If you have read all the CCMs documented in this blog, you will know that I have always picked out low-cost and sustainable methods including DIYs. But there are reasons for reviewing this completely machine-driven composting system.
Firstly, the menace of 24-hour or automatic OWCs/composters. People seem to prefer a fully automatic machine to any other system that calls for human intervention. So instead of burning all the waste into charred carbon which pollutes soil, air and water, you could as well go for Ellenvipro Organic Wet Waste Composter which puts out usable compost. That is, if you are ready to absorb the high electricity bills.
Secondly, most of the digesters designed for sustainable composting can take in not more than 50-70 kgs a day. If you have to compost a tonne of kitchen waste, you will need 20 such digesters and a lot more space and labour. To avoid such workload, communities have been cutting corners and falling for those 24-hour disasters. Moreover, this in-vessel composter can be customised according to the quantities to be handled and designed to process up to 1.5 tonnes of waste per day.
The following are the details about a 400-kg in-vessel composter (IVC). The entire setup comes with a shredder, a blender, a heater and an in-vessel made out of a combination of stainless steel, fibre-reinforced plastic, cast iron (to make gear wheel) and high carbon steel (to make shredding blades) for internal rotating parts and MS plates for the in-vessel and outer components. The shredder, which is a hammer mill pulveriser, is powerful. The machine is fitted with an air blower, a heater and a bioenzyme chamber. Total installed horsepower to run the plant with all the pumps and motors is 15 HP, 3 Phase and 440 Volts, 50 Hz. To process 400 kgs a day, it calls for 2.5-3 hours of continuous shredding and 12 hours of operation.
About the shredder: The shredder has four pairs of blades which have a total of 40 individual blades. The blades are double-edged. When the machine is turned on, the centripetal force straightens the blades out and the waste gets shredded. “If one blade gets stuck during shredding, it gets released in the next rotation itself and the material stuck between the blades falls down. Hence there’s no jamming of the shredder. Because of this mechanism, you can shred even coconut shells,” says Mohankrishna V, Director, Ellenvipro Enviro Equipments Pvt Ltd, Bengaluru.
The external surface of the IVC has undergone only anti-corrosive epoxy paint treatment. On the inside, there’s an FRP lining which does not go rusty. However, this FRP inside lining is a new feature added to the recent batch of composters.
The IVC can be customised according to the quantities to be handled and also the space where it has to be installed. The total machine footprint for this plant is 10ft width x 28ft length x 10ft height + 3ft all-round space.
To study this composter, I picked Embassy Tech Square, Kadubeesanahalli, Outer Ring Road, Bengaluru, where the machine was installed in 2013. Initially, Embassy handled the operations themselves but later on, Ellenvipro has been running the plant. Segregated kitchen waste coming from four food courts is being processed here every day. Although the in-vessel is of 800 kgs/day capacity, the current inflow is about 400 kgs/day only.
The quality of segregation was pretty decent with a few plastic pouches here and there. The staff collects the waste in large containers and sprinkles sawdust on the top to avoid flies and then brings it to the composting unit. They let out extra leachate first and then mix about 20 kgs of sawdust with 100 kgs of kitchen waste. One staff member puts the waste bucket by bucket into the shredder and the process starts.
At the mouth of the machine, there’s a fresh air blower. There is a heating unit placed right next to it. When the fresh air passes through the heating unit, it gets heated up. The hot air then passes through a liquid bioenzyme chamber. It sprays semi-vapourised or droplets of bioenzyme on the shredded waste.
The company sources bioenzyme from a soil conditioners manufacturer. It’s a molasses-based effective micro-organisms solution. Five litres of solution is needed every 15 days. Each litre is diluted with four litres of water. They also add 100-150ml of leachate that comes out of the fresh food waste each day.
From the blender, the food waste moves into the conveyor and then to the in-vessel which can hold 10 days’ of food waste inside at various composting stages. The drum keeps the bi-directional rotation going. The first day’s food waste comes out processed on the 11th day and the second day’s comes out on the 12th day, so on and so forth. It’s a continuous throughput system wherein feeding and harvesting happens simultaneously. Hence, from the 11th day onwards, harvesting happens every day.
