H. Lanier Hickman Jr.

Part 10a: Resource Recovery: Materials, Energy, or Both?

Links to other parts of our series may be found at the end of this article.

By H. Lanier Hickman Jr.

The terms recycling, waste-to-energy (WTE), and resource recovery were not a common part of our terminology until the 1970s, although they began to appear in the late 1960s. In 1970 Congress passed the Resource Recovery Act (RRA); the name alone focused the nation on part of solid waste management and defined resource recovery: the use of solid waste, otherwise destined for disposal, as both an energy source and a source of secondary materials.

The schism that exists today between the believers in recycling and WTE did not exist at the passage of the RRA. That split began sometime in the 1980s and can be attributed to the efforts of some of the more extreme environmental groups and the policy shift in the United States Environment Protection Agency (USEPA) that resulted in abandoning combustion as a method of MSW management. In the time before this split became serious. considerable investment was made by the US Public Health Service (USPHS) and its successor agency, EPA, in both sides of resource recovery. Those investments were focused on developing technologies to recover those materials most suitable for recovery, to use the combustible fraction as an energy source, and to landfill whatever remained.

Part 10a is titled "Resource Recovery: Materials, Energy, or Both?" in an effort to refresh or inform readers that WTE and materials recovery from MSW have a history of compatibility that we have forgotten. Part 10a examines the early practices of salvage and reclamation and the efforts to develop processing equipment to prepare MSW for both materials and energy recovery. Part 10b examines materials-use policies and source separation of materials, primarily from residential solid waste, since the recycling from that wastestream has fueled the exponential growth of recycling in the 1980s and 1990s.

This has been a difficult part to write because of the schism noted above and because of the complexities of resource recovery and conservation. Finally, the evolution of recycling has not been documented to the depth that this important part of integrated solid waste management deserves.

Resource Recovery

A wide variety of salvaging and reclamation went on during the first half of the 20^th century. Perhaps the most prevalent practices included rendering plants that removed dead animals as well as rejected foods and foodwastes to manufacture glycerin, oils, fertilizers and animal hides. Feeding pigs garbage was a bit deal too. The junk, or rag, man (early door-to-door recyclables collection) was well known in the streets of many cities (photo 1). But most public works officials of local government with responsibilities for refuse collection and disposal did not invest in recycling because of the fluctuating and sometimes nonexistent markets.

However, many cities attempted to make salvaging and reclamation a part of everyday refuse management. Rags, tin cans, bottles, and rubber were the materials of choice during the first half of the 20^th century. Plants that we now call material recovery facilities (MRFs) existed then and, as now, many relied on manual sorting to divert various materials (photo 2). New York City made a bold effort in the late 1890s and well into the 20^th century to have its citizens separate their solid waste. Glass bottles, steel cans, cardboard, rags, and felt hats were removed and sold. Curbside diversion of recyclables actually began during World War I, and the pushcart scavenger was born. But the evolution of the containerized compaction collection vehicle and the landfill created systems that did not support recycling.

All of us have heard stories about - and some of us remember - the really big recycling efforts that occurred during World War II. As part of a national commitment, materials had significant value for the war effort, and it was the patriotic thing to do. But as soon as WWII ended, the trend toward sanitary landfills and larger collection vehicles picked up where it been pout on hold when the US joined the WWII conflict. As the end of the 1960s arrived, most local governments with responsibility for refuse management continued to resist investing heavily in salvaging and reclamation primarily for a lack of assured markets.

The federal solid waste program of the USPHS, beginning in the late 1960s and early 1970s, was a key factor in the awakening of the American public to the need for adding recycling to the menu of methods for managing solid waste. The US Bureau of Mines (BuMines), drawing on its experience in minerals and materials processing, also began to support research on the recovery of materials from MSW (urban ore). The first Earth Day, in April of 1970, focused the attention of the American public on environmental issues that before were of little interest to them. It became clear that the WWII war effort, the explosion of the American economy after WWII, and the heavy urbanization of the population had occurred at a significantly high cost to the quality of public health and the environment. Public policy began to develop to respond to both a perceived and an actual need to change the way the US managed refuse.

The passage of the Solid Waste Disposal Act provided for the first time funds for the BuMines to support research to study recovering materials from MSW. Of particular note is the BuMines work to develop a procedure for physical beneficiation of metal and minerals in MSW incinerator residue. The National Center for Resource Recovery (NCRR), a privately funded research organization established in 1970, initiated research efforts in the area of front-end processing of MSW to recover materials and develop fuel for MSW incinerators. The NCRR, American Society of Mechanical Engineers, USPHS/EPA, and BuMines support led directly to the development of American Society for Testing and Materials (ASTM) standard specifications and methods for the recovery and preparation of a number of materials from the MSW stream. A need for standards for sampling, analysis, and production of materials was necessary to help processors of MSW develop acceptable products to the secondary materials marketplace. The BuMines did not stay heavily invested in MSW management beyond the early 1980s. NCRR, after some remarkable work, ceased to exist around 1981-1982. The ASTM Committee E-39 completed the majority of its work by the mid-1980s. This was around the same time as a shift away from processing in favor of mass-burn combustion technologies and source-separated materials from various parts of the MSW stream.

