BIOMASS CONVERSION INTO BIOFUELS AND HIGH-VALUE ADDED PRODUCTS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1021649
• Project Start Date: Nov 25, 2019
• Project End Date: Sep 30, 2024
• Program Code: [(N/A)]- (N/A)

Recipient Organization
AUBURN UNIVERSITY
108 M. WHITE SMITH HALL
AUBURN,AL 36849

Performing Department
Biosystems Engineering

Non Technical Summary
Our society is facing unprecedented challenges such as increasing uncertainty about global energy production and resources, high and fluctuating price of petroleum products, and growing scientific evidence that atmospheric carbon dioxide is among the most important contributors to extreme weathers and climate change. Therefore, it is critical to increase the renewable energy supply, and at the same time reduce worldwide greenhouse gas (GHG) emissions. These concerns have motivated researchers for long-term approaches to producing fuels, lubricants, materials and chemicals from biomass. The U.S. has a potential to provide over 1 billion dry tons of biomass annually. Forest and agricultural residues are the major biomass types but algae and sub-urban/urban wastes are also available for producing biofuels and biomaterials. Adhikari's group has been focused on producing biofuels from terrestrial and aquatic biomass using thermochemical approaches for last 11 years. For the next five years, Adhikari's group will focus on creating both biofuels and biomaterials from terrestrial biomass, sub-urban/urban wastes and algal biomass.

Animal Health Component

50%

Research Effort Categories

Basic

25%

Applied

50%

Developmental

25%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
402	0650	2020	100%

Knowledge Area
402 - Engineering Systems and Equipment;

Subject Of Investigation
0650 - Wood and wood products;

Field Of Science
2020 - Engineering;

Keywords

bioenergy

gasification

pyrolysis

liquefaction

animal wastes

Goals / Objectives
The long-term goal of this project is to develop biobased fuels and value-added products. Specifically, the project will focus on converting biomass (forest and agricultural residues, aquatic biomass) including lignin and municipal wastes into fuels via thermochemical conversion processes and creating high-value chemicals using various reaction schemes. The specific objectives of the projects are to: (i) characterize regionally available biomass for fuels and chemicals production; (ii) produce bio-crude via both pyrolysis and hydrothermal liquefaction; (iii) create biobased lubricants and fuels from bio-oils; (iv) produce syngas from biomass for fuels and chemicals; and (v) develop high-value materials from biomass and its components.

