Best Practices in Shredding Municipal Solid Waste (MSW)

Shredding waste may sound like a simple concept, but in actuality, there are many factors to consider when choosing size reduction equipment. The type of industrial shredder to choose is just one piece of the puzzle in waste processing. If the material input is consistent and clean, a single machine may be sufficient. However, for shredding MSW, Vecoplan recommends a two-stage approach of pre-shredding and re-shredding for optimal throughput and processing.

Understanding Shredding Technology: Types of Shredders

When considering the “when” and “why” to shred waste, understanding the shredding technology available is important. Reviewing expected throughput in your facility is the first factor to consider in shredder technology. Whether an industrial waste shredder has one or multiple shafts determines the throughput.

What are the Different Types of Industrial Shredders?

Single Shaft Shredders

Single shaft shredders yield lower throughput than its counterparts. If the material processed is relatively soft, such as wood, or consists of small particles, a single shaft shredder is a lower investment option. If a single shaft shredder is being considered, it would be optimally applied in cases when the MSW material has been broken down first with a pre-shredding machine.

Single-shaft shredders often do not handle contaminants well; the input material must be free from metal, inerts, and other hard contaminants. Vecoplan has single shaft shredders that address this problem. The VAZ and VEZ 2000 and larger models have an optional air spring counter-knife to detect such contaminants. The machine will pause if the counter-knife senses a contaminate, minimizing contact with the rotor.

Dual Shaft Shredders

Dual shaft shredders have opposite rotating rotors that pull the material between the two. They are available with knives or shears.

Dual Shaft Shredders with Cutters

In a dual-shaft shredder with cutters (knives), the material is cut when it passes over the cutter and a counter-knife. This creates a clean, scissor-like cut and the output it is finer. Cutter technology is best for processing film or other tensile material.  Vecoplan industrial shredders VVZ models 2500 to 3100 and VNZ models 2100 to 3100 are specifically designed to handle ductile material.

Vecoplan launched in 2020 a new product, the VRZ, that is similar to cutting technology except that it has sickle-shaped teeth in place of traditional cutters. This size reduction machine is optimal for large, bulky items such as wired bales and bags full of MSW that need to be quickly broken down at a high throughput (60 tons/hour). These machines are currently sold primarily in Europe.

Dual Shaft Shredders with Shears

Shear shredders have large oblong lobes instead of knives. Material is pulled through the lobes, tearing it in the process. The throughput rate and output size are determined by the tolerance between the lobes. Shear shredding is best for materials such as metals, large appliances, cars, and other bulky, tough waste material. However, if homogenous particle size is required or long films are present, then these shredders are not the best choice.

 Shredder Machine Customization

There are many options available on industrial shredders that affect maintenance, cleaning, uptime, and hardware selection for controlling how the material is shredded.

 Waste Shredder Maintenance

Like all machines, there are high-wear parts on shredders. Preventive maintenance too will add to the machine’s longevity. Access to the areas that must be maintained or cleaned is part of the equipment’s design. Vecoplan shredders are designed to be ergonomic with quick accessibility, such as door panels that open outward and a hydraulic screen that lifts away from the rotor yes remains attached.

 Time-Saving Shredder Features

It is virtually inevitable that MSW will have contaminants that feed into the shredder, an occurrence that can shut down an entire production line if the rotor jams. With a hopper full of waste, removing the contaminant from the rotor can be time-consuming. Vecoplan’s VEZ 2500 single shaft shredder has a swing-up floor to easily access the rotor, avoiding the need to first clean out the hopper. Further, its air spring counter-knife option is designed with a limit switch to stop the rotor when it senses a contaminant. The pressure on the counter-knife engages the switch, and the pressure setting is changeable. This variable switch allows for the customer to determine the detection sensitivity for contaminants versus a binary setting. This feature is useful particularly for inert materials such as metal and rocks.

 Cutter Selection

In addition to rotor type technology, the cutters on the shafts are an important component of how the material is shredded. Whether it is a pre or re-shred scenario, cutter size, type, and composition must be considered. Ductile materials such as film or paper need very sharp, hard metal cutters. Softer materials don’t need such robustness in the cutter composition. Cutters are high-wear parts and should be replaced regularly, the timing of which will also vary based on your material type and throughput per hour.

 The Methodology of Shredder Selection

To determine the best size reduction machine for a facility, Vecoplan waste engineers discuss with its customer's input material and company goals. The recommended technology considers these components but also considers future variables so the customer is not stuck with a shredding system that is inflexible to adapt to market changes. Vecoplan’s experience is that material changes over time based on availability, legislation, supply, and other unforeseen factors.

Managing Expectations

When deciding to add a shredder into your operation, it is important to understand the basics before engaging with a shredding specialist: what material is coming in and what end-product is desired. A system should be designed to be adaptable to different inputs in order to obtain a return on the investment. Conduct a review where throughput can be increased or how the system can be designed in order to handle higher throughputs based on expected (or unexpected) growth.

Investing in an MSW shredder

One size does not fit all with shredder selection. In order to invest in the right shredder, the operational needs and processing economics must first be clearly understood. Once these factors are defined, then shredder technology and options are more easily determined to meet goals. Vecoplan specializes in size reduction technology with machines that are engineered specifically to handle the waste. The right system that allows an operation to produce a valuable end-product can make a business sustainable for decades.

Start investing in an MSW Shredder. Contact Matt Davidson, Waste Sales Engineer, for further information. (336) 500-1471, [email protected]