Plastics, Rubber, and Paper Recycling - ACS Publications

Chapter 2

Curbside Recycling Infrastructure: A Pragmatic Approach 1

2

Plastics, Rubber, and Paper Recycling Downloaded from pubs.acs.org by UNIV LAVAL on 07/11/16. For personal use only.

Raymond G. Saba and Wayne E. Pearson

1Center for Plastics Recycling Research, Rutgers, The State University of New Jersey, New Brunswick, NJ 08093 Packaging Research Foundation, P.O. Box 189, Kennett Square, PA 19348 This chapter describes a pragmatic view of the current curbside recycling infrastructure for reclaiming polymersfromthe post-consumer solid waste stream. It concludes that the infrastructure is not economical, and it describes a future scenario by which technology improvements could achieve viable economics.

Plastics recycling is an important aspect of a much broader issue that our society is attempting to understand called "sustainable development", that is, the rate of growth of development in products and services that can be sustained by an environment and its resources. While innovation in products and services has created our high standard of living, it is prudent that we develop the necessary understanding to provide the environmentally sound management of the resources which sustain our society. Plastics recycling, through numerous technologies, is being investigated for its potential contribution to developing such an approach. Polymers are a relatively new material to our product world when compared to glass, metal, paper and clay-based materials that have a history of several thousand years. The demands of the mid-20th century war operations accelerated the development and use of these relatively new materials because of their unique capability to be customized for specific end uses. Polymeric materials offered unique advantages through their inherent light weight, their broad range of properties related to strength, durability, moldability and colorability, as well as through their relatively low energy requirements in converting resin to manufactured product. Whether as virgin materials, blends, alloys or composites, polymeric materials provided a quantum leap forward in products and services to our society and the world. Every advanced culture in history is distinguished by the sophistication of both the materials and tools developed for its products and services. Polymeric materials, as the newcomer, has been able to greatly enhance that sophistication over a relatively short span of 50 plus years. 0097-6156/95/0609-0011$12.00/0 © 1995 American Chemical Society

12

PLASTICS, RUBBER, AND PAPER RECYCLING


The 1993 sales of virgin polymers were approximately 70 billion pounds. About one third of the material was used for packaging and transportation, relatively short-life products; the balance was used for construction, furniture, appliances, electrical and other longer-life products (7). Interestingly, the recycling of plastics scrap is nearly as old as the manufacture of virgin polymers themselves, however the practice stemsfromthe economic need to achieve maximum material utilization efficiencies. In large part, this is viable because approximately 90% of the virgin polymer production is thermoplastics (2), that is, capable of being molded or formed into a final product by the application of heat and pressure. As a consequence, rejected product (or related trim and scrap) in a molding operation has the potential to be recycled back into the molding process to produce a product that meets virgin specifications. The total quantity of in-plant recycling (preconsumer), considering the polymer, intermediates andfinishedproduct, is estimated to be about 4 billion pounds per year (5). This recycling know-how provides a valuable technological cornerstone for the post-consumer recycling challenge. Post-consumer plastics recycling, as an environmental issue, received recent national attention primarilyfromthe public's concern about solid waste disposal. This concern was more focused on plastics through the public's everyday interaction with the plastics packaging discards entering the municipal solid waste (MSW) stream from consumer products. In 1993, over 34% by weight of the total MSW was containers and packaging materials, of which plastics represented 12% or 16 billion pounds

A quite significant change has occurred in the management of MSW from 1985 to 1992 (5)(See Table TABLE 1 1). Although MSW has grown 24%from164 million MUNICIPAL SOLID WASTE METHODS OF DISPOSAL tons to 203 million tons, 1992 1985 there has been a significant 164 203 Total M S W (Mil. Tons) shift awayfromlandfilling, 21% 10% Recycling the traditional means of 16% 5% waste disposal, to recycling Energy Recovery and energy recovery . Re63% 85% Landfilling / Incineration cycling, including composting, has doubled to 21%, and energy recovery has tripled to 16% . Post-Consumer Polymer Recycling Process Recycling post-consumer polymers is a tremendous challenge, economically as well as technically. Economically, the objective is to sell "trash" to someone, since post-consumer solid waste is "trash"froma general viewpoint. Technically, the challenge is to process the trash into quality raw materials that can be manufactured into products having acceptable value to a buyer. In total scope,fromthe processing of the

