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Special Issue "BioEnergy and BioChemicals Production from Biomass and Residual Resources"

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

Deadline for manuscript submissions: closed (15 April 2018)

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Guest Editor
Dr. Dimitar Karakashev

Aalborg University, Copenhagen campus, Denmark
Website | E-Mail
Interests: biofuels; biorefinery; biotechnology; microorganisms
Guest Editor
Dr. Yifeng Zhang

Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Website | E-Mail
Interests: microbial electrochemistry; biogeochemical cycles; gas fermentation and anaerobic digestion

Special Issue Information

Dear Colleagues,

We are inviting submissions to a Special Issue of Energies entitled “BioEnergy and BioChemicals Production from Biomass and Residual Resources”.

Research and technology developments in bioenergy and biochemical production systems are of utmost important for the development of next generation, high efficient biomass conversion concepts maximizing total energy and chemicals output. Utilization of non- conventional biomasses and unexploited residual resources (e.g., aquatic feedstocks, exhaust and industrial flue gases), innovative solutions for online monitoring and process control, novel biochemical pathways, microbial platforms and reactor technologies is a key issue to be addressed.

However, major challenges have still to be solved, such as the design of high performance and cost-effective technologies for production of bioenergy (gaseous, liquid, sold biofuels, renewable electricity) and biochemicals from residual resources in a biorefinery concept, where the potential of the biomass and residual waste streams is fully valorized.

In this context, evaluation of the environmental, technological, economical, and social sustainability of the concepts developed are of utmost importance.

The main objective of this Special Issue is, hence, to provide cost- effective and technologically sound solutions for next generation bioenergy and biochemical production systems.

The particular topics of interest include, but are not limited to:

  • Novel and un-exploited residual resources for next generation biorefineries
  • New emerging bioenergy and   biochemicals production technologies
  • Biochemicals pathways involved in biofuels and biochemicals production
  • Microbial ecology of the biomass conversion processes
  • Bioreactors for bioenergy and biochemicals production
  • Novel approaches for biosystems sustainability evaluation

Dr. Dimitar Karakashev
Dr. Yifeng Zhang
Guest Editors

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 papers will be 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 100 words) can be sent to the Editorial Office for announcement on this website.

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 1800 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

  • Non- conventional residual resources for a bioeconomy
  • Emerging technologies for bioenergy and biochemicals production
  • Liquid, gaseous and solid biofuels
  • Microbial electrochemistry
  • Biorefineries
  • Sustainability assessment of bioenergy and biochemicals production

Published Papers (22 papers)

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Editorial

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Open AccessEditorial BioEnergy and BioChemicals Production from Biomass and Residual Resources
Energies 2018, 11(8), 2125; https://doi.org/10.3390/en11082125
Received: 17 July 2018 / Revised: 11 August 2018 / Accepted: 13 August 2018 / Published: 15 August 2018
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Research

