Palm Beach County
Solid Waste Authority
FDEP Innovative Grant Proposal
Optical Sorting System to Recover Mixed Cullet
Abstract
The 1988 Florida Solid Waste Management Act recognized the excellent
potential for glass recycling in the State of Florida by including glass in the
list of mandatory materials. Today, collection of flint, amber, and green
glass is part of nearly every major municipal recycling program in the State.
Despite the popularity of glass recycling, its success in Florida has been
only marginal. Two factors that limit the success of glass recycling are the
collection apparatus and end users requirements. Modern collection
systems used by most jurisdictions for commingled containers require the
material to be transferred three or four times. This handling results in
breakage and produces large amounts of mixed cullet at the MRF. Glass
breakage erodes recovery and creates a marketing problem since end
users demand color-sorted product. Color sorting is a labor-intensive
process that current market prices do" not support.
The Solid Waste Authority of Palm Beach County (SWA) is proposing a
project that will serve as a proving ground for an exciting and innovative
approach’s to improving municipal glass recycling. The proposed project
will apply advanced optical sorting technology to the mixed broken cullet
currently produced as residue of the MRF glass sorting process. This
innovative technology will clean, size, and color sort the mixed fraction,
thereby transforming a processing byproduct currently requiring disposal
into a valuable resource with proven markets.
By demonstrating the operational effectiveness and economic viability of
this innovative technology and promoting technology transfer, the proposed
project can significantly improve the economics of glass recycling and
increase Florida's glass recovery rates. Our hope in undertaking this
project is that it will help make glass recycling more feasible for other
Florida counties and for municipal recycling programs everywhere.
Project Description
The SWA recently completed a 4.4 million dollar renovation of its Residential
Materials Recycling Facility (MRF) in West Palm Beach, Florida. The largest
component of this renovation project consisted of a 27,000 square foot expansion of
the existing structure and replacement of the commingled materials processing
system with a Countec McMrf 1000.
The new Countec processing system, which can process over 13 tons of
commingled materials per hour, has dramatically improved the efficiency with which
the Authority can process commingled containers. One the most beneficial features
of the Countec system is a screening system that removes the mixed broken
fraction from the commingled stream at the beginning of the process. This feature,
along with the added space provided by expansion of the existing structure, permits
the addition of an optical sorting system to recover color-sorted glass from mixed
broken cullet.
The purpose of the proposed Innovative Grant Project is to implement an innovative
optical sorting system to remove contamination and color sort mixed cullet to
recover clear glass for recycling. The optical sorting system, which has the capacity
to process up to 5 tons per hour of mixed broken cullet, will be incorporated into the
existing Countec system and will be used to remove the amber and green fraction
(approximately 40% of the glass fraction) from the mixed cullet stream. The final
product of optical sorting will be contaminant-free flint, or clear, glass ready for sale
to end markets.
The screening stage of the existing Countec processing system consists of dual
trommel screens located on each infeed conveyor directly after the first pre-sort
station. These screens re ' move glass shards less than two inches in diameter.
After exiting the trommel screens, material is either conveyed directly to a storage
bunker located adjacent to the tip floor or to a crushing and screening operation and
then to the storage bunker.
This transition point in the existing system will be the starting point for the proposed
optical sorting system. In order to maintain flexibility and incorporate optical sorting,
a three-way diverter will be installed at this point to allow material to be directed to
one of the two alternate functions described above or to the optical sorting system.
Material directed to the optical sorter is first deposited into a hopper where it is
metered onto an inclined conveyor using a vibrating feeder. As it is conveyed, the
material is passed under a cross-belt magnet for removal of ferrous metals. The
material is then deposited onto a two-deck screen. Material larger than 1 ¼ inches
passes across the top deck and returns to a double roll crusher designed to reduce
oversized particles for optimum color sorting. The crusher consists of two rotating
steel drums that turn very slowly to avoid creating excess fines. In addition to being
chromium plated to increase wear, the drums are spring loaded to assist in passing
non-crushable items. After the oversized material is processed through the crusher,
it is returned to the feed hopper.
