Crop Residue Burning in India: Potential Solutions

Abstract

With its second-largest agro-based economy and year-round crop production, India produces a lot of agricultural waste, including crop residues. Because India lacks effective sustainable management methods, an estimated 92 seems like a very small quantity of metric tons of crop waste burned each year, causing excessive particulate matter emissions and air pollution. Burning crop residue has grown into a serious environmental problem that threatens human health and causes global warming. Composting, making biochar, and mechanization are a few effective sustainable solutions that can assist in resolving the issue while maintaining the nutrients found in the agricultural residue in the soil. In order to promote environmentally friendly management practices, the Indian government has launched a number of programs and campaigns.

1. Introduction

The global economic expansion is significantly influenced by the agricultural sector. However, the handling of agricultural waste receives scant attention in the literature. It might be connected to the fact that the agricultural industry is not as strictly controlled as the municipal solid waste industry (MSW). Since municipalities and other public institutions are primarily in charge of managing MSW, data on generation and management are gathered, kept track of, and examined in public. Agricultural wastes are materials left over after different agricultural processes. Agricultural waste, according to the United Nations, often consists of manure and other wastes from farms, poultry houses, and slaughterhouses; harvest waste; fertilizer run-off from fields; pesticides that enter water, air, or soils; and salt and silt drained from fields [1, 2, 3]. With little engagement from the public sector, agricultural waste is primarily managed by the owners of the agricultural land, who are primarily in the private sector. The world’s food output has greatly increased as a result of the rising food demand in developing nations. The multiplicity of agricultural operations raises the quantity of agricultural products produced, which has an overall negative impact on the environment by increasing waste production. Due to advancements in water management systems, contemporary agro technologies, and extensive pesticide deployment, enormous swaths of wasteland have been transformed into agricultural fields [1]. These actions have exacerbated environmental degradation on a global scale and complicated the process of disposing of agricultural waste. To manage these wastes, including their conversion into useable resources, the national agencies are continuously creating policies and other potential approaches. The term “harvest trash,” more often known as “crop residue,” refers to both the field residues that remain in an agricultural field or orchard after the crop is harvested and the process residues that are left over after the crop is processed into a useful resource. Field remnants commonly include stalks and stubble (stems), leaves, and seedpods. Molasses and sugarcane bagasse are two examples of process leftovers that are useful (Figure 1) [2, 4, 5].

Figure 1.

Burning of rice residues, a prevalent practice in northwest India.

2. Crop residue: composition and decomposing mechanisms

These crop residues are a summary of the general categories of crop residues produced by the major cereal crops and sugar cane, in particular as a field residue is a natural resource that traditionally contributed to the soil stability and fertility through direct plowing into the soil or by composting. Cellulose, hemicellulose, and lignin make up the majority of plant biomass, with smaller amounts of pectin, protein extractives, sugars, nitrogenous material, chlorophyll, and inorganic waste [6, 7, 8]. Lignin is almost impermeable and offers the structural support compared with cellulose and hemicellulose. Lignin is extremely resistant to both chemical and biological degradation, which helps it resist fermentation [8, 9]. The term “lignocellulosic biomass” refers to the parts of plants that are not used for food, such as the stalks, straw, and husk [5]. The majority of the lignocellulosic biomass is made up of the four most important agricultural crops farmed worldwide: sugarcane, wheat, rice, and maize. The lignin layer is typically pretreated with lignin degrading microorganisms to break down the lignin layer and degrade cellulose and hemicellulose matter to the corresponding monomers and sugars for efficient biomass to fuel conversion [6] because it is resistant to chemical and biological degradation by fungi, bacteria, and enzymes. Mechanical, chemical, physicochemical, or biological pretreatment options are available. These techniques lead to an increase in the accessible surface area, porosity, and degree of polymerization, as well as a decrease in the crystallinity of cellulose and hemicellulose. Utilizing microorganisms to control agricultural waste could also be a great way to detoxify the soil and reduce environmental pollution [10]. The complex materials in the biomass are broken down by microbial communities into simpler elements that can be recycled or reused in other parts of the ecosystem. Depending on the type of bacteria, fungi, or algae involved in the degradation, the processes used can either be aerobic or anaerobic [11, 12].

