Dear Recyclebank,

Until recently, we had to separate the paper, plastic, and aluminum for recycling. Now our city picks up recyclables together in one bin. Why do some places require you to sort your recyclables, while others let you mix them together?

-Christine W., Brookhaven, NY

Dear Christine,

Recycling programs vary widely across the country because they are administered locally, usually at the municipal level. When a municipality or hauler picks up recyclables, they send the materials to a materials recovery facility (MRF) for sorting. Processing begins after materials are sorted, and sometimes additional sorting is still needed even if items are sorted at the curb. As you’ve seen, the sorting process either begins at home or occurs later after curbside pick-up.

Whether a recycling program accepts separated or mixed materials depends on what kind of equipment is available at its MRF. Some MRFs are classified as dual- or multi-stream, meaning they do not accept paper products mixed with other materials. Multi-stream recycling is often seen as more inconvenient and registers lower recycling rates because residents have to separate their recycling. However, the processed material from multi-stream facilities tends to be cleaner (and therefore, more valuable) because there’s less chance for contamination. Contaminated recyclables are, in effect, unrecyclable and must be sent to a landfill.

Single-stream facilities (which are more common than dual- or multi-stream) accept mixed recyclables because they are equipped with technology that can sort the different materials. That technology can use mechanical agitation, vacuums, magnets, gravity, and more to separate a newspaper from a milk carton from a soda can. Tossing all accepted materials into one bin makes recycling much more convenient for residents, so single-stream programs typically see higher recycling rates. Because it’s simpler and more convenient for residents, single-stream recycling has steadily increased in popularity since the 1990s.

Multi-stream facilities can sometimes be retrofitted to process mixed recycling, or some waste management companies find that building a single-stream MRF makes sense financially and administratively. When either of those things happens, check with your local public works department or waste hauler to learn more about what you can recycle and if you need to acquire a new recycling container.

SOURCES
University of Wisconsin, Milwaukee Cooperative Extension
The Green Grok – Duke University, Nicholas School of the Environment