Material that passes through the top deck screen falls onto a 1/2 inch screen.
Material that passes through this screen is conveyed to an outside storage bunker
for reprocessing. Material that passes over this screen is properly sized and
continues through the optical sorting system.
Properly sized material (i.e., particles from 3/8 inches to 1% inches) is then
vacuumed using a 75 horse power vacuum equipped with a bag house filter to
reduce airborne particulate matter. Vacuuming removes light contaminants such as
labels and caps in final preparation for presentation of the material to the optical
sorting unit.
The optical sorting unit can be operated in two distinct modes. For purposes of the
proposed project, the unit will be operated in the color sort mode. In this mode, the
system rejects the smallest fraction (in this case, colored glass) from the mixed
stream. Using a proprietary combination of optical and microprocessor technology,
the sorter first identifies the unwanted fraction and then triggers the firing of an air
solenoid to remove the selected fraction, leaving the flint, or clear, glass to be
recovered for recycling.
The optical sorting system can also be set to remove ceramics and metals, both of
which are identified and recovered in virtually the same manner as colored glass is
removed in the color-sorting mode. This second mode is used primarily for quality
control of more highly contaminated materials.
The flint, or clear, glass recovered by the optical sorting system is clean and ready
for sale to end users. The remaining fraction, which consists primarily of amber and
green glass, can be further sorted to separate the two colors for resale when market
prices justify the expense of additional processing. The system produces only a
small residue stream consisting of less than 1/2 inch shards, ceramic contaminants,
and any ferrous metals extracted by the system.
Project Timeline
The proposed optical sorting system will require significant time for procurement
and installation of system components. A detailed timeline for the procurement,
installation, and testing of the system is presented below.
DATE
ACTIVITY
3/2/99
SWA notified of grant award
4/16/99
Procurement of all system components complete
7/16/99
Delivery of all system components to MRF complete
9/17/99
System installation and start-up complete
10/15/99
Acceptance testing complete
10/18/99
Normal system operation begins
Proposed Project Budget
The Recycling Department and the SWA are extremely enthusiastic about
implementing this technological innovation. A review of the budget summary
provided below will show our substantial financial commitment to the project. Despite
the SWA's significant financial investment, without full grant funding the SWA will be
unable to pursue this project.
Item
Cost
Optical Sorting Unit
94,000
Ancillary Equipment
(Hoppers, Conveyors, Screeners)
147,400
Mech & Electrical installation
51,000
Air Compressor
3,500
Site Work
35,000
Sub Total
Contingency @ 5%
Project Total
330,900
16,545
347,445
Total Grant Funding Requested
213,050
SWA Funding (Pending SWA Board Approval)
134,395
Estimated Annual O&M Costs
30,000
Cost Effectiveness
The proposed optical sorting technology is without question the most
innovative improvement to glass sorting since the beginning of wide-spread
recycling in the early 80s. As with all new technologies in their infancy, the
system is not inexpensive. The proposed optical sorting system has an
estimated cost of approximately $300,000 as detailed in Section 2, Project
Description, of this proposal. Clearly, this technology, although effective, is
not appropriate for all applications. Processing systems that generate less
than three tons per hour of mixed broken cullet will have difficulty justifying the
expense of this new technology.
While the cost for this new technology, is substantial, the benefits gained from
improved resource recovery and revenue generation can be equally
significant. General estimates of cost/benefits ratios for the proposed system
can be developed using available information about current glass processing
and projections of potential recovery rates offered by optical sorting
equipment.
Based on a previously performed detailed analysis of the mixed broken cullet
stream, the SWA has determined that the material stream consists of roughly
60 percent flint and equal parts amber and green glass. Thus, of the 12,122
tons of mixed cullet the SWA produced last year, 7,273 tons (60 percent) was
flint. The proposed project targets this highly marketable fraction of the
stream for recovery.
