Hot-compressed Water Treatment Research Articles

Simulation and Optimization of Lignocellulosic Biomass Wet- and Dry-Torrefaction Process for Energy, Fuels and Materials Production: A Review

This review deals with the simulation and optimization of the dry- and wet-torrefaction processes of lignocellulosic biomass. The torrefaction pretreatment regards the production of enhanced biofuels and other materials. Dry torrefaction is a mild pyrolytic treatment method under an oxidative or non-oxidative atmosphere and can improve lignocellulosic biomass solid residue heating properties by reducing its oxygen content. Wet torrefaction usually uses pure water in an autoclave and is also known as hydrothermal carbonization, hydrothermal torrefaction, hot water extraction, autohydrolysis, hydrothermolysis, hot compressed water treatment, water hydrolysis, aqueous fractionation, aqueous liquefaction or solvolysis/aquasolv, or pressure cooking. In the case of treatment with acid aquatic solutions, wet torrefaction is called acid-catalyzed wet torrefaction. Wet torrefaction produces fermentable monosaccharides and oligosaccharides as well as solid residue with enhanced higher heating value. The simulation and optimization of dry- and wet-torrefaction processes are usually achieved using kinetic/thermodynamic/thermochemical models, severity factors, response surface methodology models, artificial neural networks, multilayer perceptron neural networks, multivariate adaptive regression splines, mixed integer linear programming, Taguchi experimental design, particle swarm optimization, a model-free isoconversional approach, dynamic simulation modeling, and commercial simulation software. Simulation of the torrefaction process facilitates the optimization of the pretreatment conditions.

Fabrication of Densified Rice Husk by Sequential Hot-Compressed Water Treatment, Blending with Poly(vinyl alcohol), and Hot Pressing.

Processing agricultural wastes into densified materials to partially substitute wooden product production is significant for reducing the consumption of forest resources. This work proposes the fabrication of high-strength rice husk (RH)-based composite materials with poly(vinyl alcohol) (PVA) via densification by hot pressing. RH was pretreated in hot-compressed water (HCW) prior to pulverization and blending with PVA or PVA/glycerol (GL). The incorporation of PVA greatly improved the strength, toughness, and waterproofness of the composite plate, which was discussed with the help of a variety of composite characterizations. The tensile strength, flexural strength, and toughness of a composite of HCW-treated RH, PVA, and GL with a mass ratio of 80:20:2 were 42, 81 MPa, and 5.9 MJ/m3, respectively. The HCW treatment and blending with PVA and GL improved those properties of the hot-pressed original RH plate by factors of 2.5, 2.3, and 6.7, respectively, and reduced the water uptake and swelling ratio in water by 57 and 53%, respectively, despite the hydrophilic nature of PVA and GL. Altogether, this work outlines a valuable and sustainable approach to the efficient utilization of agricultural wastes.

The influence of thermal treatment on recirculating two phase anaerobic digestion system

Recirculated two-phase anaerobic digestion (RTAD) is a recent technique to improve biogas production. Recirculating the effluent of two-phase anaerobic system has a methanogens invasion risk to dark fermentation. Hot compressed water is possible to reduce the methanogens invasion. The objectives of this study are identifying the effect of hot compressed water pretreatment on RTAD and evaluating the fermentation system during the change of hydraulic retention time and effluent recirculation ratio. The RTAD system was built and operated with 4 different conditions, those are hydraulic retention time 2-day (HRT 2d), HRT 3d, Effluent Ratio 1:5 (R1:5) and R2:5. The result shows that the shorter HRT increase the biogas production. The pH in the reactor is more stable after the recirculation process. In bioreactor performance, the hot compressed water treatment increased the COD removal at all conditions. The highest COD removal achieved at condition of HRT 2-day with removal up to 94.5%. The system that using hot compressed water treatment has the higher energy potential at HRT 2-day, R 1:5 and R 2:5 compared with no hot compressed water treatment.

