Zularisam Ab Wahid

Plant-driven removal of heavy metals from soil: uptake, translocation, tolerance mechanism, challenges, and future perspectives

Increasing heavy metal (HM) concentrations in the soil have become a significant problem in the modern industrialized world due to several anthropogenic activities. Heavy metals (HMs) are non-biodegradable and have long biological half lives; thus, once entered in food chain, their concentrations keep on increasing through biomagnification. The increased concentrations of heavy metals ultimately pose threat on human life also. The one captivating solution for this problem is to use green plants for HM removal from soil and render it harmless and reusable. Although this green technology called phytoremediation has many advantages over conventional methods of HM removal from soils, there are also many challenges that need to be addressed before making this technique practically feasible and useful on a large scale. In this review, we discuss the mechanisms of HM uptake, transport, and plant tolerance mechanisms to cope with increased HM concentrations. This review article also comprehensively discusses the advantages, major challenges, and future perspectives of phytoremediation of heavy metals from the soil.

Technical difficulties and solutions of direct transesterification process of microbial oil for biodiesel synthesis

Microbial oils are considered as alternative to vegetable oils or animal fats as biodiesel feedstock. Microalgae and oleaginous yeast are the main candidates of microbial oil producers’ community. However, biodiesel synthesis from these sources is associated with high cost and process complexity. The traditional transesterification method includes several steps such as biomass drying, cell disruption, oil extraction and solvent recovery. Therefore, direct transesterification or in situ transesterification, which combines all the steps in a single reactor, has been suggested to make the process cost effective. Nevertheless, the process is not applicable for large-scale biodiesel production having some difficulties such as high water content of biomass that makes the reaction rate slower and hurdles of cell disruption makes the efficiency of oil extraction lower. Additionally, it requires high heating energy in the solvent extraction and recovery stage. To resolve these difficulties, this review suggests the application of antimicrobial peptides and high electric fields to foster the microbial cell wall disruption.

Financial sustainability of biogas technology: Barriers, opportunities, and solutions

ABSTRACT Biogas technology, which converts biological waste into energy, is considered as an excellent tool to improve the lives, livelihoods, health, and ecosystem. The demand and prospect of biogas technology as a renewable energy source in terms of market value have not been adequately addressed, although it offers a large revenue opportunity that supports the socioeconomic development in rural areas. For more sustainable development of this technology, policy-makers should reform the existing institutional framework by reorganizing subsidies, motivating and attracting investors with flexible financial conditions, liberalizing the management of gas grids, and involving farmers in local projects. Therefore, it is a great challenge to find a proper mode of marketing policy, business models, and multi-profit options and a sustainable financing mechanism. This paper covers the state-of-the-art enlargements and future consequences of the hastily emerging biogas market, starting with a universal viewpoint and going through special market characteristics of Europe, USA, Africa, and Asia Pacific.

Role of Microorganisms in Microbial Fuel Cells for Bioelectricity Production

The catalytic microorganisms oxidise the organic matter to produce electrical energy in microbial fuel cells (MFCs). The microorganisms that can shuttle the electrons exogenously to the electrode surface without utilising artificial mediators are referred as exoelectrogens. The microorganisms produce specific proteins or genes for their inevitable performance towards electricity generation in MFCs. Multiple studies have confirmed the expression of certain genes for outer membrane multiheme cytochromes (e.g. OmcZ), redox-active compounds (e.g. pyocyanin), conductive pili, and their potential roles in the exoelectrogenic activity of various microorganisms, particularly in the members of Geobacteraceae and Shewanellaceae family. This chapter explores the various mechanisms of microorganisms that are advantageous for the technology: biofilm formation, metabolism, electron transfer mechanisms from inside the microorganisms to the electrodes and vice versa.

Novel mesoporous MnCo 2 O 4 nanorods as oxygen reduction catalyst at neutral pH in microbial fuel cells

The aim of this work was to evaluate the comparative performance of hybrid metal oxide nanorods i.e. MnCo2O4 nanorods (MCON) and single metal oxide nanorods i.e. Co3O4 nanorods (CON) as oxygen reduction catalyst in microbial fuel cells (MFC). Compared to the single metal oxide, the hybrid MCON exhibited a higher BET surface area and provided additional positively charged ions, i.e., Co2+/Co3+ and Mn3+/Mn4+ on its surfaces, which increased the electro-conductivity of the cathode and improved the oxygen reduction kinetics significantly, achieved an io of 6.01 A/m2 that was 12.4% higher than CON. Moreover, the porous architecture of MCON facilitated the diffusion of electrolyte, reactants and electrons during the oxygen reduction, suggested by lower diffusion (Rd), activation (Ract) and ohmic resistance (Rohm) values. This enhanced oxygen reduction by MCON boosted the power generation in MFC, achieving a maximum power density of 587 mW/m2 that was ∼29% higher than CON.

Treatment of Dye Wastewater for Water Reuse Using Membrane Bioreactor and Biofouling Control

Wastewater treatment for water reuse and membrane biofouling control is of significant value to sustainable performance of a membrane bioreactor system. Different treatment techniques have been employed to treat dye wastewater. In recent studies, membrane bioreactor was employed to treat dye wastewater; however, membrane bioreactors are facing biofouling problem. Biofouling (is a process of membrane surface colonization by microbial cells via adhesion and production of extracellular polymeric substances (EPSs)) is almost always a major hitch for membrane bioreactors (MBRs) and membrane systems. Biofouling of membrane reactors results in higher operational expenses and reduced stability and operational performance. In this chapter, biological treatment of membrane biofouling is demonstrated. Furthermore, major causes of biofouling and biological control strategies are discussed. Lastly, conclusions on wastewater treatment and membrane biofouling are presented.

Economic and Market Value of Biogas Technology

The demand and prospect of biogas technology as a renewable energy source in terms of market value have not been adequately addressed. This paper focuses on the status of legal framework and future market situation related to biogas technology in order to facilitate its improvements. Biogas technology, known as biofuel production process through fermentation of biological wastes, is a well-established technique to improve lives, livelihoods, health, and ecosystem. This approach generates a large revenue opportunity that supports the socioeconomic development in rural areas. However, very little initiative has been introduced specially in the developing world to gear up the biogas technology. For more sustainable development of this technology, policy-makers should reform the existing institutional framework by reorganizing subsidies, motivating and attracting investor with flexible financial conditions, liberalizing the management of gas grids, and involving farmers in local projects. Therefore, it is a great challenge to find a proper mode of marketing policy, business models and multi-profit options, and a sustainable financing mechanism. This paper covers the state-of-the-art enlargements and future consequences of the hastily emerging biogas market, starting with a universal viewpoint and going through the market characteristics of Europe, the USA, Africa, and Asia Pacific.