Areal Productivity Research Articles

Kinetics model with experimental validation for optimal microalgae generation in double-skin façades

Microalgae photobioreactors integrated into double-skin façades in cold climates enhance growth conditions for biomass generation, CO2 fixation, and O2 production, while reducing thermal loads. However, shading imposed by double-skin façade's assembly limits light interception for the photobioreactors. This study employs kinetics and shading models to estimate variations in biomass concentration within the light-constrained photobioreactor. To validate the accuracy and reliability of the model, the results were compared to experimental data collected by the authors from a full-scale constructed system. Biomass concentration was monitored using a developed RGB image-based monitoring technique. Direct search methods were employed to optimize the design and operational variables of the microalgae photobioreactors, with the goal of maximizing annual areal and volumetric productivities across 14 Canadian cities under various climatic conditions. Hooke-Jeeves algorithm was 65.6 % faster than Powell's conjugate direction method. This showed the system's adaptability by generating 1.3–3.0 kg/m2.year of biomass in different climates. The study established a framework for optimizing microalgae photobioreactors into façades to maximize biomass harvest.

High cell density culture of microalgae in horizontal thin-layer algal reactor: Modeling of light attenuation and cell growth kinetics

This study delved into the light intensity effects and light attenuation modeling in high cell density culture (HCDC) of green alga Neochloris oleoabundans. The research primarily focused on how different light intensities influence cell growth in terms of cell division and cell mass, and the biochemical composition within the cells. Recognizing the need to avoid overestimating light path by excluding data point in the data zone where the light intensity was zero, we proposed and verified a novel modified Beer-Lambert model, which was superb in fitting experimental data and predicting light attenuation in both low and high cell density cultures. Taking advantage of the prediction power of the modified Beer-Lambert model, we devised an approach to maintain constant mean light intensity (Imean) and by adjusting the incident light intensity (I0). The results indicate that at an Imean of approximately 66.67 μmol/m2/s and 6 mm culture thickness, maximum volumetric and areal biomass productivities of 2.72 g/L/day and 16.32 g/m2/day, respectively, were achieved. Whereas the highest biomass concentration of 28.20 g/L was produced in 20 days at Imean 50 μmol/m2/s. Photoinhibition to cell division become evident at I0 750 μmol/m2/s and above. Using the data generated at constant Imean in the constant specific growth rate range, superb fitting to the Monod model with a R2 of 0.9910 was demonstrated, highlighting the importance of generating reliable data for the modelling of the kinetics of photoautotrophic growth of microalgae, which had considered to be challenging.

Cultivation of Limnospira maxima under extreme environmental conditions in Saudi Arabia: Salinity adaptation and scaling-up from laboratory culture to large-scale production

Limnospira maxima has been adapted to grow in high salinity and in an economically alternative medium using industrial-grade fertilizers under harsh environmental conditions in Saudi Arabia. A sequence of scaling-up processes, from the laboratory to large-scale open raceways, was conducted along with gradual adaptation to environmental stress (salinity, light, temperature, pH). High biomass concentration at harvest point and areal productivity were achieved during the harsh summer season (1.122 g L−1 and 60.35 g m−2 day−1, respectively). The average protein content was found to be above 40 % of dry weight. Changes in the color and morphological appearance of the L. maxima culture were observed after direct exposure to sunlight in the outdoor raceways. These results demonstrate a successful and robust adaptation method for algal cultivation at outdoor large-scale in harsh environment (desert conditions) and also prove the feasibility of using hypersaline seawater (42 g kg−1) as an algal growth medium.

