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• Novel concept for recovering nutrients and humic substances from AD was developed. • Cascading precipitation/membrane contactor/extraction enables recovery of valuables. • Recovered NH 3 showed great potential for extracting humics from AD digestate. • All main nutrients (P and N) together with humics were recoverable by the process. Nutrient-rich product fractions were produced from abundant, yet currently chemically under-utilized nutrients-containing feedstock, residual digestate formed during anaerobic digestion (AD). The objective of this research was to experiment individually three sub-processes, i.e., precipitation of organic humic substances and phosphorus from the digestate reject water, liberation of reject water nitrogen as ammonia gas during the lime treatment and recovering it with membrane contactor (MC), and finally novel utilization of ammonia for leaching nitrogen-enriched organic substances from the digestate residue. With calcium precipitation, the main part of the phosphorus and significant part of organic material could be precipitated, and simultaneously ammonium could be liberated with good yield as ammonia gas, so that it could be recovered by MC. On the other hand, ammonia could be used with promising results as an extraction media, by which the solubility of the organic matter and the content of nitrogen attached to the soluble organic fraction could be significantly increased. Hence, all sub-processes were found to achieve their goals and digestate could be successfully utilized as a feedstock for manufacture of varying nutrient-rich products. Combining these three subprocesses together enables the development of novel cascading process concept, in which treated product stream can be used in the next process step and in which each subprocess step benefits the next. [ABSTRACT FROM AUTHOR] more...

Sugar maple (Acer saccharum) wood chips were pretreated with aqueous sodium hydroxide, sodium borohydride, and hydrogen peroxide pretreatments, and the characterization (i.e., amount, molar masses, and molar mass distributions) of the lignin dissolved during the pretreatments was performed. Of the applied pretreatments, especially borohydride pretreatments were efficient in dissolving lignin from this feedstock, as 20% to 28% of the dissolved organics were found to consist of dissolved lignin, contributing to 3.4% to 9.0% of the initial wood lignin. Corresponding values for 2.5% and 5.0% alkaline peroxide pretreatments were from 5.9% to 9.2% dissolved lignin of the total dissolved organics and from 1.1% to 3.2% of the initial wood lignin. Additionally, determined molar masses and molar mass distributions indicated that borohydride pretreatments generally led to the formation of smaller-molar-mass lignin fragments when compared to reference pretreatments and to pretreatments conducted with alkaline peroxide process, indicating more efficient lignin degradation caused by borohydride addition. For example, Mn and Mw values of the analyzed reference effluents were 54%-62% and 66%-71% higher when compared to the corresponding borohydride effluents, respectively. [ABSTRACT FROM AUTHOR] more...

For recovering value-added wood-based organic material prior to delignification, sodium borohydride (NaBH4) and hydrogen peroxide (H2O2) pretreatments under alkaline conditions were performed before soda pulping of sugar maple (Acer saccharum) chips with sodium hydroxide (NaOH). In this investigation, it was determined whether the pulp yield could be increased by partly stabilizing the hemicelluloses by these pretreatments, and simultaneously obtains lower pulp kappa numbers. The results indicated that when aiming to the same kappa numbers (i.e., kappa numbers 14.3-20.5), roughly 3% higher pulp yield could be achieved if the chips were pretreated with alkaline 0.5% NaBH4 solutions, compared to those produced without such pretreatment or pretreated only with NaOH (i.e., without NaBH4). In contrast, pretreatments conducted with alkaline 2.5% H2O2 did clearly lower pulp yields at the same kappa number range (14.0-22.7) when compared to the reference cooks conducted with NaOH pretreated materials. However, an increase in the H2O2 charge of the pretreatment from 2.5% to 5.0% had a clearly beneficial effect, as the pulp yield and kappa numbers after pulping of 5.0% H2O2 pretreated pulps were comparable to the reference cooks. [ABSTRACT FROM AUTHOR] more...

