For my case study, the destination was Sovereign Park, Basavanagudi. It’s a 23-year old, 40-unit apartment which does efficient segregation at source. It has outsourced secondary processing of dry waste to Sudh-Labh. They chose the same firm to compost their wet waste sometime in August.
Once at the spot, it took just a little while to understand the simple process and trace the origins of this rather simple design—the firm’s mentor Teejay Jayaraman’s expertise in “frugal innovation”.
A structure that breathes
Put succinctly, Sudh-Labh mimics composting process that happens in the natural environment. Instead of heaping it up in the open, you are simply layering it in a more methodical fashion inside this digester to bring out the compost as quickly as possible.
This method is aerobic. It has a simple above-the-ground rectangular box-like structure with 4.9 ft x 6.5 ftx 5.5 ft (1.5m x 2m x 1.68 m) dimensions with its walls made of FRP sheets. On all the four sides, the walls are riddled with holes to let the air in. The top is left uncovered. Four perforated pipes jut out of the digester—taking the hot air out from the composting mass and letting fresh air in, simultaneously. Two hatches (openings) at the bottom—front and back—have been provided to take out the mature compost. It has a section in the bottom to collect the leachate dripping down from the digester. Interestingly, since August, just one bucket of leachate has come out from the entire organic mass.
The digester needs to be installed under a roof to protect it from rainwater. To make things easy, the company is contemplating a detachable roof as an option to those who prefer keeping it out in the open. A step-up stool, a plastic tub, a rake and a couple of other basic tools are part of the package.
The digester can hold 500 kgs of waste, in all. That means, a 100-strong community will need only one digester to process all its kitchen waste.
Power & water consumption
Sovereign Park was not keen on investing in a shredder as the waste quantity it generates is very less (15-18 kgs per day) and that takes away the pressure to produce compost in an expedited manner by using a shredder. Water consumption is almost nil as the water content in the kitchen waste and EM solution are enough to keep the process going.
This digester takes in both vegetarian and non-vegetarian waste. When starting the first batch, four blocks of cocopeat (which need to be soaked in water and then crumbled) have to be spread evenly at the bottom to absorb leachate. This needs to be done only for the first batch. Spread a layer of kitchen waste and add a layer each of dry leaves and saw dust on top of it to absorb extra moisture. Once in a week, sprinkle neem powder and 250 ml of effective micro-organisms (EM) solution and microbes powder—both manufactured by Daily Dump. All these ingredients are essential to control malodour, insect and flies and to speed up the process.
The next day, before adding the fresh waste, use the rake to turn the mass to aerate it and repeat the process of adding kitchen waste, dry leaves and saw dust.
Daily routine: Kitchen waste + dry leaves + sawdust. The next day, rake up the material and repeat the process.
Once-in-a-week routine: Sprinkle neem water + EM solution + microbes powder.
Gopinath C R of Sovereign Park, who heads the management committee, says: “This is an easy and sustainable process and not power-driven.” When asked if they were planning to buy a shredder, Gopinath added that the digester was quite sufficient for 40 homes. “We are fine if it takes a little longer to bring out the compost. It’s better than investing in a shredder which is no small an amount for a small community like ours.”
Output and quality
The first batch always takes longer—10-12 weeks. Thereafter, the compost can be drawn out through the hatches at the bottom whenever it is done. “The variety of the brown material loaded with carbon (dry leaves, saw dust and cocopeat) and nitrogen-rich kitchen waste brings about a balanced carbon:nitrogen ratio,” says Vasuki Iyengar of Sudh-Labh.
The best feature
In my view, design is the best feature of this product. You don’t have to invest in another digester to let the compost mature in the first one. You just keep taking out the mature compost from the bottom hatch even as you go on adding fresh waste on the top. What more, it handles a large quantity of waste coming out of a maximum of 100 homes and consumes very little space.
If you decide to invest in a shredder, that will shorten the turnaround time and also bring out fine manure. Unshredded waste is slow to break down no matter which method you use and the output will be a little chunky and leafy. Once sieved, you will get a considerable amount of semi-done reject which has to be put back into the digester for further processing.
Let’s calculate both one-time and operational cost (per month) for a 100-home community. The digester costs around Rs 40,000, a one-time investment. That means, Rs 400 per household.
The break-up of the operational expenditure/month:
- Cocopeat blocks: 25 kgs, twice a month: 50 x 6/kg = Rs 300
- Neem powder: 1 kg = Rs 40.
- Sawdust, 2 sacs: Rs 60 x 2 = Rs 120.
- Daily Dump EM solution, 1 litre = Rs 65.
- Daily Dump microbes powder, 2 packets = Rs 45 x 2 = 90.
Total monthly outgo: Rs 615. That means Rs 6.15 per household for a 100-unit community.
That works a treat, doesn’t it?
Thus far, I haven’t come across a method that is this cost-effective.
Sudh-Labh, No. C-3, 906, L & T South City, Bannerghatta Road, Bangalore 560076, Phone: +91 98456 90778. www.sudh-labh.in.