Jingxin Wang

Directional liquefaction coupling fractionation of lignocellulosic biomass for platform chemicals

Conventional thermochemical liquefaction of lignocellulosic biomass produces an unpredictable complex mixture of oxygenated products, which creates techno-economic barriers during subsequent upgrading processes. The improvement of the quality of liquefied products is a critical step before the valorization of liquefied lignocellulosic biomass. We are introducing a novel “directional liquefaction” process which harnesses stepwise precipitation of hydrophobic compounds from the liquefied products to form two groups of chemicals: monosaccharides (sugar derivatives) and aromatic platforms. As evidenced in the results of the GC-MS analysis, the sugar platform chemicals, which were generated from carbohydrates, contained five-carbon and six-carbon sugar derivatives, with a total purity higher than 93%. The aromatic platform chemicals with different molecular distributions, mainly from the cleavage of the dominant β-O-4, 4-O-5 linkages in lignin, were fractionated stepwise by gradual removal of the solvent. The platform chemicals make it possible to design the final products due to their similar physiochemical properties within each fraction, and have great potential for commercial production of value added liquid fuels and fine chemicals using mild processing conditions. Additionally, we propose the mechanisms based on our investigation on the decomposition pathways during “directional liquefaction” using GC-MS and 2-dimensional NMR analyses. Overall, the potential of a catalytic refining process for integrated valorization of both carbohydrates and lignin parts in lignocellulosic biomass is the basis of our report.

Simulating Cut-to-Length Harvesting Operations in Appalachian Hardwoods

Abstract Cut-to-length (CTL) harvesting systems involving small and large harvesters and a forwarder were simulated using a modular computer simulation model. The two harvesters simulated were a modified John Deere 988 tracked excavator with a single grip sawhead and a Timbco T425 based excavator with a single grip sawhead. The forwarder used in the simulations was a Valmet 524 machine with 2.4-meter log bunks. Production rates and costs were examined for a wide range of even-age oak forest stand conditions. The simulation results suggest that when the tree’s DBH is less than 26 cm, harvesting using the Timbco T425 is about 30% more expensive than using the John Deere 988. However, if the tree is larger than 26 cm of DBH, the unit cost of the Timbco T425 was about 8% less than that of the John Deere 988. The balanced John Deere 988 CTL system was 31% more productive and 8% more expensive than the balanced Timbco T425 CTL system in the 20 to 36 cm DBH range. General regression equations were developed for estimating the productivity and cost for the range of conditions simulated. The results should be valuable to managers, planners, and loggers considering the use of CTL systems in this region.

Effects of seasonal snow on the growing season of temperate vegetation in China

Variations in seasonal snowfall regulate regional and global climatic systems and vegetation growth by changing energy budgets of the lower atmosphere and land surface. We investigated the effects of snow on the start of growing season (SGS) of temperate vegetation in China. Across the entire temperate region in China, the winter snow depth increased at a rate of 0.15 cm yr(-1) (P = 0.07) during the period 1982-1998, and decreased at a rate of 0.36 cm yr(-1) (P = 0.09) during the period 1998-2005. Correspondingly, the SGS advanced at a rate of 0.68 day yr(-1) (P < 0.01) during 1982-1998, and delayed at a rate of 2.13 day yr(-1) (P = 0.07) during 1998-2005, against a warming trend throughout the entire study period of 1982-2005. Spring air temperature strongly regulated the SGS of both deciduous broad-leaf and coniferous forests, whereas the winter snow had a greater impact on the SGS of grassland and shrubs. Snow depth variation combined with air temperature contributed to the variability in the SGS of grassland and shrubs, as snow acted as an insulator and modulated the underground thermal conditions. In addition, differences were seen between the impacts of winter snow depth and spring snow depth on the SGS; as snow depths increased, the effect associated went from delaying SGS to advancing SGS. The observed thresholds for these effects were snow depths of 6.8 cm (winter) and 4.0 cm (spring). The results of this study suggest that the response of the vegetations SGS to seasonal snow change may be attributed to the coupling effects of air temperature and snow depth associated with the underground thermal conditions.

