Initial Moisture Content Research Articles

Drying Vanilla Using A Hybrid Dryer

Vanilla (Vanilla planifolia Andrew) is a plant that has high economic value; the plant is oriented for export. Postharvest handling is necessary to produce good quality vanilla; One of them is the drying process. This study aims to measure the drying time of vanilla, measure the decrease in moisture content, and analyze the efficiency of drying wet vanilla using a rack-type hybrid dryer. The research was conducted with three treatments, namely: drying using solar energy, drying using electrical energy, and drying using solar energy and electrical energy (hybrid). Based on the results of the study, it was found that drying using solar energy, drying using electrical energy, and drying using solar energy and electrical energy (hybrid) took 15 days, 17 days, and 13 days, respectively. The initial moisture content of drying is about 91.25% which decreases to about 32.44% at the end of drying. The efficiency of the three treatments was 6.39%, 1.58%, and 0.92%, respectively. Keywords: Drying, Hybrid postharvest, Vanilla

Examination of the fire performance of wood materials treated with different precautions

This paper aims to discover how organic wood preservatives containing different fungicides and insecticides used to protect wood against fungal and insect pests affect the fire performance and combustion properties of wood materials commonly used in the domestic wood and construction industry. The aim of this article was to investigate the charring depth. From the point of view of the loss of load-bearing capacity of the wood, only the charring depth matters, since the reduction of the load-bearing capacity will be determined by the reduction of the cross section of the wood. We examined the effects of wood preservatives applied to undamaged samples of Scots pine and Norway spruce conditioned under normal climate conditions. The test samples underwent a second treatment application after which we examined the effect of different preservative combinations. Seven treatment mixtures were selected from the organic solvent and water-based wood preservatives available on the domestic market. The soaking experiments demonstrated that the preservative impregnation of Norway spruce differs significantly from that of Scots pine, which affected the comparability of the test results. We have experimentally investigated the moisture content, the loss of mass and we have calculated the char depth. Adhering to the MSZ 9607–1:1983 standard, the Linder method was performed to analyze the wood and wooden-based construction products used in construction. The effect of the different treatment materials was more significantly detectable when analyzing the size of the surface burn patterns. The Scots pine specimens suffered much greater surface burn than the Norway spruce specimens did, regardless of the type of preservative used. The higher body density, resin content (1–10%) and higher initial moisture content of Scots pine caused it to bend and, therefore, to burn better.

Effects of Mellowing Practice on the Strength and Swelling Properties of Road Construction Materials: Case of Sulphate-Bearing Clay Soils Stabilised with Lime-Silica Fume Blended Binder

The main thrust of this research was to establish any benefits of mellowing, and the optimal moisture content (OMC) for compacting mellowed sulphate-bearing clay soil undergoing the stabilization process. Two three-day mellowing regimes were carried out, prior to final compaction, at different initial moisture contents of 30% or 40% OMC. The unmellowed specimens were compacted immediately after mixing with the blended stabilizers. A blend of quicklime (L) with a sustainable by-product, silica fume (SF), at a 1:1 ratio (2%L-2%SF) was used. Linear expansion and unconfined compressive strength (UCS) tests were carried out to evaluate the benefits of mellowing. The test results suggested that the mellowed test specimens achieved better UCS and swelling properties compared to the unmellowed specimens. Mellowing at 1.2 OMC produced better strength performance than at 1.4 OMC, whereas mellowed specimens at 1.4 OMC showed better resistance to linear expansion compared to 1.2 OMC. The research findings suggested that optimal performance was achieved by mellowing at the higher initial moisture condition of 40% OMC and compacting the materials at the lower moisture condition of 1.2 OMC.