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Open AccessArticle Performance Evaluation of Mesophilic Anaerobic Digestion of Chicken Manure with Algal Digestate
Energies 2018, 11(7), 1829; https://doi.org/10.3390/en11071829
Received: 4 June 2018 / Revised: 26 June 2018 / Accepted: 27 June 2018 / Published: 12 July 2018
Cited by 2 | PDF Full-text (1966 KB) | HTML Full-text | XML Full-text
Abstract
Dilution is considered to be a fast and easily applicable pretreatment for anaerobic digestion (AD) of chicken manure (CM), however, dilution with fresh water is uneconomical because of the water consumption. The present investigation was targeted at evaluating the feasibility and process performance [...] Read more.
Dilution is considered to be a fast and easily applicable pretreatment for anaerobic digestion (AD) of chicken manure (CM), however, dilution with fresh water is uneconomical because of the water consumption. The present investigation was targeted at evaluating the feasibility and process performance of AD of CM diluted with algal digestate water (AW) for methane production to replace tap water (TW). Moreover, the kinetics parameters and mass flow of the AD process were also comparatively analyzed. The highest methane production of diluted CM (104.39 mL/g volatile solid (VS)) was achieved with AW under a substrate concentration of 8% total solid (TS). The result was markedly higher in comparison with the group with TW (79.54–93.82 mL/gVS). Apart from the methane production, considering its energy and resource saving, nearly 20% of TW replaced by AW, it was promising substitution to use AW for TW to dilute CM. However, the process was susceptible to substrate concentration, inoculum, as well as total ammonia and free ammonia concentration. Full article
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Open AccessArticle Fly Ash Formation and Characteristics from (co-)Combustion of an Herbaceous Biomass and a Greek Lignite (Low-Rank Coal) in a Pulverized Fuel Pilot-Scale Test Facility
Energies 2018, 11(6), 1581; https://doi.org/10.3390/en11061581
Received: 1 May 2018 / Revised: 23 May 2018 / Accepted: 5 June 2018 / Published: 15 June 2018
Cited by 2 | PDF Full-text (4905 KB) | HTML Full-text | XML Full-text
Abstract
The lignite boilers are designed for lower quality fuels, and often the ash is not utilized. This work assessed the impact of combustion of an herbaceous biomass with a low-quality Greek lignite on the quality of the resulting fly ash. Test results were [...] Read more.
The lignite boilers are designed for lower quality fuels, and often the ash is not utilized. This work assessed the impact of combustion of an herbaceous biomass with a low-quality Greek lignite on the quality of the resulting fly ash. Test results were compared with those of fly ash samples from an industrial facility using the same fuel qualities. Inductively coupled plasma-optical (ICP) emission spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscope (SEM) analyses were performed on the collected samples. Despite the significantly higher contents of K, Na and S in the biomass, at a 50% co-firing thermal share, the major and minor oxides in the fly ash were comparable to the lignite fly ash quality. This is attributed to the high ash content of the lignite, the low ash content of the biomass, and the much higher heating value of the biomass. There were improvements in fly ash performance characteristics with the herbaceous biomass in the fuel blend. The initial setting time and volume stability evaluations were improved with the biomass in the fuel blend. The work supports efforts of good practices in ash management, social responsibility, a circular economy, power plant renewable energy operations, and co-firing herbaceous biomass fuels in lignite power plants. Full article
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Open AccessArticle Increasing Profits in Food Waste Biorefinery—A Techno-Economic Analysis
Energies 2018, 11(6), 1551; https://doi.org/10.3390/en11061551
Received: 7 May 2018 / Revised: 20 May 2018 / Accepted: 21 May 2018 / Published: 13 June 2018
Cited by 5 | PDF Full-text (2331 KB) | HTML Full-text | XML Full-text
Abstract
The present manuscript highlights the economic profit increase when combining organic waste anaerobic digestion with other mixed culture anaerobic fermentation technologies, e.g., lactic acid fermentation and dark fermentation. Here we consider the conversion of 50 tonnes/day of food waste into methane, power generation [...] Read more.
The present manuscript highlights the economic profit increase when combining organic waste anaerobic digestion with other mixed culture anaerobic fermentation technologies, e.g., lactic acid fermentation and dark fermentation. Here we consider the conversion of 50 tonnes/day of food waste into methane, power generation (from CHP of biomethane), lactic acid, polylactic acid, hydrogen, acetic acid and butyric acid. The economic assessment shows that the basic alternative, i.e., anaerobic digestion with methane selling to the grid, generates 19 USD/t_VS (3 USD/t_foodwaste) of profit. The highest profit is obtained by dark fermentation with separation and purification of acetic and butyric acids, i.e., 296 USD/t_VS (47 USD/t_foodwaste). The only alternative that presented losses is the power generation alternative, needing tipping fees and/or subsidy of 176 USD/t_VS (29 USD/t_foodwaste). The rest of the alternatives generate profit. From the return on investment (ROI) and payback time, the best scenario is the production of polylactic acid, with 98% ROI, and 7.8 years payback time. Production of butyric acid ROI and payback time was 74% and 9.1 years. Full article
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Open AccessFeature PaperArticle An Assessment of the Sustainability of Lignocellulosic Bioethanol Production from Wastes in Iceland
Energies 2018, 11(6), 1493; https://doi.org/10.3390/en11061493
