Wood Chip Size Research Articles

Influence of woodchip size and nitrogen fertilization on carbon dioxide and nitrous oxide emissions from soils amended with orchard biomass

AbstractIncorporating large amounts of woody biomass into soil, such as in whole orchard recycling (WOR), can promote carbon sequestration, nutrient recycling, and ecosystem health in agricultural fields. Yet uncertainty regarding the effects of WOR on soil carbon (C) and nitrogen (N) dynamics influences management decisions. The objective of this research was to evaluate the effects of woodchip (WC) size and interaction with N fertilization on carbon dioxide (CO2) and nitrous oxide (N2O) emissions. An 8‐month incubation experiment incorporating WC (4% w/w, equivalent to ∼40 tons per acre) in four sieved sizes (0.2–1.6, 1.6–3.2, 3.2–6.4, and 6.4–12.7 mm) with and without N applications was conducted. All treatments with WC showed that CO2 emission peaked within the first week, then decreased drastically afterward. The CO2 peak delayed as the peak value decreased (WC size increased). The finest WC (<1.6 mm) yielded the lowest total CO2 emissions and resulted in the greatest increase in soil C at the end of incubation. Nitrogen application reduced total CO2 emissions by 1% in the smallest WC size and by 8%–9% for those larger than 1.6 mm. The N2O emissions spiked following each fertilizer application with lowest total emissions from the smallest WC size, suggesting substantial N immobilization. The results imply that larger WC sizes can delay C mineralization and reduce initial N immobilization risks, but the smallest WC size may have stabilized and increased soil organic carbon. This research increased our understanding on WC mineralization that can be used in WOR management.

Multirate mass transfer simulation of denitrification in a woodchip bioreactor

Denitrifying woodchip bioreactors (DWBs) have proven to be an efficient nature-based solution for nitrate removal. Modeling DWBs is required for improving their design and operation, but is hindered by the complexity of the modeled system where numerous chemical species and model parameters are needed. Reactions inside the woodchips are different from those at the edges, causing chemical localization (i.e., apparent simultaneous occurrence of incompatible reactions). We used the Multi Rate Mass Transfer (MRMT) approach to overcome these problems when simulating reactive transport processes in a DWB located at Kiruna, Sweden. Besides denitrification, other nitrogen-cycling processes (e.g., nitrification, dissimilatory nitrate reduction to ammonium, anammox) and alternative electron donors (e.g. oxygen, sulfate) were also considered. Biomass concentration is incorporated into the biochemical reaction rates, including growth and decay, to characterize microbial catalysis. We found that the MRMT model: 1) can account for the heterogeneity of the porous woodchips; 2) was capable of reproducing the nitrogen species evolution in the DWB with kinetic parameters from the literature; and 3) allows reproducing localized biochemical reactions (e.g., aerobic reactions on the woodchip edges, near the DWB entrance and anaerobic reactions inside); and 4) reproduces the full denitrification reactions sequence, but with the different reactions occurring in different portions of the woodchip (e.g., nitrate to nitrite near the edges and nitrite to nitrous oxide further inside). The latter observation suggests that increasing woodchip size may reduce the outflow of these undesired species.

Influence of storage time and log length on the distribution of wood chip size

Chip size distribution is important in kraft pulping, as it affects chemical use, quality, and yield in pulp production. Pinus taeda logs with two storage periods (0 and 2 weeks) and two log lengths (2.4 and 7.0 m) were processed with a disc chipper. Logs stored for two weeks produced chips with 7% less moisture than logs with no storage period. The storage period significantly influenced the quantities of overthick, accept, pin, and fines classes. Logs stored for two weeks produced 1.7% more overthick, 3.8% more pin, and 1.1% fines than logs with no stocking period. Consequently, the amount of accept produced was 6.2% higher for chips from processing freshly harvested logs. Log length influenced the produced quantities of oversize, overthick, and accept. Logs with a length of 2.4 m produced chips with 1.4% more oversize, 2.5% more overthick, and 4.6% less accept, compared to 7.0 m logs. Thus, it was concluded that Pinus taeda logs with shorter storage periods and longer lengths generate more chips in the “accept” class.