2. SABA AND PEARSON

Curbside Recycling Infrastructure

13


waste plastics to the development of markets for the recovered polymers, it is a challenge comparable to establishing a whole new industry. The raw material source, municipal solid waste (MSW), contains literally thousands of potentially recyclable items, although few are being recycled. Currently, the ten most commonly recognized items commercially recycled today are newspapers, corrugated paperboard, aluminum and steel beverage cans, tin cans, three colors of glass bottles, PET soft drink bottles and HDPE milk, water and juice bottles. The aluminum and PET beverage containers were added to the list in the past two decades, and very recently, the HDPE beverage container has been included. However, with this embryonic recycling infrastructure, few other materials in the MSW have the economic viability for recycling. Despite the fact that only the top ten items in the trash are technically and economically viable, a substantial infrastructure for recycling has arisen. There are two major reasons for this occurrence. First, the markets for the reclaimed post-consumer beverage containers and newspapers are huge and well established, so when the quality, availability and price of the reclaimed materials are acceptable, they can compete effectively either as substitutes for, or as complements to, virgin materials. The second reason is the willingness of homeowners to subsidize the recycling infrastructure by providingfreelabor through the cleaning, sorting and curbside set-out of the recyclable itemsfromtheir trash. Although the curbside collections only amount to about 2.5 % by weight of the MSW (6), the uncrushed beverage containers and the newspapers make up half of the volume of their trash, when yard waste is excluded. Thus, homeowners are reinforced in their belief that, through recycling, they are making a worthwhile contribution to the environment. Compared to newspapers and non-plastic beverage containers which have been recycled for decades, the recycling of plastic beverage containers has had significant growth in less than a decade. This is shown by the rapid increase in the number of collection programs, TABLE 2 material recovery facilities GROWTH IN INFRASTRUCTURE & MARKET (MRF's), plastics reclamation FOR RECLAIMED POLYMER plants, and the end-use markets Year 1 9 8 5 1 9 9 3 for the reclaimed polymers (See Table 2). # of Collection Programs 9400 0

# of MRF's

0

198

# of Reclamation Plants

3

337

PET (Mil. lbs)

100

448

HDPE (Mil. lbs)

25

450

Source: American Plastics Council

Adding to the legitimacy of the embryonic plastics recycling industry, a pilot project has been initiated to make recycled PET and HDPE two of the first recycled commodities electronically traded on the Chicago Board of Trade (7). In addition,

14



the Center for Plastics Recycling Research (CPRR) at Rutgers University is working with American Society for Testing and Materials (ASTM) to develop national standards for recycled resin (8). Yet, when we consider that the one billion annual pounds of post-consumer plastics, principally beverage containers, being recycled today represents just 3.5% of the total amount of plastics in the MSW (9), we realize that we have successfully resolved only a small part of a much larger problem. Beyond beverage bottle recycling we see the problems as exponentially more complex, in technical content and in relation to broader environmental, economic and social issues. Beneath the top ten items are hundreds, thousands, and ten of thousands of other items: different types of paper, glass, metal, plastics, and combinations there of, that are even farther below the technological and economic thresholds. Yet, these problems are receiving increasing attention, and there are already numerous technologies and strategies being developed that show great promise. The remainder of the chapter will describe these problems and some of the potential solutions for recycling the balance of plastics in the MSW. Markets For Plastics Derived From Trash Potentially, there is a large variety of polymeric products that can be reclaimedfromthe trash, and therefore, setting aside technical and economic considerations for the moment, the potential physical market opportunity is as large as the existing market for virgin polymers. The target markets for these materials depend on the types of products that can be derivedfromtrash. Three general classifications could be described as: 1) chemically purified monomers and polymers, 2) mechanically separated polymers (such as PET, HDPE and PVC from beverage containers), and 3) commingled or mixed polymers. Chemically Purified Monomers And Polymers. Such materials can be defined to a very high level of purity. Usually, any impurities will be measured at levels of less than 50 parts per million (99.995% pure). The markets for materials at the molecular level are huge and established. These are the markets that are already in place for virgin monomers and polymers. Therefore, there is little problem identifying the markets and the buyers for annual multi-billion pound quantities, i.e., for chemical monomers, such as ethylene and propylene. Performance can be judged by matching specifications. The only questions that must be answered for the buyer before there can be a commercial transaction, or sale, relate to price and availability. Mechanically Separated Polymers. These polymers, on the other hand, will probably have a substantially higher level of contamination than the virgin competitive material. Therefore, specifications have to be changed before a sale or substitution for a generic virgin material can take place. This can be time consuming, and it usually requires a real-life performance test before a buyer will agree to begin negotiations on price and availability. Therefore, it will take more time to persuade a buyer to

