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Thermochemical Conversion of Food, Agricultural, and Forest Wastes into Biofuel

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A4: Bio-Energy".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 15932

Special Issue Editors


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Guest Editor
Department of Chemical and Environmental Engineering, University of Nottingham, Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia
Interests: fast pyrolysis; torrefaction; hydrothermal carbonization; bio-oil upgrading; extraction of chemicals
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Guest Editor
Department of Biosystems Engineering, Auburn University, Auburn, AL 36849, USA
Interests: biomass gasification; biomass pyrolysis; hydrothermal liquefaction; torrefaction; biodiesel production
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
Interests: thermochemical technologies; biomass conversion; waste conversion to energy and fuels; pyrolysis; hydrothermal liquefaction; reaction kinetics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biomass, which stores solar energy through photosynthesis, exhibits a high potential to replace or supplement fossil fuels as an energy resource. There are many technologies available to convert biomass to biofuels or value-added products. Among these technologies, thermochemical conversions, such as pyrolysis, gasification and hydrothermal operations, have received increasing attention due to their flexibility over feedstocks and the effectiveness to provide different products. This Special Issue focuses on various aspects of different thermo-chemical conversion processes on agricultural biomass and their further upgrading. Topics of interest include, but are not limited to:

  1. Physico-chemical analysis of biomass for thermo-chemical conversions;
  2. Analytical and applied pyrolysis;
  3. Gasification;
  4. Torrefaction;
  5. Hydrothermal liquefaction/carbonization;
  6. Upgrading of bio-oil/bio-crude;
  7. Syngas cleaning;
  8. Hydrogen production;
  9. Biochar tuning and applications;
  10. Techno-economic analysis;
  11. Life cycle assessment;
  12. Machine Learning models for thermochemical conversions.

Dr. Suchithra Thangalazhy-Gopakumar
Prof. Dr. Sushil Adhikari
Dr. Ravikrishnan Vinu
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • pyrolysis
  • gasification
  • torrefaction
  • hydrothermal
  • biomass
  • wastes
  • TEA and LCA
  • machine learning models

Published Papers (7 papers)

