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A 9.75 kW walk-behind type hand tractor powered 2-row fully automatic vegetable transplanter for individual paper pot seedlings was developed by considering the power availability, paper pot dimensions and space availability in the hand tractor after the complete removal of rotavator tillage assembly. It consisted of two sets of feeding conveyor, metering conveyor, seedling drop tube, furrow opener, soil covering device, an automatic feeding mechanism, a depth adjustment wheel and hitching arrangement. Horizontal slat-type chain conveyor was used as feeding conveyor and horizontal pusher type chain conveyor was used as metering conveyor. The automatic feeding mechanism, with a timing shaft, cam and clutch, was used to coordinate the working of feeding and metering conveyors. The vegetable transplanter carried 108 seedlings on two feeding conveyors in upright orientation, fed them to the metering conveyors and planted them in upright orientation in furrows. The performance of the vegetable transplanter was evaluated for transplanting tomato at 45 × 45 cm spacing in the field at a forward speed of 0.9 km h−1. Field capacity of the transplanter was found to be 0.026 ha h−1. It resulted in the saving of 68% labour and 80% time over the conventional method of manual transplanting. The planting rate of the transplanter was found to be 32 pot seedlings min−1 with 4% missed planting and 5% tilted planting. The soil covering efficiency of the developed vegetable transplanter was about 81% and the quality of transplanting was satisfactory.

The performance of several commercial and experimental software packages (Gotas, StainMaster, ImageTool, StainAnalysis, AgroScan, DropletScan and Spray_imageI and II) that produce indicators of crop spraying quality based on the image processing of water-sensitive papers used as artificial targets were compared against known coverage, droplet size spectra and class size distribution verified through manual counting. A number of artificial targets used to test the software were obtained by controlled spray applications and given droplet density between 14 and 108 drops cm−2 and a wide range of droplet size spectra. The results showed that artificial targets coupled with an appropriate image system can be an accurate technique to compute spray parameters. The between-methods differences were 6.7% for droplet density, 11.5% for volume median diameter

To date, studies have indicated that near-infrared technologies can be used to detect peaches with mechanically induced bruises. However, it is not clear whether different mechanisms of bruising have similar effects on optical properties of peaches, and which property has greater potential for identifying bruises in peaches. To answer these questions, the absorption coefficient (μa) and reduced scattering coefficient (μs') of non-bruised, collision-bruised and compression-bruised peach pulp and skin were measured using an integrating sphere system over 950–1650 nm and up to 3 days after bruising. The changes in soluble solids content (SSC), water content, firmness, and microstructure of peach pulp or skin were also investigated. The results showed that the SSC of non-bruised and compressed peaches increased, and the SSC of collided peaches decreased with time after bruising as did the water content and firmness of all samples. Bruises caused cell structure damage and cell rupture. Three absorption peaks (980, 1175 and 1420 nm) and two absorption peaks (1175 and 1440 nm) were noted for pulp and skin, respectively. Compression had more obvious effect on μa of pulp than collision. Except for shortly after bruising, μs' of bruised pulp was significantly lower (P ≤ 0.05) than that of non-bruised fruit. The correlations between optical properties and quality indices were affected by bruises. Mechanical bruising had a significant effect on μs', from which we conclude that measurements of the reduced scattering coefficient has great potential for identifying bruised peaches.

Ammonia (NH3) loss during field application of liquid manure (slurry) causes loss of nu- trients for the crops and contributes to contamination of the environment. The emission can be mitigated by different low-emission application technologies and slurry treatment prior to application. It is assumed that a reduced area for air-slurry interaction will reduce the emission. The NH3 emission mitigation potential of technologies intended to reduce manure-air contact by reducing the exposed surface area (ESA) of the slurry or enhancing slurry infiltration was investigated for cattle slurry applied on grassland. Treatments tested were: 1) removing solids by solideliquid separation of the slurry, 2) reduced ESA by narrow band application, and 3) application with a sub-surface-deposition (SSD) slurry application (creating aeration slots). For untreated cattle slurry NH3 emission was not reduced by reducing ESA, but application over aeration slots significantly decreased emission. How- ever, reduced ESA by band application reduced emission from separated slurry compared to broadcast applied slurry, but no additional reduction was obtained by using the SSD technique. Lower emission was generally observed from separated slurry compared to untreated slurry for all application methods. This study shows that a reduction in NH3 emission is not necessarily obtained solely by reducing the ESA. It is hypothesized that rapid surface drying or crust formation of the untreated slurry in the relatively warm sunny conditions of these trials mitigated NH3 emission, thereby masking the effects of a reduced ESA.

