpet is attractive for
high-value recycling. Thus the face fiber must be
separated from the backing and other material.
The undesired part of the carpet would need to
be landfilled at a cost of $0.025/lb.
AlliedSignal buys bundled nylon 6 carpet for a
pilot recycling plant that uses a chemical process
to separate the face fibers from the backing. They
have purchased bundled nylon 6 carpet for $0.05-
APPLICATIONS A N D IMPLEMENTATIONS
$O.IO/lb FOB3from the recycler. AlliedSignal currently pays less than $O.lO/lb, but we will assume
they offer this amount for the rest of the analysis.
Collecting nylon 6 carpet to sell to AlliedSignal
is marginally attractive at best. It costs the recycler almost $0.10/lb for the warehouse, equipment, and labor to bundle the carpet. Thus a
lower price from AlliedSignal, having to pay collection costs, or having to dispose of nonnylon 6
carpet would drive the recycler into bankruptcy.
This business would be attractive now for commercial carpet where only nylon 6 carpet was delivered to the recycler with a payment of $0.0151
Ib, or where regulations were changed so that the
recycler received a payment when residential carpet was delivered.
Rather than selling bundled carpet to
AlliedSignal, the recycler could separate the face
fiber and then sell the pelletized nylon. The simplest way to separate the face fiber is by shearing
it from the backing. We estimate this would cost
about $0.03/lb. Shearing, however, recovers only
30%-70% of the face fiber, depending on the
type of carpet, whereas AlliedSignal recovers
most of the nylon 6 through its chemical process
(the exact amount is proprietary information).
1
The sheared material would then be pelletized at
a cost of $0.09/lb (Costello 1996).
To assess the potential for carpet shearing
and recycling, we first do the analysis for residential carpet, assuming that all carpet is delivered to the recycler at a price of $0.10/lb (see
table 2). If 1,333 Ib of discarded carpet arrived at
the recycler, the collection cost would be $133,
and handling costs would amount to $26.66 (at
a cost of $0.02/lb). Of the 1,333 Ib of carpet,
1,000 Ib would be nylon carpet. Thus the shearing cost would be $30. The 1,000lb of nylon carpet would contain 450 Ib of face fiber, but
assuming a generic shearing efficiency of 50%,
only half of the nylon, 225 Ib, would result from
the shearing. This 225 lb of sheared nylon would
be pelletized at $0.09/lb, or $20.25. In addition,
the cost of disposingof the 333 Ib of carpet without nylon face fiber and the 775 lb of carpet left
after the nylon face fiber was sheared would cost
$0.025/lb for a total of $27.70. The 225 Ib of
nylon pellets would sell for $90. Thus the total
cost of collection, handling, processing, and disposal would exceed the value of the pellets; this
is true even if collection costs were zero. In fact,
just to break even, the recycler would need to
Table 2 Estimated costs and revenues associated with recycling residential carpet into nylon pellets
Description
Discarded carpet:
collection
handling
Carpet without nylon face fibers:
dispose
Carpet with nylon face fibers:
shear
Backing, residual face fiber:
dispose
Nylon face fiber:
pelletize
Total operating costs
Nylon pellets:
sell
Total revenue
Unit cost
Total cost
333 lb
$O.lO/lb
$0.02/lb
$133.30
$26.66
333 lb
$0.025/lb
$8.32
000 Ib
$0.03/lb
$30.00
775 lb
$0.025/lb
$19.38
225 Ib
$0.09/lb
$20.25
$237.9 1
2251b
$0.40/1b
Gross margin (revenue minus variable cost)
Margin excluding collection costs
Material quantity
$90.00
$90.00
-$147.91 (-$O.ll/lb)
- $14.61 (- $0.011/lb)
Assumptions: 75% of carpet is nylon carpet, 45%of residential carpet by weight is face fibez and shearing efficiency is 50%.
