Stubble burning: Researchers look for tech solutions as daily fire count crosses 1,000 mark in Punjab, HaryanaUpdated: Oct 26, 2020, 00:06 IST
Burning of rice stubble has started earlier than usual this year with daily fire counts crossing the 1,000-mark in Punjab and Haryana combined, revealed the data by Council on Energy, Environment and Water (CEEW), an independent policy research institution, on Thursday.
Stubble or straw is the residue left behind in large quantities after harvesting the paddy crops. Most farmers are forced to burn the stubble as a quick way of getting rid of the residue so they can begin sowing the next crop. This mass burning of agriculture residue leads to emission of particulate matter (PM-10 and PM-2.5) and greenhouse gases (GHG), which contribute to the poor air quality in Punjab, Delhi and the National Capital Region (NCR).
Between September 1 and October 20, the CEEW has recorded more than 9,000 fires. Simultaneously, the air quality in Delhi-NCR has dropped to a very poor category with air quality index (AQI) crossing the 300 mark. AQI value over 300 represents hazardous air quality.
The harvest of rice in Punjab, Haryana and Uttar Pradesh, which usually peaks at the end of October, will mature early this year. In July a labour shortage induced by the Covid-19 pandemic forced farmers to sow their rice seeds directly in the fields instead of transplanting seedlings from nurseries.
With rice crop maturing eight to 10 days earlier than usual, harvest season has kicked off, as have rice stubble burning incidents.
While the central and state governments are trying out a host of policy measures and alternatives for collection and disposal of stubble, science and technology institutes are also working on interventions for processing the waste.
Addressing problem at the root
Punjab Agricultural University (PAU), Ludhiana, which has seen moderate success with the widely used happy seeder—a tractor-operated machine that can sow wheat seeds even in standing paddy stubble—has also developed hybrid straw management systems (SMS). A super seeder is a tractor-mounted machine that can plough the stubble and sow wheat seeds simultaneously. “It is a combined harvesting system,” said Mahesh Kumar Narang, principal extension scientist, farm machinery and power engineering, PAU.
However, the super seeder throws the ploughed straw to the centre of the field and additional labour may be required to remove the straw. To address this, the PAU has developed Super SMS, which can be fitted to the super seeder. The Super SMS chops the ploughed straw evenly and distributes it evenly over the field. This helps manage the entire straw residue within the field. The super seeder is currently priced at ₹1.10 lakh, he added. “For a farmer, the price for using the super seeder is almost ₹350 to ₹400 more per acre than using a happy seeder. However, the labour cost of mulching the stubble is eliminated,” said Narang.
Along similar lines, the Indian Institute of Technology (IIT), Ropar, has designed a stubble removing machine (SRM) and collection trolley, which can cut the stubble and collect the residue in a trolley at the same time. Happy seeder, super seeder and SRM are comparatively cheaper than traditional balers that are priced at ₹7-8 lakh, said Narang.
High yield and green alternative to coal
The rice straw holds potential as an alternative to coal in thermal power plants is widely accepted. However, paddy residue has seen very little success in its use as fuel in power plants because it has to be processed before it can be used as a fuel in a thermal plant.
The Council of Scientific and Industrial Research-National Physical Laboratory (CSIR-NPL) in Delhi, proposes heating the straw at very high temperatures in controlled conditions to convert the residue into high-yield bio coal—an environment-friendly alternative to coal.
“There are inherent problems in using raw rice straw as fuel because there is high moisture content and the gross calorific value (GCV) is low, which makes it difficult to use in large scale,” said Sanjay Dhakate, chief scientist and head of advanced carbon products group, CSIR-NPL. The solution proposed by Dhakate is using heat in a controlled environment to convert agri-waste into coal-like material. This is called torrefaction.