2. SABA AND PEARSON


15

purchase the generic polymer, and the selling expense associated with making the sale for this type of product will be higher than that associated with a monomer.


An example of a quality problem is the contamination of PET with PVC and, visa versa, the contamination of PVC with PET. Either polymer is difficult to fit into existing uses if the contamination with the other polymer exceeds 50 parts per million. The difficulty in selling contaminated polymers is a reflection of this phenomenon. The potential markets for clean generic polymers are huge because the markets for the virgin generic polymers exist and are huge. So, it is reasonable to expect that it will be possible to penetrate those markets in a reasonable period of time. Commingled Or Mixed Polymers. Mixes are orders of magnitude more difficult to describe. The problem is that it is very difficult to define a mixed material in any terms except what it does. For example, "plastic lumber" could replace wood or concrete in certain applications, but it does not yet have the industry-accepted specifications as do wood and concrete. Therefore, it takes a very long time to prove to a potential buyer that such a new product will be a satisfactory replacement. Also, it can cost a considerable sum of money to run the experiments to prove the worth of the new product. In other words, the markets for mixed plastics do not exist per se as do the markets for monomers and generic polymers. These markets must be created. Consequently, there is much elapsed timefromthe initial contact with the potential buyer to when an actual sale is consummated. This greater time is reflected in higher selling expenses associated with the commingled product than with the generic polymer. The Problem: Current Recycling Technology Is Too Expensive The issue that looms largest to restrict the amount of material that can be divertedfromthe trash through recycling is that the current systems in practice for collection, sorting and reclamation are too costly, mainly because they are small in scale and extremely labor intensive. About 59% of the cost of recycling is in the collection and the sorting (70) TABLE 3 prior to the reclamation of the polymers (See Table 3). COSTS TO RECLAIM POLYMERS IN FLAKE FORM' 101

l/lb

%

Collection

10

(27)

Sorting

12

(32)

22

(59)

15

(41)

37

(100)

Subtotal Grinding/ Cleaning Total

An examination of the components of the recycling methodology in practice today will help to explain why it is so expensive. It will also be used to indicate where changes can and must be made to improve the efficiencies and the economics of the process.

16


There are four parts of the post-consumer recycling system, namely: collection, sorting, reclaiming and marketing. Recycling does not occur unless each of the four parts is completed. The typical recycling infrastructure in place today includes:


• • • •

Curbside Collection of Commingled Recyclables Sorting at a Materials Recovery Facility (MRF) Reclamation of the Polymers Marketing of Products

Collection. Collection options currently available to communities are voluntary drop-off, buy-back and curbside collection. Curbside programs are expensive, but they capture the most material (See Table 4). Typically, a municipality will have several recyclables picked up at the curbside. These include: • Newspapers and Corrugated Cartons

• Aluminum and Steel Cans • Glass Bottles and Jars

These containers are then emptied into a collection truck and transported (uncompacted) to the materials recovery facility. Homeowners have shown TABLE 4 a willingness to cooperate in Collection Methods/Recovery Rates these curbside recycling proCollection Methods Recovery Rates grams. However, the more convenient it is for them to separate (%) the recyclablesfromthe rest of 10-15 Voluntary Drop-Off the garbage, the greater their par15-20 Buy-Back Centers ticipation and the higher the re70-90 Curbside covery rate. Recognizing this, many communities are collecting Source: Center for Plastics Recycling Research all the recyclables commingled in a single container. TABLE 5 CAPTURE RATE BY PACKAGE TYPE