Downscaling crop production data to fine scale estimates with geostatistics and remote sensing: a case study in mapping cotton fibre quality

Abstract Purpose A generalised approach to downscale areal observations of crop production data is illustrated using cotton yield and fibre quality (length and micronaire) data which is measured as a module (areal/block) average. Methods Two features of the downscaling algorithm are; (i) to estimate spatial trends in yield and quality using regression with fine resolution predictors such as remote sensing imagery, and (ii) use area-to-point kriging (A2PK) to downscale either the observations in the absence of a useful spatial trend model or the residuals from the trend model (if useful) from areal averages. Results Correlations with remote sensing covariates were stronger for cotton fibre yield than for cotton fibre micronaire, and much stronger compared to those for cotton fibre length. Spatial trends in cotton fibre yield and micronaire could be estimated with good model quality using regression with remote sensing covariates with or without A2PK in almost all fields. Conversely, model quality was poorer for cotton fibre length and there was only a small difference in model performance between the null and trend models. When the downscaling approach was tested using fine-resolution yield observations, model performance was poorer at a fine-resolution compared to the module-resolution, which was to be expected. Conclusion This approach enables the creation of high-resolution raster maps of variables of interest with a much finer spatial resolution compared to the areal observations, and can be applied for any areal averaged crop production data in a range of broadacre and horticultural industries (e.g. sugarcane, apples, citrus). The finer spatial resolution may allow growers or agronomists to better understand the drivers of variability within fields, assess management implications, and create management plans at a higher resolution.

A comprehensive review on versatile microalga Tetraselmis: Potentials applications in wastewater remediation and bulk chemical production

Microalgae are considered sustainable resources for the production of biofuel, feed, and bioactive compounds. Among various microalgal genera, the Tetraselmis genus, containing predominantly marine microalgal species with wide tolerance to salinity and temperature, has a high potential for large-scale commercialization. Until now, Tetraselmis sp. are exploited at smaller levels for aquaculture hatcheries and bivalve production. However, its prolific growth rate leads to promising areal productivity and energy-dense biomass, so it is considered a viable source of third-generation biofuel. Also, microbial pathogens and contaminants are not generally associated with Tetraselmis sp. in outdoor conditions due to faster growth as well as dominance in the culture. Numerous studies revealed that the metabolite compositions of Tetraselmis could be altered favorably by changing the growth conditions, taking advantage of its acclimatization or adaptation ability in different conditions. Furthermore, the biorefinery approach produces multiple fractions that can be successfully upgraded into various value-added products along with biofuel. Overall, Tetraselmis sp. could be considered a potential strain for further algal biorefinery development under the circular bioeconomy framework. In this aspect, this review discusses the recent advancements in the cultivation and harvesting of Tetraselmis sp. for wider application in different sectors. Furthermore, this review highlights the key challenges associated with large-scale cultivation, biomass harvesting, and commercial applications for Tetraselmis sp.

Energy-Efficient Production of Microchloropsis salina Biomass with High CO2 Fixation Yield in Open Thin-Layer Cascade Photobioreactors

Lipid production using microalgae is challenging for producing low-value-added products. Harnessing microalgae for their fast and efficient CO2 fixation capabilities may be more reasonable since algal biomass can be utilized as a precursor for various products in a biorefinery approach. This study aimed to optimize the productivity and efficiency of Microchloropsis salina biomass production in open thin-layer cascade (TLC) photobioreactors under physical simulation of suitable outdoor climate conditions, using an artificial seawater medium. Continuous operation proved to be the most suitable operating mode, allowing an average daily areal productivity of up to 27 g m−2 d−1 and CO2 fixation efficiency of up to 100%. Process transfer from 8 m2 to 50 m2 TLC photobioreactors was demonstrated, but with reduced daily areal productivity of 21 g m−2 d−1 and a reduced CO2 fixation efficiency, most probably due to increased temperatures at midday above 35 °C. An automated overnight switch-off of the circulation pumps was implemented successfully, reducing energy and freshwater requirements by ~40%. The ideal conditions for continuous production were determined to be a dilution rate of 0.150–0.225 d−1, pH of 8.5, and total alkalinity of 200–400 ppm, facilitating efficient pilot-scale production of microalgal biomass in TLC photobioreactors.