Fungi can infect paddy from the planting process through to storage. Contaminating fungi can produce aflatoxins that can persist in the paddy and in storage until it is used to make other products. In the interests of food safety, in this study, we aimed to control the growth of fungi in paddy during storage using mathematical modelling of a drying method that uses fluidisation at temperatures of 70–150 °C. We found experimentally that an increase in the drying rate was related to an increase in the drying temperature. Drying paddy at a high temperature hardened the texture of rice when cooked, owing to the starch gelatinisation. Drying could decrease fungal growth (FG) and aflatoxin content during storage; however, it also resulted in a decrease in the antioxidant properties of paddy. Mathematical modelling and a proposed FG equation were applied to predict a suitable drying condition. The optimal drying condition reduced the risk of FG in stored paddy by ~50% without affecting antioxidant properties.

Mechanical size reduction, due to its significant effect on transport phenomena and biodegradability, is the crucial initial step in the production of advanced biofuels. As is generally known, particle size reduction is high energy demand operation. Energy requirements were experimentally studied and mathematically modelled for the processing of wheat straw with 4.6% moisture content wet basis that was reduced in size using a knife mill. The characteristic particle sizes for wheat straw before and after milling were analysed using the Rosin-Rammler-Sperling-Bennet model of particle size distribution. Energy demand 0.7–21.2 kWh t−1 was reported for size reduction of wheat straw with size reduction ratio D50 equal to 1.13–3.86. Applying the theory of energy demand modelled by Rittinger, it was confirmed that treated wheat straw displayed brittle behaviour. Energy demand for size reduction of wheat straw can be therefore be estimated using Rittinger theory with Rittinger constant value of 9.9 kWh mm t−1.

Farm-scale anaerobic digestion is increasingly regarded as a greenhouse gas emission reduction measure. To get a full picture of its emission reduction potential, greenhouse gas emissions from digestate storage need to be assessed. This work quantifies methane (CH4) and nitrous oxide (N2O) emissions from farm-scale mono-digested dairy manure by continuous monitoring in an on-site digestate storage for three months, in autumn. A dedicated sampling method coupled with an on-line gas phase analyser was developed to enable continuous measurements over longer time periods. The proposed method was a refinement of existing closed chamber approaches and involved repeated sampling cycles, including a gas accumulation phase from which the emission rate was quantified. Daily average methane emissions per stored digestate volume varied from 4.6 to 14 g m−3 d−1, equivalent to 3.9 to 8.2% of the methane produced in the digester. Daily average nitrous oxide emissions varied from 0.004 to 0.13 g m−3 d−1. The total emission ranged between 170 and 478 g [CO2,eq.] m−3 d−1, up to 10% of which was attributed to nitrous oxide. Both methane and nitrous oxide emissions increased for a larger stored digestate volume and a higher temperature. The system under study was simulated through an anaerobic digestion model, taking into account prevailing operating conditions in the digester and digestate storage. Substrate-specific input values were identified by analysing the fresh dairy manure and digestate. The hydrolysis constant and gas–liquid transfer coefficient were estimated at 0.21 d−1 and 0.003 d−1, respectively, for simulation results to match experimentally observed methane emission values.