The thermochemical behavior of Norway spruce (Picea abies) sawdust as such and after various chemical treatments (hot-water extraction, delignification, and hot-water extraction followed by delignification) was investigated by analytical pyrolysis-gas chromatography-mass spectrometry. In each case, the yields of major GC-amenable condensable products were semi-quantitatively measured, and the individual compounds were classified into several compound groups. The formation of these groups from feedstock samples with varying mass portions of their structural constituents (carbohydrates and lignin) was determined at 500 °C and 700 °C with a residence time of 5 s and 20 s. The formation of pyrolysis products was shown to be characteristically dependent on feedstock composition as well as on pyrolysis conditions. This kind of approach was of practical importance with respect to efforts not only to develop rapid characterization tools for lignocellulosics, but also to uncover new biorefinery possibilities to produce bio-oils, for example, enriched either with aliphatic or aromatic constituents. [ABSTRACT FROM AUTHOR] more...

Hot-water and dilute sulfuric acid pretreatments were performed prior to chemical pulping for silver/white birch ( Betula pendula / B. pubescens ) and Scots pine ( Pinus sylvestris ) chips to determine if varying pretreatment conditions on the original wood material were detectable via attenuated total reflectance (ATR) infrared spectroscopy. Pretreatment conditions varied with respect to temperature (130 °C and 150 °C) and treatment time (from 30 min to 120 min). The effects of the pretreatments on the composition of wood chips were determined by ATR infrared spectroscopy. The spectral data were compared to those determined by common wood chemistry analyses to evaluate the suitability of ATR spectroscopy method for rapid detection of changes in the wood chemical composition caused by different pretreatment conditions. In addition to determining wood species-dependent differences in the wood chemical composition, analytical results indicated that most essential lignin- and carbohydrates-related phenomena taking place during hot-water and acidic pretreatments could be described by applying this simple spectral method requiring only a small sample amount and sample preparation. Such information included, for example, the cleavage of essential lignin bonds ( i.e. , mainly β- O -4 linkages in guaiacyl and syringyl lignin) and formation of newly condensed lignin structures under different pretreatment conditions. Carbohydrate analyses indicated significant removal of hemicelluloses (especially hardwood xylan) and hemicelluloses-derived acetyl groups during the pretreatments, but they also confirmed the highly resistant nature of cellulose towards mild pretreatments. [ABSTRACT FROM AUTHOR] more...

The thermochemical behavior of birch ( Betula pendula ) sawdust both untreated and after various chemical treatments (hot-water extraction, delignification, and hot-water extraction followed by delignification) was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). In each case, major GC-amenable condensable products were classified into several compound groups, and the formation of these monomer-related fragments from feedstock samples with varying mass portions of the structural constituents (cellulose, hemicelluloses, and lignin) were determined at 500 °C and 700 °C at hold times of 5 s and 20 s. The formation of pyrolysis products was shown to be characteristically dependent on feedstock composition as well as on pyrolysis conditions. This kind of approach was of practical importance with respect to efforts not only to develop rapid characterization tools for lignocellulosics, but also to new biorefinery possibilities to produce bio-oils, for example, enriched either with aliphatic or aromatic constituents. [ABSTRACT FROM AUTHOR] more...

Untreated and hot-water-extracted (HWE) Norway spruce (Picea abies) sawdust was cooked using the sulfur-free oxygen-alkali (OA) method under the following conditions: temperature, 170 °C; liquor-to-wood ratio, 5:1 L/kg; and NaOH charge, 19% on the oven-dry sawdust. In comparison with earlier studies conducted with birch sawdust, the spruce cooking yield data, together with the amount of the pulp rejects (78% to 86% for reference pulps from the initial feedstock and 73% to 83% for pulps from the HWE feedstock), revealed that the pretreatment stage prior to spruce OA pulping caused different effects on pulping performance. The analyses of the three main compound groups (i.e., lignin, volatile acids, and hydroxy acids) in black liquor indicated that slightly higher contents (25.5 to 45.9 g/L) of dissolved lignin were detected in black liquors originating from the HWE sawdust than in the black liquors from the reference material (27.2 to 39.6 g/L). In contrast, considerably lower (~20% decrease) volatile acid contents and similar or slightly decreased hydroxy acids contents were detected in the black liquors from the HWE sawdust. [ABSTRACT FROM AUTHOR] more...

