Liquefaction Products Research Articles

Enhanced hydrothermal liquefaction of tires using zinc and MoS2

This study introduces a novel approach for tire liquefaction employing zinc and unsupported catalyst MoS2 to mitigate oxygen, nitrogen, and sulfur content, while inhibiting poly-aromatic formation. Autoclave experiments were conducted under subcritical water conditions at 360 and 410 °C. Comprehensive characterization of char and oil was performed, encompassing elemental analysis, functional-group assessment, and composition analysis using gas chromatography-mass spectrometry (GC-MS) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). During the liquefaction, zinc metal pellets react with water to form ZnO and hydrogen, aiding hydrogenation, and MoS2 preserves its catalytic stability. ZnO shows a catalytic effect on deoxygenation, desulfurization, and denitrification reactions. However, the reaction between ZnO and H2S is not favorable under hydrothermal conditions. Zinc and MoS2 synergistically promote cracking of heavier compounds into lighter ones, particularly evident at higher temperatures, without diminishing the overall oil yield. Incorporating zinc pellets and MoS2 slightly facilitates sulfur and oxygen migration from liquid to solid and gas phases. FT-ICR MS analysis reveals oxygen, sulfur, and nitrogen-containing compounds in heavy fraction of oils. The oxygen-containing compounds, predominantly comprised of stearic acid and its derivatives, are identified. Concurrently, the nitrogen-containing compounds manifest primarily as basic nitrogen compounds. MoS2 possesses the capability of forming more N-containing compounds, leading to the generation of a broader spectrum of N-containing compounds. This work elucidates the synergistic role of zinc-assisted catalysis and MoS2, offering insights into tire liquefaction mechanisms and product composition, vital for sustainable waste management and resource recovery.

Optimization of reed-based polyol production driven by response surface methodology and machine learning: Process modeling and hydroxyl value prediction

In pursuit of sustainable development goals, the transformation of biomass resources into high-value chemicals has become a focal point within the academic community. Despite being a biomass resource, reed (Phragmites australis) has not yet fully realized its potential in the production of bio-based polyols. This study utilized Response Surface Methodology (RSM) and an Artificial Neural Network (ANN) enhanced by a Genetic Algorithm (GA) to model and optimize the liquefaction process of reeds. Furthermore, this study employed a pre-existing predictive model to estimate the hydroxyl value of reed-derived liquefaction products, thereby aiming to curtail expenses during the biomass chemical development phase. The results demonstrated that both the RSM and GA-ANN models accurately predict bio-polyol yield, with the RSM model outperforming the ANN model. Based on optimal conditions predicted by the RSM model, the best experimental process parameters were established: raw material particle size 2–12 mesh, solid-liquid ratio 5:1, glycerol content 32.5 %, catalyst content 3.6 %, temperature 169 °C, and reaction time 58 minutes. Under these conditions, the polyol yield reached 89.145 %, with a relative deviation of 2.366 %, and the bio-polyol exhibited a viscosity of 0.51 Pa·s. The predicted hydroxyl value for the bio-based polyol was found to be 399.19 mg KOH/g. The liquefied product is rich in hydroxyl groups, indicating its potential application value in preparing bio-based polymer materials. This study introduces innovative approaches to the economical production of bio-based polyols at the laboratory scale, which may pave the way for their broader industrial implementation.

A new interpretation of soft-sediment deformation features (SSDs) in the Parktown Formation (lower West Rand Group); the physical processes of deformation during deposition

Abstract In the Parktown Formation of the lower West Rand Group (Witwatersrand Supergroup), remarkably well-preserved soft-sedimentary deformation features (SSDs) occur in a number of locations in three stratigraphic horizons across the Vredefort Mountainland and in key sites in Johannesburg. The SSDs were the inevitable products of static liquefaction during early deposition in the Witwatersrand Basin. The trigger to static liquefaction is interpreted to be autogenic and related to cyclic fluctuations in pore fluid pressure(s) during capped dewatering. Allogenic triggers are not indicated. We suggest that static liquefaction was an integral physical process to sediment deposition on the Parktown Formation offshore platform, but a process not previously recognised as important to the modification of the West Rand Group stratigraphy across the Witwatersrand Basin.