lave, Conway-SchempL Harvey, Hart, Bee, and MacCracken, Recycling Nylon Carpet
I 2I
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A P P L ICAT I0NS A N D IMPLE M E NTAT10 N S
Table 3 Estimated costs and revenues associated with recycling residential and commercial carpet into
nylon 6 feedstock and nylon 6.6 Dellets
Commercial
Residential
Unit
Description
Discarded carpet:
collect residential carpet
Collected carpet:
handling
Carpet without nylon face fibers:
dispose
Carpet with nylon 6,6 face fibers:
shear
Backing, residual face fiber:
dispose
Nylon face fiber:
pelletize
Total operating costs
Discarded carpet:
drop-off commercial carpet
Nylon pellets:
sell
Nylon 6 carpet:
sell to AlliedSignal
Total revenue
cost
Material
quantity
Total
Material
cost
quantity
1,333
0
$133.30
$O.lO/lb
1,333
$0
1.000
$26.66
$0.02/lb
$20.00
0
333
$8.32
$0.025/lb
$0
600
600
$18.00
$0.03/lb
465
$18.00
495
$11.62
$0.025/lb
135
$12.38
105
$12.15
$210.05
$0.09/lb
0
$0.015/lb
$9.45
$59.83
1,000
$15.00
$0
135
105
$54.00
$0.40/lb
$42.00
400
400
$40.00
$94.00
$O.IO/lb
Gross margin
- $116.05 (- $0.087/lb)
Margin excluding collection costs
$17.25 ($0.013/lb)
Total
cost
$40.00
$97.00
$37.17 ($0.037)/lb
$22.17 ($0.022)/lb
Assumptions: 75% of carpet is nylon carpet, nylon 6,6 accounts for 45% of the carpet market, or 60% of the nylon
carpet market; nylon 6 accounts for 30%of the carpet market or 40%of the nylon carpet market; 45%of residential
carpet is face fiber, 30%of commercial carpet is face fiber, and shearing efficiency is 50%.
*Recall that residential carpet is 45%face fiber, while commercial carpet is 30%face fiber by weight.
charge at least $0.01 I/lb as carpet was delivered
to the warehouse.
For comparison, in table 3 for both a residential and commercial scenario, we consider a
combination of shipping nylon 6 carpet to
AlliedSignal and shearing nylon 6,6 carpet. In
the residential case, 1,333 lb of carpet collected
by the recycler would contain 333 lb of carpet
without nylon face fiber (to be disposed of). Of
the 1,000 lb of nylon carpet, 400 lb would be nylon 6 carpet. At $0.10/1b, the recycling company
would receive $40.00. The other 600 lb of nylon
6,6 carpet (containing 270 lb of nylon 6,6) could
be sheered to obtain 135 lb of pure nylon 6,6.
The remaining 465 lb of sheered carpet must be
I22
journal of Industrial
Ecology
disposed of. As shown in table 3, unless collection costs drop below $0.013/lb, the costs again
exceed the revenues.
This analysis shows that for residential carpet, shearing is less attractive than shipping
bundled carpet to AlliedSignal at $O.lO/lb. Only
if collection costs drop below $0.013/lb does the
gross profit margin reach zero. Given that we estimate the collection costs for residential carpet
to be $0.10/1b, recycling residential carpet is not
an attractive business. In the case of commercial
carpet, the recycler need take only the carpet
desired-however, face fiber accounts for only
about 35% of commercial carpeting. If only nylon carpet were recycled, using the same sce-
A P P L I C A T I O N S A N D IMPLEMENTATIONS
nario as in table 3, accepting only commercial
nylon carpet and charging a drop-off fee of
$0.015/lb would result in a gross margin of
$37.17, or about $O.O37/lb. Note, however, that
if installers insisted on being paid to drop off the
carpet, a payment of as little as $0.022/lb would
push the recycler into the red.
It appears that the most profitable arrangement would be to accept only nylon 6 carpet. In
the best-case scenario, if the installers paid
$0.015/lb when dropping off the carpet and handling was $0.02/lb as assumed previously, the
gross margin would be $0.095/lb when the carpet
was sent to AlliedSignal. As a solution to carpet
landfilling,however, this is not particularly effective: recycling only the face fiber of nylon 6 carpet would reduce the amount of carpet ending up
in landfill by less than about 14% (30% of carpet
is nylon 6; face fiber is about 45% of the carpet).
