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Transient heat conduction in a planar slab with convection and radiation effects
No full textThis article presents new semi-analytical solutions for transient heat conduction in a slab, which exchanges heat at the surface with its surroundings via convection, radiation, or simultaneous convection–radiation mechanisms. The concept of thermal penetration depth together with the integral method of heat balances form the basis of the formulation. Explicit expressions are derived that eliminate the need for numerical integration of the ordinary differential equations (ODEs) obtained from space integration of the heat equation. Verification of the temperature relations with a convection boundary condition is performed using an exact solution. In the case of radiation and combined convection–radiation boundary conditions, the accuracy of the explicit solutions is assessed against a numerical model. In all three cases, the new relations predict the surface temperature with high precision. For the radiation boundary condition, the computed midpoint temperature is also in excellent agreement with the numerical solution. In the case of convection heat exchange at the surface, the temperature at internal locations has close agreement with the exact solution for Biot numbers up to Bi = 1. The model prediction deviates from the exact solution in the interior positions for higher values of Bi with the highest deviation occurring at the center. For example, at Bi = 3, the highest relative error is 7.5%. Likewise, for the case of combined convection–radiation boundary conditions, the predicted midpoint temperature is found to closely follow the numerical solution at early stages of the process only. The predictability of the explicit solution of the convection-only boundary condition is more accurate than other approximate solutions at a Fourier number less than 0.2. Additional relations are presented for determination of the total heat transfer as a function of the Fourier and Biot numbers
Severe gastroenteropathy associated with Clostridium perfringens isolation in starving juvenile sturgeons
No full textIn November 2020 a mortality episode (30%) in juvenile Siberian and Russian sturgeons (Acipenser baerii, Brandt, and A. gueldenstaedtii, Brandt & Ratzeburg) and GUBA hybrid sturgeons (A. gueldenstaedtii × A. baerii) occurred in a hatchery in Northern Italy, associated with severe coelomic distension and abnormal reverse surface swimming. The fish were reared in concrete tanks supplied by well water, fed at 0.4% of body weight (b.w.) per day. Thirty sturgeon specimens were collected for necropsy, histological, bacteriological and virological examination. Macroscopic findings included diffuse and severe bloating of gastrointestinal tracts due to foamy contents with thinning and stretching of the gastrointestinal walls. Histological analysis revealed variable degrees of sloughing and necrosis of the intestinal epithelium, and the presence of bacterial aggregates. Anaerobic Gram-positive bacteria were investigated, and Clostridium perfringens was isolated from the gut. Specific PCRs identified the toxinotype A and the β2 toxin gene. The daily feed administration was increased to 1.5% b.w. and after 5 days, the mortality ceased. A new animal cohort from the same groups was examined after 12 weeks, showing neither gut alterations nor isolation of C. perfringens. The imbalance of intestinal microbiota, presumably caused by underfeeding, favoured C. perfringens overgrowth and severe gas formation. The diet increase possibly restored the normal microbiota
Exposure of embryonating eggs to Enterococcus faecalis and Escherichia coli potentiates E. coli pathogenicity and increases mortality of neonatal chickens
No full textEnterococci and Escherichia coli are opportunistic pathogens of poultry and are associated with embryo and neonatal chick mortality. We have recently demonstrated that 56% of dead broiler chicken embryos in commercial hatcheries in western Canada were due to the coinfection of Enterococcus species and E. coli. The objective of this study was to investigate the host-pathogen interactions of Enterococcus faecalis and E. coli in developing chicken embryos. Embryonating eggs at 12 d of incubation were dipped in a solution of E. faecalis and/or E. coli for 30 s to expose the eggshell to study the migration and colonization of E. faecalis and E. coli in the internal organs of chicken embryos and subsequent neonatal chicken mortality following hatch. A multidrug-resistant E. faecalis isolate from a dead chicken embryo and an E. faecalis isolate from a case of yolk sac infection were able to colonize the internal organs of chicken embryos rapidly compared to an E. faecalis isolate from a healthy chicken without affecting viability or hatchability