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17 pages, 5269 KiB

Open AccessArticle

Poplar Wood Pretreatment Using Deep Eutectic Solvents for Promoting Enzymatic Hydrolysis

by Xuyang Zhao, Ying Zhan, Lihua Han, Xiaoran Sun, Tianyu Zhang and Zheng Zhao

Processes 2023, 11(4), 1293; https://doi.org/10.3390/pr11041293 - 21 Apr 2023

Cited by 4 | Viewed by 1559

Bioethanol produced from lignocellulose is a renewable energy substitute for traditional fossil fuels. Poplar wood as forest waste is popular in bioethanol production. Nonetheless, the complex structure of lignocellulose leads to low reducing sugar and ethanol yields. Thus, lignocellulose pretreatment is necessary to [...] Read more.

Bioethanol produced from lignocellulose is a renewable energy substitute for traditional fossil fuels. Poplar wood as forest waste is popular in bioethanol production. Nonetheless, the complex structure of lignocellulose leads to low reducing sugar and ethanol yields. Thus, lignocellulose pretreatment is necessary to promote enzymatic hydrolysis. Deep eutectic solvents (DESs) have good dissolution capacity, low vapor pressure, a simple synthesis procedure, low synthesis cost and low toxicity. More and more researchers have begun paying attention to the application of DESs in lignocellulose pretreatment. In this work, poplar wood was pretreated using a series of basic DESs based on diol. The effects of the DES species, the basicity of the solvents, the pretreatment temperature and the pretreatment time on the effectiveness of pretreatment and enzyme hydrolysis for poplar wood were investigated, and characterization analysis (Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy) of poplar wood was carried out to reveal the pretreatment mechanism. The best pretreatment effect was obtained from K: 1, 2-PG, which removed 89.2% and 71.6% of the lignin and hemicellulose, respectively, while preserving 97.5% of the cellulose at 130 °C for 7 h. This enhanced the reducing sugar yield to 82.5% relative to that of the raw sample (3.3%) after 72 h of hydrolysis. The results of the characterization analysis demonstrated that lignin and hemicellulose were removed. Therefore, the DES based on K: 1, 2-PG is a promising solvent for poplar wood pretreatment, and could improve the industrial production of reducing sugar and bioethanol. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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21 pages, 914 KiB

Open AccessArticle

Chemical and Functional Characterization of Extracts from Leaves and Twigs of Acacia dealbata

by Ricardo Correia, Maria Paula Duarte, Elisabete Muchagato Maurício, João Brinco, José Carlos Quintela, Marco Gomes da Silva and Margarida Gonçalves

Processes 2022, 10(11), 2429; https://doi.org/10.3390/pr10112429 - 17 Nov 2022

Cited by 4 | Viewed by 2243

Abstract

The purpose of this work was to evaluate the recovery of bioactive extracts from Acacia dealbata leaves and twigs and to characterize their chemical composition and functional properties. Fresh and air-dried samples were extracted by maceration at room temperature and by hot extraction [...] Read more.

The purpose of this work was to evaluate the recovery of bioactive extracts from Acacia dealbata leaves and twigs and to characterize their chemical composition and functional properties. Fresh and air-dried samples were extracted by maceration at room temperature and by hot extraction at 60 °C using aqueous solutions of acetone, ethanol, and methanol. The highest extraction yields (14.8 and 12.0% for dried leaves and twigs, respectively) were obtained with 70% acetone, for both extraction procedures. Extracts were characterized for total phenolics content (TPC), total flavonoid content (TFC) and total proanthocyanidin content (TPrAC). Bioactive extracts with high TPC (526.4 mg GAE/g extract), TFC (198.4 mg CatE/g extract), and TPrAC (631.3 mg PycE/g extract) were obtained using maceration, a technically simple and low-energy process. The non-polar fraction of selected extracts was characterized using gas chromatography and time of flight mass spectrometry (GC-TOFMS). The main components detected were phytol, squalene, α-tocopherol, lupenone, and lupeol. The antioxidant activity of the extracts was characterized through DPPH and FRAP assays. Antimicrobial activity of the extracts against different bacteria was also determined. The highest DPPH and FRAP activities were obtained from dried twigs from Alcobaça (1068.3 mg TE/g extract and 9194.6 mmol Fe²⁺/g extract, respectively). Extracts from both leaves and twigs showed antimicrobial properties against Staphylococcus aureus, Staphylococcus epidermidis, methicillin resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Bacillus cereus, Streptococcus mutans, and Streptococcus mitis. The results obtained demonstrate the feasibility of recovering valuable components from these biomass fractions that may be further valorized for energy production in a biorefinery concept. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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12 pages, 1945 KiB

