Waste recycling and reuse
WASTE MANAGEMENT AND TECHNOLOGY
Martin Kubal (Institute of Chemical Technology in Prague)
Waste recycling and reuse
Recycling means any recovery operation by which waste materials are
reprocessed into products, materials or substances whether for the original or other
purposes. It includes the reprocessing of organic material but does not include
energy recovery and the reprocessing into materials that are to be used as fuels or
for backfilling operations.
Re-use means any operation by which products or components that are not waste
are used again for the same purpose for which they were conceived.
Waste hierarchy
The following waste hierarchy shall apply as a priority order in waste prevention and
management legislation and policy:
(a) prevention;
(b) re-use;
(c) recycling;
(d) other recovery, e.g. energy recovery; and
(e) disposal.
Directive 2008/98/EC on waste, Article 3 + 4
History of waste recycling
Recycling is not a new concept. The practice of recycling has been around for
thousands of years. However, it has been affected predominantly by supply and
demand, much as it is today.
Pre-industrial Times
As for the history of recycling prior to the industrial revolution, recycling and general
household re-using was actually a commonplace practice. Before mass production
flooded the market with loads of materials and products, it was generally cheaper to
reuse items as opposed to buying new ones. In other words, during these times in
the history of recycling, recycling was mainly motivated by the economic benefits of
using recycled feedstock instead of virgin material.
Industrial Times
The history of recycling took a turn during the times of industrialization. As it became
easier and cheaper to produce goods through technological innovation and mass
production, it also became easier and sometimes cheaper to throw used items away.
Nonetheless, anytime there was a massive economic slump, people would look for
ways to make the most of what they had. For example, during the Great Depression,
people reused and recycled materials because they could not afford to buy news
items or acquire virgin materials.
LEGISLATION
ECONOMY
WASTE
RECYCLING
TECHNICAL
ASPECTS
Waste recycling - Legislation
For a recycling program to work, having a large, stable supply of recyclable
material is crucial. Three legislative options have been used to create such a supply:
mandatory recycling collection, container deposit legislation, and refuse bans.
Mandatory collection laws set recycling targets for cities to aim for, usually in the
form that a certain percentage of a material must be diverted from the city's waste
stream by a target date.
Container deposit legislation involves offering a refund for the return of certain
containers, typically glass, plastic, and metal. When a product in such a container is
purchased, a small surcharge is added to the price.
A third method of increase supply of recyclates is to ban the disposal of certain
materials as waste, often including used oil, old batteries, tires and garden waste.
One aim of this method is to create a viable economy for proper disposal of banned
products. Care must be taken that enough of these recycling services exist, or such
bans simply lead to increased illegal dumping
The Garbage Primer (ISBN-13: 978-1558212503)
Waste recycling - Legislation
Legislation has also been used to increase and maintain a demand for recycled
materials. Four methods of such legislation exist: minimum recycled content
mandates, utilization rates, procurement policies, recycled product labeling.
Both minimum recycled content mandates and utilization rates increase demand
directly by forcing manufacturers to include recycling in their operations. Content
mandates specify that a certain percentage of a new product must consist of
recycled material. Utilization rates are a more flexible option: industries are permitted
to meet the recycling targets at any point of their operation or even contract recycling
out in exchange for tradeable credits.
Governments have used their own purchasing power to increase recycling demand
through what are called "procurement policies." These policies are either "setasides," which earmark a certain amount of spending solely towards recycled
products, or "price preference" programs which provide a larger budget when
recycled items are purchased.
The final government regulation towards increased demand is recycled product
labeling. When producers are required to label their packaging with amount of
recycled material in the product (including the packaging), consumers are better able
to make educated choices. Consumers with sufficient buying power can then choose
more environmentally conscious options.
The Garbage Primer (ISBN-13: 978-1558212503)
Waste recycling - Economy
Recycling is well-known for its environmental benefits (resource conservation,
energy conservation) but it should also make economic sense.
The market is one of the main aspects to be taken into account to decide
whether a recycling process is economically viable. Both market situation and
prices ought to play a decisive role when it comes to choosing the appropriate
waste treatment process in a certain context.