Project Methods
Task 1. Biomass Characterization: Biomass such as poultry litter, bio-solids, forest residues (twigs, bark and needles), algae and post-sorted MSW will be collected from local suppliers. A small amount of samples will be obtained and dried and ground using a hammer mill (1.58 mm or 1/16 inch screen) and then sieved through an 850 µm sieve for characterization. The selected biomass feedstocks will be analyzed in accordance with ASTM E870 for higher heating value (HHV), ISO562 for volatile combustible matter (VCM) and ash content, and ASTM E1755 and D3172 for ultimate analysis. Fixed carbon and oxygen contents will be calculated by difference as described in our previous work.Lignin samples will be either obtained from our industry collaborators or produced in our laboratory. Prior to the experiments, biomass will also be characterized for extractives, klason lignin, sugar profile, cellulose and hemicellulose [42-43]. Lignin samples will be produced using ethanol organosolv in our laboratory in addition to that obtained from industry collaborators. Lignin samples will be characterized as described in the published literature [44-49]. The characterization of lignin will include ultimate and proximate analyses, average molecular weight, phenol concentration, H/S/G ratio, OH concentrations (syringol, catechol, aliphatic, carboxylic, condensed phenolic), ether bonds and molecular weight. A number of analytical tools such as a thermogravimetric analyzer (TGA), gas chromatograph-mass spectrometer (GC/MS), Fourier Transform Infrared Spectroscopy (FTIR), Pyroprobe-GC/MS (Py-GC/MS), 13C, 31P and 1H Nuclear Magnetic Resonance (NMR) will be used for characterization. A detailed description of these methods is discussed in our publications [5051].Task 2. Solvolysis of Lignin of Chemicals Production: The overall goal of this task is to find out new and better strategies to depolymerize naturally found lignin biopolymer for production of novel sustainable chemical products. The first part will involve the use of three bio-based green solvents, p-cymene, R(+)limonene, and (-)α-pinene for the depolymerization of lignin model compounds and lignin samples. The lignin model compounds used will be vanillyl alcohol, benzyl phenyl ether, diphenylmethane, diphenyl ether, and Guaiacylglycerol-β-guaiacyl ether. The lignin samples used will involve Organosolv lignin (produced in our laboratory from pine), and two other lignins: Plantrose® lignin provided by Renmatix Inc. (Georgia, USA), and Dealkaline lignin procured from TCI Chemicals Ltd. (Oregon, USA). The lignin samples will be characterized using the Nuclear Magnetic Resonance (NMR) techniques. The products of lignin depolymerization will be analyzed with the help of gas-chromatography techniques. The reaction chemistry observed for model compounds will guide the further development of bond cleavage strategies that will be used for the actual lignin depolymerization.Task 3: Production of Activated Carbon from Biomass and its Components: Biomass or its components will be initially carbonized at 500 oC for 2 hours. The samples will be heated at 6 oC/min while purging with nitrogen gas. Carbonized samples will be chemically activated at 600, 700, and 800 oC in a fixed bed reactor. Briefly, a known amount of KOH (3 times the weight of oven dried biochar) will be dissolved in water (3 ml water for each 1 g KOH), the KOH solution will be added to the bio-char, and the mixture will be dried in a PTFE evaporator overnight at 105?C. Then the mixture will be placed in a quartz tube, heated to 375?C and held for 1 hour while purging with nitrogen. The mixture will be further heated up to 800 ?C and held at that temperature for 2 hours. The samples will be cooled to room temperature while flowing nitrogen gas. The mixture will be cleaned with 0.1M HCl and washed with distilled water until the pH becomes the same as the pH of distilled water. The washed samples will then be dried at 105 oC for 12 hours. The produced samples (activated carbon-ACs) will be characterized for the following properties. Physical properties including gas physisorption (BET surface area and porosity), scanning electron microscopy (SEM), and dynamic contact angle (for understanding the hydrophobicity). Chemical property analysis will include CHNS elemental analysis (atomic ratios of H/C, O/C, C/N, which are indicative of bonding arrangement and polarity), proximate analysis, cation exchange capacity (CEC), pH, electrical conductivity (EC), zeta potential, X-ray photoelectron spectroscopy (XPS) analysis (to quantify the surface functional groups), Boehm titration (to measure the surface acidic groups), and FT-IR analysis.Task 4: Production of 3D Printed Composites using Biomass and Its Components: Different percentage of biomass (or lignin) will be compounded with polymeric materials such as poly lactic acid (PLA) or other polymers and the mixture will be extruded using an extruder to make filaments for 3D printing. For this purpose, we will utilize an 18 mm Liestritz twin screw extruder equipped vacuum vents and single strand die with this machine. We will prepare blends of biomass (or lignin) with PLA or other polymers and then blends will be pelletized. DSC experiments will be performed on the blend in order to establish the melting temperature that will be used during the extrusion the filaments. A Wayne extrusion line with monofilament and multi-filament capabilities will be utilized to prepare the filaments that will be used in the 3D printing system.After the extrusion the samples will be thermoformed into different shapes for characterization. Tensile strength, modulus and elongation will be measured using a universal testing machine. Biomass/polymer interaction will be studied using microscopy. The mechanical properties across the temperature range will be measured using dynamic mechanical analysis (DMA). Finally, the filaments will be used in the 3D printing. 3D printer available at the Centre for Polymers and Advanced Composites at Auburn University will be used for printing several shapes to test the ability to create complex structures. 3D printed composites will be characterized for storage modulus (E') and loss modulus (E"). The results will elucidate the cohesivity of the network and the crosslink structure and rigidity of the material. The service temperature and the glass transition temperature (taken at the maximum of the tan d peak) will also be reported. The morphology of the product will be examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Uniaxial stress-strain response of the material under tensile loading or three point bending conditions will be studied during the project. This is critical for understanding the overall mechanical behavior of the networks, as well as for developing material models.

