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Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition

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

Deadline for manuscript submissions: 15 September 2026 | Viewed by 12362

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Dr. Małgorzata Sieradzka

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Department of Thermal Technology and Environmental Protection, Faculty of Metal Engineering and Industrial Computer Science, AGH University of Krakow, Mickiewicza 30 Av., 30-059 Krakow, Poland
Interests: bioenergy; biomass; waste; gasification; catalysts; catalytic gasification
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Special Issue Information

Dear Colleagues,

Climate change and the increasing levels of greenhouse gas emissions, coupled with rapid urbanization and the depletion of exhaustible natural resources, are pressing global concerns. Addressing these challenges requires decisive action to meet resource demands while ensuring environmental protection, reducing emissions, and minimizing waste generation.

To achieve energy independence from fossil fuels and fulfill the European Union’s targets for renewable energy adoption and greenhouse gas reduction, significant advancements are necessary. The thermal processing of biomass and waste-derived fuels presents a promising solution to these needs.

Biomass has played a crucial role as a renewable energy source, contributing to lower or even negative CO₂ emissions and increasing the share of renewables in global energy consumption. Additionally, refuse-derived fuel offers notable advantages when properly processed and utilized. However, compared to fossil fuels, the energy density of biomass and waste fuels remains relatively low, necessitating further research and technological improvements.

This Special Issue (second edition) aims to showcase recent advances in bioenergy production through biomass and waste conversion, encompassing pyrolysis, gasification, liquefaction, torrefaction, hydrothermal carbonization, direct combustion, and co-combustion. Furthermore, it highlights the utilization and valorization of by-products and residues from these processes in alignment with circular economy principles.

Topics of interest include, but are not limited to, the following:

Advanced methods for biomass and waste-to-energy conversion;
The optimization of pyrolysis, gasification, and liquefaction processes;
Innovations in torrefaction and hydrothermal carbonization;
Co-combustion strategies for enhanced energy recovery;
The utilization and valorization of process residues and by-products;
Environmental impact assessments and sustainability analyses;
Techno-economic evaluations of bioenergy systems;
Life cycle assessment and circular economy approaches.

We welcome original research articles, experimental and numerical studies, and comprehensive review papers summarizing the state of the art in these fields.

Dr. Małgorzata Sieradzka
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

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

biomass
char
refuse-derived fuel
waste management
circular economy
bioenergy
fuel characterization
sustainability
waste valorization
energy recovery
thermal conversion
torrefaction
pyrolysis
gasification
hydrothermal carbonization
combustion

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Related Special Issue

Advanced Bioenergy, Biomass and Waste Conversion Technologies in Energies (12 articles)

Published Papers (10 papers)

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Research

Jump to: Review

34 pages, 828 KB

Open AccessArticle

Market Assessment of Biomethane from Crop Residues in Ukraine: Techno-Economic Feasibility and Environmental Performance

by Olena Pimenowa, Włodzimierz Rembisz, Liudmyla Udova, Lubov Moldavan, Yan Kapranov, Bożena Iwanowska and Svetlana Sitnicka

Energies 2026, 19(8), 1891; https://doi.org/10.3390/en19081891 - 13 Apr 2026

Viewed by 712

Abstract

Global agriculture generates more than 5 billion tonnes of post-harvest crop residues each year, most of which remain unused for energy production. Within the broader landscape of advanced biomass and waste conversion technologies (thermochemical and biochemical pathways), producing biomethane from agricultural residues represents a complementary waste-to-energy route that converts decentralized feedstock into a standardized energy carrier. Mobilizing this agro-biomass for biogas/biomethane production via the anaerobic digestion of crop residues offers a promising instrument for decarbonizing agriculture, reducing greenhouse gas emissions, and advancing a circular bioeconomy. This study provides a techno-economic, environmental, and market assessment of biomethane production from post-harvest residues—specifically wheat and barley straw and maize stover—in Ukraine. We estimate the feedstock potential of crop residues and substantiate environmentally permissible removal levels accounting for soil organic matter requirements; we also characterize the role of digestate and biochar amendments in improving soil fertility, increasing mineral nitrogen availability, and enhancing crop yields. The results indicate substantial greenhouse gas mitigation potential relative to fossil natural gas. Practical recommendations are proposed to scale biomethane production from crop residues as part of Ukraine’s agricultural sustainability strategy. Under current cost and policy assumptions, many biomethane projects in Ukraine approach commercial viability, particularly in regions where damaged gas infrastructure creates local demand for a decentralized gas supply. The paper evaluates market assessment and investment feasibility of crop-residue biomethane scenarios under cost, regulatory, and infrastructure constraints. Overall, the findings suggest that agricultural residues can serve as a key feedstock for decarbonizing agriculture and biomethane-based energy systems in Ukraine. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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21 pages, 2250 KB

