Research Articles

The influence of moisture content was investigated relative to the pellet forming process and the pellet properties. Three different types of raw biomass (pine sawdust, corn straw, and peanut shell) were pelletized by hot pressing at different moisture levels (12%, 14%, and 16%) in a pellet mill with horizontal and ring type dies to investigate its physical property indexes of durability, pellet density, and combustion performance. The results of the study showed that pellet density and heating value were related to the moisture content. The maximum pellet density of the fuel pellets of sawdust, corn straw, and peanut shells was 1180 kg/m3, 1220 kg/m3, and 1130 kg/m3, respectively. The drop resistance and deformation resistance of pine sawdust and corn straw decreased with increased moisture content, but peanut shell initially increased with the increase of moisture before decreasing. The comprehensive combustion index of corn straw (14.03) was the highest during the combustion performance analysis in comparison to sawdust (11.10) and peanut shell (10.00). Overall, the optimal moisture content of sawdust, corn straw, and peanut shell was 12%, 12%, and 14%, respectively, and the combustion performance of the pellets made from corn straw was superior compared to the other two feedstocks.

Agro-industrial wastes pose great economic and environmental hazards, while the economic success of aquaculture is threatened by the unsustainability of fishmeal use. The aims of the present study were to bio-convert agro-industrial wastes through vermicomposting, and then evaluate the potential of the by-products in promoting aquaculture nutrition. Coffee husks (CH), barley wastes (BW), and kitchen wastes (KW) were pre-composted and inoculated with earthworms, Eisenia fetida, and then vermicomposted for 70 days under a controlled environment. The vermicomposting by-products, i.e., earthworms and vermicast, were amalgamated in the ratio of 1:5 into bedding and then analyzed. There were neither earthworm mortalities nor significant difference (P>0.05) in cocoons produced by E. fetid in all treatments. The earthworms grown in KW attained the highest average weight gain of 27.8±0.7g, followed by CH (24.9±0.6g) and BW (24.8±0.7g). Earthworms grown in CH and BW had significantly higher (P<0.05) nutritional attributes. All experimental wastes produced vermicast with carbon and nitrogen ratios within the preferred agronomic limit of 20. The nutritional profile of the BW bedding was comparable with that of Caridina nilotica meal and was within the recommended dietary requirements of fish. The wastes can be bio-converted through vermicomposting into various forms appropriate for providing aquaculture nutrition.

Large-section boxed-heart square timber is prone to surface and radial cracks during the drying process. A high-temperature setting pretreatment could prevent cracking in boxed-heart timber. The pretreatment process is primarily determined by the preheating time. To determine the preheating time of the test material, a mathematical model for the internal temperature distribution of Mongolian pine (Pinus sylvestris var. mongolica Litv.) boxed-heart square timber in the preheating stage was established by the finite element method. The model viability was verified by tests that showed that the model simulation results were stable and non-fluctuating. For the prediction error of the temperature change, the early-period error was large, while the later predicted values and measured values tended to be consistent. For the prediction error of the temperature distribution, the core-layer error was smallest, while that of the surface layer was greatest. For the prediction error of the preheating time, greater preheating temperatures exhibited greater error, and the minimum error was 10 min, at 90 °C. Overall, the predicted values were close to the measured values and can be referenced for subsequent pretreatment process research.

A novel bentonite-biochar (APB) composite was prepared by incorporating bentonite (BE) with Alternanthera philoxeroides (AP) biochar for the adsorptive removal of Cd(II) from aqueous media. The APB and the pristine biochar (PB) prepared from the AP were produced at 300 °C under a nitrogen environment. The adsorption capabilities of the BE, PB, and APB were tested for the removal of Cd(II) from aqueous solution. The results showed that the pH substantially affected the adsorption of Cd(II) by the PB and APB. The adsorptive capacity of the Cd(II) onto the PB and APB gradually increased as the pH was increased to 6.0, and there was no significant change in adsorption as the pH was further increased to 8.0. The adsorption kinetic data of the PB and APB were fitted to a pseudo-second-order (PSO) adsorption kinetic model and an intraparticle diffusion (ID) model. The Freundlich model matched the experimental data better than the Langmuir model, indicating that the adsorption was heterogeneous. Thermodynamic study revealed that the adsorption was mainly physisorption, and the adsorption process was endothermic and spontaneous, while the orderliness of all adsorption systems decreased. The results demonstrated that the APB was an effective adsorbent for the removal of Cd(II) from aqueous media.

The potential of 32 frequently studied ornamental and/or energy grasses and two cadmium/zinc hyperaccumulators for phytoextraction and phytostabilization was compared by their growth in a historically contaminated soil over a three-month pot experiment. Shoot and root biomasses varied by factors of 14.2 and 62.7, respectively. Mainly due to their large biomass, Napier grass (Pennisetum purpureum ‘Purple’) and variegated giant reed (Arundo donax var. versicolor) accumulated cadmium and zinc contents in shoots up to 109.3% and 55.4% higher, respectively, than those in the cadmium/zinc hyperaccumulators, despite their lower metal concentrations. Pennisetum purpureum ‘Purple’ accumulated the most zinc and the third highest cadmium in roots. Bioconcentration factors of cadmium in roots were greater than 1 for 19 grasses. The present study demonstrated that many of these grasses may be suitable for phytostabilization of soil cadmium. Arundo donax var. versicolor exhibited the most potential for phytoextraction of soil zinc, whereas Pennisetum purpureum ‘Purple’ was best for phytoextraction and phytostabilization of cadmium and phytostabilization of zinc. Ornamental/energy grasses may have greater potentials for soil remediation than hyperaccumulators, especially given their utility and eco-economic benefits. The considerable variation in their performance emphases the value of screening to select the most effective candidates.