Airborne power ultrasound for paper drying: an experimental study

A novel approach for paper drying using airborne ultrasound technology is presented. A unique experimental setup is developed, and a systematic study is conducted using 23 factorial design of experiments and Analysis of Variance. Three controlling factors are considered in the experiments including the initial moisture content, basis weight and refining condition. The outcome of the experiments is compared to a previous work on direct-contact ultrasonic drying of paper. The results confirm that similar to direct-contact, for airborne ultrasonic drying, the basis weight/thickness of the sample is the most important factor in ultrasonic drying and it is followed by the effect of initial moisture content. Using linear regression model, a correlation for predicting the total time of ultrasonic drying is provided. Quality of the dried samples is evaluated, and the permeability measurements confirmed the effect of pore characteristics on ultrasonic drying. The analysis for energy consumption reveals that airborne ultrasonic drying is more efficient at higher moisture contents.

Airtightness of a Critical Joint in a Timber-Based Building Affected by the Seasonal Climate Change

The airtightness of buildings is an essential topic regarding energy preservation. The development of new and more sophisticated materials and technology approaches is inevitable. Uncontrolled infiltration is undesirable in buildings with lower energy demands with regulated ventilation. Envelope structure, building method, quality, and others are the main factors influencing the airtightness of the building. However, the correlation between airtightness and climatic factors is less known and researched. This paper comprises measurements of a critical timber-house corner in climatic chambers. It captures the correlation between airtightness and gradual temperature and relative humidity adjustments, simulated from the exterior side. The initial timber moisture content was 12%, and during the experiment it increased with the exterior conditions to 18%. Afterward, we simulated conditions causing a humidity decrease while measuring airtightness. The drying process caused a decrement in airtightness by 18%. In addition to this experiment, this paper also analyses two methods of an airtight membrane connection—constricting or taping the contact. The discrepancy between those two methods was more than 21% in favor of tape.

Mineralogical and Microstructural Characterization of Cement-Stabilized Soft Soils Based on Quantitative Analyses

The effects of cement dosage (percentage by dry soil weight) and initial moisture content (wo) on cement stabilized soft estuarine clay were investigated by effective integration of multi-quantitative analyses, including quantitative X-ray diffraction (XRD), thermalgravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) test and scanning electron microscopy (SEM) with image processing. These quantitative analyses are highly complementary, which greatly improved the scientificalness of this research. The results revealed that the strength development of cement stabilized soft estuarine clay with varying cement dosages, and initial moisture content was ascribed to the combined influence of both soil fabric improvement and cementation bonding enhancement. The increase of wo resulted in larger clay particle spaces, which can counteract the enhancement of soil structure due to the rising hydration products. The hydration degrees of samples with fixed cement dosage but different wo are quite similar, while clay particle spaces were enlarged with an increase of initial moisture content. Thus, the same quantity of hydration products may bind more soil particles when pores are small at lower wo, thus increasing unconfined compressive strength (UCS). Furthermore, BET and quantitative SEM results illustrate that hydration degree plays a dominant role in the development of intra-aggregate pores (<0.2 μm), while wo affects inter-aggregate pores (0.2 μm–2 μm) more.

Lignocellulolytic enzyme cocktail produced by plant endophytic Chaetomium globosum exhibits a capacity for high-efficient saccharification of raw rice straw

The aim of this work was to optimize the production of lignocellulolytic enzyme cocktail by a plant endophyte Chaetomium globosum DX-THS3 under solid-state fermentation, and to evaluate the saccharification efficiency of this enzyme cocktail on raw rice straw. The process variables, including substrate type, substrate size, initial moisture content of substrate, culture temperature and fermentative time, were optimized using One-factor at a time approach and Response surface methodology. The results showed that the maximum CMCase, FPase and xylanase production reached 237.04 U/g, 54.8 U/g, and 987.33 U/g, respectively. Meanwhile, the lignocellulolytic enzyme cocktail exhibited good thermal stability between 30 °C and 60 °C, and excellent tolerance to acidic pH values of 3–6. Subsequently, the saccharification of raw rice straw by the enzyme cocktail was performed. After 24 h hydrolysis of raw rice straw, high reducing sugars yield (294.36 mg/g) and hydrolytic rate (47.58 %) were achieved. Furthermore, scanning electron micrograph also indicated that the enzyme cocktail had high hydrolysis performance for raw rice straw. Overall, our result provides a novel class of lignocellulolytic enzyme cocktail with a capacity for high-efficient and eco-friendly saccharification of raw rice straw, and strongly suggests plant endophytic fungi as excellent candidates for the production of lignocellulolytic enzymes.

