Almost all material can be recycled or pyrolyzed, as discussed below.
Since waste management is typically either publicly run or highly regulated, the industry might not respond efficiently to market signals. Cities can invest directly in single stream or mixed waste material recovery facilities (MRF), which collect and sort mixed waste, diverting economically useful materials for reprocessing.
With prices of recycled commodities highly variable, municipalities should evaluate whether investment in an advanced MRF makes sense, taking externalities into account.
The way in which material is sorted and collected can have a major effect both on the public's participation in recycling and the amount of material ultimately recycled. The debate is generally between single stream recycling, which puts all recyclable material in a single bin to be sorted by the MRF, and dual stream recycling, which separates recyclables into two categories (often organic and inorganic material) at the consumer level 9. Source-separate recycling, which uses a larger number of categories, is also done.
Other studies confirm that single stream recycling is generally more expensive to sort 11 and that contamination rates are higher 12.
The cost of a material recovery facility can be partially offset by the sale of recovered materials. The following prices were observed in 2018.
The city of San Jose, California has achieved a 74% recycling rate through a franchise system, under which the city offers exclusive waste handling contracts with mandates or incentives for high recycling rates. Bidding for franchises is open to the public.
Deposit-return systems are effective tools for recovering high-value beverage containers. The system works by adding a charge on the price of beverage containers, which is refunded when the container is returned. In the United States, recovery of bottles and cans was 82% in 2002 in the state of Oregon, which has a deposit-return program. The figure is only 30% in states without such a program 14.
Here we consider the prospects for reusing material recovered from municipal solid waste.
Composting
There will almost certainly be market demand for any amount of compost that would feasibly be produced.
The average American generates almost a third of a ton of yard and food waste per year. Of 94 facilities examined in a recent survey, 17 composted fewer than 5000 tons of organic matter per year 16, and so a compost facility can be viable serving as few as 15,000 residents, though larger facilities tend to have lower per-ton costs 17.
Injection Molding
It is possible to use fibers that are not widely otherwise recycled, such as agricultural waste 18, degraded paper fibers 18, or plastics other than HDPE and PET 19, for injection molding to make plastic parts. Recycled material saves energy relative to injection molding with virgin material.
Aggregates
Construction aggregates refer to a range of particulate construction material, including sand and gravel. Recycled material from construction and demolition waste or fly ash can be used in place of freshly mined material 20. Recycled aggregates tend to be cheaper than virgin aggregates, but their mechanical properties are often inferior 21. About three quarters of aggregates used are for non-structural purposes 21, creating an opportunity for recycled material, and recycled aggregates can be used for some structural purposes as well 22.
Waste-to-Energy
Waste-to-energy, particularly incineration, generally does not perform as well environmentally as recycling. However, waste-to-energy may be preferable to landfilling. Emerging waste-to-energy, such as pyrolysis applied to municipal solid waste, is generally preferable to incineration.
Pyrolysis can be applied to many types of organic matter, including wood; organic waste; argicultural, forestry, and pulping residue; paper; cloth; plastics; and food and yard waste 24. Pyrolysis can make char, liquid synthetic fuel, or biogas 24.
A fusion torch is a hypothetical device that would use superheating plasma from a nuclear fusion device to break apart waste materials and sort them by chemical element 25. Such a process would require a yet-unbuilt fusion generator, perhaps an aneutronic device 26, and would be highly energy intensive 27. There has been little recent development.
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