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| Recycling symbol. |
Recycling
Recycling is the process of converting waste materials
into new materials and objects. It is an alternative to
"conventional" waste disposal that can save material and
help lower greenhouse gas emissions. Recycling can
prevent the waste of potentially useful materials and
reduce the consumption of fresh raw materials, thereby
reducing: energy usage, air pollution (from
incineration), and water pollution (from landfilling).
Recycling is a key component of modern waste reduction
and is the third component of the "Reduce, Reuse, and
Recycle" waste hierarchy. Thus, recycling aims at
environmental sustainability by substituting raw
material inputs into and redirecting waste outputs out
of the economic system.
There are some ISO standards related to recycling such
as ISO 15270:2008 for plastics waste and ISO 14001:2015
for environmental management control of recycling
practice. |
 |
| Glass recovered by
crushing only one kind of beer bottle. |
Recyclable materials include many kinds of glass, paper,
cardboard, metal, plastic, tires, textiles, batteries,
and electronics. The composting or other reuse of
biodegradable waste—such as food or garden waste—is also
a form of recycling. Materials to be recycled are either
delivered to a household recycling center or picked up
from curbside bins, then sorted, cleaned, and
reprocessed into new materials destined for
manufacturing new products.
In the strictest sense, recycling of a material would
produce a fresh supply of the same material—for example,
used office paper would be converted into new office
paper or used polystyrene foam into new polystyrene.
This is accomplished when recycling certain types of
materials, such as metal cans, which can become a can
again and again, infinitely, without losing purity in
the product. However, this is often difficult or too
expensive (compared with producing the same product from
raw materials or other sources), so "recycling" of many
products or materials involves their reuse in producing
different materials (for example, paperboard) instead.
Another form of recycling is the salvage of certain
materials from complex products, either due to their
intrinsic value (such as lead from car batteries, or
gold from printed circuit boards), or due to their
hazardous nature (e.g., removal and reuse of mercury
from thermometers and thermostats). |
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| Recycling bins in
Japan. |
History
Origins
Recycling has been a common practice for most of human
history, with recorded advocates as far back as Plato in
the fourth century BC. During periods when resources
were scarce and hard to come by, archaeological studies
of ancient waste dumps show less household waste (such
as ash, broken tools, and pottery)—implying more waste
was being recycled in the absence of new material.
In pre-industrial times, there is evidence of scrap
bronze and other metals being collected in Europe and
melted down for perpetual reuse. Paper recycling was
first recorded in 1031 when Japanese shops sold repulped
paper. In Britain dust and ash from wood and coal fires
was collected by "dustmen" and downcycled as a base
material used in brick making. The main driver for these
types of recycling was the economic advantage of
obtaining recycled feedstock instead of acquiring virgin
material, as well as a lack of public waste removal in
ever more densely populated areas. In 1813, Benjamin Law
developed the process of turning rags into "shoddy" and
"mungo" wool in Batley, Yorkshire. This material
combined recycled fibers with virgin wool. The West
Yorkshire shoddy industry in towns such as Batley and
Dewsbury lasted from the early 19th century to at least
1914.
Industrialization spurred demand for affordable
materials; aside from rags, ferrous scrap metals were
coveted as they were cheaper to acquire than virgin ore.
Railroads both purchased and sold scrap metal in the
19th century, and the growing steel and automobile
industries purchased scrap in the early 20th century.
Many secondary goods were collected, processed and sold
by peddlers who scoured dumps and city streets for
discarded machinery, pots, pans, and other sources of
metal. By World War I, thousands of such peddlers roamed
the streets of American cities, taking advantage of
market forces to recycle post-consumer materials back
into industrial production.
Beverage bottles were recycled with a refundable deposit
at some drink manufacturers in Great Britain and Ireland
around 1800, notably Schweppes. An official recycling
system with refundable deposits was established in
Sweden for bottles in 1884 and aluminum beverage cans in
1982; the law led to a recycling rate for beverage
containers of 84–99 percent depending on type, and a
glass bottle can be refilled over 20 times on average.
Wartime
New chemical industries created in the late 19th century
both invented new materials (e.g. Bakelite [1907]) and
promised to transform valueless into valuable materials.
