This study focuses on the investigation of the extent of the γ-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The ...hydrolysis of a 50 wt% GVL solution to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2 × 10
–5
wt% to 6 wt%) at elevated temperatures (150–180 °C) and reaction times between 30 and 180 min caused the formation of 4 mol% 4-HVA. However, with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at a constant time (30 min) and temperature (180 °C) with the variation of the NaOH concentration (0.2 × 10
–6
wt% to 7 wt%). The addition of less than 0.2 wt% of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The degree of decomposition after treatment was determined by NMR analysis. To verify the GVL stability under practical conditions,
Betula pendula
sawdust was fractionated in 50 wt% GVL with and without the addition of H
2
SO
4
or NaOH at 180 °C and a treatment time of 120 min. The spent liquor was analyzed and a 4-HVA content of 5.6 mol% in a high acidic (20 kg H
2
SO
4
/t wood) and 6.0 mol% in an alkaline (192 kg NaOH/t wood) environment have been determined.
In this study, we propose a full gamma-valerolactone (GVL) organosolv biorefinery concept including the utilization of all pulping streams, solvent recovery, and preliminary material and energy ...balances. GVL is a renewable and non-toxic solvent that fractionates woody biomass. The silver birch chips were pulped (45–65 wt% GVL, 150 °C, 2 h) under a series of acid-catalyzed conditions (5–12 kg H2SO4/t), and the fully bleached pulp was spun into fibers by the IONCELL® process and knitted into the fabric. The dissolved lignin was precipitated by water from spent liquor (1:1) and processed into polyhydroxyurethane. Most of the dissolved hemicelluloses were in the form of xylose, therefore, the crystallization efficiency of xylose from spent liquor in the presence of residual GVL was studied. The GVL recovery rate in the lab column was 66%, however by increasing the number of equilibrium stages, 99% recovery could be achieved.
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•GVL organosolv pulping yields high-quality pulp easily convertible to fibers.•Ioncell fibers made of GVL pulp demonstrated high toughness.•GVL enhances the crystallization of xylose from spent liquor.•Lignin dissolved during GVL fractionation is suitable for industrial application.•Liquid CO2 can effectively recover GVL from spent liquor.
Human urine contributes approximately 80% of nitrogen and 50% of phosphorous in urban wastewaters while having a volume of only 1–1.5 L/d per capita compared to 150–200 L/d per capita of wastewater ...generated. There is interest to study source separation of urine and search methods to recover the nutrients form the urine. In this study, the objective was to use the nutrients in source separated urine for outdoor cultivation of microalgae in Nordic climate. A freshwater green microalga Scenedesmus acuminatus was grown in different dilutions (1:20 and 1:15) of source separated human urine, in a semi-continuously operated outdoor raceway pond with a liquid volume of 2000 L, at hydraulic retention time of 15 d. The microalgae could remove 52% nitrogen and 38% phosphorus even at culture temperatures as low as 5 °C, while obtaining a biomass density of 0.34 g VSS/L. Harvested microalgal biomass could be used to produce methane with a yield of 285 L CH4/kg volatile solids.
•Scenedesmus acuminatus grow in 1:20 & 1:15 diluted source separated human urine.•Experiments on 2000 L semi-continuous outdoor raceway pond with 15 d HRT.•Scenedesmus remove 52% TN and 38% TP even at culture temperatures <5 °C.•Biomass density of 0.34 g VSS/L and OD of 1.14 achieved.•Harvested microalgal biomass used to produce 285 L CH4/kg.
Organosolv pulping represents an alternative to the traditional production of pulp, cellulosic fibrous material, allowing the utilization of other pulping streams. Pulping of resistant wood species ...such as Finnish silver birch ( Betula pendula ) is generally challenging for an uncatalyzed organosolv system. In this study, we investigate two concepts of organosolv γ-valerolactone (GVL) pulping for the production of dissolving pulp. Silver birch sawdust was fractionated in both a one-step process with sulfuric acid or sodium hydroxide-catalyzed liquor and a two-step process with a prehydrolysis step followed by an alkaline GVL digestion step. The selectivity of delignification and hemicellulose removal in one-stage alkaline-GVL pulping was less efficient compared to uncatalyzed GVL pulping due to the partial consumption of sodium hydroxide solution in the GVL pulping liquor, which hydrolyzed to 4-hydroxyvaleric acid (4-HVA) under alkaline conditions according to the equilibrium conditions. Acid-catalyzed GVL pulping at higher temperature (180 °C) resulted in a pure cellulose fraction with a low amount of lignin and hemicelluloses (<5%), but at the expense of pulp yield. Prehydrolysis removed 50% of the original hemicellulose content, but the overall performance of two-stage pulping did not improve pulping selectivity and thus pulp qualities. Optimum conditions for one-stage acid-catalyzed GVL pulping were identified as 150 °C, 120 min, and 5–10 kg H 2 SO 4 per t for the production of dissolving pulp with specifications and macromolecular properties comparable to those of an acid sulfite dissolving pulp.
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