Development of a hybrid mixed-mode solar dryer for product drying

Sun drying in the open air is quite popular worldwide. However, the use of solar dryers to preserve various perishable agricultural products is a relatively new area of study, and the long-term effects of this method are not yet fully understood. The slow drying process in direct sunlight can contaminate the dried materials by soil and insects. To overcome these challenges, we devised a sun drying system that included a heating part, a drying area, a portable stand, fans, and a 50-W photovoltaic panel. An alternate energy source was used to power the drying process during cloudy days and at night. Fresh Freestone peach, Golden apple, and Anaheim chilies weighing 10 kg each with the initial moisture content of 89%, 87%, and 75% on a wet basis (w.b), respectively, were used in the experiments. The final moisture content of the samples was reduced by an average of 16%, 15%, and 11% for Freestone peaches, Golden apples, and Anaheim chilies, respectively. The quality analysis was carried out to determine sample composition, total bacteria, and color of dried products. The results indicated that the dried products met the recommended quality standards for food products in terms of composition, total bacteria, and color. This research supports the use of a hybrid mixed-mode solar dryer for drying a wide range of perishable agricultural products.

Indoor Experiments on the Moisture Dynamic Response to Wind Velocity for Fuelbeds with Different Degrees of Compactness

The semiphysical method is presently the most widely used for predicting litter moisture content, but it produces some errors. These are mainly due to the simplification of the water loss process and not accounting for the fuelbed structure, which can have a serious impact on the accuracy of litter moisture content predictions and, consequently, on forest fire management. As such, in this study, we constructed fuelbeds with different degrees of compactness, and the moisture content is saturated at this time. The drying process is recorded every 10 min under different wind velocity, and the experiment is stopped when the moisture content is not changing. Taking the saturated fibers’ moisture content (30%) as the threshold value, the drying process was artificially divided into two stages (from the initial moisture content to 30%, it is a process of free water drying, and from 30% to the equilibrium moisture content, this is the process of drying of bound water), which is called the distinguishing drying process. The whole drying process (from the initial to the equilibrium moisture content) is called the undistinguishing drying process. Drying coefficient and effect factors were calculated by distinguishing and not distinguishing the drying process, respectively. This established a prediction model based on compactness and wind velocity. The results show that the drying coefficients, k2 and k, of the two litter types were significantly different: the k2 of the white oak fuelbed was significantly lower than its k, with a maximum variation difference of 57.10%. The k2 in the Masson pine fuelbed was significantly higher than its k, with a maximum variation difference of 72.76%. Wind velocity and compactness had significant effects on all the drying coefficients of the two litter types, but with changes in the effect factors. The changes in k2 were weaker than those of the other drying coefficients. Compared with the model that did not distinguish the drying process, the MRE of the prediction models for white oak and Masson pine decreased by 27.39% and 2.35%, respectively. The prediction accuracy of the model of the drying coefficient obtained by distinguishing the drying loss process was higher than that of the model that did not distinguish the drying process. This study was an indoor simulation experiment that elucidated the drying mechanism of litter and established a prediction model for the drying coefficient based on effect factors. It is of great significance for further field verification and for improving the accuracy of moisture content predictions based on the semiphysical method and will significantly improve the accuracy of fire risk and fire behavior prediction.