The aim of the economic evaluation in recycling processes is, on the one hand,
to assess the economic impact of recycling and on the other hand, to identify
weak points, or the less economically efficient stages of the process, in order to
be improved. This data is valuable for decision support from a public and private
point of view. In regard to public organisms, it allows to select the best waste
treatment alternative. As it comes to private companies, it also provides
information about the recycling process´ profitability and recovery.
Waste recycling – Technical aspects
Special techniques are required to recycle specific materials:
- paper
- metals
- glass
- electronic waste
- plastic materials
Best available treatment recovery and recycling techniques.
Waste recycling and reuse – EU legislation
Re-use and recycling
Member States shall take measures, as appropriate, to promote the re-use
of products and preparing for re-use activities, notably by encouraging the
establishment and support of re-use and repair networks, the use of
economic instruments, procurement criteria, quantitative objectives or other
measures.
Member States shall take measures to promote high quality recycling and,
to this end, shall set up separate collections of waste where technically,
environmentally and economically practicable and appropriate to meet the
necessary quality standards for the relevant recycling sectors.
…. by 2015 separate collection shall be set up for at least the following:
paper, metal, plastic and glass.
Directive 2008/98/EC on waste, Article 11
Waste recycling and reuse – EU legislation
In order to comply with the objectives of this Directive (2008/98) , and move
towards a European recycling society with a high level of resource efficiency,
Member States shall take the necessary measures designed to achieve the
following targets:
(a) by 2020, the preparing for re-use and the recycling of waste materials such
as at least paper, metal, plastic and glass from households and possibly from
other origins as far as these waste streams are similar to waste from
households, shall be increased to a minimum of overall 50 % by weight;
(b) by 2020, the preparing for re-use, recycling and other material recovery,
including backfilling operations using waste to substitute other materials, of
non-hazardous construction and demolition waste excluding naturally
occurring material defined in category 17 05 04 in the list of waste shall be
increased to a minimum of 70 % by weight.
Directive 2008/98/EC on waste, Article 11
Examples of recycling
processes
Recycling of paper and cardboard
Paper and cardboard are produced from pulp derived from plant fibers,
primarily wood (also cotton and textiles for high-quality papers). Most of the
paper products have very short lifetimes and thus constitute a major fraction of
most waste.
The production of virgin pulp is primarily based on softwood logs of coniferous
trees like pine and spruce. The wood fiber can be extracted mechanically or
chemically.
Mechanical pulping involves mechanical wet grinding or refining of the wood
into fibers – it has a high fiber yield, but is dominated by shorter fibers.
Mechanical pulp is often bleached (traditionally with chlorine, possibly by less
harmfull chemicals, such as peroxides).
Chemical pulping uses caustic soda along with either sulfate or sulfite to extract
the cellulose fibers from lignin during high-pressure cooking. Chemical pulping
has a lower fiber yield than the mechanical pulping but the retrieved fibers are
longer. Chemical pulp is bleached similarly to the mechanical process.
The pulp is further processed (in a dilute suspension – about 1% fiber) on
paper machines, where it is shaped, dewatered, compressed and dried.
Paper and cardboard remanufacturing
Recycled paper and carboard can be used as a single raw material in pulp
or integrated pulp and paper mills or mixed in with virgin raw materials. In
all cases, the recycled paper and cardboard goes through a cleaning
process, which always includes mechanical cleaning and in some cases deinking and bleaching. The re-pulping can be mechanical or chemical.
Both re-pulping processes wash out some of the fillers and coatings used
(starch, titanium oxides, kaolin) removes ink as sludge and loses some of
the undersized fibers to the wastewater. The shortening of fibers during
re-pulping induces a quality loss, in particular with respect to strength,
which requires that recycled paper to maintain strength must increase the
weight per area by 5 – 15%. Alternatively, long fibered virgin pulp is mixed
in with the recycled pulp.
Paper and cardboard remanufacturing
Mechanical re-pulping is used for less demanding paper qualities such as
brown paper, egg containers, etc.. Mechanical re-pulping typically consists
of the following steps:
- Precleaning (mechanical) removes solid foreign items using centrifuges
and pressure sorters.
- Refining provides washing, sorting and milling of the pulp.
- Final cleaning (mechanical) removes items released in the refining step.
