Aspen Wood Chips Research Articles

Bedding Management for Suppressing Particulate Matter in Cage-Free Hen Houses

Cage-free (CF) layer houses tend to have high particulate matter (PM) levels because of bedding/litter floor and the birds’ activities, such as perching, dustbathing, and foraging on it. It has been reported that optimizing bedding management can potentially suppress PM levels in CF houses. The objectives of this study were to (1) test the effect of the top application of new bedding materials (BMs) on PM levels and (2) compare different BM PM reduction efficiencies. Small flake shavings (SFS), large flake shavings (LFS), and aspen wood chips (AWC) were top-dressed on the surface of the original litter (33-week-old litter) evenly in each of the BM treatment rooms at 20% volume of the original litter floor. The initial litter depths in the control, SFS, LFS, and AWC rooms were 4.6 ± 0.6, 4.8 ± 0.8 cm, 4.8 ± 0.8 cm, and 4.6 ± 0.9 cm, respectively. One room was used as a control without adding new BM. The results indicate that the top application of new bedding suppressed PM levels in all treatment rooms (p < 0.01). The PM2.5 reductions in the SFS, AWC, and LFS treatment rooms were 36.5%, 34.6%, and 28.9% greater than in the control room, respectively. The mitigation efficiencies were different between PM sizes. For instance, PM2.5, PM10, and TSP in the SFS room were lower than in the control room by 36.5%, 39.4%, and 38.7%, respectively. For litter quality, the moisture content was 18.0 ± 2.8, 20.0 ± 3.1, 20.6 ± 2.4, and 19.7 ± 4.2% in the control, SFS, LFS, and AWC rooms, respectively. Treatment rooms with 20% new BM had 10% higher litter moisture than the control room. The findings of this study reveal that the top application of new bedding on old litter is a potential strategy for reducing PM generation in CF houses. Further studies are warranted, such as regarding the effect of different ratios of new bedding on PM reduction, cost analysis, and verification tests in commercial CF houses.

Mycoprotein Production by Submerged Fermentation of the Edible Mushroom Pleurotus ostreatus in a Batch Stirred Tank Bioreactor Using Agro-Industrial Hydrolysate.

The demand for cheap, healthy, and sustainable alternative protein sources has turned research interest into microbial proteins. Mycoproteins prevail due to their quite balanced amino acid profile, low carbon footprint and high sustainability potential. The goal of this research was to investigate the capability of Pleurotus ostreatus to metabolize the main sugars of agro-industrial side streams, such as aspen wood chips hydrolysate, to produce high-value protein with low cost. Our results indicate that P. ostreatus LGAM 1123 could be cultivated both in a C-6 (glucose)- and C-5(xylose)-sugar-containing medium for mycoprotein production. A mixture of glucose and xylose was found to be ideal for biomass production with high protein content and rich amino acid profile. P. ostreatus LGAM 1123 cultivation in a 4 L stirred-tank bioreactor using aspen hydrolysate was achieved with 25.0 ± 3.4 g L-1 biomass production, 1.8 ± 0.4 d-1 specific growth rate and a protein yield of 54.5 ± 0.5% (g/100 g sugars). PCA analysis of the amino acids revealed a strong correlation between the amino acid composition of the protein produced and the ratios of glucose and xylose in the culture medium. The production of high-nutrient mycoprotein by submerged fermentation of the edible fungus P. ostreatus using agro-industrial hydrolysates is a promising bioprocess in the food and feed industry.

Evaluation of Potential Sustainable Bedding Substrates Focusing on Preference, Behavior, and Stress Physiology in Rats—A Pilot Study

