Advances of macroalgae biomass for the third generation of bioethanol production

In recent years, utilization of renewable sources for biofuel production is gaining popularity due to growing greenhouse gas(GHG) emissions which causes global warming. There has been a great effort in exploring alternative feedstock for bioethanol production. In this context, the production of third-generation bioethanol from macroalgae has emerged as an alternative feedstock to food crop-based starch and lignocellulosic biomass.This is mainly due to the fast growth rate of macroalgae, no competition with agricultural land, high carbohydrate content and relatively simple processing steps compared to lignocellulosic biomass. This review paper provides an insight of recent innovative approaches for macroalgae bioethanol production, including conventional and advanced hydrolysis process to produce fermentable sugar, various fermentation technologies, economic analysis and life cycle assessment. With the current technology maturity, efficient utilization of macroalgae as sustainable source for bioethanol and other value-added chemicals production could be achieved in the near future.

Optimization and evaluation of reduced graphene oxide hydrogel composite as a demulsifier for heavy crude oil-in-water emulsion

The rising production of produced water from oilfields had been proven to bring detrimental environmental effects.In this study,an efficient,recyclable,and environmental-friendly reduced graphene oxide immobilizedκ-Carrageenan hydrogel composite(κCaGO)was fabricated as an alternative sorbent for crude oil-in-water demulsification.Polyethyleneimine(PEI)was employed to form a stable hydrogel composite.The conditions for the immobilization of graphene oxide(GO)on PEI-modifiedκ-Carrageenan(κC)beads were optimized appropriately.An immobilization yield of 77%was attained at 2%PEI,2 h immobilization activation time,and pH 6.5.Moreover,the synthesizedκCaGO is capable of demulsification with an average demulsification efficiency of 70%.It was found that the demulsification efficiency increases with salinity andκCaGO dosage,and it deteriorates under alkaline condition.These phenomena can be attributed to the interfacial interactions betweenκCaGO and the emulsion.Furthermore,theκCaGO can be recycled to use for up to six cycles without significant leaching and degradation.As such,the synthesizedκCaGO could be further developed as a potential sorbent substitute for the separation of crude oil from produced water.

Application and circular economy prospects of palm oil waste for eco-friendly asphalt pavement industry:A review

During the production of palm oil,a significant amount of waste is generated.However,because of inefficient handling and utilization,these wastes are becoming a larger issue.As a result,one initiative is to use these wastes in the pavement industry as sustainable materials.However,there is still a lack of understanding about the wider incorporation of palm oil waste in asphalt pavement and its performance.This study examines existing literature on the use of various wastes in the pavement industry,including palm oil clinker(POC),palm oil fibre(POF),palm kernel shell(PKS),and palm oil fuel ash(POFA).As a result,this paper presents a systematic review and scientometric investigation of related study publications on many uses of palm oil waste in the asphalt pavement industry and its performance from 2009 to 2022.The VOS viewer application was used to conduct the sciento-metric study analysis.The relationship between interactions detected in co-authored country studies cited sources of co-citation,and the keyword of the co-occurrence and publication source enabled the identification of the research gap.According to the systematic literature review,40%–60% POC can be used to fine aggregate for optimal performance,while 0–100%PKS can be used to replace coarse aggregate.In addition,50%–80% POFA or POC fine(POCF)can be used as a filler replacement,5%–8% POCF or POFA as a bitumen modifier,and 0.3% POF as a stabilizing additive.Furthermore,the study demonstrates that the safety of utilizing wastes with more than 50% CO_(2) emissions can be curtailed with minimal heavy metal leaching and radioactivity levels.The scientometric analysis may encourage researchers to seek out gaps in the literature that will aid in the long-term,multifaceted use of palm oil wastes in the asphalt pavement industry.Furthermore,the study recommends employing and researching the enormous potential of using palm oil waste in the pavement sectors because they are more sustainable and have better performance.However,there are some barriers to using palm oil waste in the asphalt pavement industry,such as a lack of design standards and guidelines,inefficient raw material pro-cessing conversion facilities,and large-scale production equipment.