Experimental investigation of drying neem (Azadirachta indica) in an evacuated tube solar dryer: Performance, drying kinetics and characterization

In this experimental study, the performance of an evacuated U-tube solar collector (ETSC) combined with an indirect solar dryer is investigated, and the obtained results are compared with conventional open sun drying (OSD) to determine the optimal method for drying neem leaves. The ETSC dryer reduces the initial moisture content from 68.1% (db) to 8.34% (db) in 7 h, whereas it takes 13 h in the OSD. The average efficiencies of the collector and dryer are 61.22% and 29%, respectively. Furthermore, eleven different mathematical models are compared with non-linear regression analysis for describing the drying behavior of neem leaves. Among all examined models, the one suggested byVerma et al., is found to be the most suitable fit for the drying kinetics of the neem leaves in an ETSC dryer with the coefficient of determination (R2) value of 0.9994, root mean square error (RMSE) of 0.01002, and chi-squared error (χ2) of 0.0001673; the Modified Henderson and Pabis model gives the best correlation in the OSD with the R2°value of 0.9984, RMSE value of 0.0153, and χ2of 0.000237. Further, quality analysis of the dried leaves is carried out; the highest value of color change in the dried samples is found in the OSD, and Total phenolic content (TPC) values are found to be more in the leaves dried by the ETSC. The images obtained from the scanning electron microscope (SEM) reveal that the OSD samples contain more pores in their microstructure comparedto ETSC-dried samples. The X-Ray diffraction (XRD)analysis indicates that ETSC-dried neem leaves have a longer shelf life. The Fourier-transform infrared spectroscopy (FTIR)analysis shows thepresence of amino acids and phenolic content in the driedneem samples, making its suitability for use inthe production of drugs by pharmaceutical industries.

Studi eksperimen rumah pengering ultra-violet (solar dryer) sistem hibrid tungku biomassa melalui variasi kecepatan aliran udara panas

The ultra-violet dryer integrated with the biomass furnace is a drying method with a forced mechanism. In this study, an experimental study was carried out. The drying process of porang tubers uses a hybrid system ultra violet plastic dryer (UV solar dryer) through varying the speed of the inlet air to obtain efficient drying results and porang tuber products. The results showed that the final moisture content of porang tubers after drying per day for each variation of air speed obtained the lowest value of 10.50%bb with the highest drying rate of 0.3373 kg/hour from the assumption of an initial moisture content of 70%bb, which occurs in variations airspeed of 1.8 m/s. while the speed is 1.3 m/s with the lowest drying rate of 0.330 kg/hour with a final moisture content of 11.74%.bb) Drying efficiency for variations in the speed of hot air flow into the hot air duct of the biomass furnace shows the highest value at a speed of 1.3 m/s of 16.76% with the lowest specific energy consumption (KES) of 51975.7 kJ/kg.

Optimization of composting methods for efficient use of cassava waste, using microbial degradation.

With the recent revolution in the green economy, agricultural solid waste resource utilization has become an important project. A small-scale laboratory orthogonal experiment was set up to investigate the effects of C/N ratio, initial moisture content and fill ratio (vcassava residue:vgravel) on the maturity of cassava residue compost by adding Bacillus subtilis and Azotobacter chroococcum. The highest temperature in the thermophilic phase of the low C/N ratio treatment is significantly lower than the medium and high C/N ratios. The C/N ratio and moisture content have a significant impact on the results of cassava residue composting, while the filling ratio only has a significant impact on the pH value and phosphorus content. Based on comprehensive analysis, the recommended process parameters for pure cassava residue composting are a C/N ratio of 25, an initial moisture content of 60%, and a filling ratio of 5. Under these conditions, the high-temperature conditions can be reached and maintained quickly, the organic matter has been degraded by 36.1%, the pH value has dropped to 7.36, the E4/E6 ratio is 1.61, the conductivity value has dropped to 2.52 mS/cm, and the final germination index increased to 88%. The thermogravimetry, scanning electron microscope, and energy spectrum analysis also showed that the cassava residue was effectively biodegraded. Cassava residue composting with this process parameter has great reference significance for the actual production and application of agriculture.

Multilayer perceptron-genetic algorithm as a promising tool for modeling cultivation substrate of Auricularia cornea Native to Iran.