Biofilm and suspension-based cultivation of microalgae to treat anaerobic digestate food effluent (ADFE)

Anaerobic digestion of organic waste produces effluent (ADE) that requires further treatment. Biofilm-based microalgal cultivation is a favoured approach to ADE treatment. This study compared Chlorella sp. MUR 268 and Scenedesmus sp. MUR 269 in biofilm and suspension cultures to treat anaerobic digestate food effluent (ADFE). Chlorella sp. MUR 268 biofilm had significantly higher biomass (50.38 g m−2) than Scenedesmus sp. biofilm (9.39 g m−2). Conversely, Scenedesmus sp. yielded 1.5 times more biomass (1.2 g L−1) than Chlorella sp. in suspension. Chlorella sp. biofilm had 49.3 % higher areal productivity than suspension, while Scenedesmus sp. showed 87.3 % higher areal growth in suspension. Chlorella sp. MUR 268 and Scenedesmus sp. MUR 269 significantly removed nutrients in ADFE. In suspension, COD, ammoniacal nitrogen, and phosphate were reduced to 94.9, 5.2, and 5.98 mg L−1 for Chlorella sp. MUR 268, and 245, 2.89, and 3.22 mg L−1 for Scenedesmus sp. MUR 269, respectively. In biofilm, Chlorella sp. MUR 268 achieved reductions to 149.9, 1.16, and 3.57 mg L−1, while Scenedesmus sp. MUR 269 achieved 100.2, 6.9 and 2.07 mg L−1. Most of these values are below the recommended effluent discharge standard, highlighting the efficacy of this system in ADFE treatment. Biofilm cultures fixed 68–81 % of removed nitrogen in biomass, while in suspension, only 55–71 % ended in the biomass. Chlorella sp. MUR 268 biofilm fixed 88 % of removed phosphorus, while Scenedesmus sp. MUR 269 suspension fixed more phosphorus (55 %) than the biofilm counterpart (34 %). This biofilm design offers advantages like simplified, cost-effective operation, easy biomass recovery, and reduced water usage.

Proximate biomass characterization of the high productivity marine microalga Picochlorum celeri TG2

Microalgae are compelling renewable resources with applications including biofuels, bioplastics, nutrient supplements, and cosmetic products. Picochlorum celeri is an alga with high industrial interest due to exemplary outdoor areal biomass productivities in seawater. Detailed proximate analysis is needed in multiple environmental conditions to understand the dynamic biomass compositions of P. celeri, and how these compositions might be leveraged in biotechnological applications. In this study, biomass characterization of P. celeri was performed under nutrient-replete, nitrogen-restricted, and hyper-saline conditions. Nutrient-replete cultivation of P. celeri resulted in protein-rich biomass (∼50% ash-free dry weight) with smaller carbohydrate (∼12% ash-free dry weight) and lipid (∼11% ash-free dry weight) partitions. Gradual nitrogen depletion elicited a shift from proteins to carbohydrates (∼50% ash-free dry weight, day 3) as cells transitioned into the production of storage metabolites. Importantly, dilutions in nitrogen-restricted 40 parts per million (1.43 mM nitrogen) media generated high-carbohydrate (∼50% ash-free dry weight) biomass without substantially compromising biomass productivity (36 g ash-free dry weight m−2 day−1) despite decreased chlorophyll (∼2% ash-free dry weight) content. This strategy for increasing carbohydrate content allowed for the targeted production of polysaccharides, which could potentially be utilized to produce fuels, oligosaccharides, and bioplastics. Cultivation at 2X sea salts resulted in a shift towards carbohydrates from protein, with significantly increased levels of the amino acid proline, which putatively acts as an osmolyte. A detailed understanding of the biomass composition of P. celeri in nutrient-replete, nitrogen-restricted, and hyper saline conditions informs how this strain can be useful in the production of biotechnological products.

Relationships between combined and individual field crops’ biomass and planting density

