Post on 13-Mar-2020
Mentore Vaccari, Francesco Vitali
CeTAmb, UNIVERSITY OF BRESCIA
Waste reuse and recycling
Contents
1. General issues
2. Plastic recycling
3. Metal recycling
4. Paper recycling
5. Organic waste recycling
2
What is waste?
An item is viewed as waste as soon as it has become
worthless to the initial owner.
“One man’s waste is another man’s treasure”
Popular saying
3
Waste hierarchy: 3R rule4
First of 3R - Reduce
Success depends more on human behavior
Technology, policy and other measures take second place
5
Stages in the SWM system
Waste recycling
ReuseWidespread at domestic level Plastic containers, metals, organic matter
Recycling
Usually performed by the informal sector
Inorganic materials (e.g. plastic, metals and paper)
6
Recyclable materials
Paper
Plastic
Aluminium and metals
Organic matter
Other recyclable materials are: iron and steel, tin cans, non-ferrous metals, textiles and glass
7
Stages in the SWM system
Waste recycling
• Informal recycling is widespread
• Informal does not mean unorganized
• Such activities are often in conflict with formal services if they are not coordinated
• Waste-pickers are mostly driven by poverty, are a social fringe group and exposed to high health risk
• Recycling further along the waste cycle worsens working conditions.
• Recycling is a function of market
8
Informal recycling
Characteristics of the informal sector
Small-scale
Labour-intensive
Largely unregulated and registered
Low-technology in manufacturing or provision of services
Often carried out by individuals or family groups
9
Informal recycling
Economic impact of waste pickers
In Bangkok, Jakarta, Karachi and Manila, scavenging saves each city at least US$ 23 million / year in lower imports of raw material, and reduced need for collection, transport and disposal equipment, personnel and facilities. (Medina, 2005)
Informal recycling systems can bring significant economic benefits:
Steady, reliable supply of secondary raw materials
Stimulation of manufacture of low-cost, affordable products from recycled materials
Generates less pollution than obtaining virgin materials
Scavenging reduces the amount of wastes that need to be collected, transported and disposed of (→ cost savings, less air pollution from fewer collection trucks, life extension of landfills)
10
Recycling of plastic waste 11
Plastic Waste Recoveryin Developing Countries
Recycling of plastic waste
Environmental impacts of plastic
Harmful smoke
Blockage of drainage systems
Persistence in the environment (likely for 500 – 1000 years)
Recycling of plastic waste
Why recycle plastic?
Recycling recovers the raw material, which can be used to make new plastic products.
Reasons to start plastic recycling in developing countries:
Imported Raw materials are very expensive!
Labour costs are lower
Trasportation costs are often lower
It is suited to taking on small-scale recycling activities
Recycling of plastic waste
Plastic from raw and recycled materials
Material Price of raw material (€/t)
Price of recycled material (€/t)
LDPE 1300 - 1330 20 - 378
HDPE 1160 - 1200 100 - 650
PET 1250 - 1300 220 - 430
Recycling of plastic waste
Plastic from raw and recycled materials
Energy used to recycle plastic bottles is 8 times less than the energy
required manufacturing the same virgin polymer!
Types of recyclable plastic
Low density polyethylene
- LDPE
High density polyethylene
- HDPE
Polypro-pylene-
PP
Polyvinylchloride- PVC
Polyethylene terephthalate
- PET
Recycling of plastic waste: sorting
Simple tests
Recycling of waste plastic: recycling process
Overview of processes which can take place in a plastic recycling plant: with each step the value of the waste material increses, as the value of plastic as a secondary resource depends on its purity and composition
Recycling of plastic waste: collection
House-to-house collection:
combined with other materials
plastic only, but all types ofpolymers
certain objects only
Collection at a central point
Other ways:
informal collection in return for payment
regular collection from shops, hotels, restaurants,etc.
Recycling of plastic waste: baling
Baling:
After collecting and sorting the plastic material the option exists to sell the material to (other) processing units. Especially when transporting distances are considerable, it is important to compact waste to improve handly and save costs during transport.
Recycling of waste plastic: cleaning
A. Washing
B. Drying
manually
mechanically
manually
mechanically
The plastics can be washed at various stages of reprocessing: before, after, or even during sorting.
