Sunday Reading

New Delhi, 7 October 2009

Biogas Plants

INDUSTRY BOOST TO KITCHEN WASTE

By Radhakrishna Rao

Kitchen waste need no longer be thrown in dustbins. Instead, it could be made good use of like some corporate houses and top firms are doing in the South. By setting up kitchen waste biogas plants at their complexes, managements have found a solution to disposing off food waste and importantly are able to generate clean energy for cooking in their canteens and cafeterias.

It started with the Mysore-based Centre For Renewable Energy and Sustainable Technologies (CREST), a unit of the National Institute of Engineering (NIE), getting involved in popularizing these biogas plants to provide cooking gas for households and corporate canteens. And it has made a beginning.

How does it work? According to its spokesman about 2-kg of kitchen waste including food left-overs used in the digester provide 500-gms of methane. And, installing a biogas plant is the easiest and most cost-effective way to make use of large piles of kitchen and other wastes. Depending upon the user requirement, the capacity of the biogas digester can be scaled up appropriately. Moreover, the residue in the digester turns out to be rich source of organic manure that can be profitably used in gardens and landscaping.

According to Enzen Global Solutions, which helps corporates and industry to set up biogas plants working on organic wastes including kitchen wastes, all organic wastes that include food, vegetables and leaves have the potential to generate methane gas in anaerobic conditions. The waste when fed into a digester starts the process of anaerobic digestion of organic material to yield methane through the process of bio-methanation. Apparently, “a 350-500-kg, plant can generate gas equal to one LPG cylinder.”

In Bangalore, many of the high-tech parks and corporate complexes are falling back on kitchen waste compact biogas plant. For instance, Velankanni Tech Park, which employs 4,000 people produces a waste food in its canteen to the extent of 100-kg plus per day. The waste food disposal here was mainly dependent on an external contractor. As such this tech park with the assistance of Enzen set up a kitchen waste biogas plant with a capacity of 250-kg wastes per day and an investment of Rs.50,000. “We are not only saving Rs.200 daily on the disposal of waste but also generating about 25-kg of cooking gas and saving about Rs.20,000 a month” says a manager.

Enzen is also assisting Vydehi Institute of Medical Sciences and Research Centre in Bangalore to set up a 300-kg capacity biogas plants. “Large capacity plants can also earn additional revenue for carbon credits,” says Ram Kumar.

Similarly, the software and IT giant Wipro also operates a 3-tonne capacity biogas plant at its campus in the Electronics City of Bangalore. ”We saw this as a great opportunity to reuse the food wastes from various cafeterias in the campus. The plant converts about 200-kg of food wastes into biogas on a daily basis, and in the process saving upto 16 LPG cylinders at full load”, says its official at its Environmental Division. He also notes that “disposal of waste at the source of generation and low sludge production are other advantages”.

India’s leading software and consultancy firm TCS at its Yantra Park on the outskirts of Mumbai operates a one tonne per day capacity biogas plant. “Based on the success of this plant, we are planning similar projects at all our new campuses and also at existing facilities. Provision of biogas plant is now a part of standard design of new facilities” says its Head, health, safety and environment.

Interestingly, this concept of kitchen waste biogas plants is an offshoot of a much larger plan at the national level. The country’s National Project on Biogas Development, launched in 1981-82, which was subsequently renamed National Biogas and Manure Management has so far been able to get around 4-million family type biogas plants installed as against the existing potential for 12-million digesters. The programme’s objective is to provide clean and efficient fuel for cooking along with organic manure to rural households. Equally important goal is to mitigate the drudgery for the rural women and reduce pressure on forests as a source of fuel wood.

However, the achilles heel of this programme is use of cattle dung as the feedstock to generate methane, considered a non-polluting and carbon dioxide-neutral fuel. For a family type biogas digester (technology that takes advantage of the energy that is naturally present in animal waste and kitchen trash), to be in operational trim at least 40-kg of dung is required on a daily basis. This implies that a rural household should own at lest six-eight cattle heads.

Moreover, because the dung has a retention period of 40 days, the biogas plants need to be large. As such, limitations in terms of space, investment and absence of sufficient number of animals have gone to slow down the process of popularizing family type biogas plants in the country. And, what‘s more the process of mixing the dung with water to prepare the feedstock is considered a tedious job by many rural households.

With a view to overcome the limitations associated with the family type biogas digester, the Pune-based Appropriate Rural Technology Institute (ARTI) came out with the innovative technology of alternative high calorie feedstock that is rich in starchy materials This feedstock has been found be more efficient in terms of the methane generated and also easy to handle. The feedstock that can be fed into these biogas digesters included kitchen waste, seed of any plants as well as oil cake of non edible oilseeds.

According to ARTI, this feedstock is capable of generating about 250-kg of methane per tonne of feedstock (on the basis of dry weight). More importantly, the reaction takes just one day to complete. It has been computed that the use of 2-kg of this feedstock on daily basis is good enough to provide cooking fuel needed by a family of five. More innovations are truly welcome. --- INFA

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