Open AccessArticle

Predictive Characterization Analysis for Quality Evaluation of Biochar from Olive and Citrus Agricultural Residues: A Practical Framework for Circular Economy Applications

by Monica Carnevale, Adriano Palma, Mariangela Salerno, Francesco Gallucci, Alberto Assirelli and Enrico Paris

Energies 2026, 19(3), 804; https://doi.org/10.3390/en19030804 - 3 Feb 2026

Viewed by 511

Abstract

The sustainable management and valorisation of agricultural and agro-industrial residues are essential to reduce environmental impacts, enhance resource efficiency, and support circular economy strategies. In Mediterranean regions, large quantities of residual biomass are annually produced from olive and citrus supply chains, representing promising feedstocks for biochar production. In this study, biochar was obtained at 600 °C in a fixed-bed reactor under a N₂ atmosphere from four representative feedstocks: olive pruning (OPr), citrus pruning (CPr), olive pomace (OPo), and citrus peel (CPe). The resulting biochar was characterized in terms of physico-chemical, energetic, and structural properties, including proximate and ultimate analyses, fuel properties, cation exchange capacity (CEC), pH, elemental ratios (O/C, H/C, N/C), thermal stability, bulk density, metal content, and surface morphology (SEM), in order to assess parameters relevant to environmental potential applications. The results highlighted clear feedstock-dependent differences. OPoB and CPeB exhibited the highest thermal stability (0.56–0.66), indicating a strong potential for long-term carbon sequestration. CPeB showed the highest CEC (47.2 cmol kg⁻¹). From an application-oriented perspective, this high CEC suggests that, when applied to soil at typical amendment rates (2–5 wt%), CPeB could potentially increase soil CEC by approximately 10–30%, thereby improving nutrient retention and cation availability. Energy yields were highest for citrus-derived biochar (42.0–47.5%), while OPoB exhibited the lowest solid yield due to its higher volatile content. SEM analysis revealed marked structural differences, with OPrB retaining an ordered lignocellulosic porous structure, whereas OPoB and CPeB displayed highly irregular morphologies, favorable for surface reactivity. Overall, this study demonstrates that olive and citrus residues are suitable feedstocks for producing biochar with differentiated properties, and that a rapid screening methodology can support feedstock selection and biochar design for targeted energy, soil amendment, and carbon management applications. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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12 pages, 3507 KB

Open AccessArticle

Characteristics and Impact of Fouling from Copper Production on the Operation of a Waste Heat Recovery Boiler

by Roksana Urbaniak, Beata Hadała and Marcin Kacperski

Energies 2026, 19(1), 31; https://doi.org/10.3390/en19010031 - 20 Dec 2025

Viewed by 642

Abstract

The paper focuses on the characteristics of fouling from copper production on the tube surface in a waste heat recovery boiler during the transfer of heat from the flash furnace process gas. The likely mechanism of deposit formation on the tubes is described, and the morphology and chemical composition of the bound deposit taken from the radiation zone of the waste heat recovery boiler are reviewed. In addition, the impact of the presence of bound and loose deposits on the tube’s surface on the increase in the deposit surface temperature and the decrease in the heat transferred at the inner side of the tube is evaluated. Changes in the chemical, mineralogical, and phase constitutions along the thickness of the build-up were established on the basis of XRF, SEM, and XRD quantitative analyses. The heat exchanger tube temperature distribution was computed with the finite element method using an axi-symmetrical solution of the heat conductivity equation. Computing was carried out for a clean tube surface as well as for a case with loose and bound deposits present on the surface, with thicknesses of 0.5 cm, 1 cm, and 2 cm. The boundary conditions at the deposit side varied. For loose deposits with a thickness of 0.5 cm, the decline in the heat transferred was similar to the values obtained for a bound deposit with a thickness of 2 cm. It was established that, for a deposit with a thickness of 20 mm, there was an approximately 80% decline in the energy transferred by the walls compared to the clean tube surface. This study represents a novel approach by integrating mineralogical and phase analyses with finite element modelling to comprehensively assess the impact of both bound and loose deposits on heat transfer efficiency in waste heat recovery boilers from copper production. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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18 pages, 1023 KB

