Metro Waste uses technology to recycle more

A new robot installed in late March is the latest piece of technology that the Metro Waste Facility in Grimes has invested in as it continues to explore innovative ways to improve processing at the center. 

Using an artificial intelligence system, the new equipment scans the lines for various materials, and with three robot arms attached, will aid in recovering more product. 

“We need to make sure it’s ultra clean to get a higher degree of cleanliness, a higher degree of product, a higher degree rating for the product, or help us recover as many items as we can from the last-chance line,” Metro Waste Authority recycling administrator Dan Haag said. “We are looking at a robot not about how quickly it fixes things but how efficiently and how accurately it fixes things.” 

The robot is Metro Waste’s second significant investment in new equipment this year after installing a new optical sorter to increase the amount of single-stream recycling the facility can process.

With about 115 tons of material arriving each day, Haag said the new sorter was expected to increase throughput from about 24 tons to 30 tons per hour. 

The optical sorting systems identify and separate a wide range of recyclable materials, reducing the reliance on employees to manually sort everything. 

Various plastics that moved through the system either by a sorter, such as a screening tool or an optical sorter, reach workers on the PET (polyethylene terephthalate) and HDPE (high-density polyethylene) QC line, where they divide the plastics into three separate commodities – HDPE color, HDPE natural and PET. The employees remove anything that is not HDPE color from the line pictured. HDPE natural products include see-through items like milk jugs, while HDPE color items contain a thicker plastic like a Tide detergent bottle and PET consists of thinner plastics like water bottles. Photo by John Retzlaff

Improved purity of recovered commodities, low maintenance and worker safety have been front of mind ever since the 101,100-square-foot facility opened in November 2021, when it debuted with an enhanced sorting system developed by San Francisco-based CP Group, according to a 2022 Metro Waste Authority news release. 

At the beginning of the system, auger screens help remove sharp objects, biohazards, glass, needles and other materials from streams before they reach employees, helping eliminate the traditional and hazardous presort. 

“This is the first facility that has had the auger screens installed, so basically what this is doing is trying to get all the large pieces of cardboard off the line early, and it’s supposed to be so things don’t get tangled around,” Haag said. “It relieves that hazard where we can pull off things that would do damage coming downstream, but we do have to oftentimes remove some material that gets tangled around those auger screens. But it separates size. So the first size is 0 to 6 inches, then 6-plus. Big pieces come off right away. They go right over the top of the augers, and then the smaller stuff just falls through onto a different line.

Workers sort material on the OCC (old corrugated containers) QC line. “All they’re moving here is material that’s not cardboard,” Metro Waste Authority recycling administrator Dan Haag said. “We want to keep that material along that line as clean as we can for cardboard because it’s going right into a bunker that we’ll bale and sell.” Once all of the materials move through the system, they reach the last-chance line, where workers pull materials and put them where they’re supposed to go. Photo by John Retzlaff

The facility also features CP’s auger silos, which maximize silo storage volume, according to the news release. The augers act as a material metering system that eliminates half and quarter bales by emptying the correct amount of material to be baled. 

All of the pieces of equipment, except for the optical sorter installed in January and the robot in March, have been around since the facility opened.