RECYCLING in waste management

Total waste production in EU countries

• Total amount of 2.62 billion tonnes (2008)

• European Parliament passed a resolution on Resource Efficien Europe (zero waste by 2020)

Source: Eurostat

Per capita waste generation in EU by individual countries

Per capita hazardous waste generation in EU by individual countries

Municipal solid waste (MSW) composition in EU

Total amount: 221 million tonnes

MSW composition for the USTotal MSW generation: 234 million tonnes

Source: US EPA

State of the art: landfilling• Health and sanitary risks at dump sites, and at their vicinity

(microorganisms, insects, rodents)• Groundwater contamination by landfill leachate, incl. heavy

metals and pesticides• Airborne pollution on burning and incineration• Release of greenhouse gases (CH4, CO2, etc.)• The problem can be at least partially solved by recycling

Recovery options for various waste: an American case study

Paper

Glass

Steel

AluminiumPlas

tics

Rubber and le

ather

Textile

WoodFo

od0

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90Production, mln tonnesRecycling, mln tonnes The lowest

recovery:• Plastics• Food waste

US EPA, 2005

Recycling development• First recorded ideas on recycling

originated from Plato (ca. 400 BC)• Archeology shows that recycling

was popular in the antiquity (why?)• 18th-19th centuries – recycling of

dust and ash from burning wood and coal (bricks), scrap metal, glass• World Wars – literally everything• Next upsurge – 1970s (greatly

increased prices for oil and energy)• Increased environmental awareness

Proposed complete recycling schemeCollection

Sorting at conveyor beltOrganics + rejects

PaperMetal Textile

Glass

Plastics

Press Crushing

Composting

Rejects Compost

Bricks, interlocks, wheels, tables, manholes, road ramps, etc.

Sand

Thin filmplastics

Hardplastics

Paper recycling

Paper recycling stages• Paper sorting• Metal removal by magnet (staples etc.)• Pulping• Cleaning and screening• De-inking• froth flotation• wash deinking (detergent addition)

• Washing• Bleaching• Paper production• It is considered (US EPA, 2012) that paper can be recycled 5-7

times before cellulose fibres become too short

Paper sorting: main paper categories

• High-grade paper for printing and writing• Newsprint• Paperboard and packaging paper• Tissues and paper towels

• De-inking is required for most paper types in course of recycling

Pulping and screening• Mechanical defragmentation• pH adjusted to 8.5-10• H2O2 / O3 for bleaching• Ca2+ compunds as fillers• Fatty acids/soap• Obtained slurry undergoes

centrifugal cleaning and screening to remove particles heavier and larger than pulp fibres

De-inking: froth flotation

• Chemicals can be added to faciliate ink removal

• This is done primarily in tissue paper production

Image source: en.wikipedia.org

Recycling 1 t of paper saves:• 1 t of wood (ca 17 trees)• 26 m3 of water• 320 L of oil• 4100 kW h of energy (6-months consumption of an average US

house)• 2.3 m3 of landfill space

Plastic recycling

Most commonly used plastic types• PET/PETE (polyethylene terephtalate) – soft drink bottles, food

containers• HDPE (high density polyethylene) – bottles for beverages with

short life (milk, juices)• LDPE (low-density PE) – cable insulation, flexible bottles• PVC (polyvinylchloride), V (vinyl) – packaging sheets, wire and

cable insulation, floor tiles• PP (polypropylene) – packaging film, bottles for hot liquids• PS (polystyrene) – protective packaging

Basic recycling steps• Cleaning (hot water)• Sorting • Cutting• Shredding• Agglomeration• Pelletizing• Reprocessing

Plastic waste

Washing

Sorting

Agglomeration Shredding

Pelletizing

Injection molding Film blowing Extrusion

Sorting plastic types• Water-alcohol solution:• = 925 kg m-3: HDPE sinks, PP floats• = 930 kg m-3: HDPE sinks, LDPE floats