Alkaline pre-treatments were performed for the production of organicscontaining effluents from silver/white birch (Betula pendula/pubescens) and Scots pine (Pinus sylvestris) chips prior to chemical pulping. Pretreatment conditions were varied with respect to time (from 30 min to 120 min), temperature (130 °C and 150 °C), and alkali charge (1, 2, 3, 4, 6, and 8% of NaOH on oven-dried wood). The analytical data (total content, weight average molar mass, and molar mass distribution) on dissolved lignin were subjected to principal component analysis to examine the relationship between molar mass and molar mass distributions in lignin removed from different wood species under varying alkaline pre-treatment conditions. Using this method, differences between the wood species and effects of the various pre-treatment process variables (i.e., time, temperature, and alkali charge) were determined. [ABSTRACT FROM AUTHOR] more...

The chemical industry is being forced to evaluate new strategies for more effective utilization of renewable feedstocks to diminish the use of fossil resources. In this literature review, the integration of both acidic and alkaline pretreatment phases of hardwood and softwood chips with chemical pulping is discussed. Depending on the pretreatment conditions, high-volume sulfur-free fractions with varying chemical compositions can be produced. In case of acidic pretreatments, the major products include carbohydrates (mono-, oligo-, and polysaccharides), whereas under alkaline (i.e., aqueous NaOH) pretreatment conditions, the sulfur-free fractions of aliphatic carboxylic acids, lignin, and extractives are primarily obtained. All these fractions are potentially interesting groups of compounds and can be used in a number of applications. Finally, the effects of pretreatments on pulping are also considered. Although it is believed that there are important advantages to be gained by integrating this type of renewable raw material-based production, in particular, with kraft pulping, sulfur-free pulping methods such as soda-AQ and oxygen/alkali delignification processes are also briefly discussed. [ABSTRACT FROM AUTHOR] more...

Various alkaline pretreatments were applied to Scots pine (Pinus sylvestris) and silver/white birch (Betula pendula/pubescens) wood chips and the characterization of sulfur-free lignin dissolved was performed. The behavior of lignin during these pretreatments (alkali charge 1–8% NaOH, time 30–120 minutes, and temperature 130–150°C) was studied mainly in terms of lignin removal efficiency and molar mass distribution of dissolved lignin. The amount of lignin in pretreatment liquors increased along with an increase in the alkali charge of 0.8–4.4% and 0.6–3.4% of o.d. pine and birch wood, respectively. The most significant parameter affecting the molar mass of the dissolved lignin was shown to be the alkali charge, since an increase in this parameter clearly increased the-values of dissolved lignin, varying from 2,260 g/mol to 7,050 g/mol and from 2,200 g/mol to 5,550 g/mol for pine and birch lignin, respectively. [ABSTRACT FROM PUBLISHER] more...

The chemical composition of black liquors obtained from the soda-AQ pulping of birch ( Betula pendula) sawdust was studied as a function of cooking time, effective alkali content, and hot-water pretreatment of the sawdust prior to delignification. Special attention was paid on the formation of lignin-derived materials and low-molecular-mass carbohydrate-derived degradation products containing aliphatic carboxylic acids. In the case of the hot-water-pretreated feedstock, less acetic acid and formic acid and more nonvolatile hydroxy acids (especially monocarboxylic acids) were obtained. The observations can be interpreted as a result of the extensive removal of hemicelluloses during the hot-water pretreatment. [ABSTRACT FROM AUTHOR] more...

Scots pine (Pinus sylvestris) chips were pre-treated with alkaline solutions (alkali charges of 1, 2, 3, 4, 6, and 8% of NaOH on the oven-dried wood material) at 130°C and 150°C for various treatment times (30, 60, 90, and 120 minutes). Under these conditions, 2.0–13.6% of the wood d.s. was dissolved into the aqueous hydrolysates. The soluble organic fraction was primarily characterized in terms of carbohydrates (monosaccharides and oligo-/polysaccharides) and their alkali-catalyzed degradation products: aliphatic carboxylic acids containing, besides non-volatile hydroxy carboxylic acids, volatile formic and acetic acids. With increasing alkali charge, temperature, and time, the enhanced formation of various hydroxy monocarboxylic acids was detected. Under the most drastic pre-treatment conditions, two-thirds of the total organic fraction dissolved was composed of various aliphatic carboxylic acids, the residual material being mainly degraded lignin and extractives. Only relatively small concentrations of carbohydrates and trace amounts of furans were found. [ABSTRACT FROM PUBLISHER] more...

