2.4 Waste Diversion
47
as aluminum, lead, copper, silver, gold and titanium can be separated by this method
[31].
Separation of glass, plastic and cartons is an important process in MRFs. Most of
the MRFs use manual glass sorting with clear flint being negatively sorted [31]. Plastics can be sorted by using automated optical sorting systems. Automated systems
employ near-infrared sensor technology (NIR), color sensors and cameras to analyze
and classify polymers, aseptic packaging and paper according to their unique IR
absorbance. Various colors and resins (PET, HDPE, PVC, PP, PS, PLA, etc.) can be
separated accurately and efficiently through the automated systems. A typical automated optical sorting system consists of an accelerating belt conveyor with speeds
close to 500 ft/min, a sensing unit and a pneumatic ejection system and can sort
different plastic containers based on their color and resin type. The type of resin is
identified using NIR, laser or X-rays technology and the color is identified using
vision technology (CCD linear cameras, CCPD) and spectroscopy [31, 33, 35].
Papers are usually sorted using a trommel and manual separation. There are a
number of automated optical sorting systems being developed for recycled paper such
as PaperSort developed by Magnetic Separation Systems (MSS) and Finger Screen
developed by General Kinematics Corporation (USA). The PaperSort technology
spreads the feed into a single layer using mechanical techniques and then sends
the stream to reflective sensors that identify the optical properties of the paper. An
appropriate air nozzle is activated based on the type, size and position of the paper and
automatically removes the paper from the conveyor. A full-scale PaperSort equipment
is now operating at Weyerhaeuser’s recycling plant in Baltimore. The Finger Screen
technology conveys the mixed paper stream over a series of tapered, slotted finger
elements and screens the paper without jamming. This allows for a reduction of
the volume of the paper stream and allows the system to handle a larger amount of
materials [31].
2.4.1.1 Health and Environmental Impacts of MRFs
A recycling facility can have a negative impact on the surrounding air, water and
land if it is improperly designed and operated. The sources of environmental impacts
include hazardous wastes such as lead-acid batteries, non-hazardous residual liquids,
scrap metals contaminated with cutting oils and metallic fines, etc. To prevent the
possible negative impacts and pollution problems, facilities should follow practices
such as draining and collecting waste liquids in a designated area, regularly inspecting
the operations for spills, leakages, corrosions and any signs of deteriorating structural
integrity and separating the hazardous wastes and residues from non-hazardous waste
and dispose of them accordingly. Other environmental and health impacts include
noise, odor, traffic, dust and litter. These can be controlled by fully enclosing the
receiving and processing areas, using chemical controls for odors, using air handling
and filtering equipment for dust, and addressing all other issues during the design
and operations plan [33].
47
as aluminum, lead, copper, silver, gold and titanium can be separated by this method
[31].
Separation of glass, plastic and cartons is an important process in MRFs. Most of
the MRFs use manual glass sorting with clear flint being negatively sorted [31]. Plastics can be sorted by using automated optical sorting systems. Automated systems
employ near-infrared sensor technology (NIR), color sensors and cameras to analyze
and classify polymers, aseptic packaging and paper according to their unique IR
absorbance. Various colors and resins (PET, HDPE, PVC, PP, PS, PLA, etc.) can be
separated accurately and efficiently through the automated systems. A typical automated optical sorting system consists of an accelerating belt conveyor with speeds
close to 500 ft/min, a sensing unit and a pneumatic ejection system and can sort
different plastic containers based on their color and resin type. The type of resin is
identified using NIR, laser or X-rays technology and the color is identified using
vision technology (CCD linear cameras, CCPD) and spectroscopy [31, 33, 35].
Papers are usually sorted using a trommel and manual separation. There are a
number of automated optical sorting systems being developed for recycled paper such
as PaperSort developed by Magnetic Separation Systems (MSS) and Finger Screen
developed by General Kinematics Corporation (USA). The PaperSort technology
spreads the feed into a single layer using mechanical techniques and then sends
the stream to reflective sensors that identify the optical properties of the paper. An
appropriate air nozzle is activated based on the type, size and position of the paper and
automatically removes the paper from the conveyor. A full-scale PaperSort equipment
is now operating at Weyerhaeuser’s recycling plant in Baltimore. The Finger Screen
technology conveys the mixed paper stream over a series of tapered, slotted finger
elements and screens the paper without jamming. This allows for a reduction of
the volume of the paper stream and allows the system to handle a larger amount of
materials [31].
2.4.1.1 Health and Environmental Impacts of MRFs
A recycling facility can have a negative impact on the surrounding air, water and
land if it is improperly designed and operated. The sources of environmental impacts
include hazardous wastes such as lead-acid batteries, non-hazardous residual liquids,
scrap metals contaminated with cutting oils and metallic fines, etc. To prevent the
possible negative impacts and pollution problems, facilities should follow practices
such as draining and collecting waste liquids in a designated area, regularly inspecting
the operations for spills, leakages, corrosions and any signs of deteriorating structural
integrity and separating the hazardous wastes and residues from non-hazardous waste
and dispose of them accordingly. Other environmental and health impacts include
noise, odor, traffic, dust and litter. These can be controlled by fully enclosing the
receiving and processing areas, using chemical controls for odors, using air handling
and filtering equipment for dust, and addressing all other issues during the design
and operations plan [33].