By Daniel P. Duffy, MSW Management
May 1, 2019
What separates winners from losers in a tight market? Since China declined to take further bulk quantities of recyclable materials from the US last year, unless they met new very stringent quality standards, the recycling market has experienced a downturn with the loss of its single largest market.
Something similar happened to the recycling industry after the stock market crash and recession of 2008. Though in this earlier case it was a general dropoff in demand for recycled materials due to a fall in economic activity, in both cases the demand and price for recyclables were negatively impacted. And in both cases, the market for recyclable materials has and will recover.
While the recycling industry is working to find other markets, the industry winners will be those who increase productivity, improve quality, and cut prices.
And this will depend on advances in sorting technology and concurrent improvements and innovations. At the forefront will be advances in sensor technology and optical sensing to achieve the necessary purity levels demanded by improving quality. And although advanced AI and robotics may one day create a “Smart MRF,” the human element will always remain paramount, requiring ever improved levels of training and intelligent, market focused planning.
Multi-Stream and Single-Stream MRFs
Single-stream MRFs are the opposite of multi-stream MRFs in every important operational characteristic. Instead of receiving multiple streams of waste from various sources and locations, single-stream MRFs receive waste directly from a single source, the community’s waste collection operations. As such, the commingled material that arrives at a single-stream MRF is far from pure, which give the facility its other name of “dirty MRF”. This type of facility relies primarily on machines to perform its sorting and separation operations. Waste arrives at the MRF’s tipping floor and is loaded onto a conveyor belt which carries the wastestream through various removal stations. Each of these stations is designed to remove a particular type of material from the waste. These machines perform their operations based on the size, electromagnetic properties, shape, weight, color, and density of the material being removed. The primary types of machines and the materials they remove are as follows:
- Magnetic separators for removal of ferrous metals: This is a simple and straightforward mechanism that relies upon electromagnetism to remove steel and other ferrous metals directly from the wastestream. What varies is the configuration of the magnets and the adjacent conveyor belt carrying the wastestream. The magnets either can be set overhead, pulling up the ferrous objects out of the wastestream passing underneath on the conveyor belt, or can be integrated into the belt itself, causing the ferrous metals to stick to the belt while the rest of the wastestream falls off into bins or another conveyor belt carrying the waste to the next removal station. The belts and the attached ferrous metals turn under at a roller located at the end of the conveyor belt. There, the metal is scraped from the belt by an edged blade and drops off into a designated collection bin.
- Eddy-current separators for the removal of non-ferrous metals: This is a more complex system than an electromagnet, but it is required to extract the bulk of the metals in the wastestream that are not ferrous. Its operation is based on the method of induced currents and the generation of an electromagnetic field from these currents. A collection of fixed magnets is arranged around the rim of rapidly spinning rotors. As the rotor spins, its magnets induce an electrical current in each piece of non-ferrous metal. This current, in turn, generates its own electromagnetic field in opposition to the field created by the fixed magnets. The two fields repel each other and the non-ferrous metal literally leaps off of the belt into a waiting receptacle.