Simple SummaryThe use of animals in research is currently a very controversial and emotionally discussed topic; however, to date, animals still play a pivotal and fundamental role in the advancement of biomedical research. Housing conditions of laboratory animals are especially important, as they constitute an overarching factor independent of the respective experiments. In this pilot study, we investigated different types of bedding, i.e., substrates which are used to house laboratory rats. Bedding is a crucial environmental factor for rats as it has a significant influence on their well-being and the animals tend to have a lifelong exposition to a single type of substrate. Our objective for this pilot study was to evaluate corncob and spelt as ecological alternatives to the most commonly used aspen wood chip bedding. Although the rats’ behavior was not changed by different types of bedding substrates, we detected that the rats liked to consume spelt, which could potentially lead to confounding results, when the animals are tested for certain scientific hypotheses. Therefore, this is a crucial factor to consider when planning an experiment that fulfills high-quality scientific outcomes while simultaneously complying with important animal welfare considerations.Ensuring optimal housing conditions for laboratory animals is a crucial prerequisite for high-quality and ethically justifiable in vivo science. In addition to guaranteeing animal welfare and promoting scientific validity, environmental sustainability is also increasingly gaining attention in laboratory animal facilities. Consequently, comprehensive management of such aspects is one of the core tasks of any research vivarium. Hygienic monitoring and adhering to standardized experimental protocols have been highlighted in the past; nevertheless, various environmental aspects of housing animals still need to be evaluated in greater depth. In this pilot study, we aimed at assessing the suitability of spelt and corncob as economical and ecologically friendly bedding substrates as compared with commonly used aspen wood chips. Therefore, following a descriptive study design, we examined the preferences of male and female Wistar rats for corncob and spelt under specific conditions. In addition, we evaluated potential effects on behavior, metabolism, and stress physiology. The type of bedding did not seem to influence behavior in the observed parameters but did have time- and sex-dependent effects on blood glucose. Furthermore, housing animals on spelt led to a significant reduction in food consumption, probably compensated for by the intake of spelt, and although it did not influence glucose levels, it may have certainly impacted the nutrient supply. Our descriptive pilot study, therefore, highlights the importance of a thorough condition-associated evaluation of even seemingly marginal environmental factors, when balancing potential cost-benefit advances in sustainability and questions of standardization and reproducibility of experimental protocols.

Effect of Lignin Modifier on Engineering Performance of Bituminous Binder and Mixture

Lignin accounts for approximately 30% of the weight of herbaceous biomass. Utilizing lignin in asphalt pavement industry could enhance the performance of pavement while balancing the construction cost. This study aims to evaluate the feasibility of utilizing lignin as a bitumen performance improver. For this purpose, lignin derived from aspen wood chips (labeled as KL) and corn stalk residues (labeled as CL) were selected to prepare the lignin modified bituminous binder. The properties of the lignin modified binder were investigated through rheological, mechanical and chemical tests. The multiple stress creep recovery (MSCR) test results indicated that adding lignin decreased the Jnr of based binder by a range of 8% to 23% depending on the stress and lignin type. Lignin showed a positive effect on the low temperature performance of asphalt binder, because at −18 °C, KL and CL were able to reduce the stiffness of base binder from 441 MPa to 369 MPa and 378 MPa, respectively. However, lignin was found to deteriorate the fatigue life and workability of base binder up to 30% and 126%. With bituminous mixture, application of lignin modifiers improved the Marshall Stability and moisture resistance of base mixture up to 21% and 13%, respectively. Although, adding lignin modifiers decreased the molecular weight of asphalt binder according to the gel permeation chromatography (GPC) test results. The Fourier-transform infrared spectroscopy (FTIR) test results did not report detectable changes in functional group of based binder.

Enhancing Enzyme-Mediated Cellulose Hydrolysis by Incorporating Acid Groups Onto the Lignin During Biomass Pretreatment.

Lignin is known to limit the enzyme-mediated hydrolysis of biomass by both restricting substrate swelling and binding to the enzymes. Pretreated mechanical pulp (MP) made from Aspen wood chips was incubated with either 16% sodium sulfite or 32% sodium percarbonate to incorporate similar amounts of sulfonic and carboxylic acid groups onto the lignin (60 mmol/kg substrate) present in the pulp without resulting in significant delignification. When Simon’s stain was used to assess potential enzyme accessibility to the cellulose, it was apparent that both post-treatments enhanced accessibility and cellulose hydrolysis. To further elucidate how acid group addition might influence potential enzyme binding to lignin, Protease Treated Lignin (PTL) was isolated from the original and modified mechanical pulps and added to a cellulose rich, delignified Kraft pulp. As anticipated, the PTLs from both the oxidized and sulfonated substrates proved less inhibitory and adsorbed less enzymes than did the PTL derived from the original pulp. Subsequent analyses indicated that both the sulfonated and oxidized lignin samples contained less phenolic hydroxyl groups, resulting in enhanced hydrophilicity and a more negative charge which decreased the non-productive binding of the cellulase enzymes to the lignin.