Open AccessFeature PaperArticle

Hydrothermal Treatment of Kitchen Waste as a Strategy for Dark Fermentation Biohydrogen Production

by Marlena Domińska, Katarzyna Paździor, Radosław Ślęzak and Stanisław Ledakowicz

Energies 2025, 18(21), 5811; https://doi.org/10.3390/en18215811 - 4 Nov 2025

Cited by 1 | Viewed by 886

Abstract

This study presents an innovative approach to the production of hydrogen from liquids following hydrothermal treatment of biowaste, offering a potential solution for renewable energy generation and waste management. By combining biological and hydrothermal processes, the efficiency of H₂ production can be significantly improved, contributing to a reduced carbon footprint and lower reliance on fossil fuels. The inoculum used was fermented sludge from a wastewater treatment plant, which had been thermally pretreated to enhance microbial activity towards hydrogen production. Kitchen waste, consisting mainly of plant-derived materials (vegetable matter), was used as a substrate. The process was conducted in batch 1-L bioreactors. The results showed that higher pretreatment temperatures (up to 180 °C) increased the hydrolysis of compounds and enhanced H₂ production. However, temperatures above 180 °C resulted in the formation of toxic compounds, such as catechol and hydroquinone, which inhibited H₂ production. The highest hydrogen production was achieved at 180 °C (approximately 66 mL H₂/g_TVSKW). The standard Gompertz model was applied to describe the process kinetics and demonstrated an excellent fit with the experimental data (R² = 0.99), confirming the model’s suitability for optimizing H₂ production. This work highlights the potential of combining hydrothermal and biological processes to contribute to the development of sustainable energy systems within the circular economy. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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16 pages, 1292 KB

Open AccessArticle

Assessment of the Energy Parameters of Pedicels and Pomace of Selected Grapevine Varieties from the PIWI Group

by Magdalena Kapłan, Kamila E. Klimek, Grzegorz Maj, Kamil Buczyński and Anna Borkowska

Energies 2025, 18(20), 5444; https://doi.org/10.3390/en18205444 - 15 Oct 2025

Viewed by 690

Abstract

In view of the growing challenges related to energy transition and the need to implement circular economy principles, the use of waste from the wine industry as bioenergy raw materials is becoming increasingly important. The aim of the study was to assess the energy potential of biomass in the form of grape stems and pomace from four varieties (PIWI)—Hibernal, Muscaris, Regent and Seyval Blanc—grown in south-eastern Poland. The analyses included the determination of technical and elementary parameters, pollutant emission indicators and exhaust gas composition parameters. The pomace was characterised by a higher calorific value, higher carbon (C) and hydrogen (H) content and lower dust emissions compared to the stems, but with higher carbon dioxide (CO₂) emissions. Stems had a higher ash content, which may limit their energy use. The Hibernal variety achieved the highest calorific values at low moisture and low sulphur content, while Muscaris was characterised by increased nitrogen and sulphur content and higher sulphur dioxide emissions (SO₂) and dust emissions. The Regent variety showed relatively high nitrogen oxides (NO_X) emissions. Cluster analysis confirmed the diversity of varieties in terms of energy potential and waste biomass quantity. The results indicate that waste from PIWI grapevine cultivation can be a valuable local raw material for renewable energy production, contributing to waste reduction and greenhouse gas emissions in the agricultural sector, but its suitability depends on the variety and type of biomass. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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13 pages, 1366 KB

Open AccessArticle

The Influence of Vine Rootstock Type on the Energy Potential of Differentiated Material Obtained from Wine Production

by Kamila E. Klimek, Magdalena Kapłan, Grzegorz Maj, Anna Borkowska and Kamil Buczyński

