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.

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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.

This paper deals with the energy audit and heat recovery system modeling and design, taking a cement factory in Ethiopia as a case study. The system is a dry type rotary kiln equipped with a sixth stage cyclone type preheater, pre-calciner and grate cooler. The kiln has a capacity of 3,000 tons/day. The energy auditing has been performed based on the data collected from control volume of the kiln system for a ten-month period. The result shows that 25.23% of the total heat input is released to the environment through the preheater and another 15.58% through the cooler exhausts. The west heat recovery system (WHRS) can produce a gross power of 5.26 MW as long as the kiln is in operation. The generated power can cover all the electrical energy consumption of the kiln system whether there is a power supply from the grid or not. Therefore, the company can save up to 536,222.10 USD per year due to the production of clinker using their own power source and avoiding the loss sustained by the company due to power interruption from the grid.