Proverbially, you could not make a silk purse of a sow's
ear—until the US firm Arthur D. Little published in 1921
"On the Making of Silk Purses from Sows' Ears", its
research proving that when "chemistry puts on overalls
and gets down to business ... new values appear. New and
better paths are opened to reach the goals desired."
Recycling (or "salvage", as it was then usually known)
was a major issue for governments throughout World War
II. Financial constraints and significant material
shortages due to war efforts made it necessary for
countries to reuse goods and recycle materials. These
resource shortages caused by the world wars, and other
such world-changing occurrences, greatly encouraged
recycling. The struggles of war claimed much of the
material resources available, leaving little for the
civilian population. It became necessary for most homes
to recycle their waste, as recycling offered an extra
source of materials allowing people to make the most of
what was available to them. Recycling household
materials meant more resources for war efforts and a
better chance of victory. Massive government promotion
campaigns, such as the National Salvage Campaign in
Britain and the Salvage for Victory campaign in the
United States, were carried out on the home front in
every combative nation, urging citizens to donate metal,
paper, rags, and rubber as a matter of patriotism.
Post-World War II
A considerable investment in recycling occurred in the
1970s, due to rising energy costs. Recycling aluminum
uses only 5% of the energy required by virgin
production; glass, paper and other metals have less
dramatic but very significant energy savings when
recycled feedstock is used.
Although consumer electronics such as the television
have been popular since the 1920s, recycling of them was
almost unheard of until early 1991. The first electronic
waste recycling scheme was implemented in Switzerland,
beginning with collection of old refrigerators but
gradually expanding to cover all devices. After these
schemes were set up, many countries did not have the
capacity to deal with the sheer quantity of e-waste they
generated or its hazardous nature. They began to export
the problem to developing countries without enforced
environmental legislation. This is cheaper, as recycling
computer monitors in the United States costs 10 times
more than in China. Demand in Asia for electronic waste
began to grow when scrap yards found that they could
extract valuable substances such as copper, silver,
iron, silicon, nickel, and gold, during the recycling
process. The 2000s saw a large increase in both the sale
of electronic devices and their growth as a waste
stream: in 2002, e-waste grew faster than any other type
of waste in the EU. This caused investment in modern,
automated facilities to cope with the influx of
redundant appliances, especially after strict laws were
implemented in 2003.
In 2018, changes in the recycling market have sparked a
global "crisis" in the industry. On December 31, 2017,
China announced its "National Sword" policy, setting new
standards for imports of recyclable material and banning
materials that were deemed too "dirty" or "hazardous".
The new policy caused drastic disruptions in the global
market in recycling and reduced the prices of scrap
plastic and low-grade paper. Exports of recyclable
materials from G7 countries to China dropped
dramatically, with many exports shifting to countries in
southeast Asia. The crisis generated significant concern
about the practices and environmental sustainability of
the recycling industry. The abrupt shift caused
countries to accept more recyclable materials than they
could process, raising fundamental questions about
shipping recycling waste from economically developed
countries to countries with few environmental
regulations—a practice that predated the crisis.
Recyclates
"Recyclate" is a raw material that is sent to, and
processed in a waste recycling plant or materials
recovery facility which will be used to form new
products. The material is collected in various methods
and delivered to a facility where it undergoes
re-manufacturing so that it can be used in the
production of new materials or products. For example,
plastic bottles that are collected can be re-used and
made into plastic pellets, a new product.
Quality of recyclate
The quality of recyclates is recognized as one of the
principal challenges that needs to be addressed for the
success of a long-term vision of a green economy and
achieving zero waste. Recyclate quality is generally
referring to how much of the raw material is made up of
target material compared to the amount of non-target
material and other non-recyclable material. For example,
steel and metal are materials with a higher recyclate
quality. It’s estimated that two thirds of all new steel
manufactured comes from recycled steel. Only target
material is likely to be recycled, so a higher amount of
non-target and non-recyclable material will reduce the
quantity of recycling product. A high proportion of
non-target and non-recyclable material can make it more
difficult for re-processors to achieve "high-quality"
recycling. If the recyclate is of poor quality, it is
more likely to end up being down-cycled or, in more
extreme cases, sent to other recovery options or
landfilled. For example, to facilitate the
re-manufacturing of clear glass products there are tight
restrictions for colored glass going into the re-melt
process. Another example is the downcycling of plastic,
in which products such as plastic food packaging are
often downcycled into lower quality products, and do not
get recycled into the same plastic food packaging.