• Water-salt solution:- separating PS (polystyrene) and PVC

• Resin identification code (RIC)• Near-infrared analysis (NIR)

Resin identification code

PET PP

HDPE PS

PVC Other

LDPE

A few words on infrared analysis

Graph: Khayet et al., J. Membr. Sci. 263 (2005) 77-95Spectrometers: Google

Extrusion

1. rotating screw2. plastic pellets

addition3. breaker plate4. extruded plastic

Image source: en.wikipedia.org

Injection molding

Film blowing

http://www.hipf.edu.sa/HIPF_English/Courses-BFE.html

Thermal depolymerisation (TDP)• Plastic waste is cut or shredded• Water addition• Temperature risen to 250 C at constant volume, pressure rises to

4 MPa, 15 min• Pressure is released, water evaporates• Second stage reactor: 500 C, breaking up long hydrocarbon

chains• Destillation• Light crude oil produced• Plastic bottles can produce up to 70 % oil and 16 % gases from

their initial mass

Products from recycled plastic

• PET:• Storage containers, including food containers, fabrics

• HDPE• Tables, roadside curbs, benches, truck cargo liners, trash

receptacles• PS• Metal casting operations, concrete

• Others• Bricks, tiles, plastic railroad ties, additives to ashalt

Glass recycling

Main glass types• Container glass• Flat glass• Fibreglass• Domestic glass• Special glass types: fused silica, borosilicate glass, etc.

Glass composition (1):

• Soda-lime-silica glass: 72 % SiO2, 14.2 % Na2O ,2.5 % MgO, 10.0 % CaO, 0.6 % Al2O3; high thermal expansion, low heat resistance (melts at 500-600 C) – windows, containers, glassware, etc.

• Borosilicate glass (incl. Pyrex): 81 % SiO2, 12 % B2O3, 4.5 % Na2O, 2.0 % Al2O3; very low thermal expansion – laboratory ware, optics, household cookware

• Fused/vitreous silica glass: SiO2; low thermal expansion, very hard, resists heat (melts at 1000-1500 C) and weathering – furnace tubes

• Crystal glass: 59 % SiO2, 2.0 % Na2O, 25 % PbO, 12 % K2O, 0.4 % Al2O3, 1.5 % ZnO; high elasticity, poor heat resistance - glassware

Glass composition (2)

• Aluminosilicate glass: 57 % SiO2, 16 % Al2O3, 4.0 % B2O3, 6.0 % BaO, 7.0 % MgO, 10 % CaO – fibreglass, glass-reinforced plastics, halogen bulb glass

• Oxide glass: 90 % Al2O3, 10 % GeO2; extremely clear, used for fibre optics

Glass recycling stages• Sorting• By colour: glass of different colour generally has different

properties• By glass types – borosilicate and other special glass types should

be dealt with separately: these should be disposed of separately• Crushing into cullet• Melting• Production

• Part of glass containers can be reused

Optical glass separator

Glass production• Glass and cullet storage• Melting in furnace (up to 1575 C)• Forming• Cutting molten glass into cylinders a.k.a. gobs (1050-1200 C)• Blow and blow method: glass is blown into ring mould with all the

container details (parisons), and then blown to full container shape

• Press and blow method: parisons are formed by pressing• Done by individual section (IS) machines

• Inner surface dealkalization (high-temperature S- and F-containing gas)

• Annealing (580 C)• Cooling down (20-6000 min)

Foam glass production• Foaming agent is added to the glass• CaSO4

• Coal• CaCO3

• Aluminium slag• Mixing (foaming agent particle size ca. 75-150 µm)• Heating: gas bubbles form and expand (700-900 C)• Annealing• Cutting into details

Implementation of recycled glass• Glassware• Insulation• Ceramic sanitary ware• Brick manufacturing• Artificial turf• Recycled glass worktops• Foam glass filters• Abrasive materials• Construction aggregate for concrete

Laminated plastic recycling

Laminated plastics• Usually a plastic made of superposed layers of paper, wood,

glass, metal or fabric bonded or impregnated with resin and compressed under heat

• Perhaps one of the most challenging material in terms of recycling is PE/Al composite (chip bags, milk/juice containers, etc.)

