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The Economics of Ethanol, Agriculture and Food  [cached]
Douglas Auld
Journal of Sustainable Development , 2012, DOI: 10.5539/jsd.v5n8p136
Abstract: The global expansion of the production and consumption of bio-fuels has had a pronounced and widespread impact on related factor and product markets. This is most notable in the case of ethanol. The use of corn to produce bio-fuel for blending with gasoline in many countries has contributed to the recent increases in the price of corn and food. The diversion of corn from food and animal feed to fuel, and the conversion of crop land to produce corn-for-fuel, has led to supply and price pressure on other cereal and feed crops. This has led to diminished and more costly supplies of food for global food aid programs.
Enlargement Test Studies of Bio-hydrogen Production using Artificial Wastewater of Corn Stalk Fermentation Lixivium by Mixed Culture
玉米秸秆发酵浸出液模拟废水发酵产氢的放大实验研究

ZHANG Mao-lin,WEI Rui-xia,FAN Yao-ting,XING Yan,HOU Hong-wei,
张茂林
,魏瑞霞,樊耀亭,杏艳,侯红卫

环境科学 , 2007,
Abstract: Conversion of artificial corn stalk wastewater, which was prepared according to the main composition of the corn stalk fermentation lixivium, into bio-hydrogen gas by mixed culture was performed in a 20 L half-continuous flow fermenter. The influences of several environmental factors on the bio-hydrogen production, such as HRT, C/N ratio, Fe2+ and artificial corn stalk wastewater concentration were discussed in the tests. The experimental results showed that HRT, C/N ratio, Fe2+ and artificial corn stalk wastewater concentration significantly affected the fermentation hydrogen production. The maximum H2 yield of 11.80 mol/kg, H2 concentration of 56% and hydrogen production rate of 8.81 L/(L x d) were obtained at HRT = 10 h, C/N = 100, Fe2+ concentration of 100 mg/L and substrate concentration of 12.5 g/L by mixed culture, respectively. In the fermentation hydrogen-producing process, the conversion efficiency of the substrate was more than 90%, and 39.40% of COD was removed from the reactor. The main by-products in the liquid phase were acetic acid, butyric acid, propionic acid and a little ethanol and butanol throughout this study.
Carbon Balance Analysis of Corn Fuel Ethanol Life Cycle
玉米燃料乙醇生命周期碳平衡分析

ZHANG Zhi-shan,YUAN Xi-gang,
张治山
,袁希钢

环境科学 , 2006,
Abstract: The quantity of greenhouse gas emissions(net carbon emissions) of corn-based fuel ethanol,which is known as an alternative for fossil fuel is an important criteria for evaluating its sustainability.The methodology of carbon balance analysis for fuel ethanol from corn was developed based on principles of life cycle analysis.For the production state of fuel ethanol from summer corn in China,carbon budgets in overall life cycle of the ethanol were evaluated and its main influence factors were identified.It presents that corn-based fuel ethanol has no obvious reduction of carbon emissions than gasoline,and potential improvement in carbon emission of the life cycle of corn ethanol could be achieved by reducing the nitrogen fertilizer and irrigation electricity used in the corn farming and energy consumption in the ethanol conversion process.
Net Energy Analysis of Corn Fuel Ethanol Life Cycle
玉米燃料乙醇生命周期净能量分析

