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13 pages, 2940 KiB

Open AccessArticle

Maximizing Biogas Yield Using an Optimized Stacking Ensemble Machine Learning Approach

by Angelique Mukasine, Louis Sibomana, Kayalvizhi Jayavel, Kizito Nkurikiyeyezu and Eric Hitimana

Energies 2024, 17(2), 364; https://doi.org/10.3390/en17020364 - 11 Jan 2024

Viewed by 790

Abstract

Biogas is a renewable energy source that comes from biological waste. In the biogas generation process, various factors such as feedstock composition, digester volume, and environmental conditions are vital in ensuring promising production. Accurate prediction of biogas yield is crucial for improving biogas [...] Read more.

Biogas is a renewable energy source that comes from biological waste. In the biogas generation process, various factors such as feedstock composition, digester volume, and environmental conditions are vital in ensuring promising production. Accurate prediction of biogas yield is crucial for improving biogas operation and increasing energy yield. The purpose of this research was to propose a novel approach to improve the accuracy in predicting biogas yield using the stacking ensemble machine learning approach. This approach integrates three machine learning algorithms: light gradient-boosting machine (LightGBM), categorical boosting (CatBoost), and an evolutionary strategy to attain high performance and accuracy. The proposed model was tested on environmental data collected from biogas production facilities. It employs optimum parameter selection and stacking ensembles and showed better accuracy and variability. A comparative analysis of the proposed model with others such as k-nearest neighbor (KNN), random forest (RF), and decision tree (DT) was performed. The study’s findings demonstrated that the proposed model outperformed the existing models, with a root-mean-square error (RMSE) of 0.004 and a mean absolute error (MAE) of 0.0024 for the accuracy metrics. In conclusion, an accurate predictive model cooperating with a fermentation control system can significantly increase biogas yield. The proposed approach stands as a pivotal step toward meeting the escalating global energy demands. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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12 pages, 2241 KiB

Open AccessFeature PaperArticle

Purified Glycerine from Biodiesel Production as Biomass or Waste-Based Green Raw Material for the Production of Biochemicals

by Grzegorz Borówka, Grzegorz Semerjak, Wojciech Krasodomski and Jan Lubowicz

Energies 2023, 16(13), 4889; https://doi.org/10.3390/en16134889 - 23 Jun 2023

Cited by 1 | Viewed by 1389

Abstract

Glycerine (glycerol) is a polyol consisting of three carbon atoms bonded to hydroxyl groups. It is a by-product of the transesterification of triglycerides, such as animal fats, vegetable oils, or used cooking oils during the biodiesel production process. Crude glycerine is subject to [...] Read more.

Glycerine (glycerol) is a polyol consisting of three carbon atoms bonded to hydroxyl groups. It is a by-product of the transesterification of triglycerides, such as animal fats, vegetable oils, or used cooking oils during the biodiesel production process. Crude glycerine is subject to purification processes resulting in distilled glycerine containing at least 99.5% glycerol. Currently, produced high-quality distilled glycerine is used in the food, pharmaceutical, and cosmetic industries. Recently, technologies for converting glycerol to other chemicals through catalytic processes have been intensively developed, e.g., production of bio-based 1,2-propanediol. In the near future, glycerol will certainly become a promising renewable raw material in many modern biorefineries for the synthesis of biofuels, chemicals, and bioenergy production. This paper presents the possibility of using ion exchange resins to remove impurities with trace amounts of sulphur and nitrogen compounds from crude and distilled glycerine, produced during the biodiesel production process from used cooking oils. It was determined that using ion exchange resins at the preliminary purification stage (before distillation) was ineffective. Using cationite resins to purify distilled glycerine produced from waste materials enables the removal of impurities in the form of sulphur and nitrogen compounds. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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13 pages, 977 KiB