As indicated in Section 2, Project Description, glass feedstock must be clean
and sized in order to achieve maximum operating efficiency from the system.
Cleaning and sizing operations typically result in a loss of material of
approximately 15 percent. In this case, these operations are expected to
reduce available feedstock quantities to about 6,182 tons per year.
Equipment manufacturers' performance specifications project an efficiency
rating of 95 percent at 5 tons per hour. Using a conservative approach, the
SWA estimates an 85 percent recovery rate for flint. Applying these
conservative assumptions, the proposed project would produce 5,255 tons per
year of finished flint available for marketing.
In South Florida, color- sorted flint glass has a current market value of $25 to
$30 per ton, net shipping. At current market value, the proposed project will
generate between $131,375 and $157,650 per year from the recovery of an
additional 5,255 tons per year of flint. At this rate of cost recovery, grant funds
will be recovered in less than two years ($213,050/$131,375) and total project
costs will be recovered in about 2.5 years ($339,045/$131,375).
The cost recovery projections summarized above contemplate recovering only
flint glass. During seasonal lows when reductions in available feedstock
create excess MRF capacity, it may be practical to reprocess the remaining
portion of the mixed cullet stream to color-sort amber and green glass. While
market values for amber are less attractive than for flint, color-sorting the remaining
fraction would generate additional market revenues and reduce MRF residues.
The entire budget for the proposed project is earmarked for capital improvements
with a useful life of ten years or more, Given the relatively short time needed to
recover capital costs, the proposed project represents an economically attractive
investment. The project will not only improve long-term glass recovery for the SWA
but will also demonstrate the economic viability of optical glass sorting technology
for other jurisdictions in Florida.
Advanced Technology or Process
Processing glass to produce a color-sorted, contaminant-free product has
historically been an extremely labor intensive process. As glass prices drop, many
jurisdictions can no longer afford to collect and process glass. Despite' the
popularity of plastic for packaging, glass products still represent a significant portion
of the potentially recyclable materials and glass recovery remains an important
state-mandated objective. The successful application of optical sorting to glass
processing promises the opportunity for greater recovery at a significantly lower
cost and, thus, sufficient economic incentive for increased glass recovery.
Optical sorting represents an advanced technology that is not in common use on a
statewide basis in jurisdictions of similar size or demographics. This 'high tech"
optical scanning technology is the result of many years of scientific research and
development, and its introduction into glass processing applications has been made
possible by refinements and incremental improvement in optics and computer
technology. Optical sorting technology has only recently become commercially
available in the United States, where it was initially applied to plastics processing.
Recent advances in screening and metering equipment have been instrumental in
the development of commercially viable systems with the capacity to produce
property cleaned and sized material for processing in the system. Processing
capacity of the optical sorting system has improved dramatically, and current
technology can process up to 5 tons per hour of mixed broken cullet, a capacity
sufficient to handle volumes generated at any Florida MRF.
The application of optical sorting technology to this particular industry segment
represents the most exciting innovation in glass processing since the inception of
Widespread municipal recycling. By any industry standard, optical glass sorting is
the most advanced technology available to the recycling industry today. The
proposed project offers the SWA the opportunity to introduce this advanced
technology to municipal recycling in Florida and to demonstrate that this technology
can improve the economic viability of glass recycling for other Florida jurisdictions.
Targeted Material
Mixed glass cullet is a promising material for innovative recycling technology and is
a material category targeted by DEP. Glass recycling has been widely accepted,
and glass has been a popular part of most municipal recycling programs for nearly
ten years. All the necessary elements of a successful recycling effort are in place.
But despite wide public acceptance and a highly developed infrastructure for using
recovered glass, most jurisdictions in Florida and across the country struggle to
reach 20 to 30 percent recovery rates.