ContextField crops, irrigated and rain-fed, constitute the majority of cropland worldwide. An important agricultural variable determining their biomass production is planting density. ObjectiveThe objective of the study was to explore the relationships between the biomass (dry matter) and planting density for either major individual field crops or all field crops, combined, and to suggest empirical models describing them. MethodsThis article describes a meta-analysis of the literature data on biomass per unit area or plant versus planting density for 8 major field crops: 4 cereals (corn, wheat, sorghum, and pearl millet) and 4 forbs (soybean, sunflower, rapeseed, and buckwheat). ResultsWhen data from all 8 field crops are combined, it seems that areal biomass production is practically independent of planting density, apparently obeying the constant final yield hypothesis. By contrast, analyzing each of the 8 crops separately, there is a clear rising trend of areal biomass with increasing planting density, with a mean intraspecific allometric exponent of about 0.25, and individual exponents that increase systematically with a decrease in the average planting density. ConclusionsApplying a planting density-dependent allometric exponent improves the predictability of the interspecific biomass–planting density relationship for field crops. A bounding, exponential model that describes the biomass–planting density relationship in the agricultural range of 1–1000 plants per m2 better than power-law allometric equations is proposed. Although the biological meaning of a derived generic expression relating areal biomass to single-plant biomass for field crops is not clear, the deviation of the outliers probably reflects already utilized or remaining breeding potential for increased areal biomass and agricultural yields. ImplicationsA good understanding, quantification, and prediction of the biomass–planting density relationship is essential for both plant breeding and management of crop production. Plant breeders need this knowledge to choose between strategies for either increasing the single-plant biomass or increasing the plants’ tolerance to high planting density. Agronomists and extensionists need it to optimize planting density for a particular variety under given environmental and agricultural (GxExM) conditions.

A selection approach using high‑oxygen and pond-mimicking culture conditions increases biomass productivity in the industrially relevant diatom Nitzschia inconspicua str. hildebrandi

To meet the energy and food challenges of the 21st century, renewable and sustainable sources of fuel and nutrients are required. Microalgae offer promise in meeting these challenges but must achieve higher rates of areal productivity to compete with fully scaled, existing industries. In this study, we used selective O2 pressure to attain a ∼90 % increase in areal biomass productivity relative to the parental strain in the diatom Nitzschia inconspicua str. hildebrandi under pond-mimicking conditions with high O2 stress. The resulting culture line (GAI-337) was tested further for dilution time, culture density, CO2 supplementation, pH, temperature, and dissolved O2 concentration under outdoor pond-mimicking conditions to improve areal productivities. These experiments yielded an optimum harvest and dilution time just after sunset, ∼0.45 g AFDW L−1 initial culture density for maximal productivities, no requirement for CO2 gas supplementation or pH control, maximal performance under a diel temperature curve going from 24 °C at night to 36 °C during the day, and benefits from some O2 removal from the culture by bubbling with air. Using pond-mimicking laboratory bioreactors, N. inconspicua GAI-337 achieved ∼42 g AFDW m−2 d−1, placing it among the most productive microalgal strains tested to date. Nutrient limitation experiments resulted in a biomass composition with 36 % of AFDW comprised of lipids (measured as FAMEs) that equated to ∼160 Gallons of Gasoline Equivalent energy per ton AFDW, highlighting the potential of GAI337 as a promising renewable fuel feedstock strain.

On-Site Pilot-Scale Microalgae Cultivation Using Industrial Wastewater for Bioenergy Production: A Case Study towards Circular Bioeconomy.

This case study assesses the valorization of industrial wastewater streams for bioenergy generation in an industrial munition facility. On-site pilot-scale demonstrations were performed to investigate the feasibility of algal growth in the target wastewater on a larger outdoor scale. An exploratory field study followed by an optimized one were carried out using two 1000 L open raceway ponds deployed within a greenhouse at an industrial munition facility. An online system allowed for constant monitoring of operational parameters such as temperature, pH, light intensity, and dissolved oxygen within the ponds. The original algal seed evolved into an open-air resilient consortium of green microalgae and cyanobacteria that were identified and characterized successfully. Weekly measurements of the level of nutrients in pond liquors were performed along with the determination of the algal biomass to quantitatively evaluate growth yields. After harvesting algae from the ponds, the biomass was concentrated and evaluated for oil content and biochemical methane potential (BMP) to provide an estimate of the algae-based energy production. Additionally, the correlation among biomass, culturing conditions, oil content, and BMP was evaluated. The higher average areal biomass productivity achieved during the summer months was 23.9 ± 0.9 g/m2d, with a BMP of 350 scc/gVS. An oil content of 22 wt.% was observed during operation under low nitrogen loads. Furthermore, a technoeconomic analysis and life cycle assessment demonstrated the viability of the proposed wastewater valorization scenario and aided in optimizing process performance towards further scale-up.