3. Converting Whole Carpet to a New
Plastic
Monsanto (1994) has patented a process for
transforming entire nylon 6,6 carpeting into a
recycled carpet plastic (RCP). The entire carpet
is shredded and processed to remove most of the
dirt. The remaining material is melted and
mixed in two stages. During the second stage, a
chemical compatabilizer helps meld the face fiber, backing, adhesive, and calcium carbonate
into a new material, RCP.
Transforming Nylon 6,6 Carpet
to RCP
We examined the size of a facility, equipment, and personnel needs for a carpet-recycling
facility based in Pittsburgh that would use the
Monsanto process to convert entire pieces of
nylon 6,6 carpet into RCP. The facility is assumed to process 450,000 lb of discarded carpet
per month, of which 200,000 lb would be nylon
6,6 carpet. We assumed a single collection facility in the same building as the processor. The
process of producing RCP has the nylon 6,6 carpet being shredded, cleaned, and fed into a series
of machines that remove most of the dirt and
inorganic filler (and some of the face fiber). The
carpet is then transferred to an extruder where it
is melted and mixed with the compatabilizerand
1
Table 4 Best-case scenario for recyclingof nylon
6,6 to RCP in Pittsburgh (monthly costs)
Component
Disposal costs
Rental
Carpet collection
Labor
Depreciation
Compatabilizer
Total
Cost per munth
$8,053
$5,000
$0
$46,987
$13,784
$21,440
$106,264
.
.
Revenue from the sale of Nylon 6 = $13,500.
Cost per pound of pellets produced = $0.53.
converted into pellets. We assume carpet without nylon face fiber is sent to the landfill and
that nylon 6 carpet is sold to AlliedSignal.
As shown in table 4, assuming zero collection
costs and an income from selling nylon 6 carpet
to AlliedSignal, the cost of producing RCP pellets was found to be $0.53 per pound of pellets.
With collection costs of $O.lO/lb, the monthly
costs would increase by $45,000, or $0.78/lb.
Based on the price of virgin nylon at $1-$2/lb,
this recycling offers the most potential. However, because the pellets contain some impurities
with the nylon 6,6, a premium price, as explained below, is not expected for the material.
Marketing the Material: Uses for
Postconsumer Carpet Plastic
The market outlook for plastics in general is
excellent, with increased usage of plastic materials in many areas. Recycled plastics are more
difficult to market, however, unless their quality
and characteristics are equal to virgin equivalents. In general, virgin plastics appear to sell at
about twice the price of recycled equivalents
(Hart 1995), with virgin nylon materials selling
for about $1-$2.30/lb and recycled material,
shredded plastic from product scraps, currently
selling for about $0.40/lb (Costello 1996).
To discover uses for RCP, we first need to
know its characteristics and price. Perhaps the
two most relevant properties of the material are
its Young’s Modulus, E, and density, rho, because
they indicate stiffness and low weight. Figure 1
shows RCP in comparison with other materials.
Love, Conway-Schempfi Harvey, Hart, Bee, and MacCrocken. Recycling Nylon Carpet
I23
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A P P L I C AT1 0 N S A N D I M P L E M E N TAT I 0 N S
10
1.o
0.1
0.3
1.o
3.0
10
Density (Mg/m^3)
Figure I Materials comparison of RCP
Source: Adapted from Ashby ( I 992).
The properties of the RCP overlap those of its
main constituent compounds, namely, nylon
and polypropylene. But given the amount of fill
material and dirt mixed into the plastic, the
strength and density are slightly higher. Table 5
shows the physical properties of RCP in terms of
tensile strength, tensile modulus, elongation,
and impact strength. For comparison, we have
calculated the properties of six other plastics,
including nylon 6,6. The table shows that RCP
does not have any unique characteristics that
would make it desirable, other than the fact that
it is a recycled material.
