Author – Sumedh Mool
Plastic material is easy to use and we can find it in more than 70% of things that we commonly use. However, plastic is also considered a hazardous waste that is accumulating in our surroundings. Plastic polymers are non-biodegradable, toxin carriers and are danger to animals if consumed. According to the Central Pollution Control Board (CPCB), India generates 5.6 million tons of plastic waste annually and only 60% of this is recycled currently. While there are ecofriendly substitutes for some plastics, they are not as versatile or durable as plastics. So we have no option other than continuing the use of plastic, but reduce its usage in our daily life. However, we can increase the reuse and recycling of plastic waste generated. Fortunately, some innovators in India have come up with interesting ideas to convert plastic waste to petroleum!
After a decade-long research, a team of 6 scientists of Dehradun-based Indian Institute of Petroleum (IIP) has achieved a breakthrough in developing a combination of catalysts that can convert plastic into either liquid fuel or aromatics. The distinctive feature of the IIP process is that the raw material or the feed always remains the same, but with the change in composition of catalysts and process conditions, different products can be derived. Furthermore, the process does not leave any toxic residue. According to the lead scientist Dr.Madhukar Onkarnath Garg, the IIP technology can obtain almost 100% feed-to-product conversion. The residue depends on the quality or type of plastic used in the feed, which can be as low as 0.5% in the case of clean raw material.
The IIP process involves pyrolysis of waste plastics, where plastic’s organic molecules are broken down due to high temperatures and catalytic conversion, followed by condensation to liquefy to get liquid petroleum or aromatics. Polyolefins like polyethylene and polypropylene, which is the main raw material for producing petrol and other products, accounts for 65% to 70% of the typical plastic waste fed into the process. From one kg raw polyolefinic plastic, 650-700ml petrol or 850ml diesel or 450-500ml aromatics along with LPG as a byproduct could be produced. Petrol produced through the IIP process costs INR30-40 per liter, inclusive of the plant cost, operations and manpower. This project was sponsored by Gas Authority of India Ltd, which is now exploring the options to commercialize this process.
Rourkela LDPE-to-fuel process
Low Density Polyethylene (LDPE) is a thermoplastic consisting of monomer ethylene, which is widely used for producing food containers, bottles, tubing, plastic bags, and various molded laboratory equipment. Its most common use is in polythene bags. Raghubansh Kumar Singh a chemical engineer from the National Institute of Technology, Rourkela and Achyut Kumar Panda a Chemist in Centurion University of Technology & Management, Odisha, have jointly developed a commercially viable technology for efficiently rendering LDPE into a liquid fuel. In their approach, the team heat up the plastic waste to between 400 and 500 degrees Celsius over a Kaolin catalyst (soft china clay). This causes the LDPE’s long chain polymer chains to break apart in a process known as “thermo-catalytic degradation”.
This process produces large quantities of much smaller, organic molecules. Kaolin acts as a catalyst by providing a large reactive surface on which the polymer molecules are exposed to high temperatures inside the thermal reactor, breaking them apart. The rate of reaction can be altered by changing the amount of Kaolin used. The reaction at an optimized temperature of 450 degrees Celsius with optimal amount of Kaolin can produce around 70-80% of liquid fuel. So for every kilogram of waste plastic, they could produce 700 grams of liquid fuel that is chemically similar to conventional petrochemical fuels.
This process was invented by Professor Alka Zadgaonkar as part of her D.Sc project in G.H. Rasioni College of Engineering, Nagpur, Maharashtra. Zadgaonkar’s process is named as ‘Random De-polymerization’, which is quite is simple and has already been optimized of large scale production. In this process, plastic waste is placed in a specially designed reactor in the absence of oxygen, but in the presence of coal and certain catalyst invented by Alka Zadgaonkar. The resulting products include crude petroleum liquids, coke and LPG gases. More processing can lead to refined petrol.
Both plastics and petroleum products are hydrocarbons, but in plastics, the chain of organic molecules is longer. So in principle, the Zadgaonkar Process is nothing but reverse polymerization or breaking of longer chains into smaller chains that of fuel. Almost all types of plastic products like Polyvinyl Chloride, PET bottles, LDPE, etc. can be converted into fuel by this process. The fuel thus obtained is tested and has fared pretty well as compared to gasoline obtained from crude oil. The Zadgaonkar couple run a 5 metric ton plant in Nagpur and their fuel is used for running captive power generators in industrial units in and around Nagpur.