Received: 30 April 2018 / Revised: 3 June 2018 / Accepted: 4 June 2018 / Published: 7 June 2018
Cited by 3 | PDF Full-text (3931 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the development of a model to comprehensively assess the sustainability impacts of producing lignocellulosic bioethanol from various types of municipal organic wastes (MOWs) in Iceland: paper and paperboard, timber and wood and garden waste. The tool integrates significant economic, energy, [...] Read more.
This paper describes the development of a model to comprehensively assess the sustainability impacts of producing lignocellulosic bioethanol from various types of municipal organic wastes (MOWs) in Iceland: paper and paperboard, timber and wood and garden waste. The tool integrates significant economic, energy, environmental and technical aspects to analyse and rank twelve systems using the most common pretreatment technologies: dilute acid, dilute alkali, hot water and steam explosion. The results show that among the MOWs, paper and paperboard have higher positive rankings under most assessments. Steam explosion is also ranked at the top from the economic, energy and environmental perspectives, followed by the hot water method for paper and timber wastes. Finally, a potential evaluation of total wastes and bioethanol production in Iceland is carried out. The results show that the average production of lignocellulosic bioethanol in 2015 could be 12.5, 11 and 3 thousand tons from paper, timber and garden wastes, respectively, and that production could reach about 15.9, 13.7 and 3.7 thousand tons, respectively, by 2030. Full article
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Open AccessArticle Methodical Aspects of Biogas Production in Small-Volume Bioreactors in Laboratory Investigations
Energies 2018, 11(6), 1378; https://doi.org/10.3390/en11061378
Received: 27 April 2018 / Revised: 22 May 2018 / Accepted: 25 May 2018 / Published: 29 May 2018
Cited by 2 | PDF Full-text (1153 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this study was to develop a methodology to investigate the biofermentation process in small-volume fermenters. Dark serum bottles with a volume of 100–120 mL, tightly sealed with a rubber septum, were used as bioreactors. The optimum measurement conditions in this [...] Read more.
The aim of this study was to develop a methodology to investigate the biofermentation process in small-volume fermenters. Dark serum bottles with a volume of 100–120 mL, tightly sealed with a rubber septum, were used as bioreactors. The optimum measurement conditions in this type of bioreactor comprise: (i) filling two-thirds of the maximum volume with a suspension; (ii) a 2% bioreactor loading (on a dry basis) and; (iii) the daily equalization of pressure by removing the biogas through the septum pierced with a syringe needle and the intensive mixing of the remaining suspension. The methane yield (quantity and dynamics) obtained in this type of bioreactor is analogous to that of industrial bioreactors or large-scale laboratory bioreactors. The use of small-volume bioreactors that can be incubated will facilitate the preliminary selection of analysed systems and provide an indication of those that should be investigated in large-scale bioreactors. Full article
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Open AccessArticle Gasification of Agroresidues for Syngas Production
Energies 2018, 11(5), 1280; https://doi.org/10.3390/en11051280
Received: 13 April 2018 / Revised: 14 May 2018 / Accepted: 14 May 2018 / Published: 17 May 2018
Cited by 1 | PDF Full-text (6839 KB) | HTML Full-text | XML Full-text
Abstract
Biomass residues from agriculture and agroindustry are suitable sources for the production of energy because they don’t compete with the food chain and they are produced cheaply. Their transformation into heat and power or energy vectors depends on morphology and composition. Shells of [...] Read more.
Biomass residues from agriculture and agroindustry are suitable sources for the production of energy because they don’t compete with the food chain and they are produced cheaply. Their transformation into heat and power or energy vectors depends on morphology and composition. Shells of almonds and hazelnuts can be easily gasified in fixed beds because of their low fines content and high gas permeation. In this work we investigated the overall process performances and syngas composition, especially the H2/CO ratio, by changing the air and steam supply. The tests were carried out in a pilot updraft gasifier having a capacity of treating up to 20–30 kg/h of biomass. Experimental data were worked out by surface response analysis as function of the equivalence ratios (ER) in relation to the complete combustion and water reaction. By using only air at ER(O2) 0.24 the ratio H2/CO in the syngas was 0.33 while adding steam at ER(H2O) 0.28 the ratio reached a value of 1.0. The energy conversion efficiency from solid to gas and oils reached maximum values of 76% and 28%, respectively. As anticipated by TGA, hazelnut shells produced less organic volatiles and gas efficiency was generally higher than for almond shells. Full article
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Open AccessArticle Economic Analysis of Pellet Production in Co-Digestion Biogas Plants
Energies 2018, 11(5), 1135; https://doi.org/10.3390/en11051135
Received: 30 March 2018 / Revised: 19 April 2018 / Accepted: 26 April 2018 / Published: 3 May 2018
Cited by 1 | PDF Full-text (969 KB) | HTML Full-text | XML Full-text
Abstract
In our paper we examine the economics of a technological process which utilizes the separated biogas plant digestate as the primary material and, as auxiliary material, the waste heat produced by the cogeneration process, to produce a marketable pellet which can be used [...] Read more.