3. Adverse impact of crop residue burning on the environment

Crop residue burning causes a variety of environmental issues. Burning crop residue has several negative effects, but the main ones are the release of greenhouse gases (GHGs) that contribute to global warming, elevated levels of particulate matter (PM), and smog that pose health risks, loss of agricultural lands’ biodiversity, and deterioration of soil fertility [13]. Burning crop residue dramatically raises air pollution levels of CO₂, CO, NH₃, NOX, SOX, non-methane hydrocarbon (NMHC), volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), and particulate matter (PM) [14, 15]. In essence, this explains why organic carbon, nitrogen, and other nutrients that would normally have been kept in the soil have been lost [13, 16].

Crop residue burning in Delhi produces 17 times as much particulate matter (PM) as all other sources combined, including industry, burning of waste, and vehicle emissions [17]. As a result, the residue burning in India’s northwest produces almost 20% of the country’s total organic and elemental carbon emissions from burning agricultural waste [13]. Crop burning contributes greatly to climate change by raising the amount of particulates (PM) in the atmosphere. The release of fine black and brown carbon (primary and secondary), which alters light absorption, is one factor in global climate change [7, 18, 19]. According to their aerodynamic diameter and chemical makeup, PM2.5 and PM10 particles in the air are typically divided into two categories: fine and coarse particles, respectively. PM2.5 particles have an aerodynamic diameter of less than 2.5 and 10 m, respectively. Lightweight particles can move farther with the wind and can remain suspended in the air for longer [16, 20]. Because the particles are light and linger in the air for a longer period of time than heavier ones do, the effect of particulate matter is exacerbated by meteorological conditions. In the Patiala area of Punjab, the yearly contribution of PM2.5 from paddy residue burning was estimated to be between 60 and 390 mg/m³ [13].

4. Sustainable management practices for crop residue

Over the past 10 years, scientists and agriculturalists have long recommended alternative strategies to prevent crop residue burning, but due to farmers’ lack of understanding and social conscience, these measures have not been properly adopted. This section contains information on three such agricultural applications that have, for a variety of reasons, either been disregarded or skipped. They are in-situ management by mechanical intensification, biochar, and composting.

5. Composting

Composting is the naturally occurring, under regulated conditions, rotting or breakdown of organic waste by microorganisms [21]. Compost, which is a rich source of organic matter, is crucial for maintaining soil fertility and promoting sustainable agricultural output. Composting the soil enhances its physical, chemical, and biological qualities and can entirely replace the use of agricultural chemicals such as fertilizer and pesticides. The advantageous impacts of compost supplemented soil include greater potential for increased yields and resilience to environmental conditions such as drought, disease, and toxicity [21, 22, 23]. Due to increased soil microbial activity, these methods also aid in greater nutrient uptake and active nutrient cycling.

The organic matter is treated twice during the composting process.

1. Degradation: The initial stage of degradation begins with the breakdown of organic compounds that are simple to digest, such as sugars, amino acids, and organic acids. In addition to releasing carbon dioxide and energy, aerobic microbes also absorb oxygen. The initial thermophilic phase, which lasts for a few weeks to months, is characterized by high temperature, high pH, and humidity, all of which are necessary for activating the microorganisms [24]. Additionally, it is made sure that the substrate is adequately supplied with oxygen during this period [25].

2. Maturation: During the subsequent few weeks, more complex organic compounds are broken down, which is followed by a decline in the microbial population. When the temperature drops to 40–45°C, the phase transition from thermophilic to mesophilic occurs [25, 26, 27]. At the last step, the system’s biological activity decreases as the temperature falls to an ambient level. Finally, a soil-like substance with a dark brown to black hue is created. This soil-like substance also has a higher humus content, a lower carbon-nitrogen ratio, and a pH that has been neutralized [21]. Eventually, the biomass is changed into a nutrient-rich substance that can enhance the soil’s structural qualities [28].

