Wood contains primary extractives, which are present in all woods, and secondary extractives, which are confined in certain wood species. Extractives in wood play a major role in wood-bonding ...processes, as they can contribute to or determine the bonding relevant properties of wood such as acidity and wettability. Therefore, extractives play an immanent role in bonding of wood chips and wood fibres with common synthetic adhesives such as urea-formaldehyde-resins (UF-resins) and phenol-formaldehyde-resins (PF-resins). Extractives of high acidity accelerate the curing of acid curing UF-resins and decelerate bonding with alkaline hardening PF-resins. Water-soluble extractives like free sugars are detrimental for bonding of wood with cement. Polyphenolic extractives (tannins) can be used as a binder in the wood-based industry. Additionally, extractives in wood can react with formaldehyde and reduce the formaldehyde emission of wood-based panels. Moreover, some wood extractives are volatile organic compounds (VOC) and insofar also relevant to the emission of VOC from wood and wood-based panels.
The bark of Pinus radiata is an under-utilized forest residue that is renewable, abundant and has the potential to become a source of sustainable high-value chemicals. However, the use of this bark ...within a biorefinery for advanced applications is hindered by its intractable characteristics: high integrity, complex composition, and high heterogeneity. Most of the bark is burnt to provide energy and heat. The bark contains a high portion of phenolic extractives, constituting a potential source of valuable compounds. It also contains the heteropolymer suberin, a source of unique building blocks for developing innovative materials with potential broad bactericidal properties. Removal of phenolic extractives and suberin from bark simplifies down-streaming pulping processing of bark’s lignocellulosic part. Herein, we describe an effective green strategy to sequentially extract the lipophilic bark constituents and suberin, exploring scCO2 (40, 50 or 60 °C / 200, 350 or 500 bar) and a biocompatible ionic liquid catalyst. The obtained scCO2 extracts had similar diversity of lipophilic compounds and predominantly contained resin acids. Further extraction of the scCO2 extracted bark yielded suberin amounts of 2.25% wt. The bark’s suberin structure shows archetypal chemical features yet has an idiosyncratic high abundance of alkanoic acids, which is not common in most sources. The findings of this opening bark biorefinery study deserve further development and complementary techno-economic analyses to secure new value chains for the bark's major lipophilic compounds consisting of resin acids and bark suberin.
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•High yield extraction of scCO2 soluble lipophilic compounds from pine bark residues.•scCO2 soluble bark constituents are resin acids, alkan-1-ols, alkanoic acids, and terpenes.•Highly esterified cell wall polymer suberin extracted from bark with an ionic liquid.•Dual potential of bark for sequential recovery of its scCO2 soluble compounds and suberin.•Alkanoic acids are highly abundant (>50% wt) in the isolated bark suberin.
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•Rice straw extractives considerably influence the biogas and bioethanol production.•Water extractives reduced the biogas production yield.•Ethanol extractives enhanced the produced ...biogas.•Extractives did not affect the enzymatic hydrolysis yields.•Ethanol yield was improved by water extractives and reduced by ethanol extractives.
Extractives are nonstructural constituents of lignocellulosic materials available in small portions; however, their influence on the bioconversion processes cannot be disregarded. This study evaluated the effect of various concentrations of rice straw water extractives (RWE) and ethanol extractives (REE) on enzymatic hydrolysis, anaerobic digestion, and simultaneous saccharification and fermentation productivity. By increasing the RWE or REE concentration, the glucose yield did not change after 72 h of enzymatic hydrolysis. The RWE increment enhanced ethanol yield to 95.6%. However, the REE increment decreased ethanol yield to 32.1%. Adding RWE caused a considerable reduction in the accumulated biogas and changed the composition of produced biogas from 74% methane to less than 1%. By increasing the REE concentration, the accumulated biogas increased from 167.9 to 524.4 ml/g VS. According to the gas chromatography-mass spectrometry (GC/MS) results, the most abundant RWE and REE components were 3-hydroxy-Spirost-8-en-11-one and guaiazulene, respectively.