Open AccessArticle

Evaluation of the Gas Emissions during the Thermochemical Conversion of Eucalyptus Woodchips

by João Silva, Carlos Castro, Senhorinha Teixeira and José Teixeira

Processes 2022, 10(11), 2413; https://doi.org/10.3390/pr10112413 - 16 Nov 2022

Cited by 2 | Viewed by 1070

Abstract

The combustion of solid biomass in industrial boilers involves a sequence of processes that include heating, drying, devolatilization, and char conversion. To maintain a repeatable and fully controlled environment, and to monitor all the dynamics involved in the phenomena at a real scale, [...] Read more.

The combustion of solid biomass in industrial boilers involves a sequence of processes that include heating, drying, devolatilization, and char conversion. To maintain a repeatable and fully controlled environment, and to monitor all the dynamics involved in the phenomena at a real scale, field-scale experiments become necessary to perform investigations. In this way, to evaluate different thermochemical conversion conditions of biomass particles under an oxidative atmosphere, and to quantify the emission of the main gas compounds continuously, a small-scale reactor was developed and presented in this paper. Hence, in this work, larger particles of eucalyptus are burned at 400 and 800 °C under different stoichiometric conditions to understand the differences between different biomass conversion regimes (gasification and combustion). The analysis of the mass loss at the different temperatures was characterized by only two different and consecutive stages for both thermochemical conditions. The first region does not present the influence on the air flow rate; however, there is a significant difference in the second region. This fact highlighted the importance of the diffusion of oxygen during the char conversion. Regarding the quantification of the gas compounds, an increase of around 3 times in the CO and CO₂ emissions when gasification occurs was observed at 400 °C. However, at 800 °C, the same trend was verified, also verifying a considerable amount of CH₄. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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12 pages, 921 KiB

Open AccessFeature PaperArticle

The Influence of Solvent and Extraction Time on Yield and Chemical Selectivity of Cuticular Waxes from Quercus suber Leaves

by Rita Simões, Isabel Miranda and Helena Pereira

Processes 2022, 10(11), 2270; https://doi.org/10.3390/pr10112270 - 03 Nov 2022

Cited by 2 | Viewed by 1802

Abstract

The cuticular lipid compounds, usually named cuticular waxes, present in the cuticular layering of Quercus suber adult leaves were extracted with solvents of different polarities (n-hexane, dichloromethane and acetone) and analysed by GC–MS. Q. suber leaves have a substantial cuticular wax layer (2.8% [...] Read more.

The cuticular lipid compounds, usually named cuticular waxes, present in the cuticular layering of Quercus suber adult leaves were extracted with solvents of different polarities (n-hexane, dichloromethane and acetone) and analysed by GC–MS. Q. suber leaves have a substantial cuticular wax layer (2.8% of leaf mass and 239 μg/cm²), composed predominantly by terpenes (43–63% of all compounds), followed by aliphatic long chain molecules, mainly fatty acids, and by smaller amounts of aliphatic alcohols and n-alkanes. The major identified compound was lupeol (1.2% of leaves in n-hexane extract). The recovery and composition of cuticular lipids depended on the solvent and extraction time. The non-polar or weak polar solvents n-hexane and dichloromethane extracted similar lipid yields (77% and 86% of the total extract, respectively) while acetone solubilised other cellular compounds, namely sugars, with the lipid compounds representing 43% of the total extract. For cuticular lipids extraction, solvents with a low polarity such as n-hexane are the more suitable with an adequate extraction duration, e.g., n-hexane with a minimum extraction of 3 h. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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20 pages, 1992 KiB