6. Biochar

The thermochemical process known as pyrolysis, which occurs at low temperatures in an oxygen-free atmosphere, produces biochar, a porous material with fine-grained carbon content [29]. It is a mixture of varying amounts of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulphur (S), and ash [30]. The very porous characteristic of biochar, when added to soil, aids in better water retention and increased soil surface area. As a result, there is more interest in using soil amendments such as biochar, black carbon, and charcoal to stabilize soil organic content. These methods are thought to be an effective way to reduce agricultural waste while also reducing GHG emissions. In order to reduce the amount of CO₂ or methane released into the atmosphere, the process of carbon sequestration essentially calls for longer residence times and resistance to chemical oxidation of biomass to CO₂ or reduction to methane [8, 9]. The partially burned byproducts are pyrogenic carbon/carbon black, which undergoes a very slow chemical change to create a long-term carbon sink that is perfect for soil amendment [31, 32]. It primarily interacts with soil bacteria, plant roots, and the soil matrix [33]. It also aids in nutrient retention and triggers a variety of biogeochemical processes. Currently, biochar is being used sparingly in India, mostly in villages and small towns. Promoting the biochar process in India would be more advantageous given its broad applicability.

7. In-situ management with mechanical intensification

Many farmers use in-situ application of crop residue because it is a natural process. This process also gives the soil certain advantages. There are two primary techniques for applying chemicals in the field, but both entail leaving crop residue on the fields after harvest. What occurs with tillage in the following season will determine how they differ. In the first approach, planting is done the next season with little to no tillage, whereas in the second way, crop residue is mechanically absorbed into the soil during plowing [34]. Both techniques require specialized (new) equipment, such as machinery for crop residue absorption into soils or no-till seeing equipment, even though in-situ management of agricultural residues can offer long-term cost savings on equipment and manpower. In North America, crop residue retention with no-tillage is primarily used, and in the United States alone, no-till farming accounts for about 40% of cropland [30]. In-situ management techniques such as direct incorporation into soils and mulching are specifically mentioned in the National Policy for Management of Crop Residue [13] as ones that should be promoted in India not only to control crop residue burning but also to prevent environmental degradation in the croplands.

8. Soil health and conservation agriculture

A soil must, among other things, have room for plant roots to spread out, be able to store and make water and nutrients available to plant roots, and offer a favorable biotic and chemical environment for soil microorganisms to function in order to maintain soil porosity, fix atmospheric nitrogen, hold, and mineralize nutrients. These factors must work in concert to create the foundation for the defined soil health.

With the help of beneficial symbiotic relationships with plant roots, such as those formed by nitrogen-fixing bacteria and mycorrhizal fungi, recycling vital plant nutrients, and improvements to soil structure (such as aggregate stability), which in turn improves soil water and nutrient holding capacity, healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect, and weed pests, and ultimately improve crop production. Many regions of the world agree that their soils are ill, unhealthy, and lacking in the ability to produce enough food for themselves. While “soil quality” is frequently mentioned as if it were a fixed quality, “soil health” is less frequently mentioned and refers specifically to the biological dynamics of soil quality.

• The following essential CA elements benefit soil in “good condition” (static) or “good health” (dynamic):

• Minimal disruption of the ideal porous soil architecture, which (a) maintains optimal levels of respiration gases in the rooting zone; (b) moderates oxidation of organic matter; (c) facilitates water movement, retention, and release at all scales; and (d) restricts re-exposure of weed seeds and their germination.

