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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: closed (15 January 2021) | Viewed by 32069

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Prof. Dr. Prasad Kaparaju

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Griffith School of Engineering and Built Environment, Griffith University, Nathan Campus, Nathan, QLD 4111, Australia
Interests: biomass; biomass conversion; biofuel; biogas; biohydrogen; environmental biotechnology; renewable energy technologies; anaerobic digestion
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Special Issue Information

Dear colleagues,

Biomass from agriculture, agro-industry, and municipality is considered a renewable and sustainable energy resource that can be used to produce renewable electricity, bioenergy, transportation fuels (biofuels), and/or high value functional chemicals. Biomass conversion technologies, such as involving combustion, thermochemical, electrochemical, or biochemical pathways, can be used to convert biomass into alternative solid energy sources (charcoal, biochar, and RDF), liquid biofuels (biodiesel, algal biofuel, bioethanol, pyrolysis, and liquefaction bio-oils), and gaseous fuels (biogas, syngas, and biohydrogen). The produced bioenergy can complement other renewables, such as solar and wind energy, and facilitate meeting targets of renewable energy and greenhouse gas emission reduction. Therefore, advanced and innovative biomass conversion technologies play a crucial role in renewable energy development and the replacement of fossil fuels and chemicals in achieving environmental sustainability. This Special Issue aims to publish a comprehensive overview and in-depth technical research papers addressing the recent progress in biomass conversion technologies and processes. Studies of advanced technologies and methods for bioenergy, biorefinery, and biofuel production are also welcomed. Research involving experimental and numerical studies, recent developments, and the current state of the art and emerging technologies in this field are highly encouraged.

Dr. Prasad Kaparaju
Guest Editor

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Keywords

biomass
biofuel
bioenergy
biorefinery
chemicals
physical conversion
thermochemical conversion
chemical conversion
biological conversion
process optimization
process design
thermodynamic analysis
gasification process
process modeling

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Published Papers (10 papers)

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23 pages, 4403 KiB

Open AccessArticle

Fuel Cells Based on Natural Polysaccharides for Rail Vehicle Application

by Paweł Daszkiewicz, Beata Kurc, Marita Pigłowska and Maciej Andrzejewski

Energies 2021, 14(4), 1144; https://doi.org/10.3390/en14041144 - 21 Feb 2021

Cited by 7 | Viewed by 2733

Abstract

This manuscript shows the use of natural polysaccharides such as starch and cellulose as a carbon source for fuel cells. To achieve this, two innovative methods of obtaining hydrogen have been shown: by adsorption and by enzyme. The carbonization path of the material results in excellent sorption properties and allows gas with high efficiency to be obtained. The enzymatic method for the degradation of the compound is more expensive because specific enzymes (such as laccase, tyrosinase) must be used, but it allows greater control of the properties of the obtained material. A scientific novelty is the use of natural raw materials, the use of which increases the biodegradability of the electrochemical system and also reduces the cost of raw materials and increases the range of their acquisition. Energy should be generated where it is used. Another goal is decentralization, and thanks to the proposed solutions, hydrogen cells represent an innovative alternative to today’s energy giants—also for independent power supply to households. The proposed harvesting paths are intended to drive rail vehicles in order to reduce emissions and secondary pollution of the environment. The goals of both methods were easy recycling, high efficiency, increased environmental friendliness, low cost and a short hydrogen production path. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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14 pages, 1921 KiB

Open AccessArticle

The Impact of Particles Comminution on Mechanical Durability of Wheat Straw Briquettes

by Arkadiusz Dyjakon, Łukasz Sobol, Mateusz Krotowski, Krzysztof Mudryk and Krzysztof Kawa