Open AccessArticle

Biodiesel Production Catalyzed by Lipase Extract Powder of Leonotis nepetifolia (Christmas Candlestick) Seed

by Verónica Ávila Vázquez, Miguel Mauricio Aguilera Flores, Luis Felipe Hernández Casas, Nahum Andrés Medellín Castillo, Alejandro Rocha Uribe and Hans Christian Correa Aguado

Energies 2023, 16(6), 2848; https://doi.org/10.3390/en16062848 - 19 Mar 2023

Cited by 4 | Viewed by 1541

Abstract

This work aimed to evaluate the ability of lipase extract powder obtained from Leonotis nepetifolia seed for enzyme-catalyzed biodiesel production using Leonotis nepetifolia oil, commercial olive oil, and waste cooking oil as substrates. The lipase extract powder showed an enzymatic activity and hydrolysis [...] Read more.

This work aimed to evaluate the ability of lipase extract powder obtained from Leonotis nepetifolia seed for enzyme-catalyzed biodiesel production using Leonotis nepetifolia oil, commercial olive oil, and waste cooking oil as substrates. The lipase extract powder showed an enzymatic activity and hydrolysis percentage of 24.7 U/g and 21.31%, respectively, using commercial olive oil as a reference. Transesterification reaction conditions were 40 g of substrate, 34 °C, molar ratio oil: methanol of 1:3, lipase extract powder 20 wt%, phosphates buffer (pH 4.8) 20 wt%, and a reaction time of 8 h. Transesterification yields of 74.5%, 71.5%, and 69.3% for commercial olive oil, waste cooking oil, and Leonotis nepetifolia oil were obtained, respectively. Biodiesel physicochemical parameters were analyzed and compared with the international standards: EN 14214 (European Union) and ASTM D6751 (American Society for Testing and Materials). The biodiesel’s moisture and volatile matter percentages, iodine index, cooper strip corrosion, and methyl esters content conformed to the standards’ specifications. The fatty acid methyl ester content of the vegetable oils showed the presence of methyl oleate after enzyme-catalyzed transesterification. This study reveals that biodiesel production catalyzed by lipase extract powder from Leonotis nepetifolia could be a viable alternative, showing that transesterification yields competitive results. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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12 pages, 5430 KiB

Open AccessFeature PaperArticle

Biomass Origin Waste as Activators of the Polyurethane Foaming Process

by Patrycja Zakrzewska, Beata Zygmunt-Kowalska, Monika Kuźnia, Artur Szajding, Tadeusz Telejko and Małgorzata Wilk

Energies 2023, 16(3), 1354; https://doi.org/10.3390/en16031354 - 27 Jan 2023

Cited by 4 | Viewed by 1434

Abstract

Rigid polyurethane foams (RPUFs) are characterized by their excellent viable properties; thus, these materials can be successfully used as thermal insulation materials. The main problem, the solution of which is partly indicated in this paper, is that the products for the synthesis of [...] Read more.

Rigid polyurethane foams (RPUFs) are characterized by their excellent viable properties; thus, these materials can be successfully used as thermal insulation materials. The main problem, the solution of which is partly indicated in this paper, is that the products for the synthesis of RPUFs are produced from petrochemicals. Due to this, the use of natural fillers in the form of waste biomass is introduced for the synthesis of RPUFs. The biodegradable biomass waste used in the RPUF production process plays multiple roles: it becomes an activator of the RPUF foaming process, improves selected properties of RPUF materials and reduces the production costs of insulating materials. The paper presents the results of the foaming process with the use of six different fillers: sunflower husk (SH), rice husk (RH), buckwheat husk (BH), sunflower husk ash (SHA), rice husk ash (RHA) and buckwheat husk ash (BHA). In all cases, composites of rigid polyurethane foam with 10 wt.% of filler were produced. New foams were compared with polyurethane materials without the addition of a modifier. Moreover, the paper presents the results of the fillers’ analysis used in the tests and the effects of the fillers’ addition as activators of the RPUF foaming process. Promising results were obtained for two of the fillers, BHA and SHA, as activators of the foaming process and confirmed by the volumetric results, where the named samples reached their maximum value in half the time compared to the remaining samples. In addition, the expansion rate for PU_10BHA was a maximum of approximately 11 cm³/s and PU_10SHA was a maximum of approximately 9 cm³/s, whereas the remaining samples showed this parameter at about 3 cm³/s. During the research, the scanning electron microscopy method and infrared camera technique were used. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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15 pages, 6194 KiB

