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THE ECONOMIC TIMES POLYMERS • DECEMBER, 2010 - JANUARY, 2011 5

Plastics as commonly understood are either thermoplastic polymers or thermosetting polymers. Thermoplastic

polymers soften on increase in temperature and therefore become maleable and can be re-melted, moulded or extruded without their properties being modified too much. Thermosetting polymers on the other hand remain hard when heated and cannot be re-melted and therefore cannot be recycled mechanically. Thermoplastic polymers are by far the most widely used polymers and there are 100 types with approximately 15 of them being used for common applications. Out of these 5 thermoplastic polymers have over 75% of share of all polymers in the global market which is at a current consumption level of 250 million tonnes per year. The polymers are Polyethylene,

The mechanisation of systems right

from sorting to extrusion of pellets

not only adds to profitability,

but also covers environmental

problem at various stages of

collection, sorting, washing, drying,

grinding etc. as majority of the

waste can carry diseases through

micro-organisms as well as other

contaminated materials found in

municipal wastes.

Vijay BoolaniPresident,Boolanigroup, Mumbai

COVER STORY

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6 THE ECONOMIC TIMES POLYMERS • DECEMBER, 2010 - JANUARY, 2011

Mixed BM waste.

Thermosetting polymers on the other hand remain hard when heated and cannot bere-melted and therefore cannot be recycled mechanically.

Polypropylene, Polystyrene, Polyvinyl chloride and PET. Besides this, there are engineering plastics such as ABS, PC, Polyamides, PUR etc. which constitute approximately 15% of the total consumption of polymers and have not been considered at this point as they are used for high end life applications like automotive, electronics, hardware and appliance as well as white goods industry. The use of plastics in India, over the

past 6 decades, has increased gradually and more rapidly in the last decade to a current consumption of 8.5 million tonnes per annum, with a compounded annual growth of 15%. As a thumb rule, generally the generation of plastics waste is divided into 4 broad categories:

l Industrial Waste: It is generally generated by plastic processing companies during process of extrusion, injection and blow moulding vide purges, runners, lumps and parts with defects.

l Commercial Waste: It is mainly generated in shops and workshops. Being a post consumer waste from establishments like hotels, restaurants, petrol stations, airports, community halls, railway platforms, schools and colleges, clubs and playgrounds, tourist spots, hospitals, pharmacies, garages, hair dressers etc. It is a slightly fouled mixed waste. Besides this, there is certain amount of waste generated during events such as local festivals, side walk sales and events where the fouled plastics waste are well-identified.

l Agricultural Waste: This consists of irrigation pipes, stakes, tarpaulins (for constructions), jerry cans, woven sacks, plastic films (for packaging) etc. used in farming and forestry activities generated from post agricultural operations.

l Municipal Waste: This is mostly generated from households and deposit is directly linked to consumption and various habit patterns of the target population which is related to their purchasing power. Plastic contents may range from 0.5 kg to 1 kg per day in terms of plastic based on data that the plastic content in the municipal solid waste represent between 3 - 8% by weight.

Municipal wastes are usually heterogeneous, dispersed and heavily fouled and consists primarily of packaging films, thermoform packaging, bags, bottles, milk pouches etc. The supply is regular and one can recover plastic municipal waste from:

l Consumer (less fouled).

l Roads and from public places (very fouled).

l Waste collection centres (very fouled) which are normally micro or small businesses who carry out brief sorting of said wastes.

l Municipal dumping grounds (very fouled).

The challenges are waste management or collection depending on geographical dispersion, the contamination level and hetrogenity of such wastes. The industrial, commercial and agricultural wastes are easy to manage having the following advantages:

l Wastes are already identified.

l Regulated supply.

l Clean and unmixed waste.

l Identified collection locations / sites.

l Easy sorting.

Challenges to Collection of Municipal WasteAs regards plastic in municipal waste sourced from landfills, what is needed is:

l A process / method for reducing degree of fouling which, at times can reach upto 25%. This means that for every 100 kg of recovered plastic, there is 25 kg of filth and only 75 kg can be sorted.

l Sorting and segregating of wastes of different types of polymers i.e. PP, PE, PVC, PET, PS etc.

l Reduce transportation cost to landfill area and waste material back to recycling unit.

l An atmosphere for operations at landfill sites to minimise adverse health conditions due to unhygienic environment.

Currently, the scenario for collection of municipal waste is that it is mainly unsegregated with organic and inorganic waste. There is a need to have a structured collection system and this could be organised by selecting a few neighbourhoods in the area of commercial waste by motivating people to separate plastic and another wastes. Once this is achieved, the next challenge would be to determine the characteristics of segregated plastics waste around the 5 major categories – PP, PE, PS, PVC and PET and this could be done

PET recycle plant.Landfill collection.

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THE ECONOMIC TIMES POLYMERS • DECEMBER, 2010 - JANUARY, 2011 7

at the level of the waste collection centre.

As no ideal collection system exists, each zone or area needs to be studied to respond to the quantum of such waste being generated. Further, such an apparatus or equipment should be available which downsizes the plastics waste, which in case of packaging material are normally voluminous though light in weight and tend to occupy larger area in their original form.

