Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production

Topic Information

Dear Colleagues,

Wastes are produced by most essential activities necessitated by modern society, and their adequate disposal or valorization poses a significant sustainable development challenge. Waste-to-energy systems may contribute to waste valorization due to their diverse nature as well as their capacity to process large amounts of materials. Innovations in catalysts, reactor design, the genetic engineering of microorganisms, and downstream processing techniques have driven technological progress in waste conversion. This Topic invites original research papers to address new applications of thermochemical, biological, or integrated technologies for the conversion of organic, lignocellulosic, or polymeric wastes into energy or fuels. Additionally, authors are encouraged to submit papers addressing the state of the art and recent advancements in these areas in order to provide useful guidelines for future research. Biorefinery approaches combining material and energy valorization may be used to achieve waste valorization solutions that are both economically viable and environmentally friendly. Finally, emerging technologies for carbon dioxide capture, storage, and conversion into gas or liquid fuels exhibit great potential in lowering greenhouse gas emissions and valorizing these gaseous wastes. Efficient waste-to-energy solutions are necessary for reducing our consumption of essential raw materials as well as preserving the quality of air, water, and soils that constitute ecosystems. Thermochemical processes, such as combustion, carbonization, pyrolysis, and gasification, have been mainly applied to lignocellulosic or polymeric wastes, while biological processes such as anaerobic digestion or fermentation have been used to convert organic and lignocellulosic materials.

Potential topics include, but are not limited to, the following:

• Waste-to-energy technologies;
• Conversion of wastes into solid biofuels;
• Production of liquid biofuels from lipidic wastes, lignocellulosic wastes, or polymeric wastes;
• Production of gaseous biofuels through thermochemical or biological processes;
• Production of alcohols from organic or lignocellulosic wastes;
• Production of hydrogen from wastes;
• Catalytic upgrading of waste-derived fuels;
• Waste biorefineries; Microalgae-based biorefineries;
• Carbon dioxide capture, storage, and conversion into gas or liquid fuels;
• Life cycle analysis of waste-to-energy systems.

Prof. Dr. Margarida Gonçalves
Prof. Dr. Cândida Vilarinho
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600
Catalysts catalysts	3.8	6.8	2011	13.9 Days	CHF 2200
Fermentation fermentation	3.3	3.8	2015	15.4 Days	CHF 2100
Processes processes	2.8	5.1	2013	14.9 Days	CHF 2400
Waste waste	-	-	2023	34.1 Days	CHF 1000

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Published Papers (10 papers)

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All Energies Catalysts Fermentation Processes Waste

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18 pages, 4238 KiB  

Open AccessReview

A Review of Upscaling Hydrothermal Carbonization

by Thi. Thu-Trang Ho, Ahmad Nadeem and Kangil Choe

Energies 2024, 17(8), 1918; https://doi.org/10.3390/en17081918 - 17 Apr 2024

Cited by 9 | Viewed by 4670

Abstract

Hydrothermal carbonization (HTC) has recently emerged as a promising technology for converting diverse forms of waste with a high moisture content into value-added products such as biofuel, biochar, and activated carbon. With an increasing demand for sustainable and carbon-neutral energy sources, HTC has [...] Read more.

Hydrothermal carbonization (HTC) has recently emerged as a promising technology for converting diverse forms of waste with a high moisture content into value-added products such as biofuel, biochar, and activated carbon. With an increasing demand for sustainable and carbon-neutral energy sources, HTC has attracted considerable attention in the literature. However, a successful transition from laboratory-scale to large-scale industrial applications entails notable challenges. This review critically assesses the upscaling of hydrothermal carbonization processes, emphasizing the challenges, innovations, and environmental implications associated with this transition. The challenges inherent in upscaling HTC are comprehensively discussed, including aspects such as reactor design, process optimization, and the current treatment technology for process water. This review presents recent innovations and technological advancements that address these challenges and explores integrated solutions to enhancing hydrothermal carbonization’s scalability. Additionally, this review highlights key companies that have developed and implemented HTC plants for commercial purposes. By overcoming the obstacles and achieving advancements in the upscaling of hydrothermal carbonization, this review contributes to the ongoing efforts to realize the full potential of HTC as a sustainable and scalable biomass conversion technology and proposes future directions. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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15 pages, 1899 KiB  

