Search

Weeds reduce agricultural productivity by competing for resources intended for crops. Recently, the deactivation of weed seedbanks by microwave (MW) radiation has been developed as a chemical-free weed management practice. It is unknown, if these extreme heat disturbances permanently alter the soil microbiome of different farming systems. We performed a microcosm experiment to quantify the immediate and short-term effect of MW heating on the soil microbiome. We exposed three different soil types (representing dryland, temperate and irrigated farming systems) to MW heating, and monitored the fungal and bacterial communities over a month of recovery. Bacterial and fungal community composition were strongly dependent on the soil of origin. Following MW heating, bacterial and fungal richness decreased in all soils and did not recover during the period studied (four weeks). Notably, in all soils, bacterial communities became more dissimilar to each other following disturbance, but in fungi, this depended on the soil of origin. These results highlight the importance of considering the resistance and recovery of the resident soil microbiota in developing long-term sustainable MW-based weed management system.

Growing environmental awareness attracted research attention to the development of efficient methods in the recycling and the recovery of wastes. Microwave assisted pyrolysis (MWAP) is an alternative heating approach to convert organic waste materials into value-added products, such as biochar (BC), biogas and bio-oil. Different types of biochar materials have been produced through microwave heating technique that, in most of the cases, can be utilized for adsorption of organic and inorganic pollutants. The BC have been employed as CO2 mitigator and fertilizer for soils due to their promising physiochemical properties. In this review paper, we discuss the various aspects of Microwave assisted pyrolysis and the available case studies, as well as the mechanism of adsorption of different pollutants onto biochars. Development of microwaved biochar for other applications such as supercapacitors, batteries, electrode materials, and composite membranes are also discussed. It is believed that the development and synthesis of high potential biochar through microwave assisted pyrolysis still needs very precise adjustment of processing conditions, pre-treatment of feedstock and post treatment steps for further enhancement of properties for specific applications. The paper concludes that considering the sustainable route in development of high-performance biochar would make microwave assisted pyrolysis cost-effective, environmentally friendly, and tunable materials of great potential for wide range of applications.

Microwave soil heating deactivates weed seeds; however, in many modern agricultural settings, weed seeds are mostly found in the top 1–2 cm of the soil profile. Until recently, microwave soil heating has been achieved using various antennas, which project the microwave energy deeply into the soil. The aim of this research was to develop new microwave applicators that provide shallow heating (less than 50 mm). This paper presents two applicator designs, one based on a comb slow-wave structure and the other on the frustrated total internal reflection (FTIR) principle, which utilise evanescent microwave fields to restrict the depth of microwave heating. The background theory to their performance is presented, followed by experimental evidence of their constrained heating performance under different soil moisture scenarios. Experimental measurements of the heating performance of these applicators, in soils of varying moisture content, demonstrate that the evanescent microwave fields restrict the depth of heating, so that most of the energy is manifested in the top 50 mm of soil. The evanescent field decay rate for the FTIR applicator changes from 44.0 ± 0.7 m−1 to 30 ± 1.2 m−1 as the soil moisture changes from 32% to 174% (dry weight basis). This is higher than the evanescent field decay rate for the comb slow-wave applicator (17.6 ± 0.7 m−1 to 19.9 ± 1.5 m−1). The FTIR applicator has a wider and shallower heating pattern than the comb slow-wave applicator. Because of the double heating lobes of the FTIR applicator, the effective half temperature heating width is approximately 150 mm. This is wider than the half temperature heating width of the comb slow-wave applicator (95 mm).

Coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a rapidly spreading pandemic and is severely threatening public health globally. The human-to-human transmission route of SARS-CoV-2 is now well established. The reported clinical observations and symptoms of this infection in humans appear in the range between being asymptomatic and severe pneumonia. The virus can be transmitted through aerosols and droplets that are released into the air by a carrier, especially when the person coughs, sneezes, or talks forcefully in a closed environment. As the disease progresses, the use and handling of contaminated personal protective equipment and facemasks have become major issues with significant environmental risks. Therefore, providing an effective method for treating used/contaminated facemasks is crucial. In this paper, we review the environmental challenges and risks associated with the surge in facemask production. We also discuss facemasks and their materials as sources of microplastics and how disposal procedures can potentially lead to the contamination of water resources. We herein review the potential of developing nanomaterial-based antiviral and self-cleaning facemasks. This review discusses these challenges and concludes that the use of sustainable and alternative facemask materials is a promising and viable solution. In this context, it has become essential to address the emerging challenges by developing a new class of facemasks that are effective against the virus, while being biodegradable and sustainable. This paper represents the potentials of natural and/or biodegradable polymers for manufacturing facemasks, such as wood-based polymers, chitosan, and other biodegradable synthetic polymers for achieving sustainability goals during and after pandemics.