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Research

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24 pages, 2182 KiB  
Article
Influence of Red Mud Catalyst and Reaction Atmosphere on Hydrothermal Liquefaction of Algae
by Tawsif Rahman, Hossein Jahromi, Poulami Roy, Sushil Adhikari, Farshad Feyzbar-Khalkhali-Nejad, Tae-Sik Oh, Qichen Wang and Brendan T. Higgins
Energies 2023, 16(1), 491; https://doi.org/10.3390/en16010491 - 02 Jan 2023
Cited by 4 | Viewed by 1826
Abstract
Algae are a diverse group of aquatic organisms and have a potential to produce renewable biofuel via hydrothermal liquefaction (HTL). This study investigated the effects of reaction environments on biocrude production from “Tetraselmis sp.” algae strain by HTL process using red mud [...] Read more.
Algae are a diverse group of aquatic organisms and have a potential to produce renewable biofuel via hydrothermal liquefaction (HTL). This study investigated the effects of reaction environments on biocrude production from “Tetraselmis sp.” algae strain by HTL process using red mud (RM) based catalyst. The inert (N2), ethylene (C2H4), reducing (10% H2/90% N2), and oxidizing (10% O2/90% N2) environments were applied to the non-catalytic as well as catalytic HTL treatments with two forms of RM catalysts: RM reduced at 500 °C (RRM) and nickel-supported RM (Ni/RM). Under nitrogen, ethylene and reducing environments, the biocrude yield increased by the following trend: No Catalyst < RRM < Ni/RM. The Ni/RM catalyst produced the highest biocrude yield (37 wt.%) in an ethylene environment, generated the lowest total acid number (14 mg KOH/g) under inert atmosphere, and lowered sulfur (33–66%) and oxygen (18–30%) from biocrude products irrespective of environments. The RRM catalyst maximized the biocrude carbon content (61 wt.%) under a reducing environment and minimized the heavy metal and phosphorus transfer from the feedstock to biocrude in studied ambiences. The reducing environment facilitated mild hydrotreatment during HTL reaction in the presence of RRM catalyst. Among the non-catalytic experiments, the reducing atmosphere optimized carbon content (54.3 wt.%) and calorific value (28 MJ/kg) with minimum oxygen amount (27.2 wt.%) in biocrudes. Full article
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16 pages, 2251 KiB  
Article
Intermediate Pyrolysis of Bambara Groundnut Shell (BGS) in Various Inert Gases (N2, CO2, and N2/CO2)
by Mustapha Danladi Ibrahim, Yousif Abdalla Abakr, Suyin Gan, Lai Yee Lee and Suchithra Thangalazhy-Gopakumar
Energies 2022, 15(22), 8421; https://doi.org/10.3390/en15228421 - 10 Nov 2022
Cited by 4 | Viewed by 1726
Abstract
Energy from biomass is increasingly gaining attention amidst the environmental challenges of coal and fossil fuels. This study investigated the effects of inert gases (N2, CO2, and N2/CO2) on intermediate pyrolysis and product properties from [...] Read more.
Energy from biomass is increasingly gaining attention amidst the environmental challenges of coal and fossil fuels. This study investigated the effects of inert gases (N2, CO2, and N2/CO2) on intermediate pyrolysis and product properties from Bambara Groundnut Shells (BGS) (shells from an underutilized crop, which has high nutritional values). N2/CO2 atmosphere roughly represents flue gas. The results showed that the inert gases did not significantly affect the yields of bio-oil, biochar, and syngas. The pH of bio-oil ranged from 5.2–5.8, indicating the minimum presence of acids in bio-oil. The CHNS analysis showed that all bio-oil and biochar had their carbon content within 50.04–60.49 wt.%. The FESEM resulted in a wide range of pore sizes in biochar produced in an N2/CO2 atmosphere. The GC-MS (Gas Chromatography-Mass Spectrometry) analysis revealed the presence of compounds which can be categorized as alkene, acid, benzene derivatives, ketone, phenol derivatives, alcohol, aldehyde, alkyl, and ester. However, the presence of N2/CO2 gas favored alcohol and phenol production significantly. Full article
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12 pages, 1256 KiB  
Article
Kinetic Parameters Estimation of Thermal and Co-Pyrolysis of Groundnut De-oiled Cake and Polyethylene Terephthalate (PET) Waste
by Janaki Komandur, Abhishek Kumar, Preethi Para and Kaustubha Mohanty
Energies 2022, 15(20), 7502; https://doi.org/10.3390/en15207502 - 12 Oct 2022
Cited by 2 | Viewed by 1514
Abstract
The physicochemical characterization and kinetic evaluation of the thermal and co-pyrolysis of groundnut de-oiled cake (GDC) and PET plastic is examined in this present study. A bomb calorimeter, proximate/CHNS analysis, and a thermogravimetric analyzer were used to study the physicochemical characteristics of the [...] Read more.
The physicochemical characterization and kinetic evaluation of the thermal and co-pyrolysis of groundnut de-oiled cake (GDC) and PET plastic is examined in this present study. A bomb calorimeter, proximate/CHNS analysis, and a thermogravimetric analyzer were used to study the physicochemical characteristics of the biomass and plastic. By using a FTIR analysis, it was found that both samples had distinct functional groups. Iso-conversional models, such as Friedman’s, the Kissinger–Akhaira–Sunose, the Ozawa–Flynn–Wall, Starink’s, and the distributed activation energy models were employed in the calculation of the kinetic parameters. The physicochemical characterization provided valuable insights into the pyrolysis characteristics. The rate at which the feedstock was heated were 10, 20, and 30 °C min−1, and were used to study the thermal breakdown behavior of the GDC and PET by the TGA. The following temperatures are the active pyrolysis zones for the thermal pyrolysis and the co-pyrolysis: for the groundnut de-oiled cake, T = 150–650 °C; for the PET, T = 375–600 °C; and for the co-pyrolysis, T = 175–550 °C. For the thermal pyrolysis (for GDC, E = 127.49 kJ mol−1; PET, E = 201.45 kJ mol−1); and the co-pyrolysis (E = 175.86 kJ mol−1), Kissinger–Akhaira–Sunose revealed low activation energy. Full article
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13 pages, 3853 KiB  
Article
How to Train an Artificial Neural Network to Predict Higher Heating Values of Biofuel
by Anna Matveeva and Aleksey Bychkov
Energies 2022, 15(19), 7083; https://doi.org/10.3390/en15197083 - 27 Sep 2022
Cited by 2 | Viewed by 1234
Abstract
Plant biomass is one of the most promising and easy-to-use sources of renewable energy. Direct determination of higher heating values of fuel in an adiabatic calorimeter is too expensive and time-consuming to be used as a routine analysis. Indirect calculation of higher heating [...] Read more.
Plant biomass is one of the most promising and easy-to-use sources of renewable energy. Direct determination of higher heating values of fuel in an adiabatic calorimeter is too expensive and time-consuming to be used as a routine analysis. Indirect calculation of higher heating values using the data from the ultimate and proximate analyses is a more rapid and less equipment-intensive method. This study assessed the fitting performance of a multilayer perceptron as an artificial neural network for estimating higher heating values of biomass. The analysis was conducted using a specially gathered large and heterogeneous dataset (720 biomass samples) that included the experimental data of ultimate and proximate analysis on grass plants, peat, husks and shells, organic residues, municipal solid wastes, sludge, straw, and untreated wood. The quantity and preprocessing of data (namely, rejection of dependent and noisy variables; dataset centralization) were shown to make a major contribution to prediction accuracy improvement. In particular, it was demonstrated that 550 samples are sufficient to ensure convergence of the algorithm; carbon and hydrogen contents are sufficient ultimate analysis data; and volatile matters can be excluded from proximate analysis. The minimal required complexity of neural network is ~50 neurons. Full article
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15 pages, 1893 KiB  
Article
Torrefaction of Pulp Industry Sludge to Enhance Its Fuel Characteristics
by Tharaka Rama Krishna C. Doddapaneni, Linnar Pärn and Timo Kikas
Energies 2022, 15(17), 6175; https://doi.org/10.3390/en15176175 - 25 Aug 2022
Cited by 9 | Viewed by 1802
Abstract
Recently, under COP26, several countries agreed to phase-out coal from their energy systems. The torrefaction industry can take advantage of this, as the fuel characteristics of torrefied biomasses are comparable to those of coal. However, in terms of economic feasibility, torrefied biomass pellets [...] Read more.
Recently, under COP26, several countries agreed to phase-out coal from their energy systems. The torrefaction industry can take advantage of this, as the fuel characteristics of torrefied biomasses are comparable to those of coal. However, in terms of economic feasibility, torrefied biomass pellets are not yet competitive with coal without subsidies because of the high price of woody biomass. Thus, there is a need to produce torrefied pellets from low-cost feedstock; pulp industry sludge is one such feedstock. In this context, this study was focused on the torrefaction of pulp industry sludge. Torrefaction experiments were carried out using a continuous reactor, at temperatures of 250, 275, and 300 °C. The heating value of the sludge increased from 19 to 22 MJ/kg after torrefaction at 300 °C. The fixed carbon content increased from 16 wt.% for dried pulp sludge to 30 wt.% for torrefied pulp sludge. The fuel ratio was in the range of 0.27 to 0.61. The ash content of the pulp sludge was comparable to that of agricultural waste, i.e., around 12 wt.% (dry basis). The cellulose content in the sludge was reduced from 35 to 12 wt.% at 300 °C. Ash related issues such as slagging, fouling, and bed agglomeration tendency of the sludge were moderate. This study shows that torrefaction treatment can improve the fuel properties of pulp industry sludge to a level comparable to that of low-rank coal. Full article
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19 pages, 2883 KiB  
Article
Multi-Variate and Multi-Response Analysis of Hydrothermal Carbonization of Food Waste: Hydrochar Composition and Solid Fuel Characteristics
by Jaime E. Borbolla-Gaxiola, Andrew B. Ross and Valerie Dupont
Energies 2022, 15(15), 5342; https://doi.org/10.3390/en15155342 - 22 Jul 2022
Cited by 9 | Viewed by 1497
Abstract
To maximize food waste utilization, it is necessary to understand the effect of process variables on product distribution. To this day, there is a lack of studies evaluating the effects of the multiple variables of HTC on food waste. A Design of Experiment [...] Read more.
To maximize food waste utilization, it is necessary to understand the effect of process variables on product distribution. To this day, there is a lack of studies evaluating the effects of the multiple variables of HTC on food waste. A Design of Experiment (DoE) approach has been used to investigate the influence of three process variables on the product distribution and composition of process streams from the HTC of food waste. This work evaluates the effect of hydrothermal carbonization process conditions on the composition and utilization capabilities of hydrochar from food waste. Parametric analysis was carried out with a design of experiments of central composite rotatable design (CCRD) and response surface methodology (RSM). Derringer’s desirability function was employed to perform a multi-response evaluation. The optimized process conditions were 260.4 °C, 29.5 min reaction time, and 19.6% solid load. The predicted optimized responses were EMC = 2.7%, SY = 57.1%, EY = 84.7%, ED = 1.5, and HHV of 31.8 MJ/Kg, with a composite desirability of 0.68. Temperature and solid load had a significant effect on all evaluated responses, while reaction time was non-significant. Full article
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Review