Progress 10/01/20 to 09/30/21

Outputs
Target Audience:During this period, the target audiences were mainly undergraduate, graduate students, and the scientific community interested in bioenergy and biofuels production and utilizing waste biomass and biochar that was produced from the thermochemical conversion process. The group also interacted with several companies working on bioenergy and waste utilization, where the research findings were highlighted. The results were shared through peer-reviewed journal articles and by presenting at two national meetings. Changes/Problems:The progress of our research group was hindered some due to the pandemic (COVID-19) and also the ability to recruit graduate students. What opportunities for training and professional development has the project provided?This project provided opportunities to learn research skills for undergraduate and graduate students and Post-docs. Undergraduate students learn about experimental design and data collection with accuracy. Graduate students learn analytical skills to characterize biomass, biofuels, and biochemical and also write manuscripts. Post-docs received training on mentoring undergraduate and graduate students, developing research proposals, and writing manuscripts. Graduate students and Post-docs also got opportunities to share their research findings in Biomass and Biofuel course taught by the investigator. How have the results been disseminated to communities of interest?Results were disseminated mainly through published peer-reviewed papers and presentations at national meetings. In some cases, research findings were also shared with industry stakeholders through targeted meetings. What do you plan to do during the next reporting period to accomplish the goals?Our focus is on producing biofuels and chemicals from biomass, agricultural wastes, and food wastes. We will continue exploring hydrothermal liquefaction of biomass and food waste for the production of liquid fuels and upgrading for transportation fuels. The work will focus on understanding the effect of process parameters, reaction mechanisms, and the role of heterogeneous catalysts on biocrude upgradability. Additionally, we have identified a handful of bio-char-based catalysts for the production of biofuels from Carinata oil and our initial results show encouraging data for hydrogen treatment of biocrude produced from liquefaction oil. We will continue to explore reaction mechanisms associated with those catalysts and test those catalysts for other feedstocks such as algae oil, municipal sludge, and waste cooking oil. Further, we will explore biobased resins produced from pyrolysis process for additive manufacturing.

Impacts
What was accomplished under these goals? The long-term goal of this project is to develop biobased fuels and value-added products. For the year 2021, the team focused on producing biofuels and bioproducts from municipal sludge, algae, carinata (non-food oil seed crop). The team also focused on utilizing biochar for removing phenolics from the aqueous phase of hydrothermal liquefaction process. Biolubricants from vegetable oils: The present research and development for lubricant production from vegetable oils rely on traditional (trans)esterification, etherification, and/or chemical modifications of triglycerides and free fatty acids (FFAs). However, the final products suffer from at least one of the following: poor low-temperature characteristics, low oxidation stability, low viscosity index, or poor solubility of additives. Our study presents a novel approach to produce biolubricants (BL) from the reaction of waste cooking oil (WCO) and cyclic oxygenated hydrocarbons (COHCs) (cyclopentanone, cyclopentanol, anisole, and 2-methylfuran) via a four-step pathway: hydrolysis, dehydration/ketonization, Friedel−Crafts (FC) acylation/alkylation, and hydrotreatment. Such reactions were successfully demonstrated using model compounds (oleic acid and stearic acid) and actual WCO feedstock. The process resulted in the production of novel BLs that were consisted of molecules with several mutual properties: (1) long and linear hydrocarbon chains, (2) low to zero unsaturation, (3) minimal branching, (4) naphthenic rings and cyclic structures, and (5) polar molecules. We showed that such BLs can be synthesized with pour-point, kinematic viscosity (at 40 °C), viscosity index, and Noack volatility of −12 °C, 47.5 cP, 186, and 17 wt %, respectively. Biofuels from carinata oil: In this work, we present the production of jet and diesel range hydrocarbons from non-edible hexane-extracted Brassica carinata oil. The influence of four heterogeneous catalysts (two noble metal catalysts: Pd/C and Ru/C, and two transition metal catalysts: Ni/C and Ni/SiO2-Al2O3) was investigated at 400 °C. The catalysts were characterized using XRD, Raman spectroscopy, TEM, SEM, TGA, TG-TPR, and BET specific surface area and pore size analyzer. The upgrading experiments consisted of three different approaches: 1) single-step cracking (1-C), 2) single-step simultaneous cracking, and hydrotreatment (1-C⋅H), and 3) a two-step process of cracking followed by hydrotreatment (2-C⋅H). Reaction products were characterized using different instruments and metrics: GC-FID, GC-MS, simulated distillation, CHNS-O elemental analyzer, viscometer, higher heating value (HHV), and total acid number (TAN). The 2-C⋅H process produced the highest amounts of desired hydrocarbons. The highest liquid yield of 81% with HHV of 47 MJ/kg was obtained with the use of Ni/SiO2-Al2O3 catalyst. All catalysts appeared to be regenerable after partial deactivation. Model compound studies were performed using erucic acid that accounted for about 40% of carinata oil FFA (free fatty acid) profile. Reaction pathways were proposed according to the chemical analysis of the products. Biocrude from sludge: In this study, ethylene and nitrogen(inert) reaction environments were applied into the hydrothermal liquefaction (HTL) process of municipal sewage sludge with red mud catalyst to evaluate the effects on biocrude and other byproducts. Red mud in three oxidation states was used: red mud calcined at 575 °C (CRM), reduced at 500 °C (RRM500), and 700 °C (RRM700). The RRM500 lowered the acidity by 14%; whereas, the RRM700 minimized the viscosity by 47% comparing to non-catalytic-inert biocrude samples. The ethylene ambience successfully maximized the biocrude yield by 41.6 wt% without any catalyst. The viscosity of the biocrudes produced under ethylene environment showed lower differences compared to nitrogen environment. The RRM500-ethylene reaction efficiently reduced the nitrogen content in the biocrude by 14%. These results suggested that the ethylene atmosphere has the potential for improved biocrude production during catalytic HTL treatment. Energy recovery from the aqueous phase: Hydrothermal liquefaction is a promising method to convert municipal sludge into an energy-dense fuel. The inevitable by-product aqueous phase is rich in complex organics, which has the potential for energy and nutrient recovery and can be treated by anaerobic digestion to produce methane. However, toxic compounds such as ammonia and phenolics present would inhibit the function of micro-organisms. This study investigated the influence of ammonia and phenolics removal on anaerobic digestion. The results showed that the treated aqueous phase resulted in up to 225 ml CH4/g COD. The highest methane production was obtained in the culture with both ammonia and phenolics removal at pH 7.0, which was about 90% higher than only ammonia removal and seven times higher than only phenolics removal. The microbial community analysis results showed that these two treatments could increase microbial diversity and upregulate the relative abundance of methanogens.