Item

% Capture

Beverage bottles

65

Detergent bottles

50

Other rigid containers

10

Film

5

Average of All Plastics Source: Center For Plastics Recycling Research

30

The public will deliver to curbside programs easy-to-identify, easyto-clean plastics packaging materials such as beverage bottles and, possibly, detergent bottles (see Table 5). After that, the public's enthusiasm for digging deeper into the trash appears to wane, and the rate at which they deliver materials declinesfroma high of 65-70 percent for plastic beverage bottles to 5-10 percent of other containers and film packaging.

2. SABA AND PEARSON


17

In other words, the "free" sorting labor in the home only captures 30 percent of the plastics, resulting in high collection costs (See Figure 1). By contrast, "conventional" trash collection captures 100 percent of the recyclables, and it is low cost. In short, the new curbside collection method to collect recyclables has a higher labor cost and captures only afractionof the recyclables. In contrast, the conventional method of trash collection is very low in labor cost and captures all the recyclables. Collection Cost vs. Capture Rate


Cost S/Ton

3 0

% Capture

1°°

Source: Center for Plastics Recycling Research

Figure 1. Collection Cost vs. Capture Rate.

Sorting. The second required component of the recycling system is the separation of the collected materials, which are subsequently processed to meet the purchasing requirements of the material reclaimer. Material recovery facilities (MRF's) are being built at the 100 to 500 ton per day capacity to take the commingled recyclables from curbside collection systems. On arrival at the MRF (Figure 2), the commingled materials are dumped onto the "tipping floor". There the newspapers are separated from the containers, and the containers are then pushed with afront-endloader onto a large conveyor belt. The steel and aluminum containers are removedfromthe glass and plastics by two different types of magnetic separators. Because of the density differences, the glass is easily separatedfromthe plastic. From there, the glass containers are hand sorted by color (clear, brown and green) and the plastics are handsorted into Materials Recovery Facility (MRF) RECYCLABLES

MAGNETIC | SEPARATION

| NEWSPAPERS!

STEEL CANS

EDDY CURRENT

1

ALUMNUM CANS

1

CLEAR GLASS

4

BROWN GLASS

4

GREEN GLASS

4

4

CLEAR 1 PET |

1™

4 1 ™

1 GREEN

Source: Packaging Research Foundation

Figure 2. Materials Recovery Facility (MRF).

18


the different types of plastics bottles (PET soda, HDPE milk, water and juice, HDPE detergent, PVC water and PP ketchup, etc.). The separated materials are then baled and shipped to reclaimers.


Reclamation (Plastics). The bales of plastic bottles received by the reclaimer from the MRF are processed to a polymer resin through the following steps: • • • • • •

Bale Breaking Sorting The Bottles Chopping and Grinding The Bottles To Flakes Washing The Flakes Separating Different Polymers As Flakes Melting the Flakes to Produce Pellets

The plastic bottles that may be separated include: • • • • • •

Clear PET Soft Drink Bottles Green Soft Drink Bottles Translucent HDPE Milk, Water and Juice Bottles Pigmented HDPE Detergent Bottles PVC Water Bottles All Other Materials

Some reclamation PET plants are reclaiming non-soda PET bottles and containers, but many are not yet equipped to deal with either the slightly different polymer types or the content contaminants which usually have a higher chemical oxygen demand (COD) and biological oxygen demand (BOD) than the soft drink and juice residues left in discarded beverage bottles. This extremely expensive recycling infrastructure, beginning with curbside collection, sorting at the MRF, and resorting at the reclamation plant, must compete with the well established, highly automated, large scale, capital intensive, minimum labor content technology for gathering virgin raw materials, for producing product from the virgin materials, for distribution of the products and for disposal of the products. The basic building block chemicals manufactured at the refinery are converted to polymers in enormous, capital intensive polymer plants ranging from 100 million to 1 billion pounds per year. By contrast, the current technology for recycling the top ten items in municipal solid waste is inefficient and costly. It involves curbside pick-up in expensive trucks that require much labor to operate. This results in a cost of collection for recycling that can be 3 to 5 times higher than the cost to collect trash. Moreover, current curbside collection captures only about one third of the recyclables, and it is subsidized by thefreesorting and handling of the households.

