It has been a few years, more than five actually, since we tried composting on the terrace at Brigade Millennium Mayflower Block. Though this very successful pilot experiment has been written about here, I realised that the process has not been properly documented, so here goes!
The objective was to reduce the waste that went out of the 250-flat apartment block. The solution for wet waste was quite obvious, on-site composting.
Those of us from the apartment block who got involved with the project did quite a bit of research to arrive at a sensible, scalable model keeping in mind the existing infrastructure and constraints in the block. We visited a few working sites, read about various methods and engaged with waste management experts and service providers. With the help and guidance of Mr C. Srinivasan, a member of the Supreme Court of India’s Committee on Solid Waste Management, we decided on a method that overcame the lack of space on the ground. The terrace on the 15th floor was identified as a suitable location. Apart from a trolley that was specifically designed for the purpose, the method uses only natural resources – air, water, sunshine, manpower and bacteria present in cowdung/curd.
4 ft x 3 ft x 3 ft. Fabricated with metal flats. Fitted with wheels for portability. Cost in 2010 – approx Rs 4,500.
Preparing the trolley
The trolley was lined with discarded coir matting – on the four sides and the bottom. Coconut husk (about 4-6 inches) was placed on the coir mat at the base and this was covered with coir mat.
Preparing the waste and filling the composter
10th Jan 2010. For the experiment, we needed about 500 kg of wet waste. While a few volunteer households were contributing their waste for this, the quantities were just not enough, so we started collecting discards from nearby vegetable shops and vendors. Cowdung (a 16-litre bucketful), to treat the waste, was sourced from a nearby cowshed.
Apart from apartment residents, we were fortunate to have Mr Srinivasan and other friends present. The small army of volunteers (manpower!) choped the waste into small pieces. To make it easier, these days a shredder could be used. A weighing scale ensured that we knew exactly how much was going into the composting process. The waste was dipped into a bucket of cowdung slurry and left on a jute sack (serving as a mat) to drain excess water. Then it was put into the composting trolley. The alternative to dipping the waste in slurry is to sprinkle the slurry water on the waste after it is put into the composter.
The waste we had collected filled about half the trolley, so over the next couple of days, we continued the process to fill the trolley.
12th Jan 2010. Our trolley was about full with more than 500 kg of kitchen waste. We left it covered with a jute cloth for composting.
Monitoring the compost trolley
From 12th Jan 2010 onwards, no waste was added to the compost trolley. The trolley was kept in a sheltered area, away from direct sunlight and rain. We checked it on a daily basis, looking out for dryness. If we felt the sides or top had gotten dry, we sprayed water. The cross winds on the terrace ensured that there was almost no smell. A sack placed under the trolley absorbed the leachate. We did not mix the waste, except once after about two weeks, to neutralise the stickiness in some parts. By the 40th day, 20th Feb 2010, the level of the waste in the trolley had fallen to about half.
In another 20 days, the compost was harvested. This was after about 60 days since filling to the top.
Points to note
* In a real situation, the waste would not be added in one go, as most of the experiment’s was. An apartment such as Mayflower Block, with about 220 flats occupied, and at an estimate of 1/2 kg waste per flat, would generate about 100 kg of wet waste per day. At the time of this experiment, we had found a cow shed willing to take the fresh vegetable waste, so this estimated quantity would have been significantly reduced. Even without this, our composter would take the equivalent of about 7 days of the apartment’s waste.
* The first lot of compost was done in about 60 days, but the ones that followed would be quicker. We estimated that the first composter could be reused in 6 weeks. So a system of 6 composters would be adequate for the apartment block.
* Operating costs, apart from manpower were almost nil.
Mayflower Block did not proceed with this model, despite the success of the experiment, due to resistance from residents. However, over the past year, the neighbouring Cassia Block adopted a modified version of this method that is successfully working, and can be read about here. This has proved that composting on the terrace is truly a sustainable model, and ideal when space on the ground is a constraint.
While the models described are mobile, it must be noted that the terrace is a good place to do composting even if the composters are fixed (such as made with bricks, concrete, etc.).
Pictures: Mayank/ Karthik/ Arathi/ Vidya