A simpler characterization of RCP is revealing. Even with the addition of the compatabilizer,
RCP is not a uniform material. Parts of the various materials can still be identified. Given that
the components of the RCP will vary from batch
to batch depending on the exact composition of
the carpet processed, the range of values for each
property is much wider than that of "pure" plastics. This greater variability and uncertainty of
the RCP properties makes it a less desirable
choice for products with specific and exacting
physical requirements. In addition, because RCP
is a mix of face fibers of different color and of
other materials, its color is typically olive green.
It could be dyed black, but other colors would be
difficult to achieve.
In addition to color limitations, RCP has
other undesirable characteristics. Because it
contains a high percentage of inorganic material, its melt and flow rates are likely to be slow,
increasing processing (mold) time. In addition,
as a high-melt, crystalizable polymer, the nylon
6,6 in the composite would require higher processing temperatures, further decreasing the
melt flow rate and increasing cooldown time in
the mold. Thus RCP will probably have higher
energy costs and take longer for molding than an
easily processed material such as polystyrene.
Perhaps the most important shortcoming is that
RCP is brittle, as a result of the high proportion
of inorganic material in the plastic. Thus RCP is
not a desirable material for applications where
the plastic would have to stand up to impacts.
RCP appears to be roughly comparable to polystyrene, although it would have a higher melting
temperature and would take longer to mold and
would use more energy. Because it is not a known,
tested material, RCP is less desirable than polystyrene. We conclude that RCP would have to be
considerably less expensive than polystyrene, unless there are regulations or strong preferences for
recycled materials. Virgin polystyrene currently
Table 5 Physical properties of RCP compared with those of several typical polymers
Polymer
RCP
PS
N66
ABS
PP
HDPE
PET
Tensile strength
1O"3 psi
Tensile modulus
1O"5 psi
Elongation
%
I m p a t strength (notched)
ft-lb/in
5.6-5.9
5-12
9-12
3.5-6.2
4.3-5.5
3.1-5.5
8.5-10.5
3.64.3
4 4
1.8-4.2
2-3.5
1.6-2.3
0.6-1.8
4.6
3
1-1.5
60-300
5-60
200-700
2-1000
50-300
0.48-0.60
0.25-0.40
1-2
3-8
0.5-2
0.5-2
0.25-0.35
= Recycled Carpet Plastic; PS = Polystyrene; N66 =Nylon 6,6; ABS = Acrylonitrile-Butadiene-Styrene
Co-polymer; PP = polypropylene; HDPE = High Density Polyethylene. Data adapted from Williams (1994), and
McCrum e t al. (1992).
Notes: RCP
I24
Journal of Industrial Ecology
APPLICATIONS A N D IMPLEMENTATIONS
sells for about $0.30/lb. At the estimated cost of
$0.53/lb for RCP pellets when collection costs are
zero, this option is not acceptable.
Because it was the option with the most potential for profitability for the recycler, we gave
considerable effort to evaluating the market for
RCP. Finding a use for a new material requires
considerable work and ingenuity. The users must
be convinced that the new material is attractive
and will stand up to the proposed use.
Because RCP is not a currently marketed
plastic, we sought to discover markets where it
might compete, such as serving as a replacement
for wood in outdoor applications. This market is
already occupied by low-quality mixed recycled
plastics. Plastic wood has the advantage of not
being attractive to termites or fungus. To protect
natural wood in outdoor applications, it is filled
with or coated with a variety of pesticides that
are toxic to people. For example, telephone
poles face disposal problems because of the impregnated pesticides (Lebow 1993).
The plastic would also have the advantage of
being an engineered product, allowing for new
designs. A plastic telephone pole could be a hollow cylinder that was much lighter than, but just
as strong as, a wooden pole, making installation
easier. The pole could be designed to absorb
much of the energy of a vehicle collision and thus
lower highway deaths. Preventing deaths would
come at a price, however: these poles would be
put out of service by vehicle collisions, leading to
more disruptions in electricity and telephone service and greater replacement costs.'
A telephone pole made of a new material
would have to be tested in a wide variety of conditions to demonstrate that the pole could continue to perform for decades in a wide range of
temperatures and weather conditions. Producing
a known material saves the recycler from having
to prove the properties of the new material.