Auricularia cornea Ehrenb (syn. A. polytricha) is a wood-decaying fungi known as black ear mushroom. Earlike gelatinous fruiting body distinguishes them from other fungi. Industrial wastes have the potential to be used as the basic substrate to produce mushrooms. Therefore, 16 substrate formulations were prepared from different ratios of beech (BS) and hornbeam sawdust (HS) supplemented with wheat (WB) and rice brans (RB). The pH and initial moisture content of substrate mixtures were adjusted to 6.5 and 70%, respectively. The comparison of in vitro growth characteristics of the fungal mycelia under the different temperatures (25, 28, and 30°C), and culture media [yeast extract agar (YEA), potato extract agar (PEA), malt extract agar (MEA), and also HS and BS extract agar media supplemented with maltose, dextrose, and fructose revealed that the highest mycelial growth rate (MGR; 7.5 mm/day) belonged to HS and BS extract agar media supplemented with three mentioned sugar at 28°C. In A. cornea spawn study, the substrate combination of BS (70%) + WB (30%) at 28°C and moisture contents of 75% displayed the highest mean MGR (9.3 mm/day) and lowest spawn run period (9.0 days). In the bag test, "BS (70%) + WB (30%)" was the best substrate displaying the shortest spawn run period (19.7 days), and the highest fresh sporophore yield (131.7 g/bag), biological efficiency (53.1%) and number of basidiocarp (9.0/bag) of A. cornea. Also, A. cornea cultivation was processed to model yield, biological efficiency (BE), spawn run period (SRP), days for pinhead formation (DPHF), days for the first harvest (DFFH), and total cultivation period (TCP) by multilayer perceptron-genetic algorithm (MLP-GA). MLP-GA (0.81-0.99) exhibited a higher predictive ability than stepwise regression (0.06-0.58). The forecasted values of the output variables were in good accordance with their observed ones corroborating the good competency of established MLP-GA models. MLP-GA modeling exhibited a powerful tool for forecasting and thus selecting the optimal substrate for maximum A. cornea production.

Hygrothermal behaviour of hemp-lime walls: the effect of binder carbonation over time

Bio-based building materials are produced by recovering agricultural biomasses which are used as vegetal aggregate to replace traditional ones and realize more sustainable building materials. This study focuses on hemp-lime that is made by mixing a lime-based binder with hemp shives i.e. the waste of industrial hemp cultivation. The work aims to evaluate the effect of the maturation of hemp-lime on its hygrothermal performances. Specifically, the binder undergoes carbonation reaction through which the strength of the material and its hygrothermal properties develop. With this aim, two experimental campaigns were carried out on an experimental wall built using prefabricated hemp-lime blocks: the first few months after the construction and the second one after 3 years. The wall, equipped with hygrothermal sensors, was subjected to cycles at varying relative humidity values and fixed temperatures applied with the help of a climatic chamber. The cycles were performed at 23 °C and 35 °C to focus on the performances of the material in conditions comparable to those of the Mediterranean climate. The results prove that hygrothermal performances improve with maturation, which could be due to the carbonation of the binder and to the reduction of the initial moisture content. Numerical simulations of the experimental tests were implemented using the software WUFI® aiming at confirming the experimental methodology and also the possibility of simulating the behavior of such innovative material in dynamic regime. The proceeding of carbonation was proved through X-ray diffraction (XRD) and thermogravimetric (TG-DTG) analyses of samples having different maturation times.

Influence of soil compaction and moisture variation on development of sesame (sesamum indicum l.) plant in a sandy loamy soil