Hot-Compressed Water Treatment and Subsequent Binderless Hot Pressing for High-Strength Plate Preparation from Rice Husk

Treatment of herbaceous biomass in hot-compressed water (HCW) depolymerizes and extracts substantial portions of hemicellulose and lignin together with silica, which are all useful chemical feedstocks. The present study proposes processing of rice husk (RH) into high-strength material after pretreatment in HCW. A type of RH was treated in HCW at 140–200 °C in a tubular percolator, dried, pulverized, and then molded into rectangular or circular plates by hot pressing without a binder. The plates of HCW-treated RH had greater tensile and flexural strengths than those of the original RH, while having smaller water absorptivity and swellability. The plates of RH pretreated at 160 °C had the best properties such as tensile strength of 26 MPa (2.8 times that of the nontreated RH), flexural strength of 21 MPa (2.6 times), fracture energy of 1453 mJ (7.8 times), water uptake of 40 wt % (0.74 times), and swelling ratio in water of 1.37 (0.92 times). These properties were attributed mainly to greatly improved pulverizability, resulting occurrence of fibrous reinforcement material, and optimized fractions of cellulose and silica (as reinforcement materials) and those of hemicellulose and lignin (as the matrix and binder). This paper also reports and discusses combined effects of the conditions of HCW treatment, pulverization, and hot-press molding on the strength of plates.

Extraction of Plant Nutrients from Sunflower Stems Using Hot-compressed Water Treatment

Extraction of Plant Nutrients from Sunflower Stems Using Hot-compressed Water Treatment

Improving saccharide concentration by mixing octyl acetate during semi-flow, hot-compressed water treatment of woody biomass

Biomass-based ethanol or acetic acid can be produced by fermentation of saccharides following wood hydrolysis. Both high saccharide yield and concentration are essential for achieving an efficient hydrolysis process. However, there can be a trade-off between yield and concentration during semi-flow, hot-compressed water treatment, a candidate for wood hydrolysis. This trade-off is because the fast water flow rate is necessary for high saccharide yields, but the large amount of water dilutes the produced hydrolysate. In this study, we mixed octyl acetate, which is a water-immiscible solvent, during hot-compressed water treatment of beech wood. By adding octyl acetate, a high flow rate was achieved without increasing the water flow rate, and the saccharide concentration was thus improved, while suppressing the decrease in saccharide yield. Furthermore, lignin-derived oligomers, which have inhibitory effects on fermentation, were removed from hydrolysate because they can dissolve in octyl acetate. We performed acetic acid fermentation using the obtained hydrolysate and found that the fermentability was markedly improved compared with the hydrolysate obtained without octyl acetate.

Physicochemical and biofunctional properties of shrimp (Penaeus japonicus) hydrolysates obtained from hot-compressed water treatment

Penaeus japonicus hydrolysates were produced by hot-compressed water treatment at 100 °C – 200 °C and 30 bar for 10 min. Hydrolysate yield varied from 44.87 ± 1.74% to 88.55 ± 2.15% with the maximum yield obtained at 200 °C. Hydrolysates showed alkaline pH, which incrementally increased with temperature. Protein, phenolic compounds, and Maillard reaction product were 45.76 ± 1.27 g/100 g dried mass, 12.47 ± 0.19 mg trolox/g dried mass, and 4.02 ± 0.01, respectively, in hydrolysates produced at 200 °C. Total and reducing sugar contents were 49.30 ± 0.11 mg/g and 14.18 ± 1.23 mg/g dried mass, respectively, in hydrolysates produced at 200 °C. P. japonicus hydrolysates showed strong free-radical scavenging capacity and DPPH, ABTS, and FRAP activities of 3.08 ± 0.04, 26.74 ± 0.06, and 12.12 ± 0.50 mg TEAC/g dried mass, respectively. The maximum free and total amino acid contents were found in hydrolysates produced at 175 °C; further temperature increment degraded amino acids.

Cascade use of bamboo as raw material for several high value products: production of xylo-oligosaccharide and activated carbon for EDLC electrode from bamboo

The cascade use of bamboo as the raw material for high-value products, that is, the production of xylo-oligosaccharide and the preparation of activated carbon for EDLC electrode, was proposed as an economically effective use of bamboo in this study. Xylo-oligosaccharides, such as xylobiose and xylotriose, were successfully produced from bamboo in a water solution by a hot compressed water process. The solid residue of bamboo after the treatment of the hot compressed water was carbonized at 400–800 °C, then activated with KOH. The KOH activation was effective for the preparation of activated carbon having a high BET specific surface area of ca. 2600 m2 g−1 from the solid residue. The amount of ash drastically decreased by the hot compressed water treatment, which should be an advantage as the precursor for EDLC electrodes. The capacitance values measured in a 1 M H2SO4 aqueous solution of the activated carbon derived from the solid residue compared well with those from the bamboo.