At any given point, there must be 1/3rd of space left free in the in-vessel to facilitate tumbling. “Tumbling does not happen if there is no free space inside and secondly, if it’s full, then anaerobic conditions kick in,” says Naveen Bhargav B K, Managing Director.
Basically, the process speeds up because of these three parametres combined: Shredding, sprinkling of bioenzymes and then hot air blowing. The hot air blowing is an exothermic action that supplies necessary bioenzymes immediately to the pulverised food waste. The warm conditions help the microbes multiply quickly. “The exothermic action happens only at the beginning during the sprinkling of the bioenzymes. There are no heaters inside. Later on, the heat is generated by the bacterial action alone as the in-vessel keeps on rotating and helps the essential micro-organisms invade the surface area of the pulverised waste and eventually, the entire vessel.
I paid particular attention to this hot air blowing technique for the simple reason that composting is all about bacterial bonfire that builds up on its own when necessary conditions are ensured. However, for a composter of industrial strength, to let this bonfire happen, it takes at least 4-5 days of work for the microbes to dial up the heat. Consequently, the turnaround cycle gets slowed down.
Mohankrishna V, Director, chimes in: “The blowing doesn’t go on continuously. It has got a controller. If it works for two minutes, it stops for 10 minutes and then starts again.”
Naveen says the in-vessel doesn’t have any holes and hence, unless the hot air blowing goes on intermittently, anaerobic bacteria begin to proliferate and odour issues may crop up.
To run this plant where about 400 kgs of kitchen waste is processed every day, about 70 units of power is needed. That’s about Rs 17,000 per month. If the plant were to be run at its full capacity of 800 kgs/day, it would require about 100 units of electricity per day. “The machine runs for 12 hours only because of its start-stop mechanism. If there’s power cut for 2-3 hours, no issues. Once the power supply is restored, the process starts without any hassles. But if there’s no power for a day or two, then it may start generating odour. However, since both ends of the in-vessel are open, it will not be such a big problem,” says Naveen.
Temperatures vary from up to 30-35 deg.C from the 1st to 5th day and then onwards till almost the 8th day, it goes up to 60 degrees which helps kill the pathogens. At the time of harvesting, the temperatures drop back to room temperature or 35-40 degrees, max.
This compost is let to cure in a corner. “The temperature keeps going up and down and also the pH levels stabilise during this period. We let this stay here for a week or so and then the same is used for gardening.”
Processes STP sludge
This machine can process secondary sludge coming out of sewage treatment plants as well. “The manure is highly concentrated and hence, only a small portion of 5-10 percent of dry sludge can be mixed with kitchen waste and processed. Only dry cakes are processed and no liquid sludge. Since it comes out fully processed and stabilised, sludge need not be transported or thrown out.”
Capex and opex
The cost for the 400 kgs/day composter is Rs 12,90,000 + taxes @ 12% GST. The cost covers the transportation in Bengaluru, installation and commissioning.
Operational expenditure includes the cost of sawdust and power outgo of about Rs 17,000/month to process 400 kgs of waste/day in an 800 kgs/day capacity machine.
About the compost
To be sure, I collected the compost from the site and gave it for testing. The vendor also got the sample from the same pile tested in another lab. My main concern was the microbial load which turned out to be rich. The presence of microbes indicates that the compost is alive and usable unlike the sample from a 24-hour composter which showed zero microbes. Naveen says that they have been selling the compost at retail prices to home gardeners and the feedback has been good.
However, when I used this compost for my pots, it didn’t absorb or retain the moisture as my home-made compost does. It’s not spongy, nor is it black. You can see the difference yourself. Perhaps it’s because of the difference is how both are processed and the accelerators used. Since the lab tests didn’t throw up anything untoward, I went ahead and wrote this review.
Ellenvipro Enviro Equipments Pvt Ltd, #88, 37th ‘B’ Cross, 26th Main Road, Jayanagar 9th Block, Bangalore–560069. Ph: 91 9900108214. Website: http://www.ellennvee.com