Samson Mekbib Atnaw

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.

The Study of Temperature Profile and Syngas Flare in Co-gasification of Biomass Feedstock in Throated Downdraft Gasifier

Biomass gasification is a common technology, which converted solid biomass into gaseous fuel at high temperature reactions in the presence of gasification agent. In this paper, co-gasification of lignocellulosic biomass materials with oil palm fronds (OPF) in a downdraft gasifier is presented. The biomass feedstocks considered were sugar cane bagasse (SCB) and wood (acacia mangium). Only one material was co-gasified with OPF at a time, with blending ratios of 80:20, 50:50 and 20:80. The resulting temperature profiles in the reactor and the syngas flare duration were recorded. It was found that the blend of 80:20 wood and OPF gave the best result as it produced the longest steady flare duration (49.5 min). On the other hand, a significant bridging problem was observed in the co-gasification OPF and SCB, and thus implying the need for process improvement.

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.

Optimization of hybrid electric vehicle control for efficient performance at critical energy levels

This paper proposes an optimization algorithm to regulate energy consumption and powertrain control of a hybrid electric vehicle (HEV). The algorithm is applied on a prototype vehicle manufactured by adding an electric motor to an all-terrain vehicle (ATV). The control system is designed using an embedded micro-controller unit (MCU). The main targets in this study are to improve the electric energy consumption efficiency and to reduce the ICE usage to minimum. The MCU controls the automatic switching between the electric motor and the internal combustion engine of the ATV. Furthermore, the system gives guidance for driver to use the limited resource efficiently at critical energy level. It restricts the driver performance using pulse width modulation (PWM). PWM duty cycle is adjusted to get optimum performance in term of maximizing the travel distance. Various driving scenarios are analyzed in this study. Factors such travel speed, energy level, stop-and-go frequency have been taken into consideration. The experiments showed significant improvement.

Modeling Energy Efficiency As A Green Logistics Component In Vehicle Assembly Line

This paper uses System Dynamics (SD) simulation to investigate the concept green logistics in terms of energy efficiency in automotive industry. The car manufacturing industry is considered to be one of the highest energy consuming industries. An efficient decision making model is proposed that capture the impacts of strategic decisions on energy consumption and environmental sustainability. The sources of energy considered in this research are electricity and fuel; which are the two main types of energy sources used in a typical vehicle assembly plant. The model depicts the performance measurement for process- specific energy measures of painting, welding, and assembling processes. SD is the chosen simulation method and the main green logistics issues considered are Carbon Dioxide (CO2) emission and energy utilization. The model will assist decision makers acquire an in-depth understanding of relationship between high level planning and low level operation activities on production, environmental impacts and costs associated. The results of the SD model signify the existence of positive trade-offs between green practices of energy efficiency and the reduction of CO2 emission.

Improving Energy Efficiency for the Vehicle Assembly Industry: A Discrete Event Simulation Approach

This paper presented a Discrete Event Simulation (DES) model for investigating and improving energy efficiency in vehicle assembly line. The car manufacturing industry is one of the highest energy consuming industries. Using Rockwell Arena DES package; a detailed model was constructed for an actual vehicle assembly plant. The sources of energy considered in this research are electricity and fuel; which are the two main types of energy sources used in a typical vehicle assembly plant. The model depicts the performance measurement for process- specific energy measures of painting, welding, and assembling processes. Sound energy efficiency model within this industry has two-fold advantage: reducing CO2 emission and cost reduction associated with fuel and electricity consumption. The paper starts with an overview of challenges in energy consumption within the facilities of automotive assembly line and highlights the parameters for energy efficiency. The results of the simulation model indicated improvements for energy saving objectives and reduced costs.

Study on co-gasification of oil palm fronds and wood

Over the decade, gasification experiment on different biomass materials has been carried out to investigate the biomass potential as one of the alternative sources of fuel. Although gasification has been proven to be successful in bringing out the potential of different biomass fuels, it commonly involves conversion of only one type of biomass materials for a single run. This paper discusses the co-gasification experiment of different composition of oil palm fronds (OPF) and wood using a downdraft gasifier. The conducted study focuses on the temperature profile within the reactor and also the characteristic of the dynamic temperature profile in each zone within the gasifier reactor. The temperature profile in the drying, pyrolysis, oxidation and reduction zone of the reactor was experimentally investigated. Effect of bridging on the temperature profile is also observed. The temperature profiles obtained are compared with literature result. In addition, syngas production was monitored by observing the flare produced during the operation. However, further experiment need to be done to investigate the composition of syngas produced during the co-gasification experiment.