Modifying filamentous algae nutrient scrubbers for improved wastewater treatment and harvestability - comparison with microalgae

Algae have been well studied for their abilities to treat wastewater, and several types of treatment systems have been demonstrated at a range of scales. High Rate Algae Ponds (HRAP) are a microalgae-based system and Filamentous Algae Nutrient Scrubbers (FANS) a filamentous algae-based system. For FANS, nutrient removal rates are typically lower and more variable than HRAPs, while HRAPs have lower productivity and poor harvestability. This study investigated if modifying a FANS to mimic HRAPs (using high rate algae mesocosms HRAM), with respect to hydraulic retention time (HRT) and smaller footprint, overcomes FANS limitations, while increasing wastewater treatment and resource recovery compared to HRAPs. Biomass productivity on the FANS (10.5 ± 2.9 g m−2 d−1) and FANS with CO2 addition (19.0 ± 4.8 g m−2 d−1) were significantly higher (p < 0.01) compared to the HRAMs (6.7 ± 1.4 g m−2 d−1) and HRAMs with CO2 addition (8.1 ± 1.2 g m−2 d−1). Under phosphorus replete conditions, biomass production was significantly higher on FANS (44.8 ± 14.4 g m−2 d−1) than HRAMs (5.0 ± 0.6 g m−2 d−1). Effluent quality (nutrient removal) was significantly higher (p < 0.05) for FANS compared to HRAMS, regardless of treatment. For harvesting, FANS (2.9–41%) yielded significantly higher (p < 0.01) percentage solids with, and, without dewatering/gravity harvesting compared to the HRAM (0.04–0.11%). Modifying the operation of the FANS to mimic longer HRT of HRAMs resulted in higher areal biomass productivity and nutrient removal in the FANS than the HRAM, regardless of treatment. The use of filamentous algae on FANS greatly improved the percentage solids yield in the harvested biomass without the need for energy intensive harvesting techniques. Further investigations need to be undertaken to determine if benefits will be realised at fullscale.

Syuzevskoye diamond placer: A new stage in studying the diamond potential of Western Urals

Research subject. Geological features of the structure and composition of the Syuzevskoye diamond placer in the Aleksandrovsky region of the Perm Krai. The placer was found in the border zone of two regional tectonic structures of the Urals: the Western Ural outer folding zone and the Central Ural uplift. This placer was developed within the erosion-karst (?), erosion-structural or tectonically determined Chikman-Nyarskaya depression. Materials and methods. The placer was identified in the period from 2017 to 2022 during a geological study of the subsoil area “Glubokiy” (License PEM 02687 KP LLC “Almining”). Mining and enrichment works were carried out according to the original enrichment scheme using the clamshell sampling method, heavy media and electromagnetic separation. The morphometric characteristics of several hundred diamonds were identified and described; reports were prepared; and reserves were assessed. Results. In the section of the Syuzevskoye placer, two diamond-bearing strata are clearly distinguished, separated by poor- and non-diamond-bearing deposits; anomalously high seam thickness for the Ural placers (up to 14-16 m) was established; high areal productivity of the placer (up to 0.7-1.2 ct/m2) and high diamond content (up to 0.5 ct/m3 per sample and an average of 0.09 ct/m3 for the placer). The placer is attributed to the type of placers of tectonic scarp zones. Reserves of alluvial diamonds weighing 430.5 thousand ct of the Syuzevskoye deposit are estimated at C1 + C2 categories in the area limited by the area between exploration lines 107-116 (size 1000 x 750 m); approved by the Minutes of the GKZ Rosnedra No. 7139 dated November 18, 2022 and will be increased. Certificate No. PEM 23 DRK 10147 confirming the discovery of a mineral deposit, issued by the Federal Agency for Subsoil Use of the Russian Federation to LLC Almining on March 29, 2023. Over 90% of diamonds are of gem quality. The average mass of crystals in the reserve calculation loop is 87 mg, and behind the loops is 29 mg. The leading size classes by mass -8 + 4 and -4 + 2 mm are 93.9% and 72.3% in quantity with an average mass of a diamond crystal of 99.9 mg. The shape is dominated by dodecahedroids (66.9%), less fragments of crystals with an unpreserved shape (14.9%) and fragments of crystals (13.1%); octahedrons (2.4%) and tetrahedroids (2.2%) are rare, rhombic dodecahedroids (0.4%) are rare. The preservation of crystals is good: full crystals make up 63.7%, fragments of crystals - 16.3%, fragments - 12.9%. Most of the crystals do not have wear (42.4%), or have weak wear of the tops and ribs (43.0%), medium and strong wear was noted only in 13.7% of the crystals. The average cost of diamonds is estimated at 361.59 USD per 1 ct. Conclusions. A unique deep-seated diamond deposit has been discovered, which is considered as a new type of deep-seated diamond-bearing placers in tectonic ledge zones. The geological criteria for identifying such diamond deposits in the Urals were determined. A new technological scheme for prospecting and exploration of deep-seated diamond placers within erosion-karst and tectonically determined depressions was developed, which is applicable for prospecting for precious metal placers.

