Xylitol has beneficial health properties and can be found in nature albeit in small quantities. In commercial industries, xylitol is produced via chemical hydrogenation of xylose. This process, however, requires high purity of xylose as the raw material. Biotechnological process offers an alternative xylitol production process, using the hydrolysate of lignocellulosic material such as the agricultural waste oil palm empty fruit bunches (OPEFB) as raw material. This substances may contain glucose beside xylose. The presence of glucose as cosubstrate, in the fermentation medium is also a critical factor that regulates the xylitol production by yeasts. Glucose may repress the activity of the key xylose reductase enzyme involved in the xylose conversion into xylitol resulting in low yields of the product. The purpose of this study was to explore the ability of microorganism to produce xylitol from OPEFB hydrolysate. This paper describes the effect of glucose as the co-substrate in xylitol production by Debaryomyces hansenii ITBCC R85 and further the use of OPEFB hydrolyasate as substrate in xylitol production. This research showed that addition of co-substrate glucose affected the fermentation performance of D. hansenii in producing xylitol. Glucose concentration of 2.5 g/L or concentration ratio of glucose to xylose of 25 % gave the highest yield of xylitol. The fermentation using OPEFB hydrolysate containing glucose to xylose ratio more than 25 % gave lower xylitol yield, addressing the hydrolysis of OPEFB to be optimized further.
Empty fruit bunch (EFB) can be used as a solid fuel for heat and power generation. However, high ash particularly potassium content can cause slagging, and fouling which negatively affect thermal conversion systems. A pretreatment process to remove potassium and achieve better solid fuel characteristics from EFB was proposed by employing the hydrothermal treatment (HT) followed by the washing process. EFB was treated via HT at the temperatures of 100, 150, 180 and 220°C with the holding time of 30 min. A batch washing process was then conducted at different solid-product to liquid ratios. In this study, raw EFB and HT products were experimentally investigated in the laboratory to determine the effects of HT and the washing process on the potassium removal efficiency. Thermal behaviors of unwashed and washed products were also investigated. The results showed that the combination of HT-180 and washing can remove potassium up to 92 %, lowering the ash content down to 0.9 % and the chlorine content down to 0.19 % which led to a significant improvement in its thermal behavior with lowering the slagging tendencies. These results indicated that HT followed by the washing process is a viable way to obtain a low potassium content solid fuel.
Adsorption of copper, nickel and cadmium ions from aqueous solution by poly(acrylic acid) and polyacrylamide modified corn cob was investigated. The modified corn cob was characterized by optical microscope, FTIR, CHNO elemental analysis and N2 adsorption-desorption. The effect of parameters on heavy metal adsorption including contact time and concentration were studied. The results showed the maximum adsorption capacities of chemically modified corn cob were 239.55, 156.46 and 361.89 g kg-1 for Cu(II), Ni(II) and Cd(II), respectively. Langmuir isotherm was fitted with the adsorption equilibrium and the pseudo-second order was fitted with the adsorption kinetics for all metal ions. The adsorbents were easily regenerated by 0.1 mol dm-3 HCl solution up to four cycles with the removal performance of 59-100%.
Apple stem is one of the main waste biomass resources in Aomori prefecture, Japan. Using apple stem as the raw material for the extraction of nanocellulose is attractive for treating such a waste biomass, which can lower economic cost, and add value in cultivation. In this study, the apple stem was pretreated using typical cellulose extraction method, followed by acid hydrolysis of cellulose in mild condition for production of nanocellulose. The obtained product was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TG). The results confirmed that nanocelluloses with diameters around 10-20 nm were obtained. The nanocellulose was in whisker shape with higher crystallinity, higher thermal stability at high temperature, and no obvious composition change occurred during the acid hydrolysis.
Steam reforming (SR) and partial oxidation (POx) of nascent volatiles (NV) generated from fast pyrolysis of cedar wood chips in a two-stage reactor were studied numerically. A detailed chemical kinetic model (DCKM) consisting of more than 8000 elementary step-like reactions and more than 500 chemical species was used to simulate pyrolysis at 750°C and reforming of the NV at 900°C in the first and second stages, respectively. The molecular composition of the NV, which is one of the required boundary conditions for computations using the DCKM, was approximated based on analytical pyrolysis experiments. Global reactions accounting for the decomposition of the ill-defined portion of the NV and soot reforming were also tested to improve the model capabilities. The DCKM with the global reaction coupled with a plug-flow reactor model could fairly reproduce the experimentally observed trends for the effects of oxygen and steam partial pressures on the yields of major products such as hydrogen, carbon monoxide, and tar residual rate.