From 1965 until the early 1980s, the largest investment in money and human resources directed at resource recovery came from the USPHS and its successor, EPA. Issues such as packaging, recycling measures for newspapers, paper products, aluminum, glass, tires, and plastics were studied; reports were issued; and the national debate on how to recover these materials from MSW truly began. With resource recovery as the goal, mechanical approaches to processing MSW to divert specific materials were given special attention.

Trying to Find Processing Equipment

Efforts to understand, develop, and enhance the mechanics of processing solid waste for recycling was a comfortable step for the USPHS/EPA. The US has always been an "at the end of the pipeline" culture when it comes to waste management, be it liquid, gas, or solid. Moving up the pipeline to look at nonmechanical means of addressing a problem is less of an American characteristic.

A pioneering study that began during the early years of the new USPHS program and was completed after the formation of EPA was a comprehensive study of the recovery and utilization equipment that might be used to recover materials from the MSW stream (Drobny, 1971). The study, done by Battelle Memorial Institute, reports the state-of-the-art around 1967-68 and investigated existing and promising technologies for size reduction, separation, recovery, and utilization (composting, heat recovery, chemical conversion, fly ash utilization, and salvage).

This study concluded that other than the recovery of tin cans (because of the ease or recovery by magnetic means), the salvage of other materials from MSW was limited. There were several reasons for this conclusion: the relatively adequate supply of virgin materials and the corresponding low cost of the virgin materials that the salvaged components would replace or conserve, the high quality demanded by manufacturers that would use recovered materials for recycling into manufacturing operations, and the lack of separation technology to meet these quality requirements. It is interesting to note that the impediments identified in 1971 of recovering and selling materials from the MSW stream are still with us in the third millennium:

• The costs of virgin materials frequently remain cheaper.
• Quality requirements by buyers of separated materials are often very difficult to meet.
• Mechanical equipment, while improving, still needs development.

Equally important, this work provided early descriptions and analysis on equipment in use in various materials processing applications but that had not been tested to process MSW. The researchers concluded that hammermills were probably the most effective means to reduce MSW. Other equipment examined for sizing, separating, and so on - except for magnetic separation of ferrous - were unproven for MSW without considerable research and development. Figure 1 illustrates a variety of crushers, mostly used in mines and quarries. Of these, the impact crusher, a variation of hammermill technology, was considered the most applicable to MSW size reduction. Wet pulpers were also evaluated, and it was concluded that they might work best in compost plants. Figure 2 shows the basic components of a wet pulper. Hammermills were considered to have the widest application to MSW. Figure 3 includes the basic components of a hammermill (still the same basic designs in 2002).

The Battelle study investigated separation technologies too. The report noted that, as of 1968, the most widely used means of separating solid waste was handpicking and sorting from conveyors. The most prevalent usage of separation was in compost plants that existed around the US at that time. Photo 3 is an illustration of a handpicking station at the Lone Star Organics composting plant in Houston, TX. The researchers concluded that handpicking was not cost-effective for large-scale MSW plants.

It is easy to understand, therefore, the early commitment to developing improved mechanical equipment to ease the separation of recoverable materials in the MSW stream.

Mechanical separation technologies that were examined included magnetic separation, eddy-current separation (for nonmagnetic metals), and sizing and separating equipment including vibrating screens and tables, spiral classifiers, flotation, fluidized beds, optical sorters, and inertial separators. From their work, the researchers concluded that any of this equipment, which had operational experience with other materials, might be applicable to MSW, but until actual research was done, it was impossible to determine which would have direct applicability. The information gained from the Battelle work was reflected in the investments made by the federal program for future research efforts on both the supply side and the end of the pipeline processing.

This early work stimulated increased investment in developing processing equipment for MSW. Investments by the USPHS/EPA, NCRR, and a variety of private-sector companies were significant from 1970 to 1985. Understanding the mechanics of magnetic separators, eddy-current devices, and flotation methods are clearly reflected in the design and construction of the MRFs of today. Refuse-derived-fuel plants in the US today are a direct result of the early and later work by USPHS/EPA, NCRR, and the Department of Energy on processing techniques. Tracing a direct lineage is difficult, but it is there.

References

APWA. Municipal Refuse Disposal. American Public Works Association. Chicago, IL. 1961.

Drobney, N.L. et al. Recovery and Utilization of Municipal Solid Waste. Publication SW-10c. US Environmental Protection Agency, Washington, DC. 1971.

Hickman, H. Lanier Jr. The Complete Handbook on Solid Waste Collection and Transfer. American Academy of Environmental Engineers, Annapolis, MD. 2000.

H. Lanier Hickman Jr., P.E., D.E.E., is a member of MSW Management’s Editorial Advisory Board.

To read the other parts in this feature please click on the relevant links below:

Part 1: Introducing the Pioneers
Part 2: Of Mosquitoes, Flies, Rats, Swine, and Smoke
Part 3: The Sanitary Landfill
Part 4: Building a National Movement
Part 5a: Building an Infrastructure
Part 5b: Building an Infrastructure
Part 6: Collecting Solid Waste/No Longer Beasts of Burden
Part 7a: Landfill Gas Odors/Fires, Explosions, and Kilowatts
Part 7b: Landfill Gas - An Asset, Not a Liability
Part 8: Composting: Sometimes a Good Idea Does Not Sell
Part 9a: The Awakening of Waste-to-Energy in the US
Part 9b: A Reverse Marshall Plan