2. SABA AND PEARSON


19


Moreover, the trash disposal system developed in the United States is very efficient and low cost because it, too, is capital intensive. Modern waste management has permitted the last human hand to be removedfromtouching garbage. The latest concepts use a single operator truck. A robotic arm on the truck picks up as much as 100 gallons of trashfromthe curbside and deposits the material into a compactor truck. The compactor truck densifies the material to maximize the number of collections per trip. Then, the truck drives to a landfill where the material is handled with largefrontend loaders and bull dozers, or it is deposited in an incinerator where a crane with a grapple gathers an enormous quantity and deposits it in the incinerator. Economic Realities For recycling to be economically viable, the full cost of collecting, sorting and reclaiming must be recovered. The costs of collecting and sorting are generally borne by the community, or public sector. The costs of reclaiming are borne by the private sector. The costs to the community include the costs to collect, sort, package and ship the recyclables. These costs can be offset in part or in total by the costs avoided for the collection of the material as trash and the costs avoided for alternate disposal such as incineration or landfill. The sum of these costs would be the price the community should receive for material they would sell to a reclaimer. If the reclaimer paid that price as a raw material cost, the reclaimer would have to add the operating costs for refining the material, the cost for capital and the cost for paying dividends to stockholders. With the technology that is being practiced today and with oil at $20/barrel (See Figure 3), the sum of these costs to the public and private sectors is generally higher than the costs of comparable virgin materials. However, if the virgin material is expensive to manufacture in thefirstplace, the high cost of recovering such a materialfromthe waste stream may be competitive with the high cost to manufacture the virgin material. Some plastics have such a high value. The PET in soda bottles is one example. The polycarbonate in large water bottles is another, and there are some other materials used in automobiles, airplanes and houses which would Virgin Prices have similar high valSource: Packaging Research Foundation ue. However, the majority of plastic Figure 3. Economics of Recycling, materials do not have (Oil at $20/barrel) this threshold value.

20


Economic Driving Forces.


Higher Priced Oil. An economic driving force that would make the economics of recycling more viable would be to have the price of oil increase significantly, to say, $35 per barrel. The price of virgin materials would rise correspondingly, whereas the cost of recycled materials would not rise as abruptly (See Figure 4). Consequently, virtually all polymer recycling could become economically sound. However, there is no indication that oil prices will reach these levels in the foreseeable future. Higher Alternative Disposal Fees. Another economic driving force that would make the current recycling technology become viable is if alternate disposal fees would increase. Since the Aluminim avoided cost for alternate disposal can be legitimately applied as though it were revenue, it can be determined how high these fees need to be to make the lower price polymers become viable for recycling. Virgin Prices

It can be seen that Source: Packaging Research Foundation high value items such as aluminum and PET require no Figure 4. Economics of Recycling, offsetting subsidy in the form ( $35/barrel) of an avoided tipping fee. However, a tipping fee of about $200 per ton would be required to make the low price polymers, such as LDPE, PP and PVC, become viable, and a tipping fee of about $400 per ton would be required to make it attractive to convert the polymers to the ethylene monomer. Realistically, the actual costs to build and safely operate a modern landfill or waste to energy plant are not nearly high enough to provide a driving force. 0 i la t

Designing For Recycling. A driving force that could make the current recycling technology become viable is to replace all the present materials with those that are economically viable to recycle with the current recycling technology. This logic is the basis of the simplistic form of the concept called "designing for recycling". It can be accomplished by product bans or by encouraging that products be switched from those materials that are not recycled to those that are. Consumers often interpret the term "recyclable" to mean "what is recycled now in their own communities". For a consumer products company that wishes to respond to the wants of the consumer, this suggests changing to a material that is recycled now despite the fact that the material to be replaced is technically recyclable.

