A Review on 1st and 2nd Generation Bioethanol Production-Recent Progress

Today's society is based on the use of fossil resources for transportation fuels. The result of unlimited consumption of fossil fuels is a severe depletion of the natural reserves and damage to the environment. Depleting fossil reserves and increasing demand for energy together with environmental concerns have motivated researchers towards the development of alternative fuels which are eco-friendly, renewable and economical. Bioethanol is one such dominant global renewable transport biofuel which can readily substitute fossil fuels. Conventionally, bioethanol has been produced from sucrose and starch rich feedstocks (edible agricultural crops and products) known as 1st generation bioethanol; however this substrate conflicts with food and feed production. As an alternative to 1st generation bioethanol, currently there is much focus on advancing a cellulosic bioethanol concept that utilizes lignocellulosic residues from agricultural crops and residues (such as bagasse, straw, stover, stems, leaves and deoiled seed residues). Efficient conversion of lignocellulosic biomass into bioethanol remains an area of active research in terms of pretreatment of the biomass to fractionate its constituents (cellulose, hemicellulose and lignin), breakdown of cellulose and hemicellulose into hexose and pentose sugars and co-fermentation of the sugars to ethanol. The present review discusses research progress in bioethanol production from sucrose, starch and cellulosic feedstocks. Development of efficient technology to convert lignocellulosic biomass into fermentable sugars and optimization of enzymatic hydrolysis using on-site/ in-house enzyme preparation are the key areas of development in lignocellulosic bioethanol production. Moreover, finding efficient fermenting microorganisms which can utilize pentose and hexose sugars in their metabolism to produce ethanol together with minimum foam and glycerol formation is also an important parameter in fermentation. Research has been focus

Study of thermal behavior of deoiled karanja seed cake biomass: thermogravimetric analysis and pyrolysis kinetics

Karanja is a medium sized evergreen tree which has minor economic importance in India. The nonedible seed kernel contains 27-30% oil that is used for biodiesel production, leaving the remaining nonedible seed cake as a waste product. The aim of the present work was to obtain kinetic parameters in relation to technological parameters in nonedible seed cake biomass pyrolysis conversion process to bio-oil and biochar. Effects of heating rate on karanja seed cake slow pyrolysis behavior and kinetic parameters were investigated at heating rates of 5, 10, and 20°C/min using thermogravimetric analysis (TGA). Thermogravimetric experiments showed the onset and offset temperatures of the devolatilization step shifted toward the high-temperature range, and the activation energy values increased with increasing heating rate. In the present study, isoconversional method was applied for the pyrolysis of karanja seed cake biomass by TGA and the activation energies (118-124 kJ/mol) and the pre-exponential factors obtained using progressive conversion. Proximate-ultimate analyses, energy value, surface structure, and Fourier transform infrared spectra of the biomass processed under conditions were reported. The pyrolysis resulted in upgradation of the energy value of seed cake biomass from 18.1 to 24.5 MJ/kg; importantly with high carbon and low oxygen contents. The approach represents a novel method for the upgrading of karanja seed cake that has significant commercial potential

Desorption studies for the recovery of radionuclides (Th and Zr) and optimization using Taguchi mixed design L18(2132) - A regeneration step for loaded biosorbent, general mathematical model for multistage operation

Thorium and zirconium are the most stable radionuclides used in various nuclear operations and the removal of them from aqueous industrial streams is essential. Biosorption is one of the most effective removal processes and it will be more attractive if loaded biomass can be regenerated for reuse. Reported studies on the desorption of metal ions from loaded biomass is limited in the literature. The present study aims to investigate the desorption of Th and Zr from loaded deoiled Karanja seed cake (DKSC) and study the efficiency of desorption process. All desorption experiments were carried out under batch mode using different eluents by varying liquid to solid (L/S) ratio, eluent type and concentration. Taguchi mixed level design L18(2132) was used to optimize the process and achieve the maximum desorption efficiency (D%). The eluent concentration was found to be the major factor that affects desorption. The optimum conditions for maximum D% inlcude 1 M HCl at L/S ratio of 7 with a recovery of 96% and 0.1 M NaHCO3 at L/S ratio of 3 with a recovery of 69% for thorium and zirconium, respectively. It was also shown that desorption kinetics follows pseudo-second order for both thorium and zirconium at optimal conditions. The regenerated DKSC was found to possess properties similar to those of native DKSC. A simple mathematical model was developed for computing the concentration of metal ions in the eluent in a counter-current multi-stage desorption system and validated using thorium desorption kinetic data

Derivation of optimum operating conditions for the slow pyrolysis of Mahua press seed cake in a fixed bed batch reactor for bio-oil production

