India, the second-largest agro-based economy with year-round crop cultivation, generates a large amount of agricultural waste, including crop residues. In the absence of adequate sustainable management practices, approximately 92 seems a very small number of metric tons of crop waste are burned every year in India, causing excessive particulate matter emissions and air pollution.
Recently, crop residue burning has become a major environmental problem causing health issues as well as contributing to global warming and results in loss of plant nutrients like N, P, K and S. Therefore, appropriate management of crop residues assumes a great significance.
Reasons behind on-farm burning of crop residues
The practice of burning is not a new idea but started many generations ago with the burning of grasslands. Burning is an inexpensive, labour efficient means of removing unwanted crop residues prior to tillage or seedbed preparation. On farm burning traditionally provides a fast way to clear the fields off the residual biomass, thus, facilitating land preparation and sowing/planting. It also provides a fast way of controlling weeds, insects and diseases, both by eliminating them directly or by altering their natural habitat. The two states namely Punjab and Haryana alone contribute to 48 % of the 13915 Gg (Giga gram=10 billion gram) rice straw surplus produced in India and are subject to open field burning (Gadde et al., 2009).
Due to increased mechanization, particularly the use of combine harvesters, declining numbers of livestock’s, long period required for composting and unavailability of alternative economically viable solutions, farmers are compelled to burn the residues. The number of combine harvesters in the country, particularly in the Indo-Gangetic Plains (IGP) has increased dramatically from nearly 2000 in 1986 to over 10000 in 2010. The north-western part (Punjab, Haryana and Western Uttar Pradesh) of the IGP has about 75% of the cropped area under combine harvesting.
Combine harvesters are used extensively in the central and eastern Uttar Pradesh, Uttarakhand, Bihar, Rajasthan, Madhya Pradesh and in the southern states as well for harvesting rice and wheat crops.
Major reasons for the rapid increase in the use of combines are labour shortage, high wages during harvesting season, 9 ease of harvesting and thrashing and uncertainty of weather. On using combine harvesting; about 80% of the residues are left in the field as loose straw that finally ends up being burnt on farm. There are some other reasons also behind the intentional burning of crop residues. These include clearing of fields, soil fertility enhancement, and pest and pasture management. The time gap between rice harvesting and wheat sowing in north-west India, for example, is only 15-20 days. In this short duration, farmers prefer to burn the rice straw on-farm instead of harvesting it for fodder or any other use. The latter options also involve a huge transportation cost.
Adverse Impact of Crop Residue Burning on the Environment
Burning of crop residues leads to the release of soot particles and smoke causing human and animal health problems. It also leads to the emission of greenhouse gases namely carbon dioxide, methane and nitrous oxide, causing global warming and loss of plant nutrients like N, P, K and S. The burning of crop residues is wastage of valuable resources which could be a source of carbon, bio-active compounds, feed and energy for rural households and small industries. One ton of rice straw on burning releases about 3 kg particulate matter, 60 kg CO, 1460 kg CO2 , 199 kg ash and 2 kg SO2 (Gadi, 2003).
Many pollutants found in large quantities in biomass smoke are known or suspected carcinogens and could be a major cause of concern leading to various air-borne/lung diseases. It is also estimated that burning of crop residues in situ releases about 627 kilo tonnes (Kt) of PM10 and 4677 Kt of carbon monoxide to the atmosphere annually in India (TERI 2019). The heat generated from the burning of crop residues elevates soil temperature causing the death of active beneficial microbial population, though the effect is temporary, as the microbes regenerate after a few days. Repeated burnings in a field, however, diminishes the microbial population permanently.
Sustainable management of Crop Residue
The sustainable management of agricultural waste has become a great challenge, especially for developing countries such as India with an increasing population, production rates and economic growth. If a solution involves making another product out of crop residue, such a product should have a secured market for this solution to succeed. In certain cases, logistic issues in the transportation of the materials to larger distances also adds to the cost. In this context, it is believed that the best alternatives could be the ones that make end-products to be used by the agricultural industry itself, and on-site if possible. Composting, biochar production and mechanization are such few effective sustainable techniques that can help to curtail the issue while retaining the nutrients present in the crop residue in the soil.