Energies 2025, 18(19), 5062; https://doi.org/10.3390/en18195062 - 23 Sep 2025

Viewed by 585

Abstract

In the context of growing demand for renewable energy sources and greenhouse gas emission reductions, increasing attention is being paid to the use of agricultural waste as bioenergy feedstock. The energy potential of biomass in the form of vine stems and pomace from the Regent variety of grapes, grafted onto their own roots and various types of rootstocks (125AA, SO₄, 161-49), was assessed, where the control group consisted of ungrafted shrubs growing on their own roots, cultivated in south-eastern Poland. The analyses included the determination of technical and elementary parameters, pollutant emission indicators, and exhaust gas composition parameters. Compared to stems, pomace had a higher calorific value, higher C and H content, and lower dust emissions, while at the same time emitting more CO₂. Stems, on the other hand, showed higher ash content and higher dust emissions, which may limit their energy potential. Among the analysed substrates, pomace from 125AA achieved the highest calorific values at a low moisture content, while biomass from substrate 161-49 was distinguished by the lowest sulphur content and a favourable emission balance. Cluster analysis showed clear grouping of substrates in terms of fuel and emission parameters, indicating the possibility of optimal substrate selection for the production of bioenergy feedstock. The results confirm that the appropriate selection of rootstocks in viticulture can significantly increase the energy value of waste biomass and reduce emissions, supporting the development of local renewable energy systems. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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14 pages, 1537 KB

Open AccessArticle

Impact of Demineralization on Various Types of Biomass Pyrolysis: Behavior, Kinetics, and Thermodynamics

by Shaoying Shen, Jianping Li, Yuanen Lai, Rui Zhang, Honggang Fan, Wei Zhao, Feng Shen, Yuanjia Zhang and Weiqiang Zhu

Energies 2025, 18(16), 4289; https://doi.org/10.3390/en18164289 - 12 Aug 2025

Cited by 1 | Viewed by 1046

Abstract

This study systematically investigates the effects of demineralization on the pyrolysis characteristics, kinetics, and thermodynamics of three biomass types (eucalyptus, straw, and miscanthus) using thermogravimetric analysis (TGA) combined with multiple kinetic approaches. The Coats–Redfern integral model was employed to determine the reaction mechanisms. The results indicate that the primary weight-loss temperature ranges for eucalyptus, straw, and miscanthus were 222.02~500.23 °C, 205.43~500.13 °C, and 202.30~490.52 °C, respectively. Demineralization increased the initial pyrolysis temperature and significantly enhanced the reaction rates. Kinetics analysis revealed that the ash content significantly influences the activation energy of the pyrolysis reaction. The average activation energies follow the trend eucalyptus (193.48 kJ/mol) < miscanthus (245.66 kJ/mol) < straw (290.13 kJ/mol). After demineralization, the activation energies of both straw and miscanthus pyrolysis decreased, with the largest reduction observed in straw, which dropped by 77.53 kJ/mol. However, the activation energy for eucalyptus pyrolysis increased by 12.52 kJ/mol after demineralization. The Coats–Redfern model and thermodynamic analysis demonstrated that each type of biomass followed distinct reaction mechanisms at different stages, which were altered after demineralization. Additionally, demineralization leads to higher ΔH and Gibbs free energy ΔG for eucalyptus, but lower values for straw and miscanthus, which indicate that the ash content has a significant impact on the biomass pyrolysis reaction. These findings provide fundamental insights into the role of ash in biomass pyrolysis kinetics and offer theoretical support for the design of pyrolysis reactors. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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Review

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24 pages, 9501 KB

Open AccessReview

Evaluating the Performance of Biogas Plants Operating on Organic Waste: A Practical Approach

by Patrycja Pochwatka

Energies 2026, 19(10), 2337; https://doi.org/10.3390/en19102337 - 13 May 2026

Viewed by 327

Abstract

Biogas plants utilizing organic waste play an important role in the transition toward a circular economy and renewable energy systems. However, evaluating their actual performance is challenging due to the diversity of anaerobic digestion technologies, the wide range of feedstocks, and the use of various pretreatment methods. Consequently, assessing operational efficiency requires a comprehensive approach that goes beyond installed capacity alone. This paper synthesizes and systematizes existing approaches for evaluating the efficiency of biogas plants based on key operational indicators reported in the literature. The analysis considers a broad spectrum of feedstocks, highlighting the variability of input materials and their influence on plant performance. Particular attention is given to the internal energy consumption of electricity and heat, which directly affects net energy output and overall efficiency. The relationship between annual energy production (MWh) and installed capacity (MW) is analyzed as a core performance indicator enabling comparison between plants using different technologies, substrates, and scales. The proposed framework supports transparent performance assessment, operational optimization, and evidence-based decision-making in the development and management of waste-based biogas systems. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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22 pages, 1393 KB