Visualisation of sulphur on single fibre level for pulping industry

In the pulp and paper industry, about 5 Mt/y chemithermomechanical pulp (CTMP) are produced globally from softwood chips for production of carton board grades. For tailor making CTMP for this purpose, wood chips are impregnated with aqueous sodium sulphite for sulphonation of the wood lignin. When lignin is sulphonated, the defibration of wood into pulp becomes more selective, resulting in enhanced pulp properties. On a microscopic fibre scale, however, one could strongly assume that the sulphonation of the wood structure is very uneven due to its macroscale size of wood chips. If this is the case and the sulphonation could be done significantly more evenly, the CTMP process could be more efficient and produce pulp even better suited for carton boards. Therefore, the present study aimed to develop a technique based on X-ray fluorescence microscopy imaging (µXRF) for quantifying the sulphur distribution on CTMP wood fibres. Firstly, the feasibility of µXRF imaging for sulphur homogeneity measurements in wood fibres needs investigation. Therefore, clarification of which spatial and spectral resolution that allows visualization of sulphur impregnation into single wood fibres is needed. Measurements of single fibre imaging were carried out at the Argonne National Laboratory’s Advanced Photon Source (APS) synchrotron facility. With a synchrotron beam using one micrometre scanning step, images of elemental mapping are acquired from CTMP samples diluted with non-sulphonated pulp under specified conditions. Since the measurements show significant differences between sulphonated and non-sulphonated fibres, and a significant peak concentration in the shell of the sulphonated fibres, the proposed technique is found to be feasible. The required spatial resolution of the µXRF imaging for an on-site CTMP sulphur homogeneity measurement setup is about 15 µm, and the homogeneity measured along the fibre shells is suggested to be used as the CTMP sulphonation measurement parameter.

Effects of microwave irradiation on the moisture content of various wood chip fractions obtained from different tree species

The paper proposes the use of microwave irradiation to lower the initial moisture content of wood chips. The study involved willow and fir chips fractionated by means of a sieve separator and unfractionated ash chips. The wood chips were exposed to a constant microwave power of 800 W for 30 s, 60 s, 120 s and 180 s. The chips were weighed before and after irradiation to measure loss of moisture. It was found that the decline in moisture content increased with wood chip size for a given irradiation time and microwave power. The initial moisture content of wood chips was not found to significantly affect loss of moisture as the drying rates of wood chips with higher and lower moisture content exposed to microwaves were not statistically different. The results showed that irradiation intensity increased with the time of exposure to microwaves and unit radiant energy per unit of evaporated moisture decreased with increasing wood chip size in the 3.15–31.50 mm range.

Factors Affecting the Chipping Operation Based on the Screen Size of the Drum Chipper

Forest biomass has recently been highlighted as a renewable energy source in South Korea. As the Renewable Energy Certificate weight has been revised to encourage the use of forest biomass for energy production, forest operations have focused on the development of new technologies and harvesting methods for the extraction and utilization of forest biomass. This study examined the application of a drum chipper to forest biomass and analyzed the effects of screen size (40, 50, 65, and 80 mm) on productivity, cost, and particle size distribution. When the screen size was 40 mm to 65 mm, the chipping productivity improved by up to 3.6 times, the fuel consumption decreased by up to 29.7%, and the chipping cost was reduced by up to 31.9%. The fines content tended to decrease with an increase in screen size. The size of woodchips was less than 100 mm in length and ranged from 10 to 63 mm. The 65 mm screen was the most effective (e.g., producing optimal wood chip size at an acceptable production rate) for the chipping operation. Harvesting methods and drying time are also important factors that determine the utilization efficiency of forest biomass. Therefore, further research should be focused on the effect of moisture content on chipping productivity, power required, and fine particle size in forest biomass productions.

Woodchip size effect on combustion temperatures and volatiles in a small-scale fixed bed biomass boiler

Biomass combustion performance is greatly affected by the particle size distribution, which influences heat and mass transport phenomena. The present work investigates the effect of woodchip size distribution on combustion in a 140 kW underfeed stoker boiler. Three different fuel sizes were prepared, and their combustion performance was measured by monitoring temperatures inside and above the fire pit and the gas composition above the fuel bed. The gas composition was then correlated to the particle mean diameter. Although minor effects could be detected in the temperature and composition of the flue gases, a more uniform spatial distribution of volatiles was observed when employing bigger woodchips. The present results can improve the understanding of the impact of fuel size on the performance of woodchip-fired boilers and can be valuably used for numerical model validation.