Recycling of Plastics WasteThe recycling of plastics waste offers a huge business opportunity with economic benefits besides addressing concerns of environment and saving of petrochemical resources and energy. Once the waste is available, sorted out and in compact form, the recycling of such plastics waste can be made very profitable and equipment to extrude and pelletise such waste could be set up by local authority and / or public - private partnerships. Steps include:

l Collection

The trend in India, in a metro city, as an example, has a dual collection system where approximately 5000 collection agents collect plastics waste by door to door collection method. Each collection agent collects an average of 15 kgs of plastics waste per day and based on 25 days a month, collects approximately 375 kgs/month. This source of collection obtains quality plastics waste with minimum fouling and a higher market value. On the other hand, 5 times the number of people sort out plastic at various dumping sites and on an average extract 15% of recoverable material, out of which 5% is waste plastic. On an average, each sorter recovers 10 kgs of plastic per day and works 20 days a month, thereby recovering 200 kgs of most fouled plastics waste to be resold at approximately half the price than those collected at the source. The other factor is that transporting waste plastic is most expensive given their low densities (0.9 to 1.4) and average density in bulk rarely exceeding 400 kg/m3. This may be addressed by setting up a recycling facility possibly near about to such areas and also organising pick-up smartly with a use of cheap transport adapted to local environment e.g. using hand cart, tricycle with pedal, small motor vehicle, pick-up vans depending on the volume as well as distance to transport the same. The physical preparation of plastics waste to convert the same into small, clean and dry pellets or chips of acceptable size through use of extrusion lines and allow

the pellets or chips to be introduced into various extrusion, injection and blow moulding machines for shaping into various end products.

l Washing

Having highlighted the collection and sorting (sorting which includes emptying, decaping and delevelling containers and packages etc.), the next important thing is washing and defouling before pre-cutting / grinding the waste. Washing techniques normally used are by hand in buckets or containers of warm or cold water depending on the level and type of contamination of waste and with the use of industrial detergents to facilitate the task. Washing can also be done after grinding or downsizing the plastics waste. However this practice has to be with a degree of mechanisation as it involves using very hot water and powerful cleansing agents such as sodium or potatium hydroxide. Here the operators are in direct contact with the materials and hence are unable to comply with the safety rules. Dumping ground.

Migrant workers sort the PET bottle waste.

MEGAPLASTIC ASIA

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8 THE ECONOMIC TIMES POLYMERS • DECEMBER, 2010 - JANUARY, 2011

Currently, the scenario for collection of municipal waste is that it is mainly unsegregated with organic and inorganic waste.

streamlined and sources set-up through direct supply of waste plastic material received from the collectors / rag pickers. The mechanisation of systems right from sorting to extrusion of pellets not only adds to profitability, but also covers environmental problem at various stages of collection, sorting, washing, drying, grinding etc. as majority of the waste can carry diseases through micro-organisms as well as other contaminated materials found in municipal wastes.

Further, the plastic materials have various chemicals present and working on them through light, heat or mechanical processing can degrade and decompose the respective monomers as well as many pigments and colouring materials containing heavy metals which form the basis for their pigmentation, could be very toxic to human beings. The general aspects of work safety have to be observed.

ConclusionIn order to retain the growth of use of plastics in wider applications including the packaging sector and without affecting the environmental balance, this industry sector has to be properly organised and effectively be managed by the industry and government getting together to organise user friendly collection systems and putting in joint efforts for prompting technology based recycling industry to achieve the following objectives:l To reduce resource consumption

(petroleum oil) and power required to produce virgin material.

l Maximise resource for reuse and increase the percentage of waste recycling which will benefit Indian economy and maintain price stability of material and thus reduce inflation.

l To realise better value of waste plastic material, it is desired to create waste collection systems of such items which are identifiable and generated in large quantities everyday, which will prevent the material from being dumped into garbage bins and finally to municipal garbage sites.

l The recovery of plastics waste from garbage sites / landfills pose health hazards, is uneconomical, difficult to get quality product for reuse.

l Setup plants for process technology for recycling of post consumer plastic (PP, PE, PVC, PET, PS and other), mixed plastic and plastics waste segregated from end-of-life products such as automotive, electronic and white goods.

l Drying

A crucial step after washing, but prior to recycling is that the material has to be reasonably dried to a lower moisture content, preferably less than 0.1% to make it receiptable to extrusion process. Drying is carried out by various methods such as drying in the sun or ventilated

rooms with artificial ventilation such as use of a fan or hot air drying with heat guns, electrical dryers etc. The drying of flakes is easily mechanised by using a spin dryer which can take up waste plastic flakes between 4 and 10 mm having moisture content of about 5% and after a run of 5 minutes reduce moisture content to 0.5%.

After the above process, the granulated material / flakes are force fed in an extrusion line (using single or twin screw extruder depending on the polymers to be used and extrusion lines from 10 kg/hour to over 1000 kg/hour production can be made available). Plastic material exits through calibrated die with circular holes to obtain strands of desired diameters which are in line immersed in a water tank to cool the strands, before being fed into pelletising unit which cuts the strands into small lengths of 3 to 4 mm. The other system would be to directly cut hot strands with a die face cutter at the die outlet by using air or water cooling arrangement. The pelletised granules are then collected and packed in PP industrial sacks of 25 kg volume or in jumbo bags of 500-1000 kg depending on the customer requirement.

Reuse of Plastics WasteIn the Indian context, recycling of plastics waste is an economically profitable activity. As against the world average of plastics waste recycled at 20%, the Indian plastics waste recycling industry is highest at 60%. The cheap labour cost, specifically in the area of operations of collections, sorting, washing, drying, grinding, extrusion and use thereafter are done mainly with manual labour. However, for the future

growth in this area, it is advisable to go for mechanised operations for all of the above, except collection and with a higher

production to achieve a viable scale as well as quality of end product and thereby to achieve higher profitability. Secondly, the cost of procurement of plastics waste; either unsoiled, slightly soiled or highly soiled should be

Twin screw extruder.

Single screw extruder.