The experimental design and gas mixture selection is of great importance in the definition of optimal gas concentrations for use in storage of fresh produce. The aim of this study was to optimise O2 and CO2 concentrations under controlled atmosphere conditions to understand the effect on quality and shelf life of ‘Shelly’ mango fruit stored at 13 °C for 28 d. This was achieved by designing three experimental points (gas compositions = O2, CO2 and N2) using simplex lattice mixture design to (i) determine single and interaction effects of gas compositions on selected quality parameters and (ii) determine the optimal gas combination in order to maintain quality and prolonging shelf life of ‘Shelly’ mango fruit. The estimated model parameters coefficients successfully categorised the single and interaction effects of O2, CO2 and N2 gas compositions. The selected quality attributes experimental data was fitted well using the canonical Scheffe type special cubic model, resulting in coefficient of Determination, R2 = 0.70 to 0.97. The low O2 and high CO2 in CA-2 managed to retard ripening and mass loss, and reduce fruit softening and chlorophyll degradation. Positive relationship was observed for linear effect in all quality attributes, while binary and ternary interaction effects varied across all the treatments. The optimal gas compositions for storage of ‘Shelly’ mango fruit in terms of selected quality attributes ranged between 5 and 8% O2 + 5–9% CO2 + 86–91% N2. The results highlight the potential use of simplex lattice mixture design to optimise CA storage conditions.

A mechanistic model for ammonia removal in a countercurrent biological air scrubber was set up. This model was used to study the effect of the influent characteristics – air temperature, ventilation rate and ammonia load, on ammonia removal efficiency. Besides mass balances of the components participating in the biological conversions, the water mass balance and the heat balance were considered. The effects of the pH and the concentration of the nitrogen components on the driving force for mass transfer were examined. The model output was compared against experimental data from a pig housing facility. Simulations were performed to assess the usefulness of pH control and to investigate the effect of inflow air conditions on the ammonia removal efficiency. The study found out that although pH control affected the nitrogen component distribution in the washing water, it hardly affected the ammonia removal efficiency. Thus, pH control for biological air scrubbers is not recommended in practice, however, an on/off pH control system adding only acid at critical moments (pH above 7.5) could be considered. The variations in the ammonia removal efficiency are mainly caused by a changing ventilation rate rather than air temperature fluctuations or ammonia load.

Winter housing of dairy cows and beef cattle is common practise in north-western European countries such as the UK and Ireland. In cattle housing, urine and dung are deposited over a large floor surface area from which ammonia (NH3) emissions may rapidly occur. The application of additives to this emitting layer has the potential to significantly reduce NH3 volatilisation from cattle housing surfaces. A dynamic flow-through chamber based study was carried out to determine the NH3 abatement potential of 10 additives applied to dairy cow slurry covered concrete surfaces under simulated northwest European winter housing conditions. Peak NH3 fluxes for control (slurry only) treatments occurred at approximately 3–5 h post slurry application, peaking at 133 mg [NH3–N] m−2 h−1. Acidifiers offered the most potential for cost-effectively abating NH3 emissions from slurry-fouled surfaces by increasing the NH4+:NH3 ratio. Experimental data suggests that targeting a slurry pH of 6 at the housing floor stage can significantly reduce NH3 emissions from fresh excreta. Of the tested additives, alum was the most successful at abating NH3 emissions from slurry; particularly after 6 h (76% NH3 abatement), where the efficacy of alum was greatest relative to the other acidifiers. Alum was followed by calcium chloride (69%) and sulphuric acid (41%). Actisan, a commercially available bedding disinfectant was another successful NH3 abatement option (59% after 6 h). Caution is needed in extrapolating results from this chamber-scale study to cow house scale as spatial and temporal variability of excreta deposition and climatic factors create additional complexity.

This study presents the start-up and 1-year performance study of two full-scale biotrickling filters or biological air scrubbers at a pig fattening facility in terms of ammonia removal and nitrous oxide production. Two newly-built multi-stage biotrickling filters were continuously monitored for these gases and for washing water characteristics. Although pH and electrical conductivity in the washing water are used in practice as a cheap and easy way to monitor the ammonia removal efficiency of biotrickling filters at pig housing facilities, it was shown that the relation between these variables is not always straightforward. Setting up a nitrogen balance over both biotrickling filters suggested denitrification activity. Additionally, the effect of inoculation with activated sludge of a wastewater treatment plant was investigated by inoculation of one of the two biotrickling filters. The inoculated biotrickling filter showed a fast start-up of nitrification and hardly any nitrite accumulation in the washing water. The ammonia removal efficiency was higher and the nitrous oxide production was slightly lower in the inoculated biotrickling filter compared to the non-inoculated.

