14 Recycling

Dr. J. Rajesh Banu

Objectives:

• The learning objectives of this module are
• To know what is recycling and the material that are recycled. To gain knowledge about the types of recycling
• To explain the steps involved in recycling process
• To describe the proper mode of collecting and sorting the waste To understand the benefits of recycling and recycling symbols

1.    Recycling: Definition

Recycling is the process of collecting and processing waste materials into reusable materials. It is the key constituent of waste reduction in the modern world. A material is recycled if it is used, reused, or reclaimed. Recycling can avoid or minimize the wastage of valuable materials. It will also reduce the utilization of fresh raw materials due to which energy usage is minimized. Moreover, recycling controls or minimizes the environmental pollution eg. air and water pollution (pollutants released during the process of incineration landfilling. The materials that can be recycled include paper (newspaper, cardboard, mixed paper, etc.), glass (amber, green, and/or flint), cans (aluminum, ferrous, bimetal), and plastics (PET, HDPE, PS, PVC, PP, LDPE, etc.), and many more.

2. Types of Recycling

Recycling can be classified into three types. They are primary, secondary and tertiary recycling. Tertiary recycling is further sub classified into internal and external recycling. Figure 1 shows the schematic view of the types of recycling.

2.1. Primary Recycling

The reusing and recovering of the material without any changes in their originality after recycling is said to be primary recycling. It can be defined as the second-hand use – reusing. The purpose of material usage will remain unchanged. Example: Giving donation to a friend, family member or to charity organisation, selling etc.

2.2. Secondary Recycling

This type of recycling involves some sensible alteration of the material or product without the use of chemical processes. Example: Cutting and reshaping of various products to make arts and crafts, Cutting envelopes into smaller pieces to use them as scrap paper etc.

Figure 1 Types of Recycling

2.3. Tertiary Recycling

This type of recycling involves the reprocessing of materials or products by a chemical process or heat. Example: melting metals, chemically treating old paper and crushing plastics bottles to make brand new products.

2.3.1. External Recycling

The Tertiary recycling is said to be external recycling if the materials or products are recovered and reprocessed with public participation i.e., sorting waste and putting it in recycle bins to be collected and transferred to reprocessing facilities.

2.3.2. Internal Recycling

The Tertiary recycling is said to be internal recycling if the materials or products are recovered without public participation i.e., within the factories and manufacturing facilities.

3. Steps involved in Recycling process

Recycling process involves the following steps that assists in the minimization of waste material or products thereby reducing their environmental impacts. The steps involved in the recycling process is shown in Figure 2,

Figure 2: Steps involved during Recycling process

3.1 Collection

The Recyclable materials from municipal solid waste is collected by the following methods.

1. Collection of segregated or source-separated recyclables. They are collected by the waste collectors with and without subsequent processing.
2. The materials for recycling can also be collected from the transfer stations or any other centralized recovery facility.

If the waste is a mixed municipal solid waste then they have to be segregated and collected in different coloured bins. Figure 3 depicts the colour coded bins for segregated collection of waste. Green bins or sacks are for green waste eg. Food and garden waste. Blue colour bins are for recyclables and black is for non-recyclables. Once segregated, the recyclables are delivered to waste collectors for further processing.

3.1.1 Mixed dry recycling

Clear sacks are used for collecting this type of waste, do not mix with the black sack wastes and squash the plastic bottles regularly. The list of mixed dry recycling material that are collected in blue bin are listed below:

i.  Cans including: food tins and drinks cans, empty aerosol cans, tinfoil and foil ready-meal containers (with food removed)

ii. Cardboard, including: cardboard boxes, cardboard food packets, greeting cards, toilet roll and kitchen roll inserts, food and drink cartons (with liquids removed)

iii. Paper, including: newspaper and magazines, catalogues, telephone directories and paperback books, envelopes, junk mails and shredded paper

iv. Glass including: glass drink bottles, glass food jars and bottles

v. Plastic, including: plastic bottles, yoghurt pots, plastic ready meal container, ice cream tub, super market carrier bags.

