Advances in sustainable approaches to recover metals from e-waste-A review

Electronic waste collection systems using Internet of Things (IoT): Household electronic waste management in Malaysia

Economic performance of pyrolysis of mixed plastic waste : open-loop versus closed-loop recycling

Microalgae as a solution of third world energy crisis for biofuels production from wastewater toward carbon neutrality: An updated review

Microalgae as a solution of third world energy crisis for biofuels production from wastewater toward carbon neutrality: An updated review.

An analysis of electronic waste management strategies and recycling operations in Malaysia: Challenges and future prospects

Anthropogenic CO2 emissions are the main contributors to climate change. Among the various efforts to reduce atmospheric CO2 levels, cultivation of microalgae is the most promising approach owing to its high photosynthetic rates and CO2 fixation efficiencies than terrestrial counterparts. However, the accurate quantification method of CO2 fixation during the cultivation of microalgae in photobioreactors (PBRs) is lacking. Present methods for the determination of CO2 fixation during microalgae cultivation include direct and indirect methods, where 79% of direct method studies of the bibliometric analysis compared to 21% of indirect method studies. Direct methods evaluate the carbon content in microalgae biomass using assumptive values, though it results in significant errors as high as 50% in quantifying the CO2 fixation. This can be improved by measuring the carbon contents using elemental and total organic carbon analysis. On the other hand, indirect methods quantify CO2 concentration at inlet and outlet of PBRs by using gas chromatography or infrared sensors. It is rather difficult to validate the accuracy of direct and indirect methods due to the lack of comparative works and analysis among the methods. Additionally, there are no current studies that provide in-depth discussion and perspectives on the CO2 fixation methods. Therefore, the main aim of this critical review is to analyse, contrast and discuss the differences as well as inaccuracies of direct and indirect microalgae CO2 fixation quantifications in PBRs. This is followed by the recommendations for further improvements, and standard guidance for future studies in applying appropriate CO2 fixation quantification methods.

Analysis of direct and indirect quantification methods of CO2 fixation via microalgae cultivation in photobioreactors: A critical review

Anthropogenic emissions like carbon dioxide (CO 2 ) necessitate the need for immediate mitigation of excessive CO 2 concentrations, so as to ease the impacts of climate change. Mass carbon capture and storage (CCS) via microalgae cultivations have been proven prominent for their CO 2 capturing abilities and prospects of converting CO 2 into commercially valuable bioproducts. However, current microalgae cultivation systems have yet to achieve the satisfactory production rates required for mass CCS. To improve microalgae growth, CO 2 gas bubbles are often fed to sustain microalgae cultures in photobioreactors (PBRs). Studies have shown significant increases in microalgae growth and CO 2 capturing rates with the reduction of gas bubble sizes to micro-size. In this work, 3 distinct gas spargers were designed, and their mixing performances were investigated in a 10 L flat-panel PBR. Detailed analysis of micro-size bubbles generation via gas spargers, along with the cost analysis and carbon tax estimations for the sparger designs and operations, were discussed. The results of this work showed that spargers with micro-size pores were not able to produce micro-size bubbles. The customised sintered metal spargers with novel double sparger orientation resulted in higher mixing performances, compared to perforated spargers and commercial spargers. Findings advance the understanding of mixing and CO 2 mass transfer, important milestones for photobioreactor scale-up studies and partly fulfil the circular bioeconomy concept where microalgae cultivations address both environmental and economic aspects. • Pipe spargers with micro-size pores failed to produce micro-size bubbles. • Customised sintered metal spargers provided better mixing performances. • CO 2 mass transfer was insignificant for customised sparger of different pore sizes. • Low-cost aquarium commercial sparger provided consistent mixing performance. 

Improving microalgae growth and carbon capture through micro-size bubbles generation in flat-panel photobioreactors: Impacts of different gas sparger designs on mixing performance

Yi An Lim

Papers

An analysis of electronic waste management strategies and recycling operations in Malaysia: Challenges and future prospects

Analysis of direct and indirect quantification methods of CO2 fixation via microalgae cultivation in photobioreactors: A critical review

Improving microalgae growth and carbon capture through micro-size bubbles generation in flat-panel photobioreactors: Impacts of different gas sparger designs on mixing performance