of embryos. Although E. faecalis colonized internal organs of chicken embryos, no evidence of inflammation of these organs nor the expression of virulence genes of E. faecalis was observed. Although E. faecalis and E. coli alone did not affect the viability of embryos, a significantly high neonatal chicken mortality (27%) was observed following exposure of embryos to both E. faecalis and E. coli. Upregulation of IL-1 and CXCR4 was evident 48 h before peak mortality of neonatal chickens; this could suggest a possible link of cytokine dysregulation to increased mortality in coinfected neonatal chickens. However, further studies are warranted to investigate this issue vis-à-vis coinfection with E. faecalis and E. coli in chicken embryos and neonatal chickens.Alberta Agriculture and Forestry, Alberta, CanadaNatural Sciences and Engineering Research Council of Canad
Fundamental investigation of bio-surfactants-assisted harvesting strategy for microalgae
No full textThe lack of energy-sufficient harvesting technologies has dramatically impeded the commercialization of microalgae-derived bio-products. To address this challenge, a foam flotation harvesting approach using bio-surfactants has been previously developed for microalgae. However, most studies have applied chemical surfactants in the foam flotation, which is in opposition to the concept of sustainability. Thus, in this study, two bio-surfactants including rhamnolipid and Bovine Serum Albumin (BSA) were applied in foam flotation-assisted harvesting for Chlorella vulgaris. Initially, the ability of foam formation and foam stability in different microalgal culture media including distilled water, MiracleGro™, and Bold's Basal Medium (BBM) were evaluated. Following this, the microalgal cell adhesion mechanism was elucidated using FTIR analysis, zeta potential, and conductivity. The results showed that a higher degree of foam stability was observed when using BSA as the bio-surfactant than rhamnolipids. No big difference in the zeta potential was observed for BSA in all tested culture media, and the value of zeta potential was approx. 20 mV whereas, a difference was observed between rhamnolipid solution and rhamnolipid in culture media at all tested conditions. On the contrary, in the conductivity analysis, the use of rhamnolipids led to a higher conductivity at all investigated conditions compared to BSA. FTIR analysis suggested that the addition of either rhamnolipids or BSA did not affect the functionality. Overall, this fundamental study regarding the bio-surfactant-assisted foam flotation harvesting strategy for microalgae lays the foundation for process development.NSERCUniversity of Prince Edward Island (UPEI
Cultivating agricultural-riparian shrub willow to improve the sustainability of potato production systems in Prince Edward Island, Canada
No full textShrub willow (Salix sp.) is increasingly cultivated as a bio economy crop and for a range of environmental applications. Strategically cultivating Salix to maximize environmental utility could reduce production costs and justify incorporation in traditional agricultural settings. Cultivating Salix in agricultural-riparian transition areas has been proposed as an approach to reduce agriculturally derived indirect agricultural N2O emissions and enhance the surface water protection streams with potentially reduced production costs. The purpose of this research was to evaluate the environmental and economic implications of agricultural-riparian shrub willow buffers downslope of potato cropping systems on Prince Edward Island (PEI), Canada. The impact of Salix viminalis on shallow soil GHG emissions (N2O, CO2, CH4) was assessed relative to grassed buffers and upslope cultivated fields in potato rotation at five research sites. N2O, CO2, and CH4 flux at the soil-atmosphere interface was measured using non-steady-state static chambers. Nitrate exposure, soil temperature and soil moisture content were assessed. The biomass and nutrient accrual potential, below ground carbon (C) dynamics and economic viability of such a system receiving no direct fertilization was also investigated. Carbon, nitrogen, and phosphorus assimilation was measured in stem and root biomass at nine sites and a cost-benefit analysis assessed opportunities for bioenergy use and deployment. Water quality impacts were modeled by using the Soil and Water Assessment Tool (SWAT) to simulate nutrient and sediment loads in the Dunk watershed quality impacts of targeted, 30m 3-zone buffers incorporating shrub willow harvesting. 