Improvement of proximate data and calorific value assessment of bamboo through near infrared wood chips acquisition

In a previous study, a near infrared (NIR) spectroscopy model was developed using a spectra of ground bamboo samples. Although the previous report on ground bamboo described a good performance, operation in the power plant was found to be inconvenient due to preparation costs and labour required for the necessary preparation of ground samples. Thus, this study presents the comparison of the performance of an NIR model that was developed by direct scanning of bamboo chips to the previously developed model for ground samples. Special emphasis is put on the comparison of the spectral reproducibility. Bamboo chip models were developed based on PLS regression with variable selection methods in order to achieve the optimal model. The moisture content (MC) and ash content (A) of the developed bamboo chip models could be applied toward quality assurance. The volatile matter (VM) and fixed carbon (FC) models could be used for approximating predictions. The gross and net calorific value (GCV and NCV) models could be used for most applications. The root mean square (RMS) value of pre-treated spectra of different particle size had no statistically significant differences. The study’s findings indicate that the model developed using NIR spectroscopy protocol with wood chips spectra can be used as a classification tool and is an effective method for estimating bamboo chip energy quality. The big particle size of wood chips affect negatively the prediction model, however, it could be solved through spectral pre-processing technique, thus eliminating the need for grinding feedstock samples.

Influence of the particle size of poplar wood chips on the development of mesophilic and thermotolerant mould during storage and their potential impact on dry matter losses in piles in practice

For efficient provision of wood chips from agriculture and forestry these raw materials must be stored in such a way that mass and energy losses are kept as low as possible. The connections between wood chip size, moisture content, pile temperature, mould concentrations and dry matter loss were examined in practice during storage of wood chips from poplar (Populus) from SRC in covered piles for periods of seven to nine months.Similar temperature curves were measured in the piles in all trials. The curves can be subdivided into characteristic temperature-dependent phases (P) – P1 (frost), P2 (high temperature), P3 (low temperature). In piles with small chips, temperatures measured in P2 (up to 64 °C) were always higher by comparison with those measured in medium chip piles (up to 58 °C). Low mesophilic and thermotolerant mould contents (up to 3.8 lgCFU g−1) as well as low dry matter losses (up to 5.7%) were also recorded. As temperatures drop below 45 °C in P3, mould contents and dry matter losses (up to 16%) increase clearly.In the case of medium chips, highest dry matter losses (up to 10%) occurred already in P2 in presence of high thermotolerant mould content levels (up to 6.2 lgCFU g−1). In order to store larger chips or chopped pieces with low dry matter losses, the process should be designed in such a way that the duration of P2 is minimised. A later harvest at higher outdoor temperatures in spring can also have a beneficial impact on reducing dry matter losses.

Effects of Age and Height on Chemical Properties of Yushania Alpina Grown at Injibara District, Amhara Region, Ethiopia

This paper studied the chemical composition of cultivated 3, 4 and 5 year-old highland bamboo (Y. alpina) which were classified into three position (top, medium and bottom) to determined the main compositions especially cellulose, lignin, extractive and ash content. From all culms representative samples were converted to the required size of wood chips to prepared sample for chemical testing. Then the specimens prepared from bottom, middle and top portions for the three ages were used to determine the chemical properties in accordance to American Society for Testing and Materials (ASTM) standards except for cellulose test determined according to Kurschner and Hoffer method. All parameters in the experiment were expressed by percent based on dry basis. From this research, we have found small but significant increases in mean cellulose content from the base to the top of the culm at all three ages. The lignin content in Y. alpina species of bamboo is in the ranged of 23.04 to 30.03%. The mean values of the chemical constituents in 3, 4 and 5- year-old culms were 51.83, 54.94 and 49.78% for cellulose content, 28.28, 24.99 and 24.53% for lignin content, 7.8, 10.09, and 9.54% for alcohol-toluene extractive, respectively. In general, the comprehensive knowledge of the chemical components in the bamboo species will facilitate the use of the materials in the forestry industrial sector and help to enhance their utilization in the chemical and bio-chemical related industry.

Effects of Age and Height on Chemical Properties of Yushania Alpina Grown at Injibara District, Amhara Region, Ethiopia

This paper studied the chemical composition of cultivated 3, 4 and 5 year-old highland bamboo (Y. alpina) which were classified into three position (top, medium and bottom) to determined the main compositions especially cellulose, lignin, extractive and ash content. From all culms representative samples were converted to the required size of wood chips to prepared sample for chemical testing. Then the specimens prepared from bottom, middle and top portions for the three ages were used to determine the chemical properties in accordance to American Society for Testing and Materials (ASTM) standards except for cellulose test determined according to Kurschner and Hoffer method. All parameters in the experiment were expressed by percent based on dry basis. From this research, we have found small but significant increases in mean cellulose content from the base to the top of the culm at all three ages. The lignin content in Y. alpina species of bamboo is in the ranged of 23.04 to 30.03%. The mean values of the chemical constituents in 3, 4 and 5- year-old culms were 51.83, 54.94 and 49.78% for cellulose content, 28.28, 24.99 and 24.53% for lignin content, 7.8, 10.09, and 9.54% for alcohol-toluene extractive, respectively. In general, the comprehensive knowledge of the chemical components in the bamboo species will facilitate the use of the materials in the forestry industrial sector and help to enhance their utilization in the chemical and bio-chemical related industry.