2. SABA AND PEARSON


21

Some companies have chosen to switchfrompolyvinyl chloride or polypropylene to PET to have packages that are currently "recyclable". This option is both expensive and regressive. Since the replacement material is the one that usually costs the most as a virgin material, the package costs increase.


The biggest negative factor is that this approach causes a virtual abandonment of packaging innovation. New products and product concepts would be forced to fit the current recycling technology and infrastructure, which has not kept pace with the development of packaging technology. Legislation Mandating Recycle Content. A fourth economic driving force that could make the current recycling technology become viable is to pass legislation that mandates products to use a prescribed percent of recycled material. Companies would have to choose either to abandon the product or to pay whatever is required to incorporate the recycled material in their products. In this case, the supply and price of virgin material have no bearing on the decision. The price can be higher than virgin, and the substantial increase in price that would be permitted by this legislation would allow materials, which ordinarily could not compete with virgin materials, to become viable instantly. Many states and municipalities are passing or are considering passing such legislation. While this will accelerate recycling, it will be inflationary and will result in higher prices. Technology To Reduce the Cost Of Recycling. The preferred economic driving force is one that reduces the cost of recycling plastics to make such materials competitive with their virgin counterparts (See Table 6). This will require a new research approach to achieve TABLE 6 the goal of recycling 25% - 50% of the plastic disPOLYMER RECYCLING - CURRENT & GOAL COSTS (0/LB) cards by the late 1990's. Current Goal As goals, the cost to col2.5 10 lect recyclables should not Collection exceed the cost to collect Sorting 12 5 trash, and the cost to sort 15 Grinding/Cleaning 15 should be offset by the 22.5 37 Subtotal revenuefromthe sale of high quality sorted materi- Landfill Avoidance ' 4 4 als plus the avoided cost 18.5 33 Total * of their disposal as trash $80.00/ton Under these conditions, the costs of collecting and Net with revenues sorting could be reduced Source: Packaging Research Foundation by nearly 65%, which should make the recycled polymers competitive with virgin materials. 1

2

11

2)

22


Energy Savings. The most widely used plastic in packaging is polyethylene, with an inherent (caloric) energy content of more than 23,000 Btu/lb. This is about the energy content of the crude oilfromwhich it was produced. An additional amount of energy, used to rearrange the atomic structure of the molecules (monomer to polymer), can be called conformational energy. Recycling uses the already (con)formed polymer, rather than new crude oil, through technologies that require less energy than the original conformational energy, so that the inherent (caloric) energy content and some of the conformational energy can be saved.


Emerging Technologies As mentioned, collection and sorting costs are too high to meet the economic realities of the market place (See Table 7). Consequently, communities and reclaimers are experimenting with a number of technologies to reduce these high costs. Alternate methods of collection include: curbside co-collection of trash and recyclables (uncompacted), collection of all recyclables in a compactor truck, and collection of all trash in a compactor truck. Each of the collection methods has advantages and disadvantages. TABLE 7 COLLECTION METHODS - ADVANTAGES & DISADVANTAGES

Method

Advantages

Disadvantages

Curbside Recyclables

Easier for MRF

High cost Unasked for materials Low recovery rates

Co-collection

Lower cost

More difficult for MRF Unasked for materials Low recovery rate

Collect all trash

Lowest cost Highest recovery rate

Very difficult for MRF

Source: Packaging Research Foundation

To reduce the cost of sorting, the MRF's and the reclaimers are experimenting with automated sorting technologies to replace expensive manual sorting. A few commercial installations are operating which can separate the major beverage containers, PET, HDPE and PVC, and the newest versions have the capability to separate plastic bottles and plastic chips by color. In effect, these new technologies replace labor with capital. It is too early to determine what the economic advantages are, and it is not clear whether the quality of separation per pass of either method is superior. The challenge is to develop the lowest cost of collection that captures the maximum amount of clean recyclables while not making it impossible or uneconomical to separate the recyclables into marketable components at the MRF.

