Optimization of bioethanol production from glycerol by Escherichia coli SS1

Bioethanol is a promising biofuel and has a lot of great prospective and could become an alternative to fossil fuels. Ethanol fermentation using glycerol as carbon source was carried out by local isolate, ethanologenic bacterium Escherichia coli SS1 in a close system. Factors affecting bioethanol production from pure glycerol were optimized via response surface methodology (RSM) with central composite design (CCD). Four significant variables were found to influence bioethanol yield; initial pH of fermentation medium, substrate concentration, salt content and organic nitrogen concentration with statistically significant effect (p ≤ 0.05) on bioethanol production. The significant factor was then analyzed using central composite design (CCD). The optimum conditions for bioethanol production were substrate concentration at 34.5 g/L, pH 7.61, and organic nitrogen concentration at 6.42 g/L in which giving ethanol yield approximately 1.00 mol/mol. In addition, batch ethanol fermentation in a 2 L bioreactor was performed at the glycerol concentration of 20 g/L, 35 g/L and 45 g/L, respectively. The ethanol yields obtained from all tested glycerol concentrations were approaching theoretical yield when the batch fermentation was performed at optimized conditions.     

Development of the concept of environmentally friendly CHPP and TPP with the active use of photosynthetic processes

The article considers the possibility of applying the concept of a “transition link” from hydrocarbon to “green” energy. The entire world industry uses hydrocarbons as fuel. The share of “green” energy is growing, but it cannot completely replace oil, gas and coal at this stage. In many production processes, due to technology, a significant amount of heat is lost. Thus, the anthropogenic impact is doubled both due to fuel combustion and due to heat losses into the environment. Traditional methods of reducing harmful emissions, as a rule, are focused only on a specific type of treatment and are capital treatment facilities. The authors' approach to the problem differs from the generally accepted one. The developed method makes it possible to obtain an additional product due to waste heat, while reducing emissions of carbon monoxide into the atmosphere. The authors have chosen Combined heat power plant (CHPP), thermal power plant (TPP) as the object of research. Their role as a source of heat, light and hot water supply can hardly be overestimated. But thermal power plants and thermal power plants are also sources of greenhouse gases generated during fuel combustion, sources of heat loss with exhaust gases and thermal pollution of water bodies with cooling liquid. Thermal pollution of water bodies leads to their overgrowth with algae, and as a result, deterioration of water quality. The method presented by the authors is based on the integrated use of waste heat generated in large volumes in algae cooling ponds and the production of bioethanol. Studies were carried out on a mass spectrometer of the chemical composition of algae formed in various media (sea, tap and purified water). During the experiments, legumes were grown on purified water, tap water, and distilled water. According to the calculations, the cost of 1 L of the resulting bioethanol will be about 28 rubles/l, which is 3 times cheaper than what is currently produced. It is concluded that the polluted water of a thermal power plant or thermal power plant has a negligible effect on the bioethanol yield. A 17.8-fold decrease in sodium was shown due to the use of biofilters. During the experiments, legumes were grown on purified water, tap water, and distilled water.The conclusion is made about the significant adsorption capacity of Zn, Mg, Fe, Al, Si, Pb ions. The resulting water after passing through the algae was tested according to SanPiN 2.1.4.1074-01, and fully complied with the standard, which allows it to be used for technological and technical purposes and, moreover, to be returned to the natural environment without consequences.The work is planned within the framework of an international project to create devices and industrial technology that provides for the production of synthesis gas in a fuel processor and hydrogen for generating electrical energy using a fuel cell.     

Enzymatische Hydrolyse und Fermentation von Apfeltrester

Apple pomace is a complex, carbohydrate-rich by-product of apple juice production and an interesting raw material for the production of platform chemicals such as ethanol and acetic acid. By simultaneous saccharification and fermentation, the pomace was degraded to 82 %. In the fermentation medium, the ethanol concentration was ∼5.7 vol %, which allows an economical further processing of the ethanol. Tank sediment (sludge) and accompanying substances (sorted out biomass) are also available for fermentative utilization, with acetic acid as the preferred product. The N-rich tank sediment can replace part of the required tap water and makes the addition of micronutrients unnecessary.     

Consumer choice between ethanol and gasoline: Lessons from Brazil and Sweden

The introduction of flex-fuel vehicles since 2003 has made possible for Brazilian drivers to choose between high ethanol blends or gasoline depending on relative prices and fuel economies. In Sweden, flex-fuel fleets were introduced in 2005. Prices and demand data were examined for both Brazil and Sweden. Bioethanol has been generally the most cost-efficient fuel in Brazil, but not for all states. In any case, consumers in Brazil have opted for ethanol even when this was not the optimal economic choice. In Sweden, a different behavior was observed when falling gasoline prices made E85 uneconomical in late 2008. In a context of international biofuels expansion, the example of E85 in Sweden indicates that new markets could experience different consumer behavior than Brazil: demand falls rapidly with reduced price differences between ethanol and gasoline. At the same time, rising ethanol demand and lack of an international market with multiple biofuel producers could lead to higher domestic prices in Brazil. Once the limit curve is crossed, the consumer might react by shifting back to the usage of gasoline.     