In our paper we examine the economics of a technological process which utilizes the separated biogas plant digestate as the primary material and, as auxiliary material, the waste heat produced by the cogeneration process, to produce a marketable pellet which can be used in two ways (to supply soil nutrients and heat energy). Using multivariate linear regression model we developed an equation for the biogas yield from the modelled production recipe and expected nutrient pellet prices, and sensitivity analysis were also performed for the substrate dry matter content. We found that pellets can be produced at a cost of 88–90 EUR/ton with a 6 to 10% dry matter substrate content and that, primarily, sales of pellets for heating justify pelleting; producer’s own use and use for nutrient purposes can only be justified in exceptional cases. In the case of dry solid content above 5%, the process does not require the total amount of waste heat; some of this can be used to cover other heat requirements. Full article
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Open AccessArticle The Effect of Temperature on the Methanogenic Activity in Relation to Micronutrient Availability
Energies 2018, 11(5), 1057; https://doi.org/10.3390/en11051057
Received: 6 April 2018 / Revised: 23 April 2018 / Accepted: 23 April 2018 / Published: 25 April 2018
Cited by 3 | PDF Full-text (7029 KB) | HTML Full-text | XML Full-text
Abstract
In the view of microbial community, thermophilic microorganisms were reported to have faster biochemical reaction rates, which are reflected by a higher methane production rate. However, there has no research to discuss the effect of temperature on methanogenic activity in relation to micronutrient [...] Read more.
In the view of microbial community, thermophilic microorganisms were reported to have faster biochemical reaction rates, which are reflected by a higher methane production rate. However, there has no research to discuss the effect of temperature on methanogenic activity in relation to micronutrient transport and availability. The objective of this study was to investigate the effect of temperature on methanogenic activity in relation to nutrient uptakes, micronutrient transports, and mass balance using anaerobic sequencing batch reactors (ASBR) with recycled biogas for treating ethanol wastewater at mesophilic (37 °C) and thermophilic (55 °C) temperatures. The increase in temperature from 37 to 55 °C increased in both of the optimum chemical oxygen demand (COD) loading rate and methanogenic activity, corresponding to the results of N and P uptakes, energy balance, and mass balance. The higher temperature of the thermophilic operation as compared to the mesophilic one caused a lower water solubility of the produced H2S, leading to lowering the reduction of divalent cation micronutrients. The thermophilic operation could prevent the deficit of micronutrients, thus causing a higher methanogenic activity, while the mesophilic operation still had the deficit of most micronutrients, leading to the lower activity. Full article
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Open AccessArticle Digestion Performance and Microbial Metabolic Mechanism in Thermophilic and Mesophilic Anaerobic Digesters Exposed to Elevated Loadings of Organic Fraction of Municipal Solid Waste
Energies 2018, 11(4), 952; https://doi.org/10.3390/en11040952
Received: 8 February 2018 / Revised: 14 March 2018 / Accepted: 20 March 2018 / Published: 17 April 2018
Cited by 4 | PDF Full-text (4991 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Mesophilic and thermophilic anaerobic digestion reactors (MR and TR) for the organic fraction of municipal solid waste (OFMSW) were tested to reveal the differential microbial responses to increasing organic loading rate (OLR). MR exhibited faster adaptation and better performance at an OLR range [...] Read more.
Mesophilic and thermophilic anaerobic digestion reactors (MR and TR) for the organic fraction of municipal solid waste (OFMSW) were tested to reveal the differential microbial responses to increasing organic loading rate (OLR). MR exhibited faster adaptation and better performance at an OLR range of 1.0–2.5 g VS·L−1·d−1, with average profiles of a biogas yield of 0.38 L/gVSadded*d at 0.5 g/L*d OLR and 0.69 L/gVSadded*d at 2.5 g/L*d OLR, whereas TR had a biogas yield of 0.07 L/gVSadded*d at 0.5 g/L*d OLR and 0.44 L/gVSadded*d at 2.5 g/L*d OLR. The pyrosequencing results of amplicons revealed the microbial mechanisms of OFMSW anaerobic digestion. Larger shifts in the bacteria composition were observed in the TR with OLR elevation. For methanogens in both reactors, Methanothrix dominated in the MR while Methanosarcina was favored in the TR. Moreover, analysis of the mode and efficiency of metabolism between the MR and TR demonstrated different performances with more efficiency related to the limiting hydrolytic acid step. Full article
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Open AccessArticle Application of Rumen Microorganisms for Enhancing Biogas Production of Corn Straw and Livestock Manure in a Pilot-Scale Anaerobic Digestion System: Performance and Microbial Community Analysis
Energies 2018, 11(4), 920; https://doi.org/10.3390/en11040920
Received: 20 March 2018 / Revised: 8 April 2018 / Accepted: 9 April 2018 / Published: 13 April 2018
Cited by 1 | PDF Full-text (5210 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This study aimed to assess the feasibility of rumen microorganisms inoculated in a modified pilot-scale system for enhancing biogas production of (1) solely corn straw (CS) and (2) CS with livestock manure under different solid contents and mixture ratios. The biogas liquid was [...] Read more.