2. SABA AND PEARSON


23


Materials Recovery Facility (MRF) May Hold The Key. Since the lowest collection costs and the highest recovery rates occur in the collection of raw trash, it follows that the most commercially viable recycling system could be one where the MRF has the capability of producing viable productsfromraw trash. Furthermore, a large scale MRF is required to make recycling become commercially viable. The appropriate technology at suitable processing volumes will have to be developed. Simultaneously, greater market efforts will be required to develop the customer base. The Future MRF. A Future MRF must be designed to process "all" of the trash to obtain the maximum amount of suitable commodities for sale. This means that garbage will be the incoming feedstock. Foodstuff and product left in containers as residue or attached to films and paper will have to be acceptable to the MRF; and the MRF will have to operate with technologies that are acceptable to their neighbors. In addition, the residuefromthe MRF processing will be classed as garbage and, as such, must be disposed of as garbage. This strongly suggests that the MRF should be located adjacent to either a landfill or a waste-to-energy plant. To deal with the question of how to process raw trash requires afreshand bold approach. The goal should be to gather raw trash at the lowest cost, to transport it to a processing facility and to process raw trash into economically viable commodities in an environmentally sound manner. Research (77) suggests that ore processing technology may be applicable for the separation of the commodities in the raw trash. This technology is used in massive scale for the cleaning and separating of the minerals in ores, and it is used to clean coal. The feed for such a system is material ground into fine particles so that they can be separated in aqueous,frothflotation systems. It has been suggested by the investigator that raw trash could be comminuted and slurried in water, whereupon the recyclable resources could be separatedfromthe nonrecyclable material. The recyclables, slurried in water, could be transported by pipe lines literally hundreds of milesfromthe source of the trash to appropriately scaled processing facilities which could have the ore separation technology as a center piece of the material recovery process. With such an approach in mind, one could imagine combining the collecting and transporting of municipal solid waste in aqueous form with the transporting of municipal sewage. The resources portion of the waste would be transported by pipeline to the processing facility ("Future MRF"), and the non-resource portion of the municipal solid waste could be combined with the sewage using the same large scale facilities and technologies that are in place for converting the organic portion of our waste to sludge. The sludge, in turn, could be converted to fertilizer and mulch. New Design For The Future MRF. It is essential that the scale of the future MRF be large enough to justify automating as much of the sorting as possible to minimize costs, including transportation. The range in size of present day MRF's is only about one-tenth the size of the modern landfill and/or waste-to-energy plant (about 2000 tons per day).

24



It is also essential that the MRF be designed and operated to produce uniform and high quality products. This will require the development of a "vision" of the purpose of the MRF, and it will require a commitment on the part of the public and the MRF management to take a "long term" approach to the venture. The future MRF and its management will need to insist upon separating high quality commoditiesfromthe trash, and the materials will have to be competitive in price. In addition, the MRF management will need to recognize that they must "create" the markets. To create markets, the MRF must produce new products and price them with incentives that will attract prospective buyers. All of the skills that the private sector employs to develop and sustain markets and customers must be used. Consequently, MRF management should be prepared to fund marketing development programs upfront.This investment in the "business" to sell trash is as important, if not more important, than the investment in the hardware for collecting and sorting the trash. In the scoping of a future MRF, it would seem wise to attempt to define the products that the MRF would ultimately sell. Therefore, the first task would be to assay the trash in terms of the types of materials that could ultimately be separated. From this breakdown, it would be possible to define some types of markets and potential customers for these materials. It would also be possible to assign some tentative specifications and market prices. Further, it would be possible to determine in what form the potential customers would want to receive the materials. It would be highly desirable if the future MRF could include material chipping and then sorting of chips rather than whole items. This lends the system to automation, and it has the added advantage of producing a product that does not have to be baled to be shipped. A chipped product of plastic could be shipped by rail hopper car or by hopper truck, as virgin resins are handled today. The elimination of the bale will save money at the MRF and also at the reclamation plant. The giant challenge, of course, is that the MRF must have good enough technology and control to produce a high quality end product. The future MRF could also implement some simple cleaning of dirty materials to remove food stuffs and/or contaminants that would create effluent problems for the reclaimer. By locating the MRF at a landfill or waste to energy plant, the effluent could be readily treated and disposed. On the other hand, disposing of the effluent from a reclamation plant that is located in an urban area can be very difficult. The COD and BOD levels of the contaminants may require the reclaimer to put in a secondary treatment facility at huge capital and operating expense. Often a reclaimer is forced to shutdown because the plant, as initially approved by the public, was not authorized to handle garbage. Another potential for the future MRF is to mine materials from landfills (72). As old landfills are recycled to make room for new wastes, the mined materials could