The impact of a growing bioethanol industry on food production in Brazil

The Brazilian production of major food commodities increased fivefold between 1961 and 2008. In the same time, the area cropped with sugar cane increased with high growth rates, currently covering 3% of the area dedicated to agricultural production in Brazil. In order to assess a possible competition between biofuel and food production, the development of agricultural productivity and area expansion in the past was analysed. Furthermore, the future situation of land resources for agricultural production was illustrated. The findings of this study indicated that area resources of more than 20 million hectare would be available for agricultural production in the upcoming years. A current constraint of food production throughout land dedicated to biofuels was not found. Three scenarios were investigated, simulating possibilities of future changes in Brazilian agriculture. The results demonstrated that primary food production could be enhanced by 1.5 times while bioethanol production was enhanced simultaneously by 1.8 times over the years 2007/2008 and 2020. The generated bioethanol volumes would meet 38% of the total energy demand in Brazilian transport sector, applied to the year 2007. The second scenario evaluated an agricultural development with a higher focus on biofuels. It was projected that the production of bioethanol could be increased by 3.0 times to 76.7 million m³ of bioethanol, while increasing at the same time primary food production with the factor 1.4 aligned to the projected population growth. This bioethanol volume represents 67% of the total energy demand in Brazilian transport sector in the year 2007. A third scenario demonstrated that food production could be increased even with no area expansion higher than the projected population growth, due to a continued increase of productivity. At the same time bioethanol production would rise to 32 million m³ without occupying more area.     

Production of liquid biofuels from renewable resources

This article is an up-to-date review of the literature available on the subject of liquid biofuels. In search of a suitable fuel alternative to fast depleting fossil fuel and oil reserves and in serious consideration of the environmental issues associated with the extensive use of fuels based on petrochemicals, research work is in progress worldwide. Researchers have been re-directing their interests in biomass based fuels, which currently seem to be the only logical alternative for sustainable development in the context of economical and environmental considerations. Renewable bioresources are available globally in the form of residual agricultural biomass and wastes, which can be transformed into liquid biofuels. However, the process of conversion, or chemical transformation, could be very expensive and not worth-while to use for an economical large-scale commercial supply of biofuels. Hence, there is still need for much research to be done for an effective, economical and efficient conversion process. Therefore, this article is written as a broad overview of the subject, and includes information based on the research conducted globally by scientists according to their local socio-cultural and economic situations.     

Comparative study of fuel gas production for SOFC from steam and supercritical-water reforming of bioethanol

Theoretical study of fuel gas (H₂ + CO) production for SOFC from bioethanol was carried out to compare performances between two reforming technologies, including steam reforming (SR) and supercritical-water reforming (SCWR). It demonstrates that the fuel gas productions are comparable among the two reforming systems; however, SCWR requires the operation at much higher temperature and pressure than SR. The maximum hydrogen yield can be obtained at 850 K, atmospheric pressure, ethanol to water molar feed ratio of 1:20 for SR system and at 1300 K, 22.1 MPa, and ethanol to water feed ratio of 1:20 for SCWR. The use of a distillation column to purify the bioethanol feed was proven to improve the fuel conversion efficiency of both systems. The analysis reveals that SCWR is a promising system for fuel production for SOFC when a gas turbine is incorporated to the system for energy recovery. Further, it is not necessary to distil bioethanol to obtain too high ethanol recovery (i.e. >90%) as higher energy consumption at the distillation column could lead to lower overall thermal efficiency.     

Process control analysis for intensified bioethanol separation systems

The purification of bioethanol is traditionally performed by extractive distillation using three column sequences. In the present work new arrangements composed of two columns are considered for the analysis of control properties. The control properties study was based on the controllability properties under open loop operation, followed by the dynamic behavior for common industrial operating disturbances. Simulation results were analyzed by the singular value decomposition technique. The results from the theoretical control properties indicate that the presence of a side stream in the extractive distillation sequences does not necessarily provide operational disadvantages. The results also suggest that control properties are ruled by the kind of solvent used. The best performances were obtained when glycerol is used as entrainer.     

Anaerobic digestion of maize focusing on variety,harvest time and pretreatment

The methane potential of six varieties of fresh maize (whole plant) harvested at three different times and of maize silage (whole plant) in two particle size distributions was experimentally determined in batch assays. Fresh maize gave the highest methane yield/hectare at late harvest (6270 m³ CH₄ (10⁴ m²)⁻¹). The methane yield/wet weight (WW) increased from 80 (early harvest) to 137 m³ CH₄ (t WW)⁻¹ (late harvest). Maize harvested at different times, or different varieties of maize had similar specific methane production/volatile solids content (m³ CH₄ (kg VS)⁻¹). The measured yield m³ CH₄ (kg VS)⁻¹ was 84% of the theoretical methane potential. The estimated ethanol yield was between 2.5 and 3.5 t ethanol (10⁴ m²)⁻¹. The energy yield was 62 and 19–22 MWh (10⁴ m²)⁻¹ if fresh maize (whole plant) is used for methane or ethanol production respectively. Reducing the particle size of maize silage to an average size of approximately 2 mm increased the methane yield m³ CH₄ (kg VS)⁻¹ by approximately 10%.