Sustainable materials are becoming increasingly important due to environmental concerns and the energy crisis. Non-wood resources such as bamboo are being explored as alternatives to wood-based ...materials to reduce deforestation. However, the chemical properties of these resources determine their usability. This study analyzed the chemical composition and solubility of Bambusa bambos (L.) Voss, a type of bamboo. The effects of age and height position (top, middle, and bottom) on the chemical composition and solubility were also considered. The study followed the standards of TAPPI (Technical Association of the Pulp and Paper Industry) to analyze holocellulose, lignin, and extractive content, and water (hot and cold) and caustic soda (1% NaOH) solubility. The results showed that the chemical composition, i.e., holocellulose, lignin, and extractive, increased while solubility, i.e., cold water, hot water, and NaOH, decreased with the ageing of B. bambos. The average holocellulose, lignin, and extractive contents of three-year-old B. bambos were 70.49%, 27.55%, and 4.54%, respectively. These values were within the range of previous studies, indicating that B. bambos has potential applications in various purposes.
•The chemical compositions increased with the ageing of Bambusa bambos.•The solubility decreased with the ageing of B. bambos.•Three-year-old B. bambos had comparable chemical compositions to wood.•B. bambos has the potential to be used for various purposes.
The colour modification effect of dry thermal treatment was studied in black locust (Robinia pseudoacacia L.), poplar (Populus x euramericana cv. Pannonia), Scots pine (Pinus sylvestris L.), spruce ...(Picea abies Mill.) and larch (Larix decidua L.) species in the temperature range 90-200 °C. Colour data were presented and evaluated in the CIE L*a*b* coordinate system. All thermal treatments applied altered the wood colour throughout the entire cross section regardless of the treatment temperature. At lower temperatures, wood extractives played a decisive role in colour change. The degradation products of hemicelluloses were the major determinant of the change in lightness at 200°C. Redness change in percentage showed much greater alteration than the yellowness and the lightness change. Spruce presented the greatest chromaticity coordinate (a* and b*) alteration among the investigated species. Changes in redness and yellowness followed the Arrhenius law during the investigated dry thermal treatments confirming that the temperature dependence of these colour parameters is exponential for wood material.
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•Despite their small proportion, extractives significantly affected the bioconversion.•Extractives affected enzymatic hydrolysis, SSF, and anaerobic digestion.•Water extractives ...decreased enzymatic hydrolysis yield but not ethanol extractives.•Water extractives decreased ethanol yield, while ethanol extractives increased it.•Extractives reduced the produced biogas yield and composition.
Extractives are a wide range of compounds that make up a small fraction of lignocelluloses, but they can profoundly affect the bioconversion processes of these materials. To investigate the effects of extractives on these processes, pinewood extractives were extracted by water and ethanol as solvents. The composition of extractives was analyzed by GC/MS, and the phenolic contents of extractives were determined by Folin-Ciocalteu assay. Pinewood and extractives-free pinewood were subjected to enzymatic hydrolysis, simultaneous saccharification and fermentation (SSF), and anaerobic digestion in the presence of different concentrations of pinewood water extractives (PWE) and pinewood ethanol extractives (PEE). It was found that PWE and PEE contained 122.7 and 57.9 mg gallic acid equivalent (GAE)/g extract of phenolics, respectively. The GC/MS results revealed that 4-benzyloxy-4- 2,2-dimethyl-4-dioxolanyl butyraldehyde and abietic acid were the most abundant components of PWE and PEE, respectively. The addition of 100 g/L PWE decreased enzymatic hydrolysis glucose yield from 23.3 to 16.8%, and a linear relationship between inhibition and the concentration of PWE was found. Whereas, the addition of 100 g/L PWE decreased the SSF ethanol yield from 16.8 to 4.6%. Accumulated biogas was declined from 107.4 to 16.7 mL/g VS with the addition of 80 g/L of PWE in anaerobic digestion. By increasing the concentrations of PWE from 0 to 80 g/L, accumulated methane also decreased from 91.7 mL/g VS to nearly zero. On the other hand, adding 100 g/L of PEE improved ethanol yield from 15.3 to 28.6%. An increase in the level of PEE from 0 to 40 g/L decreased accumulated biogas from 140.2 to 62.8 mL/g VS. However, it had no significant effect on glucose yield in enzymatic hydrolysis. Although extractives are minor components of lignocellulose, they affect its bioconversion severely, especially biogas production.