The effect of bio-carbon addition on the electrical, mechanical, and thermal properties of polyvinyl alcohol/biochar composites

The composites of polyvinyl alcohol and bio-carbon (i.e. biochar) were prepared by a solution casting method to investigate their electrical conductivity and mechanical and thermal properties. The polyvinyl alcohol/biochar composites filled with 2 wt% and 10 wt% biochar exhibit a similar electrical conductivity to most carbon nanotube and graphene reinforced polyvinyl alcohol composites. Results of mechanical tests indicate that addition of the biochar reduced the tensile strength of the polyvinyl alcohol/biochar composites. However, the tensile modulus and storage modulus above the glass transition temperature were improved through the addition of biochar. The results of thermal gravimetric analysis and differential scanning calorimetry indicated that addition of biochar increased the thermal decomposition temperature of polyvinyl alcohol/biochar composites. These results demonstrate that biochar holds great potential for replacing the carbon nanotubes and graphene as a filler of polymers in electrical applications.

Factors Affecting Spatial Variation of Annual Apparent Q10 of Soil Respiration in Two Warm Temperate Forests

A range of factors has been identified that affect the temperature sensitivity (Q10 values) of the soil-to-atmosphere CO2 flux. However, the factors influencing the spatial distribution of Q10 values within warm temperate forests are poorly understood. In this study, we examined the spatial variation of Q10 values and its controlling factors in both a naturally regenerated oak forest (OF) and a pine plantation (PP). Q10 values were determined based on monthly soil respiration (RS) measurements at 35 subplots for each stand from Oct. 2008 to Oct. 2009. Large spatial variation of Q10 values was found in both OF and PP, with their respective ranges from 1.7 to 5.12 and from 2.3 to 6.21. In PP, fine root biomass (FR) (R = 0.50, P = 0.002), non-capillary porosity (NCP) (R = 0.37, P = 0.03), and the coefficients of variation of soil temperature at 5 cm depth (CV of T5) (R = −0.43, P = 0.01) well explained the spatial variance of Q10. In OF, carbon pool lability reflected by light fractionation method (LLFOC) well explained the spatial variance of Q10 (R = −0.35, P = 0.04). Regardless of forest type, LLFOC and FR correlation with the Q10 values were significant and marginally significant, respectively; suggesting a positive relationship between substrate availability and apparent Q10 values. Parameters related to gas diffusion, such as average soil water content (SWC) and NCP, negatively or positively explained the spatial variance of Q10 values. Additionally, we observed significantly higher apparent Q10 values in PP compared to OF, which might be partly attributed to the difference in soil moisture condition and diffusion ability, rather than different substrate availabilities between forests. Our results suggested that both soil chemical and physical characters contributed to the observed large Q10 value variation.

Turbidity and suspended-sediment changes from stream-crossing construction on a forest haul road in West Virginia, USA

A forested headwater watershed in West Virginia was monitored to examine changes to in-stream turbidity following the construction of a 0.92 km (0.57 mi) haul road. Due to the design of the study, most of the sediment that entered the stream following road construction was known to result from the stream crossings and approaches to the crossings. Stream-water samples collected daily and sequentially during stormflow from 1999 through 2005 were used to interpret the effects of stream-crossing construction on turbidity and suspended-sediment concentrations (SSC). Daily and stormflow turbidity and SSC values increased as a result of the construction. Average sediment loads (kg per storm) and total annualized sediment loads (kg per year) also increased significantly, both by a factor of about 1.8. Sediment delivery to the stream was caused by mechanical introduction of soil during stream-crossing culvert installation and fill-slope construction in the crossing approaches, and by erosion of those areas due to delays in vegetation re-establishment. Inputs from stream-crossing construction affected the overall sediment regime of the stream; the turbidity-discharge hysteresis changed from the normal clockwise pattern to a counter-clockwise pattern for about seven months. As the crossing fills and approach fill slopes became re-vegetated, they stabilized, and annualized sediment loads declined. However, at the end of the study, sediment exports remained above pre-disturbance levels.

