At a time when fuel and power are becoming dearer, Professor S. Rajendran explains how trash can help to generate revenue

S. Rajendran talks biotechnology in his own simple way. But before delving into the subject, he offers me biscuits to eat. What is the connection between the biscuits and biotechnology here? “It’s made of mushrooms cultivated on municipal waste,” he says. Sounds bizarre to the ears but the biscuits taste good.

The Associate Professor of Botany at Saraswathi Narayanan College has successfully cultivated mushroom with the use of organic manure obtained from municipal solid waste. Over the years it has been his attempt to optimally use the waste generated in the city.

“Mushroom is a storehouse of proteins,” he says. “It can be consumed as a fresh vegetable as well as in the powdered form.”

It all started when Rajendran embarked on a project on ‘Feasibility study of technology for smoke-free briquettes’ with agricultural waste. Initially, he focussed on producing quality briquettes for the Department of Science and Technology funded project. But later switched to cultivation of mushroom given the high organic content in agricultural waste.

“The organic substance is separated from the waste and oyster mushroom is cultivated through the solid state fermentation technology,” he explains. It is a process where the organic matter is seeded with mushroom spawns. The substrate is then left in a temperature controlled room for 15 days to get the first yield of mushroom.

Once the results were encouraging, he branched out and applied the same technology to municipal waste. He first demonstrated the study in Paramakudi Municipality.

After the mushroom harvest, the fungal fermented substrate is used to make briquettes. “The calorific value of these briquettes can be upgraded to that of lignite coal. These briquettes are potential power-generating agents as well as efficient fuel,” notes Rajendran. Apart from the briquettes, he has also made tiles out of agricultural substrate, which are efficient acoustic enhancement material.

“Once the degradable waste is segregated, the leftover inert material can also be utilised as rooting media for plant cultivation in terrace gardens.”

On an average the city generates around 450 tonnes of garbage everyday, leave alone the hospital waste. It includes more than 100 tonnes of vegetable market junk. Over 65 per cent of the entire waste is organic matter.

Since the waste generated in Madurai corporation is massive, Rajendran suggests that women self help groups can be involved in production of organically cultivated mushroom. He regularly conducts free training programmes for entrepreneurs interested in mushroom cultivation and he has also developed healthy mushroom spawns. He has submitted a proposal to the city corporation.

There’s generally an aversion towards agricultural produce grown on municipal waste. “It’s a misconceived notion,” says A. Mathuram, City Engineer, Madurai Corporation.

The local body collects garbage from residences and commercial establishments and transports them to the dumping yard in Vellakal near Perungudi where the degradable waste is digested aerobically and composted to manure.

The Corporation has devised the solid waste management programme in accordance with the guidelines of the inter-ministerial task force established by ministries of environment and urban development. “There are no takers for the organic manure generated from municipal waste. Awareness should be created among people to support such initiatives. We are studying the feasibility of using briquettes for power generation,” he says.

People can produce their own organic manure by separating degradable waste from garbage. The manure can be used to grow not only mushrooms but also other vegetables in their home garden. For many, garbage disposal is dumping the junk in a yard. But not many know that it is a potential money spinner for the local body.