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Sanjita Wasti, Eldon Triggs, Ramsis Farag, Maria Auad, Sushil Adhikari, Dilpreet Bajwa, Mi Li, Arthur J Ragauskas. 2021. Influence of plasticizers on thermal and mechanical properties of biocomposite filaments made from lignin and polylactic acid for 3D printing. Composites B. Vol. 205. pg. 108483.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Ravishankar Mahadevan, Sushi Adhikari, Rajdeep Shakya and Oladiran Fasina. 2021. Influence of biomass inorganics on the functionality of H+ZSM-5 catalyst during in-situ catalytic fast pyrolysis. Catalysts, Vol. 11, pg. 124.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Hossein Jahromi, Sushil Adhikari, Poulami Roy, Ehsan Hassani, Conner Pope, Tae-Sik Oh and Yubaraj Karki. 2021. Production of green transportation fuels from Brassica carinata oil: A comparative study of noble and transition metal catalysts. Fuel Processing Technology, Vol. 215. Pg. 106737.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Pixiang Wang, Yuriy Sakhno, Sushil Adhikari, Haixin Peng, Deb Jaisi, Temitope Soneye*, Brendan Higgins, Qichen Wang. 2021. Effect of ammonia removal and biochar detoxification on anaerobic digestion of aqueous phase from municipal sludge hydrothermal liquefaction. Bioresource Technology. Vol. 326. Pg. 124730.
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Tawsif Rahman, Hossein Jahromi, Poulami Roy, Sushil Adhikari, Ehsan Hassan, Tae-Sik Oh. 2021. Hydrothermal liquefaction of municipal sewage sludge: Effect of red mud catalyst in ethylene and inert ambiences. Energy Conversion and Management. Volume 245, pg. 114615.
• Type: Journal Articles Status: Published Year Published: 2022 Citation: Pixiang Wang, Sarah Tyndall, Tawsif Rahman, Poulami Roy, Hossein Jahromi, Sushil Adhikari, Melissa Boersma. 2022. Sorption and recovery of phenolic compounds from aqueous phase from sewage sludge hydrothermal liquefaction using bio-char. Chemsphere. https://doi.org/10.1016/j.chemosphere.2021.131934
• Type: Journal Articles Status: Published Year Published: 2021 Citation: Hossein Jahromi, Sushil Adhikari, Poulami Roy, Madison Shelley, Ehsan Hassani, Tae-Sik Oh. 2021. Synthesis of novel bio-lubricants from waste cooking oil and cyclic oxygenates through an integrated catalytic process. ACS Sustainable Chemistry & Engineering. Vol. 9 (21). pg. 13424-13437.