The effect of pyrolysis temperature, retention time and inert gas (i.e. N2) flow rate on the conversion of Mahua Press Seed Cake (PSC) into bio-oil was studied in a slow pyrolysis fixed bed batch reactor. The optimum operating conditions for the process were derived using a Response Surface Methodology (RSM). It was found that the highest bio-oil yield (49.25 wt.%) can be achieved at a moderate temperature of 475 °C and a retention time of 45 min. As expected, the bio-oil yield was found to be affected by the reaction temperature. In a GC-MS analysis of the bio-oil, major compounds found were 6-octadecenoic acid, octadecanoic acid and free fatty acids (FFAs). The physicochemical properties of a raw PSC and bio-char were studied using bomb calorimeter, elemental analysis, and Fourier Transform Infrared (FT-IR) spectroscopy techniques. The heating value of the pyrolytic bio-oil (31.53 MJ/kg) at 475 °C was found to be increased by 46% compared to that of raw PSC (21.592 MJ/kg). The FT-IR analysis indicates that there was a decrease in the number of O-H (hydroxyl), C-H (alkanes) and C-O (primary alcohol) groups and an increase in the number of C=C (aromatics) functional groups with an increase in the pyrolysis temperature. Bio-gas analysis confirmed that, at higher temperatures, higher gas yield with increased CO and CH4 contents was observed. Finally, from the energy balance and economic analysis, it has been confirmed that at the derived optimum operating conditions it is feasible to produce bio-oil from Mahua PSC

An experimental study to investigate the effect of torrefaction temperature on the kinetics of gas generation

Pre-treatment of biomass using torrefaction has been demonstrated to be an efficient process to improve the physical and chemical properties of biomass that can be used as a promising feedstock for gasification and boilers. Karanja, neem, kusum, mahua, and microalgae were the five biomass feedstocks investigated in this work for the torrefaction pre-treatment. The experimental study of torrefaction was carried out in a vertical fixed bed reactor set-up at 200, 250, and 300°C under nitrogen atmosphere. A thorough analysis of gas, liquid and solid products was made and the changes in H/C and O/C ratios in the pre-treated biomass were analyzed by elemental analysis. Among the five biomass feedstocks studied, mahua was found to have the highest heating value of 27.73MJ/kg at 300°C compared to others (neem=19MJ/kg, Karanja=23.3MJ/kg, kusum=25.8MJ/kg, microalgae=26.7MJ/kg). Following a detailed kinetic analysis using the yield of product gas mixtures, it is concluded that the biogases are generated by parallel independent first-order reactions. Also, the activation energy values for the torrefaction reactions of five biomass feedstocks were found to be different from each other

Experimental investigations on the effect of pyrolytic bio-oil during the liquefaction of Karanja press seed cake

In this study, experimental investigations on the liquefaction of Karanja Press Seed Cake (PSC) were carried out in the presence of Pyrolytic Bio-oil (PBO) produced from the slow pyrolysis of the same feedstock. The effects of PBO amount and temperature were studied with an aim to achieve the highest conversion in liquefaction experiments. Also, comparison has been established between the use of PBO and conventional solvent and acid catalyst such as phenol and sulphuric acid, respectively for achieving the highest liquefaction conversion. A detailed chemical analysis and a comparison of PBO and liquefied product (bio-crude) have been carried out using FT-IR, and GC-MS techniques. The results showed that the Karanja PSC could be directly liquefied in the presence of PBO at moderate reaction conditions. A maximum liquefaction conversion of 99% was obtained at a reaction temperature of 240 °C, a residence time of 160 min and a Karanja PSC to PBO ratio of 1:6. In contrast, ~ 94% conversion was obtained for the same residence time but at significantly lower temperature of 160 °C when phenol and sulphuric acid were used in the ratio of Karanja PSC, phenol and H2SO4 as 1:2:0.6. It was observed that aromatic structure with less oxygen was evident in bio-crude compared to PBO

Recovery of levulinic acid by reactive extraction using tri-n-octylamine in methyl isobutyl ketone: Equilibrium and thermodynamic studies and optimization using Taguchi multivariate approach