Log Sawing Practices and Lumber Recovery of Small Hardwood Sawmills in West Virginia

A total of 230 logs from two species, red oak (Quercus rubra) and yellow poplar (Liriodendron tulipifera), were measured in five typical hardwood sawmills across West Virginia to evaluate log sawing practices and lumber recovery. Log characteristics such as length, diameter, sweep, taper, and ellipticality were measured in sawmills, while log scale and grade were determined by using the US Department of Agriculture Forest Service grading rules. The characteristics of sawing equipment, such as headrig type, headrig kerf width, and sawing thickness variation, were recorded during the measurement process. A general linear model was used to statistically analyze the relationship between lumber recovery and characteristics of logs and sawing practices. Results indicated that factors such as log grade, log diameter, species, log sweep, log length, and some two-factor interactions significantly affected lumber value and volume recovery.

Appalachian hardwood product exports: an analysis of the current Chinese market.

A mail survey of Appalachian hardwood product exporters was conducted in the fall of 2008 to analyze the export practices for Appalachian hardwood products, specifically the volume of hardwood products exported to the Chinese market, their preferred species, and potential and existing trade barriers between US producers and Chinese customers. Results of the survey showed that the most frequent export destinations of Appalachian hardwood products were Europe, China, Canada, Mexico, and Japan. In 2007, approximately 11.4 million board feet (MMBF, Doyle scale) of hardwood logs and 145.3 MMBF of hardwood lumber were exported to China by the respondents. Approximately 37 percent of the respondents who exported hardwood products to China exported red oak logs, followed by white oak, black walnut, black cherry, and hard (sugar) maple. The top species of hardwood lumber exported to China were red oak, white oak, yellow poplar, black walnut, hickory, cherry, hard maple, and soft maple. Respondents indicated that transportation freight costs and payments are the limiting factors when considering expanding business overseas. The continued decreasing hardwood price has put more pressure on hardwood products exporters to maintain profit margins. Because of the current economic downturn, hardwood production in the Appalachian hardwood region has declined by more than 40 percent. Exports of hardwood products to China will be affected to some extent. However, it is expected that China will remain an important overseas market in the near future.

Application and Effectiveness of Forestry Best Management Practices in West Virginia

The application and effectiveness of forestry best management practices (BMPs) was assessed on 33 harvested sites with streamside management zones (SMZs) throughout West Virginia, which coincided with 116 sites of statewide BMP compliance assessment. The sampled sites either showed evidence of activity in the SMZ or a stream crossing was found due to the harvest. Four checklists derived from the West Virginia BMP guidelines were used to assess 27 BMPs on haul roads, skid trails, at landings, and in SMZs. Rankings were analyzed statistically to examine the differences of BMP application and effectiveness among forester involvement, ownership, harvest, and stream type. The overall BMP application and effectiveness on sites with SMZs averaged 85% and 80% in West Virginia. Results also indicated that the BMP application and effectiveness rates were higher on industry owned lands or with forester involved than on private lands or without forester involvement. The findings should be useful to aid in future assessments of application and effectiveness of BMPs across West Virginia or in the region.

Differential effects of conifer and broadleaf litter inputs on soil organic carbon chemical composition through altered soil microbial community composition

A strategic selection of tree species will shift the type and quality of litter input, and subsequently magnitude and composition of the soil organic carbon (SOC) through soil microbial community. We conducted a manipulative experiment in randomized block design with leaf litter inputs of four native subtropical tree species in a Pinus massoniana plantation in southern China and found that the chemical composition of SOC did not differ significantly among treatments until after 28 months of the experiment. Contrasting leaf litter inputs had significant impacts on the amounts of total microbial, Gram-positive bacterial, and actinomycic PLFAs, but not on the amounts of total bacterial, Gram-negative bacterial, and fungal PLFAs. There were significant differences in alkyl/O-alkyl C in soils among the leaf litter input treatments, but no apparent differences in the proportions of chemical compositions (alkyl, O-alkyl, aromatic, and carbonyl C) in SOC. Soil alkyl/O-alkyl C was significantly related to the amounts of total microbial, and Gram-positive bacterial PLFAs, but not to the chemical compositions of leaf litter. Our findings suggest that changes in forest leaf litter inputs could result in changes in chemical stability of SOC through the altered microbial community composition.