The reasons for these disappointing recovery rates can be traced to the collection
systems used to collect commingled containers. For example, in Palm Beach
County commingled containers are transferred at least three times during a typical
collection day. The result of all this handling is the production of large amounts of
mixed broken cullet less than two inches in diameter. Traditionally, this material has
little or no market value. Since mixed cullet cannot be used for glass manufacturing
and cannot be cost effectively sorted, it is usually crushed for use as aggregate
substitute or disposed of as residue at a cost to the MRF operator.
For the SWA, mixed broken cullet represents nearly 30 percent by weight the
commingled fraction and, therefore, a significant loss of resources and revenue for
our program. The SWA has explored numerous alternative uses for mixed cullet
including glassphalt manufacturing, as an abrasive in sand blasting, and as
decoration in the production of outdoor tile. The SWA has been unable to develop
any of these alternative markets to the extent necessary to handle' the quantity of
material being generated. The apparent lack of solutions to breakage on the
collection side, the unavailability of alternative markets for mixed cullet, and the
steady demand from end markets for color-sorted material led the SWA to focus on
a MRF based solution.
Of the mixed cullet generated by the Palm Beach County program, 60 percent is flint
glass, with the remaining 40 percent being comprised of nearly equal parts of amber
and green glass. Implementation of the proposed innovative optical sorting
technology will enable the SWA to recover the more valuable flint glass and to
significantly reduce the amount of material that must be disposed of. In the event
that market values improve, amber glass can also be sorted and recovered for
resale.
By demonstrating the operational feasibility and economic incentives offered by this
technology, the proposed project will serve as a model for improving mixed cullet
recovery rates in the State of Florida.
Technology Transfer
The optical sorting technology being proposed for use at the SWA MRF is compact
and can easily be retrofitted to most MRF configurations in general use today. The
system requires minimal ancillary equipment, and operations can be made relatively
simple, usually requiring only one operator with minimal training. These factors
combine to make this technology easily transferable to many jurisdictions and
adaptable to multiple applications. .
The SWA is fully committed to the concept of technology sharing fostered by DEP
through the Innovative Grants Program. If the proposed project is fully funded, the
SWA is prepared to share information concerning system design and to compile
detailed records related to system implementation, operation, and maintenance
costs.
To promote the process of technology transfer, the SWA will carry out an extensive
public education and information program. The MRF will offer tours for the general
public as well as for various professional associations and other governmental
agencies. The SWA will feature the proposed project as a segment on our “Waste
Matters” program aired on Palm Beach County public television. The SWA also
commits to make at least one formal presentation of the project to a State or
national workshop within one year of installation of the proposed optical sorting
system.
With completion of renovations to the MRF, the Palm Beach County Residential
MRF expects to handle more residential recycling tonnage than any other MRF in
the State of Florida and in the nation. This distinction will certainly spark the notice
of the recycling industry and will generate significant attention for the proposed
project. In addition, the manufacturers of the optical sorting system are eager to
develop a presence in the southern US and will be instrumental in promoting the
transfer of this innovative technology throughout Florida and the nation.
Regional Approach
As one of the leading municipal recycling programs in South Florida, the SWA of
Palm Beach County has always worked with our neighbors to bring new recycling
initiatives to our region. The proposed project is an opportunity to continue this
regional approach.
The SWA currently accepts commingled containers from Martin and St. Lucie
Counties to the north and from Okeechobee County to the west. This cooperative
effort allows smaller programs in neighboring counties to share the economic
benefits of a larger scale facility. Because the proposed project represents a
regional approach to recycling, this project offers the opportunity to improve glass
recovery rates and increase recycling revenues for four participating counties.
Following implementation of the proposed optical sorting technology, the SWA will
cooperate with interested parties in the region to promote the use of this technology
at other facilities. Once the operational effectiveness and the economic viability of
the technology have been established, the project will serve as a model for other
large programs in South Florida that could also serve as regional processing
facilities.