Limits to the Commingled Mix

Sticky pop cans, crumpled newspapers, a glass pickle jar with some juice congealing at the bottom, old clothes and an obsolete computer—all of these are released into the solid waste and recycling stream. The cans, papers and jars are standard shipments to a material recovery facility (MRF). But in some municipalities, items such as clothing, computers and plastic film are also being collected, and MRFs are not necessarily prepared to mechanically sort them.

Commingled recyclables processing techniques have been improved by a series of mechanical and technological steps, a trend that has greatly increased the popularity of commingled collection. But the research and development has focused on processing a somewhat narrow (though high-volume) stream of commodities: paper, plastic containers, food and beverage cans and glass jars and bottles.

At the same time these streamlined processing techniques have been developed, some communities are collecting additional materials to meet targeted landfill diversion rates. The new materials, in most cases, will not be welcome in the high-volume but sensitive MRF equipment that has been designed. Some creative problem solving is being attempted to allow more materials to be recycled outside of the traditional paper and containers stream.

DIVIDING THE STREAM

Landfill diversion rate targets and increased desires to reduce what heads to the landfill have made many recycling coordinators and MRF operators look for ways to take more types of materials and process them efficiently and economically. “We are seeing increasingly that cities want to add more materials and make them fully commingled into a full stream of materials,” says Kevin McCarthy, region recycling manager for Waste Management at its Davis Street Transfer Station in San Leandro, Calif. “We take that single stream and break it into various commodity grades,” the MRF operator says.

Installing automated equipment is the approach Waste Management has been taking to increasing the variety of materials accepted and to keep processing costs economical, but so far paper and container recycling is what has been addressed. Installing screens to help separate bottles from cans and different paper grades as well has worked well for the MRF, Mc-Carthy says. “We’re challenged with trying to sort material to see if we can employ some sort of screening equipment to recover those materials,” he says of any new materials that might be considered.

Perhaps part of the need to take in a more varied stream of materials arises from recycling goals mandated by the state of California for 2000. “In California we have a 50% recycling goal by this year, so cities are exploring or adding materials to their existing programs,” McCarthy says. “This ranges from trying to add additional plastic bottles to some cities adding food waste to their programs. It can be a pretty big change in your processing system.

“Screens help do most of your sorting work, other than pulling cardboard,” McCarthy says. What might look like inefficiency on the front end—commingled collection—actually pays off because automation can help do a lot of the sorting needed, he says. Having waste haulers save time by not sorting materials collected at the curb into separate streams makes the overall system more cost-effective, McCarthy says, because the labor and time spent manually sorting at the curb can be replaced by an automated system at the MRF.

“The trick is balancing your collection system with your processing system,” he says. “By going to a commingled stream you save money on the front end by not having to have segregated trucks and instead having a single truck with a greater payload. It makes things more efficient overall with what we see, because those collection savings are more than you can save at the MRF.”

And while commingled collection may mean adding a few more manual sorters at the MRF, the savings is still greater then implementing sorting at the curb. “The goal of our company is to maximize the effort at the MRF so you get a greater overall savings. Hopefully where you end up is you see greater collection cost savings,” McCarthy says.

Commingled collection and an automated sorting system have also been more efficient for Cedar Rapids, Iowa. Gary Spellersberg, assistant plant manager of City Carton Co., Cedar Rapids, says that once the company switched to a more automated sorting system, the same amount of processing could be accomplished using one shift instead of the two shifts the company had previously been running.

“We’ve noticed that we went from two shifts of sorting curbside materials down to one,” he says. “We’re over twice as fast. That is the big selling point of this because we were maxed out and now we can do all of it in one shift with room to grow.”

City Carton processes the materials collected by Blue-stem, the government agency that runs the recycling program for the Cedar Rapids area. City Carton processes plastics, paper, cardboard, tin and aluminum. The materials had been largely hand-sorted beginning in September 1998, but in September 1999 a more automated system was put in place. Screens to pull out cardboard and paper are used, though much of the rest of the materials are still hand sorted.

Spellersberg says that while some programs still do sort materials at the curb, that the deciding factor in collection methods is often the cost of transportation. “When you go to source separated you have to educate them more,” he says, speaking of educating the residents participating in the curbside collection programs. “We can sort everything here and it is easier to train 16 people [at the MRF] to sort them out than to train the entire city.”