Circulatory Management of Nutritional Substance Growing Sunflower and Extracting Nutrition by Hot-compressed Water Treatment

Sunflowers are grown as an ornamental plant and a catch crop beside an oilseed crop in Japan. Seed residues after oil milling are recycled as a feed for livestock and a fertilizer. After harvesting, crop residue such as stem and leaves are returned to the soil by the tillage in conventional cultivation. This report discusses the appropriate circulatory management of crop residues and plant nutrition considering them as a new commodity and plant nutrients resource for activating small agriculture. To study the characteristics of the nitrogen uptake from soil, sunflower cultivar named Hybrid Sunflower was grown with fixed row distance of 70 cm and varying hill distance of 10, 20, 30, 40 and 50 cm in a 5 m * 5m plot at a university farm, Tokyo, Japan. Growth survey was carried out every week. Sunflower whole crops sampled at each plot were dried in the oven at 70 °C for 1 day soon after the blanching treatment and stored until the extraction experiment. Sunflower sample at the growth stage of after flowering had the largest mass compared with the stage of before flowering and seed harvesting. Total dried matter of whole crop in 10cm-plot was the largest among the planting density conditions for each growth stage. The dried matter of crop residue at the growth stage of seed harvesting was 613, 408, 323, 281 and 279 g/m2 for the plot of 10, 20, 30, 40 and 50 cm, respectively. Nitrogen contained in sunflower stem was 2.5 to 5.5 g-N/m2 and that in seed was almost double, 5.9 to 7.5 g- N/m2. Sunflowers were processed to extract nitrogen by the hot-compressed water (HCW) treatment. Ground sample of sunflower stem mixed with water was heated at temperature of 180, 200 and 220 °C with gas pressure of 2 MPa in a pressure tight reactor for 5 and 30 min to release nitrogen from the solid fibre. Sample was separated into the solid matter fraction and the liquid matter fraction after the treatment. Extracted nitrogen as liquid matter was 37.9, 45.5 and 49.4 % at temperature of 180, 200 and 220 °C, respectively. Approximately 40 to 50 % of nitrogen contained in sunflower stem was recovered as the liquid matter. The liquid matter can be returned to the soil as a fertilizer while the solid matter containing cellulose and hemi- cellulose can be used as a raw material for bioethanol production.

O-103 加圧熱水処理によるタケヘミセルロースの可溶化と可溶化物の酵素分解(セッション1:技術1,口頭発表)

O-103 加圧熱水処理によるタケヘミセルロースの可溶化と可溶化物の酵素分解(セッション1:技術1,口頭発表)

3-7.加圧熱水処理によるリグノセルロースからのバイオエタノール生産における発酵阻害((2)エタノール,Session 3 バイオマス等)

3-7.加圧熱水処理によるリグノセルロースからのバイオエタノール生産における発酵阻害((2)エタノール,Session 3 バイオマス等)

3-45 加圧熱水処理によるリグノセルロースからの各種酵母を用いたバイオエタノール生産((12)水熱反応2,Session 3 バイオマス等,研究発表(口頭発表))

3-45 加圧熱水処理によるリグノセルロースからの各種酵母を用いたバイオエタノール生産((12)水熱反応2,Session 3 バイオマス等,研究発表(口頭発表))

P213 イナワラの酵素糖化に対するリン酸水熱処理の効果(ポスター発表)

P213 イナワラの酵素糖化に対するリン酸水熱処理の効果(ポスター発表)

3-14-6 バイオマスの加圧熱水処理により得られた炭化物の燃焼特性(Session 3 バイオマス等)

3-14-6 バイオマスの加圧熱水処理により得られた炭化物の燃焼特性(Session 3 バイオマス等)

3-77p バガスの酵素糖化に対するリン酸加圧熱水処理の効果(バイオマス等,研究発表(ポスター発表))

3-77p バガスの酵素糖化に対するリン酸加圧熱水処理の効果(バイオマス等,研究発表(ポスター発表))

3-90-2 リグニン含有率の異なるイナワラの水熱処理(Session 3 バイオマス等,ポスター発表)

3-90-2 リグニン含有率の異なるイナワラの水熱処理(Session 3 バイオマス等,ポスター発表)

Characterization of the precipitated lignin from Japanese beech as treated by semi-flow hot-compressed water

Abstract Japanese beech (Fagus crenata) was decomposed by a semi-flow process in hot-compressed water (HCW) at 150~230°C/10 MPa for 25 min. Mainly hemicelluloses and partly the lignin moiety of the wood was affected and liquefied in water. A part of the liquefied products can be precipitated after 12 h standing at ambient conditions. The precipitates are composed of around 90% of lignin, which was quantified and characterized by various chemical and spectroscopic methods in comparison of milled wood lignin (MWL), which is considered to be a representative compound for the native lignin in wood. The yield of the precipitated lignin (Lprecip) is higher than that of MWL and its syringyl content is also higher as demonstrated by alkaline nitrobenzene oxidation (NBO) giving rise to higher syringaldehyde/vanillin (SA/VA) ratios. Its OHphen group content was also high. The interpretation is that Lprecip is mainly from the secondary wall, and accordingly, the presented semi-flow HCW treatment offers the possibility for an efficient lignin isolation.