The quality of recyclate not only supports high-quality
recycling, but it can also deliver significant
environmental benefits by reducing, reusing and keeping
products out of landfills. High-quality recycling can
help support growth in the economy by maximizing the
economic value of the waste material collected. Higher
income levels from the sale of quality recyclates can
return value which can be significant to local
governments, households, and businesses. Pursuing
high-quality recycling can also provide consumer and
business confidence in the waste and resource management
sector and may encourage investment in that sector.
There are many actions along the recycling supply chain
that can influence and affect the material quality of
recyclate. It begins with the waste producers who place
non-target and non-recyclable wastes in recycling
collection. This can affect the quality of final
recyclate streams or require further efforts to discard
those materials at later stages in the recycling
process. The different collection systems can result in
different levels of contamination. Depending on which
materials are collected together, extra effort is
required to sort this material back into separate
streams and can significantly reduce the quality of the
final product. Transportation and the compaction of
materials can make it more difficult to separate
material back into separate waste streams. Sorting
facilities are not one hundred per cent effective in
separating materials, despite improvements in technology
and quality recyclate which can see a loss in recyclate
quality. The storage of materials outside, where the
product can become wet, can cause problems for
re-processors. Reprocessing facilities may require
further sorting steps to further reduce the amount of
non-target and non-recyclable material. Each action
along the recycling path plays a part in the quality of
recyclate.
Quality recyclate action
plan (Scotland)
The Recyclate Quality Action Plan of Scotland sets out a
number of proposed actions that the Scottish Government
would like to take forward in order to drive up the
quality of the materials being collected for recycling
and sorted at materials recovery facilities before being
exported or sold on to the reprocessing market.
The plan's objectives are to: |
- Drive up the quality of recyclate
- Deliver greater transparency about
the quality of recyclate
- Provide help to those contracting
with materials recycling facilities to identify what is
required of them
- Ensure compliance with the Waste
(Scotland) regulations 2012
- Stimulate a household market for
quality recyclate
- Address and reduce issues
surrounding the Waste Shipment Regulations
The plan focuses on three key areas, with fourteen
actions which were identified to increase the quality of
materials collected, sorted and presented to the
processing market in Scotland.
|
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The three areas of focus are: |
- Collection systems and input
contamination
- Sorting facilities – material
sampling and transparency
- Material quality benchmarking and
standards
|
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Recycling consumer waste
Collection
A number of different systems have been implemented to
collect recyclates from the general waste stream. These
systems lie along the spectrum of trade-off between
public convenience and government ease and expense. The
three main categories of collection are "drop-off
centers", "buy-back centers", and "curbside collection".
Curbside collection
Curbside collection encompasses many subtly different
systems, which differ mostly on where in the process the
recyclates are sorted and cleaned. The main categories
are mixed waste collection, commingled recyclables, and
source separation. A waste collection vehicle generally
picks up the waste.
At one end of the spectrum is mixed waste collection, in
which all recyclates are collected mixed in with the
rest of the waste, and the desired material is then
sorted out and cleaned at a central sorting facility.
This results in a large amount of recyclable waste,
paper especially, being too soiled to reprocess, but has
advantages as well: the city need not pay for a separate
collection of recyclates and no public education is
needed. Any changes to which materials are recyclable is
easy to accommodate as all sorting happens in a central
location.
In a commingled or single-stream system, all recyclables
for collection are mixed but kept separate from other
waste. This greatly reduces the need for post-collection
cleaning but does require public education on what
materials are recyclable.
Source separation
Source separation is the other extreme, where each
material is cleaned and sorted prior to collection. This
method requires the least post-collection sorting and
produces the purest recyclates, but incurs additional
operating costs for collection of each separate
material. An extensive public education program is also
required, which must be successful if recyclate
contamination is to be avoided. In Oregon, USA, its
environmental authority Oregon DEQ surveyed multi-family
property managers and about half of them reported
problems including contamination of recyclables due to
trespassers such as transients gaining access to the
collection areas.
Source separation used to be the preferred method due to
the high sorting costs incurred by commingled (mixed
waste) collection. However, advances in sorting
technology have lowered this overhead substantially.