Optimizing phase equilibrium predictions for the liquefaction of supercritical water gasification products: Enhancing energy storage solutions through advanced thermodynamic modeling

Supercritical water gasification products typically consist of a vapor mixture consisting of H2 and CO2 with high pressure. Liquefaction of supercritical water gasification products not only allows the vapor mixture to be reduced in volume for easy transportation, but also allows liquid CO2 to be obtained from it, and also serves as a form of energy storage. Under the existing thermodynamic model, the prediction of the liquefaction dew point under high pressure is easily diverged and the accuracy is not enough. In this paper, we obtain the value of CO2+H2 binary interaction coefficient under high pressure kij=0.146 by the fitting method and, which improves the convergence of the predicted phase equilibrium data at high pressure and obtains the results with higher accuracy. In the prediction of dew point of supercritical water gasification products, the fluctuation of H2 content has little effect on the liquefaction pressure, and more significant is the effect of the liquefaction temperature, and it is more economical to carry out the liquefaction work within the range of −30 °C to −5 °C. At the same time, in the liquefaction products lower than −10 °C, the liquid CO2 with the mole fraction of more than 0.9 can be obtained.

The liquefaction characteristics of poplar under CuMgAlOx catalysis in supercritical methanol

AbstractIn an effort to explore the potential energy of biomass and reduce industrial reliance on fossil fuels, this study investigates the liquefaction of poplar wood using supercritical methanol and a CuMgAlOx catalyst. It assesses the composition of liquefied products and performs a comprehensive life‐cycle assessment. Results display that at 360°C, with 1 h of CuMgAlOx, poplar wood's conversion rate reached 98.4%. The proportion of alcoholic compounds in the liquefaction products increased dramatically from 7.99% without a catalyst to 70.81% with it, a rise of 786.23%. Moreover, the process's global warming potential (GWP) intensity is significantly lower at 0.886 gCO2eq/MJ compared to the 93 gCO2eq/MJ from conventional petroleum refining, underscoring its substantial emission reduction potential.

Effects of composite soil conditioner on soil properties and corn yield in a saline–alkali soil

AbstractBiochar is widely used in agricultural production because of its ability to improve the physical and chemical properties of soil and promote crop growth. In this study, a combination of different biochar and lake sediments were used to improve saline soils. The four raw materials, including corn stalk and chicken manure liquefaction product (SMLP), rice husk charcoal (RHC) and two types of sediment (S‐1 and S‐2), which was used to improve the saline–alkali soil, respectively. The most significantly effective applied on the soil was when the composite soil conditioner (CSC) prepared by mixing SMLP, RHC, S‐1 and S‐2 at 5:20:6000:500 t·100 ha−1. The results of soil experiments using the above blending levels showed that the spike weight, plant height and root length of corn increased by 12.49%, 47.17% and 22.10%, respectively, and the pH and electrical conductivity (EC) of soil decreased by 4.83% and 24.02%, respectively. The contents of soil nutrients, soil organic matter (SOM), water content (WC) and soluble cations (K+, Ca2+ and Mg2+) all presented an increasing trend, and the contents of Na+ and soluble anions (Cl−, CO32−, HCO3− and SO42−) of soil showed a downward trend. Accordingly, the composite soil conditioner with biochar and dredged sediment achieves a synergistic improvement in soil physical structure and an increase in nutrient content, which is beneficial for promoting the growth characteristics and yield of corn.

A review of the co‐liquefaction of biomass feedstocks and plastic wastes for biofuel production

AbstractInterest has emerged recently in addressing the long‐standing issue of waste plastic disposal and environmental challenges through the co‐liquefaction of waste plastics with eco‐friendly renewable biomass resources, including microalgae biomass and lignocellulosic biomass, to produce biofuels. Co‐liquefaction provides a viable alternative for managing plastic waste while contributing to biofuel production. The purpose of this article is to provide a comprehensive review of the advances in the co‐liquefaction of various mixtures of plastic waste and different types of biomass feedstocks (lignocellulosic and algal) for the production of biofuels.The influence of various reaction parameters, such as feedstock composition (blending ratio), temperature, catalyst type and loading, solvents, and reaction time on the product yield are explored. The synergistic interaction during the co‐liquefaction of biomass and plastic and the distribution and properties of biofuel products are also discussed.The findings demonstrate that maximum product yields vary depending on the final temperature, and the blending ratio plays a crucial role in determining the distribution of liquefaction products. Of particular interest is biocrude oil, the components of which are influenced by the composition of the feedstock material. The distribution of organic elements in the biochar is contingent upon the type of plastic used. Although the analysis of gas‐phase components is often overlooked, the reaction medium's composition is shown to impact the resulting gas composition.Finally, based on the insights gleaned from the literature, this review presents future perspectives on the subject matter. In general, the co‐liquefaction process offers a viable option for sustainable biofuel production and is a promising approach to address the waste plastics disposal challenges effectively, contributing to the valorization of plastic waste to achieve a circular bioeconomy in the future.

