Simple brick tank composting

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No underground pits, no fancy or complex organic digesters or converters. Sierra Towers uses a strip of simple brick tanks built along the wall at the far corner of the apartment compound for composting. Located in Lokhandwala, Kandivali East, Mumbai, Sierra Towers, houses about 220 families, and these compost tanks have been adequate to hold the wet waste of all the households.

Compost tanks at Sierra Towers, Jan 2016

Wet waste in the compost tanks

Compost taken out of the tank, to be sieved

Cities like Mumbai often find themselves in crisis situations when it comes to garbage disposal. With the closure of the Gorai dumping site in 2007, the BMC found itself struggling to find places to unload the city’s mixed unsegregated/ unsegregatable garbage (and in the process not adhering to the Municipal Solid Wastes (Management & Handling) Rules of 2000 that had made segregation of waste at source mandatory). Housing societies like Sierra Towers often found themselves left to manage their garbage bags for days together, and with it, the stink, flies and associated health hazards.
Around about the summer of 2014, a group of about 10 residents (all ladies) of Sierra Towers got together with the objective of breaking away from their dependence on the BMC for waste disposal. They were aiming to manage their entire garbage within the society premises itself, i.e. become zero waste. The Sierra Workforce, as they called themselves, did a lot of reading, visited a few places in the neighbourhood where composting was being done, including the Samata Nagar Police Station that the Khatri couple had transformed. They also had several interactions with BMC solid waste management officials and waste management service agencies and checked out popular composting infrastructure like Organic Waste Converters (OWCs). Finally, with the help of the Khatris, they decided on the brick compost tanks. Cost was a major consideration, and this method had low cost in its favour.
The team knew that composting was some time away. Much had to be done at the household level before they would be ready. So about three months were spent in training the housekeeping staff and then educating the residents and their helpers (maids, drivers, etc.) on the whats, hows and whys of the waste they were generating. The team spent several hours every week going house to house, explaining segregation at source, which waste was dry and which wet, and how they needed to hand them over to the door-to-door garbage collector. Relevant posters were displayed at strategic locations in the society, and can still be seen. Wet waste goes into one bin, and the dry waste goes into a different bin/bag. Bio-waste, wrapped separately, also goes into the wet waste bin.

A poster that was initially used

Finally in December 2014, the compost tanks were ready for use, and “inaugurated” in the presence of the local BMC officials, corporator and others who had helped. Made of bricks and cement, with gaps for aeration, the bottom was lined with sugarcane leftovers, cow dung, green leaves, and sugarcane leftovers. A mesh covers the tank to keep off rodents and other pests. A roof was subsequently added. In hindsight, the single tree seen in the picture should have been kept out of the tank; it could not survive the heat of the composting process.
Preparing the tanks
Inauguration

The waste collection-disposal process
– Households put the wet waste into a garbage bag and then put this bag into the wet waste bin. Bio-waste, wrapped separately, also goes into the wet waste bin. The dry waste is put into a different bin or bag.
– Housekeeping staff empty the contents of the two bins into a wet waste drum and a dry waste bag. This is done everyday.
– The dry waste is kept separately for the BMC contractor and given away free.
– Bio-waste and other waste that should not go into the compost tank are put into a bin for the BMC contractor to take away.
– The wet waste is taken to the composting area at the back of the society. The housekeeping staff members, open the garbage bags and visually scan the contents. They empty the wet waste into the compost tanks. If there are big bits, these are cut immediately. The waste is stirred based on visual judgement. Cowdung slurry is sprinkled on and off. It takes about two months for the waste to become usable compost. The compost is used for the plants in the society with or without sieving, and also given to residents if they want. Now the society is thinking of selling the excess compost.

Adding wet waste to the compost tank

Composting in progress

Compost is ready

Problems and tackling them
– Some residents were reluctant to do segregation of waste, something that the BMC was not asking them to do. Soon BMC served notices to the societies in the area telling them it was mandatory to segregate waste. Further, the BMC had promised reduction in property tax to societies that managed their waste properly, so this is one incentive that was (and still is) always cited. Currently however, no reduction in property tax has been received.
– Currently about 90 percent of the households do “good” segregation of waste. This level of segregation has been reached with a lot of perseverance. Neighbours were asked to keep a watch on each other. Volunteers from the Sierra Workforce used to accompany the housekeeping staff to households that do not segregate/ segregate improperly to explain what is to be done, why, etc. With tenant movement and some indifferent owners, at any point there are households that do not do segregation properly, so house visits are still done as and when the need arises.
– It took a few months to stabilise the compost piles. It is natural that wet waste that is collected from households will start smelling after some hours. Once it is put into the compost tank and stirred or covered with a layer of already made compost, the smell would go away.
– Bagging of the wet waste in garbage bags generates a few thousands of plastic waste every month, which the team is looking to eliminate. This would be one big step in further reducing the quantum of waste.
The Sierra Workforce team  realises that the current process can be refined and made more efficient. Given their determination, the target of becoming zero waste could well be achieved in the coming year. Other societies in Mumbai could consider emultating this one, not so much for the sake of the law as for the sake of the future of the next generations. India is drowning in garbage and we just have to save ourselves.
For more information or to visit the Sierra Towers compost site, please contact Trupti Rajparia <trajparia@hotmail.com>.