Waste & Recycling


Stepping In The Same Stream Twice

A new study may go a long way toward settling the matter of whether or not the benefits of single-stream recycling outweigh its disadvantages compared to dual-stream recycling. Dan Lantz is Director o...

A new study may go a long way toward settling the matter of whether or not the benefits of single-stream recycling outweigh its disadvantages compared to dual-stream recycling. Dan Lantz is Director of Environmental and Engineering Services at Metro Waste Paper Recovery in Toronto, Ontario. His evaluation of single-versus dual-stream systems published in a recent edition of Resource Recycling couldn’t be timelier; program operators are reeling from depressed recycled commodity prices and end-customers are clamoring for better quality. (See page 20 for a report on recycling markets.)

As most readers know, fibres and containers are commingled in single-stream systems, and collected separately in dual-stream. Single-stream proponents say the simplicity for residents of tossing everything in one container encourages them to divert more material. The higher cost of separating the fibres and containers at the materials recovery facility (MRF) is offset in part by lower labor costs (if collection trucks with automated equipment are used). Defenders of dual-stream programs maintain that single-stream squanders the free labor of residents separating the materials at source. Subsequently, more recyclables may be collected, but residue rates increase.

Sorting through the claims on either side has been difficult for waste managers. This is why Lantz’s rigorous examination is so valuable. Lantz concludes that the benefits of single-stream recycling are overstated.

Lantz examined the 2007 recovery rates of some representative large-scale recycling programs in Ontario, including three single-stream and four dual-stream systems. The single-stream programs tended to be concentrated in major cities, while the dual-stream ones were a mix of urban, suburban and rural. Interestingly, he found that dual-stream recycling cost $3.50 less per tonne or about a dollar less per household.

Lantz notes that various factors need to be taken into account, including that dual-stream systems tend to operate with older infrastructure that will eventually have to be replaced, thus raising costs. But lower labor costs will offset this, especially as things like optical-sorting technologies are added.

Lantz estimates new equipment will trigger a net increase of $10 to $17 per tonne for dual-stream facilities, but prorating this across plants that don’t need new equipment lowers the amount to just $4 to $6 per tonne. Switching to a single-stream program raises labor costs; residue in the inbound stream and the efficiency of separation screens necessitates the addition of five to eight sorters at a cost of $3 to $7 per tonne. Some single-stream programs receive a premium for their fibre compared to dual-stream (examples include $6 to $7 per tonne) which can mask true net costs.

Lantz recognizes that large plants enjoy economies of scale. Facilities that process more than 50,000 tonnes per year typically operate more than one shift per day, which monetizes capital costs over two shifts and more tonnages, thereby lowering the capital cost per tonne. Two shifts would reduce capital costs by $5 and $8.50 per tonne.

On the surface, moving to single-stream collection appears to save money (20 to 30 per cent), but Lantz compared actual costs that show single-stream programs saving less than $3 per tonne compared to the average for dual-stream programs that pick up the two streams in the same pass. He concludes that dual stream collection costs could be lowered to match those of single-stream.

Tallying up the various factors, Lantz suggests that dual-stream programs can offer savings between approximately $8.50 and $22 per tonne (six to 15.5 percent) compared to single-stream programs. This is astounding.

But what about diversion rates? The study indicates that shifting to single-gle-stream may not be the main reason recycling rates appear to increase compared to other factors such as user-pay systems, bag limits and program promotion. The amount of material arriving at the MRF may go up with single-stream (along with higher residue rates) but there’s little evidence of single-stream recycling alone increasing

total diversion. Worse, contamination reduces the value of materials sold (through brokers) to end markets. An estimate from one Ontario mill suggests that increased contaminants raises its processing costs by $20 per tonne; some mills are simply not accepting fibre from single-stream systems these days. The majority of the tonnes marketed from Ontario MRFs is old newsprint; if they all converted to single-stream and were downgraded, the cost would exceed $8.9 million annually (with more material sent to landfill). In a typical single-stream MRF, 15 to 20 percent of the fibres end up on the containers line, and about the same percentage of containers end up on the fibres line, resulting in higher costs for additional screening or manual sorting than simply doing two sorts at the curb.

This is important information for anyone considering switching from dual-to single-stream recycling, especially in the current down-market for recycled commodities. Be sure to study the matter carefully before you make any big changes.

NOTE:Readers can download a copy of the Resource Recycling article from the Posted Documents section ofwww.solidwastemag.com

Guy Crittenden is editor of this magazine. Contact Guy atgcrittenden@solidwastemag.com

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