Estimation of Fuel Properties for the Heavy Fraction of Biomass Pyrolysis Oil Consisting of Proposed Structures for Pyrolytic Lignin and Humins

The organic component of biomass pyrolysis oils is composed of a light fraction (C2–C4 volatiles, sugar- and lignin-derived monomers) and a less polar heavy fraction (pyrolytic lignin/humins, greater than approximately 200 g/mol). Importantly, this heavy fraction can account for roughly one-third to one-half of the total pyrolysis oil. While the composition and characteristics of the light fraction are generally well understood, research is still needed for the characterization of the heavy fraction. Some important thermodynamic fuel properties of this fraction are the heat of combustion, normal boiling point, heat of vaporization, and flash point, which are (computationally) estimated in this work with regularized regression and empirical correlations. The quantification of these properties has implications on downstream utilization, particularly in the context of co-processing bio-oils with plastic and coal liquefaction products and/or crude petroleum. Finally, challenges and opportunities for (experimental) work are discussed for the advancement of sustainable valorization of biomass pyrolysis oils.

Deduction of lignite liquefaction mechanism based on carbon structure analysis and free radical determination

The liquefaction performance of lignite is closely related to its structural evolution. The carbon structure and the free radical concentrations of Naomaohu (NMH) coal and liquefaction products were characterized by modified nuclear magnetic resonance (NMR) spectroscopy and electron paramagnetic resonance (EPR), respectively. The results showed that the oil yield increased gradually with the increase in temperature, and it reached a maximum of 64.91% at 430 °C. The carbon spectrum of the liquefied oil showed that the increase in temperature had little effect on the aromatic carbon connected with the aliphatic carbon, but had a greater effect on the aromatic proton carbon of the liquefied oil. The stability of aromatic carbon in asphaltene was greater than that of aliphatic carbon, and the temperature rise had a significant impact on the different types of aliphatic carbon of the asphaltene. The aromatic side chain of asphaltene gradually broke, and the bridgehead carbon content of the aromatic carbon increased due to the intensification of the condensation reaction at high temperature. On the other hand, the concentration of free radicals in liquefied oil increased with temperature, while the concentration of free radicals in asphaltene first increased and then decreased with temperature, indicating a positive correlation between its change trend and respective yield. With the increase in temperature, the aromatic ring substances with strong bond energy were gradually opened, the side chains were broken, thus forming more low molecular compounds. In summary, based on the above changes in the carbon structure and free radicals, the lignite pyrolysis and liquefaction mechanism have been deduced at the molecular level.

Yield and distribution of products of lignin liquefaction catalyzed by molybdenum-vanadium-phosphorus heteropolyacids

ABSTRACT This paper focuses on the performance of Molybdenum-vanadium-phosphorus heteropolyacids (PMo12-xVx) with different V-doped amounts in catalyzing the conversion of lignin to bio-oil, and the distribution of liquefied products. Molybdenum-vanadium-phosphorus heteropolyacids (PMo11V1, PMo10V2, PMo9V3) with different amount (0, 2.5, 5, 10 wt%) were used to catalyze lignin liquefaction. The experimental results showed that PMo12-xVx could effectively catalyze the depolymerization of lignin to bio-oil, and the doping amount of the V atom in PMo12-xVx affects the distribution of lignin depolymerization products. The highest bio-oil yield (53.62wt%) and conversion (57.83wt%) could be obtained from lignin liquefaction at 2.5 wt% PMo9V3. With the increase of PMo12-xVx V-atom doped amount, the content of aliphatic hydrocarbons increased from 3.14% to 40.58%, the content of vanillin increased from none to 8.9%. Based on the analysis of bio-oil, FT-IR data, and DFT simulation results, it was found that the selective cleavage of the Cα-Cβ bond and the ring-opening of the carbon at the methyl end of lignin were the main reasons for the high yield of vanillin and aliphatic hydrocarbons during the depolymerization of lignin catalyzed by PMo12-xVx. Finally, a possible reaction pathway for the PMo12-xVx-catalyzed depolymerization of lignin to vanillin and aliphatic hydrocarbons was proposed.