3-zone willow buffer effectiveness was compared to grass and forest buffers (15m and 30m), and optimal buffer width was assessed. Finally, an online quantitative survey was deployed to evaluate potato grower riparian landowner willingness, constraints, and opportunities to planting agricultural-riparian Salix buffers on PEI. Agricultural-riparian willow significantly mitigated N20 emissions, with mean cumulative seasonal reductions of 1.32 kg N ha-1 (-0.021 to 6.16 kg N ha-1) and a reduced mean cumulative global warming potential of 613 kg CO2e ha-1 in willow relative to cultivated fields. Salix viminalis displayed considerable site-to-site variation in biomass production, with water availability limiting growth. Mean annual yield was 0.25 to 16.59 T ha-1yr-1 (mean 3.9) while CO2 fixation was 0.67 – 46.64 T CO2 ha-1 yr-1 (0.26 - 18.17 T CO2 ha-1 yr-1 long term sequestration). Agricultural-riparian Shrub-willow production was economically viable for on-farm use when yields exceeded 5.6 T ha-1yr-1. Off-farm sale is not currently economically justified. Salix buffers displayed considerable water quality benefits. 30m 3-zone willow buffers removed 93.4% of sediment, 50.2% Total N and 64% Total P (5.6% and 7.5% more sediment, 4.1% and 12.6% more Total P, and -1% and 16.8% Total N than existing 15m grass and forest buffers). 15m 3-zone willow buffers removed significantly more particulate contaminants than15m forest buffers. Optimal 3-zone willow buffer width downslope of potato fields on PEI for diffuse pollutant mitigation was assessed to be 40m
Synthesis and characterisation of microbial acylated amino acids as potential biosurfactants
No full textCurrent synthesised surfactants available commercially have adverse effects on the environment due to their high toxicity and persist in the environment due to their low biodegradability. The need for sustainable and more eco-friendly alternatives to current surfactants is high and biosurfactants may be the solution. In this project, acylated amino acid biosurfactants being N-palmitoyl-L-valine and N-stearoyl-L-valine was synthesised to explore their surfactant properties as a potential alternative. The emulsification index was determined by E24 testing and it was observed that it can be considered a promising emulsifier which is a key surfactant property. Diffusion-ordered spectrometry (DOSY, NMR) was carried out on varying concentrations of these surfactants to determine their critical micelle concentration (CMC). The CMC is important in determining the aqueous solubility and dissolution of surfactant to efficiently reduce surface tension of liquid interfaces. The CMC is achieved in N-palmitoyl-L-valine with a lower concentration of surfactant compared to a common commercially used surfactant, sodium dodecyl sulphate, therefore this biosurfactant can also be considered to have excellent aqueous solubility and dissolution where smaller amounts can be used to reduce surface tension of liquid interfaces. Overall, N-palmitoyl-L-valine is a promising potential biosurfactant
Supercritical water gasification of lignocellulosic biomass: Development of a general kinetic model for prediction of gas yield
No full textSupercritical water gasification (SCWG) utilizes water as the reaction medium to convert biomass into a mixture of gases (i.e., H2, CO2, CO, CH4, and other short-chain hydrocarbons) at typical operating temperature ≥ 400 °C and pressure ≥ 23 MPa. Understanding kinetics of SCWG processes is critically important for future development and scale-up application of the SCWG technology. Thus, this study aimed to develop a general kinetic model to predict the yields of gases from SCWG of various lignocellulosic feedstocks with varying contents of cellulose, hemicellulose and lignin. The model was established based on the experimental results from K2CO3-catalyzed SCWG of various biomass model compounds including cellulose, xylan and lignin at 450–550 °C for 10–50 min, followed by validation of the model using the experimental data obtained from SCWG of real biomass (i.e., corn stalk and pinewood) under same reaction conditions. The validation results showed that the general kinetic model developed could accurately predict the yields of gases from real biomass SCWG and the quantitative influences of temperature and residence time on the gas yield in biomass SCWG. Additionally, the kinetic model has been validated other SCWG data in the literature obtained with various facilities and different lignocellulosic biomass feedstocks. The development of the general kinetic model provides an applicable way to assess the potential of SCWG of various lignocellulosic biomass feedstocks for producing combustible gases at various conditions
A mini-review: Biowaste-derived fuel pellet by hydrothermal carbonization followed by pelletizing