Autohydrolysis pre-treatments were performed for the production of hemicellulose-rich autohydrolysates from silver birch (Betula pendula) chips prior to chemical pulping. Pre-treatment conditions were varied with respect to time (from 30 to 120 min) and temperature (130 and 150 °C), covering a P-factor range from 10 to 238. Hydrolysates were analyzed in terms of carbohydrates, lignin, volatile organic acids, and furanoic compounds. The analytical data were subjected to various chemometric techniques to establish the relationships between dissolved organic components, hardwood and softwood used in the experiments, and applied pre-treatment conditions. Using this method, differences between the wood species could be clearly seen, and a relatively accurate model for the autohydrolysis of birch chips was developed. [ABSTRACT FROM AUTHOR] more...

Various chemometric techniques were used to establish the relationship between the autohydrolysis conditions prior to pulping and the chemical compositions of the soluble organic materials removed from Scots pine (Pinus sylvestris) wood chips. The aqueous chip pre-treatments (autohydrolysis) were administered at 130 °C and 150 °C for 30, 60, 90, and 120 min, and the hydrolysates obtained were characterized in terms of total carbohydrates (various mono-, oligo-, and polysaccharides together with uronic acid side groups), volatile acids (acetic and formic acids), lignin, and furans (furfural and 5-(hydroxymethyl)furfural). Based on the analytical data gathered, a relatively accurate model for pine chip autohydrolysis was developed. [ABSTRACT FROM AUTHOR] more...

Hardwood (Betula pendula) chips were extracted having alkaline aqueous solutions with varying chemical charges (1, 2, 3, 4, 6, and 8% of NaOH on wood), treatment times (30, 60, 90, and 120 minutes), and temperatures (130°C and 150°C). The total amount of material removed was in the range 2.1–16.5% of the original dry feedstock. This fraction was characterized in terms of carbohydrates and their degradation products (mainly aliphatic carboxylic acids together with some furanoic compounds), lignin, and extractives. Low alkali charges (1–4% of NaOH) were not sufficient to neutralize all the acids formed (mainly acetic acid from the acetyl groups of xylan). In contrast, an increase in alkali charge (6% and 8% of NaOH) more intensively facilitated the alkali-catalyzed degradation reactions of polysaccharides to various hydroxy acids, which were then typically present as one of the main constituents in the dissolved organic matter, along with other aliphatic carboxylic acids (acetic and formic acids), lignin, extractives, and carbohydrates. [ABSTRACT FROM PUBLISHER] more...

Carbohydrate-containing hydrolysates (1.1 to 14.9% of wood dry matter) obtained from auto hydro lysis (at 130 to 150°C for 30 to 120 minutes) of birch (Betula pendula) chips prior to pulping were purified with respect to non-carbohydrate materials, without carbohydrate losses, either by ethyl acetate extraction or XAD-4 resin treatment. In the former case, about 50% of lignin and practically all the furanoic compounds (2-furaldehyde and 5-(hydroxymethyl)furfural) could be removed, whereas in the latter case, the corresponding amounts were about 30% and 50 to 90%, respectively. A partial recovery of various unsaturated impurities is of importance, because they may act as inhibitors when biochemically converting carbohydrates in hydrolysates into value-added products. [ABSTRACT FROM AUTHOR] more...

Sulfur-free pulping has an environmental advantage over the traditional kraft process. This article describes the combustion properties of the black liquors produced from silver birch (Betula pendula) sawdust using three different cooking processes: two sulfur-free cooks (soda-anthraquinone and oxygen-alkali), and one reference kraft cook. It also considers the corresponding black liquors from an integrated forest biorefinery, in which a hot-water pretreatment of feedstock was performed prior to pulping. With the same cooking time, the total burning times for the sulfur-free black liquors were higher (15–55%) than those for the conventional kraft black liquors. However, no significant differences were noted between the total burning times for black liquors from pretreated feedstock and those from untreated feedstock. Especially in the case of untreated feedstock, the results showed that the kraft black liquors typically swelled more (25–45%) than the sulfur-free black liquors. It was further observed that the kraft and soda-anthraquinone black liquors from the untreated feedstock swelled more than those from the pretreated feedstock, while the oxygen-alkali black liquors swelled less. [ABSTRACT FROM AUTHOR] more...