The Effect of Selected Technical, Technological, and Material Factors on the Size of Juvenile Poplar Wood Chips Generated during Face Milling

The effects of technical, technological, and material factors affecting the size of juvenile poplar wood chips were evaluated. Each analysis was performed on two species of poplar, namely natural poplar Populus tremula L. and plantation poplar clones Populus euramericana Serotina, and on juvenile and mature wood within each poplar species. A cutter with angular geometry was selected for the face milling:  = 55° (angle of cutting wedge),  = 15° (rake angle). The cutting conditions were a feed rate of vf = 2.5 and 15 m·min-1, cutting speed of vc = 30 m·s-1, 45 m·s-1, and 60 m·s-1, and the depth of cut ap = 1 mm. An image analysis of the size of the largest and smallest fraction was performed. Most of the chips generated during the face milling of poplar wood were classified as flat grain wood. A small percentage of the generated chips could be included in the group of rod-shaped fibrous bulk particles with a considerable extension in one direction (smaller fractions generated at a feed rate of 2.5 m·min-1, and at the finest fractions- dust generated in all of the combinations of technical and technological parameters).

Development and test of a simplified method to calculate dry matter loss during open-air storage of poplar wood chips by analysing ash contents

Short rotation coppice (SRC) in agriculture can be established successfully, only if the entire process chain is economically competitive. Despite the substantial dry matter loss (up to 25%) occurring during open-air storage of wood chips, it is the most applied storage technique. Since the particle size of wood chips plays an important role in storage and drying processes, two storage piles (>500 m3) with fine and coarse wood chips were investigated comprehensively under the weather conditions of North-East-Germany over a period of 9 months.The objective of this experiment was to develop a simplified method to calculate dry matter loss by determining the ash content and to compare the results with the conventional sample bag method. The new method delivered statistically sound results, particularly when ash contents were calculated from separated bark and wood samples instead of from wood chip samples. Furthermore, the significant and consistent increase in ash content of the bark samples during storage suggests, that the development of a model solely based on ash content of separated bark could be advantageous in terms of simplified yet reliable determination of dry matter losses. Since the ash content of wood chips is largely governed by the bark content, exact data for the proportion of bark is required, which varies between 18 and 35% depending on tree size represented by the stem diameter at cutting height (SDCH). Moreover, it was found that the fuel quality depends more on the SDCH of the SRC-harvest than on the produced wood chip format.

Investigation of the interrelations between defibration conditions, fiber size and medium-density fiberboard (MDF) properties

Defibration conditions and raw material properties affect wood fiber characteristics, and thereby the properties of fiber-based panels such as high-density fiberboard (HDF), medium-density fiberboard (MDF) and wood fiber insulation board. This study investigates the influence of steaming conditions (time and temperature), grinding disc distance, wood species (pine, beech, birch and poplar), method of refiner discharging (radial and tangential stock outlet) and wood chip size on fiber length and fiber length distribution, and further the influence of fiber size on MDF properties. Fiber lengths were determined applying the recently developed image analysis-based fiber size measuring system FibreCube. This system enables an automated and nearly complete mechanical separation of woolly-felted fiber samples prior to image acquisition, software-supported post-separation of overlapped-lying fibers at the beginning of image analysis, and flow line tracing-based length measurement. It was found that grinding disc distance and wood species are the most influential parameters on fiber length characteristics. Especially the content of undefibrated fiber bundles (shives) was found to strongly correlate with the grinding disc distance. Wood anatomical differences between hardwood and softwood were reflected clearly by the fiber length characteristics. Fiber size was found to be one of the parameters influencing panel properties. However, other fiber characteristics—in particular the chemical nature of the fiber, which is responsible for its wettability with water (thickness swelling) and glue (mechanical properties)—have to be considered as important influencing parameters on panel properties.