This paper proposes a classifier for contamination detection in fresh latex. It relates to a dry rubber content (DRC) measurement system implemented with a 1 GHz microwave reflectometer (MWR), which behaves anomalously when fresh latex field samples are contaminated with cassava flour or CaCO3 by 10% by mass or more. The relative permittivity ( e r ) of non-contaminated and contaminated samples were investigated and an algorithm for detecting contaminants is proposed. The performance of this algorithm was tested experimentally and practically significant contamination levels were diagnosed with high accuracy.

Anaerobic sequencing batch reactors (ASBR) are preferred for treating dilute wastewaters but the retention of adequate active biomass, in successive-cycles, is always a challenge. This research investigated the efficacy of using a cationic polyacrylamide (PAM) flocculant for enhanced sludge retention in an ASBR treating flushed dairy manure, operated under psychrophilic conditions. Three PAM doses (10, 25, and 50 mg [PAM] l−1) were tested in duplicate reactors. At 6 d hydraulic retention time (HRT) and dosing of the feed-manure, steady state specific biogas yield for the 50 mg [PAM] l−1 treatment was 491 ± 7 ml g−1 [TCOD] (56% greater than control). At 4 d HRT the 50 mg [PAM] l−1 dose resulted in 465 ± 8 ml g−1 [TCOD] (20% higher than the control) at steady state conditions. The ratio of total volatile fatty acid to alkalinity was 0.29 ± 0.08 during the 6 d HRT and 0.14 ± 0.02 during the 4 d HRT, which were both below the trigger point for digester souring. This study shows that the use of PAM for high sludge retention in ASBR is a viable approach for, not only enhancing biogas yield, but also for improved and high-rate treatment of flushed dairy manure under psychrophilic conditions.

An anaerobic digestion model was set up and applied to estimate desired methane production in the form of biogas as well as unwanted methane emissions associated with farm-scale digestion of manure. The generally accepted Anaerobic Digestion Model No. 1 was simplified assuming that hydrolysis is rate-limiting during anaerobic digestion of manure, mainly consisting of non-readily biodegradable compounds. Simulations were performed to demonstrate the effect of temperature and retention time on methane emissions resulting from long-term manure and digestate storage. Moreover, the overall carbon footprint of several manure management scenarios for Flemish dairy farms was assessed based on model simulations and literature data. The scenarios assessed, differed in the possible presence of a digester as well as in the manure collection and storage method. A reduction in methane emissions was achieved for lower manure storage temperatures (through external storage) and by decreasing the stored manure volume and thus the storage time before (controlled) anaerobic digestion. At the same time, feeding fresh manure induced an increased methane production in the digester. The lowest carbon footprint could be achieved on dairy farms with fresh manure collection by a manure scraper, followed by controlled digestion and storage of the digestate in a gas-tight tank, located outside. The controlled digestion must take place in a properly managed and correctly dimensioned reactor as high digester methane losses and low digester retention times increase the carbon footprint significantly.

We propose an integrated system for simultaneous ammonia recovery, ammonia pretreatment, biogas upgrading, and fertiliser production in biogas production. Ammonia stripping and absorbing played an important role as they significantly affected the ammonia recovery and biogas upgrading performance. Ammonia stripping with biogas was used to remove ammonia from biogas slurry at various conditions. The ammonia removal efficiency reached 99.30% at 10% CO2 content, 90 °C and 6 h stripping time. Ammonia absorption of ammonia-bearing biogas achieved crystalline ammonium and biogas upgrading. The obtained crystalline ammonium was used for recovering ammonia. The ammonia pretreatment and anaerobic digestion results showed that wheat straw pretreated with 0.70% ammonia concentration and 105 °C obtained the highest biogas yield of 538.1 mL g−1, which was 31.9% higher than untreated wheat straw. The process in this study shows a great potential in biogas production by recycling ammonia for pretreatment of feedstocks and biogas purification associated with producing fertilisers.