Open AccessEditor’s ChoiceArticle

Determination of Kinetic and Thermodynamic Parameters of Biomass Gasification with TG-FTIR and Regression Model Fitting

by Viktória Zsinka, Bálint Levente Tarcsay and Norbert Miskolczi

Energies 2024, 17(8), 1875; https://doi.org/10.3390/en17081875 - 15 Apr 2024

Cited by 2 | Viewed by 1547

Abstract

In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as [...] Read more.

In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as a basis for kinetic analysis with three different isoconversional, model-free methods, which were the KAS, FWO and Friedman methods. Afterwards, the activation energy and the pre-exponential factor were determined, and no significant difference could be identified among the used methods (difference was under 5%), achieving 203–270 kJ/mol of E_a on average. Thereafter, the thermodynamic parameters were studied. Based on the TG-FTIR data, a logistic regression model was fitted to the data, which gives information about the thermal degradation and the obtained components with different heating rates. The FTIR analysis resulted in differential peaks corresponding to the studied components that were detected within the temperature range of 350–380 °C. The primary degradation processes occurred within a broader temperature range of 200–600 °C. Accordingly, in this work, the use of logistic mixture models as an alternative to traditional kinetic models for the description of the TGA process was also investigated, reaching adequate performance in fitting by a validation data coefficient of determination of R² = 0.9988. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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20 pages, 7177 KiB  

Open AccessArticle

CFD–DEM Simulation of Heat Transfer and Reaction Characteristics of Pyrolysis Process of MSW Heated by High-Temperature Flue Gas

by Meng Wang, Tianyuan Jia, Xiaoan Song, Lijie Yin, Dezhen Chen and Kezhen Qian

Processes 2024, 12(2), 390; https://doi.org/10.3390/pr12020390 - 15 Feb 2024

Cited by 5 | Viewed by 1749

Abstract

Pyrolysis is a promising disposal method for municipal solid waste (MSW) due to the high-value utilization of the organic components of MSW. Traditional indirect heating has low heat transfer efficiency and requires an increase in the heat exchange area. In this study, a [...] Read more.

Pyrolysis is a promising disposal method for municipal solid waste (MSW) due to the high-value utilization of the organic components of MSW. Traditional indirect heating has low heat transfer efficiency and requires an increase in the heat exchange area. In this study, a refined numerical simulation model for the pyrolysis of four typical MSW components with high-temperature flue gas was established to study the influence of flue gas on the heat transfer and reaction characteristics of MSW. The temperature distribution and particle size change in different components were obtained, and the effects of flue gas temperature and velocity on the pyrolysis process were analyzed. It was found that the temperature difference of the four components along the bed height direction was about 1.36–1.81 K/mm, and the energy efficiency was about 55–61%. When the four components were uniformly mixed, the temperature increase rates of each component were similar during the pyrolysis process. As the flue gas temperature increased, the amount of gas consumption decreased and the energy efficiency increased. When the flue gas velocity increased, the flue gas consumption increased and the energy efficiency decreased. The research results are of great significance for the promotion and application of pyrolysis technology to MSW with high-temperature flue gas. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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16 pages, 5344 KiB  

Open AccessEditor’s ChoiceArticle

Surface Modification of Fe-ZSM-5 Using Mg for a Reduced Catalytic Pyrolysis Temperature of Low-Density Polyethylene to Produce Light Olefin

by Yincui Li, Ting Liu, Shengnan Deng, Xiao Liu, Qian Meng, Mengxue Tang, Xueying Wu and Huawei Zhang

Catalysts 2024, 14(1), 78; https://doi.org/10.3390/catal14010078 - 18 Jan 2024

Cited by 4 | Viewed by 2782

Abstract

Although the catalytic pyrolysis of low-density polyethylene (LDPE) to produce light olefin has shown potential industrial application advantages, it has generally suffered when using higher pyrolysis temperatures. In this work, Mg-modified Fe-ZSM-5 was used for catalytic conversion of LDPE to obtain light olefin [...] Read more.