This study investigated the comparative effects of conventional hot-air oven heating (CHO), microwave heating (MW) and sealing effect on the nutritive value of lucerne hay. Equivalent energy (125 J.g−1) was applied with a 1.1 kW of MW oven for 60 seconds (s) or a 3.06 kW CHO oven for 350 s. The required equivalent energy level was measured based on a preliminary calibration trial. Two heating method (CHO and MW) and sealing condition (SC) applied as treatment factors in this study. A two-way analysis of variance (P < 0.05) was used to measure the effect of different factors on some properties of lucerne hay. The dry matter (DM) percentage of lucerne hay was increased when MW treatments were applied on both sealed and non-sealed lucerne hay compared with the control. Both heating method and their interaction with SC had negative effects on crude protein (CP) percentage. DM digestibility (DMD) and Digestible organic matter in the DM (DOMD) were decreased by 9% and 5%, respectively, in the sealed MW group, compared with the sealed control. Neutral detergent fibre % also increased by 6% in the sealed MW group, compared with the sealed control group. However, no differences in acid detergent fibre % due to any heating method and/or SC were observed in this study. The mechanisms behind these changes require further exploration.

The individual and cumulative effects of drought stress (DS) and heat stress (HS) are the primary cause of grain yield (GY) reduction in a rainfed agricultural system. Crop failures due to DS and HS are predicted to increase in the coming years due to increasingly severe weather events. Plant available silicon (Si, H4SiO4) has been widely reported for its beneficial effects on plant development, productivity, and attenuating physiological and biochemical impairments caused by various abiotic stresses. The current study investigated the impact of pre-sowing Si treatment on six contrasting wheat cultivars (four drought and heat stress-tolerant and two drought and heat stress-susceptible) under individual and combined effects of drought and heat stress at an early grain-filling stage. DS, HS, and drought-heat combined stress (DHS) significantly (p < 0.05) altered morpho-physiological and biochemical attributes in susceptible and tolerant wheat cultivars. However, results showed that Si treatment significantly improved various stress-affected morpho-physiological and biochemical traits, including GY (>40%) and yield components. Si treatment significantly (p < 0.001) increased the reactive oxygen species (ROS) scavenging antioxidant activities at the cellular level, which is linked with higher abiotic stress tolerance in wheat. With Si treatment, osmolytes concentration increased significantly by >50% in tolerant and susceptible wheat cultivars. Similarly, computational water stress indices (canopy temperature, crop water stress index, and canopy temperature depression) also improved with Si treatment under DS, HS, and DHS in susceptible and tolerant wheat cultivars. The study concludes that Si treatment has the potential to mitigate the detrimental effects of individual and combined stress of DS, HS, and DHS at an early grain-filling stage in susceptible and tolerant wheat cultivars in a controlled environment. These findings also provide a foundation for future researc

Feed nutritive value and its utilization by the animal are the two important factors that influence the profitability and sustainability of animal production systems. Microwave (MW) technology is one of the efficient technologies being used for physical processing of feed to improve feed nutritive value in the animal digestive system. Previous research has demonstrated that MW treatment may have been useful for improving feed digestibility and changing its utilization in animals’ bodies. Crude protein (CP) is one of the most important nutrients, MW treatment is effective at reducing concentrate feed CP rumen degradability, potentially leading to more efficient utilization of protein in the ruminant intestine. It reduces the anti-nutritional factors present in the feeds, which can limit animals’ intake and utilization. In this chapter, the application of MW treatment for feed processing and the prospects for the future use of MW technology in animal production systems will be discussed.