[EN] Low frequency aeration of slurries may reduce ammonia (NH3) and methane (CH4) emissions without increasing nitrous oxide (N2O) emissions. The aim of this study was to quantify this potential reduction and to establish the underlying mechanisms. A batch experiment was designed with 6 tanks with 1 m3 of pig slurry each. After an initial phase of 7 days when none of the tanks were aerated, a second phase of 4 weeks subjected three of the tanks to aeration (2 min every 6 h, airflow 10 m3 h 1), whereas the other three tanks remained as a control. A final phase of 9 days was established with no aeration in any tank. Emissions of NH3, CH4, carbon dioxide (CO2) and N2O were measured. In the initial phase no differences in emissions were detected, but during the second phase aeration increased NH3 emissions by 20% with respect to the controls (8.48 vs. 7.07 g m 3 [slurry] d 1, P < 0.05). A higher pH was found in the aerated tanks at the end of this phase (7.7 vs. 7.0 in the aerated and control tanks, respectively, P < 0.05). CH4 emissions were 40% lower in the aerated tanks (2.04 vs. 3.39 g m 3 [slurry] d 1, P < 0.05). These differences in NH3 and CH4 emissions remained after the aeration phase had finished. No effect was detected for CO2, and no relevant N2O emissions were detected during the experiment. Our results demonstrate that low frequency aeration of stored pig slurry increases slurry pH and increases NH3 emissions., North Wyke Farm and technical support staff. Mr. R. Knox, Tor Pigs, Devon, UK for providing slurry. Spanish Ministry of Education, Culture and Sports, in the framework of the State Programme to Promote Talent and Employability in R + D + I, Sub-program on Mobility of the Plan on Scientific and Technical Research and on Innovation 2013-2016, and Spanish Ministry of Economy, Industry and Competitiveness (Project AGL2014-56653-C3-2-R). Rothamsted Research is supported by the UK Biotechnology and Biological Sciences Research Council.

In modified atmosphere packaging (MAP), the transpiration of the fresh product and exchange of water through the polymeric packaging are often not properly considered. This paper presents a mathematical model to describe the evolution in water vapour, O2 and CO2 concentrations in the packaging headspace, the weight loss of the product and the condensation of water in a MAP system with perforations. Transpiration was considered as the sum of water transferred out from the product due to the gain of energy from its respiration process and the difference in water activities between the product and the surrounding atmosphere. Respiration was represented using Michaelis–Menten enzyme kinetics. The gas transfer through the packaging and the perforations was described with Fick equations. The temperature influence on these processes was considered to follow the Arrhenius' law. To experimentally determine the model parameters, feijoa fruits (Acca sellowiana Berg) were stored under different storage conditions: packaging type, relative humidity and temperature. The completed model was subsequently validated in a MAP test by packaging fruits in perforated polypropylene (PP) and polylactic acid (PLA) bags for 13 days at 12 °C and 75% RH. Inside the PP bags, a saturated atmosphere (100% RH) was reached and 1.48% of the initial weight in the packed fruit was lost by day 13, while in the PLA bags, an equilibrium RH of 83% and a fruit weight loss of 3.29% were measured. The prediction capacity of the model was satisfactory, with coefficients of determination (R2) between 0.88 and 0.99 for the different tests.