This study aimed to assess the feasibility of rumen microorganisms inoculated in a modified pilot-scale system for enhancing biogas production of (1) solely corn straw (CS) and (2) CS with livestock manure under different solid contents and mixture ratios. The biogas liquid was proven to pretreat CS at this scale. The digestion system was started up within 32 days at a retention time of 20 days. The rumen culture was found to have a positive response to the impact on temperature and pH. The optimal solid content of CS was detected to be 3%, resulting in a stable biogas yield of 395 L kg−1·total solid (TS)−1. A higher biogas yield of 400 L kg−1·TS−1 – 420 L kg−1·TS−1 was achieved at a solid content of 10% organic loading rate (OLR, 4.42 kg volatile solid (VS) m−3·d−1) in co-digestion systems with CS and livestock manure. The methane content could be maintained at about 60%. Hydrogenotrophic methanogens were dominated by Methanobacterium in the solely CS digestion system, and two methanogenetic pathways, including hydrogenotrophic and acetoclastic methanogens by Methanosarcina and Methanobacterium, co-occurred for methane production during the co-digestion of CS with pig manure (PM). This study indicates that rumen microbes could be utilized in a pilot-scale digestion system and that they greatly promoted the biogas yield. Full article
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Open AccessArticle Utilization of Energy Crops and Sewage Sludge in the Process of Co-Gasification for Sustainable Hydrogen Production
Energies 2018, 11(4), 809; https://doi.org/10.3390/en11040809
Received: 28 February 2018 / Revised: 15 March 2018 / Accepted: 29 March 2018 / Published: 31 March 2018
Cited by 3 | PDF Full-text (971 KB) | HTML Full-text | XML Full-text
Abstract
The increasing world energy demand driven by economic growth and technical development contributes to the severe depletion of conventional energy resources and various environmental issues. The need for the employment of low-emission, highly efficient technologies of thermochemical conversion, flexible in terms of both [...] Read more.
The increasing world energy demand driven by economic growth and technical development contributes to the severe depletion of conventional energy resources and various environmental issues. The need for the employment of low-emission, highly efficient technologies of thermochemical conversion, flexible in terms of both raw resources and product applications is declared, when the utilization of solid, alternative fuels is considered. Gasification is the proven technology of lower unit emission of contaminants and higher efficiency than combustion systems, as well as versatile applicability of the synthesis gas, as its main product. While the conversion of fossil fuels in gasification systems is technically mature, the co-utilization of biomass and waste still requires research and optimization in various technical and economic aspects. In this paper, the results of experimental work on co-gasification of energy crops biomass and sewage sludge with steam to produce hydrogen-rich gas are presented. The process is performed at 700, 800 and 900 °C under atmospheric pressure. The experimental results are analyzed with the application of the Hierarchical Clustering Analysis. The optimal results in terms of hydrogen production in co-gasification of selected biomass and sewage sludge are observed for Helianthus tuberosus L. blends of 10% w/w of sewage sludge content at 900 °C. Full article
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Open AccessArticle Carbon Debt Payback Time for a Biomass Fired CHP Plant—A Case Study from Northern Europe
Energies 2018, 11(4), 807; https://doi.org/10.3390/en11040807
Received: 22 January 2018 / Revised: 20 March 2018 / Accepted: 23 March 2018 / Published: 31 March 2018
Cited by 2 | PDF Full-text (5471 KB) | HTML Full-text | XML Full-text
Abstract
The European Union (EU) has experienced a large increase in the use of biomass for energy in the last decades. In 2015, biomass used to generate electricity, heat, and to a limited extent, liquid fuels accounted for 51% of the EU’s renewable energy [...] Read more.
The European Union (EU) has experienced a large increase in the use of biomass for energy in the last decades. In 2015, biomass used to generate electricity, heat, and to a limited extent, liquid fuels accounted for 51% of the EU’s renewable energy production. Bioenergy use is expected to grow substantially to meet energy and climate targets for 2020 and beyond. This development has resulted in analyses suggesting the increased use of biomass for energy might initially lead to increased greenhouse gas (GHG) emissions to the atmosphere, a so-called carbon debt. Here, we analyze carbon debt and payback time of substituting coal with forest residues for combined heat and power generation (CHP). The analysis is, in contrast to most other studies, based on empirical data from a retrofit of a CHP plant in northern Europe. The results corroborate findings of a carbon debt, here 4.4 kg CO2eq GJ−1. The carbon debt has a payback time of one year after conversion, and furthermore, the results show that GHG emissions are reduced to 50% relative to continued coal combustion after about 12 years. The findings support the use of residue biomass for energy as an effective means for climate change mitigation. Full article
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Open AccessArticle Optimization and Scale-Up of Coffee Mucilage Fermentation for Ethanol Production
Energies 2018, 11(4), 786; https://doi.org/10.3390/en11040786
Received: 31 January 2018 / Revised: 5 March 2018 / Accepted: 5 March 2018 / Published: 29 March 2018
Cited by 2 | PDF Full-text (8088 KB) | HTML Full-text | XML Full-text
Abstract
Coffee, one of the most popular food commodities and beverage ingredients worldwide, is considered as a potential source for food industry and second-generation biofuel due to its various by-products, including mucilage, husk, skin (pericarp), parchment, silver-skin, and pulp, which can be produced during [...] Read more.