Open AccessArticle

Solvothermal Liquefaction of Blackcurrant Pomace in the Water-Monohydroxy Alcohol Solvent System

by Mariusz Wądrzyk, Łukasz Korzeniowski, Marek Plata, Rafał Janus, Marek Lewandowski, Grzegorz Borówka and Przemysław Maziarka

Energies 2023, 16(3), 1127; https://doi.org/10.3390/en16031127 - 19 Jan 2023

Cited by 3 | Viewed by 1142

Abstract

Wet organic wastes are especially troublesome in valorization. Therefore, innovative solutions are still in demand to make valorization feasible. In this study, we tested a new transformation route of a blackcurrant pomace as a high-moisture industrial waste through a series of high-temperature and [...] Read more.

Wet organic wastes are especially troublesome in valorization. Therefore, innovative solutions are still in demand to make valorization feasible. In this study, we tested a new transformation route of a blackcurrant pomace as a high-moisture industrial waste through a series of high-temperature and pressure solvothermal liquefaction experiments. The feedstock was directly converted under near-critical conditions of the binary solvent system (water/2-propanol). The goal was to examine the effect of conversion parameters (temperature, biomass-to-solvent ratio) on the change in the yield of resultant bioproducts, as well as the quality thereof. The experiments were conducted in a batch autoclave at a temperature between 250 and 300 °C. The main product of the transformation was liquid biocrude, which was obtained with the highest yield (ca. 52 wt.%) at 275 °C. The quality of biocrude was examined by ATR-FTIR, GC-MS, and elemental analysis. The ultimate biocrude was a viscous heterogeneous mixture containing various groups of components and exhibiting evident energy densification (ca. 145–153%) compared to the value of the feedstock. The proposed processing method is suitable for further development toward efficient valorization technology. More specifically, the co-solvent additive for liquefaction is beneficial not only for the enhancement of the yield of the desired product, i.e., biocrude, but also in terms of technological aspects (reduction of operational pressure and temperature). Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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14 pages, 1651 KiB

Open AccessArticle

Developing a Proximate Component Prediction Model of Biomass Based on Element Analysis

by Sunyong Park, Seok Jun Kim, Kwang Cheol Oh, La Hoon Cho and DaeHyun Kim

Energies 2023, 16(1), 509; https://doi.org/10.3390/en16010509 - 2 Jan 2023

Cited by 4 | Viewed by 1501

Abstract

Interest in biomass has increased due to current environmental issues, and biomass analysis is usually performed using element and proximate analyses to ascertain its fuel characteristics. Mainly, element component prediction models have been developed based on proximate analysis, yet few studies have predicted [...] Read more.

Interest in biomass has increased due to current environmental issues, and biomass analysis is usually performed using element and proximate analyses to ascertain its fuel characteristics. Mainly, element component prediction models have been developed based on proximate analysis, yet few studies have predicted proximate components based on element analysis. Hence, this study developed a proximate component prediction model following the calorific value calculation. Analysis of Pearson’s correlation coefficient showed that volatile matter (VM) and fixed carbon (FC) were positively correlated with hydrogen and oxygen, and with carbon, respectively. Thus, the model correlation was developed using a combination of the “stepwise” and “enter” methods along with linear or nonlinear regressions. The optimal models were developed for VM and ash content (Ash). The VM optimal model values were: R² = 0.9402, root-mean-square error (RMSE) = 7.0063, average absolute error (AAE) = 14.8170%, and average bias error (ABE) = −11.7862%. For Ash, the values were: R² = 0.9249, RMSE = 2.9614, AAE = 168.9028%, and ABE = 167.2849%, and for FC, the values were: R² = 9505, RMSE = 6.3214, AAE = 18.3199%, and ABE = 15.0094%. This study provides a model to predict the proximate component by element analysis. Contrary to existing method, proximate analysis can be predicted based on elemental analysis, and shows that consume samples can be performed at once. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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Review

