Waste Plastics

Waste Plastic

A WORLD WIDE ENVIRONMENTAL HAZARD:- Plastics contribute approximately 10% of discarded wastes / garbage.

Many kinds of plastics exist depending on their precursors and the process used for their polymerization. Depending on their chemical composition, plastics and resins have varying properties related to contaminant absorption and adsorption

Polymer degradation [1] takes much longer as a result of saline environments and the cooling effect of the sea. These factors contribute to the persistence of plastic debris in certain environments. However, recent studies have shown that plastics in the ocean decompose faster than was once thought, due to exposure to sun, rain, and other environmental conditions, resulting in the release of toxic chemicals such as bisphenol A. However, increased volume of plastics in the ocean results in slowing down of decomposition.

The Marine Conservancy has predicted the decomposition rates of several plastic products. It is estimated that a foam plastic cup will take 50 years, a plastic beverage holder will take 400 years, disposable diaper will take 450 years, and fishing line will take 600 years to degrade.

Types of plastics: [2]

There are about 50 different groups of plastics, with hundreds of different varieties. American Society of Plastics Industry developed a marking code to help consumers identify and sort the main types of plastics:

PET-Polyethylene terephthalate-(Fizzy drink bottles and oven-ready mea trays).
HDPE-High-density polyethylene-(Bottles for milk and washing-up liquids.)
PVC-Polyvinyl chloride-(Food trays, cling film, bottles for squash, mineral water and shampoo.)
LDPE--Low density polyethylene-(Carrier bags and bin liners.)
PP--Polypropylene-(Margarine tubs, microwaveable meal trays).
PS--Polystyrene-(Pots, fish trays, boxes and cartons, cups, plastic cutlery, packaging for electronic goods and toys.)
OTHERS--Any other plastics-that do not fall into above categories.( Eg-melamine, used in plastic plates and cups)

Sources of Plastic Wastes Generation: [1]

Waste from Manufacturing Sector- almost fully remelted & recycled
Post-Consumer wastes – Segregated mixed waste plastics (The plastics waste shall be segregated as per the Codes 1-7 mentioned in the BIS guidelines (IS:14534:1938). ) From garbage.

Approximately 10 thousand TPD plastic waste is generated i.e. 9% of the 1.2 Lacs TPD of MSW in the country.

Categories of Plastic wastes:[2]

Thermo plastics-constitute 80% of the plastic wastes generated in the country which include PET, HDPE, LDPE, PVC, PS, PP, etc. Thermo Set Plastics-constitute 20% of the plastic wastes.

Thermo set plastics are non-recyclable and contains alkyd, epoxy, ester, melamine, formaldehyde, phenol formaldehyde, silicon, urea formaldehyde, polyurethane etc.

Sources of plastic wastes: [3] Plastics wastes from Municipal sources that include residential, markets, commercial establishments, hotels and hospitals. Distribution and industry sector like food and chemical industries, packing films, etc. etc. Other sources include automotive wastes, agricultural wastes, industrial wastes construction debris etc.

Environmental Impact: [3]

Manufacturing of plastic products consumes significant quantities of resources. (4% of world’s annual oil production as feed stock + 3% to 4% in manufacturing).
Requires other natural resources like water, land and produces emissions, liquid wastes and solid wastes.
Littered plastics impact aesthetic beauty of the city, choke drains and make important public places filthy.
Risk on human health and environment due using of toxic chemicals in plastic products.
Animals feed on it from the garbage bins, leading to illness and possible death. Because of the non-biodegradable and impervious nature of plastics,
If disposed in the soil, they could arrest the recharging of ground water aquifers. Garbage mixed with plastics interferes in waste processing facilities and may also cause problems in landfill operations. Requires large area for disposal.
Garbage containing plastic, when burnt may cause air pollution by emitting toxic polluting gases. Recycling industries operating in non-conforming areas also pose hygiene problems concerning environment.

