Simulation of a hydrogen production and purification system for a PEM fuel-cell using bioethanol as raw material

A process to produce “fuel-cell grade” hydrogen from ethanol steam reforming is analyzed from a thermodynamic point of view. The hydrogen purification process consists of WGS and COPROX reactors. Equations to evaluate the efficiency of the system, including the fuel cell, are presented. A heat exchange network is proposed in order to improve the exploitation of the available power. The effect of key variables such as the reformer temperature and the ethanol/water molar feed ratio on the fuel-cell efficiency is discussed. Results show that it is feasible to carry out the energy integration of the hydrogen catalytic production and purification—PEM fuel-cell system, using ethanol as raw material. The technology of “fuel-cell grade” hydrogen production using ethanol as raw material is a very attractive alternative to those technologies based in fossil fuels.     

Energy and eMergy evaluation of bioethanol production from wheat in Henan Province,China

Ethanol production from wheat has become an emerging economic activity in Henan Province due to the establishment in 2001 of the National Program for Alcohol Production. The program aimed at facing the unfolding world energy crisis in the near future and increasing China's energy security. Instead, in spite of claims for “green energy”, such an activity is likely to generate great environmental damage and social problems. Moreover, the international market prices for raw materials (especially cereals) and fossil oil are putting this activity under siege. This research presents an energy and eMergy analysis of a typical wheat plantation/alcohol distillery system, in the Henan Province. Comparison is drawn with bioethanol production in Italy, based on corn from intensive, industrialized agriculture. Energy and eMergy indices of ethanol production from wheat and corn in the two agro-industrial systems are respectively as follows: output/input energy ratio, 1.09 (wheat) and 1.19 (corn); transformity of bioethanol, 2.77×105 and 1.89×105 seJ/J; renewability, 20% and 11%; eMergy yield ratio, 1.24 and 1.14; environmental loading ratio, 4.05 and 7.84; and finally eMergy sustainability index, 0.31 and 0.15. Results show that bioethanol from food crops is not a sustainable source of fuel.     

Can the environmental benefits of biomass support agriculture?—The case of cereals for electricity and bioethanol production in Northern Spain

Recent policy documents, such as the EC Communication on an Energy Policy for Europe (January 2007) make emphasis on the opportunities that energy applications can offer certain agricultural commodities, especially in the framework of a progressive dismantling of the Common Agricultural Policy. This paper analyses whether this can be true for wheat and barley farmers, using the real example of a straw-based power plant in Northern Spain and a theoretical factory for bioethanol production fed with cereal grain. The outcomes of such an exercise, in which their relative environmental benefits vis-à-vis fossil fuel alternatives are worked out with the aid of a simplified life-cycle approach, show that the characteristics of the electricity and biomass markets, the baseline scenario and the fuel prices are crucial for the future of the sector.     

Effectiveness of dilute oxalic acid pretreatment of Miscanthus × giganteus biomass for ethanol production

In the present study the effect of temperature, reaction time and dilute oxalic acid (OA) concentration during steam-pretreatment of Miscanthus × gigantueus has been evaluated using the combined severity factor (CS). At the highest CS glucan and lignin content in the water insoluble fraction (WIF) increased, while xylan content decreased. While glucose recovery in the water soluble fraction (WSF) was found at low concentration when mild CS were used (≤5.0 g L⁻¹ at CS ≤ 2.17), xylose and arabinose concentrations were higher at low-mild CS (1.58–2.17) with a concentration peak at CS 2.03 (39.9 and 3.2 g L⁻¹ for xylose and arabinose, respectively). The decrease in pentoses coincided with inhibitory formation in the WSF, namely acetic acid, furfural, HMF and phenolic compounds. Glucan conversion rose from 46.1% at CS 1.54 to 91.2% at CS 2.76. Likewise, maximum ethanol concentration was achieved at CS 2.76, corresponding to 20.2 g L⁻¹ and a volumetric ethanol productivity of 0.28 g L⁻¹ h⁻¹. Negative correlations have been found between xylan vs. glucan conversion and xylan vs. ethanol production, suggesting that decreasing the xylan content in WIF increases both saccharification rate and ethanol concentration (R² 0.91 and R² 0.93, respectively). On the other hand, a positive correlation was found between ethanol production and glucan conversion (R² 0.93). Fermentation of WSF by Scheffersomyces (Pichia) stipitis CBS 6054 at CS 1.54 produced 12.1 g L⁻¹ of ethanol after 96 h incubation with a volumetric ethanol productivity of 0.13 g L⁻¹ h⁻¹.     

Yttria-stabilized zirconia (YSZ) supported Ni–Co alloys (precursor of SOFC anodes) as catalysts for the steam reforming of ethanol

Bioethanol is an attractive fuel for direct internal reforming SOFC (DIR-SOFC). The aim of this work is to investigate the activity of Ni–YSZ, used as precursor for the preparation of SOFC anodes and as catalyst of the ethanol steam reforming reaction. The effect of the addition of cobalt is also studied, as the best performance is given by Ni–Co (25:25)/YSZ catalyst. This achieves total conversion of ethanol around 670 K, at which temperature the H₂ yield is 65%. The addition of Co results in the inhibition of the dehydration reaction as well as of methane production. Furthermore, Co also has an effect on the hydrogen yield, by increasing it and thus apparently favouring methane steam reforming.     

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.     

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.     

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.     

Stakeholders' perceptions on challenges and opportunities for biodiesel and bioethanol policy development in Thailand

Thailand is Southeast Asia's largest promoter of biofuels. Although, Thailand promotes the use of biofuels, it has yet to achieve its policy targets. This paper focuses on the first generation biofuel development in Thailand and examines the perceptions of seven stakeholder groups to guide further policy development. These stakeholders were feedstock producers, biofuel producers, government agencies, car manufacturers, oil companies, non-profit organizations and end users. It combines a Strengths, Weakness, Opportunities and Threats (SWOT) framework with an Analytical Hierarchy Process (AHP) framework and a TOWS Matrix for analysis of stakeholder's perceptions to propose priorities for policy development. Five policies were of high priority for development of biofuel. These are: (1) promoting biofuel production and use in long term through government policies, (2) revising government regulations to allow sale of biofuel products to other domestic industries while keeping retail prices of blended biofuels below those of regular ethanol and biodiesel, (3) improving farm management and promoting contract farming, (4) expanding cultivation area and yield without affecting food production and environmental sustainability, and (5) balancing biofuel feedstock use between the food and energy industries.