- Thickening reduces the water content and allows for storing
- Drying.
Paper and cardboard remanufacturing
Chemical re-pulping is used for higher-quality products requiring the removal
of ink and maybe bleaching. Chemical re-pulping typically consists of the
following steps:
- Precleaning (mechanical) to remove solid foreign items, using centrifuges
and pressure sorters.
- Feeding and pulping including pH adjustment (caustic soda, aluminium
sulfates) and addition of dispersing agent (e.g. glycol ether).
- Refining to provide washing, sorting and milling the pulp.
- De-inking and pigment removal by chemical (NaOH, sodium silicate,
hydrogen peroxide, soaps or fatty acids, chelating agents) and mechanical
(flotation) treatment steps.
- Final cleaning (mechanical).
- Thickening and bleaching (optional) and storing.
- Drying.
Recycling of paper and cardboard
Market considerations
Recycled paper is an important part of the raw material used in the pulp and paper
industry and is traded on a market that is global. The consumption and production is
though fragmented globally and there are large differences in the consumption
(Africa: 8 kg/person/year, North America: 211 kg/person/year).
Table: Paper production in Europe in 2004
paper production
content of recycled
(1000 t)
paper (%)
__________________________________________________________
Newspaper
11 048
80.1
Other graphical paper
37 956
8.7
Case material
22 136
91.8
Cartoon boards
7 944
41.5
Other paper and board
4 225
85.4
for packaging
Recycling of paper and cardboard
Fiber flows in paper and board production, EU
2004, million tonnes)
Recycling of paper and cardboard
Environmental considerations
Several studies on paper recycling in comparison to incineration and landfilling
and with paper production from virgin raw materials as reference have
concluded that recycling is beneficial from an environmental point of view. The
key issues regarding the recycling of paper are:
- Which virgin production of paper does the recycled paper substitute? The
important issue here is the energy profile of the pulp and paper mill. Do the
mills use biomass for the production of energy (which is typical for chemical
pulp mills) or do the mills use electricity from the grid (which is typical for
mechanical pulp mills)?
- What happens to the logs which, due to paper recycling, are no longer
needed for the paper mill? Do they find use as biomass fuel or do they just
continue in the natural cycle of the forest and degrade into carbon dioxide over
time.
Solid Waste Technology  Managament, ISBN 978-1-4051-7517-3
Recycling of metals (iron + aluminium)
Metals like iron and aluminium are produced from mineral ore and used for
a range of products, some of which have very short lifetimes and thus
constitute a major fraction of municipal waste. Other products like
appliances, vehicles and buildings containing iron and aluminium metals,
have long lifetimes before they end up in the waste stream.
The recycling of production waste and postconsumer metals has a long
history in the metal industry. Some metal smelters are today entirely based
on scrap metals.
Recycling of metals (iron and steel production)
After iron ore has been mined, the ore is concentrated by crushing, grinding
and magnetic separation, at which stage the residual rock is removed. The
concentrated ore is sintered at 1200 – 1300oC to make pellets and fines.
Reduction of the refined ore takes place in a blast furnace using coke as a
reducing agent. Lime is added as well. The pig iron resulting from the blast
furnace is afterward smelted at 1600oC in a secondary smelter, for example
an electrical furnace. The molten steel is cast into ingots or rolled (hot and
cold) to produce sheets. Iron production is energy-demanding and creates
large amounts of tailings (waste ore rock pilings).
The steel industry converts the iron into products used by other industries
and in private consumption:
Plate products, strip products, long products
Recycling of metals (aluminium production)
Aluminium oxides and hydroxides make up 20 – 30% of bauxite, primarily
mined in open mines in Australia, Guinea, Brazil and Jamaica. Bauxite is
crushed and sand and clay is washed away. In the smelter the finely
crushed bauxite is heated (200oC) in a caustic solution (NaOH) under
pressure (up to 3.5 MPa). Alumina is dissolved in the solution while the other
compounds settle out. Afterwards the alumina is precipitated and converted
to alumina oxides by heating. Metallic alumina is afterwards obtained at the
cathode of an electrolytic salt melt containing cryolite (Na3AlF6) at 960oC.
