Microalgae has been identified as a potential feedstock for biodiesel production since its cultivation requires less cropland compared to conventional oil crops and the high growth rate of ...microalgae. Research on microalgae oils often are focused on microalgae oil extraction and biomass harvesting techniques. However, energy intensive and costly lipid extraction methods are the major obstacles hampering microalgae biodiesel commercialisation. Direct biodiesel synthesis avoids such problems as it combines lipid extraction techniques and transesterification into a single step. In this review, the potential of direct biodiesel synthesis from microalgae biomass was comprehensively analysed. The various species of microalgae commonly used as biodiesel feedstock was critically assessed, particularly on high lipid content species. The production of microalgae biodiesel via direct conversion from biomass was systematically discussed, covering major enhancements such as heterogeneous catalysts, the use of ultrasonic and microwave- techniques and supercritical alcohols that focus on the overall improvement of biodiesel production. In addition, this review illustrates the cultivation conditions for biomass growth and lipid productivity improvement, the available harvesting and lipid extraction technologies, as well as the key challenges and future prospect of microalgae biodiesel production. This review serves as a basis for future research on direct biodiesel synthesis from modified microalgae biomass to improve profitability of microalgae biodiesel.
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•Microalgae lipid enhancement techniques were compared.•Harvesting and extraction technologies were evaluated.•Factors impacting direct biodiesel synthesis were discussed.•Challenges and prospects for microalgae industrial application were proposed.
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•Conventional and newly developed methods for algal biochar synthesis are discussed.•Characterization of algal biochar is presented to justify its application range.•Future directions ...on the development of algal biochar technologies are proposed.
Algal biomass is known as a promising sustainable feedstock for the production of biofuels and other valuable products. However, since last decade, massive amount of interests have turned to converting algal biomass into biochar. Due to their high nutrient content and ion-exchange capacity, algal biochars can be used as soil amendment for agriculture purposes or adsorbents in wastewater treatment for the removal of organic or inorganic pollutants. This review describes the conventional (e.g., slow and microwave-assisted pyrolysis) and newly developed (e.g., hydrothermal carbonization and torrefaction) methods used for the synthesis of algae-based biochars. The characterization of algal biochar and a comparison between algal biochar with biochar produced from other feedstocks are also presented. This review aims to provide updated information on the development of algal biochar in terms of the production methods and the characterization of its physical and chemical properties to justify and to expand their potential applications.
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•Microalgal biomass from wastewater treatment can be used for biochar production.•MPBR is applicable in microalgae cultivation and wastewater treatment.•Pyrolysis can be a suitable ...process in biochar production.•Optimization process in conversion of microalgal biomass to biochar is suggested.
Microalgae have received increasing attentions due to its capacity of carbon fixation and serving as feedstock for producing biofuels and other value-added products. Microalgae can be used to remediate wastewater for simultaneously nutrient removal and biomass production, thereby significantly lowering the costs of microalgal feedstock. Recently, converting microalgal biomass biochar is of particular interest since biochar has numerous opportunities in application. In this review, innovative methods developed for microalgae-based wastewater treatment are described. Conventional and novel technologies used for producing biochar from microalgal biomass, such as pyrolysis and hydrothermal approaches, are presented. Future challenges and potential applications of the biochar derived from microalgal biomass collected from wastewater treatment system (e.g., soil amendment or adsorbent) are also discussed.
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•Torrefaction is a promising conversion method in upgrading microalgal biomass.•Wet torrefaction is a recent technology to improve HHV of wet microalgal biomass.•Torrefied microalgae ...shows an applicable approach in solid fuel application.•Microalgal biochar has unique properties suitable for bio-adsorbent application.
Microalgal biomass is the third-generation promising feedstock for production of biofuel and other valuable goods. The raw microalgal biomass and residues have low calorific value, high moisture, and high H/C and O/C atomic ratio which not suitable to use as solid fuel and many engineering applications. Torrefaction is a promising technique to upgrade microalgal biomass closed to solid coal properties by increasing the calorific value of microalgal biochar. However, the overview of torrefaction process for microalgal biochar is lacking in the literature study. Thus, an overview of recent dry and wet torrefaction of microalgal biomass is presented in this review. Wet torrefaction is a new technology for microalgal biochar production because it has some advantages compare with other pre-treatment methods. Besides, this review aims to provide a comprehensive overview of recent research for fuel property of microalgal biochar after torrefaction process. Different torrefaction temperature, gases and holding time lead to various solid yield, energy yield and calorific value of biochar are comprehensively discussed. In addition, the used of microalgal biochar as bio-adsorbent to remove pollutants in wastewater are included as well. In short, this is a comprehensive summary of recent torrefaction technology for microalgal biochar as fuel.
