A lab-scale experiment was conducted to assess effects of the membrane-covered technology and superphosphate on the compost quality and emissions of nitrogen-containing gases during aerobic composting. The results showed that the membrane-covered technology increased the temperature of the compost pile and accelerated degradation of organic matter. The membrane-covered (T1) sample attained a germination index (GI) of 50% and 80%, approximately 2 and 9 d earlier, respectively, relative to the control (CK) sample. However, the application of superphosphate might have an adverse effect on the GI value. The NH3 and N2O emissions during the aerobic composting were decreased by 25.8% and 13.1%, respectively, for the T1 sample compared to the CK sample, while these were reduced correspondingly by 21.3% and 27.2% for the superphosphate addition (T2) sample. Compared with the superphosphate addition, the membrane-covered approach reduced the NH3 emission but not the N2O emission. Thus, the membrane-covered aerobic composting is a potential technology for the adequate utilization of organic waste as a resource.

The addition of biochar and the use of membrane coverings are two methods used in aerobic composting of agricultural waste. The effectiveness of each of these two methods on compost quality and reduction of greenhouse gas emissions was tested in the laboratory. The results showed that both methods increased the maximum composting temperature and extended the thermophilic period. The germination index of biochar-treated compost and membrane-covered compost reached 70% on the 18th day, which was 12 days earlier than the corresponding value in the control group. The products from the biochar-treated compost had higher pH and lower electrical conductivity, compared with the product of the control group, indicating that these products are more suitable for acidic soils. In terms of greenhouse gas reduction, both methods were found to reduce the emissions of CH4 and N2O from composting. The addition of biochar had a better emission reduction effect on N2O, whereas the membrane covering technique yielded a better effect on CH4 emission reduction. The results of this study provide technical support for managed aerobic composting to reduce greenhouse gas emissions.

A comprehensive understanding of the uprooting failure mechanism will likely require the accurate characterization of the mechanical properties of cotton stalk. Uprooting failure includes a fractured cotton stalk and peeled phloem sliding along the xylem. The modulus of elasticity of cotton stalk...

Vegetable waste was aerobically composed using a trough-type system, and the resulting emitted volatile organic compounds were investigated. In addition, the succession pattern of microorganisms was analyzed. Aerobic fermentation was conducted using a tomato stalk-cow dung mix (a water content of 65% and a carbon-to-nitrogen ratio of 25:1). The emitted volatile organic compounds comprised of 58 kinds of compounds, including 2 sulfur-containing compounds, 3 alcohols, 3 esters, 3 aldehydes, 3 ketones, 6 halogenated hydrocarbons, 18 aromatic hydrocarbons, 17 alkanes, and 3 alkenes. The primary volatile organic compounds produced were methyl sulfide, ethyl acetate, ethanol, and acetaldehyde. Clustering and principal coordinate analysis suggested that the community succession changed throughout the composting process in the odor-producing habitat. High-throughput sequencing revealed that the bacterial community was comprised of Firmicutes, Chloroflexi, Proteobacteria, and Actinobacteria, whereas the dominant flora included Ascomycota, Basidiomycota, and Mucoromycota. These findings could aid in the mitigation of volatile organic compounds and odors during vegetable waste composting as well as contribute to the development of deodorizing bacteria.

A horizontal distributor for biogas slurry application was proposed to explore the distribution performance through CFD analysis and verified by field test. The rheological properties of biogas slurry were analyzed at first, and key parameters were obtained for the next simulation. The effects of distribution modes, inlet direction, and outlets number on the velocity distribution of flow field and mass flow rate of the horizonal distributor were investigated by CFD simulations. Results of rheological properties indicated that biogas slurry was a non-Newtonian fluid and exhibited shear-thinning behavior. It can be well described by power-law model. The simulation results showed that the geometry of rotor, especially the block numbers was the main factor that determining the fluid movement and trajectory of distribution and output. The mode rotor 1 with two blocks reached the lowest variable coefficient of mass flow rate (4.49%), indicating a higher degree of uniformity. The upward inlet direction would obtain less dead zone, and the distributor with an even outlets number would possess more uniform distribution and less dead zone. The field test of the distributor with rotor 1, upward inlet direction, and 24 outlets has been carried on to verify the simulation results, the variable coefficient of mass flow was 13.06%, which was slightly higher than the simulation (9.23%), but it still within the range of requirement (<15%). The proposed model and the findings of this work are of guiding significance for the study of the utilization technology and equipment of liquid biogas residue. Keywords: distributor, biogas slurry, distribution uniformity, rheological properties, CFD DOI: 10.25165/j.ijabe.20231601.7460 Citation: Fu J J, Chen Y S, Xu B X, Ma B, Wang P J, W A B, et al. Investigation of distribution uniformity of distributor for biogas slurry application based on CFD analysis. Int J Agric & Biol Eng, 2023; 16(1): 45–52.

Due to the lack of effective numerical simulation and the absence of an accurate and reliable bonded discrete element model for tobacco stalks during mechanised harvesting, the design and optimisation of tobacco stalk pulling and harvesting equipment have been largely hindered. In this study, post-harvest stalks of flue-cured tobacco transplanted in single-ridge cultivation were taken as the research object; Zhongchuan 208 stalk samples with an average outer diameter of 36.78 ± 1.05 mm and an average moisture content of 82.5% were selected, their intrinsic and contact parameters were measured, and a mechanical simulation model of the stalks was established based on the Bonding V2 contact model. With the maximum crushing force (F_C) as the response value, Plackett–Burman tests were first used to screen significant factors, the steepest ascent tests were then employed to determine the optimal region of the significant factors, and finally a second-order regression model between the maximum crushing force and the significant parameters was established using central composite design, yielding the optimal parameter combination: normal stiffness per unit area of 5.498 × 10⁹ N·m⁻³, tangential stiffness per unit area of 1.434 × 10⁹ N·m⁻³, critical tangential stress of 9.146 × 10⁶ Pa, and bonding radius of 1.304 mm. Under this parameter combination, compression and bending simulation tests were carried out; five independent repeated simulations gave an average maximum crushing force of 2410.22 N, a standard deviation of 225.39 N, and a coefficient of variation of 9.35%, with a relative error of 4.32% against the physical test mean; the relative errors of the peak displacement and the maximum bending force were 2.62% and 4.74%, respectively. In the physical control tests with and without epidermis, the relative error between the mean maximum bending forces of the two groups was 8.68%. The results indicate that the discrete element model established in this study can effectively characterise the macroscopic peak load-bearing response of tobacco stalks under the tested conditions and can provide data support for the design and parameter optimisation of stalk pulling equipment.