• The soil surface benefits from a permanent layer of sufficient organic matter, particularly crop residues, including: (a) protection from the harsh effects of solar radiation and rain; (b) a substrate for soil organism activity; (c) increased cation-exchange capacity for nutrient capture, retention, and slow release; and (d) weed smothering. Legumes included in crop rotations and sequences offer the following benefits:

• A range of species, for direct harvest and/or fodder; (a) minimal rates of pest species population build-up through life-cycle disruption; (b) biological N-fixation in suitable conditions, limiting external costs; (c) prolonged slow-release of such N from complex organic molecules derived from soil organisms; and (e) improvement of soil profile by organic matter addition at all depths.

According to the Ministry of New and Renewable Energy (MNRE 2009), the government of India, approximately 500 Mt. of crop residue is produced annually. Depending on the cropping intensity, productivity, and crops planted in various Indian states, there is a wide variation in crop residue generation and utilization. The most waste is produced in Uttar Pradesh (60 Mt), then in Punjab (51 Mt), and then in Maharashtra (46 Mt). Cereals provide 352 Mt. of leftovers from various crops, which is followed by fibers (66 Mt), oilseeds (29 Mt), pulses (13 Mt), and sugarcane (12 Mt). The cereal crops (rice, wheat, maize, and millets) account for 70% of crop residues, whereas the rice crop alone accounts for 34%. With 22% of the residues produced, wheat comes in second, while 13% of the residues produced by all crops come from fiber crops. Cotton produces the most fiber (53 Mt) and has an 11% crop residual rate. Coconut comes in second among fiber crops for residue generation with 12 Mt. In India, crop residues made up of tops and leaves from sugarcane production total 12 Mt., or 2% of all crop residues.

The excess leftovers, or those that were generated but not used for other purposes, are often burned in the field or used to power homes. India’s estimated annual crop residual surplus ranges from 84 to 141 Mt., with grains and fiber crops accounting for 58 and 23%, respectively, of the total. The remaining 19% comes from various crops, sugarcane, legumes, and oilseeds. Out of the 82 Mt. of excess cereal crop residues, 44 Mt. are leftover rice, followed by 24.5 Mt. of wheat, which is primarily burned in fields. An estimated 80% of the extra residue from fiber crops (33 Mt) is cotton, and this residue is burned.

9. Remainders’ positive influence on soil health

Crop residues can have a number of beneficial effects on the physical, chemical, and biological aspects of soil, whether they are incorporated into the soil or are left on the surface. By changing the soil’s structure and aggregate stability, it lowers the bulk density of the soil and increases hydraulic conductivity. Plant residue mulching increases the minimum soil temperature in winter owing to a decrease in the upward heat flux from the soil and lowers the minimum soil temperature in summer due to the shade effect. Crop residues that are kept on the soil’s surface slow runoff by acting as miniscule dams, prevent the formation of surface crusts, and improve infiltration. When left unaltered with no-till, the channels (macro-pores) made by earthworms and old plant roots enhance infiltration to aid in reducing or eliminating runoff. A higher level of soil moisture can, in many cropping and climatic settings, lead to a higher crop yield when combined with decreased water evaporation from the top few inches of soil and improved soil properties.

Residues serve as a store for plant nutrients, stop nutrient leaching, boost cation exchange capacity (CEC), offer a hospitable environment for biological N fixation, boost microbial biomass, and improve the activities of enzymes such as dehydrogenase and alkaline phosphatase. Increased microbial biomass can improve soil nutrient availability and serve as a source and sink of nutrients for plants. The reduction of wind and water erosion, the improvement of water infiltration and moisture retention, and the reduction of surface sediment and water runoff are all benefits of leaving significant amounts of crop residues equally dispersed across the soil surface. Crop residues are crucial in reducing soil acidity by releasing hydroxyls, especially during the breakdown of residues with higher C:N ratios, and in increasing soil alkalinity by applying residues with lower C:N ratios.crops including legumes: oilseeds and pulses. Crop residues’ contribution to soil carbon sequestration would be a bonus in terms of managing the effects of climate change.