Progress 11/25/19 to 09/30/20

Outputs
Target Audience:During this period, the target audiences were mainly undergraduate, graduate students, and the scientific community interested in bioenergy and biofuels production and utilizing bio-char that was produced from the thermochemical conversion process. The group also interacted with several companies working on bioenergy and waste utilization, where the research findings were highlighted. The results were shared through peer-reviewed journal articles and by presenting at two national meetings. Changes/Problems:The progress of our research group was hindered due to the pandemic (COVID-19) and the inability to secure external funds. What opportunities for training and professional development has the project provided?This project provided opportunities to learn research skills for undergraduate and graduate students and Post-docs. Undergraduate students learn about experimental design and data collection with accuracy. Graduate students learn analytical skills to characterize biomass, biofuels, and biochemical and also write manuscripts. Post-docs received training on mentoring undergraduate and graduate students, developing research proposals, and writing manuscripts. Graduate students and Post-docs also got opportunities to share their research findings in Biomass and Biofuel course taught by the investigator. How have the results been disseminated to communities of interest?Results were disseminated mainly through published peer-reviewed papers and presentation at national meetings. In some cases, research findings were also shared with industry stakeholders through targeted meetings. What do you plan to do during the next reporting period to accomplish the goals?Our focus is on producing biofuels and chemicals from biomass, agricultural wastes, and food wastes. We will continue exploring hydrothermal liquefaction of biomass and food waste for the production of liquid fuels. The work will focus on understanding the effect of process parameters, reaction mechanisms, and the role of heterogeneous catalysts on the biocrude upgradability. Additionally, we have identified a handful of bio-char based catalysts for the production of biofuels from Carinata oil. We will continue to explore reaction mechanisms associated with those catalysts and test those catalysts for other feedstocks such as algae oil, municipal sludge, and waste cooking oil.

