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 eco-friendly 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!
Innovations 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 the 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 65-70% of the typical plastic waste material 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 the Gas Authority of India Ltd, which is now exploring the options to commercialize this process. A commercial plant was inaugurated in August 2019 in IIP, which is capable of producing 750-800 liters of diesel from 1,000 kg of plastic. The plant has a capacity of one tonne per day and they are planning to set up 10 such plants.
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 heats up the plastic waste to about 400-500 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.
Rudra Environmental Solutions
Shirish Phadtare and Medha Tadpatrikar, were dismayed by the amount of plastic casually thrown away and decided to find a solution. Plastic is made from crude oil so they thought to reverse the process, researched about it and came up with a technique to convert plastic waste to fuel using the mechanism of thermos catalytic depolymerization. After vigorous research for four years, they founded Rudra Environmental Solutions in 2010 and were the first to set up a plastic-to-fuel conversion plant in Pune, without the aid of any government laboratory.
Vans of Rudra Environmental Solutions collect plastic waste from residential societies in Pune, which is then taken to their plant in Jejuri outside Pune where it is segregated. The segregated plastic is then put into a dust cleaning machine and after cleaning for dirt, the plastic is shredded. The shredded plastic is fed in a reactor along with a catalyst and is heated to 270-280 degree celsius. The heating energy for the machine comes from gases like methane and propane that are emitted during the heating of these plastics which is reused. The oil obtained this way is then filtered, stored and sent for dispatch. The residue obtained from this process is also used in road asphalting, so the entire process is eco-friendly. Rudra Environmental Solutions process about 10-12 tonnes of plastic in a month and generates 55-70 liters of oil from 100 kgs of plastic.
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.
The Zadgaonkar process is no longer active.