By Khushboo Goyal
Biogas is a mixture of different gases produced by the breakdown of agricultural waste, manure, municipal waste, plant material, sewage, green waste, or food waste, in the absence of oxygen. When this mixture is further purified and processed, it is called bio-compressed natural gas (bio-CNG). It is similar to natural gas in terms of its composition and properties, and is a cleaner alternative to fuels such as petrol and diesel.
In India, bio-CNG has immense scope, specifically as a replacement for the more widely used CNG and liquefied petroleum gas (LPG). Besides, bio-CNG can cater to diverse segments of the market with applications in commercial (hotels, canteens, bakeries and resorts), industrial (glass and ceramic, metal processes, cement and textiles) and automotive (public transport and private vehicles) processes.
Apart from replacing CNG and LPG, bio-CNG can be used in lieu of biogas, which has an estimated market potential of 1,281 MW. For instance, distilleries, and sugar and starch factories meet about 75 per cent of their energy needs through biogas, and thus could be the potential consumers of bio-CNG as well. Other industries like milk processing, pulp and paper, and slaughterhouses could also utilise bio-CNG to meet their energy needs.
Bio-CNG is produced from biogas, through a simple and convenient process involving desulphurisation, upgradation and compression. First, biogas is desulphurised if the hydrogen sulphide content is over 1,500 ppm. Then, the desulphurised biogas is upgraded to make its composition similar to CNG, followed by the compression and bottling of the resulting bio-CNG.
Bio-CNG contains about 92-98 per cent methane and only 2-8 per cent carbon dioxide, while biogas contains 55-65 per cent methane with 35-45 per cent carbon dioxide. The calorific value of bio-CNG is about 52,000 kilojoules (kJ) per kg, which is nearly 167 per cent higher than that of biogas at 19,500 kJ per kg. The high methane content and calorific value combined with the low quantity of moisture, hydrogen sulphide and impurities makes bio-CNG an ideal fuel for automobiles and power generation. The low emission levels of bio-CNG also make it a more environment-friendly fuel than biogas.
As per Renewable Watch Research, there are 17 bio-CNG plants in the country, aggregating a capacity of 46,178 kg per day. Most of these plants are located in the western and northern regions of the country, which account for approximately 96.5 per cent of the bio-CNG capacity. These plants are spread over nine states, of which Maharashtra is in the lead in terms of the largest capacity as well as the highest number of plants. Gujarat comes second in terms of capacity, while Rajasthan ranks second in terms of the number of bio-CNG plants. In fact, Maharashtra and Gujarat together account for 63 per cent of the country’s total installed bio-CNG capacity.
In addition to these 17 plants, the National Agricultural Cooperative Marketing Federation of India is planning to develop a bio-CNG facility near Azad Mandi in New Delhi, with Indraprastha Gas Limited (IGL) poised to procure the bio-CNG produced at this plant. In January 2018, the Punjab Bureau of Industrial Promotion and Punjab Energy Development Agency signed an MoU with Indian Oil Corporation Limited (IOCL) for setting up biogas and bio-CNG projects in the state, at a total investment of Rs 50 billion. The state government plans to scale these up to 400 units over the course of the next few years. The Ministry of Petroleum and Natural Gas is also planning to set up bio-CNG plants across the country at a cost of Rs 70 billion, through partnerships with IOCL, Bharat Petroleum Corporation Limited, Hindustan Petroleum Corporation Limited and GAIL (India) Limited.
The installation costs of bio-CNG plants, along with the segregation and processing costs of waste, are considerable, which can limit their adoption. The lack of skilled professionals is also a major constraint at the moment, which will get bigger in the future unless skill development in the country keeps pace with the technological advancements. Further, there are no set standards for the waste-to-energy (WtE) segment, which is also hindering the large-scale uptake of bio-CNG in the country.
However, in the near future, the large amounts of waste generated in the urban and rural areas, combined with government initiatives to tackle this waste, will drive the growth of bio-CNG in India. To this end, the Ministry of New and Renewable Energy (MNRE) is providing financial support for the research and development of all WtE plants, including bio-CNG. A capital subsidy of Rs 10 million is offered per MW of power or per unit of bio-CNG from 12,000 cubic metres of biogas in a day, with a maximum cap of Rs 50 million per project.
In addition to this, the Galvanising Organic Bio-Agro Resources Dhan (GOBAR-DHAN) scheme, aimed at the management and conversion of cattle dung and solid waste into compost, fertiliser, biogas and bio-CNG, was announced in the Union Budget 2018-19 and is to be launched soon. From April 2020, stricter Bharat Stage-VI standards will also be rolled out to scale down sulphur emissions. These standards will increase the costs of petrol and diesel, thereby making CNG more cost efficient for trucks and buses. Given the huge amounts of waste generated in the country, bio-CNG will certainly emerge as a more feasible option than CNG.