Many areas which had developed source separation
programs have since switched to what is called
co-mingled collection.
Buy-back centers
Buy-back centers differ in that the cleaned recyclates
are purchased, thus providing a clear incentive for use
and creating a stable supply. The post-processed
material can then be sold. If this is profitable, this
conserves the emission of greenhouse gases; if
unprofitable, it increases the emission of greenhouse
gasses. Government subsidies are necessary to make
buy-back centres a viable enterprise. In 1993, according
to the U.S. National Waste & Recycling Association, it
costs on average $50 to process a ton of material, which
can be resold for $30.
In the US, the value per ton of mixed recyclables was
$180 in 2011, $80 in 2015, and $100 in 2017.
In 2017, glass is essentially valueless, because of the
low cost of sand, its major component; low oil costs
thwarts plastic recycling.
In 2017, Napa, California was reimbursed about 20% of
its costs in recycling.
Drop-off centers
Drop-off centers require the waste producer to carry the
recyclates to a central location, either an installed or
mobile collection station or the reprocessing plant
itself. They are the easiest type of collection to
establish but suffer from low and unpredictable
throughput.
Distributed recycling
For some waste materials such as plastic, recent
technical devices called recyclebots enable a form of
distributed recycling. Preliminary life-cycle analysis
(LCA) indicates that such distributed recycling of HDPE
to make filament of 3D printers in rural regions is
energetically favorable to either using virgin resin or
conventional recycling processes because of reductions
in transportation energy.
Sorting
Once commingled recyclates are collected and delivered
to a materials recovery facility, the different types of
materials must be sorted. This is done in a series of
stages, many of which involve automated processes such
that a truckload of material can be fully sorted in less
than an hour. Some plants can now sort the materials
automatically, known as single-stream recycling.
Automatic sorting may be aided by robotics and
machine-learning. In plants, a variety of materials is
sorted such as paper, different types of plastics,
glass, metals, food scraps, and most types of batteries.
A 30 percent increase in recycling rates has been seen
in the areas where these plants exist. In the United
States, there are over 300 materials recovery
facilities.
Initially, the commingled recyclates are removed from
the collection vehicle and placed on a conveyor belt
spread out in a single layer. Large pieces of corrugated
fiberboard and plastic bags are removed by hand at this
stage, as they can cause later machinery to jam.
Next, automated machinery such as disk screens and air
classifiers separate the recyclates by weight, splitting
lighter paper and plastic from heavier glass and metal.
Cardboard is removed from the mixed paper and the most
common types of plastic, PET (#1) and HDPE (#2), are
collected. This separation is usually done by hand but
has become automated in some sorting centers: a
spectroscopic scanner is used to differentiate between
different types of paper and plastic based on the
absorbed wavelengths, and subsequently divert each
material into the proper collection channel.
Strong magnets are used to separate out ferrous metals,
such as iron, steel, and tin cans. Non-ferrous metals
are ejected by magnetic eddy currents in which a
rotating magnetic field induces an electric current
around the aluminum cans, which in turn creates a
magnetic eddy current inside the cans. This magnetic
eddy current is repulsed by a large magnetic field, and
the cans are ejected from the rest of the recyclate
stream.
Finally, glass is sorted according to its color: brown,
amber, green, or clear. It may either be sorted by hand,
or via an automated machine that uses colored filters to
detect different colors. Glass fragments smaller than 10
millimetres (0.39 in) across cannot be sorted
automatically, and are mixed together as "glass fines".
This process of recycling as well as reusing the
recycled material has proven advantageous because it
reduces amount of waste sent to landfills, conserves
natural resources, saves energy, reduces greenhouse gas
emissions, and helps create new jobs. Recycled materials
can also be converted into new products that can be
consumed again, such as paper, plastic, and glass.
The City and County of San Francisco's Department of the
Environment is attempting to achieve a citywide goal of
generating zero waste by 2020. San Francisco's refuse
hauler, Recology, operates an effective recyclables
sorting facility which helped the city reach a
record-breaking diversion rate of 80%.