No full textThis review article focuses on recent studies using hydrothermal carbonization (HTC) for producing hydrochar and its potential application as a solid fuel pellet. Due to the depletion of fossil fuels and increasing greenhouse gas (GHG) emissions, the need for carbon-neutral fuel sources has increased. Another environmental concern relates to the massive amount of industrial processing and municipal solid waste, which are often underutilized and end up in landfills to cause further environmental damage. HTC is an appealing approach to valorizing wet biomass into valuable bioproducts (e.g., hydrochar), with improved properties. In this review, the effects of the main HTC reaction parameters, including reaction temperature, residence time, and feedstock to water ratio on the properties and yield of hydrochar are described. Following this, the pelletizing of hydrochar to prepare fuel pellets is discussed by reviewing the influences of applied pressure, processing time, pellet aspect ratio, moisture content of the hydrochar, and the type and dosage of binder on the quality of the resulting fuel pellet. Overall, this review can provide research updates and useful insights regarding the preparation of biowaste-derived solid fuel pellets.Discovery Grants Program, Natural Science and Engineering Research Council of Canada (NSERC
Functionalized organic–inorganic hybrid porous coordination polymer-based catalysts for biodiesel production via trans/esterification
No full textConsidering the increasing heavy energy demands and severe environmental issues, researchers have been searching for an alternative renewable source of energy, aiming to achieve carbon neutralization. Biodiesel, which is deemed as an environment-friendly, sustainable, and renewable energy, has attracted extensive concerns worldwide with the merits of non-toxicity, biodegradability, and carbon-neutral nature. Generally, biodiesel is mainly produced via the transesterification of triglycerides and esterification of fatty acids with the assistance of highly effective catalytic material, which is determined to be a critical issue for biodiesel production. Benefiting from the superiorities of huge porosity, uniform pore size, controllable functional group, and excellent activity with stability, organic–inorganic hybrid porous coordination polymers (OIHPCPs) are considered to be promising catalysts for biodiesel production. However, limited reviews have concentrated on the specific application of OIHPCP-based catalytic materials for the production of biodiesel. With this, this study systematically reviews the current application of OIHPCPs in catalyzing the trans/esterification of liquid biomass for biodiesel production, including pristine metal–organic frameworks (MOFs), functionalized MOFs (i.e., acid, base, bifunctional, and enzymatic), MOF derivates, unconventional MOFs (UMOFs), and biomass derivate coordination polymers catalysts. Besides, the important impacts of trans/esterification parameters, such as the amount of catalyst, type and molar ratio of alcohol, reaction temperature and time, water and fatty acids content of the substrate, and auxiliary production technology of biodiesel are also comprehensively evaluated. Finally, the corresponding plausible reaction mechanisms and main conclusions together with future perspectives for OIHPCP applications in biodiesel production are further emphasized. This review is timely and conducive for advancing the bioenergy realms and achieving carbon neutrality
Indigenous-led conservation in the Arctic supports global conservation practices
No full textAmid growing recognition for the role of global conservation initiatives in protecting biodiversity and mitigating climate change impacts, the interest in Indigenous-led and Indigenous-centered conservation in the circumpolar Arctic is also on the rise. Through literature and practice, Indigenous communities in the Arctic are shaping the global discourse around conservation approaches, mechanisms, and strategies, and are challenging colonial conceptions of how lands, waters, and species should be used, managed, and protected. Indigenous approaches, mechanisms, and strategies often differ from those found in the global conservation toolbox and rather focus on local priorities, Indigenous knowledge, traditional practices, sovereignty, and self-determination. Direction on how conservation should evolve and overcome challenges and related burdens is best given by Indigenous communities, scholars, organizations, and governments. Valuing Indigenous knowledge and supporting community-level initiatives, strategies, and practices comes with the benefits of understanding, forwarding, and implementing community priorities, needs, and values through attention and focus on funding, Indigenous-led research and management, and mutual mentorship. In addition to benefiting conservation itself, biodiversity research conducted within Indigenous homelands has the opportunity to serve as a model for how regional, national, and international initiatives best engage with Indigenous knowledge, conservation practice, and policy development in the Arctic and beyond