Coffee, one of the most popular food commodities and beverage ingredients worldwide, is considered as a potential source for food industry and second-generation biofuel due to its various by-products, including mucilage, husk, skin (pericarp), parchment, silver-skin, and pulp, which can be produced during the manufacturing process. A number of research studies have mainly investigated the valuable properties of brewed coffee (namely, beverage), functionalities, and its beneficial effects on cognitive and physical performances; however, other residual by-products of coffee, such as its mucilage, have rarely been studied. In this manuscript, the production of bioethanol from mucilage was performed both in shake flasks and 5 L bio-reactors. The use of coffee mucilage provided adequate fermentable sugars, primarily glucose with additional nutrient components, and it was directly fermented into ethanol using a Saccharomyces cerevisiae strain. The initial tests at the lab scale were evaluated using a two-level factorial experimental design, and the resulting optimal conditions were applied to further tests at the 5 L bio-reactor for scale up. The highest yields of flasks and 5 L bio-reactors were 0.46 g ethanol/g sugars, and 0.47 g ethanol/g sugars after 12 h, respectively, which were equal to 90% and 94% of the theoretically achievable conversion yield of ethanol. Full article
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Open AccessArticle Thermogravimetric, Devolatilization Rate, and Differential Scanning Calorimetry Analyses of Biomass of Tropical Plantation Species of Costa Rica Torrefied at Different Temperatures and Times
Energies 2018, 11(4), 696; https://doi.org/10.3390/en11040696
Received: 18 February 2018 / Revised: 16 March 2018 / Accepted: 19 March 2018 / Published: 21 March 2018
Cited by 2 | PDF Full-text (3310 KB) | HTML Full-text | XML Full-text
Abstract
We evaluated the thermogravimetric and devolatilization rates of hemicellulose and cellulose, and the calorimetric behavior of the torrefied biomass, of five tropical woody species (Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis and Vochysia ferruginea), at three temperatures [...] Read more.
We evaluated the thermogravimetric and devolatilization rates of hemicellulose and cellulose, and the calorimetric behavior of the torrefied biomass, of five tropical woody species (Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis and Vochysia ferruginea), at three temperatures (TT) and three torrefaction times (tT) using a thermogravimetric analyzer. Through a multivariate analysis of principal components (MAPC), the most appropriate torrefaction conditions for the different types of woody biomass were identified. The thermogravimetric analysis-derivative thermogravimetry (TGA-DTG) analysis showed that a higher percentage of the hemicellulose component of the biomass degrades, followed by cellulose, so that the hemicellulose energy of activation (Ea) was less than that of cellulose. With an increase in TT and tT, the Ea for hemicellulose decreased but increased for cellulose. The calorimetric analyses showed that hemicellulose is the least stable component in the torrefied biomass under severe torrefaction conditions, and cellulose is more thermally stable in torrefied biomass. From the MAPC results, the best torrefaction conditions for calorimetric analyses were at 200 and 225 °C after 8, 10, and 12 min, for light and middle torrefaction, respectively, for the five woody species. Full article
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Open AccessArticle Life Cycle Performance of Hydrogen Production via Agro-Industrial Residue Gasification—A Small Scale Power Plant Study
Energies 2018, 11(3), 675; https://doi.org/10.3390/en11030675
Received: 28 January 2018 / Revised: 13 March 2018 / Accepted: 13 March 2018 / Published: 16 March 2018
Cited by 2 | PDF Full-text (2100 KB) | HTML Full-text | XML Full-text
Abstract
This study evaluates the environmental profile of a real biomass-based hydrogen production small-scale (1 MWth) system composed of catalytic candle indirectly heated steam gasifier coupled with zinc oxide (ZnO) guard bed, water gas shift (WGS) and pressure swing absorber (PSA) reactors. [...] Read more.
This study evaluates the environmental profile of a real biomass-based hydrogen production small-scale (1 MWth) system composed of catalytic candle indirectly heated steam gasifier coupled with zinc oxide (ZnO) guard bed, water gas shift (WGS) and pressure swing absorber (PSA) reactors. Environmental performance from cradle-to-gate was investigated by life cycle assessment (LCA) methodology. Biomass production shows high influence over all impact categories. In the syngas production process, the main impacts observed are global warming potential (GWP) and acidification potential (AP). Flue gas emission from gasifier burner has the largest proportion of total GWP. The residual off gas use in internal combustion engine (ICE) leads to important environmental savings for all categories. Hydrogen renewability score is computed as 90% due to over 100% decline in non-renewable energy demand. Sensitivity analysis shows that increase in hydrogen production efficiency does not necessarily result in decrease in environmental impacts. In addition, economic allocation of environmental charges increases all impact categories, especially AP and photochemical oxidation (POFP). Full article
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Open AccessFeature PaperArticle Sucrose Is a Promising Feedstock for the Synthesis of the Platform Chemical Hydroxymethylfurfural
Energies 2018, 11(3), 645; https://doi.org/10.3390/en11030645
Received: 16 February 2018 / Revised: 9 March 2018 / Accepted: 12 March 2018 / Published: 14 March 2018
Cited by 4 | PDF Full-text (2843 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hydroxymethylfurfural (HMF) has an outstanding position among bio-based platform chemicals, because high-value polymer precursors and fuel additives can be derived from HMF. Unfortunately, the large-scale industrial production of HMF is not yet realized. An open research question is the choice of hexose feedstock [...] Read more.
