Overview
Recycling means different things to different people. To consumers, recycling may mean putting out bottles and cans for curbside collection. To a product maker—a manufacturer of raw materials or fabricator of goods—it means including recycled materials in the process. To recycling service providers, recycling can mean providing cost-efficient collection, sorting and shipping services. For scavengers, it means culling recyclable materials from garbage and waste cans and selling them to recycling depots. To public policy makers in all levels of government, it means establishing regulations governing collection and utilization as well as reducing the volume of waste to be disposed of and deriving revenue from the sale of the recycled materials. For recycling to work effectively and safely, these diverse groups must be educated to work together and share responsibility for its success.
The recycling industry had been growing steadily since its inception a century ago. Until the 1970s, it remained basically unchanged as a voluntary private sector effort conducted largely by scrap dealers. With the advent of incineration in the 1970s, it became desirable to separate out certain materials before putting waste into the furnaces. This concept was introduced to address the emission problems created by metals, batteries, plastics and other materials discarded in urban wastes which were causing many old incinerators to be shut down as environmental polluters. The increasing concern about the environment provided the primary impetus for the organized separation of plastics, aluminium, tin, paper and cardboard from the residential waste stream. Initially, the recycling industry was not economically viable as a self-sustaining business, but by the mid 1980s, the need for the materials and the increase in their prices led to the development of many new material recycling facilities (MRFs) to handle commingled recyclable materials across the US and Europe.
Work Force
The broad range of skills and expertise makes the range of employment for a MRF very wide. Whether it is a full-service MRF or a single sorting-line operation, the following groups of workers are generally employed:
- Operators of heavy equipment (front end loaders, grapples, bull-dozers, etc.) work on the tipping floor, coordinating the movement of waste from the staging area of the tipping floor to the area where the materials are sorted.
- Material sorters, the majority of the workforce, segregate and sort recyclable materials by product and/or colour. This may be done entirely by hand or with the assistance of equipment. The sorted materials are then baled or crated.
- Forklift operators are responsible for moving finished bales from the throat of the baler to the storage area and from there to the trucks or other means of transportation.
- Maintenance workers are becoming increasingly important as the technology advances and the machines and equipment become more complicated.
Processes and Facilities
The recycling industry has been growing very rapidly and has evolved many different processes and procedures as the technology of sorting recyclable materials has advanced. The most common types of installation include full-service MRFs, non-waste stream MRFs and simple sorting and processing systems.
Full-service MRFs
The full-service MRF receives recyclable materials mixed in the residential waste streams. Typically, the resident places the recyclables in coloured plastic bags which are then placed in the residential waste container. This allows the community to combine recyclable materials with other residential wastes, eliminating the need for separate collection vehicles and containers. A typical sequence of operations includes the following procedures:
- The waste and recyclables bags are dropped from the collection vehicle onto the tipping/collection floor.
- The mixture of waste and recyclables is moved either by a grapple or a front-end loader to an in-floor conveyer.
- The conveyer moves the material into the sorting area where a rotating trommel (a cylindrical sieve) opens the bags and allows the very small particles of dirt, sand and gravel to pass through the openings to a collection container for discarding.
- The remaining materials are semi-automatically sorted by screens or disks according to weight and bulkiness. Glass is sorted by its heavier weight, plastics by their lighter weight and paper fibre materials by their bulk.
- Employees hand sort materials, typically from an elevated position above bunkers into which the materials can be stored. Materials are sorted according to the grade of paper, the colour of glass, the physical properties of plastic and so on.
- Refuse and other wastes are collected and removed by tractor-trailer loads.
- The separated materials are moved from the bunkers by forklift or by a “walking floor” (i.e., a conveyer) to a baler or a shredding and baling operation.
- The formed bale is discharged from the baler and moved to the storage area by a forklift.
- Collected bales are shipped either by rail or a tractor-trailer. Instead of baling, some MRFs loose load the materials into a rail car or a tractor trailer.
Non-waste stream MRF
In this system, only the recyclables are delivered to the MRF; the residential wastes go elsewhere. It involves an advanced, semi-automated sorting and processing process system in which all of the steps are the same as those described above. Because of the smaller volume, fewer employees are involved.
Simple sorting/processing system
This is a labour-intensive system in which the sorting is performed manually. Typically, a conveyer belt is used to move material from one work station to another with each sorter removing one type of material as the belt passes his station. A typical sequence for such a simple, inexpensive processing system would include these processes:
- Mixed recyclables are received on a tipping floor and are moved by a front-end loader to the main sorting conveyor belt.
- Glass bottles are separated manually by colour (flint, amber, green and so forth).
- Plastic containers are sorted by grade and accumulated for baling.
- Aluminium cans are removed manually and fed to either a compactor or baler.
- The remaining materials are discharged into a residue pile or container for disposal.
Equipment and machinery
The machinery and equipment used in a MRF is determined by the type of process and the volumes of materials handled. In a typical semi-automated MRF, it would include:
- bag openers
- magnetic separators
- screens (disks, shakers or trommel)
- material classification equipment (mechanical or pneumatic)
- glass crushers
- balers and compactors
- eddy current separators (for non-ferrous metal separation)
- conveyer belts
- rolling stock.
Health and safety hazards
MRF workers face a large variety of environmental and work hazards, many of which are unpredictable since the content of the waste changes continually. Prominent among them are:
- infectious disease from biological and medical wastes
- acute and chronic toxicity from household chemicals, solvents and other chemicals being discarded. This risk is not very great (except when industrial wastes find their way into the residential stream) since household chemicals are usually not very toxic and only relatively small amounts are present.
- solvents and fuel and exhaust fumes (especially vehicle operators and maintenance workers)
- exposures to heat, cold and bad weather since many MRFs are exposed to the elements
- noise at harmful levels when heavy machines operate in confined spaces
- physical hazards such as slips and falls, puncture wounds, lacerations and abrasions, muscular strains, sprains and repetitive motion injuries. Sorters usually stand continuously, while vehicle operators must sometimes contend with poorly designed seats and operating controls.
- airborne dust and particles.
Table 1 lists the most common types of injury in the recycling industry.
Table 1. Most frequent injuries in the recycling industry.
|
Injury type |
Cause of injury |
Body part affected |
|
Cuts, abrasions and lacerations |
Contact with sharp materials |
Hands and forearms |
|
Strain |
Lifting |
Lower back |
|
Particles in eye |
Airborne dust and flying objects |
Eye |
|
Repetitive motion |
Manual sorting |
Upper extremities |
Prevention
MRF workers have the potential to be exposed to whatever wastes are delivered to it, as well as the ever-changing environment in which they work. The management of the facility must constantly be aware of the content of the material being delivered, the training and supervision of the workers and their compliance with safety rules and regulations, the proper use of PPE and the maintenance of machinery and equipment. The following safety considerations deserve constant close attention:
- lockout/tagout precautions
- general housekeeping
- egress maintenance
- emergency preparedness and, when needed, access to first-aid and medical assistance
- hearing conservation programmes
- protection against blood-borne pathogens
- preventive maintenance of machines and equipment
- traffic patterns and danger to pedestrians from the rolling stock
- confined spaces
- fire prevention and training and equipment for fire-fighting
- household hazardous waste management
- availability and use of high-quality, properly-sized PPE.
Conclusion
Municipal recycling is a relatively new industry that is changing rapidly as it grows and its technology advances. The health and safety of its workforce depend on proper design of processes and equipment and the proper training and supervision of its workers.