10. Use of residues in conservation agriculture is subject to restrictions

With greater residue levels in Conservation Agriculture, there are a number of difficulties (CA). These include issues with various diseases, insects, or weeds as well as challenges caused by increased surface residues to effective seed, fertilizer, and pesticide placement. With their greater amounts of crop residue, conservation tillage approaches typically demand more care, timing, placement of nutrients and pesticides, and tillage operations. Due to increasing residue levels and fewer options for the manner and timing of nutrient administrations, nutrient management may become problematic. In instance, no-till can make it more difficult to apply manure and may cause nutrient stratification in the soil profile as a result of repeated surface treatments without any mechanical assimilation.

Placement of seed at the right depth to promote germination in the no-tilled plots with residue kept on the soil surface is still a challenge and is one of the major technological bottlenecks that requires attention. Although the zero-till seed-cum-fertilizer drill machinery has undergone significant progress, there is still more room for advancement to provide farmers with a hassle-free technology. The other bottleneck, particularly in the rice-wheat system, is weed control. Given that chemical herbicides can leak into the environment, overuse of them may not be ideal. All fertilizers, notably N, should not be applied as a base dose at the time of planting because doing so could reduce their effectiveness and pollute the environment. Although evaporation is decreased and more water is kept close to the top with greater residue levels, this stimulates the establishment of feeder roots close to the surface where the nutrients are concentrated. Higher expenditures may occasionally result from additional application of particular nutrients and the need for specialized equipment for efficient fertilizer placement. Similar to how higher pesticide use may be required for CA adoption. The problem of non-point source pollution and environmental hazard is already present in the nations that use proportionally more herbicides.

• Additional management skill requirements, concerns about poorer crop yields and/or economic returns, unfavorable attitudes or views, and institutional restrictions are additional barriers to farmers adopting residue integration systems. Farmers and occasionally entire communities show a great preference for well-kept tilled fields. They take great satisfaction in keeping their fields “clean” of debris and actively tilling them to create a flat surface before planting.

• Other applications for crop leftovers

• There are a number of strategies that can be used to handle residues effectively. Large quantities of wastes can be utilized for compost preparation, energy production, the creation of biofuel, and mushroom culture in addition to being used as cattle feed.

By utilizing the leftovers as animal bedding and subsequently piling them in a dung pit, the wastes can be composted. A kilogram of straw can hold up to 2–3 kilogram of animal excreted pee. On the farm itself, material can also be composted using various techniques. One hectare’s worth of rice leftover produces 3.2 tonnes of nutrient-rich farmyard manure (FYM).

11. Biomass energy from crop waste

Because of its benefits for the environment, biomass is a source of energy that can be used effectively and is sought for on a global scale. Crop residue is now being used more frequently to produce energy and to replace fossil fuels in recent years.

Additionally, it provides a quick fix for lowering the atmospheric CO₂ concentration. Biomass is a storable resource that is less expensive, more energy-efficient, and environmentally friendlier than other renewable energy sources such as solar and wind energy. Straw, however, has a low bulk density and a low energy output on a weight basis. Regardless of the bio-energy technology, the logistics of delivering the vast quantities of straw needed for efficient energy generation is a significant economic factor. The capacity to use residues for energy generation is influenced by a number of factors, including the availability of residues, the cost of transportation, and the infrastructure (such as harvesting equipment and collection methods).

12. Ethanol produced from crop waste

Because ethanol can be used as a pure fuel in internal combustion engines or combined with gasoline as a fuel extender and octane-enhancing agent, the conversion of ligno-cellulosic biomass into bio-based alcohol production is a significant and researchable subject. Theoretical estimates of the amount of ethanol that may be produced from various feedstocks, including maize grain, wheat straw, rice straw, bagasse, and sawdust, range from 382 to 471 L t⁻¹ of dry matter.

13. Biomethanation

Biogas, a gaseous mixture of carbon dioxide and methane, can be produced from biomass, such as rice straw, and used as fuel. It has been claimed that dry rice straw may produce 300 m³ t⁻¹ of biogas. The procedure produces good-quality gas with a methane content of 55–60%, and the spent slurry can be used as manure. This approach aims to produce manure that may be returned into the soil while also using agricultural waste to extract high-quality fuel gas.

