Akhilendra K. Pathak

NPK-10:26:26 complex fertilizer assisted optimal cultivation of Dunaliella tertiolecta using response surface methodology and genetic algorithm.

A culture medium based on NPK-10:26:26 fertilizer was formulated for enhanced biomass and lipid production of Dunaliella tertiolecta by selecting appropriate nutrients and environmental parameters. Five-level-five-factor central composite design assisted response surface methodology was adopted for optimal cultivation of D. tertiolecta and results were compared with simple genetic algorithm (GA). Significant improvement in biomass and lipid production was obtained using newly formulated fertilizer medium over f/2 medium. Following optimal parameters [i.e., NaHCO3, (mM), NPK-10:26:26 (g L(-1)), NaCl (M), light intensity (μmol m(-2) s(-1)) and temperature (°C)] were obtained for maximum biomass (1.98 g L(-1)) and lipid production (0.76 g L(-1)): (42.50, 0.33, 1.09, 125, 25.13) and (38.44, 0.40, 1.25, 125, 24.5), respectively using GA. A multi-objective optimization was solved using non-dominated sorting GA to find best operating variables to maximize biomass and lipid production simultaneously. Effects of operating parameters and their interactions on algae and lipid productivity were successfully revealed.

Multi-objective optimization of oil well drilling using elitist non-dominated sorting genetic algorithm

A multi-objective optimization of oil well drilling has been carried out using a binary coded elitist non-dominated sorting genetic algorithm. A Louisiana offshore field with abnormal formation pressure is considered for optimization. Several multi-objective optimization problems involving two-and three-objective functions were formulated and solved to fix optimal drilling variables. The important objectives are: (i) maximizing drilling depth, (ii) minimizing drilling time and (iii) minimizing drilling cost with fractional drill bit tooth wear as a constraint. Important time dependent decision variables are: (i) equivalent circulation mud density, (ii) drill bit rotation, (iii) weight on bit and (iv) Reynolds number function of circulating mud through drill bit nozzles. A set of non-dominated optimal Pareto frontier is obtained for the two-objective optimization problem whereas a non-dominated optimal Pareto surface is obtained for the three-objective optimization problem. Depending on the trade-offs involved, decision makers may select any point from the optimal Pareto frontier or optimal Pareto surface and hence corresponding values of the decision variables that may be selected for optimal drilling operation. For minimizing drilling time and drilling cost, the optimum values of the decision variables are needed to be kept at the higher values whereas the optimum values of decision variables are at the lower values for the maximization of drilling depth.

Coal Bed Methane in India: Difficulties and Prospects

To meet the rapidly increasing demand for energy and faster depletion of conventional energy resources, India with other countries is madly searching for alternate resources like coal bed methane (CBM), shale gas, gas hydrate. CBM is considered to be the most viable resource of these. The present paper discussed about the prospect of CBM as a clean energy source, difficulty involved in production of CBM, enhanced recovery techniques. In this regards, one Indian coal field is selected and gas content is determined by analyzing the collected samples.

Optimal synthesis of methyl ester of Sal oil (Shorea robusta) using ion-exchange resin catalyst

This paper deals with the synthesis of Sal oil methyl ester (SOME) biodiesel using Sal oil (Shorea robusta) and acidic ion-exchange resin catalyst (INDION-225 H). An experimental set-up was proposed for the synthesis of SOME biodiesel where esterification of free fatty acids and transesterification of glycerides of fatty acids took place simultaneously with continuous removal of water. Effects of methanol and catalyst loading were studied to maximize the conversion of Sal oil to SOME biodiesel. Biodiesel productivity was also tested using recycled catalyst and a constant yield of biodiesel was obtained for all the catalyst recycle experiments. Scanning electron microscope (SEM) study of recycled catalyst was carried out to check the morphology of the catalyst and the degradation of the catalyst after recycling. SEM analysis revealed that the catalyst activity remained unchanged after several recycles. In the proposed process, ion-exchange resin not only reduced catalyst consumption and effluent generation considerably but also enhanced the productivity of SOME biodiesel considerably by eliminating the steps of purification. Acid value was measured continuously to monitor the extent of biodiesel formation with reaction time. The yield of SOME biodiesel was measured after purification of the reaction mass and it was tested using ASTM’s standard methods of biodiesel testing. Finally, the properties of SOME biodiesel were compared with the petroleum-based diesel fuel.

Modelling of microalgal growth and lipid production in Dunaliella tertiolecta using nitrogen-phosphorus-potassium fertilizer medium in sintered disk chromatographic glass bubble column.

A comprehensive mathematical model involving NPK-10:26:26 fertilizer, NaCl, NaHCO3, light and temperature operating variables for Dunaliella tertiolecta cultivation is formulated to predict microalgae-biomass and lipid productivity. Proposed model includes Monod/Andrews kinetics for the absorption of essential nutrients into algae-biomass and Droop model involving internal nutrient cell quota for microalgae growth, assuming algae-biomass is composed of sugar, functional-pool and neutral-lipid. Biokinetic model parameters are determined by minimizing the residual-sum-of-square-errors between experimental and computed microalgae-biomass and lipid productivity using genetic algorithm. Developed model is validated with the experiments of Dunaliella tertiolecta cultivation using air-agitated sintered-disk chromatographic glass-bubble column and the effects of operating variables on microalgae-biomass and lipid productivity is investigated. Finally, parametric sensitivity analysis is carried out to know the sensitivity of model parameters on the obtained results in the input parameter space. Proposed model may be helpful in scale-up studies and implementation of model-based control strategy in large-scale algal cultivation.

Effect of light emitting diodes on the cultivation of Spirulina platensis using NPK‐10:26:26 complex fertilizer

NPK‐10:26:26 complex fertilizer based culture medium was studied for the mass production of Spirulina platensis using different light emitting diodes (LEDs). First, cultivation was carried out under white LED to formulate the optimum fertilizer loading for which Spirulina growth was maximized. Optimum composition for newly formulated fertilizer medium was NPK fertilizer −0.76 g L−1 and sodium bicarbonate −10.0 g L−1 and corresponding biomass productivity was found to be 76.67 mg L−1 day−1. The effect of different LEDs (for example, blue, white, red, green and yellow) on Spirulina growth kinetics and the accumulation of chlorophyll, protein and lipid content was determined using the optimum NPK fertilizer medium. Kinetic parameters (i.e., biomass productivity, maximum specific growth rate, maximum biomass concentration, nitrogen‐to‐biomass conversion factor and phosphorus‐to‐biomass conversion factor) and chlorophyll accumulation were affected by the use of different LEDs and follow the following trend: blue > white > red > green > yellow, whereas protein and lipid accumulation was almost independent of LEDs used. Elemental C, N, P and K concentrations were measured to find the effects of nutrients for the growth of Spirulina platensis. Physicochemical parameters (pH and conductivity) were also monitored during biomass growth under different LEDs. Finally, biomass growth using NPK‐10:26:26 fertilizer under different LEDs was compared with standard Zarrouk medium and better growth results were obtained using optimally formulated NPK‐10:26:26 fertilizer medium.