Direct Liquefaction of South African Vitrinite- and Inertinite-Rich Coal Fines.

In this investigation, coal fines enriched with inertinite were used for direct liquefaction experiments. For comparison, a vitrinite-rich coal typically utilized in coal-to-liquid processes was also employed. To assess the impact of mineral matter content, demineralization was used to remove most of the inorganic constituents. The findings revealed that the inertinite-rich coal exhibited lower liquefaction conversions due to a reduced proportion of reactive macerals and elevated levels of inorganic mineral matter. These conversion values exhibited a strong correlation with the quantity of reactive macerals present in the parent coals. For the inertinite-rich coal, the presence of inorganic mineral matter impeded the liquefaction process but facilitated the CO2 gasification reactions of the derived chars. To evaluate their potential in gasification processes, CO2 gasification experiments were conducted and the reactivities and apparent gasification activation energies of both coal chars, liquefaction residue chars, and preasphaltene and asphaltene (PAA) chars were calculated. These calculations were carried out using the random pore model (RPM) and volumetric reaction model (VRM). The chemistry, reactivity, and kinetics of residue gasification conversion are not thoroughly understood, yet they hold significant importance in optimizing syngas production within gasification processes. The findings from this work highlight significant differences in liquefaction conversion values, product distribution, and composition. These differences are influenced by factors such as maceral composition, inorganic mineral matter content, hydrogen-donor capabilities of the solvent, and liquefaction reaction temperatures. Additionally, these variables affect the CO2 gasification reactivity of liquefaction solid residue chars.

Solvent processing for improved separation of hydrothermal liquefaction products

Solvent extraction and separation of HTL products using naphtha range hydrocarbons was studied with the aim of decreasing operational hazards while improving scalability, reliability, and yields.

Molecular composition of direct coal liquefaction products obtained from the Shenhua industrial plant

The China Shenhua company has built and operated the only large industrial direct coal liquefaction (DCL) plant in the world for 15 years, with an oil product capacity of one million tons per year. However, there is insufficient information on the chemical composition of its products. In this study, the liquefaction product, including the distillate oil and the vacuum residue, as well as the circulating solvent were characterized by gas chromatography – mass spectrometry (GC–MS) and high-resolution mass spectrometry. The liquefaction oil has lower H/C ratio and higher oxygen and nitrogen contents compared to hydrogenation products derived from petroleum. The major component of the liquefaction oil is middle-temperature distillate, which is approximately 70 wt% concentrated in the range of 200–350 °C. Pyrene and perhydropyrene are the most abundant compounds in the liquefaction oil. Hydrocarbons with 1–4 aromatic rings were detected in the liquefaction oil, with skeletons of benzene, biphenyl, naphthalene, fluorene, phenanthrene, pyrene, etc.. Various partially hydrogenated and perhydrogenated aromatic compounds were identified in the oils and they even constitute the major component of the circulating solvent. 2,3-Dihydro-1H-phenalene was also found in high-relative abundance in the oils and has potential to be used as a marker for coal liquefaction produced through hydrogenation processes. Partially hydrogenated polycyclic aromatics exhibit higher dehydrogenation activity compared to tetralin. The organic component in the vacuum residue account for around 60 wt%, with toluene insoluble matter accounting for more than one third. The toluene soluble fraction has an H/C ratio of 0.82 and is mainly composed of aromatic with 4–8 rings. The molecular size and condensation degree of the residue are much higher than those of other fossil fuel-derived aromatic-rich substances. Further studies are necessary to evaluate whether aromatic hydrocarbons with such a high condensation degree are suitable for producing high-performance carbon materials.