Bread wheat, one of the largest broadacre crops, often experiences various environmental stresses during critical growth stages. Terminal drought and heat stress are the primary causes of wheat yield reduction worldwide. This study aimed to determine the drought and heat stress tolerance level of a group of 46 diverse wheat genotypes procured from the Australian Grains Gene Bank, Horsham, VIC Australia. Two separate drought stress (DS) and heat stress (HS) pot experiments were conducted in separate growth chambers. Ten days after complete anthesis, drought (40 ± 3% field capacity for 14 days) and heat stress (36/22 °C for three consecutive days) were induced. A significant genotype × environment interaction was observed and explained by various morpho-physiological traits, including rapid, non-destructive infrared thermal imaging for computational water stress indices. Except for a spike length in DS and harvest index in HS, the analysis of variance showed significant differences for all the recorded traits. Results showed grains per spike, grains weight per spike, spike fertility, delayed flag leaf senescence, and cooler canopy temperature were positively associated with grain yield under DS and HS. The flag leaf senescence and chlorophyll fluorescence were used to measure each genotype's stay-green phenotype and photosystem II activity after DS and HS. This study identified the top ten best and five lowest-performing genotypes from drought and heat stress experiments based on their overall performance. Results suggest that if heat or drought adaptive traits are brought together in a single genotype, grain yield can be improved further, particularly in a rainfed cropping environment.

Rice grain arsenic (As) is a major pathway of human dietary As exposure. This study was conducted to reduce rice grain As concentration through microwave (MW) and biochar soil treatment. Collected soils were spiked to five levels of As concentration (As-0, As-20, As-40, As-60, and As-80 mg kg−1) prior to applying three levels of biochar (BC-0, BC-10, and BC-20 t ha−1) and three levels of MW treatment (MW-0, MW-3, and MW-6 min). The results revealed that MW soil treatment alleviates As phytotoxicity as rice plant growth and grain yield increase significantly and facilitate less grain As concentration compared with the control. For instance, the highest grain As concentration (912.90 µg kg−1) was recorded in the control while it was significantly lower (442.40 µg kg−1) in the MW-6 treatment at As-80. Although the BC-10 treatment had some positive effects, unexpectedly, BC-20 had a negative effect on plant growth, grain yield, and grain As concentration. The combination of BC-10 and MW-6 treatment was found to reduce grain As concentration (498.00 µg kg−1) compared with the control (913.7 µg kg−1). Thus, either MW-6 soil treatment alone or in combination with the BC-10 treatment can be used to reduce dietary As exposure through rice consumption. Nevertheless, further study is needed to explore the effectiveness and economic feasibility of this novel technique in field conditions.

Developing a mathematical model for the dielectric properties of water over a wide range of frequencies helps design, develop, model and optimize processes involving the interaction of electromagnetic waves with water containing materials. Based on large data sets (1744 published dielectric measurements) from literature and significant extensions to mathematical models, which have also been presented in literature, a comprehensive mathematical model for the most important dipolar responses and molecular resonances of water, from radio wave to the ultraviolet frequencies has been developed. This model provides a good approximation to published dielectric properties of pure water. Where possible, it also accounts for the influence of salinity and temperature.

Online monitoring and control of the drying processes are necessary to maintain the final products’ quality attributes, especially when a microwave system is used to facilitate the drying process. Machine learning techniques could be a suitable and very accurate approach for modelling the drying process. Two machine learning techniques including Support Vector Regression (SVR) and Artificial Neural Network (ANN) were employed to predict lentil seeds’ temperature and moisture ratio during drying in a microwave fluidised bed dryer with inputs of microwave power (0–500 W), fluidising air temperature (50 °C and 60 °C) and drying time. Mean squared error (MSE) and the coefficient of determination (R2) were used to evaluate the performance of the models. One hidden layer and 10 hidden neurons, the logistic sigmoid transfer function for the hidden layer, and a linear function for the output layer were determined to be the best structure for the ANN. Weights and biases were found by training the network with Bayesian Regularisation (trainbr) and the optimum MSE and R2 of the test set were 3.8×10-5 and 0.999 respectively. Optimised SVR could also provide a good model to predict MR and temperature (overall MSE = 1.96 ×10-4 andR2 = 0.995), although ANN provided relatively more accuracy for the temperature data. Therefore, ANN could be utilised as an accurate tool for the prediction of MR and temperature of lentil seeds during microwave fluidised bed drying.

