Solid Waste & Recycling


One Stream In — Profits Out

Some of you may remember a Bizarro cartoon captioned "Recycling from Hell." The image depicted a vision of hell in which there were endless bins for every conceivable type of waste and Hell's resident...

Some of you may remember a Bizarro cartoon captioned “Recycling from Hell.” The image depicted a vision of hell in which there were endless bins for every conceivable type of waste and Hell’s residents would face an eternity of discarding of waste in the correct bin.

As a Toronto resident, for a time it looked like my life on earth was to mimic life in Recycling from Hell — blue box for glass and plastic, grey box for paper and cardboard, green bin for organics, and black bin for residual. Taking out the garbage on a Sunday evening was a 20 minute affair.

Thanks to advances in technology, single-stream recycling is now a reality in a growing number of Canadian municipalities. In these communities, the requirement of the average citizen to memorize what is and what isn’t allowed in various bins is less.

Single-stream recycling

Municipalities that utilize single-stream recycling remove much of the pre-sorting step from the homeowner and do it instead at the material recovery facility (MRF). Through advances in technology, the single stream of recyclables is sorted into saleable raw materials for industry.

When recycling was first introduced to the general populace in North American and Europe, it was a somewhat onerous process. Typically, glass, paper, plastic and metal, each representing a separate material stream, were placed in separate, color-coded containers at the curbside. All other waste items were placed in trash receptacles that identified their contents for delivery to the landfill.


Arguably, there are no technical barriers for any municipality from running a single-stream recycling program. The challenge would be in finding pickers to do the job.

With the advent of optical sorting equipment, the need for hand picking to segregate single-stream recyclables into metal, glass, plastic, cardboard, and paper can be done faster, with less labour, and with higher value “products.”

The world’s first automated optical sorting system for recovered paper began operation in 1999 in Baltimore, Maryland. The first system, supplied by MSS, Inc. from Tennessee, could sort up to eight tonnes of scrap paper per hour, replacing the need for 8 to 10 hand pickers.

In Canada, the first optical sorter for paper became operational in 2003 at Metro Waste Paper Recovery in Toronto.

The modern technology used to convert household recyclables into streams of saleable material at a MRF is basically the same, regardless of the manufacturer. The material is moved via conveyor belts where they are identified, using an optical sensor, by specific type of recyclable material. Removal from specific materials is accomplished by magnets, air jets, and other mechanical methods feeders (i.e., trommels, finger screens, and disc screens).

Optical sensing technology can identify specific objects on a conveyor belt moving at 1200 feet per minute. The paper sorting system utilized the Metro Waste Paper Recycling and supplied by MSS, Inc. has a capability sorting up to 99 different paper grades into individual categories (i.e., white, colored, newspaper, magazines, cardboard, etc.)


The first benefit of single-stream recycling starts at the curb. The homeowner only needs one bin for all recyclables. An easier sorting system means higher participation rates by residents.

With respect to pick-up, single-stream recycling cuts down on the need for special, compartmentalized trucks. For a composting municipality, pick-up is reduced to three bins: recyclables, organics, and residual waste.

At the MRF, the utilization of optical sorting technologies and mechanized removal has improved the recovery rate of recyclable material by up to three times and reduced the labour costs through the reduction in the number of hand sorters. It has also resulted in lower labour costs through the reduction. The baled material that is sold is cleaner, with less non-recyclable waste, and hence more valuable to the industry buying it.

The elusive “single” single stream

How close are we to a single bin that can be handled at a MRF? It appears that we are years away. Optical sorting equipment is not yet at the stage where you can just through a bin full of refuse onto a conveyor and end up with multiple streams of marketable materials. (This is sometimes referred to as a “dirty MRF.”) The best that can be achieved is a system that optimizes source-separated recyclables into higher quality resalable recyclables.

EDITOR’S NOTE:Turn to pages 34-35 for a walk-through of a two-stream recycling plant.

John Nicholson, M.Sc., P.Eng., is a consultant based in Toronto, Ontario. Contact John at

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