14. Gasification of waste

Gas is created during the thermochemical process of gasification when wastes partially burn. After early pyrolysis, the process thoroughly decomposes the biomass to produce energy-rich gaseous products. The primary issue in using biomass gasification to produce electricity is purifying the gas to get rid of pollutants. The residues can be put to use in gasifiers to create producer gas. In some states, gasifiers with a capacity of more than 1 MW have been erected to produce producer gas, which is fed to motors connected to alternators to produce power. About 300 kWh of power may be produced from 1 tonne of biomass.

15. Fast pyrolysis

In order to quickly pyrolyze crop leftovers, the biomass must quickly reach a temperature of 400–500°C. This causes a striking modification in the thermal disintegration process. A biomass’s dry weight is transformed into condensable vapors to the tune of about 75%. The condensate produces a dark brown, viscous liquid known as bio-oil if it cools down quickly within a few seconds. Bio-oil has a calorific value that ranges from 16 to 20 MJ kg⁻¹.

16. Biochar

Biochar is a high-carbon substance made from biomass that has been slowly heated without oxygen. It has benefits in terms of its effectiveness as an energy source, its usage as a fertilizer when combined with soil, and its capacity to stabilize and lower atmospheric emissions of hazardous gases. Biochar is useful for releasing gases that are high in energy, which are subsequently used to create liquid fuels or directly to generate electricity and/or heat. It might have a significant impact on the long-term storage of carbon. Biochar improves the soil’s fertility and capacity to hold onto water, as well as speeding up the transport of minerals to plant roots.

17. Elements of a nutrient management strategy in CA

Components of a nutrient management plan in California

As an agro-ecological technique with a biological foundation, CA does not concentrate on a specific product or species. Instead, it deals with the intricate relationships between various crops and specific local conditions, capitalizing on the intricate networks of relationships involved in managing soil systems in a profitable and sustainable manner.

The following four general aspects would need to be taken into account by nutrient management techniques in CA systems:

1. The biological processes of the soil are strengthened and safeguarded to provide all soil biota and microorganisms preference and to increase and maintain soil organic matter and soil porosity;

2. Enough biomass is produced and biological nitrogen is fixed to maintain enough soil energy and nutrient stores.

3. The production of biomass and biological nitrogen fixation is sufficient to maintain the energy and nutrient levels in the soil necessary to support higher levels of biological activity and to cover the soil;

4. Plant roots in the soil have sufficient access to all nutrients from both natural and artificial sources to meet crop needs; and.

5. The pH of the soil is maintained within an appropriate range to ensure that all important soil chemical and biological processes run smoothly.

18. Managing soil biological processes: the living system that is soil

Water must enter soil that is permeable from the surface below in order for rivers, plants, and groundwater to function. The interaction between the biological, physical, and chemical aspects of soil productivity is hampered by a lack of water for plants. The volume and interconnectedness of soil pores, which in turn control their ability to transfer water, determine the rate at which water enters, passes through, and moves through the soil.

The percentage of soil pores that can hold water against gravity and still release it in reaction to “suction” produced by roots, as defined by the physiology of the plants and atmospheric demand, determines the volume and availability of water that plants may use. Nutrient management and water management in soil are inextricably related.

The productivity of the soil in which plants are growing is reduced due to a lack of water and/or other nutrients, which prevents the complete interaction of the plant and soil systems. Plant growth and development are hampered by inadequate plant nutrients, and a severe water shortage brings the system to a complete stop.

Due to degradation and loss of organic matter, soil porosity is compromised or eliminated through compaction, pulverization, and/or collapse.