This study determines the influence of soil compaction on shoot, root development and nutrients uptake of sesame (sesamum indicum l.) plant in a sandy loamy soil. The research was carried out in Mokwa local government of Niger state during wet season. Three soil samples of 300g weight from the top 20cm of the soil profile were taken from college farm. The initial moisture content of the soil was determined using oven-drying method. The soil samples were air dried, large clods broken and grounded. The soil samples were then mixed to obtain a homogenous mixture of the sample. The soil moisture content was then raised to varying moisture levels of 10%, 12%, and 14% exceeding the optimum moisture content of sandy loam which is 12% moisture. Each sample was subjected to five levels of compaction energy using 0,5,10,15,20 blows of a standard proctor hammer in cylindrical cores of 17cm in height and 10cm diameter in accordance with the standard proctor compaction procedure. Four holes were made in each can and four seeds were sown in each hole to be thinned into one seed per hole (four plants in each can). The depth of sowing was one cm. The seedlings were tinned to a maximum of five (5) per core at 15 days after planting. The heights (cm) of the seedling were taken with a measuring tape at 5-days interval to 20 days after planting. The experiment was laid out in randomized complete block design (RCBD). The data collected were subjected to descriptive statistical analysis, regression analysis and analysis of variance. The results from the soil physical properties analysis shows that the soil is sandy loam with sand being 76.8 % and clay as 11.2%. The bulk average density was 1.75 g/cm3. Results obtained from the study shows that compactive efforts significantly affect plant growth and development. It also shows that as compactive effort increases, the soil bulk density and penetration also increases. The effect of number of hammer blows on soil bulk density and penetration resistance was significant. The effect of excessive moisture also affects germination and plant growth. Moderate soil compaction has beneficial effect. This is due to greater water retention. In general, it appears that there is a great potential in growing sesame on sandy loam soil, if the level of compaction is maintained at moderate level, which does not impede root development and other plant requirements.

Moisture sorption isotherms characteristics for shelf-life prediction of peanuts (Arachis Hypogaea L.).

The spring grown peanut varieties J87 and TG37A are prone to quality deterioration as a result of high temperature and relative humidity during harvesting. Thus, the sorption isotherms of peanut varieties were evaluated at 25, 35 and 45 °C and the water activity (aw ) range of 0.110-0.975 aiming to predict the suitable storage conditions, packaging material and shelf-life. The equilibrium moisture content (EMC) increased with increased aw and isotherms of type II were observed. The monolayer moisture content varied between 3.135% and 4.235% for J87 and between 3.906% and 5.640% for TG37A variety. The experimental data were fitted to seven mathematical models. The variations in correlation coefficients were in the range 0.879-0.992 and in root mean square were in the range 0.055-1.988. On the basis of statistical parameters, Guggenheim Anderson de Boer and Double Log Polynomial were considered to be best fitted models. At aw of 0.6, critical moisture content (CMC) was 7.59%, 7.060% and 5.89% for J87 and 9.06%, 8.904% and 7.80% for TG37A at 25, 35 and 45 °C, respectively. The shelf-life prediction model provided that the aluminum packages had the maximum predicted shelf-life of around 1779 days for TG37A and 1077 days for J87 variety at 25 °C with an initial moisture content of 5.91% and 4.81%, respectively. The EMC and CMC evaluated from sorption study provided the basis for determination of package properties and shelf life. Aluminum packages had the minimum water vapor transmission rate and permeability. Hence, peanuts packaged in these bags and stored at 25 °C and 75% relative humidity had the potential to attain the maximum storage life. © 2023 Society of Chemical Industry.

Process design and optimization on self-sustaining pyrolysis and carbonization of municipal sewage sludge

Pyrolysis can realize the reduction and resource utilization of municipal sewage sludge (MSS). In this paper, a self-sustaining pyrolysis process is designed for municipal sewage sludge, and the process flow is simulated by Aspen plus software. By changing the initial moisture content of sludge, moisture content after drying, pyrolysis temperature and air supply in the incinerator, the possibility of achieving energy self-balance in the system is analysed. The simulation results show that by adjusting the parameters of the system, this process can realize the energy self-balance of sludge drying and pyrolysis treatment. Considering the system’s energy loss, the dry basis calorific value of sludge should not be less than 10 MJ/kg. The higher the initial moisture content of sludge, the more external energy input the system needs. It is recommended to dehydrate sludge mechanically to about 60 % before entering the system. When the pyrolysis temperature is increased, the amount of oil and gas produced by sludge pyrolysis increases, and it is easier to achieve self-balance of system energy. But the higher the pyrolysis temperature, the greater the energy consumption required. In practice, it is suggested that the pyrolysis temperature is about 400 °C. The moisture content of dried sludge has little effect on the energy self-balance of the system, and it is recommended to be about 30 %. The air supply volume of the incinerator mainly affects the flue gas outlet temperature and flue gas volume, but has little effect on the energy balance of the system.

