Solid Waste & Recycling


Recycling, Sorting and Separation Equipment & Systems: Single-Stream Recycling

The momentum towards single-stream recycling systems is pushing ahead. Recyclers, waste management companies and municipalities have embraced the concept and are realizing the benefits of this efficie...

The momentum towards single-stream recycling systems is pushing ahead. Recyclers, waste management companies and municipalities have embraced the concept and are realizing the benefits of this efficient process. Modern technology and better management has dramatically improved system capabilities.

With more single-stream recycling programs in operation, there is further evidence that the benefits are real. However, some still wade cautiously because of quality concerns. A lot of these concerns seem to center around the quality of paper coming out of these plants. But it’s important to remember that traditional multi-stream processes do not guarantee better quality because they are only as good as their curbside sort and the separation system within the recycling truck. Multi-stream processes rely on the same sorters and inspectors as do single-stream processes so it’s fair to say that the risk of contamination will always exist in both processes.

The most effective ways to mitigate these risks are through public education, staff training, proper plant management and a well-designed sorting system.

Case studies

In the past year, various case studies have compared single-stream and multi-stream recycling programs.

Several of these studies conclude that the single-stream process is more cost effective than traditional multi-stream methods while several argue that there needs to be a larger volume of recyclables to justify the expense of the equipment.

But when reviewing overall system costs, including the cost of collection, smaller communities experience significant savings by moving towards single-stream recycling.

Let’s make use of a hypothetical example to illustrate the benefits and risks of a single-stream vs. a multi-stream system.

When the cost of capital to purchase processing equipment are examined along with the cost of direct labour for a seven-year contract on a per tonne basis, one can see how insignificant the capital costs are. With this seven-year contract, to process 50,000 tonnes of recyclables per year the average cost of the equipment $6 per tonne and $17 per tonne for labour. These numbers are based on a single-stream recycling system that employs the latest technology.

With a less automated multi-stream process, the labour cost per tonne would increase even higher — perhaps by as much as an additional $5 per tonne. The capital costs suddenly become less significant.

The cost savings in a single-stream recycling process are also realized at the collection stage due to the elimination of the curbside sort. Single-compartment compaction vehicles carry greater payloads and are able to do more stops per hour, and this reduces the amount of collection trucks and drivers required.

This is the case despite the fact that the single-stream collection trucks cost more, use more tires and get less gas mileage than the lighter multi-stream collection vehicles.

The collection cost difference in the 50,000 tonne per year cost model equals approximately $13.50 per tonne.

Other common benefits of a single stream system include that the tipping floor of the MRF is safer and easier to manage due to the reduction of truck traffic (and there’s one less tipping floor to supervise). Further cost savings derive from having fewer trucks to maintain and insure, lower route supervision costs and lower consumption costs for both the drivers and the trucks.

When the savings in collection cost and the processing costs are combined, the savings can work out to as much as $15 per tonne or 17 per cent. At 50,000 tonnes per year, the savings adds up to $600,000 per year or $4.2-million over seven years.

Key factors

That said, it’s important to realize that there are two factors that can make or break any cost model: management and staff training. Without effective management and proper training, the performance factor decreases.

At the operations level, the manager must have an excellent understanding of the material flow through the plant and how to properly deploy staff. Proper metering of the in-feed system is also critical to productivity. All too often the loader operator who’s assigned to feed the sorting system is also assigned other distracting duties. This operator can negatively affect the productivity of all of the staff on the sorting line, which in some cases is more than 20 people.

If the sorters are seeing nothing but black belt, they are not able to sort. If the burden depth on the conveyor is too high, the sorters will pull the stop cord to sort through the large pile on the sorting conveyor and productivity is lost again. If a facility loses 10 to 15 per cent efficiency due to improper metering, up to $100,000 per year could be lost based on the 50,000 tonne per year model.

It’s not practical to dump a big pile of recyclables on the in-feed conveyor and expect it to self-meter. The best automated in-feed systems will not replace good loading practices. The system will only enhance the efforts of the loader operator.

Whether choosing a single-stream or multi-stream recycling system, lower recycling costs can be achieved by embracing new technology and focussing on operational competence.

Bob Marshall is president of Machinex Recycling Technologies, based in Pickering, Ontario.

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