Evaluation of sugar cane bagasse hydrothermal liquefaction products for co-gasification with coal as green coal pellet production

This study investigates the production and properties of green coal pellets formed by combining hydrochar and coal in different ratios (3,1, 1:1, and 1:3). It was found that higher ratios of hydrochar to coal resulted in increased mechanical strength of the green coal pellets, highlighting the binding properties inherent in hydrochar. Furthermore, all the green coal and hydrochar pellets exhibited remarkable hydrophobic qualities. Among the different ratios tested, the green coal pellets composed of equal amounts of hydrochar and coal demonstrated the most favourable pyrolysis behaviour based on these indices. The gasification reactivities (R50%) at 1000 °C were measured as 107.9 min−1 for hydrochar pellets, 28.2 min−1 for sugarcane bagasse pellets, and 17.7 min−1 for coal. By blending coal with hydrochar, the green coal pellets exhibited improved pyrolysis and gasification properties compared to coal alone. Notably, the synergistic effect observed in the green coal samples increased with higher ratios of hydrochar.

Anaerobic digestion of aqueous product of co-hydrothermal liquefaction of beverage waste and sewage sludge: Reduction of toxicity and energy assessment

Beverage waste and sewage sludge are two of the most generated waste-based biomasses. Recently, the production of biocrude through the hydrothermal liquefaction (HTL) of both wastes independently or jointly resulted in the generation of an aqueous byproduct (ACP) of high dissolved organic carbon. The high dissolved organic carbon means that ACP can be digested anaerobically to recover more bioenergy products like methane. This study investigated the anaerobic digestion (AD) of ACP produced from co-HTL of beverage waste [winery rose lees (RL)/brewery trub (BT)] and primary sludge (PS) with reference to the quantity and energy content of methane produced as well as the suitability of digestate as an organic fertilizer. Results indicated that ACP generated from the HTL of combined RL and PS (RLPS) produced the highest specific methane yield of 317 mL/gCOD and energy recovery of 80.64% while ACP generated from PS produced the lowest specific methane yield of 26 mL/gCOD and energy recovery of 6.62%. Results also indicated the N/P ratio of the anaerobic digestate makes it suitable for fertilizer application although it needs to be supplemented by K, Ca, and Mg. The results of this study proved that ACP produced during the HTL processing of mixed sewage sludge and beverage waste generates higher methane yield than what could be generated if both wastes are not mixed. This study emphasized that efficient process optimization and energy recovery can be obtained in AD of HTL ACP using a mixed feedstock rather than single feedstocks.

Eco-friendly phenol formaldehyde resin wood adhesive from bagasse lignin liquefaction

Liquefaction products were prepared using bagasse lignin and phenol as raw materials and sulfuric acid as catalyst. Liquefaction products as a substitute for phenol were applied to synthesize bagasse lignin-based phenol formaldehyde (BLPF) resin. Compared with the deep red phenol formaldehyde (PF) resin, the appearance of BLPF resin was dark brown, its solid content was 50.97%, swelling degree was 78.16%, pH was 9.36, storage life was 25–30 d, all of these parameters were lower than PF resin. The introduction of liquefaction products has undermined the bonding properties of resin but enhanced its environmental performance. Compared with the plywood made with PF resin, the plywood made with BLPF resin had lower dry bonding strength (1.99 ± 0.17 MPa, decreased by 0.29 MPa) and wet bonding strength (1.50 ± 0.11 MPa, decreased by 0.24 MPa). Besides, the formaldehyde emission of BLPF resin decreased from 1.134 to 0.641 mg/L, and the weight loss increased from 10.81% to 12.49%. Finally, the functional mechanism of liquefaction products of bagasse lignin on BLPF resin was discussed through the utilization of various precision instruments.

Preliminary results of the solid-state C-13 NMR study of Mongolian coals: Implications for oil and gas potential and liquefaction reactivity

Chemical structures of five coals from Mongolia were studied using solid-state C-13 NMR and oil and gas potential as well as yields of liquefaction products of the coals have been predicted. Pennsylvanian ZG, Upper Permian TT and Lower-Middle Jurassic AT-5 coals might have more potential for gas due to abundant aliphatic and aromatic CH3 carbons. Lower-Middle Jurassic KH coal probably has more potential for oil because of its increased CH2 content. Lower Cretaceous SO-3 coal may have more potential for gas, but significant amount of non-hydrocarbon gases could also be generated simultaneously. The prediction of yields of liquefaction product shows that ZG, TT and AT-5 and KH coals could yield similar hydrocarbon gas, oil and residue. Cretaceous SO-3 coal is predicted to give the lowest yields of oil, hydrocarbon gas and residue compared with others. KH sample has the highest oil yield due to its high content of CH2.
 Keywords: coal, petroleum potential, NMR, Mongolia