Optimizing the location of wind and photovoltaic solar power plants is a significant environmental management problem. The effectiveness of the site selection process for renewable energy systems (RES) could be strengthened by flexible spatial and environmental planning strategies using decision support systems (DSS) to critically identify the most productive, environmentally friendly and acceptable sites for the production of sustainable and reliable wind and solar energy. This study discusses hybrid DSS, using multi-criteria evaluation based on the analytical hierarchy process (AHP), a geographical information system (GIS), fuzzy logic, and a weighted linear combination (WLC) approach to determine optimal locations for renewable energy generation infrastructure. In the first stage, the most decisive factors for evaluating the site suitability were identified, based on experts’ opinions. Next, raster layers of ecological and socioeconomic sub-criteria were prepared GIS software. After incorporating the raster maps of each parameter, fuzzy membership functions were applied to normalize each raster layer between 0 and 1. The relative weights of different indicators were calculated using super decision software. Prioritizing vital elements were performed using AHP. In the final stage, the WLC approach was utilized to amalgamate layers in the GIS environment, which afforded the final site suitability maps. In Isfahan Province, Iran, 26% of the land area was found to be highly suitable for solar farms with 18% being highly suitable for wind farms. The results illustrate that using and comparing the results from combinations of computer-based DSS are more likely to result in better decisions than using individual DSS tools for the determination of the most suitable sites for RES location.

With water resources constantly becoming scarcer, and 70% of freshwater used for the agriculture sector, there is a growing need for innovative methods to increase water use efficiency (WUE) of food production systems and provide nutrient-dense food to an increasing population. Sensor technology has recently been introduced to the horticulture industry to increase resource use efficiency and minimize the environmental impacts of excessive water use. Identifying the effects of irrigation levels on crop performance is crucial for the success of sensor-based water management. This research aimed to optimize WUE in a soilless microgreen production system through identification of an optimal irrigation level using a sensor that could facilitate the development of a more efficient, low-cost automated irrigation system. A dielectric moisture sensor was implemented to monitor water levels at five irrigation setpoints: 7.5, 17.5, 25, 30, and 35 percent of the effective volume of the container (EVC) during a 14-day growth cycle. To validate the sensor performance, the same irrigation levels were applied to a parallel trial, without sensor, and water levels were monitored gravimetrically. Plant water status and stress reaction were evaluated using infrared thermal imaging, and the accumulation of osmolytes (proline) was determined. Results showed that, proline concentration, canopy temperature (Tc), canopy temperature depression (CTD), and crop water stress index (CWSI) increased at 7.5% EVC in both sensor-based and gravimetric treatments, and infrared index (Ig) and fresh yield decreased. The dielectric moisture sensor was effective in increasing WUE. The irrigation level of 17.5% EVC was found to be optimal. It resulted in a WUE of 88 g/L, an improvement of 30% over the gravimetric method at the same irrigation level. Furthermore, fresh yield increased by 11.5%. The outcome of this study could contribute to the automation of precision irrigation in hydroponically grown micro

Dielectric properties of any particular material will determine the level of microwave (MW) heating. Therefore, measurement of the dielectric properties of MW treatment subject materials is necessary. This study investigated the dielectric properties of six roughages and three concentrate animal feeds across the microwave frequency range of 1 × 109 to 5 × 109 Hz. Six treatment groups, named control (at equilibrium moisture constant), oven dried (0% moisture), 25% moisture added, 50% moisture added, 75% moisture added, and 100% moisture added groups were prepared for the study. Three separate replications and five observations for each replication were used to assess the dielectric properties of these materials. The results showed that for increasing moisture content, from oven-dried, though the control status, to 100% added moisture, both the dielectric constant (real part) and the dielectric loss factor (imaginary part) increased for both the roughages and concentrates. However, the responses were not linear. The oven-dried plant samples' dielectric properties were very low compared with those of the higher moisture content samples. Thus, the sample's moisture content was the dominant contributor to the feed samples' dielectric behavior. Among all the feed samples, faba bean and wheat grain showed the highest response to added moisture. Mathematical models were developed to explain the dielectric properties of feeds as a function of frequency and moisture content. The goodness of fit (r2) for these models' real part varied between 0.85–0.99 for roughage and 0.98–0.99 for concentrate feed type. On the other hand, the goodness of fit for the imaginary part varied between 0.59–0.78 for roughage, and 0.81–0.93 for concentrate feeds.