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20 pages, 2563 KiB  
Review
Biochar as Cement Replacement to Enhance Concrete Composite Properties: A Review
by Aan Mohammad Nusrat Aman, Anurita Selvarajoo, Teck Leong Lau and Wei-Hsin Chen
Energies 2022, 15(20), 7662; https://doi.org/10.3390/en15207662 - 17 Oct 2022
Cited by 9 | Viewed by 5306
Abstract
In recent years, concrete has been accessible and economical in the construction industry, resulting in high demand for its components. Cement is known for its negative impact on the environment, which has led researchers to investigate alternative supplementary materials. Recently, biochar has been [...] Read more.
In recent years, concrete has been accessible and economical in the construction industry, resulting in high demand for its components. Cement is known for its negative impact on the environment, which has led researchers to investigate alternative supplementary materials. Recently, biochar has been proposed as a replacement to cement in small amounts, with an optimum amount of 0.08–5, resulting in increased strength and enhancement of other properties of concrete composites. The biochar production process and its components are more economical and environmentally friendly than that of cement. In this review, we focus on research highlighting the properties of biochar that aid in the enhancement of biochar mortar and concrete composite properties. We explore properties of biochar such as water absorption, as well as compressive, flexural and tensile strength. Progress has been made in research on biochar concrete composites; however, additional investigations are required with respect to its carbon-sequestering abilities and life cycle assessment for its production process. Full article
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