Recycling industrial waste
Although many government programs are concentrated on
recycling at home, 64% of waste in the United Kingdom is
generated by industry. The focus of many recycling
programs done by industry is the cost–effectiveness of
recycling. The ubiquitous nature of cardboard packaging
makes cardboard a commonly recycled waste product by
companies that deal heavily in packaged goods, like
retail stores, warehouses, and distributors of goods.
Other industries deal in niche or specialized products,
depending on the nature of the waste materials that are
present.
The glass, lumber, wood pulp and paper manufacturers all
deal directly in commonly recycled materials; however,
old rubber tires may be collected and recycled by
independent tire dealers for a profit.
Levels of metals recycling are generally low. In 2010,
the International Resource Panel, hosted by the United
Nations Environment Programme (UNEP) published reports
on metal stocks that exist within society and their
recycling rates. The Panel reported that the increase in
the use of metals during the 20th and into the 21st
century has led to a substantial shift in metal stocks
from below ground to use in applications within society
above ground. For example, the in-use stock of copper in
the USA grew from 73 to 238 kg per capita between 1932
and 1999.
The report authors observed that, as metals are
inherently recyclable, the metal stocks in society can
serve as huge mines above ground (the term "urban
mining" has been coined with this idea in mind).
However, they found that the recycling rates of many
metals are very low. The report warned that the
recycling rates of some rare metals used in applications
such as mobile phones, battery packs for hybrid cars and
fuel cells, are so low that unless future end-of-life
recycling rates are dramatically stepped up these
critical metals will become unavailable for use in
modern technology.
The military recycles some metals. The U.S. Navy's Ship
Disposal Program uses ship breaking to reclaim the steel
of old vessels. Ships may also be sunk to create an
artificial reef. Uranium is a very dense metal that has
qualities superior to lead and titanium for many
military and industrial uses. The uranium left over from
processing it into nuclear weapons and fuel for nuclear
reactors is called depleted uranium, and is used by all
branches of the U.S. military for the development of
such things as armour-piercing shells and shielding.
The construction industry may recycle concrete and old
road surface pavement, selling their waste materials for
profit.
Some industries, like the renewable energy industry and
solar photovoltaic technology, in particular, are being
proactive in setting up recycling policies even before
there is considerable volume to their waste streams,
anticipating future demand during their rapid growth.
Recycling of plastics is more difficult, as most
programs are not able to reach the necessary level of
quality. Recycling of PVC often results in downcycling
of the material, which means only products of lower
quality standard can be made with the recycled material.
A new approach which allows an equal level of quality is
the Vinyloop process. It was used after the London
Olympics 2012 to fulfill the PVC Policy.
E-waste recycling
E-waste is a growing problem, accounting for 20–50
million metric tons of global waste per year according
to the EPA. It is also the fastest growing waste stream
in the EU. Many recyclers do not recycle e-waste
responsibly. After the cargo barge Khian Sea dumped
14,000 metric tons of toxic ash in Haiti, the Basel
Convention was formed to stem the flow of hazardous
substances into poorer countries. They created the
e-Stewards certification to ensure that recyclers are
held to the highest standards for environmental
responsibility and to help consumers identify
responsible recyclers. This works alongside other
prominent legislation, such as the Waste Electrical and
Electronic Equipment Directive of the EU the United
States National Computer Recycling Act, to prevent
poisonous chemicals from entering waterways and the
atmosphere.
In the recycling process, television sets, monitors,
cell phones, and computers are typically tested for
reuse and repaired. If broken, they may be disassembled
for parts still having high value if labor is cheap
enough. Other e-waste is shredded to pieces roughly 10
centimetres (3.9 in) in size, and manually checked to
separate out toxic batteries and capacitors which
contain poisonous metals. The remaining pieces are
further shredded to 10 millimetres (0.39 in) particles
and passed under a magnet to remove ferrous metals. An
eddy current ejects non-ferrous metals, which are sorted
by density either by a centrifuge or vibrating plates.
Precious metals can be dissolved in acid, sorted, and
smelted into ingots. The remaining glass and plastic
fractions are separated by density and sold to
re-processors. Television sets and monitors must be
manually disassembled to remove lead from CRTs or the
mercury backlight from LCDs.