In agriculture and industry, it is often necessary to heat surface layers of material like soil, timber, concrete, and so on, with microwave (MW) energy. Traditional MW irradiators (antennas) cannot restrain their heating to the surface, with the energy penetrating deeply into the material. Slow-wave comb applicators can provide the required energy distribution in the surface layer. Theoretical analyses of the comb applicators used for heating were carried out and on this basis, three comb applicators were designed and made for soil treatment: two applicators Comb 1 and Comb 2 for frequency 2.45 GHz and Comb 3 for frequency 0.922 GHz. An experimental study of applicators was carried out using two MW plants: 30 kW (2.45 GHz) and 60 kW (0.922 GHz) for heating soil with moisture content in the range from 32% to 173% and density 460 to 1290 kg m−3. The study showed that comb applicators provide the following advantages: reduction in energy dissipation in material depth and release of the significant part of applied MW energy in layers close to the applicator surface. Comb applicators can provide the required soil top layer treatment (sterilization) with reasonable efficiency and can be recommended for practical use in shallow soil treatment for weed seed and pathogen control in agricultural applications. Comb applicators can also be used for effective heating and MW treatment of the surface layers of wood, concrete, bricks, plastics, and other dielectric materials.

A microwave fluidized bed has proven to be substantially more efficient than a conventional fluidized bed dryer in food and agriculture. However, its effect on the quality attributes of the grains, have not yet been fully discovered. In the present study, the effect of microwave fluidized bed drying with the aim of pest and pathogen control, utilising microwave powers of 0, 300, 400, 500 W (0, 3.6, 4.8 and 6 W g−1 dry seeds, respectively) and fluidizing air temperature of 50 and 60°C, on the quality traits of lentil seeds were examined by measuring antioxidant enzyme activities, cooking quality and macronutrients analysis using Fourier transform infrared micro spectroscopy. A reduction in Peroxidase activity was observed at powers of 3.6 and 4.8 W g−1 and fluidizing air at 60 °C. The hardness of soaked and cooked seeds increased after drying at 6 W g−1 with both air temperatures and at 4.8 W g−1 with an air temperature of 60 °C. Based on the results of FTIR, no conformational changes in the protein secondary structure were observed at microwave powers of 0, 3.6, and 4.8 W g−1. Therefore, controlling microwave radiation utilising hot air for agitation could prevent any negative effect on the grain quality attributes.

Eucalyptus saligna tends to develop defects during its drying process, thus limiting its use as construction or furniture material. Intermittent drying, which applies non-heating phases between heating phases, has the potential to overcome this issue. This study evaluated the effects of 3 intermittent and 1 continuous schedule on the species’ drying performance and post-drying qualities. The results showed that the boards from all intermittent schedules exhibit significantly slower drying rates (from -9.4x10-3 /hour to -1.57 x10-2 /hour) than those from the continuous schedule (from -5.12 x10-2 /hour to -1.03 x10-2 /hour). The intermittently-dried boards also developed lower collapse depth (1.162-2.032 mm) than the continuously-dried boards (5.12 mm). Nevertheless, applying higher temperature than that used in the continuous schedule, during the heating phase of the intermittent schedule, potentially increased the moisture gradient, residual drying stress, end check length, internal check percentage, and spring depth.

Botrytis grey mould (BGM) is a problematic seed-borne disease of lentil crop, with little known about its possible physical control. Microwave fluidized bed dryers have been widely studied for grain, fruit and vegetable drying. In the present study, simultaneous drying and disinfection of red lentil seeds, were investigated in a microwave fluidized bed at 4 microwave powers of 0, 300, 400 and 500 W using fluidizing hot air at 50 and 60 °C. Moisture diffusivities of lentil seeds were defined by considering the Fick's second law of diffusion in one direction in a sphere with convective boundary conditions as well as negligible external resistance to mass transfer. They varied from 0.44 × 10−10 for hot air alone at 50 °C to 3.06 × 10−10 m2/s for microwave power and air temperature combinations of 500 W and 60 °C by considering convective boundary condition for the seeds. Drying times obtained from well-fitted Page's model were applied for drying of the seeds contaminated with BGM. The results indicated that infected seeds percentage (IS%) could be reduced by 30% by applying combinations of microwave power and hot air at 300 W and 60 °C or 400 W and 50 °C, without a significant loss of seed viability. Thus, microwave fluidized bed drying has a good potential to reduce seed born BGM in lentil crop.

