- 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.
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 "set-asides," 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)
- 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
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 de-inking 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.
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