A comparative study of adsorption behavior of rifampicin,streptomycin,and ibuprofen contaminants from aqueous solutions onto chitosan:Dynamic interactions,kinetics,diffusions,and mechanisms

Adsorptive removal and dynamic interaction of three different pharmaceutical pollutants,namely rifampicin(RIF),streptomycin(STM),and ibuprofen(IBU)onto chitosan were systematically investigated using a batch adsorption technique at different processing parameters.In this study,chitosan was derived from mud-crab shells,as an innovative way to use the waste from marine foods as adsorbents.The kinetics,intraparticle diffusion,mechanism,and thermodynamics of the adsorption were systematically evaluated and analyzed using kinetic models,Boyd mass transfer and WebereMorris intraparticle diffusion models,Langmuir,Freundlich,DubinineRadushkevich,and Temkin isotherm models,and the Gibbs equation.The adsorption isotherm of the larger molecules,RIF and STM,could be explained by the Langmuir isotherm model,in contrast,that of IBU,which is a much smaller molecule,followed the Freundlich isotherm model.The maximum adsorption capacity of RIF,STM,and IBU on chitosan was estimated to be 66.91 mg g^(-1),11.00 mg g^(-1),and 24.21 mg g^(-1),respectively,which are higher compared to those on a variety of agricultural wastes,suggesting that this biopolymer is a potential practical and economical adsorbent to remove the pharmaceutical compounds from wastewater.The adsorption mechanism of the pharmaceutical compounds on chitosan is proposed based on the vibrational spectroscopic analyses,XRD patterns,and DSC thermograms of the biopolymer before and after adsorption process.

Hydrodynamic Performance of Air-Filled Wave Attenuator for Wave Control:Experimental Study

Numerous types of floating breakwaters have been proposed,tested and commercialized in the past decades.The majority of these breakwaters are made of solid bodies;hence,they are relatively bulky and are not readily to be rapidly installed at the targeted sites when immediate wave protection of the coastal and offshore facilities is needed.Furthermore,the application of these hard floating structures at the recreational beaches is rather unlikely due to potential deadly marine traffic collision.To overcome these problems,a flexible air-filled wave attenuator(AFWA)has been developed in the present study.This floating breakwater is made of flexible waterproof membrane materials.The main body consists of a rectangular air-filled prism and is ballasted by sandbags located around the floating module.The objective of this study is to evaluate the wave transmission,wave reflection,energy dissipation,motion responses and mooring forces of the AFWA under the random wave actions using physical modelling.The test model located in a 20 m long wave flume was subjected to a range of wave heights and periods.The wave profiles in the vicinity of the test model were measured using wave probes for determination of wave transmission,reflection and energy loss coefficients.The motion responses in terms of heave,surge and pitch,and wave forces acting on the mooring lines were measured using a motion tracking system and load cells,respectively.The experimental results reveal that the AFWA is effective in attenuating up to 95%in the incoming wave height and has low-wave-reflection properties,which is commendable for floating breakwaters.

Simultaneous harvesting and cell disruption of microalgae using ozone bubbles:optimization and characterization study for biodiesel production

In the present study, ozone was introduced as an alternative approach to harvest and disrupt microalgae cells (Chlorella vulgaris) simultaneously for biodiesel production. At the optimum ozonation conditions (6.14 g·h^(−1) ozone concentration, 30 min ozonation time, 1 L·min^(−1) of ozone flowrate at medium pH of 10 and temperature of 30℃), the sedimentation efficiency of microalgae cells increased significantly from 12.56% to 68.62%. It was observed that the microalgae cells aggregated to form flocs after pretreated with ozone due to the increment of surface charge from −20 to −6.59 mV. Besides, ozone had successfully disrupted the microalgae cells and resulted in efficient lipid extraction, which was 1.9 times higher than the control sample. The extracted microalgae lipid was mainly consisted of methyl palmitate (C16:0), methyl oleate (C18:1) and methyl linolenate (C18:3), making it suitable for biodiesel production. Finally, utilization of recycled culture media after ozonation pre-treatment showed robust growth of microalgae, in which the biomass yield was maintained in the range of 0.796 to 0.879 g ·h^(−1) for 5 cycles of cultivation.

Microwave torrefaction of empty fruit bunch pellet:Simulation and validation of electric field and temperature distribution

Microwave simulation is significant in identifying a reactor design allowing the biomass to be heated and processed evenly.This study integrated the radio frequency and transient heat transfer modules to simulate the microwave distribution and investigated the performance of microwave heating in the cavity.The simulation results were compared with the experimental findings us-ing the finite element analysis software of COMSOL MULTIPHYSICS to predict the temperature profile and electric field of microwave in the biomass(empty fruit bunch pellets).The higher temperature distribution was observed at the bottom and centre section of the empty fruit bunch pellet bed in the reactor,showing the uniqueness of microwave heating.According to the simula-tion results,the temperature profile obtained through the specific cavity geometry and dielectric properties agreed with the experimental temperature profile.The simulated temperature profile demonstrated a logarithmic increase of 120°C/min at the first 50 s followed by 50°C/min until 350 s.The experimental temperature profile showed three different heating rates before reaching 300°C,including 78.3°C/min(50-120°C),30.6°C/min(121-250°C),and 105°C/min(250-300°C).The results of this study might contribute to the improvement of microwave heating in biomass torrefaction.