This research aims to study the wet torrefaction (WT) and saccharification of sorghum distillery residue (SDR) towards hydrochar and bioethanol production. The experiments are designed by Box-Behnken ...design from response surface methodology where the operating conditions include sulfuric acid concentration (0, 0.01, and 0.02 M), amyloglucosidase concentration (36, 51, and 66 IU), and saccharification time (120, 180, and 240 min). Compared to conventional dry torrefaction, the hydrochar yield is between 13.24 and 14.73%, which is much lower than dry torrefaction biochar (yield >50%). The calorific value of the raw SDR is 17.15 MJ/kg, which is significantly enhanced to 22.36–23.37 MJ/kg after WT. When the sulfuric acid concentration increases from 0 to 0.02 M, the glucose concentration in the product increases from 5.59 g/L to 13.05 g/L. The prediction of analysis of variance suggests that the best combination to maximum glucose production is 0.02 M H2SO4, 66 IU enzyme concentration, and 120 min saccharification time, and the glucose concentration is 30.85 g/L. The maximum bioethanol concentration of 19.21 g/L is obtained, which is higher than those from wheat straw (18.1 g/L) and sweet sorghum residue (16.2 g/L). A large amount of SDR is generated in the kaoliang liquor production process, which may cause environmental problems if it is not appropriately treated. This study fulfills SDR valorization for hydrochar and bioenergy to lower environmental pollution and even achieve a circular economy.
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•Both hydrochar and bioethanol are produced from sorghum distillery residue (SDR).•The maximum bioethanol concentration from dilute acid pretreatment is 19.21 g/L.•The minimum solid yield from wet torrefaction (WT) is 13.24%.•The maximum higher heating value (HHV) of hydrochar is 23.37 MJ/kg.•WT can increase the HHV of SDR by up to 36.27%.
The main finding of the work: Bioethanol and hydrochar produced from sorghum distillery residue with low-concentration sulfuric acid concentrations are achieved, which can mitigate environmental pollution.
Microalgae cultivation and biomass to biochar conversion is a potential approach for global carbon sequestration in microalgal biorefinery. Excessive atmospheric carbon dioxide (CO
2
) is utilized in ...microalgal biomass cultivation for biochar production. In the current study, microalgal biomass productivity was determined using different CO
2
concentrations for biochar production, and the physicochemical properties of microalgal biochar were characterized to determine its potential applications for carbon sequestration and biorefinery. The indigenous microalga
Chlorella vulgaris
FSP-E was cultivated in photobioreactors under controlled environment with different CO
2
gas concentrations as the sole carbon source. Microalgal biomass pyrolysis was performed thereafter in a fixed-bed reactor to produce biochar and other coproducts.
C. vulgaris
FSP-E showed a maximum biomass productivity of 0.87 g L
−1
day
−1
. A biochar yield of 26.9% was obtained from pyrolysis under an optimum temperature of 500 °C at a heating rate of 10 °C min
−1
.
C. vulgaris
FSP-E biochar showed an alkaline pH value of 8.1 with H/C and O/C atomic ratios beneficial for carbon sequestration and soil application. The potential use of microalgal biochar as an alternative coal was also demonstrated by the increased heating value of 23.42 MJ kg
−1
.
C. vulgaris
FSP-E biochar exhibited a surface morphology, thereby suggesting its applicability as a bio-adsorbent. The cultivation of microalgae
C. vulgaris
FSP-E and the production of its respective biochar is a potential approach as clean technology for carbon sequestration and microalgal biorefinery toward a sustainable environment.
The morphotaxonomy of Rhipicephalus microplus complex has been challenged in the last few years and prompted many biologists to adopt a DNA-based method for distinguishing the members of this group. ...In the present study, we used a mitochondrial DNA analysis to characterise the genetic assemblages, population structure and dispersal pattern of R. microplus from Southeast Asia, the region where the species originated.
