It produces LPG, yields organic manure, gets rid of garbage. What more can you ask for? Hema Vijay describes the bio-digester
The Radhakrishnan household in South Chennai hasn’t booked an LPG cylinder in the last few months; they make their cooking gas right at home.
Neither do they buy manure for the huge vegetable garden on their terrace. Imagine a lifetime’s supply of free cooking gas and organic manure, and the satisfaction of not only reducing your carbon footprint but also not adding to the piles of garbage on the streets.
Sounds too good to be true? Not really, if you adopt a new contraption called the bio-digester. Several commercial establishments have adopted the gadget but also, interestingly, families like the Radhakrishnans as well.
Meanwhile, someone like Sai Jayapalan, who runs a marriage hall for the Red Hills Paddy and Rice Merchants’ Association, has found a profitable way to get rid of 250-odd kilos of organic garbage that his hall generates each day.
It seems like a win-win solution all around. As R. Kannan, MD, Infratech Infrastructure Services, a firm that creates waste-management infrastructure, says: “If there is access to sufficient organic garbage, the bio-digester is a very viable option.”
How it works
So, what exactly is a bio-digester? A cylindrical fibreglass structure that works like a composter, it is 1.65m tall, 1.45m in diameter, and weighs about 60 kilos. Immediately after installation, about 25 kg of cow-dung is fed into the composter, as starter fuel, and it takes roughly 25 days to produce bacteria. To start using it, all you need do is feed your organic garbage (fallen leaves, kitchen waste, food waste, etc.) into the crusher unit, where it is mixed with a small stream of water.
The mix is then fed into the bio-digester, where the bacteria already present decomposes it to produce cooking gas. This is piped to your kitchen stove.
A 2 cu.m. bio-digester (generates 2 cu.m. cooking gas, equivalent to 1 kg of LPG) can keep a stove burning for five hours, which means about Rs 30-40 worth of LPG produced each day.
Thankfully, the fuel leaves no foul smell. The bio-digester can process 15 kg of organic waste per day, but that’s not a mandatory figure -- you generate bio-gas in proportion to the waste that’s fed in. The bigger windfall, though, is the rich organic manure produced as sludge. You can use it for a thriving flower and vegetable garden. “Manure costs are exorbitant. In fact, an enterprising person can make a profitable living selling the manure,” says S. Radhakrishnan.
Safe and profitable
After installation, the device is virtually maintenance-free and does not require more cow dung.
It must be located in an open area and the pipe fed into the kitchen. It is inherently safe, as the gas formed is of low density and pressure (less than 1.5 kg/sq.cm; a fraction of that exerted by LPG (17 kg/sq.cm). “If the gas is unused or if excess gas is produced, it won’t explode but merely bubble out gently from the bottom,” says A. Parthasarathy, MD, B-Sustain, a company that manufactures domestic bio-digesters. “I have three now,” says Radhakrishnan, “so neighbours and vegetable vendors give me their organic ‘kuppai’, while I give them rich manure and vegetables in return.” If every house, apartment complex, and restaurant were to invest in the bio-digester, it might be the answer to urban challenges of clean energy, garbage disposal and affordable organic vegetables.
The 2 cu.m. bio-digester costs Rs. 30,000. After installation, you can claim a Rs. 6,000-8,000 subsidy from the Ministry of New and Renewable Energy.
This brings down the effective price to Rs. 24,000. A team at Bangalore University’s Department of Environmental Sciences led by Dr. Rinku Verma is working on a bio-digester design that will cost less than Rs. 15,000 and generate enough gas to cook breakfast, lunch and dinner for a family of five.
Contacts: A. Parthasarathy (9176650001); Dr. Rinku Verma (9880101975); S. Radhakrishnan (9841023448) and Sai Jayapalan (9841019582)