Due to the deterioration and loss of organic matter, compaction, pulverization, and/or collapse harm or destroy soil porosity. Tillage of the soil causes a rapid oxidation of the organic carbon in the materials to carbon dioxide gas and its loss to the environment, resulting in a net loss of organic matter. After such damage, the nonliving portion of organic matter is biologically transformed by its living component, the fauna and flora that live the soil, ranging from microorganisms such as bacteria to macroorganisms such as worms, termites, and the plants themselves. The creation of irregular aggregates of soil particles, within and between which are the crucial pore-spaces in soil, is facilitated by their metabolic activity, which also produces glue-like compounds, fungal hyphen, etc. The production of irregular aggregates of soil particles, within and between, which are the vital pore-spaces in which water, oxygen, and carbon dioxide move and roots grow, is a result of their metabolic activity, which also contributes glue-like compounds, fungal filaments, etc. Additionally, these elements significantly increase the soil’s ability to grab and hold onto nutrient ions on organic complexes and provide a slow-release mechanism for their release back into the soil’s moisture. A significant amount of fresh organic matter must constantly be present in the soil as a source of energy and nutrients for soil organisms, not simply for the plants alone, in order for this activity and its effects to cease. If the conditions for biotic activity in the soil are kept favorable, this dynamic process of formation and reformation of the porous soil architecture will continue from year to year, maintaining the capacities of landscapes thus treated to continue yielding vegetation and water on a regular basis, contributing to the sustainability of such production processes.

This is where maintaining “soil health” becomes important. It is more appropriate to think of the soil as primarily a living, porous biological entity that penetrates the nonliving components and forms from the top downward, rather than as a geological entity that forms from the bottom upwards with living things in it at the top, when deciding how to manage the land and nutrients to maintain its productivity [25].

19. Government intervention

The engagement of the right government agencies is required to implement strict measures to reduce crop burning and better control crop waste management. The Indian government has made several attempts to introduce and educate the agricultural community about best practices. Environmentalists and government officials have also developed ideas to reduce crop residue burning and encourage the use of alternative sustainable management techniques. The National Environment Appellate Authority Act of 1997, the Air Prevention and Control of Pollution Act of 1981, the Environment Protection Act of 1986, the National Tribunal Act of 1995, and Section 144 of the Civil Procedure Code (CPC) are a few of the laws relating to crop residue burning that are currently in effect. The National Green Tribunal (NGT) has implemented strict regulations, particularly in the states of Rajasthan, Uttar Pradesh, Haryana, and Punjab, to reduce crop residue burning [13, 35].

20. National schemes and policies

The National Thermal Power Corporation (NTPC) has lately been instructed by the Indian government to combine crop residue pellets (almost 10%) with coal for the purpose of generating electricity [36]. The farmers benefited from a financial return of about Rs. 5500 (77 USD) per tonne of agricultural leftovers as a result. These profitable techniques have not yet been implemented, but farmers might profitably take advantage of them. The Indian government only operates a few bio-composting-related measures. As a part of its 11th Five Year Plan, the Indian government announced the Rashtriya Krishi Vikas Yogna (RKVY), State Plan Scheme of Additional Central Assistance, in August 2007 (Table 1) [35].

Query	Response	Crop residues management options
1. Can crop residues be used for conservation agriculture?	Yes	Retain it on soil surface Use drill for sowing with residues (e.g. Happy Seeder)
If the answer is; No, move to query 2		Follow conservation agriculture for all crops in rotation
2. Can it be used as fodder?	Yes	Leave stubbles in field Enrich fodder with
If the answer is; No, move to query 3		supplements; (e.g. urea and molasses); Use manure in conservation agriculture
3. Can it be used for biogas generation?	Yes	Leave stubbles in field Adopt community biogas
If the answer is; No, move to query 4		plant (e.g. KVIC design modified by IARI); Use slurry in conservation agriculture
Query	Response	Crop residues management options
4. Can it be used for composting?	Yes	Leave stubbles in field Adopt modern composting technique (e.g. IARI model)
If the answer is; No, move to query 5		Use compost in conservation agriculture
5. Can it be used for bio-fuel generation?	Yes	Leave stubbles in field Install bio-fuel plant Use liquid slurry in conservation agriculture
If the answer is No, move to query 6
6. Can it be used for electricity generation?	Yes	Leave stubbles in field Install biomass-energy plant (e.g. KPTL model)
If the answer is; No, move to query 7		Use ash in conservation agriculture
7. Can it be used for gasification?	Yes	Leave stubbles in field Install biomass gasifier (e.g. CIAE model)
If the answer is; No, move to query 8		Use ash in conservation agriculture
8. Can it be used for biochar making?	Yes	Leave stubbles in field Install biochar klin (e.g. IARI model) Use biochar in conservation agriculture