Electrochemical behavior of biochar and its effects on microbial nitrate reduction: Role of extracellular polymeric substances in extracellular electron transfer

Biochar is extensively used in the remediation of pollutants because of its diverse physicochemical properties. Biochar application can alter the activity of microbial communities involved in bioremediation. However, the electrochemical behavior of biochar and its potential effect on microbial nitrate reduction remains unknown. Electron transfer between microbial cells and electron donor or acceptor species is often across extracellular polymeric substances (EPS). However, the role of EPS in extracellular electron transfer remains unclear. In this study, we examined the electrochemical behavior of biochar and its effects on microbial nitrate reduction to elucidate the role of EPS in extracellular electron transfer (EET). The biochar prepared by the pyrolysis of Aspen wood chips at 400–600 °C. Electrochemical analysis using cyclic voltammetry, electrochemical impedance spectrum, and chronoamperometry showed that biochars could donate and accept electrons. BC 400, BC 500, and BC 600 had an electron donating capacity of 1.03 mmol e− g−1, 0.9 mmol e− g−1, and 0.8 mmol e− g−1, respectively. Furthermore, biochars prepared at 400 °C significantly enhanced the microbial nitrate reduction process. The phenol OH and quinone CO surface functional groups on the biochar probably contributed to the overall electron exchange, and this accelerated the nitrate reduction. Electrochemical analysis revealed that the outer membrane c-type cytochrome and flavin proteins from the biofilm were involved in the electron transfer process, with the EPS acting as a transient media for the microbially-mediated EET. Overall, this study suggested that biochar may be effectively used as an eco-friendly material for the enhancement of microbial denitrification.

A Techno-Economic Assessment of Renewable Diesel and Gasoline Production from Aspen Hardwood

In this study, we developed a techno-economic model to estimate the production cost of renewable diesel and gasoline from aspen woodchips through fast pyrolysis-based bio-oil and its subsequent hydroprocessing. The whole pathway includes the conversion of woodchip biomass to bio-oil through fast pyrolysis followed by upgrading to transportation fuels via hydroprocessing. Experiments were carried out to develop for the process model. This detailed process and techno-economic study was done based on 2000 dry t day−1 aspen woodchips (base case capacity), from which we estimated the cost to produce renewable diesel and gasoline. For this base case, using the present method, 148.81 ML year−1 of renewable diesel and 99.21 ML year−1 of gasoline using merchant hydrogen can be produced. The production costs of renewable diesel and gasoline for 2000 t day−1 are 1.09 and 1.04$ L−1, respectively. We also studied the effect of changing the scale of the facility from 500 to 5000 t day−1 on the production costs of renewable diesel and gasoline. The economic optimum plant size (the capacity at which fuel production cost is lowest) was determined to be 3000 t day−1. Finally, we carried out sensitivity and uncertainty analyses for the base case and determined that production cost is most sensitive to bio-oil yield and internal rate of return (IRR).

Interactive effects of climate change and fungal communities on wood-derived carbon in forest soils

Although wood makes up the majority of forest biomass, the importance of wood contributions to stable soil carbon (C) pools is uncertain. Complex interactions among climate, soil physical properties, intrinsic properties of woody residues, and biological processes all exert dynamic controls over the stabilization, destabilization and transport of wood-derived C in soils. Many studies have demonstrated the strong physical controls on decomposition rates in soils, but little work has been done to relate these to changes in decomposer community composition and how this influences the fate of wood-derived C in soils. Here, we examine the effects of initial fungal inoculation, temperature, soil texture, Free Air CO2 Enrichment (FACE) wood type, and location of wood residue in the soil, with an experiment investigating the fate of wood-derived C from soils in the first two years following clear-cut harvest in aspen (Populus tremuloides Michx.) forests. We applied 13C-depleted aspen wood chips in 168 experimental plots across six sites in northern Michigan, USA, and tracked the depleted 13C signature through the mineral soil as DOC and from the soil surface as CO2.Wood residue location had the largest impact on soil CO2 efflux, with surface wood treatments having more than twice as much wood-derived soil CO2 efflux as buried wood treatments (1.20 g CO2 m−2 h−1 versus 0.49 g CO2 m−2 h−1, respectively; p < 0.001). Initial fungal decomposers had a significant effect on DOC quantity and quality, with higher wood-derived DOC concentrations, levels of humification, and tannin content for white-rot treatments compared with brown-rot treatments. Buried chip treatments within open-top chambers had one-third higher wood-derived soil CO2 efflux than buried chips in ambient temperature treatments (p < 0.002). FACE wood type also influenced soil C fluxes from the decomposing wood chips. The average wood-derived soil CO2 efflux and the average percentage of wood-derived soil CO2 efflux were significantly greater from wood grown under elevated CO2 than wood grown under elevated CO2 + O3 (p = 0.002 and p = 0.004, respectively). Furthermore, wood grown under elevated CO2 had increased DOC aromaticity relative to wood grown in ambient conditions. Taken together, these results show that wood-derived C sources and the decomposers that process them are significant determinants of C fluxes from and transformations within the soil following harvest in aspen forests.

