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The Twelve Master Categories
of Recyclable Materials

By Daniel Knapp, Ph.D. & Mary Lou Van Deventer


Designing a comprehensive recycling system requires a discard composition study. To do the study, one must observe and record what is being tossed out. Categories become important at this stage, because watching the variety of things dumped at a landfill can be overwhelming.

To pull order out of the chaos, similar things must be grouped together. But the category list is crucial; a study will see only what its categories provide for. Inadequate categories will leave a lump of unidentified residue called "miscellaneous" or "garbage." The list has to be big enough to cover everything, and small enough to be useful.

Different sizes of lists are possible, depending on one's idea of what will ultimately happen to the discards. Composition studies for incinerators often have only two categories: burnable and nonburnable. A study for a garbage composting plant might only use four of five.

How many categories are best for a total recycling system? It turns out there are twelve. (The examples after the category names are intended to suggest expansion; they are not limits by any means.)
  1. Reusable goods, including intact or repairable home or industrial appliances; household goods; clothing; intact materials in demolition debris, such as lumber; building materials such as doors, windows, cabinets, and sinks; business supplies and equipment; lighting fixtures; and any manufactured item or naturally occurring object that can be repaired or used again as is.
  2. Paper, including newsprint; ledger paper; computer paper; corrugated cardboard; and mixed paper.
  3. Metals, both ferrous and nonferrous, including cans; parts from abandoned vehicles; plumbing; fences; metal doors and screens; tools; machinery; and any other discarded metal objects.
  4. Glass, including glass containers and window glass.
  5. Textiles, including nonreusable clothing; upholstery; and pieces of fabric.
  6. Plastics, including beverage containers; plastic packaging; plastic cases of consumer goods such as telephones or electronic equipment; films and tires
  7. Plant debris, including leaves and cuttings; trimmings from trees, shrubs, and grass; whole plants, and sawdust.
  8. Putrescibles, including animal, fruit, and vegetable debris; cooked food; manures; offal; and sewage sludge.
  9. Wood, including unreusable lumber; tree rounds; and pallets.
  10. Ceramics, including rock; tile; china; brick; concrete; plaster; and asphalt.
  11. Soils, including excavation soils from barren or developed land; and excess soils from people's yards.
  12. Chemicals, including acids; bases; solvents; fuels; lubricating oils; and medicines.
Estimated and Actual Percentages of Recyclables in the Total Discard Supply
From incomplete empirical studies and countless unsystematic real world observations, we can build up a composite picture of the way the twelve master categories are probably related. This is a best guess and is not accurate for any specific locality, but it is still quite useful because it provides an overview showing that although discards viewed en masse are chaotic and physically overwhelming, they are nevertheless finite and can be accounted for.

Percentage of Recyclables in Discards
  • 25% Paper
  • 25% Plant Debris
  • 10 % Wood
  • 7% Plastics
  • 5% Reusable goods
  • 5% Ceramics
  • 5% Putrescibles
  • 5% Glass
  • 5% Metals
  • 3% Soils
  • 3% Textiles
  • 2% Chemicals
Percent Recycleables
© 1989 Daniel Knapp and Mary Lou Deventer.
Excerpted from Total Recycling: Realistic Ways to Approach the Ideal.

This generic chart lets us make these big and very useful observations:
  • Just two categories, paper and plant debris, make up 50% of the total discards.
  • About 85% of the discards are organic, carbon-based compounds.
  • The original 'Earth Day' recycling focused on post-consumer cans, bottles, and newsprint. We have not achieved total success in these categories - really subcategories - but if we did, that would give us a recycling rate somewhere between 15% and 25%.
  • From an entrepreneurial point of view, the current public preoccupation with plastics recycling obscures much more viable business opportunities with bigger potential impacts. Reusable goods, plant debris, soil, ceramics, putrescibles, and textiles can be harvested much more easily and they represent 56% of the total, compared to plastic's 7%.
  • Had the early recyclers concentrated on reusable goods - the single most valuable category per ton of the twelve - they could have tapped into a financial resource that would have stabilized and underwritten their losses elsewhere without diminishing the environmental impact of their efforts. Reusable goods are equal in volume to glass and metal, and salvaging them conserves the manufacturing energy embodied in them.
No fully operational twelve-category recycling system is currently up and running anywhere at this time. But for every one of the master discard categories, there are recycling enterprises somewhere reliably disposing of all or parts of the supply.

Recycling Reusables With Urban Ore
Just before the Berkeley landfill died, it gave birth to Urban Ore, Incorporated. Urban Ore was originally the title of a research proposal written to the National Science Foundation. We wanted to study the feasibility of digging some test holes in the landfill, recovering what we could for recycling, and composting the rest. What we were really after was not materials are all, but more space to fill while we developed a big, comprehensive recycling system on the landfill surface.

We wanted to extend the life of the landfill. The funding never came through, though, so we had to stop thinking of ourselves as scientists in lab coats. We adopted a new identity as urban scavengers.

In the wild and woolly environment of the dump, just surviving from one day to the next was a major feat. We went after reusable goods because they had more survival value than anything else. When we wanted tools, we found them in the dump. When we wanted clothes, we found them, too. When we wanted money, we sold the things we found: scrap metals, building materials, furniture, equipment, books, toys. We learned the salvage trade by trial and error, and by necessity.

We learned business so we could become established, legitimate, and recognized. We passed a major city audit when the landfill closed on schedule, we were invited to be a part of the recycling system at the new transfer station. We even prevailed in a major battle with our host public works department over an incinerator they wanted to build.

That political victory was necessary to our survival because it protected our supply. Nevertheless, it cost a lot of effort and money, and it dug a gulf between our regulators and us that took years to bridge.

We've had our ups and downs, just like any other business. But overall, we've grown and prospered. Ten years later, Urban Ore generated over $600,000 per year selling reusable goods. It employs fifteen people at wages ranging from $8.00 to $12.00 per hour. Its employees enjoy a company-paid health plan. Customers include flea-market vendors, artists, realtors, house-restoration contractors, property managers, landlords, renters, collectors, students, newlyweds, movie and theater companies, and just about anyone else looking for bargains, surprises, and sometimes just ideas.


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