Impacts
What was accomplished under these goals? The long-term goal of this project is to develop biobased fuels and value-added products. For the year 2020, the project was focused on producing biofuels and bioproducts from municipal sludge, lignin, Carinata. The team also focused on utilizing biochar for enhancing methane production from the aqueous phase of hydrothermal liquefaction of municipal sludge. Biofuels Production from Municipal Sludge: Municipal sludge is a product of waste treatment processes. Conventional sludge treatment methods include incineration, land application, and composting. The release of toxic substances into the atmosphere coupled with demonstrated leaching of contaminants into the subsurface makes these treatment methods unpopular. Our study examined the effect of temperature and solids content on the product yield and fuel quality of municipal sludge hydrothermal liquefaction (HTL) products. HTL was carried out on three sample types, two temperatures (300ºC and 325ºC) with a reaction residence time of 1 hour and a continuous stirring. The highest oil yield of 37.7±1.6 wt.% (dry basis, ash-free) was obtained in the thickened sludge liquefied at 325ºC, while the highest char yield of 20.6±1.6 wt.% was obtained in the catalyzed secondary sludge liquefaction at 325ºC. The higher heating value of the produced biocrude ranged from 24-35 MJ/kg. Biofuels from Carinata: In this study, we explored the production process of jet and diesel range hydrocarbons from non-edible hexane-extracted Brassica carinata oil. The influence of four heterogeneous catalysts (two noble metal catalysts: Palladium, Ruthenium, and two transition metal catalysts: nickel on carbon and alumina) was investigated at 400 °C. The catalysts were characterized using various analytical instruments. The upgrading experiments consisted of three different approaches: 1) single-step cracking (1-C), 2) single-step simultaneous cracking, and hydrotreatment (1-C.H), and 3) a two-step process of cracking followed by hydrotreatment (2-C.H). Reaction products were characterized using standard protocols. The 2-C.H process produced the highest amounts of desired hydrocarbons. The highest liquid yield of 81% with HHV of 47 MJ/kg was obtained using nickel on alumina catalyst. All catalysts appeared to be regenerable after partial deactivation. Model compound studies were performed using erucic acid that accounted for about 40% of carinata oil FFA profile. Reaction pathways were proposed according to the chemical analysis of the products. The results from this work has been submitted for publication to Fuel Processing Technology, and has been accepted for publication in 2021. Biocomposites and Biofuels from Lignin: Our group has explored the potential of utilizing lignin for the production of biofuels and bioproducts. We reviewed extensive literature on the use of solvent for lignin depolymerization. The structure of lignin was found to be more critical than reaction conditions in determining the product yields, and future research should have more emphasis on this aspect. Overall, high temperature and longer residence time were found to be useful for depolymerization under certain conditions, such as the presence of homogeneous catalysts, condensed lignin structure, and water as a solvent. This work has been published in Renewable and Sustainable Energy Reviews that has an Impact Factor of 12. We also explored the use of polylactic acid and lignin for additive manufacturing. Polylactic acid (PLA) and organosolv lignin were mixed at different ratios and extruded to obtain PLA-lignin composite filaments. PLA was replaced with lignin up to 20 wt%. Two plasticizers (polyethylene glycol (PEG) 2000 and struktol TR451) were added in varying concentrations to enhance the properties of PLA_L20 (20% lignin in PLA) composite filaments. The effect of lignin in PLA, and PEG, and struktol in PLA_L20 composites was investigated via tensile test, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy of the filaments, and dynamic mechanical analysis of 3D printed samples. A 2 wt% PEG was able to enhance both tensile stress and elongation at maximum load of PLA_L20 composite by 19% and 35%, respectively, whereas struktol TR451 was able to improve elongation at maximum load by 24%. Use of biochar for Enhancing Methane Production: Studies have shown that biochar enhances methane formation due to the presence of redox active moieties and its conductive properties. Our study investigated the influence of biochar, which was produced from Douglas fir pyrolysis, on biogas production and microbial community during anaerobic digestion (AD) of wastewater sludge. The results showed that biochar significantly enhances methane (CH4) production rate and increases its final yield during AD. The cumulative highest CH4 production obtaining in cultures with DF500 (biochar from Douglas fir at 500 °C) was about 11% and 98% more than the culture without biochar at 37 °C and 25 °C AD temperature, respectively. At 55 °C, the maximum CH4 yield reached 172.3 ml/g COD with DF730, which was about 48.3% more than the control culture. The microbial community analysis results showed that biochar could upregulate the role of micro-ecology, especially the methanogens, and improve the AD process. This research has opened the possibility of using biochar to increase methane production from anaerobic digestion. Other accomplishments are: two MS students graduated and continuing doctoral degrees in other institutes, four undergraduate students participated in the research, two post-docs are continuing their research, and 4 graduate students are working towards their degrees.

Publications

• Type: Journal Articles Status: Published Year Published: 2020 Citation: Hyungseok Nam, Shuang Wang, Sanjeev KC, Myung Won Seo, Sushil Adhikari, Rajdeep Shakya, Doyeon Lee, Saravanan R Shanmugam. 2020. Enriched hydrogen production over air and air-steam fluidized bed gasification in a bubbling fluidized bed reactor with CaO: Effects of biomass and bed material catalyst. Energy Conversion and Management. Vol. 225. pg. 113408
• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Vivek Patil, Sushil Adhikari, Phillip Cross, Hossein Jahromi. 2020. Progress in the solvent depolymerization of lignin. Renewable and Sustainable Energy Reviews. Vol. 133. pg. 110359
• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Sushil Adhikari, Maria Auad, Brian Via, Ajay Shah, Vivek Patil. 2020. Production of novolac resin after partial substitution of phenol from bio-oil. Transactions of the ASABE. Vol. 63(4). pg. 901-912
• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Sanjita Wasti and Sushil Adhikari. 2020. Use of biomaterials for 3d printing by fused deposition modeling technique: A review. Front Chem. Vol. 8. pg. 315. doi: 10.3389/fchem.2020.00315
• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Pixiang Wang, Haixin Peng, Sushil Adhikari, Brendan Higgins, Poulami Roy, Wei Dai, Xiaochong Shi. 2020. Enhancement of biogas production from wastewater sludge via anaerobic digestion assisted with biochar amendment. Bioresource Technology. Vol. 309. pp. 123368.