Contents lists available at ScienceDirect Environmental Research journal homepage: www.elsevier.com/locate/envres Valorization of underutilized waste biomass from invasive species to produce biochar for energy and other value-added applications Ashfaq Ahmed a,b,c , Muhammad S. Abu Bakar a , Rasyidah Hamdani a , Young-Kwon Park b,* , Su Shiung Lam d , Rahayu S. Sukri e , Murid Hussain c , Khaliq Majeed c , Neeranuch Phusunti f , Farrukh Jamil c , Muhammad Aslam c a Faculty of Integrated Technologies, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Brunei Darussalam b School of Environmental Engineering, University of Seoul, Seoul, 02504, Republic of Korea c Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus Raiwind Road, Lahore, 54000, Pakistan d Pyrolysis Technology Research Group, Institute of Tropical Aquaculture and Fisheries (Akuatrop), Universiti Malaysia Terengganu, 21030, Kuala Terengganu, Terengganu, Malaysia e Environmental and Life Sciences Programme, Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE 1410, Brunei Darussalam f Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand ARTICLE INFO Keywords: Underutilized biomass Biofuels Pyrolysis Biochar Invasive species Value-added products ABSTRACT Biochar production from invasive species biomass discarded as waste was studied in a fixed bed reactor pyrolysis system under different temperature conditions for value-added applications. Prior to pyrolysis, the biomass feedstock was characterized by proximate, ultimate, and heating value analyses, while the biomass decom- position behavior was examined by thermogravimetric analysis. The heating values of the feedstock biomass ranged from 18.65 to 20.65 MJ/kg, whereas the volatile matter, fixed carbon, and ash content were 61.54–72.04 wt %, 19.27–26.61 wt % and 1.51–1.86 wt %, respectively. The elemental composition of carbon, hydrogen, and oxygen in the samples was reported to be in the range of 47.41–48.47 wt %, 5.50–5.88 wt % and 46.10–45.18 wt %, respectively, while the nitrogen and sulphur content in the biomass samples were at very low concentrations, making it more useful for valorization from environmental aspects. The biochar yields were reported in the range of 45.36–58.35 wt %, 28.63–44.38 wt % and 22.68–29.42 wt % at a pyrolysis temperature of 400 °C, 500 °C, and 600 °C, respectively. The biochars were characterized from ultimate analysis, heating value, energy densification ratio, energy yield, pH, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy and energy dispersive X-ray spectrometry (SEM and EDX), to evaluate their potential for value-added applications. The carbon content, heating value, energy densification ratio, and the porosity of the biochars improved with the increase in pyrolysis temperature, while the energy yield, hydrogen, oxygen, and nitrogen content of the biochars decreased. This study revealed the potential of the valorization of underutilized discarded biomass of invasive species via a pyrolysis process to produce biochar for value-added applications. 1. Introduction Energy is a basic commodity and is very important for the sustain- ability of modern society. The ever-increasing energy needs and the consequent increasing consumption of fossil fuels have resulted in the release of more greenhouse gases and volatile organic compounds into the atmosphere, resulting in environmental pollution. The requirements for energy are increasing as the population and economic activities of the world are increasing (H. Lee et al., 2020). Consequently, secure and accessible supplies of energy are needed to ensure the growth and socio- economic activities of modern era (Patel and Shah, 2015). Fossil fuel resources are depleting every day, and their combustion is leading to major issues, such as global warming and threats to human health, along with the fluctuations in demand and supply, as well as the geopolitical issues that continually fluctuate the prices of the fuels. These issues have disturbed the economy-related calculations of coun- tries and prompted the search for unconventional renewable energy to ensure the sustainable, low cost and environmentally friendly supplies of energy (Aberilla et al., 2019; Lam et al., 2019c). In the given situation, biomass is a promising renewable energy resource that might contribute to energy production (Ahmed et al., 2017; Shen et al., 2015). Compared to fossil fuels, biomass is considered https://doi.org/10.1016/j.envres.2020.109596 Received 28 February 2020; Received in revised form 23 April 2020; Accepted 24 April 2020 * Corresponding author. E-mail address: catalica@uos.ac.kr (Y.-K. Park). Environmental Research 186 (2020) 109596 Available online 25 April 2020 0013-9351/ © 2020 Elsevier Inc. All rights reserved. T