Table 1.

Model plan for managing crop residues at local and regional scales.

The Indian Ministry of Agriculture recently created a National Policy for Management of Crop Residue (NPMCR) [7] in addition to the aforementioned. The NPMCR’s primary goals are listed below [6]:

1. To reduce the loss of important soil nutrients and to increase the variety of uses for crop residue in industrial applications, promote technology for the best usage and in-situ management of crop residue.

2. Create and encourage the use of suitable crop machinery in agricultural techniques, such as the modification of grain recovery equipment (harvesters with twin cutters to cut the straw). Offer discounts and incentives to encourage the purchase of mechanical sowing equipment such as baling, shredding, and turbo seeders.

3. Work with the National Remote Sensing Agency (NRSA) and the Central Pollution Control Board to monitor agricultural residue management using satellite-based remote sensing technologies (CPCB).

4. Raise money for creative ideas and project proposals using a multidisciplinary approach and fund raising in several ministries.

21. Summary and conclusions

Crop residues are one type of agricultural waste that has presented unique issues because of its enormous volume and lack of management tools. Given that rice and wheat, which typically provide the majority of crop leftover, are the main staples of India, it is apparent that the extensive cultivation of these crops to feed the continuously growing population has resulted in the development of significant amounts of crop residue. India produces 500 Mt. of crop residue annually on average. There is a massive surplus of 140 Mt., out of which 92 Mt. is burned annually, primarily in the northern states such as Punjab, Haryana, and Uttar Pradesh, even though the majority of it is used as fodder, a raw material for energy production, etc. Due to a lack of technical knowledge and appropriate disposal options, small-scale farmers in particular turn to burning crop waste as a cheap alternative. Crop burning on a large scale raises atmospheric CO₂, CO, N₂O, and NOx levels and has caused an alarming rise in air pollution. The air quality in northern India terrifyingly deteriorated, reaching nearly double the allowable Indian threshold and 10 times the WHO standard.

The Indian government has launched numerous programs in an effort to address the issue of crop residue burning. The Indian Ministry of New and Renewable Energy (MNRE) and the Indian Agricultural Research Institute (IARI) are constantly encouraging research and cutting-edge techniques to handle crop waste without burning. Recently developed by the Central Government, the National policy for management of crop residue (NPMCR) outlines laws and regulations that local agencies must follow to address crop burning and promote sustainable management practices. Continued air pollution, particularly in November and December, suggests that the aforementioned restrictions have not effectively stopped crop burning. The true causes of the burning of crop residue are more socioeconomic in nature than agricultural or waste management related. In its place, sustainable alternatives that entail techniques to feed the nutrients in the crop residue back into the same crop areas have been developed. Uncommonly used bio-based products for agricultural waste usage include biogas, charcoal, and in-situ management with mechanical intensification. Composting rules could be developed for rural regions and applied to all farms by farmers associations. Crop residue can be significantly reduced by mechanizing the harvesting process, and farmers may receive equipment subsidies from local authorities. This gap should be filled by the local government, municipality, or farmers’ organization, which should also start local assistance programs such as equipment rentals, waste transportation, and possibly linking waste to areas where it can be used as raw materials. Educating the farming community and providing them with socioeconomic and technical support. They must to be informed of the benefits of lower agrochemical costs owing to the use of compost and the additional income they can get from other types of recovery initiatives, such energy production.