Jatropha Curcas Biodiesel: A Lucrative Recipe for Pakistan’s Energy Sector

The effect of high altitude environment on diesel engine performance: Comparison of engine operations in Hangzhou, Kunming and Lhasa cities

The all-area operating performance of the vehicles requires the development of diesel engines that can operate at high altitudes without significant performance deterioration. Prior to optimizing the efficiency and emissions of highland engines, there is a necessity to investigate the underlying causes of engine performance degradation. The purpose of this paper was to study the in-cylinder activities occurring in the combustion chamber of diesel engines at high altitudes, which can help explain the effect of altitude on engine efficiency and emissions of concern to the customer. Specifically, a turbocharged direct injection compression ignition engine was operated at a constant engine speed and load, but at different altitudes. The theoretical analyses based on experimental data suggested that the mismatch between air and diesel quantities caused by the high altitude atmosphere led to the engine combustion deterioration. Specifically, the lower gas density at high altitudes during fuel injection resulted in a reduction of the injection angle and an enhancement of the penetration capability. In addition, the rise in altitude extended the ignition delay, which increased the fuel fraction mixed with air in the premixed combustion stage and raised the pressure rise rate. Moreover, at high altitudes, the reduction in excess air ratio and increased possibility of wall impingement of the fuel droplets resulted in uneven mixture concentration distribution and reduced air utility. Accordingly, combustion deterioration occurred in the combustion chamber of the plateau engines, which reduced energy release during main mixing-controlled combustion, lowered combustion efficiency, increased exhaust energy, and raised engine-out incomplete combustion emissions. All these effects resulted in a decrease in engine thermal efficiency of ∼6.5% and an increase in soot emissions of ∼4.2 times from Hangzhou to Lhasa city for the engine and operating conditions investigated in this study. Consequently, engines operating in highland areas need to be optimized in terms of efficiency and emissions.

Bioprocesses for the Biodiesel Production from Waste Oils and Valorization of Glycerol

The environmental context causes the use of renewable energy to increase, with the aim of finding alternatives to fossil-based products such as fuels. Biodiesel, an alternative to diesel, is now a well-developed solution, and its production from renewable resources makes it perfectly suitable in the environmental context. In addition, it is biodegradable, non-toxic and has low greenhouse gas emissions: reduced about 85% compared to diesel. However, the feedstock used to produce biodiesel competes with agriculture and the application of chemical reactions is not advantageous with a “green” process. Therefore, this review focuses only on bioprocesses currently taking an important place in the production of biodiesel and allow high yields, above 90%, and with very few produced impurities. In addition, the use of waste oils as feedstock, which now accounts for 10% of feedstocks used in the production of biodiesel, avoids competition with agriculture. To present a complete life-cycle of oils in this review, a second part will focus on the valorization of the biodiesel by-product, glycerol. About 10% of glycerol is generated during the production of biodiesel, so it should be recovered to high value-added products, always based on bioprocesses. This review will also present existing techniques to extract and purify glycerol. In the end, from the collection of feedstocks to the production of CO2 during the combustion of biodiesel, this review presents the steps using the “greener” possible processes.