Energies 2020, 13(23), 6186; https://doi.org/10.3390/en13236186 - 25 Nov 2020

Cited by 12 | Viewed by 2531

Abstract

Briquetting is one of the recommended biomass agglomeration processes. The material subjected to briquetting gains valuable functional features related to higher energy density, appropriate moisture content, and increased bulk density. However, the briquettes need high mechanical durability to maintain high quality during transportation, loading, and other logistic steps before they will be delivered to the final consumer and utilized for energy purposes. The mechanical durability depends on many factors, including the particles comminution of the compacted biomass. Therefore, the aim of this study was to analyze the impact of particle comminution on the mechanical durability of wheat straw briquettes. The research was carried out in accordance with the international standard for solid biofuels PN-EN ISO 17831-1:2016-02. The briquettes were produced from three different fractions: 0–2 mm, 2–15 mm, and 15–45 mm. To obtain more data related to the mechanical durability of briquettes, the tests were also carried out outside the ISO standard conditions. During the investigations, the working chamber operation time was extended from 5 to 60 min, and the rotational speed of the working chamber was increased to 25 and 30 rpm, respectively. The results indicated that the mechanical durability index (Du) of briquettes decreases along with the increase in the particle size. According to the PN-EN ISO 17831-1:2016-02 standard, the highest mechanical durability was achieved for the 0–2 mm fraction (Du = 91.17%) followed by the 2–15 mm fraction (Du = 88.12%), and the lowest was achieved for the 15–45 mm fraction (Du = 84.48%). It was noticed that the increase in the working chamber operation time resulted in a decrease of the Du value. Moreover, the difference in mechanical durability (between t₅ = 5 min and t₆₀ = 60 min) was greater for a larger fraction (∆Du = 16.26% for 0–2 mm fraction, ∆Du = 21.04% for 2–15 mm fraction, and ∆Du = 23.43% for 15–45 mm fraction). It was also observed that the increase of the rotational speed of the working chamber caused a slight decrease in the value of the mechanical durability of briquettes for all investigated fractions. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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20 pages, 7805 KiB

Open AccessArticle

Comparison of Torrefaction and Hydrothermal Treatment as Pretreatment Technologies for Rice Husks

by Tianjiao Cheng, Andante Hadi Pandyaswargo and Hiroshi Onoda

Energies 2020, 13(19), 5158; https://doi.org/10.3390/en13195158 - 3 Oct 2020

Cited by 4 | Viewed by 2310

Abstract

Many agricultural waste residues are generated in Southeast Asia while some areas in the region still do not have electricity. This study explores the potential effective utilization of agricultural residues in Southeast Asia to generate power. Firstly, visualization of the potential for energy generation was completed using a geographic information system (GIS). Secondly, a comparison of effectiveness was completed between the torrefaction and hydrothermal treatment of low-grade agricultural residues as pretreatment techniques for the modification of agricultural residues. In this study, the feasibility of utilizing rice residues was analyzed (i.e., rice husks, which are produced in large quantities in Southeast Asia) to determine their suitability for pretreatment as feedstock for power plants. This was assessed experimentally by focusing on the pyrolytic characteristics of the husks and the rate of ash change both before and after treatment, while the subsequent implications on transportation costs were also noted. The results indicated that the percentage of ash in torrefied rice husks was 26.7%, whereas the percentages of ash in rice husks that were treated with water or an NaOH solution were 13.96% and 8.87%, respectively. The reduction in transportation costs after compression was 90.8% for hydrothermal treatment and 88.7% for torrefaction. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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18 pages, 4361 KiB

Open AccessArticle

Dehydration Leads to Hydrocarbon Gas Formation in Thermal Degradation of Gas-Phase Polyalcohols

by Asuka Fukutome and Haruo Kawamoto

Energies 2020, 13(14), 3726; https://doi.org/10.3390/en13143726 - 20 Jul 2020

Cited by 2 | Viewed by 2808

Abstract

To understand the molecular mechanisms of hydrocarbon gas formation in biomass gasification, gasification of simple polyalcohols (glycerol, propylene glycol, and ethylene glycol) were studied at 400, 600, and 800 °C (residence times: 0.9–1.4 s) from the viewpoint of dehydration reactions that form aldehydes with various substituents as intermediates to produce hydrocarbon gases. The results were also compared with those of glyceraldehyde and dihydroxyacetone, which are reported to produce syngas (H₂ and CO) selectively. All polyalcohols became reactive at 600 °C to form condensable products in 15.7–24.7% yields (C-based), corresponding to 33.9–38.4% based on the amounts of reacted polyalcohols. These condensable products, mostly aldehydes, act as gas-forming intermediates, because the polyalcohols were completely gasified at 800 °C (hydrocarbon gas contents: 20.3–35.3%, C-based). Yields of the intermediates bearing alkyl groups at 600 °C were proportionally correlated to the yields of hydrocarbon gases at 800 °C, suggesting that the alkyl groups are further converted into hydrocarbon gases via the fragmentation of acyl radicals. Dehydration reactions were suggested to occur in both heterolytic and radical mechanisms by theoretical calculations. Glyceraldehyde tended to fragment directly into CO and H₂, instead of forming a dehydration intermediate. These results are informative for controlling the product gas composition in biomass gasification. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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15 pages, 2768 KiB