Complementary chromatic adaptation as a strategy to increase energy conversion efficiency of microalgae-cyanobacteria consortia in continuous LED photobioreactors

Phototrophic cultivation of microalgae represents a potential sustainable process to obtain valuable commercial products, but the industrial cultivation is still hampered by low energy-to-biomass conversion efficiency. However, a number of cyanobacteria species evolved the ability to adapt to the prevailing light spectrum exploiting phycobiliproteins and Complementary Chromatic Adaptation (CCA). Spectral properties of such accessory pigments can be, hence, used to cover the green gap and possibly use light energy more efficiently. In this work, the green microalgae Tetradesmus obliquus and the chromatically adapting cyanobacterium Tolypothrix tenuis were cultivated as an alga-alga consortium in chemostat, aimed at increasing the light utilization efficiency in LEDs illuminated photobioreactors. When grown in co-culture, the advantage of consortium, with respect to monocultures, was maintained under different spectra, achieving an areal productivity up to 38 g m−2 d−1 under low red light. A remarkable photosynthetic conversion efficiency was reached under cocultivation, as a result of a wider absorption of photons with different wavelengths by the two species. Red light also resulted the most suitable one from the overall energy balance when artificial light is used. In this condition, by also considering the lamp efficiency, an overall conversion efficiency equal to 21% was reached (on Photosynthetically Active Radiations of RED light and calculated for the biomass of the two species together). The consortium performances were preliminary evaluated in continuous photobioreactors at pilot scale in 16 L and 160 L reactors, confirming the results obtained at lab scale. Hence, we found that is possible to efficiently convert light energy supplied to photobioreactors through a rationale use of light and widening wavelengths absorption spectrum thanks to co-existing species. Such results indicate that innovative consortia establishment can be advantageous for future research and industrial microalgae cultivation.

Experimental and theoretical investigations of rotating algae biofilm reactors (RABRs): Areal productivity, nutrient recovery, and energy efficiency.

Microalgae biofilms have been demonstrated to recover nutrients from wastewater and serve as biomass feedstock for bioproducts. However, there is a need to develop a platform to quantitatively describe microalgae biofilm production, which can provide guidance and insights for improving biomass areal productivity and nutrient uptake efficiency. This paper proposes a unified experimental and theoretical framework to investigate algae biofilm growth on a rotating algae biofilm reactor (RABR). Experimental laboratory setups are used to conduct controlled experiments on testing environmental and operational factors for RABRs. We propose a differential-integral equation-based mathematical model for microalgae biofilm cultivation guided by laboratory experimental findings. The predictive mathematical model development is coordinated with laboratory experiments of biofilm areal productivity associated with ammonia and inorganic phosphorus uptake by RABRs. The unified experimental and theoretical tool is used to investigate the effects of RABR rotating velocity, duty cycle (DC), and light intensity on algae biofilm growth, areal productivity, nutrient uptake efficiency, and energy efficiency in wastewater treatment. Our framework indicates that maintaining a reasonable light intensity range improves biomass areal productivity and nutrient uptake efficiency. Our framework also indicates that faster RABR rotation benefits biomass areal productivity. However, maximizing the nutrient uptake efficiency requires a reasonably low RABR rotating speed. Energy efficiency is strongly correlated with RABR rotating speed and DC.

