Shredded waste is continually fed into a conventional extruder. Here over the length of a heated extruder screw, the waste is plasticised and melted at a relatively low temperature. The melt is then stripped of chlorine as we just saw, and led to a reactor where lies the crux of the invention. The melt interacts with proprietory catalysts invented by Alka. The stable, continual chain of carbon found in all plastics is destabilised by a depolymerization reaction and rendered ready for a rich harvest.
Three streams of produce are obtained. A part of the gaseous cloud is condensed to form a liquid hydrocarbon. This is the recovered fuel oil. It is a sulphur free equivalent of industrial crude. It can be readily used in furnaces or put through fractional condensation to obtaine finer grades like petrol. For a long while to come, the best market for this is as furnace oil for process heating in factories. Zadgaonkar recovery plants, when they spread in the country, can use plastic from local dumps and serve local industries which currently buy expensive furnace oil from far away.
What is not condensable at the reactor is obtained as a LPG equivalent. A modified genset can generate electricity using this gas. This is now standard practice at a Zadgaonkar plant, which is self sufficient for power. The final remains are a solid fuel called petroleum coke. Approximately 70% is liquid hydrocarbon, 15% is gas and 5% is solid coke. Balance is ash and metal fines.
And now the story:
Alka born in 1962, has always had a fascination for organic chemistry. "I was intrigued by the way new products can be created by playing with carbon and hydrogen molecules," she says. "There was a sense of great control over things." That mind set was to eventually lead her to her invention.
After marriage to Umesh Zadgaonkar, she settled in Nagpur and began teaching chemistry. Umesh is an MBA and a natural entrepreneur- which means he has an ability to grab the opportunity ball and carry it over the line, eluding all tackles. He was the first to bring health clubs and gyms to a sleepy, conservative Nagpur; he realised the idea would appeal to citizens given to living the clean life. In contrast, Alka is a small, self-effacing lady fiercely committed to teaching and housekeeping. Their son Akshay is a computer prodigy.
In 1993, Alka first began to notice plastic piles in their clean and pleasant Nagpur. The menace was already a huge problem in big cities and there was a rising chorus of concern demanding solutions. These ranged from fiats to ban carry bags use [- as though other forms of plastics were innocent], to recycling to making the industry pay. "You can't wish away plastics," says Alka. "They have become a part of our lives."
She began to think of a creative solution. It was still pre-Internet days and she did not have ready to access to the state of the art. She knew her chemistry, though. She began arguing that the source of all plastics is petroleum. The trick is to revert them to their previous life where they become petroleum again. Plastics get their variety and stability from strong continual, patterned bonding of the carbon molecule. If this long chain is disrupted, they would collapse and can be coaxed to their original form. The process of disruption is random depolymerization.