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29th October – Co-firing of coal plants

Ready to swap?

Worldwide, pressure is mounting to close coal-fired power plants that are old, inefficient and spew more carbon emissions. Yet, in June this year when the Punjab government decided to dismantle its 43-year-old Guru Nanak Dev (GND) thermal plant at Bathinda and sell the land, it raised quite a few eyebrows, expectedly.

What is the issue?

  • In 2018 a study by the Central Electricity Authority of India (CEA) and the Japan Coal Energy Centre (JCOAL), a Japanese institution, said the 440-megawatt plant, shut since 2017, could be refurbished to generate clean power.
  • The plant would burn agro-residues, in addition to coal, and thereby not only emit less but also help avert the thick smog generated by stubble burning in the region. It can thus set an example for reinventing utilisation of older coal power plants, suggested the study by CEA-JCOAL, working to ensure sustainable, low-carbon electricity supply in the country.
  • The Punjab State Power Corporation Limited (PSPCL) agreed to converting one of its 120MW units into a 60MW paddy straw-fired unit after its committee estimated that the cost of conversion was lesser than establishing a new biomass plant.
  • It also found that the conversion would decrease the cost of power generation and thus, reduce the burden on consumers.
  • While it remains unknown what prompted the government to order against PSPCL’s recommendation, the fact is biomass co-firing has failed to create a buzz in India even though it is among the largest producers of agro-residues.

Potential of bio-energy in India –

  • In the absence of any consolidated figure with the government, estimates show that India produces some 550-650 million tonnes (mt) of agro-residues in a year; 160-180 mt of it is available for bio-energy.
  • Under the technology, a part of the plant’s base fuel, coal, is replaced with biomass and burnt either in the same boiler or in separate units. This results in a sharp decrease in pollution load, particularly in regions where stubble burning is prevalent.

Benefits –

  • First, co-firing helps avoid these emissions by creating a market for stubble.
  • Second, it avoids emissions from the coal that gets replaced.
  • Third, agro-residues emit less when burnt in power plants in controlled conditions and in the presence of pollution control technologies.

Significance of co-firing –

  • Estimates show that 85-100 mt of agro-residues are burnt across India every year. Punjab, Haryana and Uttar Pradesh contribute 60 per cent of it. Upon burning, 1 tonne of agro-residue releases 1,400 kg of carbon dioxide (CO2), 58 kg of carbon monoxide (CO), 11 kg of particulate matter (PM), 4.9 kg of nitrogen oxides (NOx) and 1.2 kg of sulphur dioxide (SO2).
  • Co-firing helps reduce over 73 per cent PM, 47 per cent CO2, 5 per cent NOx, 98 per cent SO2 and 99.6 per cent CO.
  • It creates business opportunity for pellet and briquette manufacturers as coal plants prefer using biomass in compressed forms. Factory-gate price at these units varies between Rs 2,000 and Rs 2,500 a tonne. While farmers earn between Rs 500 and Rs 1,500, the rest goes to labourers engaged in collection, loading, unloading and transportation.
  • Trials show existing infrastructure in the country is sufficient for low blend ratio of 5-10 per cent biomass. Even for higher blend ratios, the cost is just 10-20 per cent of the establishment cost of a standalone biomass power plant.
  • Retrofitted boilers have another advantage: they can fire biomass when supplies are plentiful and switch back to coal when supplies are low.

Challenges –

  • A major drawback for India is the round-the-year availability of agro-residue; it can be procured in bulk only during the harvest time. This is an impossible task for small industries and pellet and briquette manufacturers who do not have the capacity to buy or store biomass in such huge quantities. For the power plants, the cost will keep increasing as blend ratio goes up.
  • Though the Ministry of New and Renewable Energy has last year included biomass in the list of renewable energy, it suffers the same fate as any other non-solar renewable energy. State regulators have a target to source a certain amount of electricity from these sources under renewable purchase obligation. But utilities have defaulted on these targets due to lack of enforcement mechanism and non-existent penalties.

Way forward –

  • One way of promoting co-firing is to move the plants up the merit order—a ranking that enables distribution companies to buy from plants that offer electricity at cheaper rate.
  • At present, coal power plants in Punjab and Haryana feature at the bottom of the merit order because they are located away from the coal mines. This makes coal expensive for them and their electricity costly. Since biomass is available in plenty in these regions, the government can help them shift to co-firing on a priority basis and simultaneously push them up the merit order, suggests the official.
  • The government should also fix a price for procurement. This will help stabilise the market faster.

SourceDown To Earth

QUESTION – Co-firing of coal and biomass such as agri-residues could provide a clean solution to thermal power plants. Discuss.

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