Although the catalytic pyrolysis of low-density polyethylene (LDPE) to produce light olefin has shown potential industrial application advantages, it has generally suffered when using higher pyrolysis temperatures. In this work, Mg-modified Fe-ZSM-5 was used for catalytic conversion of LDPE to obtain light olefin in a fixed bed reactor. The effects of catalyst types, pyrolysis temperatures, and Mg loading on the yield of light olefin were investigated. The 1 wt% Mg loading slightly improved the yield of light olefin to 38.87 wt% at 395 °C, lowering the temperature of the pyrolysis reaction. We considered that the higher light olefin yield of Fe-Mg-ZSM-5 was attributed to the introduction of Mg, where Mg regulated the surface acidity of the catalyst, inhibited the secondary cracking reaction, and reduced coking during the pyrolysis process. Furthermore, the addition of Mg also dramatically reduced the average particle size of Fe oxides from 40 nm to 10 nm, which is conducive to a lower catalytic reaction temperature. Finally, the spent catalyst could be easily regenerated at the conditions of 600 °C in airflow with a heating rate of 10 °C/min for 1 h, and the light olefin yield remained higher than 36.71 wt% after five cycles, indicating its excellent regeneration performance. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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29 pages, 1595 KiB  

Open AccessReview

Enhancing Methane Yield in Anaerobic Co-Digestion of Primary Sewage Sludge: A Comprehensive Review on Potential Additives and Strategies

by Foteini Sakaveli, Maria Petala, Vasilios Tsiridis and Efthymios Darakas

Waste 2024, 2(1), 29-57; https://doi.org/10.3390/waste2010002 - 16 Jan 2024

Cited by 4 | Viewed by 3430

Abstract

Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a [...] Read more.

Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a sustainable solution for managing sewage sludge while generating renewable energy. The present study provides a comprehensive examination of the current state of knowledge regarding the anaerobic digestion of PS. Co-digestion of PS with organic substrates, including food waste and agro-industrial residues, emerges as a promising approach to boost biogas production. Additionally, the utilization of additives such as glucose and clay minerals has shown potential in improving methane yield. Critical factors affecting AD, such as pretreatment methods, carbon-to-nitrogen (C/N) ratio, temperature, pH, volatile fatty acids (VFAs) levels, organic loading rates (OLR), inoculum-to-substrate ratio (ISR), and the role of additives, have been meticulously studied. Finally, this review consolidates existing knowledge to advance our understanding of primary sewage sludge anaerobic digestion, fostering more efficient and sustainable practices in sludge management and renewable energy generation. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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17 pages, 5089 KiB  

Open AccessArticle

Characterization of Uganda’s Main Agri-Food Value Chain Wastes for Gasification

by Peter Wilberforce Olupot, Tadeo Mibulo and Jacintha Gumoteyo Nayebare

Energies 2024, 17(1), 164; https://doi.org/10.3390/en17010164 - 28 Dec 2023

Cited by 2 | Viewed by 1709

Abstract

Agricultural residues are a source of energy derived through various conversion processes. They are gaining attention as a solution to limited energy access in developing countries in which a majority of the population depends on agriculture for a living at a time when [...] Read more.