Open AccessReview

Biogas Upgrading and Bottling Technologies: A Critical Review

by Yolanda Mapantsela and Patrick Mukumba

Energies 2025, 18(24), 6506; https://doi.org/10.3390/en18246506 - 12 Dec 2025

Cited by 4 | Viewed by 3056

Abstract

Biogas upgrading and bottling represent essential processes in transforming raw biogas produced via the anaerobic digestion of organic waste into high-purity biomethane (≥95% CH₄), a renewable energy source suitable for applications in cooking, transportation, and electricity generation. Upgrading technologies, such as membrane separation, pressure swing adsorption (PSA), water and chemical scrubbing, and emerging methods, like cryogenic distillation and supersonic separation, play a pivotal role in removing impurities like CO₂, H₂S, and moisture. Membrane and hybrid systems demonstrate high methane recovery (>99.5%) with low energy consumption, whereas chemical scrubbing offers superior gas purity but is limited by high operational complexity and cost. Challenges persist around material selection, safety standards, infrastructure limitations, and environmental impacts, particularly in rural and off-grid contexts. Bottled biogas, also known as bio-compressed natural gas (CNG), presents a clean, portable alternative to fossil fuels, contributing to energy equity, greenhouse gases (GHG) reduction, and rural development. The primary aim of this research is to critically analyze and review the current state of biogas upgrading and bottling systems, assess their technological maturity, identify performance optimization challenges, and evaluate their economic and environmental viability. The research gap identified in this study demonstrates that there is no comprehensive comparison of biogas upgrading technologies in terms of energy efficiency, price, scalability, and environmental impact. Few studies directly compare these technologies across various operational contexts (e.g., rural vs. urban, small vs. large scale). Additionally, the review outlines insights into how biogas can replace fossil fuels in transport, cooking, and electricity generation, contributing to decarbonization goals. Solutions should be promoted that reduce methane emissions, lower operational costs, and optimize resource use, aligning with climate targets. This synthesis highlights the technological diversity, critical barriers to scalability, and the need for robust policy mechanisms to accelerate the deployment of biogas upgrading solutions as a central component of a low-carbon, decentralized energy future. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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38 pages, 7400 KB

Open AccessReview

The Biorefinery Paradigm: Technologies, Feedstocks, and Retrofitting for Future Sustainable Energy

by Aisha Ahmed and Yassir Makkawi

Energies 2025, 18(22), 5919; https://doi.org/10.3390/en18225919 - 10 Nov 2025

Cited by 3 | Viewed by 3078

Abstract

Biorefineries offer a sustainable approach to producing fuels, chemicals, food, and feed from biomass, presenting a viable strategy for mitigating greenhouse gas (GHG) emissions and reducing reliance on fossil fuels. This review provides a comprehensive overview of the biorefinery concept, with a particular focus on its integrated conversion processes, classification pathways, and the potential for retrofitting existing fossil fuel refineries. Emphasis is placed on the Gulf Cooperation Council (GCC) region, home to some of the world’s largest hydrocarbon processing infrastructures, as a strategic case study for deploying biorefinery technologies. This review presents the latest trends in integrated biorefinery configurations and the potential for upgrading to drop-in fuels. It examines conventional biorefineries in the GCC, outlines their processing capacities, and explores suitable biomass feedstocks that thrive under the region’s high-temperature and high-salinity conditions. By highlighting both technological advancements and regional opportunities, this study underscores the potential for leveraging existing infrastructure in oil-rich nations to facilitate the transition toward sustainable bioenergy systems. Full article

(This article belongs to the Special Issue Advanced Bioenergy, Biomass and Waste Conversion Technologies: 2nd Edition)

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