Recycling of waste plastic: size reduction
Cutting:
Initial size reduction of large objects
Shredding:
Suitable for smaller pieces
Product of shredding: pile of coarseirregularly shaped plastic flakes whichcan then be further processed
Agglomeration:
Cutting, preheating and drying of softplastic waste
Recycling of waste plastic: pelletizing
Plastic flakes
Plastic spaghetti
Pellets
Recycling of waste plastic: pelletizing
Plastic flakes
Plastic spaghetti
Pellets
A pelletizer in Hargeisa
Recycling of waste plastic: pelletizing
Pellets
Recycling of waste plastic: further processing
Extrusion moulding
Soft PVC tube
Production of pipes, tubes
Recycling of waste plastic: further processing
Injection moulding
Production of miscellaneous itemsShoe soles
Recycling of waste plastic: further processing
Blow moulding
Production of bottles
Recycling of waste plastic: further processing
Recycling of waste plastic: recycling process
Recycling of waste plastic: recycling process
Price of plastic at different steps of the process (€/kg)
HDPE
0.35 after collection
0.54 after baling
0.8 after pelleizing
LDPE
0.2 after collection
0.24 after baling
0.45 after shredding
0.82 after pelletizing
Recycling of waste plastic: recycling process
Price of plastic at different steps of the process (€/kg)
PET
0.3 after collection
0.32 after baling
0.52 after shredding
0.89 after pelletizing
Separation bycolour:
Clear and light bluePET is far morevaluable thancoloured PET
Recycling of plastic waste: examples from Senegal, Mauritania and Burkina Faso
Recycling of metal waste 34
Metal Waste Recoveryin Developing Countries
Recycling of aluminium and iron
Konyo Konyo Market (Juba, Sudan)
AIRCHARCOAL
BYCYCLE WHEEL
35
Recycling of paper waste 37
Paper Waste Recoveryin Developing Countries
Types of waste that can be recovered
Recycling of waste paper
Main grade Examples Value
Printing and writing Computer printout, computer cards, printers trimmings, school and letter papers, “pams”
medium
Kraft sacks Resale as sacks high
Corrugated cardboards Waste paper low
Cartons Waste paper – Sale as cartons medium
Newspaper Printed - Unprinted medium
Mixed waste paper Dirty - Clean low
Source: Vogler, 1981
38
The cheapest way is by putting it into a sack, but this does not hold enough to be profitable.
The next step is a hand-cart, small enough for one person, or a bigger one for a large enterprise.
Recycling of waste paper
Ways of collecting waste paper
39
Manufacture of egg and fruit boxes from old cartons
Manufacture of paper bags and funnels
Waste paper as a fuel (also after briquetting)
Recycling of waste paper
Direct re-use of waste paper
40
Recycling of waste paper
Baling process and presses
Baling means squashing the paper in square-shape bundle and tying it up with wires or strings.
Makes the transport cheaper
Makes the storage cheaper
Adds value to the product
Advantages of baling
No long transportation
No need for storage
No need to lift the bale
Not desirable when
41
Recycling of waste paper
Small-scale paper making plant
Machine Action
Raw material Waste paper or agricultural waste
Digester Cooking with caustic soda or lime
Hollander beater Breaking down to basic fibres, washing and bleaching
Cylinder mould machine Making the pulp (water is sucked out through a drain)
Cutting roll Peel of the pulp in sheets
Hydraulic press Squeezed between smooth rollers
An Indian example
42
Recycling of waste paper
Small-scale paper making plant
Hollander beater
Cylinder mould machine
Hydraulic press
43
Organic Waste Recoveryin Developing Countries
44
Recycling of organic waste
Problems related to dumping of organic waste
Leachate (pollution of soil, surface- and groundwater)
Attraction of animals
Uncontrolled methane production
Shortening of landfill lifespan
46
Organic Recycling Activities
Recycling of organic waste: composting
What is composting?
Composting is an aerobic process that converts waste into a humus-likematerial through microbial action on the organic portion of the solid waste.If carried out effectively, the final product is stable, odour-free, does notattract flies and can act as a soil fertilizer.
Recycling of organic waste: composting
Processes during composting
Recycling of organic waste: composting
Main advantages of composting
Minimize waste amounts in
dump sites and landfills
Reduce waste management costs
(e.g. transportation, disposal)
Improve nutrient and humus
content and soil condition of
agricultural land
Reduce environmental impact of
waste
Comply with national legislation
and policy
Low-cost composting techniques
available
Creates employment
Recycling of organic waste: composting
Some methods of composting
Windrow composting
windrow with a triangular cross-sectionmanual or mechanical turning
Barrel (or box) composting
concrete or steel barrel one or a group of families
Biodegradable waste is biologically decomposed by microorganisms under aerobic conditions and generation of heat in about 6-8 weeks
Recycling of organic waste: composting
Some methods of composting
Vermicomposting
is a process where pre-composted wasteis fed to earthworms, which digest thematerial. The worms can digest halftheir weight in waste per day.
Recycling of organic waste: composting
Types of composting schemes
Backyard Composting
Community-Based Neighborhood Composting
Composting on Institution or Company Premises
Medium Scale Composting Enterprises
Centralised Waste Treatment Facilities
Recycling of organic waste: composting
Lessons learnt
Support by population
Profit
Support by local authority
Reasons for success
Neighborhood resistance
Financial losses
Local authority resistance
Reasons for potential failure
Social factors Financial factors
Institutional factors