Recovery of levulinic acid from an aqueous solution using a tertiary amine, tri-n-octylamine (TOA), as an extractant in methyl isobutyl ketone (MIBK) was studied at different temperatures (293-333 K). The physical equilibrium studies were performed using MIBK as a diluent. Partition (P) and dimerization (D) coefficients were found to decrease noticeably with increasing temperature. The coefficient of distribution was found to be very low in physical equilibrium. Chemical equilibrium studies were conducted using various concentrations of the extractant. The highest coefficient of distribution (K D ) and efficiency of extraction (%E) were found to be 58.0 and 98.0% respectively for 0.1 kmol m -3 of levulinic acid and 0.678 kmol m -3 of TOA at 293 K. Chemical equilibrium studies showed the formation of 2:1 complex as the main mechanism in the reactive extraction. Taguchi mixed design multivariate approach (L 18 ) was used to optimize the process variables. S/N ratio (larger-is-better) criterion was adopted to maximize the perfor mance parameters. The optimum combination of variables was found to include acid concentration (X 1 ) = 0.3 kmol m -3 , TOA concentration (X 2 ) = 0.678 kmol m -3 and temperature (X 3 ) = 293 K. A confirmation run was conducted using these parameters and K D and %E values from this run were determined to be 11.83 and of 92.2%, respectively, which were very close to the predicted values of K D = 12.78 and %E = 94%

Regeneration of levulinic acid from loaded-organic phase: equilibrium, kinetics and process economics

Regeneration of carboxylic acids from the loaded- organic phase is an essential step to complete the reactive extraction process. A study on the regeneration of levulinic acid from loaded-organic phase (methyl isobutyl ketone + tri-n-octylamine +acid) was carried out using various techniques including NaOH, temperature swing, diluent swing, and tri-methylamine methods. Equilibrium data obtained show that among all the methods, the recovery of acid is the highest for the tri methylamine method when the molar ratio of tri-methylamine to levulinic acid concentrations is greater than 1. Kinetic studies performed for the tri-methylamine method showed that there are no changes in the specific rate of extraction with changes in stirrer speed rate and phase volume ratio (Vaq/ Vorg), and the overall order of reaction is 1.5. Based on the effects of stirrer speed and phase volume ratio on the specific rate of extraction, the reaction was concluded to occur in the fast regime. Also, about 80% of acid was recovered by the evaporation of tri-methylamine phase at 104-140 oC. A detailed economic evaluation for the recovery of levulinic acid using reactive extraction for a feed rate of 2 m3 h-1 shows that the payback period for recovering capital investment is 0.49 years

Oxygen-steam gasification of karanja press seed cake: Fixed bed experiments, ASPEN Plus process model development and benchmarking with saw dust, rice husk and sunflower husk

This article aims at investigating the oxygen-steam gasification of Karanja press seed cake using experimental and modeling studies and compare the results of these studies with those for other feedstocks such as rice husk, sawdust, and sunflower husk. The experimental work was conducted in a fixed bed reactor and the process simulation model was created in ASPEN Plus. Finally, validation and benchmarking exercise were conducted by validating the ASPEN Plus model using experimental results. A general agreement was found between the experimental results and ASPEN Plus process model results with a maximum variation of ±4%. Furthermore, sensitivity analyses were carried out to understand the effects of parameters such as gasification temperature, ER (equivalence ratio), and SBR (steam to biomass ratio) on synthesis gas composition, LHV (lower heating value) and CGE (cold gas efficiency). The optimal values of ER and SBR in this study were found to be 0.23 and 0.3, respectively. The CGE was found to increase with an increase in the temperature. Values of CGE and LHV were found to be as high as 95% and ∼12 MJ/Nm3, respectively at 1000 °C for all feedstocks. The optimum SBR value was found to vary from 0.3 to 0.7 for H2/CO variation in the range of ∼0.83-1.0

Optimization of process parameters for slow pyrolysis of neem press seed cake for liquid and char production

Slow pyrolysis of neem press seed cake (NPSC) was carried out in a fixed bed batch reactor to study the effects of temperature, retention time, and nitrogen (N 2 ) flow rate on liquid and char yields. Response surface methodology (RSM) based on Box-Behnken design was used to determine the optimum operating conditions to maximize the liquid yield. The highest liquid yield of 52.1 wt% was obtained at 512.5 °C, after 60 min using 0.5 L/min N 2 flow rate. Scanning electron microscopy (SEM), elemental analysis, bomb calorimeter, Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffraction techniques and gas chromatography-mass spectrometry (GC-MS) were used to determine the physicochemical properties of NPSC and char, and chemical properties of liquid. GC-MS analysis showed that the bio-oil was rich in 9-octadecenamide, 2-propenyl decanoate, heptadecanenitrile, and oleanitrile. The higher heating value of the bio-oil and NPSC were 32.8 and 16.05 MJ/kg, respectively at 575 °C. The FT-IR results showed a decrease in the number of O-H (hydroxyl), C-H (alkanes), C=O (esters), -C-H (alkanes), and C-O (primary alcohol) groups in NPSC with increasing pyrolysis temperature