Commercial harvest maturity of ‘Hass’ avocado fruit is estimated based on dry matter content (DM). Typically, a few samples representing the entire orchard are destructively analysed using time-consuming procedures such as oven or freeze drying the fruit's mesocarp. However, the maturity parameter of avocado, that is known to have a direct link to nutritional quality, is oil content (OC). This study was conducted to develop models for indexing maturity of on-tree avocado using a portable visible to near-infrared spectrometer. Rapid non-destructive models for assessing OC, DM and moisture content (MC) of avocado fruit were successfully developed using The Unscrambler® X chemometric software. Models robustness was assessed in an independent test set. There were non-significant differences (p > 0.05) between destructive and non-destructively assessed OC in terms of means (42.45 and 41.91%), standard deviations (4.79 and 4.87%) and coefficients of variation (11.34 and 11.62%) from the independent test set. The predictability of OC was associated with its high extractability caused by drying samples at high (75 °C) temperatures. The heat-drying technique can be used by other researchers to increase extractability and hence, the predictability of avocado OC during calibrations of alike non-destructive models. Commercial application of the developed models can improve maturity indexing since OC, DM and MC can be easily assessed without harvesting of sample fruit.

Transpiration and respiration are physiological processes well-known as major sources of fresh produce mass loss. Besides causing impairment of external quality, it is associated with economic loss since it inevitably decreases saleable weight. To prevent postharvest mass losses, by improved modified atmosphere and humidity packaging, comprehensive knowledge on the mechanistic basis of both processes and their interactions is essential. The objective of this study was to evaluate the contribution of these processes on mass loss of packaged and unpackaged strawberries. Experiments on a single strawberry were performed at 4, 12 and 20 °C; and 76, 86, 96 and 100% RH. Mass loss was also investigated as a function of number of strawberries and package volume at 12 °C. A combined model based on Arrhenius equation and Fick's first law of diffusion for an unpackaged single strawberry and a model based on degree of filling was developed and validated with packaged strawberries. These models have potential application towards the selection of optimal moisture control strategies for strawberries.

The aim of this preliminary feasibility study was to verify whether visible/near infrared(vis/NIR) spectroscopy could be used to predict the oil content of intact olives entering the mill, and of olive paste, pomace and pate during the milling process. Three different extraction methods (3-phase decanters, 2-phase decanters and 2.5-phase decanters) were considered, and two optical devices were tested: (i) a process device for non-contact analysis and (ii) a system equipped with an immersion probe for contact measurements, both working in the spectral range 400–1650 nm. 35 samples of olives were collected during the experimental tests, 50 samples of olive paste, 50 samples of pomace and 50 samples of pate. The collected samples (olives, olive paste, pomace and pate) were used to calculate partial least squares (PLS) regression models. Results regarding the non-contact analyses were encouraging, except for the measures on olives. On pomace, satisfactory models were calculated for the vis/NIR range [Ratio Performance Deviation (RPD) > 2], and a good model with R2 = 0.81 and RPD = 2.68 in validation was calibrated in the NIR range. The device equipped with an immersion probe achieved good predictive models for the oil content prediction on pate (R2 and RPD values ranged 0.77–0.82 and 3.00–3.43). The predictive models could be easily applied in an on-line system to monitoring the entire extraction plant and to perform a feed-forward control, allowing a reduction of oil leakage to minimise the oil losses and to maximise the extraction yield.

This study has been conducted to optimise the dry-thermophilic anaerobic co-digestion of two different types of real waste (municipal solid waste and biodiesel waste) in a semi-continuous feeding regime, under high organic loading rates (OLRs) or low hydraulic retention times (HRTs). For this purpose, different high OLRs (from 10 to 34 g [VS] l−1 d−1) or low HRTs (from 10 to 4.4 d) were investigated in a continuously stirred tank reactor. Optimal conditions (257 ml [CH4] g−1 VS; 6.03 ± 0.43 l [CH4] l−1 d−1; 16.3 ± 2.3 × 10−12 l [CH4] cell−1 d−1) were obtained at 4.4 d HRT (OLR = 23 g [VS] l−1 d−1), in which the average values of the ratios of Eubacteria:Archaea and hydrolytic-acidogenic bacteria:acetogens were 95:5 and 87:8, respectively.

