According to reports, the recent hike in petroleum products has once again upset the common man’s budget and made yet another strong pitch in favour of adopting a safer, sustainable and economical alternative. Biogas for urban use is fast emerging as one. Urban India generates 1,88,000 tonnes of municipal solid waste per day, and this is expected to increase by one to 1.5 per cent every year. The waste includes both non biodegradable and biodegradable waste.
The biodegradable MSW holds the key to current energy crises, be it electricity or gas, as the high moisture content does not permit costly incineration or composting but is highly suitable for anaerobic digestion in a biogas plant. The average organic content in MSW is 50 per cent and every 150 tonnes of organic waste can generate up to one mega watt of electricity. This has been endorsed by the successful performance of waste to electricity projects in Vijayawada, Lucknow and Hyderabad. Up to 2,600 MW of electricity can be generated using urban waste. In Delhi, the Keshopur sewage treatment plant is another example. The STP generates raw gas which when supplied to the biogas plant can be upgraded to CNG quality gas that can be used to refuel and run up to 120 DTC buses at the adjoining bus depot.
Out of the 180 million metric tonnes of fruits, vegetables and perishables produced, nearly 25 per cent to 30 per cent is wasted due to storage capacity constraints. However, this presents an opportunity for energy generation. To cope with this, the regulations stipulate that all municipalities should adopt sustainable methods of handling MSW. Gas generation from biodegradable waste is providing twin benefits of solving the MSW disposal problem as well as producing valuable energy in the process.
According to Professor VK Vijay of the Centre for Rural Development and Technology, IIT Delhi, “Till now there was no compulsion to look earnestly for an alternative, but due to the rising prices of petroleum products people are now more open to considering other cheaper options. The Government should take proactive steps using the available technologies to ensure mandatory urban utilisation of biogas not only at institutional level such as hotels and hospitals, but also at household level.”
He added, “Government should incentivise biogas usage, especially as it is cheap to set up. For instance, the cost of a biogas plant that can service 16 to 20 homes is `1.5 lakh with a monthly maintenance charge of `6,000-8,000. However, the Government must ensure that community participation and awareness in waste segregation into biodegradable and non biodegradable is implemented effectively.”
The evolution of biogas is compressed biogas. CBG is the enrichment of biogas using various technologies such as water scrubbing.
Water scrubbing technology, developed and patented by IIT Delhi, is one of the cheap and viable technologies for biogas purification that bring biogas to CNG quality having high methane content. Water scrubbing technology is based on the physical phenomenon that at a high pressure water has high absorption affinity towards carbon di-oxide. This scrubs carbon di-oxide out of biogas and produces a gas with a higher methane concentration. CBG can be used for purposes such as cooking as it can be compressed and bottled, as well as for vehicular transport in place of CNG.
According to a research paper authored by Mr Vijay and another expert, Mr Dhawal Parate, the conversion of biogas to CBG and further sale as replacement of commercial CNG/LPG is a new and promising entrepreneurial model. Commercial LPG is expensive (`68/kg) and thus, its replacement with CBG is a profitable business. A 1000 cubic metre per day biogas generation, purification and bottling plant can be setup at a capital cost of `180 lakh with a payback period of less than four years. The Government has a subsidy model to support such projects. As one goes for higher capacity, the capital cost increases non-linearly resulting in better paybacks.
The Government’s role is encouraging, with the Union Ministry of New and Renewable Energy having a subsidy scheme for the promotion of biogas purification set-ups. Under this scheme, 22 plants have been approved at a 50 per cent subsidy as demonstration projects across the country.
Apart from this, the Government has set up committees to devise Bureau of Indian Standards composition standards for CBG. Simultaneously, standards for vehicular applications are being prepared; once completed, CBG will become approved fuel for all natural gas applications.
The day may not be far off when the customary red LPG cylinders are replaced with bright green CBG ones as the energy of the future, but a committed Government and continuous technological improvements are essential to ensure that future.