Plastic recycling
Plastic recycling is the process of recovering scrap or
waste plastic and reprocessing the material into useful
products, sometimes completely different in form from
their original state. For instance, this could mean
melting down soft drink bottles and then casting them as
plastic chairs and tables. For some types of plastic,
the same piece of plastic can only be recycled about 2-3
times before its quality decreases to the point where it
can no longer be used.
Physical recycling
Some plastics are remelted to form new plastic objects;
for example, PET water bottles can be converted into
polyester destined for clothing. A disadvantage of this
type of recycling is that the molecular weight of the
polymer can change further and the levels of unwanted
substances in the plastic can increase with each remelt.
Chemical recycling
For some polymers, it is possible to convert them back
into monomers, for example, PET can be treated with an
alcohol and a catalyst to form a dialkyl terephthalate.
The terephthalate diester can be used with ethylene
glycol to form a new polyester polymer, thus making it
possible to use the pure polymer again. In 2019, Eastman
Chemical Company announced initiatives of methanolysis
and syngas designed to handle a greater variety of used
material.
Waste plastic pyrolysis to
fuel oil
Another process involves the conversion of assorted
polymers into petroleum by a much less precise thermal
depolymerization process. Such a process would be able
to accept almost any polymer or mix of polymers,
including thermoset materials such as vulcanized rubber
tires and the biopolymers in feathers and other
agricultural waste. Like natural petroleum, the
chemicals produced can be used as fuels or as feedstock.
A RESEM Technology plant of this type in Carthage,
Missouri, US, uses turkey waste as input material.
Gasification is a similar process but is not technically
recycling since polymers are not likely to become the
result. Plastic Pyrolysis can convert petroleum based
waste streams such as plastics into quality fuels,
carbons. Given below is the list of suitable plastic raw
materials for pyrolysis: |
- Mixed plastic (HDPE, LDPE, PE, PP,
Nylon, Teflon, PS, ABS, FRP, etc.)
- Mixed waste plastic from waste paper
mill
- Multi-layered plastic
|
|
Recycling loops
The (ideal) recycling process can be differentiated into
three loops, one for manufacture (production-waste
recycling) and two for disposal of the product (product
and material recycling).
The product's manufacturing phase, which consists of
material processing and fabrication, forms the
production-waste recycling loop. Industrial waste
materials are fed back into, and reused in, the same
production process.
The product's disposal process requires two recycling
loops: product recycling and material recycling. The
product or product parts are reused in the product
recycling phase. This happens in one of two ways: the
product is used retaining the product functionality
("reuse") or the product continues to be used but with
altered functionality ("further use"). The product
design is unmodified, or only slightly modified, in both
scenarios.
Product disassembly requires material recycling where
product materials are recovered and recycled. Ideally,
the materials are processed so they can flow back into
the production process.
Recycling codes
In order to meet recyclers' needs while providing
manufacturers a consistent, uniform system, a coding
system was developed. The recycling code for plastics
was introduced in 1988 by the plastics industry through
the Society of the Plastics Industry. Because municipal
recycling programs traditionally have targeted
packaging—primarily bottles and containers—the resin
coding system offered a means of identifying the resin
content of bottles and containers commonly found in the
residential waste stream.
Plastic products are printed with numbers 1–7 depending
on the type of resin. Type 1 (polyethylene terephthalate)
is commonly found in soft drink and water bottles. Type
2 (high-density polyethylene) is found in most hard
plastics such as milk jugs, laundry detergent bottles,
and some dishware. Type 3 (polyvinyl chloride) includes
items such as shampoo bottles, shower curtains, hula
hoops, credit cards, wire jacketing, medical equipment,
siding, and piping. Type 4 (low-density polyethylene) is
found in shopping bags, squeezable bottles, tote bags,
clothing, furniture, and carpet. Type 5 is polypropylene
and makes up syrup bottles, straws, Tupperware, and some
automotive parts. Type 6 is polystyrene and makes up
meat trays, egg cartons, clamshell containers, and
compact disc cases. Type 7 includes all other plastics
such as bulletproof materials, 3- and 5-gallon water
bottles, cell phone and tablet frames, safety goggles
and sunglasses. Having a recycling code or the chasing
arrows logo on a material is not an automatic indicator
that a material is recyclable but rather an explanation
of what the material is. Types 1 and 2 are the most
commonly recycled. |
|
 Kiddle: Recycling
Wikipedia: Recycling |
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