Open Forum

New Delhi, 22 July 2009

Plastic Bags & Waste

APT RECYCLING MAY SOLVE CRISIS

By Dhurjati Mukherjee

The use of plastics, which are petroleum derivatives and non bio-degradable, is very common nowadays, specially in the form of polythene bags, both in urban and rural India. Early this month, the Minster of State of Environment & Forests, Jairam Ramesh, appeared to have got the green activists upset, when he told the Lok Sabha that there is a general belief in the country that plastic bags have been banned, which is not a solution. The entire world uses them and they came as an alternative to paper bags, which he added could be more hazardous to the environment as it would imply cutting more trees.  

Instead, the Minister assured that the Government would pursue a policy of encouraging bio-degradable plastic, which though an expensive proposition, is in a promising stage. Indeed, plastic waste is a significant portion of the total municipal solid waste (MSW) and estimates reveal that 10,000 tonnes per day of such waste is generated i.e. 9 per cent of 1.20 lakh tonnes of the total MSW. The plastic waste constitutes two major categories: thermoplastics and thermo set plastics. The former constitute 80 per cent and the latter 20 per cent of the total post-consumer plastic waste generated. Both these types are non-biodegradable and have a long working lifetime.

The environmental hazards due to mismanagement of plastic waste includes: littered plastics spoil the cities’ beauty and choke drains;  garbage containing plastics when burnt cause air pollution by emitting gases; garbage mixed with plastics interferes in waste processing facilities and may cause problems in landfill operations; plastic waste contaminates the soil, thereby impairing agricultural productivity; and recycling industries operating in non-conforming areas are posing unhygienic problems to the environment.

Apart from these, scientists have found that plastic waste interferes with the flow path of sub-surface water, thus responsible for development of local anomalous high ore water pressure, which consequently lowers the strength of the mass. This has caused a failure of the slope and led to landslides. Recent investigation of landslides in Darjeeling and other areas have found that the soil collapses once the plastic waste enters the sub-surface. Besides, plastics that enter water bodies and lakes affect pisciculture.   

Regulation of plastic waste has become a problem though there is the Recycled Plastics Manufacture & Usage Rules, 1999 and subsequently amended in 2003. In recent years, there has been development of standards and guidelines for reuse of plastic waste into construction of roads, pavements, conversion of post consumer plastics into crude oil, in blast furnace/cement kiln, densification of multi-layer and laminated post consumer plastics into card-boards, lumber etc.

It has to be admitted, as the Minister rightly pointed out, that recycling if carried out as per approved procedures and guidelines, may not be an environmental or health hazard though a section of environmentalists do not quite agree questioning its practicality. Various initiatives are being taken for recycling, reuse and disposal of plastic waste. But these technologies are not very popular and most municipalities are grappling with the problem of proper management of plastic waste.

The best option is, of course, recycling in an environmentally sound manner. But it is also a fact that most civic bodies fail to collect and dispose waste. Instead of implementing technological innovations States such as Himachal Pradesh, Jammu & Kashmir, West Bengal other than Delhi have banned the use of plastic bags.

Recycling technologies, however, have been divided into four general types – primary, secondary, tertiary and quaternary. While primary recycling involves processing of waste/scrap into a product with characteristics similar to those of the original product, secondary recycling involves characteristics different from original product. Tertiary recycling helps the production of basic chemicals and fuels from plastic waste/scrap as part of the municipal waste stream or as a segregated waste. The quaternary recycling, which is most complicated, retrieves the energy content of waste/scrap plastic by burning/incineration but this process is not in use.      

In recent times, various organizations (including the Central Pollution Control Board) have experimented in the use of polymer-coated bitumen in road construction and the results are quite satisfying. The mixture is taken out at around 130-140 degree Celsius from the mini hot mix plant and used for road laying. Optimally 10 per cent of bitumen is replaced with plastic wastes. This process is found beneficial in two ways --it saves the fossil fuel and also solves the problem of plastic waste amicably. The process is rather simple and can be used with existing technology and the roads too have been found to be better in marshal value strength, leaching, bleeding, stripping etc.

Besides, experiments of conversion of plastic waste into liquid fuel have also been undertaken. After proper cleaning and drying, the waste plastic is poured into specially designed steel reactor in absence of oxygen and in the presence of coal and certain catalytic additive. It is heated to 300-350⁰ C to convert into liquid vapour, which is then collected in a condensation chamber in the form of liquid fuel while the tarry liquid waste is topped-down from the heating reactor vessel. The organic gas that is generated can be used in dual fuel diesel generator set for generation of electricity.

Importantly, there are other methods of conversion of plastic waste. The post consumer waste of PET jars, bottles etc. can be recycled through a chemical process. These small pieces are washed, dried and shredded into small pieces and fed into the reactor as semi-solid strings in presence of certain chemicals and at desired temperature (around 270⁰ C). The strings are then air-cooled and converted into staple fibres and resins. The former can be used as fibres (rayon) for manufacture of carpets, mattresses and clothing materials.

The other conversion option is to clean, dry, shred the plastic scrap and send the same into mechanical densifier in high pressure. This material is converted into solid plank which is then cut into desired pieces for use in doors, partition walls, furniture etc. However, the downside is that during the process the dust generated may contaminate the ambient environment.   

Though these technologies are available, most of the municipalities are not doing much in managing plastic waste properly. Very few States have started to recycle and/or reuse such waste for productive purposes. Given the situation, it may be imperative the ban on low-quality plastics be enforced strictly enforced all over the country. If not, it could have far-reaching negative effects.

Besides, recycling must be undertaken effectively in accordance with specifications of the Bureau of Indian Standards (BIS). The State Governments should initiate measures to popularize recycling and reuse technologies so that the plastic waste could productively be used. Perhaps, offering subsidy to recycling plants could be an answer.--INFA

 (Copyright, India News and Feature alliance)