The potential benefits of dry comminution in a knife mill for a diverse range of biomass 6 pellets are explored. The impact of dry comminution on energy consumption, particle size and shape, 7 is examined as well as the link between milling and mechanical durability. Biomass pellet comminution 8 energy was significantly lower (19.3-32.5 kW h t-1 [fresh] and 17.8-23.2 kW h t-1 [dry]) than values 9 reported in literature for non-densified biomass in similar knife mills. The impact of drying was found 10 to vary by feedstock. Dry grinding reduced milling energy by 38% for mixed wood pellets, but only 2% 11 for steam exploded pellets. Particle size and shape, particle distribution dispersion, and distribution 12 shape parameters changes between fresh and dry milling were also material dependent. Von Rittinger 13 analysis showed that to maximise mill throughput, pellets should be composed of particles which can 14 pass through the screen and thus have a neutral size change. A strong correlation was found between 15 pellet durability and energy consumption for fresh biomass pellets. Dry grinding has the potential to 16 significantly reduce energy consumption without compromising the product particle size, as well as 17 enhancing product quality and optimising biomass pellet comminution and combustion.

In this study, anaerobic co-digestion of cattle manure (CM) and meadow grass (MG) with serial configurations of continuous stirred tank reactors (CSTRs) was investigated. Four laboratory-scale CSTRs were operated at thermophilic condition (55 °C), of which two CSTRs were connected serially with equal working volumes while the remaining two CSTRs were operated as single CSTRs as controls. Improvements on bio-methane yield, methane contents and solids reduction were observed with serial CSTR configurations. The results showed that co-digestion with 5% (w/w) MG with serial configurations of CSTRs produced 24% more bio-methane compared with single reactor, with the total hydraulic retention time (HRT) being the same. The volatile fatty acids (VFA) concentration was found higher in the 1st reactor, but was reduced by 40–50% in the 2nd reactor. The improved bio-methane yield with serial CSTR configuration with 100% CM was 8%, indicating that the serial CSTRs process is superior in a co-digestion set up with addition of MG.

Drying uniformity is one of the most important indicators in evaluating a drying technique as well as the final quality of dried products. In the current study, three drying approaches (hot-air drying (HAD), microwave-vacuum drying (MVD), and the combined method (HAD + MVD)) were applied to dehydrate mango slices. During the HAD + MVD process, the time required for hot-air drying was determined in terms of colour variations during hot-air drying. With the help of hyperspectral imaging in conjunction with multivariate data analysis and image processing, the moisture content distribution on mango slices subjected to different drying methods was visualised. Results showed a non-uniform drying property for mango slices dried by HAD or MVD individually, where HAD-dried samples had a higher moisture content in the centre but MVD-dried samples showed the opposite result. Drying uniformity was improved when HAD and MVD were combined, which produced dried products with an even moisture distribution. Mango slice samples dried by HAD + MVD showed a porous structure and a high percentage of colour retention. The current study led to the development of an effective combined HAD + MVD technique for enhancing drying uniformity for the industry.

Microwave (MW) at 915 MHz has potential to achieve one pass rough rice drying. However, optimising processing parameters to maintain the rice quality is crucial. Effects of MW treatment on rice moisture removal, milled rice characteristics, and energy requirements for continuous one pass drying operation were quantified. Freshly harvested rough rice with initial moisture content of 25% wet basis was dried in a pilot-scale 915 MHz microwave dryer. The dryer was set to transmit MW power ranging between 3 and 24 kW during 8 min of drying. During treatments, rough rice was conveyed at bed thicknesses, 0.01, 0.03, and 0.05 m; supplied specific energy was maintained at 450, 600 and 750 kJ kg −1 of rough rice. Moisture removed varied between 6% and 15% points, depending on rice bed thickness (0.01–0.05 m) and applied specific energy (450–750 kJ kg −1 ). Increasing rice bed thickness and specific energy reduced milling and head rice yields, increased final viscosity of milled rice, but marginally affected rice peak viscosity and surface lipid and protein contents (p −1 and 750 kJ kg −1 of rough rice, 4574 kJ and 5986 kJ were required per kg of water removed, respectively; this translated to 13 and 16 USD per metric ton of dried rice, respectively. The study demonstrated feasibility of one pass MW drying of rough rice; 450–600 kJ kg −1 of rough rice was recommended to preserve rice quality and achieved better energy use efficiency.