Two-Step Hot-Compressed Water Treatment of Douglas Fir for Efficient Total Sugar Recovery by Enzymatic Hydrolysis

The non-catalytic hydrothermal pretreatment of softwood is generally less effective for subsequent enzymatic hydrolysis. In this study, the efficacy of hot-compressed water (HCW) treatment of Douglas fir was investigated between 180 °C and 260 °C, allowing solubilization of the cellulose components. The enzymatic digestibility of cellulosic residues increased significantly under HCW conditions > 250 °C, and the enhanced glucan digestibility was closely related to the decomposition of the cellulose component. Combination of the first-stage HCW treatment (220 °C, 5 min) to recover hemicellulosic sugars with the second-stage HCW treatment (260 °C, 5 min) to improve cellulose digestibility gave a total sugar recovery of 56.2% based on the dried raw materials. This yield was 1.4 times higher than that from the one-step HCW-treated sample (260 °C, 5 min). Additionally, an enzymatic hydrolysate from the two-step HCW-treated sample exceeded 90% of the ethanol fermentation yield based on the total sugars present in the hydrolysates. These results suggest the potential of the two-step HCW treatment of softwood as a pretreatment technology for efficient total sugar recovery and ethanol production.

Evaluation of the effect of hot-compressed water treatment on enzymatic hydrolysis of lignocellulosic nanofibrils with different lignin content using a quartz crystal microbalance.

Hot-compressed water (HCW) treatment is known to not only improve enzymatic hydrolysis efficiency of lignocellulosic biomass but to also generate insoluble lignin droplets, which retard enzymatic hydrolysis. In this study, the inhibitory effect of the lignin droplets was evaluated by monitoring the initial enzyme adsorption and degradation of lignocellulosic nanofibrils (LCNFs) using a quartz crystal microbalance (QCM). Lignin content was adjusted by the sodium chlorite-acetic acid method and divided into samples with high (24.9 wt%) and low (5.6 wt%) lignin content, which were then subjected to HCW treatment at various temperatures. The changes in lignin content were small with increasing HCW temperature, whereas hemicellulose content decreased, regardless of the initial lignin content. The formation of lignin droplets and pseudo-lignin-like products was confirmed in both LCNFs by atomic force microscopy (AFM) and was predominant in LCNFs with high lignin content treated at 200°C. QCM data showed that the enzyme adsorption amount in both LCNFs after HCW treatment was increased and was greater in LCNFs with low lignin content. Initial enzymatic degradation was substantially slowed in LCNFs with high lignin content, particularly after HCW treatment at temperatures higher than 180°C. These QCM results suggest that the steric hindrance of the deposited lignin is the primary mechanism by which the initial enzymatic hydrolysis is delayed. Biotechnol. Bioeng. 2016;113: 1441-1447. © 2015 Wiley Periodicals, Inc.

Comparative study on topochemistry of delignification from Japanese cedar and Japanese beech by hydrothermal treatment

The difference in decomposition behavior of lignin from Japanese cedar (Cryptomeria japonica) as softwood and Japanese beech (Fagus crenata) as hardwood treated by hot-compressed water was investigated. The obtained residual lignin was then evaluated by the alkaline nitrobenzene oxidation analysis, the relative proportion of ether type linkages had decreased for both species as the hot-compressed water treatment was prolonged. Furthermore, the microscopic observation of the residual lignin indicated that lignin in tracheid cell walls was removed to a greater extent than that in middle lamella in Japanese cedar. Similarly in Japanese beech, lignin in fiber cell walls was removed more extensively, with middle lamella lignin remaining after two-step treatment. Such observation was supported by a result obtained from the methoxyl content analysis per C9 unit of the residual lignin. Based on these lines of evidence, lignin in middle lamella must be rich in condensed type, and these differences between softwood and hardwood can be attributed to the intrinsic characteristics of the original lignin and its topochemistry in woods.