Wooden power poles and their ongoing inspection represent a significant investment for most electrical power utilities. This study explored the potential for using microwave fields to non-invasively assess the state of hardwood power poles in a field experiment. Two strategies were assessed: 2.4 GHz microwave field transmission through the pole; and mutual coupling between antennae using a 10.525 GHz radar module applied to the surface of the pole. Both systems distinguished between sound hardwood poles and those which were compromised by decay and subterranean termite attack and infestation.

Growing herbicide resistance has encouraged the development of new technologies for weed control. Microwave (MW) heating of soil before sowing has been shown to reduce weed establishment in no‐till farming systems and substantially increases crop productivity. However, the effect of this technology on the soil microbial community in general, and on beneficial soil microbes such as ammonia oxidizers in particular, warrants further study. In order to check the effect of MW soil disinfestation treatments on the soil biota, indigenous soil microcosms were treated under a horn antenna of the MW prototype for three distinct durations. Immediately after heating (T0) and 28 days after heating (T28) the soil was collected at two penetration depths (0–5 and 5–10 cm) of MW energy to determine the bacterial community responses based on 16S rRNA amplicon sequencing and the total abundances of bacteria and ammonia oxidisers with qPCR. Although total bacteria and ammonia oxidizer abundances exhibited no response to the MW treatments, bacterial community composition differed according to the treatment durations. Community responses clustered into two categories: no effect at low heating intensities (0 and 30 s, 17–45°C) and strong effect at high heating intensities (60 and 90 s, 65–78°C). For the latter group, community richness did not recover to its pre‐heating levels within the 4 weeks studied. Immediately after high heating intensity treatments, the relative abundance of Firmicutes increased and that of Proteobacteria decreased significantly regardless of penetration depth. The relative abundances of beneficial soil microbes (Micromonosporaceae, Kaistobacter and Bacillus) were significantly higher as soils recovered from high heating intensities compared with untreated soils at T28. Our findings suggest that although pre‐sowing MW treatments alter the soil microbial community, beneficial soil microbes exhibit faster recovery. Highlights High heating intensities reduced

To investigate the effects of microwave (MW) treatment on hays nutritive value, five types of hay (50 g) were treated with MW for 0 (control), 20, 40, 60, and 80 s (0, 440, 880, 1320, and 1760 kJ kg−1 of MW energy, respectively) and analyzed for nutritive value prior to scanning by an electron microscope to observe microstructure changes. The dry matter (DM) % of hays were increased with increasing treatment time (p < 0.001). The improved DM and digestible organic matter in the DM were recorded from MW treated lucerne (60 s), wheat (40 s), and canola (20 s) (p < 0.001), which might have been due to the MW ruptured cell wall. The MW energy required for maximal DM digestibility improvement was linearly related to control hay crude protein content (r2 = 0.79; p < 0.001). Overall, the study showed MW treatment can increase some hays’ digestibility. In addition, the crude protein content from control hay may be a proxy to indicate DM digestibility improvement.

In the original publication, the figures 4 and 5 were swapped mistakenly. The correct figures with their caption are provided in this correction.

In this study, four textural classes of soil (Clay, Clay Loam, Loam, and Loamy Sand) were used to investigate the dielectric properties of soils, using a vector network analyser with an open-ended coaxial probe kit at room temperature (25 ± 2°C) in the 700–7000 MHz microwave frequency range. Four levels of soil moisture content (oven dry, 33% field capacity, 66% field capacity and 100% field capacity) were maintained to perform the experiment with three replication and three observation each. The results showed that, with increasing soil moisture, from oven dry conditions to 100% field capacity, both the real (Dielectric Constant) and imaginary (Loss Factor) components of the dielectric properties increased; however, the responses were not linear. The dielectric properties of oven dry soils were very low compared with the soils with higher moisture content. Therefore, soil moisture was the major contributor to the dielectric behaviour of soil. The dielectric properties of sandy soil were much lower than the other soils; however, the dielectric loss factor of the Dookie clay soil was higher compare with the other soils. Models were developed to explain the dielectric properties of soils as a function of frequency and moisture content. The goodness of fit (r2) for these models varies between 0.952 for the Dookie Sandy Soil to 0.997 for the Dookie Loam Soil, suggesting that these models were adequate to describe the dielectric properties of these soils over the range of frequencies and moisture contents assessed in this study. Another model was developed to estimate the expected penetration depth of electromagnetic waves in these soils, based on the model of the dielectric properties. It was clear that penetration decreases with both frequency and moisture content. Low frequencies penetrate further into the soils than higher frequencies. Similarly, dry soils allow further penetration than moist soils.