Carbon emissions from afforestation and tending operations were studied in this work. Renewable resources from the operations were evaluated in terms of their potential as fuel. New planting operations were found to result in higher energy consumption, biomass, and emissions compared with the tending operations. The greenhouse gas emissions from new planting and afforestation operations for plantation were 405.0 kg CO2/ha, 50.1 g CH4/ha, and 27.1 g N2O/ha, whereas those from the tending operations were 277.7 kg CO2/ha, 36.3 g CH4/ha, and 19.0 g N2O/ha. The major components of the renewable resources from the afforestation and tending operations were C, O, and H, and the contents of N and S were lower than those specified in the regulations by the European Union for refuse-derived fuels. Therefore, the refuse-derived fuel prepared from the renewable resources of the afforestation and tending operations did not cause NOx or SOx pollution. This fuel resulted in zero CO2 emissions, and it could be used as an alternative fuel for small boilers in the future.

A multiple regression model was evaluated to predict pulp and handsheet properties including z-directional tensile strength (z-strength) and Scott bond values. One hypothesis that was central for the model evaluation was that the crill content, as measured with ultraviolet and infrared lights, would improve the statistical models. A chemi-thermomechanical pulp (CTMP) mill designed with two parallel primary refining lines and a reject refiner was the basis for this study, and all process data and pulp samples were gathered from the specific process. Pulp was extracted from the process for an extended period from a position after the latency chest (primary refined pulp) and from the pulp-stream exiting the mill to the board machine (accept pulp). The crill content was positively correlated to the z-strength of the accept pulp, explaining 55% of the variance with a linear regression model with the crill content as the sole predictor. The estimation model of the z-strength of accept pulp was based on a combination of the crill content, freeness, fibril perimeter for longer fibers, and mean kink angle, and resulted in an R2 of 0.79. When applying cross-validation to determine the predictive model performance, the highest R2 obtained was 0.67. This latter model included the crill content, fibril perimeter, and mean kink angle as predictors.

Bamboo nanocellulose can be regarded as a promising biomass material for the preparation of sustainable energy devices due to its unique structure, excellent properties, and wide range of sources. A highly conductive electrochemical energy storage was synthesized due to the excellent electrical conductivity of graphene and the high surface area of nanocellulose and graphene, which was beneficial for producing a network structure. The symmetric capacitor assembled from the Phyllostachys pubescens nanocellulose/graphene aerogel (CGA) electrode exhibited a high specific capacitance of 125.5 F/g at 5 mV/s and extreme stability of 98.3% capacitance retention ratio after 5000 cycles at 2 A/g. This nanocellulose-graphene electrode showed potential for future high-performance supercapacitors.

Steam explosion (SE) was used to pretreat rice straw (RS) and Caragana korshinskii Kom. (CKK). Enzymatic hydrolysis of pretreated RS and CKK, and a pure cellulose (bacterial cellulose, BC) were performed and compared. The characteristics and changes of different substrates during pretreatment and enzymatic hydrolysis were observed. After SE pretreatment, the hemicellulose content of RS and CKK was decreased from 21.7% to 4.9% and 17.9% to 6.2%, respectively. The cellulose percent of RS and CKK was increased to 45.1% and 38.4%, and the enzymatic hydrolysis conversion of cellulose was increased 1.1 times and 0.9 times, respectively. Although the composition and enzymatic yield of different substrates varied, their enzymatic hydrolysis rates showed a similar declining trend during enzymatic hydrolysis. The adsorption capacities of substrates on the enzyme were increased by pretreatment. The enzymatic hydrolysis efficiency was closely related to the enzyme adsorption capacities of substrates at the initial stage (1 h). The BC and SE pretreated RS first adsorbed and subsequently desorbed the enzyme, while the untreated RS and CKK had weak adsorption capacity and formed irreversible adsorption with the enzyme. The changes in crystallinity after enzymatic hydrolysis suggested that there was no direct correlation between the crystallinity and digestibility of cellulose.

An innovative approach for preparing hemp fibers from hemp hurds for use in tissue and towel grades of paper is described. Hemp hurds are a low value by-product of industrial hemp processing that are generally used for animal bed litter. Tissue paper was fabricated from hemp hurd fibers by following three pulping processes: autohydrolysis (hydrothermal), sodium carbonate-based defibration, and high yield kraft pulping, and benchmarked against hardwood pulp. To meet industrial standards, hardwood and hemp pulp fibers were mixed at a dry mass ratio of 75:25, from which tissue paper sheets were prepared. Desirable tissue paper properties, such as water absorption, burst resistance, softness, and tensile strength (dry and wet), were measured and compared. Characterization of morphological and chemical properties of tissue handsheets was conducted with SEM and time-of-flight-secondary ion mass spectrometry (ToF-SIMS). The combined kraft pulped hardwood and autohydrolyzed hemp pulp fibers displayed improvements in tensile index, burst resistance, and softness of tissue handsheets compared to only kraft hardwood pulp handsheets without adversely impacting water absorption. Hardwood fibers showed a sparse distribution of surface lignin compared to hemp fibers using the same defibration. This technology can lead to a variety of eco-friendly tissue paper products that are not only highly energy efficient, but avoid harsh chemical processing.