energies Review Crop Residue Management in India: Stubble Burning vs. Other Utilizations including Bioenergy Gaurav Kumar Porichha 1,*, Yulin Hu 2, Kasanneni Tirumala Venkateswara Rao 1 and Chunbao Charles Xu 1,* 1 Department of Chemical and Biochemical Engineering, Western University, London, ON N6A 5B9, Canada; [email protected] 2 Faculty of Sustainable Design Engineering, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada; [email protected] * Correspondence: [email protected] (G.K.P.); [email protected] (C.C.X.) Abstract: In recent studies, various reports reveal that stubble burning of crop residues in India generates nearly 150 million tons of carbon dioxide (CO2), more than 9 million tons of carbon monoxide (CO), a quarter-million tons of sulphur oxides (SOX), 1 million tons of particulate matter and more than half a million tons of black carbon. These contribute directly to environmental pollution, as well as the haze in the Indian capital, New Delhi, and the diminishing glaciers of the Himalayas. Although stubble burning crop residue is a crime under Section 188 of the Indian Penal Code (IPC) and the Air and Pollution Control Act (APCA) of 1981, a lack of implementation of these government acts has been witnessed across the country. Instead of burning, crop residues can be utilized in various alternative ways, including use as cattle feed, compost with manure, rural roofing, bioenergy, beverage production, packaging materials, wood, paper, and bioethanol, etc. This review article aims to present the current status of stubble-burning practices for disposal of crop residues in India and discuss several alternative methods for valorization of crop residues. Overall, this review Citation: Porichha, G.K.; Hu, Y.; article offers a solid understanding of the negative impacts of mismanagement of the crop residues Rao, K.T.V.; Xu, C.C. Crop Residue via stubble burning in India and the other more promising management approaches including use Management in India: Stubble for bioenergy, which, if widely employed, could not only reduce the environmental impacts of crop Burning vs. Other Utilizations residue management, but generate additional value for the agricultural sector globally. including Bioenergy. Energies 2021, 14, 4281. https://doi.org/10.3390/ Keywords: agricultural residue; stubble burning; alternative management practices; valorization en14144281 Academic Editor: Idiano D'Adamo 1. Introduction Received: 31 May 2021 Stubble burning is a practice where fire is purposely put to the stubble which remains Accepted: 8 July 2021 Published: 15 July 2021 after grains, such as paddy, wheat, rice, corn, etc., have been harvested. This represents an important source of atmospheric aerosol and gas emissions, hence having a potential effect Publisher’s Note: MDPI stays neutral on the global air quality and environmental chemistry. Open-field biomass burning is a with regard to jurisdictional claims in longstanding method for land clearing and improvements in land use to dispose of living published maps and institutional affil- and dead vegetation, used globally. It has been estimated that humans account for nearly iations. 90% of biomass combustion, although only a small portion of natural fires are responsible for the overall amount of vegetation burnt [1]. Over the past few decades, biomass burning has increased worldwide. In India alone, the total amount of crop residue and the burnt was estimated to be 516 million tones and 116 million tonnes (Mt), respectively, in the year of 2017–2018, approximately generating 176.1 Mt CO , 10 Mt of CO, 0.31 Mt CH , Copyright: © 2021 by the authors. 2 4 Licensee MDPI, Basel, Switzerland. 0.008 Mt N2O, 0.151 Mt NH3, 0.814 Mt NMVOC, 0.453 Mt PM2.5 (particulate matter) and This article is an open access article 0.936 Mt PM10 [2]. Stubble burning has many environmental impacts and consequences, distributed under the terms and compared with alternatives such as ploughing stubble back in the field or harvesting them conditions of the Creative Commons for industrial purposes. However, there are inadequate data on the impacts of crop stubble Attribution (CC BY) license (https:// burning. Extrapolation has been commonly used in estimating the pollution factors in the creativecommons.org/licenses/by/ database of farm residues, which may result in high uncertainty in the emission figures. It 4.0/). is well known that, due to agricultural field burning during the harvest season, air quality Energies 2021, 14, 4281. https://doi.org/10.3390/en14144281 https://www.mdpi.com/journal/energies Energies 2021, 14, x FOR PEER REVIEW 2 of 17 Energies 2021, 14, 4281 of crop stubble burning. Extrapolation has been commonly used in estimating the pollu-2 of 17 tion factors in the database of farm