Tonnages are increasing in today’s MRFs, and safety and efficiency are key to the operational success. As technology is developed, we are going to see more and more automation being implemented into the MRFs of the future.
By Clay Layne
Before we discuss what a MRF is and the equipment used in one, let’s discuss why a MRF is important. The quantity of overall solid waste in cities is rising at a pace of 5 percent per year. Every year, per capita waste generation, grows by 1.3 percent. Because of the rising waste generation, it is impossible to recycle most of the waste generated if material recovery facility equipment executes manual operations, as manual processes take a long time to sort the waste stream. That is why advanced methods and machinery are required to increase speed and recover large amounts of waste daily.
The total generation of MSW in 2018 was 292.4 million tons—4.9 pounds of waste per person per day. Of the total MSW generated, approximately 69 million tons were recycled, and 25 million tons were composted. Together, almost 94 million tons of MSW were recycled and composted, equivalent to 32 percent diversion rate. In 1960, 5,610,000 tons of MSW were recycled compared to 69 million tons in 2018. Over time, recycling and composting have increased from just 6 percent in 1960, to 10 percent in 1980, to about 29 percent in 2000, to 32 percent in 2018. The current EPA has implemented a plan called 50by30. This means 50 percent diversion by 2030. With these increased numbers and regulations, the need for automation, properly sized and equipped machines, and operational efficiencies are more crucial than ever to meet these requirements.
Photos courtesy of Caterpillar.
Starting the Process
Overall, a material recovery facility looks like a very simple system. Raw recyclables are dumped on the tip floor. The MRF technology inside sorts, cleans, breaks down, and compacts those recyclables. On the other end, the MRF produces neat bales that are then loaded up and sent to an end user.
Of course, the process is much more complicated than that. Today’s MRFs use several types of material handling systems, and the best of them are designed to work hand-in-hand with all
machinery that sorts, cleans, and compacts recyclables for re-use.
So, where does the MRF process start? Most generally, the process starts with a front-end wheel loader. The hauler trucks arrive at the MRF, weigh on the scales, and then dump their loads on the tipping floor and leave. The dumped raw recyclables now need to be moved from the tip floor to the MRF system. The wheel-loader can be used to accomplish this task. The loader can scoop up the raw materials in the bucket and place them on the sorting table or in the hopper to load the conveyor lines of the MRF system.
Placing the Right Equipment
There is not a one size fits all when it comes to support equipment in the MRF. A few things to consider when trying to place the right machine and attachments in your application are:
• What are the daily production goals for the MRF?
• What are future growth opportunities?
• What task will the loader be doing (stockpiling, loading hopper, loading trucks, pushing material to another machine)?
• What is the hopper height?
• What type of truck load out (below grade, half separation, same level)?
• Will the loader be feeding another machine for load out (wheeled excavator or material handler)?
Being able to answer the above questions will help in determining:
• What size of loader to place in the MRF
• What type of bucket to equip the loader with:
o Load and Carry type bucket
o Tamp and Clamp bucket
o Push and Doze type bucket
o Whether or not to equip bucket with rubber or steel cutting edge
o High lift configuration vs. standard lift
o Wheel loader with rim pull selection vs. no rim pull selection
If you are going to use the wheeled excavator or material handler option, you will need to answer some basic questions as well to determine proper machine and attachment. Just like the wheel loader, proper sizing is crucial to safe and efficient operation:
• What are the daily production targets?
• What are the future growth opportunities?
• What other task will the wheeled exca vator or material handler be doing?:
o Stockpiling
o Loading trucks
o Hopper or conveyor loading
• What type of attachment will be needed?:
o Demo and sorting grapple with 360-degree rotation
o Orange peel grapple
o Thumb on an excavator
o Contractor grapple
• If loading trucks for transport to the landfill, what type of truck and loadout?
o Below grade loading
o Half separation loading
o Same level loading
All this information will help in the selection of properly sized equipment to allow for safe and efficient operation in the MRF.
Reducing Contaminated Materials
After being loaded into the MRF system, the materials pass through a complex list of MRF technology to reduce the contaminated materials:
• Robots or AI assist the human staff in pulling contaminants off sorting table
• Human staff take contaminants and place in safe location for load out to the landfill
• Optical sorters identify and separate material materials
• Magnets pull out all metals
• Disc sorters drop smaller items onto a separate track
• Star screen sorters separate finer materi als from longer ones
• Air classifiers blow paper, plastics and metals into separate lines
• Materials will pass through washing machines
• Sometimes plastic bottles go through a perforator and glass goes through a crusher
• The materials that make it through the screening process will end up in the baler which compacts all material into a roughly 2,500 lb. bale
Handling the Bales
Once the materials are baled for transport, forklifts are the go-to technology to handle the bales. The forklift can be fitted with bale/carton clamps to move the bales quickly and safely into and out of storage, shipping containers and trucks. Small wheel loaders and skid steers can also be equipped with forks and bale clamps to move the bales safely and efficiently.
Finally, all the material that is rejected on the MRF line will be stockpiled and loaded out into large trailer’s and transported to the landfill for disposal. Material can be loaded out in several ways depending on the design of the MRF.
The load out area can be separate with separate equipment strictly for the load out process. It can also be combined with the MRF application as well. For example, if the material handler was feeding the MRF and the wheel loader was feeding the material handler, the wheel loader could sort and stockpile the rejected material and load the trucks after the material handler is supplied with enough material to continue its loading operation.
A wheeled excavator, HEX, or material handler could be solely placed at the load out area and the wheel loader can push material to this machine strictly for loadout. The wheel loader becomes a very versatile machine in the MRF.
Safety and Efficiency
Tonnages are increasing in these MRFs, and safety and efficiency are key to the operational success of the MRF. As technology is developed, we are going to see more and more automation being implemented in the MRFs of the future. | WA
Clay Layne is the Sales Support Consultant in Waste Applications at Caterpillar Inc. Clay covers landfills, transfer stations and MRFs. He started working for Caterpillar in 2008 as an operator at the Peoria Proving Grounds working with engineers on the
Research and Development of Caterpillar Machinery. In 2011, Clay moved to the Edwards Demonstration and Learning Center. It was here that Clay started working in the Waste Industry, conducting onsite operator training for Caterpillar customers all over the world. Clay can be reached at (309) 675-8486 or e-mail [email protected].