Don't junk it

Waste can power vehicles

By Nidhi Jamwal
Published: Thursday 31 July 2003

a recent development can revolutionise the concept of waste management. Alka Umesh Zadgaonkar, head of the department of applied chemistry at the Nagpur-based G H Raisoni College of Engineering, has demonstrated how plastic waste can be converted to diesel, gasoline and lubricant oil. V A Juvekar of the department of chemical engineering, Indian Institute of Technology, Mumbai, agrees that it is possible to make gasoline from plastic because it has the same hydrocarbon chain of molecules as petrol.

Zadgaonkar claims the fuels' quality is at par with those obtained from crude oil. "Unlike plastic incineration, the process does not generate dioxins, as it is carried out in the absence of oxygen and under controlled conditions," he adds. It is even profitable (see table below: Low input, high output).

The two-stage process involves depolymerisation of plastic waste under controlled reactions. A mixture of plastic waste can be used. For instance, one kilogramme of waste can consist of 500 grammes (gm) of plastic bag, 200 gm of plastic sandals, 200 gm of discarded raincoats and 100 gm of computer scrap. During the first stage, the mixture is processed along with coal and patented additives, and then heated at a temperature of about 350c in the absence of oxygen. Thereafter, about 1,100 millilitres of liquid distillate is formed, which accounts for 80 per cent of the waste by weight. The rest of the junk is converted into gases (15 per cent) and coke (five per cent). Faridabad-based Indian Oil Corporation has certified the gas to be in the range of liquefied petroleum gas .

In the second stage, the distillate undergoes fractional distillation, which requires a maximum temperature of 360c. Between room temperature and 200c, petrol is formed. From 240-360c, diesel is produced. Above 360c, lubricant oil is generated. The fuel ratio is: 60 per cent gasoline, 30 per cent diesel and 8-10 per cent lubricant oil.

The rewards of efficient waste management are endless
Inputs Total expenditure
of inputs
(in Rs)
Outputs Quantity
(in litre)
Rate per litre
(in Rs)
Total income
(in Rs)
Plastic waste (I kg of plastic costing Rs 2) 2 Petrol (gasoline) 0.6 37.50 22.50
Labour 5 Diesel 0.3 25.50 7.65
Service charges 2.50 Lubricant oil 0.1 15.00 1.50
Total 9.50 1 31.65
Source: Alka Umesh Zadgaonkar 2003, Conversion of Waste Plastic into Fuels, G H Raisoni College of Engineering, Nagpur, mimeo

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