Author – Sakshi Gupta
The modern society’s ever increasing energy consumption will exhaust all major non-renewable energy sources by the end of this century. Further, the fossil fuel-based energy production harms the nature in gruesome ways by causing global warming, air, water and land pollution.
In order to ensure our sustainability, we need to switch to eco-friendly energy sources such as solar, wind, biogas, biodiesel, etc. Among them, biogas could be the best source of energy in India, since it not only provides cheap fuel, but it also has a solution for proper organic waste disposal without causing any kind of pollution. It is one of the fastest growing renewable sources of energy today.
‘Biogas’ is a term used for a mixture of gases produced from anaerobic digestion (reaction in the absence of oxygen) of the organic waste material. Major gases that comprise biogas are methane and carbon dioxide, which give it fuel like properties along with traces of hydrogen sulfide and siloxanes.
Production of biogas is a simple method involving some organic raw materials that are made to undergo anaerobic digestion in a biodigester. All kinds of organic waste ranging from agricultural waste to manure from cows, pigs and horses, human feces or industrial organic waste to municipal organic waste. Preferred sources are ones with high energy value, which allow easy digestion. Acidic materials are avoided as they might harm the microbes. A biogas plant consists of a biodigester, a tank where the raw material is fed and anaerobic bacterial action takes place. This generates biogas at the top of the tank leaving behind liquid slurry at the bottom, which could be used as organic manure for plants. A biogas production unit can erected either at a small or a large scale, depending on the amount of raw material available and the investment.
In India, we have many small scale plants established across the nation among dairy farms with cattle herd of 8-10 animals. It does not require much of an investment or time for installation and generates energy, which could be directly used for electricity generation or converted to bio-CNG or bio-methane, and then utilized for purposes similar to that of compressed natural gas. ‘Bio-CNG’ is combustible biogas that is cleaned to the specifications of natural gas, while bio-methane is biogas with higher concentrations of methane and little carbon dioxide.
The amount of combustible gas produced by small scale biogas plants is less than 40,000 cubic meters. Medium-scale biogas plants produce gas of around 40,000-200,000 cubic meters. These plants mainly utilize raw material such as municipal, industrial and agricultural waste. Industrial waste would be organic by products from industries such as food, beverage or pharmaceutical. Some mid-scale plants such as Green Elephant in India, which has established the Peshwe Park Project consisting of two large scale biogas power plants for Pune Municipal Corporation, it was set up in 2010 it has even expanded to include 3 more plants in 2013.
Another plant is for a corporate company, where waste obtained from the canteen of Tata Consultancy Services, produces 200 cubic meters of biogas every day. There had been a special Volkswagen project called Greenbox 500, this project produces 40 cubic meters of gas processing 500kgs of waste everyday, which is then used to heat stoves kitchen rather than power generation. However, direct conversion of biogas to energy is under research till now, with help of fuel cell. The current employed technique is utilizing biogas as a fuel for combustion engines, which in turn power an electric generator to produce electricity.
Biogas can effectively be utilized for electricity generation through a biogas-based power generation system after dewatering and cleaning of the gas. A Biogas power plant consist of a Biogas plant, a gas cleaning system, 100% Biogas Engine with alternator, Control panel etc. Hydrogen sulphide gas present in biogas is very harmful to the engine, so it has to be removed through the gas cleaning system.
Large scale biogas plants are the ones where more than 200,000 cubic meters of gas is produced. Here all kinds of organic materials are used for production. Since a large amount of gas is generated, it is directly converted into electricity. The largest biogas plant in India is in Satara district, Maharashtra which is also established by Green Elephant. Here 25,000 cubic meters of biogas is generated every day from 600 tons of sugarcane waste obtained from sugar mills in the vicinity. Gas obtained is converted to compressed biogas (CBG) and used as fuel. This plant uses an advanced Continuous Stirred Tank Reactor for faster anaerobic process. Green Elephant has planned to establish 2-3 more large biogas plants in India by 2015. The New & Renewable Energy Development Corporation of Andhra Pradesh has built a 200-cubic metre plant in Krishna district, which generates 20KW of power per day.
Another large biogas plant is made under the National Biogas & Manure Programme by the Ministry of New & Renewable Energy. This plant produces nearly 936,000 cubic meters of biogas per day. They came up with technology of pre fabricated digesters to reduce the losses made by these plants. Further, the NBMMP project supports 13 regional development and training centers to empower people with the right knowledge for business in this area.
People are becoming aware and have begun to build such plants on small and large scale in various parts of the country. City dwellers are yet to realize the immense business opportunity of utilizing municipal or industrial waste for biogas generation. There are many Indian firms who deal with the construction of biogas plants such as Jain Irrigation System Ltd, Indian Biogas Association etc. If we provide them with information about the source of material and amount, land available, and money, these companies can build these plants on a turnkey basis, planning and constructing the entire set-up.