Hydroxymethylfurfural (HMF) has an outstanding position among bio-based platform chemicals, because high-value polymer precursors and fuel additives can be derived from HMF. Unfortunately, the large-scale industrial production of HMF is not yet realized. An open research question is the choice of hexose feedstock material. In this study, we used the highly available disaccharide sucrose for HMF synthesis. The conversion of sucrose was catalyzed by sulfuric acid in water media. Experiments were conducted at temperatures of 180, 200, and 220 °C with reaction times of 2–24 min. A carbon balance showed that the yield of unwanted side products rose strongly with temperature. We also developed a kinetic model for the conversion of sucrose, involving nine first-order reactions, to uncover the kinetics of the main reaction pathways. Within this model, HMF is produced exclusively via the dehydration of fructose. Glucose isomerizes slowly to fructose. Side products arise simultaneously from glucose, fructose, and HMF. A pathway from hexoses to xylose via reverse aldol reaction was also included in the model. We believe that sucrose is the ideal feedstock for large-scale production of HMF because it is more abundant than fructose, and easier to process than sugars obtained from lignocellulosic biomass. Full article
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Open AccessArticle Environmental Analysis of Waste-to-Energy—A Portuguese Case Study
Energies 2018, 11(3), 548; https://doi.org/10.3390/en11030548
Received: 26 January 2018 / Revised: 22 February 2018 / Accepted: 28 February 2018 / Published: 4 March 2018
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Abstract
Environmental evaluation of the waste treatment processes for the area of Greater Porto (Portugal) is presented for the year 2015. The raw data for the energy recovery plant (ERP) provided by the waste management entity were modelled into nine environmental impact categories, resorting [...] Read more.
Environmental evaluation of the waste treatment processes for the area of Greater Porto (Portugal) is presented for the year 2015. The raw data for the energy recovery plant (ERP) provided by the waste management entity were modelled into nine environmental impact categories, resorting to a life cycle assessment dedicated software (GaBi) for the treatment of 1 tonne of residues. Also, a sensitivity analysis was conducted for five scenarios in order to verify the assessment quality. Results were compared to two European average situations (typical incineration plant and sanitary landfill with no waste pre-treatment), which showed that these facilities perform better or at the same level as the average European situation, mostly due to the high efficiency observed at the ERP and to the electricity production in the incineration process. A detailed analysis concluded that these helped to mitigate the environmental impacts caused by some of the processes involved in the waste-to-energy technology (landfill showing the harder impacts), by saving material resources as well as avoiding emissions to fresh water and air. The overall performance of the energy recovery plant was relevant, 1 tonne of waste saving up to 1.3 million kg of resources and materials. Regarding the environmental indicators, enhanced results were achieved especially for the global warming potential (−171 kgCO2-eq.), eutrophication potential (−39 × 10−3 kgPO4-eq.) and terrestrial ecotoxicity potential (−59 × 10−3 kgDCB-eq.) categories. This work was the first to characterize this Portuguese incineration plant according to the used methodology, supporting the necessary follow-up required by legal frameworks proposed by European Union (EU), once this facility serves a wide populational zone and therefore is representative of the current waste management tendency in the country. LCA (life cycle assessment) was confirmed as a suitable and reliable approach to evaluate the environmental impacts of the waste management scenarios, acting as a functional tool that helps decision-makers to proceed accordingly. Full article
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Open AccessArticle Biological Pretreatment of Mexican Caribbean Macroalgae Consortiums Using Bm-2 Strain (Trametes hirsuta) and Its Enzymatic Broth to Improve Biomethane Potential
Energies 2018, 11(3), 494; https://doi.org/10.3390/en11030494
Received: 30 January 2018 / Revised: 15 February 2018 / Accepted: 19 February 2018 / Published: 27 February 2018
Cited by 2 | PDF Full-text (1750 KB) | HTML Full-text | XML Full-text
Abstract
The macroalgae consortium biomass in the Mexican Caribbean represents an emerging and promising biofuel feedstock. Its biological pretreatment and potential for energetic conversion to biomethane were investigated, since some macroalgae have hard cell walls that present an obstacle to efficient methane production when [...] Read more.
The macroalgae consortium biomass in the Mexican Caribbean represents an emerging and promising biofuel feedstock. Its biological pretreatment and potential for energetic conversion to biomethane were investigated, since some macroalgae have hard cell walls that present an obstacle to efficient methane production when those substrates are used. It has been revealed by anaerobic digestion assays that pretreatment with a Bm-2 strain (Trametes hirsuta) isolated from decaying wood in Yucatan, Mexico was 104 L CH4 kg·VS−1; In fact, the fungal pretreatment produced a 20% increase in methane yield, with important amounts of alkali metals Ca, K, Mg, Na of 78 g/L, ash 35.5% and lignin 15.6%. It is unlikely that high concentrations of ash and alkali metals will produce an ideal feedstock for combustion or pyrolysis, but they can be recommended for a biological process. Full article
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Open AccessFeature PaperArticle Identification and Quantification of Volatile Compounds Found in Vinasses from Two Different Processes of Tequila Production
Energies 2018, 11(3), 490; https://doi.org/10.3390/en11030490