Recycling of pre-hydrolysis liquor to improve the concentrations of hemicellulosic saccharides during water pre-hydrolysis of aspen woodchips

In this study, the pre-hydrolysis liquor (PHL) was recycled during aspen chip water pre-hydrolysis, and the effects of PHL recycling on the extraction and accumulation of the hemicellulosic saccharides especially that with high molecular weight in the PHL were studied. The results showed that the concentration of hemicellulose saccharides in PHL depended on the pre-hydrolysis temperature and PHL recycling times. Compared to the unrecycled PHL, the concentration of hemicellulosic saccharides in PHL increased significantly when recycling PHL once or twice at 170°C. Furthermore, the amount of high-molecular-weight hemicelluloses (HMHs) in PHL recycled once at 170°C increased from 2.58g/L (unrecycled) to 6.18g/L, but the corresponding average molecular weight of HMHs decreased from 9.2kDa to 7.6kDa. The concentration of hemicellulosic saccharides in PHL decreased with PHL recycling time at 180°C, accompanied by the formation of a significant amount of furfural.

The influence of polymer adsorption, and fiber composition, on the rheology of aqueous suspensions of aspen, cotton, and corn stover pulps

The mechanisms governing the ability of water-soluble polymers (WSP) to alter the rheological properties of lignocellulosic biomass to achieve processing advantages are investigated. Lignocellulosic fiber surface chemistry is found to be an important factor in the efficacy of WSPs as rheological modifiers, and a strong correlation between the amount of adsorbed polymer at fiber surfaces and the yield stress of the fiber suspension indicate that adsorption of polymer is important for rheological modification. Three fiber suspensions of varying physical chemistry were produced from Aspen wood chips, and a number of additional fiber suspensions with chemically functionalized surfaces were generated from cellulose pulp. Polymer adsorption and suspension rheology are found to correlate in every case examined, but the amount of adsorbed polymer alone cannot be used to predict the efficacy of a WSP as a rheological modifier, suggesting that there are contributions from additional variables such as adsorbed-polymer conformation.

Hot Water Pretreatment of Boreal Aspen Woodchips in a Pilot Scale Digester

Hot water extraction of aspen woodchips was treated at about 160 °C for 2 h with a liquor-to-solid ratio of 4.76:1 in a 1.84 m3 batch reactor with external liquor circulation. Both five-carbon and six-carbon sugars are obtained in the extraction liquor. Xylose and xylooligomers are the main five-carbon sugar in the hot water extract, which reached a maximum concentration of 0.016 mol/L, and 0.018 mol/L, respectively. Minor monosaccharides including galactose, mannose, rhamnose, glucose, and arabinose are also obtained during the hot water extraction. Rhamnose is the main six-carbon sugar in the extraction liquor, which has a maximum concentration of 0.0042 mol/L. The variations of acetyl groups and formic acid are investigated due to their catalytic effect on the extraction reactions. Zeroth-order kinetics models are found to be adequate in describing the dissolved solids, acids, xylose, and xylooligomers.

Pyrolysis of wood to biochar: Increasing yield while maintaining microporosity

The objective of this study was to determine if biochar yield could be increased by the deposition of volatile pyrolysis species within the bed during production, without negatively influencing the microporosity and adsorption properties. Aspen (Populus tremuloides) wood chips were loaded into three vertically stacked zones within a reactor and heated in nitrogen to temperatures between 420 and 650°C (i.e., pyrolyzed). The yield did increase from the zone at the reactor inlet to the subsequent zones as volatile species deposited and carbonized, and importantly, the carbonized deposits had a similar microporous structure and organic vapor uptake (1,1,1,2-tetrafluoroethane) to that of the primary biochar. Based on these results, bio-oil from previous runs at 600°C was recycled to the bed, which further increased the yield while maintaining the desirable adsorption properties of the biochar.