Production of pelleted biomass for fuel is an emerging industry in the United States. Moisture content is a primary quality attribute of pelleted biomass materials because it is critical in binding, storage, combustion, and the pricing of pelleted biomass. To produce pellets of high quality, moisture content must be tightly controlled. A microwave system was designed for moisture sensing in flowing bulk material and used to determine feasibility of sensing moisture content in pelleted biomass from measurement of the dielectric properties at microwave frequencies. Samples of pelleted biomass derived from peanut hulls and pine sawdust were used for moisture content determination. Moisture contents of pine sawdust pellets ranged from 5.4%–9.9% (wet basis), and the range for peanut hull pellets was 8.9%–14.5%. At each moisture content, three different material flow rates were tested, and moisture content predictions were compared to those obtained with static measurement. Moisture content of flowing material was predicted by using a permittivity-based density-independent moisture calibration function. Root-mean-square deviations were computed for comparisons between reference moisture content, and predicted moisture contents for both static and flowing materials. Results showed that predicted moisture contents under static and flowing conditions were comparable.

The moisture sorption properties of typical biomass samples (tobacco stem, rice husk, wheat straw, cotton stalk, corn straw and rice straw) were investigated under different conditions, and the adsorption kinetics was analysed with pseudo order models. The equilibrium moisture content (EMC) was simulated with different models based on biomass property and adsorption process. Results showed that the adsorption process of biomass can be divided into two ranges: rapid adsorption and slow adsorption process. A pseudo-second order model could better describe the moisture sorption process than a pseudo-first order model. Equilibrium moisture content (EMC) mainly depended on biomass type and environmental humidity. A modified Halsey model provided the best fit to EMC of biomass and this model can be used to predict EMC of biomass.

Microwave-assisted retting was conducted at various power levels (1, 1.5 and 2 W g −1 ) on pre-soaked flax stems (12, 24 and 36 h). The retted flax stems were dried and the fibres were separated. The amount of cellulose, hemicellulose and lignin presented in the flax fibres was established by NIR (near infrared) spectroscopy. Based on the rate of change of cellulose, hemicellulose and lignin at various levels of treatments, a kinetic model was developed and the model was validated by analysing the compositions of hemp fibres obtained from pre-soaked hemp stems at various microwave power levels. The rate of change of cellulose percentage in the model fitted with the observed values of cellulose percentage with an average R 2 value of 0.87 and an average RMSE (root-mean-square error) value of 0.0130. But in hemicellulose, the R 2 value was 0.936 and average RMSE value was 0.0135, and for lignin, R 2 value was 0.92 and RMSE value of 0.0181. The rate coefficient for all the treatments was increasing within the treatment limit, which indicated the increased reaction rate with an increase in microwave power. Validation of the model was successfully conducted by analysing the components of hemp fibres at various levels of microwave powers.

The production of pelleted biomass represents a significant emerging industry in the United States. Solid biomass can be formed from the waste products of different natural and manufactured products. In this study, the effects of temperature and pellet material type on the dielectric properties were investigated. The resulting information was used to develop temperature- and material-independent moisture prediction equations. Dielectric properties of peanut-hull, pine, and hardwood pellets were measured at microwave frequencies for temperatures between 10 °C and 50 °C and at moisture contents between 4.9% and 16.0%. Further work was performed in investigating the dielectric properties of pine, peanut-hull, and hardwood pellets to determine whether a “unified” calibration for moisture content might be developed. Results showed that a temperature-compensated calibration for moisture content could be developed for different pellet types with standard errors of calibration between 0.50% and 1.04%. In addition, a unified calibration for pine, peanut-hull and hardwood pellets at 20 °C was developed that provides moisture content for the materials with a standard error of calibration between 0.48% and 0.56%.