Removal of pollutants from aqueous product of Co-hydrothermal liquefaction: Adsorption and isotherm studies

Hydrothermal liquefaction (HTL) is an attractive technology for the conversion of wet waste into biofuel and co-HTL has been touted to increase the quality of products. However, the recovery of energy from wastewater byproduct called aqueous co-product (ACP) is limited due to the presence of toxic inhibitory substances. Adsorption has been countenanced to remove these toxic compounds but there has not been a distinct comprehensive adsorption isotherm study to explain the interaction between the adsorbate molecules and the adsorbent sites. This study investigated the sorption mechanism of oxidizable reducing pollutants measured as chemical oxygen demand (COD); heavy metals (boron and copper); and phenols from ACP samples obtained from co-HTL of brewery trub (BT), and primary sludge (PS) onto granular and powdered activated carbon (GAC and PAC). Conventional isotherm models such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich were used for data analysis. Results indicated that the adsorptive capacity (qe) of PAC was greater than GAC in COD adsorption (BT−1947 > 234; BTPS−617 > 245; PS−289 > 207), boron adsorption (BTPS−70 > 7; PS−53 > 49), copper adsorption (BT−5 > 1; BTPS−3 > 2; PS−1.3 > 1.1) and phenol adsorption (BT−1340 > 356; BTPS−1587 > 253; PS−460 > 245) in mg/g, μg/g, μg/g, and μg/g respectively. Comparing the adsorption of pollutants onto PAC and GAC, this study observed that PAC followed the Temkin, and Dubinin-Radushkevich models in the adsorption of the four pollutants while GAC followed the Freundlich and Langmuir models in the adsorption of phenol and copper, and Temkin, and Dubinin-Radushkevich in the adsorption of COD and boron. This study proved that combining feedstock in HTL (co-HTL) does not only change the quality of the ACP but also changes the dynamics of the adsorption isotherms. The Free Energy Change (ΔG0) result showed a spontaneous reaction in the adsorption of copper and phenol. This study presents an adsorption equilibrium information for the interpretation of adsorption isotherms for the overall improvement of adsorption mechanism pathways and the effective design of adsorption systems for the treatment of ACP.

Solvothermal co‐liquefaction of wastes from Citrus limetta fruit processing

AbstractBACKGROUNDLiquefaction of biomass has an advantage over other thermochemical processes of conversion and its co‐liquefaction aims to overcome the restrictions and limitations imposed upon single feedstock liquefaction. Valorization of Citrus limetta peel and pulp wastes by their co‐liquefaction in a hydrogen‐donor solvent such as methanol was chosen as an objective herein for efficient conversion of raw materials to obtain better quality biocrude.RESULTSA maximum biocrude yield of 11.25 wt. % was obtained from solvothermal co‐liquefaction of Citrus limetta peel and pulp biomasses at 260 °C temperature, with 30 min residence time, at three different ratios of biomass to solvent (1:2, 1:3 and 1:4). This was higher than the biocrude yield from liquefaction of individual C. limetta pulp biomass as well as other studies on similar citrus fruit wastes. The higher heating value (HHV) of biocrude was raised to 25.72 MJ kg−1 at 1:3 biomass:solvent ratio by co‐liquefaction, showing its synergy over individual C. limetta peel biocrude. The presence of esters, ketones, alcohols, hydrocarbons and fatty acids in the biocrude product were found from Gas Chromatography–Mass Spectrometry (GC–MS) results. The biochar obtained was mesoporous in nature and could be employed for adsorption in bioremediation of water and soil.CONCLUSIONCo‐liquefaction of homogeneous lignocellulosic biomasses have the ability to boost production and the quality of the biocrude and biochar attained in comparison to products of individual liquefaction. Future studies on upgrading the quality of products are required. © 2023 Society of Chemical Industry (SCI).

Comparative study of liquefaction behavior and products from brown-rotted wood and sound wood

Comparative study of liquefaction behavior and products from brown-rotted wood and sound wood