Open AccessArticle

Improvement of Enzymatic Saccharification of Cellulose-Containing Raw Materials Using Aspergillus niger

by Ekaterina Budenkova, Stanislav Sukhikh, Svetlana Ivanova, Olga Babich, Vyacheslav Dolganyuk, Philippe Michaud and Olga Kriger

Processes 2021, 9(8), 1360; https://doi.org/10.3390/pr9081360 - 03 Aug 2021

Cited by 3 | Viewed by 2339

Abstract

Enzymatic hydrolysis of cellulose-containing raw materials, using Aspergillus niger, were studied. Filter paper, secondary cellulose-containing or starch-containing raw materials, miscanthus cellulose after alkaline or acid pretreatment, and wood chip cellulose, were used as substrates. The study focused on a wild A. niger [...] Read more.

Enzymatic hydrolysis of cellulose-containing raw materials, using Aspergillus niger, were studied. Filter paper, secondary cellulose-containing or starch-containing raw materials, miscanthus cellulose after alkaline or acid pretreatment, and wood chip cellulose, were used as substrates. The study focused on a wild A. niger strain, treated, or not (control), by ultraviolet (UV) irradiations for 45, 60, or 120 min (UV45, UV60, or UV120), or by UV irradiation for 120 min followed by a chemical treatment with NaN₃ + ItBr for 30 min or 80 min (UV120 + CH30 or UV120 + CH80). A mixture of all the A. niger strains (MIX) was also tested. A citrate buffer, at 50 mM, wasthe most suitable for enzymatic hydrolysis. As the UV exposure time increased to 2 h, the cellulase activity of the surviving culturewas increased (r = 0.706; p < 0.05). The enzymatic activities of the obtained strains, towards miscanthus cellulose, wood chips, and filter paper, were inferior to those obtained with commercial enzymes (8.6 versus 9.1 IU), in some cases. Under stationary hydrolysis at 37 °C, pH = 4.7, the enzymatic activity of A. niger UV120 + CH30 was 24.9 IU. The enzymatic hydrolysis of secondary raw materials, using treated A. niger strains, was themost effective at 37 °C. Similarly, the most effective treatment of miscanthus cellulose and wood chips occurred at 50 °C. The maximum conversion of cellulose to glucose was observed using miscanthus cellulose (with alkaline pretreatment), and the minimum conversion was observed when using wood chips. The greatest value of cellulase activity was evidenced in the starch-containing raw materials, indicating that A. niger can ferment not only through cellulase activity, but also via an amylolytic one. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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15 pages, 2990 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Extraction of Added-Value Triterpenoids from Acacia dealbata Leaves Using Supercritical Fluid Extraction

by Vítor H. Rodrigues, Marcelo M. R. de Melo, Inês Portugal and Carlos M. Silva

Processes 2021, 9(7), 1159; https://doi.org/10.3390/pr9071159 - 03 Jul 2021

Cited by 9 | Viewed by 2960

Abstract

Forestry biomass is a by-product which commonly ends up being burnt for energy generation, despite comprising valuable bioactive compounds with valorisation potential. Leaves of Acacia dealbata were extracted for the first time by supercritical fluid extraction (SFE) using different conditions of pressure, temperature [...] Read more.

Forestry biomass is a by-product which commonly ends up being burnt for energy generation, despite comprising valuable bioactive compounds with valorisation potential. Leaves of Acacia dealbata were extracted for the first time by supercritical fluid extraction (SFE) using different conditions of pressure, temperature and cosolvents. Total extraction yield, individual triterpenoids extraction yields and concentrations were assessed and contrasted with Soxhlet extractions using solvents of distinct polarity. The extracts were characterized by gas chromatography coupled to mass spectrometry (GC-MS) and target triterpenoids were quantified. The total extraction yields ranged from 1.76 to 11.58 wt.% and the major compounds identified were fatty acids, polyols, and, from the triterpenoids family, lupenone, α-amyrin and β-amyrin. SFE was selective to lupenone, with higher individual yields (2139–3512