The materials City Carton processes are dictated by markets for those materials, Spellersberg says. As markets may emerge for particular materials, such as foam or carpet (materials that City Carton is exploring processing), then the company will have to seek ways to process the new commodities.

PICKING AND CHOOSING

Moving to the commingled collection model seems unmistakably the trend in municipal programs. Chris Almeida, recycling operations manager of Greenteam, San Jose, Calif., says commingled collection has been found by their company to be more popular than the sort and sift method of separating materials at the curb. “We have found that the drivers want single steam for collection,” he says, “and the customers love it because they have one container. Participation has gone way up and pounds per house have gone up.”

A pilot program in San Jose that tested commingled collection found it to be a popular choice for recyclables, even adding some commodities not typically collected, such as plastic film and textiles. Both the collection and processing of the materials collected in the test run appears to have gone very well. “We just ran a load of our single stream pilot program and it went very well with our film and textiles,” he says. “We over-contaminated the load to see if the system would get bogged down.” And even with the system processing more of the problem materials, the trial run seems to have been a success on both the collection side and processing side.

In the sorted streams, employees sort materials in different bins at the curb, with further sorting occurring at the MRF. Almeida says there is a quality check on all materials entering the facility to see if they can be recycled. “Anything we might find a market for [we try to capture],” says Almeida. “The reason we do it is San Jose receives the entire amount a customer pays. Then we get an incentive payment for any recycling.”

Nontraditional materials such as plastic film and textiles can have a value to Greenteam if they are clean and not contaminated. Plastic film is often exported, but if shipments contain food contamination, by the time they make it overseas the contaminated materials might be too rancid to be recycled. “If we get even specks on the plastic film that are certain types of food waste, then it might become a rancid load and that becomes a problem,” Almeida says.

Regarding textiles, Almeida says that it makes more sense to collect items such as used clothing at strategic times of the year, such as in August when it is back to school time. Because of the volume of materials that can be collected at these times, it makes economic sense to have a truck collect the textiles. Potentially, these materials can be sold at flea markets or other outlets where instead of getting 10 cents for a pound of clothes, single items can be sold for 25 cents.

Ellen Ryan, division manager of the Environmental Service Department of the City of San Jose, says that while textile recycling is encouraged, placing the materials at the curb is often a suggested last place to deposit the materials for reuse. Donating clothes to charitable organizations is often the first suggestion for these materials. “The recycling bin is the last resort,” Ryan says. “It’s actually a very small part of our recycling stream.”

DEVELOPMENTS IN THE HAWKEYE STATE

In Iowa, some cities have taken an aggressive approach to recycling, including the collection of all plastics except #6, along with mixed paper, metals, plastic bags, auto lubricant containers, cardboard and composting. Cedar Rapids, Iowa, has also gone to a commingled collection stream because of the desire to increase participation in recycling programs, says Mike Berkshire, planning and education coordinator for Bluestem Solid Waste Agency.

Cedar Rapids also has one of the largest composting programs in the United States, Berkshire says. “Our board is very progressive in doing lots of programs,” he remarks.

In addition to curbside programs, Cedar Rapids also has had much success with electronics recycling and a pilot program for dropping off materials, says Jeff Maxted, community education specialist. A free drop off for computer equipment offered for three days last December netted 22.6 tons of computers, he says. “It was unbelievable for a county of 180,000 people,” he remarks. “And that was only from residents and not from businesses.”

Bluestem is in the process of selecting a company to head a permanent drop off location for computer equipment that is scheduled to begin in April. The actual recycling of the computer equipment is contracted out to companies specializing in the processing of electronic equipment, he says.

MAKING SOME ADJUSTMENTS

Materials that could potentially call for some modification of existing MRF set-ups include textiles, plastic film, plastic foam, tires and electronics such as computers. “Some of the problem materials would be textiles and film plastic because they take up a lot of volume and are sort of a bigger item that isn’t readily separated out by the screens,” McCarthy says.

Although the use of screens does help sort plastics, glass and paper, materials such as film and textiles can end up in all streams and then must be manually separated out at the MRF. And while textiles or polystyrene can make up a pretty small amount of the total waste stream, if there is value in the sorting of that commodity, McCarthy says that some recyclers will want to separate it out of the waste stream.

But there appear to be emerging markets for material such as film plastic and companies are looking for economical processes to collect and sort these materials, he says. RT

The author is the Assistant Editor of Recycling Today.