2. SABA AND PEARSON


25

be salvaged for feedstock or fuel. Once this is realized, it is a small step for the MRF, which would be located on a landfill, to begin to store materials for future sale when the markets are more fully developed or when the price is more propitious.


The technologies that must be developed and demonstrated for the future MRF's will include methods to: • • • • • • • •

Optimize MRF sitings and the associated truck routings to the MRF Separate metalsfromthe rest of the trash Separate different metalsfromeach other Separate glassfromthe rest of the trash Separate different glassesfromeach other Separate paper from plastics Separate different papersfromeach other Separate different plasticsfromeach other

New technology for MRF's and/or reclamation plants will be required. Such technology would include: • The substitution of automated technology for manual sorting. • The inclusion of flake sorting technology. • The washing of recyclables and separation of them by hydrocyclone and froth flotation technologies. • The separation of mixed polymers by dissolution in solvents Products The Future MRF Would Make. Some examples of products the MRF might market would include, but not be limited to: • • • • • • • •

Glass for cullet (like today) Glass for fiber glass or asphalt modification High quality aluminum (like today) High quality tin cans (like today) Bi-metal products separated for specific markets Paper fiber of high quality such as bleached kraft Other plastics in addition to PET and HDPEfrombeverage containers Various commingled plastics feed stocks: • as replacements for virgin material • as feedstocks for solvent separation processes • as raw materials for plastic lumber and for refined commingled use • Various mixtures of plastics (free of chlorinated, and possibly, oxygenated compounds): • As refinery feedstocks • As hydrogen donors in coliquefaction with coal • Combinations of paper and plastics for: • Refuse Derived Fuel (RDF) • Raw material for composite board for walls and furniture

26


Acknowledgement The authors wish to acknowledge the contributions of the faculty and staff at the Center for Plastics Recycling Research, Rutgers University, with a special thanks to Jose Fernandes.


Literature Cited 1) 2) 3) 4)

5)

6) 7) 8)

9) 10) 11)

12)

Modern Plastics, Jan. 1994, vol 71 No.l pp.73-78. Reference (1). Authors' estimate. Characterization of Municipal Solid Waste in the United States: 1994 Update, United States Environmental Protection Agency, Municipal and Industrial Solid Waste Division, Office of Solid Waste, Nov. 7, 1994 (EPA 530-R-94-042), p.6. The Role of Recycling in Integrated Solid Waste Management to the Year 2000, Franklin Associates, LTD Report (Prepared for Keep America Beautiful, Inc. Stanford, CT) Summary, Sep., 1994, p.6. Reference (5), p.9. Recycling Times, Aug. 9, 1994, p.1. Morphological and Rheological Characteristics of Commercially Produced Plastic Lumber, Van Ness, K.E.; Hocking, S.E.; Washington and Lee University, Lexington, VA 24450; Nosker, T. J.; Renfree, R. W.; Sachan, R.D.; Center for Plastics Recycling Research, Rutgers University, Piscataway, NJ 08855. To be published in Proceedings of the Society of Plastics Engineers, Annual Technical Conference, May, 1955. Reference (4), p. 5. Authors' estimate Technical Report #64 Froth Floatation Recovery of Post-Consumer Plastics For Recycling, Center for Plastics Recycling Research Rutgers University, New Brunswick, N.J. (7/1/90 -6/60/92). Landfill Reclamation Strategies, Nelson, H.; Biocycle, Oct. 1994, p. 40

RECEIVED September 22, 1995

Plastics, Rubber, and Paper Recycling - ACS Publications

Recommend Documents