Agricultural residues are a source of energy derived through various conversion processes. They are gaining attention as a solution to limited energy access in developing countries in which a majority of the population depends on agriculture for a living at a time when global population growth is outpacing the depreciation of conventional energy sources. This study characterized residues generated along the main agri-food value chains in Uganda for gasification by reviewing relevant literature and through field measurements and laboratory experiments. Maize, beans, cassava, banana, coffee, and sugarcane are the most important value chains, occupying 5.73 million hectares, and accounting for 40% of the country’s total area under cultivation. In terms of biomass residues, banana, maize, and sugarcane are the most feasible options, producing 4.18, 2.2, and 0.6 metric tons of biomass waste per ton, respectively. The bulk densities vary from 65.5 to 160 kg/m³, moisture content from 6.67 to 22.5%, and heating values from 12.6 to 16.74 MJ/kg for all residues. In terms of principal elements, oxygen has the highest proportion of 38.76–57.25% followed by carbon, 33.46–47.9%, and hydrogen 6%. The lignocellulosic composition is 23.46–41.38% hemicellulose, 9.9–55% cellulose, and 5.77–35% lignin. The three value chains have the potential to generate 172.2 PJ annually, which is enough to offset 50% of the cooking energy demands for Uganda. The main disadvantage of this is the low bulk density, which raises production costs and reduces conversion efficiency. Bulk density can be improved by densification through the compaction of residues. Given their composition and current utilization, maize stover, banana leaves, banana pseudo stems, and sugarcane tops are promising gasification feedstocks. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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17 pages, 1491 KiB  

Open AccessArticle

Valorizing the Input and Output Waste Streams from Three PtX Case Studies in Denmark—Adopting a Symbiotic Approach

by Rikke Lybæk and Tyge Kjær

Waste 2023, 1(4), 884-900; https://doi.org/10.3390/waste1040051 - 6 Oct 2023

Viewed by 2156

Abstract

This study aimed to investigate the waste streams from the production of hydrogen energy carriers from PtX technology and identify how they can be valorized by applying a symbiotic approach to enable greater utilization of the inputs and outputs from such plants. Various [...] Read more.

This study aimed to investigate the waste streams from the production of hydrogen energy carriers from PtX technology and identify how they can be valorized by applying a symbiotic approach to enable greater utilization of the inputs and outputs from such plants. Various electrolysis development projects are under development or in the pipeline in Europe and Denmark, but in many cases, it is not clear how waste streams are emphasized and valued in these projects. Thus, three exploratory case studies (a city, a rural, and an energy hub case) were investigated herein exemplifying state-of-the-art electrolysis projects currently being deployed, with a focus on identifying how and to what extent waste streams are being valorized in these projects and energy system integration is being pursued. Inspired by the industrial symbiosis literature, we analyzed how internal, regional, and long-distance symbiotic collaboration is realized within these cases and found them to be very different in terms of the energy carrier produced, the current development stage, and the access to appropriate energy infrastructure. This paper concludes that the co-location of PtX technology near biogas plants would provide a great opportunity for the integration of the produced energy carriers and waste streams into the existing energy system and, hence, could assist in stabilizing fluctuating renewable energy sources to enable their more efficient use in the energy system. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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11 pages, 1660 KiB  

Open AccessArticle

Applicability of Rice Husk Residue Generated by the Silica Extraction Process to Anaerobic Digestion for Methane Production

by Seon Young Park, Byoung Seung Jeon, Yang Mo Gu, Ji Yeon Park, Hyunook Kim, Byoung-In Sang, Eunsung Kan, Okkyoung Choi and Jin Hyung Lee

Energies 2023, 16(14), 5415; https://doi.org/10.3390/en16145415 - 17 Jul 2023

Cited by 4 | Viewed by 2457

Abstract

Rice husks are a feedstock of biogenic silica because of their high silica content. After silica extraction, a solid residue comprising mostly carbohydrates is present. Solid residue valorization is important for closed-loop systems using rice husk and has minimal negative environmental impacts. In [...] Read more.

