Clean substitute
Replacing coal with biomass can infuse life into ageing power plants and make them cleaner, while generating income opportunities for farmers
Replacing coal with biomass can make power plants cleaner and help farmers
GENERATING POWER from coal is a grubby business. 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.
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 agroresidues, 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 120 MW units into a 60 MW 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 agroresidues. In the absence of any consolidated figure with the government, estimates show that India produces some 550-650 million tonnes (mt) of agroresidues in a year; 160-180 mt of it is available for bio-energy.
SO, WHY THE PARADOX?
Before analysing this, let’s first understand how co-firing offers a win-win solution for India. 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. Estimates show that 85100 mt of agroresidues are burnt across India every year. Punjab, Haryana and Uttar Pradesh contribute 60 per cent of it. Upon burning, 1 tonne of agroresidue releases 1,400 kg of carbon dioxide (CO ), 58 2 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 (SO ). 2
First, co-firing helps avoid these emissions by creating a market for stubble. Second, it avoids emissions from the coal that gets replaced. Third, agroresidues emit less when burnt in power plants in controlled conditions and in the presence of pollution control technologies.
Delhi-based non-profit Centre for Science and Environment (CSE) has recently estimated the overall emissions reduction potential of biomass co-firing. It says 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 (see ‘More power to biomass’, p18). The transition can also generate economic opportunities in rural areas, say CSE researchers. 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 `2,000 and `2,500 a tonne. While farmers earn between `500 and `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, says the CSE researchers. Retrofitted boilers have another advantage: they can fire biomass when supplies are plentiful and switch back to coal when supplies are low. When an old plant works safely, efficiently and emits less, utility authorities can defer its retirement age, which at present is 25 years in the country. A number of plants operating across the world are as old as 40-50 years.
INDIA MUST ACT, FAST
Biomass co-firing has played a vital transitional role in the decarbonisation of coal power in Europe, USA and the UK. It has also extended the lives of the old plant fleet. In fact, all major coal plants in UK have adopted biomass co-firing. These countries have mandatory regulations to increase the share of renewables in the electricity sector. A number of Asian countries such as Japan, China and South Korea have also adopted co-firing. While Japan is experimenting to increase the blend ratio by up to 84 per cent, China, the world’s largest agroresidue generator, has drafted extensive policy to manage biomass production and trading. As per the International Energy Agency (IEA), power from biomass will increase by a factor of 10 until 2050, primarily through co-firing, accounting for 7.5 per cent of the global generation.
A major drawback for India is the round-the-year availability of agroresidue; 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. A perennial and higher blend ratio will thus require government support in terms of subsidy or other incentives.
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.
At the National Thermal Power Corporation (NTPC), which has been using biomass co-firing in its Dadri plant and plans to extend the practice to 18 other plants before the end of the year, an official says that 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.