Open AccessArticle

Methane Oxidation Efficiency in Biofiltration Systems with Different Moisture Content Treating Diluted Landfill Gas

by Niccolò Frasi, Elena Rossi, Isabella Pecorini and Renato Iannelli

Energies 2020, 13(11), 2872; https://doi.org/10.3390/en13112872 - 4 Jun 2020

Cited by 8 | Viewed by 2715

Abstract

This study investigates the influence of moisture content on the potential oxidation efficiency of methane (CH₄) of biofiltration systems treating landfill gas containing high oxygen concentrations. Column tests filled with compost with different moisture contents (20%, 30%, and 40%) loaded with different methane flows were set up on a laboratory scale. Analyzing the results the following evidences can be summarized: With low methane load (<100 g CH₄ m⁻² d⁻¹), a moisture content of 20% was not enough to support bacterial activity, while a moisture content of 40% advantaged the compost respiration assisting it to become the dominating process; with higher methane load (100–300 g CH₄ m⁻² d⁻¹), a moisture content of 30% resulted in an optimal value to support methanotrophic activity showing the highest CH₄ concentration reduction; moving on to a CH₄ load above 300 g CH₄ m⁻² d⁻¹, the inhibition of methanotrophic activity emerged independently to the moisture content of the filter media. The optimal configuration is obtained for a moisture content of 30% and in the case of flows below 200 g CH₄ m⁻² d⁻¹ for which the oxidation efficiency results higher than 80%. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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12 pages, 2057 KiB

Open AccessArticle

Hyperthermophilic Treatment of Grass and Leaves to Produce Hydrogen, Methane and VFA-Rich Digestate: Preliminary Results

by Przemysław Liczbiński and Sebastian Borowski

Energies 2020, 13(11), 2814; https://doi.org/10.3390/en13112814 - 2 Jun 2020

Cited by 4 | Viewed by 2228

Abstract

In this study, the feasibility of hydrogen and methane production from grass and leaves via hyperthermophilic anaerobic digestion was investigated. The hyperthermophilic treatment of grass at 70 °C resulted in the highest concentrations of volatile fatty acids (TVFA) and reducing sugars in the supernatant of over 21 and 6.5 g/L reported on day 3 and 4 of the experiment. In contrast, hydrolysis and acidification of leaves performed slower and with lower efficiency, as the peak concentrations of TVFA and reducing sugars were observed at the end of the process. However, the highest cumulative hydrogen and methane yields of 69.64 mLH₂/gVS and 38.63 mLCH₄/gVS were reported for leaves digested at 70 °C, whereas the corresponding maximum productions observed for grass were 50 mLH₂/gVS and 1.98 mLCH₄/gVS, respectively. A temperature increase to 80 °C hampered hydrogen and methane production and also resulted in lower yields of volatile fatty acids, reducing sugars and ammonia as compared to the corresponding values reported for 70 °C. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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18 pages, 2443 KiB

Open AccessArticle

Energy Efficiency of Comminution and Extrusion of Maize Substrates Subjected to Methane Fermentation

by Kamil Witaszek, Krzysztof Pilarski, Gniewko Niedbała, Agnieszka Anna Pilarska and Marcin Herkowiak

Energies 2020, 13(8), 1887; https://doi.org/10.3390/en13081887 - 13 Apr 2020

Cited by 19 | Viewed by 2718

Abstract

The production of methane in the anaerobic digestion process is a proven technology, but it is characterized by low cost-effectiveness. The pretreatment of substrates seems to be a promising technology, which may increase the cost-effectiveness of biogas installations. The aim of the study was to investigate the influence of the comminution and extrusion of maize silage and maize straw silage on the course and yield of anaerobic digestion. The use of a pretreatment (comminution, extrusion) is justified when its energy balance is positive. The greatest increase in the methane yield per dry matter (12.4%) was observed after the extrusion of maize straw silage at 175 °C. The change in the methane yield resulting from the extrusion of maize silage and maize straw silage at 150 °C was small and amounted to 6.4% and 9%, respectively. The comminution caused an increase in the methane yield and accelerated the fermentation of substrates. The methane yield from maize silage was 38.4%, whereas the yield from maize straw silage was only 8.3%. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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12 pages, 1212 KiB

Open AccessArticle

One-Step or Two-Step Acid/Alkaline Pretreatments to Improve Enzymatic Hydrolysis and Sugar Recovery from Arundo Donax L.

by Shangyuan Tang, Yushen Cao, Chunming Xu, Yue Wu, Lingci Li, Peng Ye, Ying Luo, Yifan Gao, Yonghong Liao, Qiong Yan and Xiyu Cheng