Most of the government interventions thus far have mainly focused on the energy production out of crop residue, particularly biogas production. In the states of Tamil Nadu, Bihar, Assam, West Bengal and Jammu and Kashmir, crop residues are being used as a source for animal feed. Some of the residues are processed to be used in construction applications, such as the use of rice husk ash in cement mixtures. Banana peels and sugarcane waste are being utilized in the paper industry, while husk and bagasse ash are utilized for mushroom cultivation. Alternative measures have long been suggested by scientists and agriculturalists over the past decade to counter crop residue burning, but due to a lack of awareness and social consciousness among the farmers these measures have not been fully implemented. This could be one of the reasons why biogas production has prospered while other alternatives such as using crop residue as raw material for animal feed, paper industry, construction industry have not become very popular.
Government Intervention
The Indian Government has attempted many interventions to curtail the amount of crop residue burning through different campaigns. May such past attempts involved advocacy and encouragement to use crop residue in the energy sector as a raw material. The Indian Agricultural Research institute (IARI), Indian Ministry of New and Renewable Energy (MNRE) are continuously promoting research and innovative measures to handle crop waste without burning. The National policy for management of crop residue (NPMCR) recently formulated by the Central Government, has laid out policies and regulations to be undertaken by the local agencies to curb crop burning and initiatives towards sustainable management practices. As a result, the National Remote Sensing Agency (NRSA) and the Central Pollution Control board (CPCB) now monitor crop burning through aerial surveillance and penalize farmers who burn crops.
A) Initiative towards Biogas Plants
Biogas plants are a progressive step taken by the Government of India to curb crop burning and to prevent pollution. These programs were implemented by the Government under the “waste to energy mission”. Large scale industrial biogas plants generate 5000 m3 of bio gas per day. Nearly 400 off-grid biogas power plants have been set up with a power generation capacity of 5.5 MW. Currently there are 56 biogas-based power plants operational in India, the majority of them are in the states of Maharashtra, Kerala and Karnataka. Recent developments in technology have opened the possibility of using paddy straw and other crop residue other than dung and vegetable waste for biogas generation in an integrated approach.
B) National Schemes and Policies
The Government of India directed the National Thermal Power Corporation (NTPC) to mix crop residue pellets (nearly 10%) with coal for power generation. This helped the farmers with a monetary return of approximately Rs. 5500 per ton of crop residue. These profitable measures are yet to be in action and it can be successfully exploited by the farmers. In various government schemes farmers from different states were trained for agro-waste bio-conversion and bio-compost production. These large-scale efforts supported farmers in gaining economic advantages.
Ministry of Agriculture of India recently developed a National Policy for Management of Crop Residue (NPMCR) with the following main objectives:
(1) Promote the technologies for optimum utilization and in-situ management of crop residue, to prevent loss of valuable soil nutrients, and diversify uses of crop residue in industrial applications.
(2) Develop and promote appropriate crop machinery in farming practices such as modification of the grain recovery machines (harvesters with twin cutters to cut the straw). Provide subsidy, discounts and incentives for purchase of mechanized sowing machinery such as the happy seeder, turbo seeder, shredder and baling machines.
(3) Use satellite-based remote sensing technologies to monitor crop residue management with the National Remote Sensing Agency (NRSA) and Central Pollution Control Board (CPCB).
(4) Provide financial support through multidisciplinary approach and fund mobilization in various ministries for innovative ideas and project proposals to accomplish above.
With the help of remote sensing crop burning area can be tagged and as a significance, states like Rajasthan, Punjab and Haryana imposed fines between Rs. 2500 to Rs. 15,000 (35 to 210 USD) on farmers indulging in crop-burning. The National Green Tribunal, a government enterprise, stablished under the National Green Tribunal Act laid down stringent directives to the states to curb crop burning through recycling initiatives and spread proper awareness among the people. With the vigilance of government agencies, the states of Punjab and Haryana have witnessed a reduction of 38% and 25% in crop stubble burning, respectively. Therefore, educating and empowering the farming stakeholders are crucially important steps to make a significant impact. Creating awareness raising campaigns should always run parallel to implementation of a practical solution that empowers them not only technically, but also economically.
Source: Bhuvaneshwari S., Hettiarachchi H., Meegoda J.N. Crop residue burning in India: Policy challenges and potential solutions. Int. J. Environ. Res. Public Health. 2019; 16:832. doi: 10.3390/ijerph16050832
TERI (2019) Development of Spatially Resolved Air Pollution Emission Inventory of India. New Delhi: The Energy and Resources Institute