Factors that Could Increase the
Attmctiveness ofRecycling Nylon Carpet
A variety of actions would change the attractiveness of recycling nylon carpet. Market actions would include increases in the price of
petroleum, increases in landfill prices, and consumer desires for recycled material. Government
1
actions would include banning discarded carpets
from landfills, forcing manufacturers to take
back and recycle their carpets, refusing to collect
discarded carpet with MSW,or forcing stores
selling replacement carpet to deliver the discarded carpet to a recycler. Petroleum prices
would have to rise sharply before it would induce
recycling on the basis of raw materials costs. The
same is true for landfill prices for avoided disposal costs. DuPont currently offers customers
the option to pay $1 per square yard ($0.25/lb)
to recycle their nylon carpet. In 1996, three million square yards were recycled in this program.
(DuPont 1997). Government laws and regulations can force recycling. At present, none of
these factors appears likely to make carpet recycling much more attractive.
Lessons Learned
Our project allowed us to discover a few painful truths about recycling (see also Carpet and
Rug Institute 1995). The first is that collection
costs are important. In each scenario investigated, collection costs led to a net profit loss. To
make recycling economically attractive, the recycler cannot pay for delivery of discarded carpet.
The second insight is that, given time and incentives for adjustment, collection costs could be
reduced. Installers who currently take loads of carpet to landfills could take them to strategically
placed carpet collection points. If the carpet is labeled, the recycler could accept only the desirable
carpet. Given that the landfill has a tipping fee,
the recycler could charge up to the tipping fee.
Thus, with adjustment, collection costs would become negative, and most of the expense of disposing of unwanted materials would disappear.
The third lesson is that trying to recycle
products that were not designed for recycling
poses many problems. For carpet, identification
of the face fiber and separation of the different
components are obstacles. An obvious, low-cost
change would be to note the face fiber on the
underside of the carpet to facilitate sorting.
Other changes that become progressively more
expensive would be to (1) make the backing of
carpet from the same material as the face fiber,
(2) choose the adhesive, so that it could be easily removed during recycling, and (3)eliminate
Love, Conwoy-Schernpf; Harvey, Hart, Bee, ond MocCrocken, Recycling Nylon Carpet
I25
1
APPLICATIONS A N D IMPLEMENTATIONS
the calcium carbonate, leaving a single material
that could be much more easily recycled. If all of
these changes were made, the recycler could get
only the desired carpets, and almost the entire
carpet could be pelletized for recycling. Recycling would be a n attractive business under these
conditions, even at a collection cost of $O.lO/lb.
The final insight is that the recycling process
should produce a n existing material, if a t all possible, given that new materials face major marketing problems. In the case of RCP, the material
has value as a commercial material, but the inconsistency in properties makes it less desirable.
Acknowledgments
This study was funded by a grant from
Monsanto Corporation and the Green Design
Consortium a t Carnegie Mellon University.
Deanna Hart c.ontributed engineering analysis
from her M.S.thesis in the Department of Civil
and Environmental Engineering under the supervision of Professors Francis McMichael and Chris
Hendrickson. Business analyses were carried out
in a n MBA project course by Timothy Bee, James
Harvey, and Christopher MacCracken. The
course was supervised by Professors Lester Lave
and Noellette Conway-Schempf.
Notes
'
1. One square yard of carpet weighs approximately
4 Ib; one square meter approximately 2 kilograms.
2. The cost of weekly pickup in Pittsburgh varies
with container size: 4 cubic yards: $80/week =
$20/cubic yard, 8 cubic yards: $120/week = $151
cubic yard, 20 cubic yards: $280/week = $14/cubic yard (Phillips 1997).
3. Free on board (FOB) is a designation used in
shipping to indicate that a quoted price does not
include the cost of shipping (i.e., the purchaser
pays the cost of transport).
4. Telephone companies are unlikely to welcome
the controversy, and likely lawsuits, that would
ensue from being able to use a pole that prevented some highway deaths at the cost of more
frequent disruptions and replacement.
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