Energies 2020, 13(4), 948; https://doi.org/10.3390/en13040948 - 20 Feb 2020

Cited by 4 | Viewed by 2455

Abstract

Energy crops are not easily converted by microorganisms because of their recalcitrance. This necessitates a pretreatment to improve their biodigestibility. The effects of different pretreatments, as well as their combination on the enzymatic digestibility of Arundo donax L. were systematically investigated to evaluate its potential for bioconversion. Dilute alkaline pretreatment (ALP) using 1.2% NaOH at 120 °C for 30 min resulted in the highest reducing sugar yield in the enzymatic hydrolysis process because of its strong delignification and morphological modification, while ferric chloride pretreatment (FP) was effective in removing hemicellulose and recovering soluble sugars in the pretreatment stage. Furthermore, an efficient two-step ferric chloride-alkaline pretreatment (FALP) was successfully developed. In the first FP step, easily degradable cellulosic components, especially hemicellulose, were dissolved and then effectively recovered as soluble sugars. Subsequently, the FP sample was further treated in the second ALP step to remove lignin to enhance the enzymatic hydrolysis of the hardly degradable cellulose. As a result, the integrated two-step process obtained the highest total sugar yield of 420.4 mg/g raw stalk in the whole pretreatment and enzymatic hydrolysis process; hence, the process is a valuable candidate for biofuel production. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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23 pages, 2107 KiB

Open AccessArticle

Use of Co-Solvents in Hydrothermal Liquefaction (HTL) of Microalgae

by Yang Han, Kent Hoekman, Umakanta Jena and Probir Das

Energies 2020, 13(1), 124; https://doi.org/10.3390/en13010124 - 25 Dec 2019

Cited by 22 | Viewed by 5832

Abstract

This study reviewed and summarized the literature regarding the use of alcohols during hydrothermal liquefaction (HTL) of algal biomass feedstocks. The use of both pure alcohols and alcohol-water co-solvents were considered. Based upon this review, laboratory experiments were conducted to investigate the impacts of different alcohol co-solvents (ethanol, isopropanol, ethylene glycol, and glycerol) on the HTL treatment of a specific saltwater microalga (Tetraselmis sp.) at two temperatures: 300 °C and 350 °C. Based on their performance, two co-solvents, isopropanol and ethylene glycol, were selected to explore the effects of varying solvent concentrations and reaction temperatures on product yields and biocrude properties. The type and amount of added alcohol did not significantly affect the biocrude yield or composition. Biocrude yields were in the range of 30–35%, while a nearly constant yield of 21% insoluble products was observed, largely resulting from ash constituents within the algal feedstock. The benefits of using alcohol co-solvents (especially isopropanol) were the reduced viscosity of the biocrude products and reduced rates of viscosity increase with biocrude aging. These effects were attributed mainly to the physical properties of the co-solvent mixtures (solubility, polarity, density, etc.) rather than chemical processes. Under the reaction conditions used, there was no evidence that the co-solvents participated in biocrude production by means of hydrogen donation or other chemical processes. Recovery and recycling of the co-solvent present various challenges, depending upon the type and amount of the co-solvent that is used. For example, glycol solvents are recovered nearly completely within the aqueous product stream, whereas simple alcohols are partitioned between the biocrude and aqueous product streams. In commercial applications, the slight benefits provided by the use of co-solvents must be balanced by the challenges of co-solvent recovery and recycling. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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13 pages, 3382 KiB

Open AccessCase Report

An Analysis of the Current Status of Woody Biomass Gasification Power Generation in Japan

by Yasutsugu Baba, Andante Hadi Pandyaswargo and Hiroshi Onoda

Energies 2020, 13(18), 4903; https://doi.org/10.3390/en13184903 - 18 Sep 2020

Cited by 10 | Viewed by 3806

Abstract

Forests cover two-thirds of Japan’s land area, and woody biomass is attracting attention as one of the most promising renewable energy sources in the country. The Feed-in Tariff (FIT) Act came into effect in 2012, and since then, woody biomass power generation has spread rapidly. Gasification power generation, which can generate electricity on a relatively small scale, has attracted a lot of attention. However, the technical issues of this technology remain poorly defined. This paper aims to clarify the problems of woody biomass gasification power generation in Japan, specifically on the challenges of improving energy utilization rate, the problem of controlling the moisture content, and the different performance of power generation facilities that uses different tree species. We also describe the technological development of a 2 MW updraft reactor for gasification and bio-oil coproduction to improve the energy utilization rate. The lower heating value of bio-oil, which was obtained in the experiment, was found to be about 70% of A-fuel oil. Among the results, the importance of controlling the moisture content of wood chips is identified from the measurement evaluation of a 0.36 MW-scale downdraft gasifier’s actual operation. We discuss the effects of tree species variation and ash on gasification power generation based on the results of pyrolysis analysis, industry analysis for each tree species. These results indicate the necessity of building a system specifically suited to Japan’s climate and forestry industry to allow woody biomass gasification power generation to become widespread in Japan. Full article

(This article belongs to the Special Issue Biomass Conversion Technologies)

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