Citation: Kumar, A.; Komandur, J.; Chaudhary, V.; Mohanty, K. Catalytic Co-Pyrolysis of Mesua ferrea L. De-Oiled Cake and Garlic Husk in the Presence of Red-Mud-Based Catalysts. Catalysts 2023, 13, 1401. https://doi.org/10.3390/ catal13111401 Academic Editors: Gartzen Lopez and Maite Artetxe Received: 12 August 2023 Revised: 12 October 2023 Accepted: 24 October 2023 Published: 28 October 2023 Copyright: © 2023 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/). catalysts Article Catalytic Co-Pyrolysis of Mesua ferrea L. De-Oiled Cake and Garlic Husk in the Presence of Red-Mud-Based Catalysts Abhishek Kumar, Janaki Komandur, Vasu Chaudhary and Kaustubha Mohanty * Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, India; abhishekk.cl@iitg.ac.in (A.K.); kjanaki@iitg.ac.in (J.K.); vasuchaudhary001@gmail.com (V.C.) * Correspondence: kmohanty@iitg.ac.in Abstract: Utilizing lignocellulosic biomass as a renewable energy source for the production of sustainable fuel is of paramount importance. This study focuses on the catalytic co-pyrolysis of Mesua ferrea L. de-oiled cake (MDC) and Garlic husk (GH) as potential feedstocks for bio-fuel production. The pyrolysis experiments were conducted using a semi-batch reactor under inert conditions at temperatures of 500, 550, and 600 ◦ C, with a heating rate of 10 ◦ C min -1 , a particle size below 1 mm, and an inert gas flow rate of 80 mL min -1 . The findings reveal that temperature significantly influences the yield of pyrolytic products. However, GC-MS analysis detected higher oxygenated compounds in the bio-oil, negatively impacting its heating value. To improve fuel quality, co-pyrolysis with and without a catalyst for a feedstock ratio of 1:1 w/w was performed. Red mud, an alkaline waste mainly composed of Fe 2 O 3 , Al 2 O 3 , and SiO 2 , is a hazardous environmental concern from aluminum production and is used as a catalyst. The red-mud catalysts reduced oxygen concentration and increased carbon content, acidity, and heating value in the pyrolytic oil. GC-MS analysis of the bio-oil confirmed that using catalysts combined with MDC and GH significantly decreased the concentration of acidic and aromatic compounds, thereby improving the pyrolytic oil’s higher heating value (HHV). Keywords: Mesua ferrea L. de-oiled cake; garlic husk; catalytic co-pyrolysis; red-mud; Ni/RM 1. Introduction The increase in demand for the world’s energy consumption is bringing focus to the dependence on the renewable energy sector. Fossil fuels contribute to over 80% of the world’s primary energy consumption. This leads to severe pollution of air, soil, and water [1]. Using biomass as a feedstock for producing renewable fuels and chemicals, particularly liquid fuels, shows tremendous energy security [2]. Pyrolysis is a method that can convert biomass into a liquid fuel known as bio-oil. This process has the potential to be both efficient and cost-effective. The different components of biomass, i.e., cellulose, hemicellulose, and lignin, decompose into various pyrolytic products, namely condensable gases (bio-oil), solid char, and non-condensable gases. Undesirable properties such as high acidity, low energy potential, and high-water content restrict the use of pyrolytic oil as a natural alternative to fossil fuel [3]. Co-pyrolysis is regarded as one of the most straightfor- ward strategies for successfully and efficiently utilizing a wide variety of feedstocks while only requiring the amount of energy that is required for each individual feedstock. Co- pyrolysis has the potential to utilize a sizable amount of waste as a raw material, resulting in the efficient handling of waste. Furthermore, co-pyrolysis has the potential to drastically reduce energy consumption, cost of production, and processing times. The heating value and pyrolytic liquid production are increased by co-pyrolyzing the biomass feed [4]. Some of the raw materials used in the production of biofuels include non-edible oil seeds (vegetable oil), wheat husk, algal biomass, de-oiled cake, waste products, etc. The production of biofuels from agricultural waste, including non-edible oil crops, has Catalysts 2023, 13, 1401. https://doi.org/10.3390/catal13111401 https://www.mdpi.com/journal/catalysts