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27 pages, 2467 KiB

Open AccessReview

Biohythane, Biogas, and Biohydrogen Production from Food Waste: Recent Advancements, Technical Bottlenecks, and Prospects

by Shivali Sahota, Subodh Kumar and Lidia Lombardi

Energies 2024, 17(3), 666; https://doi.org/10.3390/en17030666 - 30 Jan 2024

Cited by 1 | Viewed by 1495

Abstract

Food waste (FW) is a significant global issue with a carbon footprint of 3.3 billion tonnes (Bt), primarily generated due to improper food supply chain management, storage issues, and transportation problems. Acidogenic processes like dark fermentation, anaerobic digestion, and a combination of DF-AD [...] Read more.

Food waste (FW) is a significant global issue with a carbon footprint of 3.3 billion tonnes (Bt), primarily generated due to improper food supply chain management, storage issues, and transportation problems. Acidogenic processes like dark fermentation, anaerobic digestion, and a combination of DF-AD can produce renewable biofuels (Bio-CH₄, Bio-H₂) by valorising FW, aligning with the UN SDGs. FW is an ideal substrate for acidogenic processes due to its high moisture content, organic matter, and biodegradability. However, the choice of FW valorisation pathways depends on energy yield, conversion efficiency, and cost effectiveness. Acidogenic processes are not economically viable for industrial scale FW treatment due to reduced energy recovery from stand-alone processes. So, this study reviews comparative studies on biogas, biohydrogen, and biohythane production from FW via acidogenic processes, focusing on energy yield, energy recovery, and environmental and economic impact to provide a clear understanding of energy recovery and yield from all acidogenic processes. Additionally, this review also explores the recent advancements in digestate slurry management and the synergistic effects of AD and HTC processes. Lastly, a futuristic integrated bio-thermo-chemical process is proposed for maximum energy recovery, valuing food waste to energy vectors (Bio-H₂, Bio-CH₄, and hydro-char) along with digestate management and biofertilizer production. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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18 pages, 2190 KiB

Open AccessFeature PaperReview

Hydrothermal Carbonization of Digestate Produced in the Biogas Production Process

by Joanna Mikusińska, Monika Kuźnia, Klaudia Czerwińska and Małgorzata Wilk

Energies 2023, 16(14), 5458; https://doi.org/10.3390/en16145458 - 18 Jul 2023

Cited by 1 | Viewed by 1490

Abstract

In agricultural biogas plants, besides biogas, the by-product digestate is also produced. Due to its high moisture content and organic origin, it can successfully be applied in the hydrothermal carbonization process to avoid the fate of landfilling. This paper reviews the properties of [...] Read more.

In agricultural biogas plants, besides biogas, the by-product digestate is also produced. Due to its high moisture content and organic origin, it can successfully be applied in the hydrothermal carbonization process to avoid the fate of landfilling. This paper reviews the properties of agricultural digestate and its hydrothermal conversion (HTC) into hydrochar and process water. The type of feedstock and the parameters of the HTC process, such as temperature, pressure and residence time, affects the physical and chemical characteristics of hydrochar. Therefore, its possible application might be as a biofuel, fertilizer, soil improver, adsorber, or catalyst. In this paper, the properties of hydrochar derived from agricultural digestate are widely discussed. Full article

(This article belongs to the Special Issue Biomass, Biofuels and Waste)

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