Molten aluminium is drawn from the bottom of the reactor and cast into
ingots. The ingots are afterwards rolled into sheets. Aluminium production is
extremely energy-demanding and leaves large open scars in the landscape.
Metals remanufacturing
The types of waste steel and aluminium being recycled are:
- Metal scrap originating from industry, construction and demolition all over
the world are collected, sorted and baled by scraper dealers, who sell it to
smelters.
- End-of-life vehicles, appliance, white goods etc., are typically taken apart
and the metal parts, shredded, sorted (magnetic and eddy-current
separators) and cleaned before being baled for sale on the world market.
- Postconsumer waste in terms of packaging and small metal things
discarded in the municipal waste may be separately collected or recovered
as scrap from an MBT plant or from the bottom ash of incinerators. This
postconsumer metal scrap is the least attractive of the sources of scrap
metal because it is very mixed and not clean. However, it may still be
recycled or utilized.
Iron and steel remanufacturing
The main problem in steel recycling is the cleanliness of scrap with respect
to primary steel, other metals and alloys. This is a particular problem with
post-consumer waste: the tin content of tin cans is too high to allow
recycling of large quantities in steel smelters that produce high quality steel.
Steel cans may also be used in copper production. Steel cans with their
large surface to weight ration are well suited for reducing copper sulfate to
matalic copper and ferrous sulfate.
There are in principle two processes for recycling iron and steel, either
through a basic oxygen furnace (BOF) or through an electric arc furnace
(EAF). The BOA process only accepts 25-30% of scrap steel, of which the
majority is inhouse scrap which is steel scrap originating from the
production of the steel ingots, sheets, rolls themselves or new scrap from
cut-offs during the shaping in steel product fabrication. EAFs in contrast
accept 100% steel scrap and this is therefore the predominant way of
recycling the scrap steel.
Aluminium remanufacturing
Aluminium scrap may be remanufactured by returning the scrap to the cast
stage (only clean scrap) or alternatively to the electrolysis step. Aluminium
recycling mainly takes place in rotary or reverbatory furnaces. Aluminium
scrap from municipal waste such as used in beverage cans and foils is
pretreated in order to remove contaminants or to de-coat or de-oil the scrap
depending on source. This improves the thermal efficiency of the recycling
and reduces potential emissions from the melting process.
The scrap is then loaded into the furnaces. There are a number of different
furnace setups depending on the quality of the aluminium scrap. From the
furnace the melted aluminium is tapped for either direct casting or sent to
another furnace where alloys can be made. In this process the aluminium is
also refined to remove the last impurities in the aluminium. The aluminium
recycling process uses only around 5% of the energy needed for the
virgin aluminium production, as the alumina conversion in virgin production
is where the majority of the energy is used.
Market consideration
The consumption of steel and aluminium varies considerably from country
to country. In the EU the average consumption of metal packaging is 9.8
kg/person/year, but this covers consumption rates as low as 3.1
kg/person/year up to 16.4 kg/person/year. The recovery rate varies from
22% in Cyprus up to 88% in Belgium, although the two countries have
similar consumption of aluminium packaging.
Environmental considerations
Several studies on metal scrap recycling in comparison to incineration and
landfilling and with metal production from virgin materials as reference
have concluded that from an environmental point of view recycling is
beneficial. The key issues regarding the recycling of metals are:
- The virgin materials for steel and aluminium production are limited and
are not easily accessible. The energy costs of extracting the raw materials
for the production is therefore very high and furthermore the energy costs
for processing the metals are very high. Through the remelting of the metal
scraps significant energy savings are thus obtained, which makes room for
even long-distance bulk transport of the metals around the world.
- Metal has really no major function in an incinerator (negligible energy
content) and is practically inert in a landfill. However in both cases the
metal takes up capacity in the system.
Solid Waste Technology  Managament, ISBN 978-1-4051-7517-3
Questions to exam
- Definition of recycling.
- Definition of re-use.
- Legislative options to ensure stable supply of recyclable material (mandatory
collection, container deposit, restrictions to disposal).
- Legislative options to increase demand for recycled materials (minimum recycled
content mandates, utilization rates, procurement policies, recycled product
labeling).
- Paper recycling.
- Steel and aluminium recycling.