Bioenergy production and nutrients removal by green microalgae with cultivation from agro-wastewater palm oil mill effluent (POME) - A review

Environmental pollution specifically wastewater is gaining attention both in the developed and developing countries. Malaysia is considered as one of the major palm oil producers in the world. Therefore, it is important to develop an environmental friendly and economic method to treat palm oil mill effluent (POME). The wastewater can serve as an economical nutrient source or substrate that can support the cultivation of microalgae. This can be a great nutrient for algal cultivation at the same time as remediating effluent and generating biomass. Nowadays, many microalgae species are being investigated to determine their potential and effectiveness for phytoremediation application, especially high growth rate. However, using synthetic media for growing microalgae in a mass scale is costly. It is acknowledged that POME (as nutrients enriched media) assisted enhanced microalgae growth under certain condition can considerably reduce the presence of organic and inorganic compounds. In this review, the potential of wide range of the predominant microalgae species with main focus on green microalgae (high removal efficiency): Chlamydomonas sp and Chlorella sp were investigated. Moreover, we discussed about the history, methods and future prospects in nutrients removal by green microalgae comprehensively. This review discusses several potential strategies for tackling the environmental issue generated by agro-waste water POME with enhancement of biomass productivity which can be used as an alternative for energy production

A review on the economic feasibility of composting for organic waste management in Asian countries

The rising rate of population growth and industrial development mainly in urban areas have led to significant increase in municipal solid waste (MSW) production. It has been a challenge to materialise a sustainable solid waste management notably in many developing countries. Organic portion represents a significant component in the municipal solid waste across countries with different level of income, ranging from about 25 to 70 %. Composting can be a viable option to manage waste sustainably by transforming waste into value-added fertiliser. Large-scale operation of composting is confronted with concern over feasible economic performance, which varied following different mode of operation. This study aims to review the economic feasibility (EF) on two different composting systems, which are the in-vessel and windrow system, implemented in several developed and developing countries. The review considered the cost factors for both composting systems, including the capital cost and operating cost. The return on investment (ROI) is estimated for both composting systems based on the potential cost benefits from the compost sale and the saving of waste tipping fee. This review provides a better insight into the desirability and applicability of both composting systems as an alternative to the landfilling practice. It is expected that the review of the various composting system could be very useful for improving the sustainable composting technology in the developing countries

Pinch analysis methodology for trigeneration with energy storage system design

Rising energy prices, as well as environmental pollution and depletion of fossil fuel, have increased the need to find alternative energy sources and improve the efficiency of current energy systems. Conventional power plants only use an average thermal efficiency of 30 – 35 % to produce power while the remaining energy is dissipated to the environment. The thermal efficiency can be increased to 80 – 90 % by reusing the waste heat for other applications, such as heating and cooling. A trigeneration system is a technology that can produce power, heating and cooling from a single energy source. Pinch Analysis is a methodology that can help users optimise energy, water and other resources. This paper proposes a novel methodology for developing a Trigeneration Cascade Table (TriGenCT) with energy storage system based on the Pinch Analysis algebraic technique. There are five parts for developing TriGenCT which are data extraction, Single Utility Problem Table Algorithm, Multiple Utility Problem Table Algorithm, Total Site Problem Table Algorithm and TriGenCT with energy storage system. The usage of trigeneration system with storage can save energy up to 202 GWh/y. The development of a TriGenCT with energy storage system can be very useful for engineers and managers to optimize the design of trigeneration systems as well as energy storage systems

Development and optimization of an integrated energy network with centralized and decentralized energy systems using mathematical modelling approach

Decentralized energy generation (DEG) system which characterizes local power generation and utilization are recently getting more attention in energy system planning and implementation because it produces cleaner energy from renewable resources and is capable to avoid significant energy losses during the power transfer from the centralized power plants. These DEGs are however scattered in locations and have intermittent power supply, making it difficult to self-sustain. In this study, a novel integrated energy system consisting of multiple DEGs connected to the existing CEG is proposed. New aspects that are included in the model include the distribution and transmission losses as well as impact of operating load on the heat rate of power plants. Energy storage system were also modelled to operate within the DEG and CEG network. Through a case study demonstration, the capacities of the integrated system were optimized using superstructure-based mixed integer non-linear programming (MINLP) mathematical modelling. The system was also optimized based on economic and energy efficiency to study the effects and trade-off between the two parameters. The results revealed that the optimal system can be obtained with levelized cost of electricity of MYR 0.44/kWh. The result also revealed that biomass and wind energy favours industrial users