Emma Suali

Membrane Photobioreactor as a Device to Increase CO2 Mitigation by Microalgae

The integration of a membrane contactor with a photobioreactor serves two major purposes for the mitigation of CO2 by microalgae, i.e., to enhance the mass transfer and interfacial contact between two different phases and to increase the exchange process of CO2–O2 by microalgae in the photobioreactor. The membrane integrated with a photobioreactor for CO2 mitigation by microalgae can be considered as a relatively new field, and only four or five related research efforts have been published in the literature, suggesting that a significant amount of work remains to be done in this field. In addition, all of the authors agreed that a membrane contactor is capable of achieving better mass transfer than the conventional approach of using a separation column in the gas–liquid separation process. One significant problem associated with using a membrane as a CO2–O2 gas exchanger is its susceptibility to pore fouling due to the micron-size cells of the microalgae. However, pore fouling can be prevented by using a hydrophobic membrane contactor and appropriate operating conditions, both of which are discussed in detail in this work.

Potential use of carbon dioxide by microalgae in Malaysia.

CO2 emission, which is feared to bring more harm than benefit to the environment, can be prevented and reduced through the cultivation of microalgae. Microalga is the fastest growing organism (estimated 40 times faster than terrestrial grass) and requires a high CO2 concentration to reproduce. Thus, this work evaluates the potential of microalgae to utilise CO2. The tolerable concentration of CO2 for high microalgae productivity as a biomass producer is also explored. High productivity of microalgae is the key to successful biofuel productions, that is, not only producing green energy but also preventing the release of CO2 into the atmosphere. Because of this concern, microalgae potential as a double-benefit for green energy production is analysed and discussed considering a CO2 emissions scenario in Malaysia.

Membrane Processes for Microalgae in Carbonation and Wastewater Treatment

The objective of this work is to present the integration of membrane processes in the field of bioenergy resource and wastewater treatment using microalgae. There are two main processes involved: carbonation and separation, which were conducted and reported as a separated work within this chapter. The chapter begins with the introduction of membrane processes, followed by carbonation of microalgae and separation of biomass from the wastewater effluent. The experimental work on the carbonation aims to evaluate the effectiveness of hydrophobic hollow fibre membrane in transporting CO2 into microalgae culture and microalgae accumulation within the membrane. The experimental work on the separation process of microalgae biomass from the wastewater effluent on the other hand, aims to evaluate Ultrafiltration (UF) membrane capability in removing BOD and COD as well as its ability to retain microalgae biomass which were used by the turbidity reading of the membrane permeate. The application of hydrophobic membrane in the carbonation process has increased the carbonation efficiency up to 83 % in comparison with the carbonation without membrane and only a small amount of mirage was accumulated within the membrane. The experimental result also shows that, the carbonised microalgae can be further used for wastewater treatment. Based on the result of separation process of microalgae biomass of wastewater effluent, the UF membrane utilization shows high separation efficiency in turbidity to lower than 5 Fau, and was able to facilitate in nutrient removal for less time required compared to the biological treatment without application of the membrane.

Polishing of POME by Chlorella sp. in suspended and immobilized system

The effect of using suspended and immobilized growth of Chlorella sp. to treat POME was studied. Cotton and nylon ropes were used as the immobilization material in a rotating microalgae biofilm reactor. The result showed that POME treated in suspended growth system was able to remove 81.9% and 55.5% of the total nitrogen (TN) and total phosphorus (TP) respectively. Whereas the immobilized system showed lower removal of 77.22% and 53.02% for TN and TP. Lower performance of immobilized microalgae is due to the limited light penetration and supply of CO2 inside the immobilization materials. The rotating microalgae biofilm reactor was able to reduce the biochemical oxygen demand (BOD) to 90 mg/L and chemical oxygen demand (COD) to 720 mg/L. Higher BOD and COD reading were obtained in suspended growth due to the presence of small number of microalgae cell in the samples. This study shows that suspended growth system is able to remove higher percentages of nitrogen and phosphorus. However, an efficient separation method such as membrane filtration is required to harvest the cultivated microalgae cell to avoid organic matter release into water bodies.

Correlation study of microalgae carbonation in membrane integrated photobioreactor

Microalgae ability to utilise CO2 higher compared to terrestrial plant making it suitable for biomass production and as CO2 utiliser. This could be one of many ways to preserve a safer and healthier environment with less air pollutant. For study purposes, CO2 usually transported to microalgae culture broth with the aid of membrane technology to prevent formation of large bubble and to accelerate the carbonation of microalgal media. However, membrane susceptible to accumulation of CO2, which can cause extreme acidic to microalgal media. This prevents microalgae to assimilate CO2. Thus, this study proposes correlations to prevent the extreme acidic: which represents the relationship of: (1) CO2 inlet and accumulation, (2) CO2 inlet and CO2 at the membrane-liquid interphase and (3) CO2 inlet and CO2 solubility in the media. The correlations were successfully validated with a deviation of less than 20% compared to the theoretical value.

Synthesis and characterization of metal oxide promoted alumina catalyst for biofuel production

Alumina has been widely used as a support in catalysis process which owing to its extremely thermal and mechanical stability, high surface area, large pore size and pore volume. The aim of this study was to synthesize calcium oxide-supported basic alumina catalysts (CaO/Al2O3) by impregnation method and to characterize the properties of the catalyst based on its surface area and porosity, functional group, surface morphology and particle size. Impregnation method was chosen for the synthesization of catalyst which involved contacting the support with the impregnating solution for a particular period of time, drying the support to remove the imbibed liquid and calcination process. In the preparation of catalyst, catalytic performance of CaO/Al2O3 catalyst was measured at different calcined temperatures (650°C, 750°C and 800°C). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Mercury intrusion porosimetry (MIP), and particle size analyzer (Zetasizer) was used to characterize the catalyst. The highest total specific area and the total porosity of the catalyst was obtained at 750oC. FTIR analysis basically studied on the functional groups present in each catalyst synthesized, while SEM analysis was observed to have pores on its surface. Moreover, CaO/Al2O3 catalysts at 650°C produced the smallest particle size (396.1 mn), while at 750°C produced the largest particle size (712.4 mn). Thus it can be concluded that CaO/Al2O3 catalysts has great potential coimnercialization since CaO has attracted many attentions compared to other alkali earth metal oxides especially on the transesterification reaction.