Rice husks are a feedstock of biogenic silica because of their high silica content. After silica extraction, a solid residue comprising mostly carbohydrates is present. Solid residue valorization is important for closed-loop systems using rice husk and has minimal negative environmental impacts. In this study, we used solid rice husk that was generated by silica extractionto anaerobic digestion for producing biomethane. The rice husk residue was characterized in terms of total solids, volatile solids, pH, composition, and particle size. Changing the characteristics increased biogas production by 2.48-fold compared to that of raw rice husk. The residue produced 166.4 mL-biogas g⁻¹ vs. and 100.4 mL CH 4 g⁻¹ VS, much more than previously reported. Microbial community analysis, which was conducted to investigate the biological reasons for increased biogas and methane, found increased Bacteroidetes levels in the rice husk samples. Among archaeal communities, Bathyarchaeota was more abundant in all rice husk samples than in the inoculum. The rice husk residue contained more operational taxonomic units than other samples. These changes in the microbial community significantly influenced the anaerobic digestion of the rice husk residue and improved methane production. Our findings provide a basis for the cleaner utilization of rice husk residue to produce renewable energy. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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16 pages, 3078 KiB  

Open AccessArticle

Screening of Ultraviolet-Induced Thermotolerant Yeast Mutants and Their Performance

by Xiaodi Li, Yan Lin, Hainan Kong and Zhiquan Wang

Fermentation 2023, 9(7), 608; https://doi.org/10.3390/fermentation9070608 - 28 Jun 2023

Cited by 3 | Viewed by 2491

Abstract

The simultaneous saccharification and fermentation (SSF) technique holds promise for the conversion of lignocellulose to ethanol. However, the optimal fermentation temperature of yeast is lower than the enzymatic hydrolysis temperature of the saccharification process, which leads to the temperature of the actual production [...] Read more.

The simultaneous saccharification and fermentation (SSF) technique holds promise for the conversion of lignocellulose to ethanol. However, the optimal fermentation temperature of yeast is lower than the enzymatic hydrolysis temperature of the saccharification process, which leads to the temperature of the actual production process of SSF usually being lower than 38 °C. In this work, two ultraviolet (UV)-induced mutations were performed step by step using Saccharomyces cerevisiae BY4742 as the original strain to enable the yeast to perform well at higher temperatures. Thermotolerant strains obtained through mutagenesis and screening, YUV1-1 and YUV2-2, were utilized for fermentation and SSF at a targeted temperature of 40 °C. They obtained ethanol yields comparable to those at 38 °C in SSF, whereas the ethanol yields of the original strain at 40 °C decreased by about 10% compared to those at 38 °C. This study proves that thermotolerant strains adapted to elevated fermentation and SSF temperatures can be obtained through UV mutagenesis and screening, thereby increasing the stability of the fermentation and SSF processes and lowering the subsequent distillation costs. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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15 pages, 5517 KiB  

Open AccessArticle

Study of Ash Sintering Temperature and Ash Deposition Behavior during Co-Firing of Polish Bituminous Coal with Barley Straw Using Non-Standard Tests

by Karol Król, Dorota Nowak-Woźny and Wojciech Moroń

Energies 2023, 16(11), 4424; https://doi.org/10.3390/en16114424 - 30 May 2023

Cited by 6 | Viewed by 1520

Abstract

The need to reduce CO₂ emissions forces the use of biomass as a fuel in the conventional energy conversion process implemented by combustion. Burning biomass alone can be problematic because of the high potential for slugging and fouling on boiler heating surfaces. [...] Read more.

The need to reduce CO₂ emissions forces the use of biomass as a fuel in the conventional energy conversion process implemented by combustion. Burning biomass alone can be problematic because of the high potential for slugging and fouling on boiler heating surfaces. Therefore, co-firing of biomass with coal is used. This article presents the results of a study of biomass blends of barley, straw, and hard coal biomass from the Polish Makoszowy mine. The sintering of ash from biomass-coal blends was studied by experimental non-standard methods, such as the fracture stress and the pressure drop test. The results were confirmed with the result of thermodynamic modeling using FactSage 8.0 software. Additionally, ash deposition tests were performed in a 3.5 m boiler. The tests conducted showed a significant effect of the addition of biomass to hard coal on the formation of ash deposits on the heating surfaces of the boiler. In addition, the usefulness of non-standard methods in the assessment of the degree of fouling and slugging hazard was confirmed. Full article

(This article belongs to the Topic Valorizing Waste through Thermal and Biological Processes for Sustainable Energy Production)

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