To establish a sustainable regional biomass use system, clarifying the present condition in the objective area and proposing a proper scenario to improve the present conditions are important. In this study, one suburban village where rice cultivation and livestock industries are popular in Southern Vietnam was selected as the objective area. Literature review, interviews at the site and field surveys were conducted to analyze material flow in agricultural production and excreta treatment of livestock. As a result, it was clarified that surface water quality at some points in the canals, rivers and wells of the village did not meet the national standard, and contributions of discharges of untreated livestock excreta to total nitrogen loads to lower water bodies were large (43% in total). From another aspect, some rice straw was burned without any effective use at the paddy fields. For this situation, two scenarios were proposed and designed as “Plan model 1” and “Plan model 2”. The one is to increase biogas digesters in the village for treatment of untreated livestock excreta, decrease washing water rate poured into biogas digesters and use slurry from the biogas digester (hereafter, slurry) at paddy and non-paddy fields as a fertilizer. Another is to use unused rice straw for producing bio-ethanol. By these scenarios, the possibility was shown that approximately 327,000 Nm3/year of biogas and more than 240 kL/year (≓190 t/y) of bio-ethanol can be produced in objective village, 39% of nitrogen load to water bodies and 95% of application rate of chemical fertilizer to agricultural field could be decreased, and greenhouse gas emission rate could be decreased if bio-ethanol is substituted for fossil fuel.
The methanolysis of para rubber seed oil in the presence of the catalyst CH3/SO3H-MCM-41 was investigated with the aim of improving catalytic stability. Using 5.06 wt% of CH3/SO3H-MCM-41, we obtained a 95% yield of the fatty acid methyl ester. A kinetic study was conducted in which the reaction time and temperature were varied in the range of 30-150 min and 120-160°C, respectively. The activation energy, pre-exponential factor, and reaction order were determined. It was shown that the reaction approached first order kinetics (n = 1.08, R2 > 0.99). The activation energy (Ea) and frequency factor (A) were found to be 29.2 kJ/mol and 129.3 min-1 (mol/g)-0.0807, respectively.
This research aimed to study the potential of furfural production via green chemicals (supercritical ethanol and formic acid) using oil palm biomass. Furfural was obtained via reaction conducted using a high-pressure and high-temperature mini-batch reactor. Various reaction parameters were studied including temperature, reaction time, solid loading, and alcohol-acid ratio. Depolymerisation of the pentosan into xylose by supercritical ethanol and subsequent dehydration of xylose into furfural from the acid-catalyzed reaction occurred simultaneously in the minibatch reactor.Results obtained showed the highest furfural yield of 88.7% at 260°C, 10 min, 0.6 g solid loading, and 1:2 alcohol: acid ratio.The highlight of this research is in the use of green chemicals in which a fully biomass-based process were achieved as both ethanol and formic acid can be produced from biomass itself. Ethanol is produced by fermentation of saccharides. Meanwhile formic acid is generated from furfural production itself.
A dual-fluidized bed system that comprised a fast fluidized bed regenerator and a bubbling bed carbonator was operated under a temperature condition of Calcium Looping process for CO2 capture. Three kinds of coal with different volatile matter content were burned in the regenerator in oxygen-enriched atmosphere. Gas mixture consisted of NO, O2, and N2 was fed to the carbonator to simulate the interaction between char and NO in the flue gas from an air-blown combustor. Inert quartz sand was used as the bed material. Formation of CO and CO2 in the carbonator from oxidation of char which was entrained from the regenerator was measured. With char combustion, small amount of NOX was formed in the carbonator when NO-free gas was fed. With NO feed to the carbonator, a part of the fed NO was reduced by char. Thus the char particles in the carbonator were effective for NOX reduction when NO concentration in the feed gas was high. Formation of N2O in the carbonator was less than 10 ppm. The increase in greenhouse effect due to N2O emissions was calculated to be far less than the decrease in greenhouse effect by capturing CO2.