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.

Quantitative predictions of bioconversion of aspen by dilute acid and SPORL pretreatments using a unified combined hydrolysis factor (CHF)

A combined hydrolysis factor (CHF) was developed to predict xylan hydrolysis during pretreatments of native aspen (Populus tremuloides) wood chips. A natural extension of previously developed kinetic models allowed us to account for the effect of catalysts by dilute acid and two sulfite pretreatments at different pH values. When xylan is modeled as two fractions with different hydrolysis rates, previously identified as fast and slow xylan, the model closely matches the experimental data. Extent of xylan hydrolysis is strongly correlated with pretreatment solids yield, energy consumption for size reduction, and substrate enzymatic digestibility (SED). Composition of the pretreatment hydrolysate was less correlated with extent of hydrolysis due to carbohydrate decomposition reactions. Substrate cellulose enzymatic conversion and enzymatic hydrolysis glucose yield can be predicted to approximately 10% accuracy using CHF alone.

Hot-water extraction and its effect on soda pulping of aspen woodchips

Abstract Hot-water extraction of industrial aspen woodchips (mainly Populus tremuloides) and subsequent soda pulping were carried out in an M/K® digester. It was found that mass removal of woodchips was 4.74% at 160 °C for 15 min with a water-to-wood ratio of 4:1, and that mass removal increased with extraction time and temperature. The mass removal reached 21.38% at 160 °C for 210 min. Less than 6% lignin (on total wood mass) from virgin woodchips was dissolved in the extraction liquor. The concentrations of xylose, acetic acid, formic acid and furfural in the extraction liquor were measured by 1H NMR, which were found to increase with extraction time and temperature. Furfural increased sharply beyond 150 min of extraction at 160 °C. The residual woodchips were subjected to soda pulping at 150 °C for 3 h with 20% effective alkali and a liquor-to-wood ratio of 4.5:1. Compared with the control sample, the overall pulp yield for extracted woodchips decreased little while rejects decreased sharply. Kappa number of the pulps decreased with increasing extraction time and temperature. Viscosity of the pulp increased with increasing extraction temperature and duration for the first 90 min. Beyond 90 min of extraction, the resulting pulp viscosity decreased with increasing duration of extraction. The water-to-wood ratio had little effect on the entire process. Considering bioconversion of extracted hemicellulose to fuel/chemicals and the resultant pulping characteristics, hot-water extraction at 165 °C for 90 min with a water-to-water ratio of 5:1 for aspen woodchips seems to be optimum.

Pre-extraction of hemicelluloses and subsequent ASA and ASAM pulping: Comparison of autohydrolysis and alkaline extraction

AbstractCommercial aspen wood chips were treated with hot water (autohydrolysis) and with alkali to extract part of the hemicelluloses. The extracted residues and an unextracted wood (control) were subjected to pulping based on the alkaline sulfite anthraquinone (ASA) and alkaline sulfite anthraquinone methanol (ASAM) methods to afford pulps useful for paper production with the same degree of delignification. Unlike the autohydrolysis residue, the alkali extracted residue was shown to favor subsequent pulping in terms of pulping yield, charges of chemicals, cooking times and properties of pulps. The experimental conditions and results are discussed.

Modeling xylan solubilization during autohydrolysis of sugar maple and aspen wood chips: Reaction kinetics and mass transfer

A mathematical description is presented for xylan solubilization during hydrothermal pretreatment of sugar maple and aspen wood chips. It assumes first-order kinetics with Arrhenius-type temperature dependence of the reaction rate constants and includes limitations on the transport of reaction products formed in the wood pores to the bulk liquor. The model is calibrated with experimentally measured yields of residual xylan, xylooligomers, and xylose obtained in the autohydrolysis of sugar maple wood chips under pretreatment conditions of 152−175 °C, reaction times of 0−6 h, and liquor to solid ratio of 6:1 in a batch digester. It is validated against experimental data obtained from the autohydrolysis of aspen wood chips at 160 °C under similar experimental conditions as those used for sugar maple. The model can also satisfactorily correlate data of deacetylation of xylan and formation of products (free acetyl groups and acetyl groups attached to xylooligomers in the hydrolyzate) in the autohydrolysis of sugar maple and aspen wood chips with fair accuracy.

