sustainability Article Sustainable Management of Peanut Shell through Biochar and Its Application as Soil Ameliorant Aisha Nazir * , Um-e- Laila, Firdaus-e- Bareen, Erum Hameed and Muhammad Shafiq   Citation: Nazir, A.; Laila, U.-e.; Bareen, F.-e.; Hameed, E.; Shafiq, M. Sustainable Management of Peanut Shell through Biochar and Its Application as Soil Ameliorant. Sustainability 2021, 13, 13796. https://doi.org/10.3390/su132413796 Academic Editors: Keiji Jindo and Hans Langeveld Received: 26 October 2021 Accepted: 6 December 2021 Published: 14 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Environmental Biotechnology Laboratory (F4), Institute of Botany, University of the Punjab, Lahore 54590, Pakistan; ume.laila1012@gmail.com (U.-e.-L.); fbareen@gmail.com (F.-e.-B.); erumhameed401@gmail.com (E.H.); mshafiq.botany@pu.edu.pk (M.S.) * Correspondence: aisha.botany@pu.edu.pk; Tel.: +92-(300)-413-6566 Abstract: The current research encompasses utilization of peanut shells (PS) as feedstock for pyrolysis carried out at various temperatures (250, 400, and 550 ◦ C) for deriving biochar, namely PS-BC250, PS-BC400, and PS-BC550. After analyzing the biochar types physicochemically, it was applied as a soil ameliorant for the growth of cucumber. The results showed that in prepared biochar type, bulk density, volatile contents, hydrogen, oxygen, and nitrogen content decreased, whereas pH, electrical conductivity, ash content, fixed carbon content, and surface area increased with the increasing temperature. Scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) presented high porosity, re-orientation of vessels, and a greater number of aromatic compounds, respectively, for PS-BC prepared at 550 ◦ C. On applying PS-BC250, PS-BC400, and PS-BC550 as amendments in potted soil at 2, 4, and 6% (w/w), it improved soil quality (viz pH, EC e , BD, and soil water holding capacity) and increased the yield of cucumber. Because of improved soil properties and crop yield, PS-BC550 at the rate of 4% (w/w) demonstrated a great potential for agricultural application while provisioning dual circular economic indicators in the form of diverting PS waste to an effective alternative of chemical fertilizer having intensive carbon footprints in cucumber production. Keywords: peanut shell; biochar; pyrolysis temperature; soil ameliorants 1. Introduction Agricultural waste landfilling causes a wide range of environmental issues. The peanut processing sector contributes significantly to agro-industrial waste, primarily in the form of waste peanut shells [1]. It has been estimated that 28 million tonnes (Mt) of peanuts are produced annually. The peanut shell accounts for 25 to 30% weight of peanuts, resulting in 8 Mt of residual biomass in Asia alone [2]. Such residual biomass consists of great energy content that is worth exploring. Pyrolysis is one of the better options for the sustainable management of the voluminous quantity of peanut residual biomass [3]. Sustainable agricultural commodities emphasise not only crop productivity but also provides a better way for the management of agricultural waste, while maintaining soil health. Soil quality significantly influences the crop growth and is mainly affected by the widespread use of inorganic fertilizers. This has led to soil deterioration, a decrease in organic matter content, and ultimately a reduction in beneficial microbial diversity [4,5]. The inorganic fertilizer should be used less frequently, whereas organic amendment in the form of biochar can be used as a powerful tool for sustainable agricultural implication [6], as it has a prodigious potential to ameliorate the soil fertility and soil structure [7]. Biochar is recognized as a pyrolyzed carbon-rich substance, produced through the process of pyrolysis under an extremely limited provision of oxygen [8]. The biochar used as a soil amendment should have a great binding and water holding capacity and must not have detrimental consequences on the soil structure and soil fertility. The low bulk density and greater surface area enable it to retain the nutrients and water content, thereby Sustainability 2021, 13, 13796. https://doi.org/10.3390/su132413796 https://www.mdpi.com/journal/sustainability