High productivity of fucoxanthin and eicosapentaenoic acid in a marine diatom Chaetoceros gracilis by perfusion culture under high irradiance

For a high production rate of microalgae, a high-cell-density culture is an effective strategy for reducing the light intensity per dry weight in the culture to avoid photoinhibition under high light conditions. However, under high cell density microalgae are exposed to nutrient-deficient conditions, resulting in a reduced biomass production rate. To enhance the production rate of high-value bioactives such as fucoxanthin and eicosatetraenoic acid (EPA) by the diatom Chaetoceros gracilis, a perfusion culture was operated at harvesting rates of 10–40 % under light intensities of 300–2000 μmol m−2 s−1. At a harvesting rate of 20 % under a high light intensity of 2000 μmol m−2 s−1, the dry weight increased, and the areal productivity reached 15.6 ± 1.3 g-dry weight (dw) m−2 d−1, which is comparable to the maximum value previously reported in diatoms. The high biomass production, even at a low harvesting rate of 20 %, could result from sufficient nutrient supply by perfusion culture. At a harvesting rate of 20 %, the EPA areal productivity achieved 183 mg-dw m−2 d−1 even under 2000 μmol m−2 s−1 due to the increase in the dry weight using the perfusion culture. However, the fucoxanthin content decreased under 2000 μmol m−2 s−1. A strong relationship was observed between the specific light intensity per dry weight and fucoxanthin content in C. gracilis. This relationship indicates that the fucoxanthin content does not increase unless the specific light intensity per dry weight is adjusted below 20 μmol g-dw−1 s−1. Thus, perfusion culture proved to be useful to control the biomass-specific light intensity for the effective production of EPA and fucoxanthin in C. gracilis under high light conditions expected for outdoor culture.

A closed-loop approach for enhanced biodiesel recovery from rapeseed biodiesel-based byproducts through integrated glycerol recycling by black soldier fly larvae

The present study evaluated an innovative zero-waste approach for efficient recycling of byproducts from rapeseed-based biodiesel industry including lipid-free rapeseed cake (RSC) and waste glycerol by black soldier fly larvae (BSFL). RSC showed high organic matter and protein contents of 92.7 dw% and 32.1 dw%, respectively. Therefore, it was utilized as the main feed source for BSFL rearing, while waste glycerol was supplemented at different concentrations (0–10%, w/w). Application of 5.0% waste glycerol significantly enhanced larval biomass gain rate and areal productivity by 13.0% and 17.2%, respectively, over the control. Interestingly, lipid content also increased by 25.9% over the control. The study suggested a synergistic action in the mixture, where RSC is digested to achieve the growth and development, while waste glycerol can be integrated directly into fatty acid biosynthesis pathway to accumulate lipids. In addition to being a carbon source, morphological examination and FTIR analysis showed that waste glycerol has the potential to penetrate RSC biomass fibers easing its decomposition. Overall, the highest recorded fatty acid methyl esters (FAMEs) productivity of 98.0 mg m−2 was recorded in BSFL treated with 5.0% waste glycerol, which represented 57.7% higher than the control. Comparing to rapeseed biodiesel, saturated fatty acids proportion in the BSFL-based FAMEs at all studied treatments was much higher, leading to 11.9–12.9% higher cetane number. In conclusion, findings of this study provide new insights to BSFL as a promising mini-livestock for biodiesel production through innovative recirculation route of biodiesel byproducts towards waste reduction and sustainable development.