Long-term effects of cage-cleaning frequency and bedding type on laboratory rat health, welfare, and handleability: a cross-laboratory study

Cage-cleaning is necessary for a hygienic environment, but since rats communicate using scent, they might suffer if their cages are cleaned too frequently. Male rats (Sprague-Dawley and Wistar) were kept for five months across four animal units. Their cages were cleaned twice-weekly, weekly, or every two weeks, and contained either aspen woodchips or absorbent paper bedding. Aggression, injuries and general health, weight gain, chromodacryorrhoea (a stress-related Harderian gland secretion), handleability, and lung pathology were monitored, as was in-cage ammonia. Cleaning frequency had no clear impact on rat welfare, although frequent cleaning decreased ammonia concentrations and handleability, and non-aggressive skirmishing was highest in weekly cleaned rats. Surprisingly, bedding type did not affect ammonia, but all ammonia readings were unexpectedly low. However, rats kept on aspen had greater sneezing rates and lung pathology than those on paper bedding, but also had higher body weights. The results raise concerns about aspen bedding, which is relatively inert compared with other wood beddings, but nevertheless more harmful than paper. Animal unit significantly affected eight of the 11 variables tested, having interactive effects on five of them. The study also demonstrates the interactive effects of different animal units, casting doubt on the feasibility of standardization. We explored multiple variables of interest, so all findings require confirmation through further work. Nevertheless, cage-cleaning rates seem to affect socially housed male rats little, while bedding type has important effects on rat health.

The effect of moisture on the dynamical mechanical properties of bacterial cellulose/glucuronoxylan nanocomposites

The plant cell wall possesses unique material properties due to its hierarchical organisation. In order to biomimic a native structure like a plant cell wall, a model system consisting of microfibrillar cellulose, produced by the gram-negative bacteria Acetobacter xylinum, and a glucuronoxylan matrix derived from aspen holocellulose was constructed. The glucuronoxylan was extracted from delignified aspen ( Populus tremula) wood chips using DMSO to preserve its native chemical composition. Dynamic mechanical analysis (DMA) measurements performed with moisture scans showed a moisture-induced softening of delignified aspen wood fibres due to the plasticization of glucuronoxylan. A similar result was observed for the model system. However, the softening behaviour of the delignified aspen fibre and the model system was not identical, most probably due to differences in spatial organisation of the components. Dynamic FTIR-studies indicated that interactions between the cellulose and the glucuronoxylan exist in the aspen holocellulose while the components in the nanocomposite appear to be more isolated.

Absorbencies of six different rodent beddings: commercially advertised absorbencies are potentially misleading

Moisture absorbency is one of the most important characteristics of rodent beddings for controlling bacterial growth and ammonia production. However, bedding manufacturers rarely provide information on the absorbencies of available materials, and even when they do, absorption values are usually expressed per unit mass of bedding. Since beddings are usually placed into cages to reach a required depth rather than a particular mass, their volumetric absorbencies are far more relevant. This study therefore compared the saline absorbencies of sawdust, aspen woodchips, two virgin loose pulp beddings (Alpha-Dri and Omega-Dri), reclaimed wood pulp (Tek-Fresh), and corncob, calculated both by volume and by mass. Absorbency per unit volume correlated positively with bedding density, while absorbency per unit mass correlated negatively. Therefore, the relative absorbencies of the beddings were almost completely reversed depending on how absorbency was calculated. By volume, corncob was the most absorbent bedding, absorbing about twice as much saline as Tek-Fresh, the least absorbent bedding. Conversely, when calculated by mass, Tek-Fresh appeared to absorb almost three times as much saline as the corncob. Thus, in practical terms the most absorbent bedding here was corncob, followed by the loose pulp beddings; and this is generally supported by their relatively low ammonia production as seen in previous studies. Many factors other than absorbency determine whether a material is suitable as a rodent bedding, and they are briefly mentioned here. However, manufacturers should provide details of bedding absorbencies in terms of volume, in order to help predict the relative absorbencies of the beddings in practical situations.