Plastic Waste Management in India [3,4]:

Waste Management mainly aims at recycling. Recycling technology has been classified into 4 general categories:

Primary recycling -involves processing of a waste /scrap into a product with characteristics similar to those of original product.
Secondary recycling -involves processing of waste/scrap plastics into materials that have characteristics different from those of original plastics product.
Tertiary recycling -involves the production of basic chemicals and fuels from plastics waste/scrap as part of the municipal waste stream or as a segregated waste.
Quaternary recycling -retrieves the energy content of waste/scrap plastics by burning/incineration. This process is banned and not practiced in India.

While primary and secondary recycling of segregated waste plastics is practiced widely within the country. Residual segregated plastics that cannot be recycled through the primary and secondary recycling process are processed through the tertiary recycling process.

Kavya Pyro Oils Pvt. Ltd., planttechnology falls under the tertiary recyclingand therefore we will concentrate on Tertiary Recycling i.e. Plasma Technology and Thermolysis/Pyrolysisfor production of combustible gases fuel oils and hydrocarbon chemicals.

Tertiary Recycling: Is done using the following processes:

Plastic waste disposal through Plasma Pyrolysis Technology (PPT)
Conversion of Plastic Waste into Liquid Fuel using the process of Thermolysis / Pyrolysis.

Plasma Pyrolysis Technology: (PPT)

Plasma Pyrolysis is a state of the art technology, which integrates the thermochemical properties of plasma with the pyrolysis process. The intense and versatile heat generation capabilities of PPT enable it to dispose of all types of plastic wastes including polymeric, biomedical and hazardous waste in a safe and reliable manner. Plasma Pyrolysis Technology is plasma pyrolysis, firstly the plastics waste is fed into the primary chamber at 8500 o C through a feeder.

The waste material dissociates into carbon monoxide, hydrogen, methane, higher hydrocarbons etc. Induced draft fan drains the pyrolysis gases as well as plastics waste into the secondary chamber, where these gases are combusted in the presence of excess air. The inflammable gases are ignited with high voltage spark. The secondary chamber temperature is maintained at around 10500 o C. The hydrocarbon, carbon monoxide and hydrogen are combusted into safe carbon dioxide and water. The process conditions are maintained so that it eliminates the possibility of formation of toxic dioxins and furans molecules (in case of chlorinated waste). The conversion of organic waste into nontoxic gases (CO2, H2O) is more than 99%. The Plastic waste disposal through Plasma Pyrolysis is a state of the art technology, which integrates the thermo-chemical properties of plasma with the pyrolysis process. Central Pollution Control Board extreme conditions of Plasma kill stable bacteria such as Bacillus stereothermophilus and Bacillus subtilis immediately. Segregation of the waste is not necessary, as very high temperatures ensure treatment of all types of waste without discrimination. The CPCB has initiated the study in association with Facilitation Centre for Industrial Plasma Technologies (FCIPT), Institute of Plasma Research (IPR) The objectives of the study are to conduct performance study of the PPT on 15 kg/hr. prototype demonstration system developed by FCIPT/ IPR for proper disposal of plastics waste and also monitor air quality parameters e.g. suspended particulate matter (SPM), carbon monoxide (CO), hydrocarbons (HC), benzene, dioxins, furans etc. with regards to gaseous emissions. CPCB also proposes to undertake study on safe disposal of plastics waste using higher capacity (approx. 50 kg/hr.) plasma pyrolysis system as in future and may set up prototype plasma pyrolysis plant on demonstration basis (15 kg/hr. waste disposal capacity) at specific locations (hilly and pilgrimage) in consultation with State.

The operating costs of PPT are high and plant capacities low and therefore commercially not viable. For now, only medical wastes which cannot be safely disposed by Thermolysis are preferentially considered / treated using the Plasma Technology.

Thermolysis / Pyrolysis:[4]

Selection/Segregation: The recyclers/ reprocessers have to segregate the waste/scrap which is suitable for recycling/reprocessing through Primary, Secondary and Tertiary processes.

Processing:

After selection and segregation of the pre consumer waste (factory waste) are directly recycled. The post-consumer waste (used plastic waste) is washed, shredded, agglomerated, extruded and granulated for further use by industry.

The portion of scrap that constitutes Tertiary scrap after segregation of primary and secondary scrap is the type of scrap ideally suited for Thermolysis/ Pyrolysis. Which we use.