Crop yield gaps can be partially overcome by soil sanitation strategies such as fumigation; however, there are fewer suitable fumigants available in the marketplace and growing concerns about chemical impacts in the environment and human food chain. Therefore, thermal soil sanitation has been considered for some time and microwave soil treatment has some important advantages over other thermal soil sanitation techniques, such as steam treatment. It is also apparent that microwave soil sanitation does not sterilize the soil, but favors beneficial species of soil biota making more nutrients available for better plant growth. From these perspectives, microwave soil treatment may become an important pre-sowing soil sanitation technology for high value cropping systems, allowing agricultural systems to better bridge the crop yield gap.

The aim of this study was to investigate the process of drying Eucalyptus delegatensis in a greenhouse solar kiln. Specific objectives were to assess stress formation, moisture gradients and timber distortion, the moisture content distribution within various sections of the timber stack, and internal checking and collapse development within the boards. The maximal temperature and relative humidity (RH) during day time were set at 430C/72% RH. In the night time the temperature was at ambient condition with 90% RH. The strain measurements were undertaken before and after the samples were sliced. The timber quality at the end of drying was assessed based on Australian and New Zealand standard (AS/NZS 4787:2001). The moisture content values in the three different sections (front, middle and end) of 2400 mm long boards were compared by Analysis of Variance. The results showed that the mean compressive strain was -2 x 10-4 mm/mm in the core layers and the tensile strain was 14 x 10-4 mm/mm in the outer layers. All sample boards were within the acceptable limits for cupping, spring and bow, even though the relative humidity level did not reach the set value. However, the amount of twist in three out of twelve sample boards was above the acceptable limit. Mean moisture gradient was 0.6%. There was a significant difference in moisture content at end section compared to the front and middle sections. Internal checking, collapse and residual stress were graded as Class “C” (class A is the highest grade and D is the lowest).

Phosphorus (P) scarcity and eutrophication have triggered the development of new approaches for phosphorus recovery. This study investigated the impact of calcium-doped biochar, produced from biosolids via microwave pyrolysis at 700 °C for 20 min, on phosphorus recovery. The phosphorus removal isotherms, removal kinetics and the impact of initial pH of phosphorus solution on phosphorus recovery were studied. The phosphorus recovery was proportional to the calcium content in biochar, leading predominantly to the production of brushite. Precipitation was the main mechanism of phosphorus removal by calcium-doped biochar. Phosphorus removal capacity of biochar reached equilibrium after 8 h of contact time and was described by a pseudo-second-order kinetic model. The Langmuir isotherm model fitted the experimental data well with a maximum adsorption capacity of 147 mg-P/g for biochar BC20 (20 wt% Ca(OH)2). The results of phosphorus removal from a real wastewater demonstrated that using Ca-doped biochar for phosphorus removal from contaminated streams is a promising alternative for phosphorus recovery as well as for biosolids management. Heavy metal leaching from Ca-doped biochar was much lower than from undoped biochar, and decreased as the amount of calcium in biochar increased.

The purpose of this study was to apply an intermittent drying schedule developed from a conventional kiln to a solar kiln. Implementing this experiment could help better understand the oscillation of the temperature inside a solar kiln and timber quality during drying progress. The theoretical recharge and discharge curves were used to predict the temperature inside the solar kiln using experimental data obtained previously using a solar kiln. The surface and internal checks were measured using ImageJ freeware, and the development of the Moisture Content (MC) profile was assessed by coring and slicing method for the Eucalyptus delegatensis boards during drying. The results showed that the recharge and dis-charge model can predict the temperature with less than 2 C error from the experimental data in the solar kiln. The total drying time to 12% MC was 87 days for the solar kiln. The drying rate was equivalent to the conventional kiln decreasing at an average rate of 0.2%per day. The surface check formation was found when the MC gradient between the core and the case of the board was greater than 42% at 9 days of drying in the solar kiln and conventional laboratory kiln. The applied drying schedule used in the solar kiln was success-ful and offered similar drying time. However, the oscillation of temperature in the intermittent drying will require further improvement to get closer conditions in a solar kiln.