Energy-saving in fucoxanthin production by Chaetoceros gracilis in a flat-bag photobioreactor with intermittent mixing

To save energy in the production of high-value products with antioxidant properties such as fucoxanthin by Chaetoceros gracilis, the effect of mixing frequency (once every 18 min and once every 9 min) on fucoxanthin productivity was examined using a flat bag photobioreactor. The mixing frequency of once every 9 min resulted in a significantly higher (p < 0.01) areal fucoxanthin productivity of 28.9 mg m−2 d−1 than mixing once every 18 min (13.7 mg m−2 d−1). The fucoxanthin productivity at the mixing frequency of once every 9 min was comparable to that in previous studies of diatoms cultured using continuous mixing. Moreover, intermittent mixing reduced the energy required for mixing and biomass productivity per mixing energy of 20.5-21.2 g-DW kWh−1 d−1 was achieved. The present study showed that mixing frequency affected the cell density and light intensity per dry weight of C. gracilis which means the light intensity received by individual cells. The fucoxanthin content increased exponentially with decreasing light intensity per dry weight due to the decrease of the light intensity received by individual cells. Thus, mixing frequency is an essential parameter for high fucoxanthin productivity. Light intensity per dry weight and mixing frequency should be considered in combination to achieve energy savings in fucoxanthin production by C. gracilis.

A streamlined approach to characterize microalgae strains for biomass productivity under dynamic climate simulation conditions

Screening microalgae strains under static light and temperature flask conditions cannot directly quantify the biomass productivities of algae growing in the dynamically fluctuating light and temperature conditions of outdoor ponds. In this effort, we describe a testing pipeline that screens for productivity under climate simulated conditions. A validated, miniaturized Laboratory Environmental Algae Pond Simulator (mini-LEAPS) photobioreactor was used to determine optimal medium salinities and biomass productivities of cold-tolerant microalgae collected from Arctic, subarctic, Antarctic, and subalpine habitats. Strains characterized in this effort include: Chlorella antarctica UTEX1959, Chlorella sp. UTEXSNO69, Chloromonas rosae UTEXSNO11, Phaeodactylum tricornutum UTEX646, and Stichococcus minutus CCALA727. Observed productivities of the characterized strains ranged from 1.74 ± 0.25 to 8.18 ± 0.81 g m−2 day−1 (as ash-free dry weight). For each strain, a temperature tolerance profile was generated to identify the most appropriate season (s) for cultivation. The two most promising strains, Chlorella sp. UTEX SNO69 and P. tricornutum UTEX646, were tested alongside the DISCOVR winter benchmark strain Monoraphidium minutum 26B-AM in outdoor open ponds at the PNNL Algae Testbed (PAT) in Arizona. Under cold-season outdoor pond conditions, Chlorella sp. UTEXSNO69 achieved average areal biomass productivities of 8.21 ± 0.50 g m−2 day−1, not significantly different from that of the benchmark strain (8.52 ± 0.43 g m−2 day−1, p > 0.05). Under spring outdoor pond conditions, P. tricornutum UTEX646 achieved average areal biomass productivities 10.34 ± 0.27 g m−2 day−1, not significantly different from that of the benchmark (10.07 ± 0.50 g m−2 day−1) under the tested conditions (p > 0.05). The streamlined pipeline was thus demonstrated to successfully characterize productive microalgae strains for outdoor deployment by weeding out algae strains that were not productive under the tested dynamic light and temperature conditions.

Nutrient recovery in cultured meat systems: Impacts on cost and sustainability metrics.

A growing global meat demand requires a decrease in the environmental impacts of meat production. Cultured meat (CM) can potentially address multiple challenges facing animal agriculture, including those related to animal welfare and environmental impacts, but existing cost analyses suggest it is hard for CM to match the relatively low costs of conventionally produced meat. This study analyzes literature reports to contextualize CM's protein and calorie use efficiencies, comparing CM to animal meat products' feed conversion ratios, areal productivities, and nitrogen management. Our analyses show that CM has greater protein and energy areal productivities than conventional meat products, and that waste nitrogen from spent media is critical to CM surpassing the nitrogen use efficiency of meat produced in swine and broiler land-applied manure systems. The CM nutrient management costs, arising from wastewater treatment and land application, are estimated to be more expensive than in conventional meat production. Overall, this study demonstrates that nitrogen management will be a key aspect of sustainability in CM production, as it is in conventional meat systems.