Recycling process stages• Shredding• Magnetic and Foucaul current separation• Foucault or eddy curent arise when the magnetic current passing

through conducting material changes• This slows down passing metallic objects

• Aluminium-rich fraction (up to 50 %) is thus obtained• Fraction is treated thermally to remove PE• Rotating kiln• Moving bed pyrolysis oven

• Al is remelted and recycled into new foil

Alternative recovery• Shredding• Addition of diluted acid (HCl or H2SO4) or NaOH

2 Al + 6 HCl → 2 AlCl3 + 3 H2 ↑2 Al + NaOH → 2 NaAlO2 + H2 ↑

• PE slurry is separated by filtration• Hydrogen can be used as fuel gas

Biodegradable organic waste recycling (including food waste)

Organic part recycling• Anaerobic fermentation coupled with biogas production• Methane tanks

• Optimal temperature for biogas production is around 37 °C• Composition: methane and carbon dioxide, may have hydrogen

• Composting • Sludge from methane tanks is aerated, dewatered (when necessary), and mixed

with peat (when necessary)• Left for further decomposition• Used as soil for food-unrelated purposes upon rejects removal (if any)

Recycling MSW rejects

Rejects • Contaminated plastic bags• Clening not cost efficient

• Small pieces of glass• May be dangerous for those who sort waste

• The rejects are usually separated from compost after maturation of piles • Drum separator with cutting tools• Organic material is shredded into smaller prices an exits through

openings in drum walls• Rejects are transported further and exit at the end of the drum• Alternative: screen separator

• Can be incinerated or recycled

Separated rejects• Agglomeration• Cutting• Sand addition• Heating up to 140-240 °C• Plastic rejects melt,

forming silica-plast mass that can be molded and pressed into various products

Compost with rejects

SeparatorCompost

Rejects

Agglomerator

Mixing and heating

Sand

Sand screens

MoldHydraulic pressProducts

Silica-plast products from MSW rejects• 20-60 % of sand• Compressive strength 10-23 Mpa• Density of 1.12-1.68 g cm-3

• Low water adsorption

• Bricks• Poor adhesion (plastic)• Higher density• Hard material (bulletproof)

• Interlocks• Yards, floors, pavements, etc.• Cost is 30-50 % of ceramic interlocks

• Maintenance hole covers• Cheaper and not prone to corrosion, as metal covers

Recycling in iron and steel industry

Blast furnace1. Hot blast2. Melting zone3. FeO reduction4. Fe2O3 reduction5. Pre-heating6. Feed7. Exhaust gases8. Ore, coke and

limestone9. Removal of slag10. Molten pig iron11. Waste gases

collectionFe2O3 + 3CO → 2Fe + 3CO2

Pig iron• 2.14-6.97 % C• 0.2-0.8 % Si• 0.08-0.18 % P• 0.01-0.04 % S• Mn, etc.

• Brittle due to high carbon content• Refinig into steel is needed

Basic oxygen furnace• Hot pig iron is poured

into converter• Magnesium for sulphur

removal• Oxygen stream (99 %)• Outcome: low-carbon

steel • 0.3-0.6 % C• 0.05-0.1 % Mn• 0.01-0.03 % Si• 0.01-0.03 % S and P

Slag• Blast furnace: 20-40 % by mass of pig iron produced• Basic oxygen furnace: 5-22 % of steel produced• Generates SO2, on contact with water H2S and H2SO4

• Recycling: iron re-smelting, addition to glassware and ceramics (from Antiquity on), cement production, road filling, insulating materials (slag wool)

• Part of iron in the slag can be reduced and extracted by magnet

Recycling statistics

Waste recovery in EU