Biomass gasification with CO2 in a fluidized bed

Biomass gasification with CO2 as the gasifying agent is a promising way to relieve the energy shortage and minimize CO2 emission. In this study, Eulerian method was used to study the CO2 gasification of biomass in a fluidized bed gasifier. It was found that the CO2 percentage in the gasifying mixture with air, the CO2-to-biomass ratio, the moisture content of woodchips, and the woodchip size had great influence on the gasification performance. With the increasing CO2-to-biomass ratio, the mole fraction of CO in the producer gases would be increased while those of H2 and CO2 vary in the opposite trend. When CO2 mass percentage in the gasifying agent was 60%, the fractions of CO and CH4 in the producer gas reached the maximum, as well as the lower heating value and cold gas efficiency, so this was the optimal condition when the gasifier had the best performance. The moisture content and particle size of the woodchips had negative effects on the gasification performance, because of the lower heating value of producer gases, cold gas efficiency and CO2 conversion ratio were both reduced with increasing moisture content and particle size. This study offers a promising way to integrate the gasification of renewable biomass with CO2 capture, and may be helpful in the design and operation of biomass gasifier.

Preliminary fixed-bed downdraft gasification of birch woodchips

This paper investigated the possibilities of using birch wood chips for fixed-bed downdraft gasification. The preliminary air gasification resulted producer gas with an average composition of 11.5 % CO, 5.4 % CO2, 5.9 % H2, 0.38 % CH4 corresponding to a mean lower heating value of about 2 MJ/kg. The approximate size of woodchips used for gasification was around 11.5 mm for a maximum solid throughput of 0.65 kg/h. The obtained equivalence ratio (ratio between actual air fuel ratio and stoichometric air fuel ratio) as a result of air and biomass feed was close to 0.45 which was stable throughout the test. Producer gas left the gasifier at ca. 150 °C and was diverted for flaring owing to the level of low energy content. Despite availability, the option for gas to generate heat and electricity via integrated gas engine has not been utilized in the present case and remained for further ongoing research.

Hot Water Extraction of Hemicelluloses from Aspen Wood Chips of Different Sizes

Hot water extraction of hemicelluloses from aspen wood chips of different sizes and wood meal was performed, and the extracted hemicelluloses were characterized. With decreasing wood chip size, the total sugars and total poly- and oligosaccharides extracted with hot water increased. The dissolution of hemicelluloses was mainly limited by diffusion in the fiber wall and mass transfer from fiber to fiber during hot water extraction of the wood chips. The extraction yield of high molecular weight hemicelluloses was less than that of low molecular weight hemicelluloses, and the reduction of wood chip size benefited the extraction of high-molecular weight hemicelluloses. Compared to the wood chips, the high molecular weight hemicelluloses extracted from wood meal had a higher extraction yield and an increased average molecular weight.

Determining wood chip size: image analysis and clustering methods

One of the standard methods for the determination of the size distribution of wood chips is the oscillating screen method (EN 15149- 1:2010). Recent literature demonstrated how image analysis could return highly accurate measure of the dimensions defined for each individual particle, and could promote a new method depending on the geometrical shape to determine the chip size in a more accurate way. A sample of wood chips (8 litres) was sieved through horizontally oscillating sieves, using five different screen hole diameters (3.15, 8, 16, 45, 63 mm); the wood chips were sorted in decreasing size classes and the mass of all fractions was used to determine the size distribution of the particles. Since the chip shape and size influence the sieving results, Wang’s theory, which concerns the geometric forms, was considered. A cluster analysis on the shape descriptors (Fourier descriptors) and size descriptors (area, perimeter, Feret diameters, eccentricity) was applied to observe the chips distribution. The UPGMA algorithm was applied on Euclidean distance. The obtained dendrogram shows a group separation according with the original three sieving fractions. A comparison has been made between the traditional sieve and clustering results. This preliminary result shows how the image analysis-based method has a high potential for the characterization of wood chip size distribution and could be further investigated. Moreover, this method could be implemented in an online detection machine for chips size characterization. An improvement of the results is expected by using supervised multivariate methods that utilize known class memberships. The main objective of the future activities will be to shift the analysis from a 2-dimensional method to a 3- dimensional acquisition process.

Determining wood chip size: image analysis and clustering methods

Determining wood chip size: image analysis and clustering methods

Woodchip bedding for sheep in Northern Norway

The aim of this study was to investigate the effects of a woodchip-based deep litter on the health and welfare of sheep. Two different sizes of woodchips (small: 2.5 cm and large: 5.0 cm) were tested in combination, both with or without Sphagnum peat. Ten groups of seven adult, pregnant ewes of the Norwegian White breed were randomly allotted to pens containing one of the bedding mixtures. Resting behaviour, animal cleanliness and the temperature development in the bedding were measured over four months. The woodchip size and peat supplement did not affect resting behaviour, although ewes housed on straw bedding were cleaner than those kept on woodchip-based bedding. The fewer the days since the addition of fresh litter substrate, the cleaner the animals. In conclusion, the welfare of sheep was acceptable when housed on woodchip-based bedding, and generally good when housed on straw bedding.