residues, which may result in high uncertainty in the emission figures. It is well known that, due to agricultural field burning during the harvest season,is greatly air affected.quality is Aerosolgreatly affected. and gaseous Aerosol pollutant and gaseous source pollutant profiles fromsource an profiles agricultural from anfire agricultural are needed fire to assessare needed their to contribution assess their tocontribution ambient air to quality. ambient As air described quality. As above, de- scribedagricultural above, field agricultural burning hasfield created burning many has environmentalcreated many environmental problems, utilizations problems, of croputi- lizationsresidues of for crop such residues as cattle for feed, such compost as cattle with feed, manure, compost rural with roofing, manure, biomass rural fuel, roofing, beverage bi- omassproduction, fuel, beverage packaging production materials,, packaging wood, paper, materials, and bioethanol, wood, paper, etc., and should bioethanol, be explored etc., shouldand promoted. be explored In theand following promoted. sections, In the following the detrimental sections, environmental the detrimental impacts environmen- of open talburning impacts of of the open agricultural burning of residues the agricultural are discussed residues in are detail discussed and current in detail approaches and current for approachesmanaging thesefor managing crop residues these are crop also residues presented. are also presented. ThisThis paper paper aims aims to to present present an an overview overview of of the the practice practice of of stubble stubble burning burning of of crop crop residuesresidues in in India, India, its its effects effects on on the the environm environmentent and and health, health, and and discuss discuss some some alternatives alternatives toto stubble stubble burning burning for for valorization valorization of of crop crop residues. residues. 2.2. Practices Practices in in India India IndiaIndia is is aa farmingfarming nation nation with with many many farming farming practices practices in step in step with with agro-climatic agro-climatic zones. zones.Rice, paddyRice, paddy and wheat and wheat cropping cropping patterns patterns are among are among the extensive the extensive farming farming practices prac- in ticesthe statesin the ofstates Haryana, of Haryana, Punjab, Punjab, Rajasthan, Rajasthan, and westernand western Uttar Uttar Pradesh. Pradesh. These These regions regions are arealso also infamous infamous for for burning burning the the straw straw and and stubble stubble after after the the harvestingharvesting season.season. The The state state PunjabPunjab crosses crosses India PakistaniPakistani borderborder and and is is also also called called a ‘breadbasket’ a ‘breadbasket’ because because it produces it pro- ducestwo-thirds two-thirds of India’s of India’s food grains.food grains. Even thoughEven though the government the government increasingly increasingly restricted re- strictedthe practice the practice after 1990s, after each1990s, year each in year late Septemberin late September and October, and October, farmers farmers from Punjab from Punjaband Haryana and Haryana in particular in particular burn an burn estimation an estimation of 35 million of 35 tons million of crop tons residue of crop from residue their frompaddy their fields paddy after fields harvesting after harvesting [3]. This practice [3]. Th servesis practice as a low-costserves as method a low-cost of getting method rid of of gettingthe straw rid andof the reduces straw theand turnaround reduces the time turnaround between time harvesting between and harvesting sowing for and the sowing second for(winter) the second crop. (winter) Figure1 crop. shows Figure the crop-wise1 shows the distributions crop-wise distributions of crop production, of crop produc- residue generated, and residue burnt in India for the year of 2018 [4]. tion, residue generated, and residue burnt in India for the year of 2018 [4]. FigureFigure 1. 1. Crop-wiseCrop-wise distributions distributions of of crop crop production, production, re residuesidue generated, generated, and and residue residue burnt burnt in in India India forfor the the year year 2018 2018 [4]. [4]. BurningBurning the the residue residue leads leads to to the the loss loss of of nu nutrientstrients and and resources. resources. Apart Apart from from deterio- deterio- ratingrating the the ambient ambient air air quality, quality, flaming flaming stubbles stubbles causes causes soil soil nutrient nutrient loss loss of of organic organic carbon carbon (3850(3850 million million kg), kg), nitrogen nitrogen (59 (59 million million kg), kg), phosphorus phosphorus (20 (20million million kg), kg), and andpotassium