A phylogeographic analysis inferred from the 16S rRNA and cytochrome oxidase subunit I (COI) genes was performed with five populations of R. microplus collected from cattle in Malaysia. Malaysian R. microplus sequences were compared with existing COI and 16S rRNA haplotypes reported globally in NCBI GenBank.
A total of seven and 12 unique haplotypes were recovered by the 16S rRNA and COI genes, respectively. The concatenated sequences of both 16S rRNA and COI revealed 18 haplotypes. Haplotype network and phylogenetic analyses based on COI+16S rRNA sequences revealed four genetically divergent groups among Malaysian R. microplus. The significantly low genetic differentiation and high gene flow among Malaysian R. microplus populations supports the occurrence of genetic admixture. In a broader context, the 16S rRNA phylogenetic tree assigned all isolates of Malaysian R. microplus into the previously described African/the Americas assemblage. However, the COI phylogenetic tree provides higher resolution of R. microplus with the identification of three main assemblages: clade A sensu Burger et al. (2014) comprises ticks from Southeast Asia, the Americas and China; clade B sensu Burger et al. (2014) is restricted to ticks that originated from China; and clade C sensu Low et al. (2015) is a new genetic assemblage discovered in this study comprising ticks from India and Malaysia.
We conclude that the R. microplus complex consisting of at least five taxa: R. australis, R. annulatus, R. microplus clade A sensu Burger et al. (2014), R. microplus clade B sensu Burger et al. (2014) and the new taxon, R. microplus clade C sensu Low et al. (2015). The use of COI as the standard genetic marker in discerning the genetic assemblages of R. microplus from a broad range of biogeographical regions is proposed.
We present a 2D-stitched, 316MP, 120FPS, high dynamic range CMOS image sensor with 92 CML output ports operating at a cumulative date rate of 515 Gbit/s. The total die size is 9.92 cm × 8.31 cm and ...the chip is fabricated in a 65 nm, 4 metal BSI process with an overall power consumption of 23 W. A 4.3 µm dual-gain pixel has a high and low conversion gain full well of 6600e- and 41,000e-, respectively, with a total high gain temporal noise of 1.8e- achieving a composite dynamic range of 87 dB.
We report, for the first time, a facile, scalable, and cost-effective method for the synthesis of high-performance and monodispersed hexagonally shaped cobalt oxide platelets supported on iron oxides ...(Fe3O4 and α-Fe2O3) as the electrocatalyst systems for water electrolysis. The Fe3O4 was synthesized in the absence of an inert environment and organic solvent, using a modified coprecipitation procedure. Fe3O4 nanoparticles of average size 15 nm served as the best catalyst support for Co3O4, in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). A current density of 10 mA/cm2 was achieved, at −0.36 and 1.64 V for the HER and OER versus reversible hydrogen electrode (RHE), respectively, for the Co3O4/Fe3O4 system, in 0.1 M KOH with low total catalyst loading of 250 μg/cm2 (or 100 μgCo3O4 /cm2). Compared to those using the same total loading of unsupported Co3O4 catalyst, the overpotentials of Co3O4/Fe3O4 catalyst decreased by 0.22 and 0.06 V for the HER and OER, respectively. Despite low nonprecious metal loading, the Co3O4/Fe3O4 system showed high OER kinetics with low Tafel slope of 63 mV/dec. Chronoamperometry tests performed, at 1.62 and −0.30 V for the OER and HER, respectively, on the Co3O4/Fe3O4 catalyst demonstrated extremely stable OER over a period of 8 h. FESEM images of Co3O4/Fe3O4 revealed that the Co3O4 platelets were self-assembled into edge-on orientation on the Fe3O4 support. This largely accounted for the high catalytic activities observed because of the large total exposed surface area of Co3O4/Fe3O4 for catalytic reactions, in addition to electrochemical and morphological effects. Despite negating the need for specially tailored morphologies, Co3O4/Fe3O4 demonstrated enhanced electrochemical performance and stability. This may serve as a cost-effective route to the large-scale commercialization of electrolyzers and fuel cells via facile synthesis of nonprecious metal oxides as the catalyst–support system for enhanced electrochemical water electrolysis.
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