{mg kg}_{leaves}^{- 1}

) and concentrations (10.1–12.4 wt.%) in comparison to Soxhlet extractions, which in turn obtained higher yields and concentrations of the remaining triterpenoids. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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20 pages, 3429 KiB

Open AccessArticle

Techno-Economic Assessment of Solar-Driven Steam Gasification of Biomass for Large-Scale Hydrogen Production

by Houssame Boujjat, Sylvain Rodat and Stéphane Abanades

Processes 2021, 9(3), 462; https://doi.org/10.3390/pr9030462 - 04 Mar 2021

Cited by 17 | Viewed by 2826

Abstract

Solar biomass gasification is an attractive pathway to promote biomass valorization while chemically storing intermittent solar energy into solar fuels. The economic feasibility of a solar gasification process at a large scale for centralized H₂ production was assessed, based on the discounted [...] Read more.

Solar biomass gasification is an attractive pathway to promote biomass valorization while chemically storing intermittent solar energy into solar fuels. The economic feasibility of a solar gasification process at a large scale for centralized H₂ production was assessed, based on the discounted cash-flow rate of return method to calculate the minimum H₂ production cost. H₂ production costs from solar-only, hybrid and conventional autothermal biomass gasification were evaluated under various economic scenarios. Considering a biomass reference cost of 0.1 €/kg, and a land cost of 12.9 €/m², H₂ minimum price was estimated at 2.99 €/kg_H2 and 2.48 €/kg_H2 for the allothermal and hybrid processes, respectively, against 2.25 €/kg_H2 in the conventional process. A sensitivity study showed that a 50% reduction in the heliostats and solar tower costs, combined with a lower land cost of below 0.5 €/m², allowed reaching an area of competitiveness where the three processes meet. Furthermore, an increase in the biomass feedstock cost by a factor of 2 to 3 significantly undermined the profitability of the autothermal process, in favor of solar hybrid and solar-only gasification. A comparative study involving other solar and non-solar processes led to conclude on the profitability of fossil-based processes. However, reduced CO₂ emissions from the solar process and the application of carbon credits are definitely in favor of solar gasification economics, which could become more competitive. The massive deployment of concentrated solar energy across the world in the coming years can significantly reduce the cost of the solar materials and components (heliostats), and thus further alleviate the financial cost of solar gasification. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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Review

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19 pages, 1391 KiB

Open AccessReview

Life Cycle Assessment (LCA) of Biochar Production from a Circular Economy Perspective

by Joana Carvalho, Lucas Nascimento, Margarida Soares, Nádia Valério, André Ribeiro, Luciana Faria, André Silva, Nuno Pacheco, Jorge Araújo and Cândida Vilarinho

Processes 2022, 10(12), 2684; https://doi.org/10.3390/pr10122684 - 13 Dec 2022

Cited by 7 | Viewed by 5836

Abstract

Climate change and environmental sustainability are among the most prominent issues of today. It is increasingly fundamental and urgent to develop a sustainable economy, capable of change the linear paradigm, actively promoting the efficient use of resources, highlighting product, component and material reuse. [...] Read more.

Climate change and environmental sustainability are among the most prominent issues of today. It is increasingly fundamental and urgent to develop a sustainable economy, capable of change the linear paradigm, actively promoting the efficient use of resources, highlighting product, component and material reuse. Among the many approaches to circular economy and zero-waste concepts, biochar is a great example and might be a way to push the economy to neutralize carbon balance. Biochar is a solid material produced during thermochemical decomposition of biomass in an oxygen-limited environment. Several authors have used life cycle assessment (LCA) method to evaluate the environmental impact of biochar production. Based on these studies, this work intends to critically analyze the LCA of biochar production from different sources using different technologies. Although these studies reveal differences in the contexts and characteristics of production, preventing direct comparison of results, a clear trend appears. It was proven, through combining life cycle assessment and circular economy modelling, that the application of biochar is a very promising way of contributing to carbon-efficient resource circulation, mitigation of climate change, and economic sustainability. Full article

(This article belongs to the Special Issue Extraction, Utilization and Conversion of Woody Biomass)

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