3.1.2     Non- recyclable waste

Depending on the property, the non-recyclable materials are collected either from the black bin or from the black sacks or large communal wheeled bin. The non-recyclable materials such as disposal nappies, sanitary towels and incontinence pads, polystyrene packing, pet waste or cat litter, broken crockery, cigarette ends and ashtray content, coal and wood ash

3.1.3    Categories of waste collection

There are three categories of recycling material collection centres as shown in Figure 4.

Drop-off centers

Drop-off centers necessitate the waste producer to convey the recyclable material to a central location, either an installed or portable collection station or the recycling plant itself. They are the simplest type of assortment to establish, but suffer from low and unpredictable quantity.

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 on, hopefully creating a profit. Unfortunately, government subsidies are necessary to make buy-back centers a viable enterprise, as according to the U.S. National Waste & Recycling Association, it costs on average US$50 to process a ton of material, which can only be resold for US$30.

Curbside collection

Curbside collection includes many faintly 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. The recyclable material collecting Truck is shown in Figure 5.

3.2 Sorting

Once commingled recyclates are collected and delivered to a central collection 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. In plants, a variety of materials are 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. Sorting can be done by various methods. They are

i.  By hand

ii. By Automated machinery

iii. By strong metals

3.2.1   By hand

The commingled recyclable material is removed from the collection vehicle and placed on a conveyor belt spread out in a single layer. Large pieces of corrugated fibre board and plastic bags are removed by hand at this stage, as they can cause later machinery to jam.

3.2.2   By Automated machinery

Automated machinery such as disk screens and air classifiers separate the recyclable material 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 plastics 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.

3.2.3   By strong metals

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 aluminium 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 based on its colour: brown, amber, green, or clear. It can either be sorted by hand, or via an automated machine that uses coloured 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.

3.3   Rinsing

Food packaging should no longer contain any organic matter (organic matter, if any, needs to be placed in a biodegradable waste bin or be buried in a garden). To avoid organic matter, the packing material needs to be rinsed before placing in a trash bag.

3.4   Processing & Recycling

Although many government programs are concentrated on recycling at home, a 64% of waste is generated from 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. Table 1 shows the Waste processing and recycling methods.

Levels of metals recycling are generally low. As metals are inherently recyclable, the metal stocks in society can serve as huge mines above ground. However, they found that the recycling rates of many metals are very low. 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 it is used by all branches of military use for 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 Poly Vinyl Chloride often results in downcycling of the material, which means only products of lower quality standard can be made with the recycled material.

4. Recycling Symbols

During recycling, it is difficult to know whether a product is recyclable. However, to recognize a product that is recyclable the symbols are often printed on the underside of packaging. The universal recycling symbol is

There are several systems of symbols found on packaging, the most common symbols and their meanings are listed below:

5. Benefits of Recycling

The following are the advantages of recycling process. They are,

• Reduces the quantity of waste convey to landfills and combustion facilities
• Safeguard natural resources such as timber, water, and minerals
• Prevents pollution by dropping the need to collect new raw materials
• Saves energy
• Reduces greenhouse gas emissions that put in to global climate changes
• Helps to uphold the environment for future generations
• Helps create new well-paying jobs in the recycling and manufacturing industries.

6    Summary

In this lecture, we learn about:

• Recycling and its types
• Method of collection, sorting and processing and recycling The energy saved during recycling process
• Various symbols used to identify the recycled products Benefits of recycling process

References:

1. Web-Dictionary.com (2013). “Recyclate”.
2. Freudenrich, C. (2014). “How Plastics Work”. Retrieved 2016-07-07.
3. DEFRA (2013). “Quality Action Plan Proposals to Promote High Quality Recycling of Dry Recyclates”
4. Sheffield, Hazel. Sweden’s recycling is so revolutionary, the country has run out of rubbish (December 2016), The Independent (UK)
5. http://en.wikipedia.org/wiki/Recycling