Feedstock flexibility is highly advantageous for the viability of (solvent-based) biorefineries but comes with the considerable challenge of having to cope with the varying nature and typically high ...abundance of nonlignocellulose compounds in the most readily available residual biomass streams. Here, we demonstrate that mild aqueous acetone organosolv fractionation of various complex lignocellulosic raw materials (roadside grass, wheat straw, birch branches, almond shells, and a mixed stream thereof) is indeed negatively affected by these compounds and present a versatile strategy to mitigate this bottleneck in biorefining. A biomass pre-extraction approach has been developed to remove the detrimental extractives with (aqueous) acetone prior to fractionation. Pre-extraction removed organic extractives as well as minerals, primarily reducing acid dose requirements for fractionation and loss of hemicellulose sugars by degradation and improved the purity of the isolated lignin. We show how pre-extraction affects the effectiveness of the biorefinery process, including detailed mass balances for pretreatment, downstream processing, and product characteristics, and how it affects solvent and energy use with a first conceptual process design. The integrated biorefining approach allows for the improved compatibility of biorefineries with sustainable feedstock supply chains, enhanced biomass valorization (i.e., isolation of bioactive compounds from the extract), and more effective biomass processing with limited variation in product quality.
Pellets produced from wood, energy grasses and straw present a higher energy density feedstock than wood chips or bales, and therefore reduce the costs of handling, transport and storage throughout ...the supply chain. European specifications provide limits to the proportion of fines (particles less than 3.15mm) allowed in pellets, which refers to the durability of the pellets. Fines have implications for health and safety in supply chains, and cause issues with slag formation in combustion systems. This paper reviews the factors affecting biomass pellet durability. The industrial trade for wood pellets has expanded greatly over the last decade and involves the international trade of tens of million tonnes annually. Due to increasing demands for pellets, there has been growing interest in utilising more varied biomass types. The aim of this review is to examine feedstock qualities and pelleting conditions that produce durable pellets. Pellet durability can be affected by the feedstock characteristics, the moisture content or size reduction during pre-processing, and by pelleting conditions, including the use of binders, feedstock mixes, temperatures or die pressures. Post-production conditions can also affect durability, such as the storage conditions and handling frequency, therefore an understanding of all the factors affecting durability throughout the supply chain is needed in order to prioritise where advances can be made.
Off-gassing and self-heating are the major challenges when it comes to transportation and storage of wood pellets. The heat generated due to self-heating poses a fire risk while off-gassing of toxic ...gasses such as carbon monoxide (CO) and some volatile organic compounds (VOCs) is an environmental and human health risk. With the increase in production volumes of wood pellets which has subsequently increased the amounts of wood pellets in transportation and storage, there is need to find lasting solutions to off-gassing and self-heating of wood pellets. The objective of this study was to test the off-gassing abilities of Scots pine wood pellets produced from sawdust with varying amounts of extractives. The aim is to come up with raw material pre-treatment measures so as to produce wood pellets that are not liable to off-gassing. Six (6) types of sawdust raw materials namely; fresh pine sawdust (FPS), stored pine sawdust (SPS), sawdust plus pine rosin (PRS), sawdust plus linseed oil (LOS), sawdust plus tall oil (TOS) and acetone extracted sawdust (AES) were used to produce the pellets. The produced pellets were then subjected to off-gassing tests under controlled conditions using the ECOM J2KN analyser. The concentrations of carbon monoxide, carbon dioxide and methane increased with storage time but slowed down towards the end of the nine days test period. The formation of these gasses were largely dependent on the type of extractives present in the raw material and not the total extractive content. The formation of methane started later than the other gases and coincided with the time when residual oxygen was depleted.
•Off-gassing of wood pellets is influenced by the type of extractives in the raw material and not the total extractive.•The concentration of off-gasses increases with storage time up to a certain extent.•Stored and acetone extracted pellets lost the ability of fresh pine wood pellets to form gas emissions.•Methane formation in off-gassing of wood pellets is strongly dependent on anaerobic conditions.
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