Received: 18 January 2018 / Revised: 10 February 2018 / Accepted: 11 February 2018 / Published: 26 February 2018
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Abstract
Vinasses are the main byproducts of ethanol distillation and distilled beverages worldwide and are generated in substantial volumes. Tequila vinasses (TVs) could be used as a feedstock for biohydrogen production through a dark fermentative (DF) process due to their high content of organic [...] Read more.
Vinasses are the main byproducts of ethanol distillation and distilled beverages worldwide and are generated in substantial volumes. Tequila vinasses (TVs) could be used as a feedstock for biohydrogen production through a dark fermentative (DF) process due to their high content of organic matter. However, TV components have not been previously assayed in order to evaluate if they may dark ferment. This work aimed to identify and quantify volatile compounds (VC) in TV and determine if the VC profile depends upon the type of production process (whether the stems were initially cooked or not). TVs were sampled from 3 agave stems with a not-cooking (NC) process, and 3 agave stems with a cooking (C) process, and volatile compounds were determined by gas chromatography coupled with mass spectrometry (GC–MS). A total of 111 volatile compounds were identified, the TV from the cooking process (C) showed the higher presence of furanic compounds (furfural and 5-(hydroxymethyl) furfural) and organic acids (acetic acid and butyric acid), which have been reported as potential inhibitors for DF. To our knowledge, this is the first description of the VC composition from TVs. This study could serve as a base for further investigations related to vinasses from diverse sources. Full article
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Open AccessReview Biological Pretreatment Strategies for Second-Generation Lignocellulosic Resources to Enhance Biogas Production
Energies 2018, 11(7), 1797; https://doi.org/10.3390/en11071797
Received: 8 June 2018 / Revised: 2 July 2018 / Accepted: 3 July 2018 / Published: 9 July 2018
Cited by 4 | PDF Full-text (253 KB) | HTML Full-text | XML Full-text
Abstract
With regard to social and environmental sustainability, second-generation biofuel and biogas production from lignocellulosic material provides considerable potential, since lignocellulose represents an inexhaustible, ubiquitous natural resource, and is therefore one important step towards independence from fossil fuel combustion. However, the highly heterogeneous structure [...] Read more.
With regard to social and environmental sustainability, second-generation biofuel and biogas production from lignocellulosic material provides considerable potential, since lignocellulose represents an inexhaustible, ubiquitous natural resource, and is therefore one important step towards independence from fossil fuel combustion. However, the highly heterogeneous structure and recalcitrant nature of lignocellulose restricts its commercial utilization in biogas plants. Improvements therefore rely on effective pretreatment methods to overcome structural impediments, thus facilitating the accessibility and digestibility of (ligno)cellulosic substrates during anaerobic digestion. While chemical and physical pretreatment strategies exhibit inherent drawbacks including the formation of inhibitory products, biological pretreatment is increasingly being advocated as an environmentally friendly process with low energy input, low disposal costs, and milder operating conditions. Nevertheless, the promising potential of biological pretreatment techniques is not yet fully exploited. Hence, we intended to provide a detailed insight into currently applied pretreatment techniques, with a special focus on biological ones for downstream processing of lignocellulosic biomass in anaerobic digestion. Full article
Open AccessReview Opportunities and Barriers to Bioenergy Conversion Techniques and Their Potential Implementation on Swine Manure
Energies 2018, 11(4), 957; https://doi.org/10.3390/en11040957
Received: 28 March 2018 / Revised: 12 April 2018 / Accepted: 13 April 2018 / Published: 17 April 2018
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Abstract
The objectives of this article are to offer a comprehensive evaluation of the opportunities and barriers for swine manure conversion technologies and to shed light on the gaps that might require further investigation to improve the applicability of these technologies. The challenges of [...] Read more.
The objectives of this article are to offer a comprehensive evaluation of the opportunities and barriers for swine manure conversion technologies and to shed light on the gaps that might require further investigation to improve the applicability of these technologies. The challenges of manure management have been propagated alongside the global growth of swine production. Various technologies that target the production of energy, fuels, and bioproducts from swine manure have been reported. These technologies include pretreatments, i.e., drying, and solid separation; biological techniques, i.e., composting, anaerobic digestion, and biodrying; and thermochemical techniques, i.e., combustion, gasification, pyrolysis, liquefaction, and carbonization. The review highlights the yields and qualities of products, i.e., energy, gaseous fuel, liquid fuel, and solid fuel, of each technology. It exhibits that the choice of a conversion technology predominantly depends on the feedstock properties, the specifics of the conversion technique, the market values of the end products as well as the local regulations. The challenges associated with the presented techniques are discussed to ameliorate research and development in these areas. The notable finding of this paper is that there is a need for full-scale research in the area of thermochemical conversion of solid-separated swine manure. Full article
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