Mathematical modelling and verification of open sun drying of cotton seeds

Abstract Researchers have carried out the kinetics of various agro products for open sun drying, but research articles still need to address such analysis for cotton seeds. Open sun drying of cotton seeds has been experimentally investigated and presented in this paper. Shorting of cotton seeds was carried out to collect appropriate samples in current research work. Cotton seeds were found to have a nearly ovoid shape with an average radius of 2 to 2.5 mm. The initial moisture content of cotton seeds was estimated to be 14.65% wet-basis using the hot air oven method. During drying, the reduction in the mass of cotton seeds was measured at every one-hour time interval. From this data, it was observed that drying occurred with a falling rate period. Drying data were fitted with 10 mathematical models available in the literature. Multi-regression analysis in Excel-solver equation was performed to obtain values of constants and coefficients of these models. Coefficient of determination (R2), reduced chi-square (χ2) and root mean square error were taken as criteria for the selection of the best drying model. The diffusion approach and models by Verma et al. were chosen as the most suitable drying models for open sun drying of cotton seeds. Effective diffusivity was estimated and found within the range suggested in the literature.

Recycling Nutrient-Rich Municipal Wastes into Ready-to-Use Potting Soil: An Approach for the Sustainable Resource Circularity with Inorganic Porous Materials

Using waste products is a promising and sustainable alternative to conventional non-renewable peat and nutrient-rich renewable materials. Their products are gaining importance for closing the loop in the ornamental plant industry. Porous inorganic materials have recently become potential bulking agents (BA) for sewage sludge (SS) owing to their high porosity, surface area, passivation capacity, high recycling potential, and potting soil components. The main purpose of the present work was to investigate the feasibility of pumice (PU) and expanded perlite (EP) on composting parameters, nutrient bioavailability and suitability of SS to serve as an ornamental substrate. The addition of PU and EP at 50% (v/v) resulted in higher porosity, optimal initial moisture content, higher temperature rise (56.24 ± 0.13 °C, 56.21 ± 0.11 °C, respectively), and higher CO2 evolution (39.41 ± 0.17%, 41.70 ± 0.22% daily peaks). Composting with inorganic BA at EP-50 and PU-50 mixtures was beneficial owing to high nitrogen content (3.82 and 3.70%, respectively) and readily bioavailable nutrients (270 mg kg−1 phosphates and 1835 mg kg−1 potassium). The use of PU and EP was found helpful in improving the slow-release nutrient properties of the compost. The overall results indicated that composting SS with PU and EP is a viable approach to achieve good composting properties and a good nutrient-providing profile if the compost is used as a component for potting soil components or garden soil amendments.

Moisture content distribution model for the soil wetting body under moistube irrigation

This study investigated the moisture distribution characteristics of a soil wetting body under different influencing factors to inform the design and management of a moistube irrigation system. A mathematical model of soil moisture movement under moistube irrigation was established based on Hydrus-2D software. The suitability of the Hydrus-2D simulation model was verified by laboratory experiments. Numerical simulations were carried out with Hydrus-2D to investigate the influence of soil texture, initial moisture content, moistube specific discharge and irrigation time on the moisture distribution of a soil wetting body. The soil moisture content is highest at the moistube, and its value is related to the moistube-specific discharge and soil texture. The soil moisture content at any point in the wetting body decreased linearly with increasing distance from the wetting front to the moistube in the five set directions (vertical downward, 45° downward, horizontal, 45° upward and vertical upward). This trend is applicable to fine-textured and coarse-textured soil. An estimation model of soil moisture content including soil saturated hydraulic conductivity, initial soil moisture, the specific flow rate of the moistube and the maximum value of the wetting front distance in all directions is proposed. The model estimation is good (root mean square error = 0.008–0.018 cm3·cm−3, close to 0; Nash-Sutcliffe efficiency coefficient = 0.987, close to 1), and it can provide a practical tool for moistube irrigation design and agricultural water management.