As a pilot, NPL has set up a small stainless-steel plant in its lab for torrefying rice straw by applying heat from 250 to 400 degrees Celsius. The plant redirects the gases emitted to generate power to back the plant in turn. “We have found that on torrefaction at 250°C, the GCV of the residue is 3,762 kcal/kg and it further increases to 4,342, 5,129 and 5,339 kcal/kg with an increase in torrefaction temperature from 300°C to 400°C,” said Dhakate. This is comparable to the calorific value of coal used in thermal plants (6000-8000 kcal/ kg). The NPL is currently working with National Thermal Power Corporation Limited for large-scale implementation of torrefaction of rice straw.
Darpan Das, a postdoctoral fellow at Johns Hopkins University, USA, also endorses torrefaction. He offers the concept of ‘briquetting’ of rice straw to curb emissions, a process involving compaction of fuel to an energy-densified material. Formerly a PhD student at IIT-Bombay, Das has used the same, as a strategy to reduce emissions from domestic applications of coal in cookstoves. “This can be used for agro-residues for efficient conversion to bio-briquettes which can cater to the household energy needs of the country. Briquettes can also serve as additional support to the Pradhan Mantri Ujjwala Yojana scheme of providing LPG to every citizen,” said Das.
Cost, feasibility a challenge for implementation, say experts
Collection of rice straws is a labour-intensive and expensive process, even with the machines in place, say experts. In Punjab alone, around 13,000 happy seeders and 200-odd super seeder machines were deployed last year, according to Narang. For a state that generates 19.7 metric tonne of paddy straw, the CEEW estimates the requirement of 35,000 happy seeder machines.
“While there is a rise in takers for the machines with the subsidy offered by the government, there is a big gap in the number of machines that are required and are available,” said LS Kurinji, research analyst, CEEW. Large-scale dissemination of technology is a challenge in implementation, agreed Das.
There are 290 manufacturers of various straw management machines empanelled with the government of India. In Punjab, individual farmers get a 50% subsidy on the purchase of a machine and cooperatives can avail a subsidy of 75%. “The subsidy for buying straw management machines should continue for at least three more years so that farmers continue to invest in them,” said Ajay Vir Jakhar, chairperson of the Punjab state farmers’ and farmworkers’ commission.
For power plants to substitute coal with biomass, too, is not an easy task. “Technologically it is possible to use rice straw as fuel in thermal power plants. The problem is the plants are too far away from the paddy fields. This adds to the transportation cost. Ideally, Punjab and Haryana should buy up the agri-waste to fuel the power plants within the states,” said Ajay Mathur, director-general of The Energy and Resources Institute.
“Instead of dictating a policy to promote the use of biomass as a coal substitute in power plants, the government should set out guidelines for disposing of rice straw in an environment-friendly way. This will give entrepreneurs and researchers to find disruptive solutions to the problem,” said Jakhar, adding that to promote innovation, the government should set up funds for competitions seeking solutions.
The problem: The air quality in north India, particularly along the Indo-Gangetic plains, stoops to dangerously low levels between October and November every year. This is also the time when farmers in the region set fire to their agricultural waste after harvesting their paddy fields.
Punjab, Haryana and Uttar Pradesh are the biggest producers of rice in the country in the Kharif season between May and November every year. In 2017-18, almost 62% of all the rice procured by the Food Corporation of India came from these states.
Harvesting begins in October and peaks by the end of the month. At the end of the harvest, stubbles of paddy are left rooted in the fields. Farmers usually have barely two weeks to clear this stubble so they can start sowing the next crop, which is wheat.
Left with a heap of unwanted rice stubble, with little time to dispose of it, farmers set fire to the heaps and use the ash as a fertiliser. However, stubble burning emits greenhouse gases and harmful particulate matter into the air, which leads to pollution. Punjab alone generates 19.7 million metric tonnes of rice straw in a year.
Burning of rice straw releases particulate matter and harmful gases such as carbon monoxide and nitrous oxide. These emissions pose severe health risks and can be detrimental to lung functions.