Green solution to bio-waste

A biogas plant treating Bengaluru’s waste is supplying 600 kg of CNGa day to hotels, says M.A. Siraj

February 28, 2015 12:00 am | Updated 05:37 am IST

28bgp bio 1

28bgp bio 1

A way from the public gaze, South India’s first plant producing CNG (Compressed Natural Gas) from waste from hotels and poultry farms has completed its first year of operations. The plant is supplying 600 kg. of CNG to the Bengaluru’s restaurants every day.

Tucked in Huskur village, 14 km west of Doddaballapur, the plant named Maltose Agri Products Private Ltd. (MAPPL), not merely takes away some amount of city’s waste, but also turns it into energy and averts release of hazardous methane into the atmosphere. Currently operating with three waste digesters, it will have ten of them on completion of its expansion plans.

The innovative plant was envisioned and set up by T. Ananda, an agriculturist, two years ago even while the city was in the throes of agitation at Mandur against landfills. It is currently taking 25 to 30 tonnes of waste. The waste from poultry farms, which abound in the area, is either piped to the plant in the form of slurry or arrives by tractors. The waste from a hundred and odd hotels and restaurants, mainly around Hebbal and R.T. Nagar, is carted to the plant by Bruhat Bengaluru Mahanagara Palike (BBMP) lorries in drums, while the cattle dung is picked by workers from mainly Cantonment area and brought in lorries. Three BBMP lorries bring 10 tonnes of hotel waste a day. Twenty five tonnes of dung is collected by another four lorries and five to seven tonnes of poultry waste also comes in. The poultry farms are paid for the waste at 30 paise a kg.

The process

Upon arrival, the dry waste is first crushed. Non-organic waste such as plastics or silica is removed and sent to a collector tank where slurry is prepared. It is then pumped into large sized digester chambers. Anaerobic digestion takes 21 days for production of methane at the start of the process. Daily feeding of waste ensures continuous generation. The chambers have churners inside that isolate sediments, which are separated mechanically and left to dry in pits for the purpose of manure.

The methane is then brought to balloon rooms where it is stored under large-sized rubber domes. At this stage it has merely 60% methane while the rest of it contains carbon dioxide, hydrogen sulphide gas and vapour. It then undergoes a purification process and carbon dioxide, sulphur dioxide and vapour are removed. At this stage, it is 92% methane which is passed through compressor to be filled at high pressure as Compressed Natural Gas (CNG) into cylinders of 5 kg, 10 kg and 12 kg for supply to the restaurants. The company is however running its supply trucks on the same CNG and has fitted them with 38 kg cylinders.

Currently, the Maltose plant is producing 600 kg of CNG a day and supplies them to six large hotels and restaurants in the city in collaboration with the marketing company Carbon Masters. While the LPG cylinder gas comes at a rate of Rs.60 per kg, Maltose’s CNG is being supplied at Rs.40 a kg.

Ananda, who has studied up to Plus Two and himself maintains a poultry farm with 50,000 birds, says that against the initial investment of Rs.2 crore by him, the Ministry of Renewable Energy extended a sum of Rs.68 lakh by way of assistance. His plea to exempt the product from Sales Tax is under consideration by the State government.

Ananda expects the plant to generate 4,000 to 5,000 kg of CNG by taking 250 tonnes of waste once all the ten digesters begin to operate around the middle of 2016. By then his investment would go up to Rs. 20 crore. Besides, he has set aside five acres of his land for putting up the plant.

The plant has come as a boon for the poultry farmers in the area as the waste is immediately collected by the Maltose plant. Says K.S. Ashok Kumar, who owns several poultry farms and a dairy in the area (he is M.Sc. in Agriculture), Ananda must be encouraged for his innovativeness and enterprise. Ashok says poultry and animals waste is a major pollutant which if not collected and treated, leads to not merely atmospheric pollution but also leads to clogging of drainage in the city.

He says the impact of non-treatment can be gauged by the fact that a ton of methane released leads to production of 24 tonnes of carbon dioxide.

Ashok says a huge amount of biomass is consumed by cattle in the city as well as suburbs. Unless their waste is systematically treated, it either remains on the scene or flows into the gutters, resulting in blockages in the flow. He says plants like Maltose play a healing role by restoring the energy cycle which gets ruptured due to production of and diffusion of methane into the environment. Besides, the manure from the plant returns the much needed humus to the soil and can cut down the fertilizer import bill if adopted on a wider scale.

According to Nadeem Fairoz, professor at the Department of Livestock Product Technology, Bengaluru has 1.6 lakh heads of cattle and three lakh other animals (mainly pet dogs, cats, cage birds, horses and donkeys). Due to inefficient collection, a considerable quantity of waste they generate flows into either the sewerage system or the drains.

Dr. Fairoz says biomethanation is the most productive treatment of the waste. He says a ton of putrescible waste consists of 77% water and 23% of solids. The anaerobic digestion can convert approximately 75% of those solids into biogas which is sufficient to produce 100 cubic metres of gas. The plant can be run with merely 20% of the energy it ultimately produces.

Win-win situation

Plants like Maltose have several benefits. They can be a replacement for landfills.

With low content of carbon in emission from them, the environmental dividends are huge. The residues from them can be used instead of organic fertilizers and the CNG is available at cheaper rates.

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