ZHANG Zhi-shan,YUAN Xi-gang,
张治山
,袁希钢

环境科学 , 2006,
Abstract: Energy efficiency(net energy gain or energy ratio) of corn-based ethanol as a substitute for fossil fuel is an important criteria for assessing its sustainability.The method of net energy analysis for fuel ethanol from corn was developed based on principles of life cycle inventory(LCI) analysis.For the production state of fuel ethanol from summer corn in China,energy efficiency of the corn fuel ethanol life cycle system was estimated and its main influence factors were identified,and energy saving effect of some ethanol blended gasoline fuels was discussed.Corn fuel ethanol has certain energy benefits.The energy ratios for dry and wet milling process were 1.25 and 1.04 respectively.Through comparison of energy inputs in corn fuel ethanol life cycle,fossil energy inputs of corn production and ethanol conversion processes were identified as the most important,and therefore nitrogen fertilizer,electivity and diesel used in corn farming and energy consumption of distillation and dehydration process in ethanol production could be known as the most influential factors for the energy benefit of corn fuel ethanol.
The Food Crises: A quantitative model of food prices including speculators and ethanol conversion  [PDF]
Marco Lagi,Yavni Bar-Yam,Karla Z. Bertrand,Yaneer Bar-Yam
Quantitative Finance , 2011,
Abstract: Recent increases in basic food prices are severely impacting vulnerable populations worldwide. Proposed causes such as shortages of grain due to adverse weather, increasing meat consumption in China and India, conversion of corn to ethanol in the US, and investor speculation on commodity markets lead to widely differing implications for policy. A lack of clarity about which factors are responsible reinforces policy inaction. Here, for the first time, we construct a dynamic model that quantitatively agrees with food prices. The results show that the dominant causes of price increases are investor speculation and ethanol conversion. Models that just treat supply and demand are not consistent with the actual price dynamics. The two sharp peaks in 2007/2008 and 2010/2011 are specifically due to investor speculation, while an underlying upward trend is due to increasing demand from ethanol conversion. The model includes investor trend following as well as shifting between commodities, equities and bonds to take advantage of increased expected returns. Claims that speculators cannot influence grain prices are shown to be invalid by direct analysis of price setting practices of granaries. Both causes of price increase, speculative investment and ethanol conversion, are promoted by recent regulatory changes---deregulation of the commodity markets, and policies promoting the conversion of corn to ethanol. Rapid action is needed to reduce the impacts of the price increases on global hunger.
Enzymatic digestibility and ethanol fermentability of AFEX-treated starch-rich lignocellulosics such as corn silage and whole corn plant
Qianjun Shao, Shishir PS Chundawat, Chandraraj Krishnan, Bryan Bals, Leonardo Sousa, Kurt D Thelen, Bruce E Dale, Venkatesh Balan
Biotechnology for Biofuels , 2010, DOI: 10.1186/1754-6834-3-12
Abstract: AFEX-pretreated starch-rich substrates (for example, corn grain, soluble starch) had a 1.5-3-fold higher enzymatic hydrolysis yield compared with the untreated substrates. Sequential addition of cellulases after hydrolysis of starch within WCP resulted in 15-20% higher hydrolysis yield compared with simultaneous addition of hydrolytic enzymes. AFEX-pretreated CS gave 70% glucan conversion after 72 h of hydrolysis for 6% glucan loading (at 8 mg total enzyme loading per gram glucan). Microbial inoculation of CS before ensilation yielded a 10-15% lower glucose hydrolysis yield for the pretreated substrate, due to loss in starch content. Ethanol fermentation of AFEX-treated (at 6% w/w glucan loading) CS hydrolyzate (resulting in 28 g/L ethanol at 93% metabolic yield) and WCP (resulting in 30 g/L ethanol at 89% metabolic yield) is reported in this work.The current results indicate the feasibility of co-utilization of whole plants (that is, starchy grains plus cellulosic residues) using an ammonia-based (AFEX) pretreatment to increase bioethanol yield and reduce overall production cost.Impending energy shortages and widespread environmental pollution are two major challenges facing humanity in the 21st century. Petroleum is an important and scarce resource that meets 44% of the world's total energy demand. The increasing worldwide demand for crude oil and the dwindling petroleum resources have led to the development of alternative sources of fuel that can displace fossil fuels [1,2]. Many nations have initiated programs to develop alternative fuels, such as the 'Office of Energy Efficiency and Renewable Energy's Biomass Program', which aims to replace 20% of gasoline consumed in the USA, with alternative renewable fuels over the coming decade [3]. Ethanol is one such alternative renewable fuel that can potentially replace gasoline.Currently, corn grain is the major US feedstock for producing fermentation-based ethanol, produced using either the wet or dry grind process[4]
Ethanol production from corn stover pretreated by electrolyzed water and a two-step pretreatment method
XiaoJuan Wang,Hao Feng,ZhiYi Li
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5079-1
Abstract: Pretreatment is one of the most important unit operations for ethanol production from biomass feedstocks. In this study, corn stover was used as a feedstock to examine the effectiveness of two pretreatments: electrolyzed water pretreatment and a two-step pretreatment. Electrolyzed water was employed as a catalyst to conduct one-step pretreatment of corn stover at three temperatures (165, 180 and 195°C) and three treatment times (10, 20 and 30 min). During the two-step pretreatment process, an organic alkaline solution of 1% (w/w) NaOH in 70% (w/w) ethanol was used for lignin removal in the first step, followed by a second step using hot water. No furfural or 5-hydroxymethyl furfural was detected in the hydrolysates from both pretreatment methods when the detection limit of the HPLC was 0.2 g/L. The highest glucan conversion yields were 83% obtained at 195°C for 30 min with acidic electrolyzed water and 83% by the two-step process, where the second step of the pretreatment was at 135°C for 30 min. The hydrolyzates from the two pretreatment methods showed good performance in Saccharomyces cerevisiae fermentation tests. The two new methods may provide promising alternatives for the pretreatment of biomass for ethanol production.
Ethanol and biogas production after steam pretreatment of corn stover with or without the addition of sulphuric acid  [cached]
Bondesson Pia-Maria,Galbe Mats,Zacchi Guido
Biotechnology for Biofuels , 2013, DOI: 10.1186/1754-6834-6-11
Abstract: Background Lignocellulosic biomass, such as corn stover, is a potential raw material for ethanol production. One step in the process of producing ethanol from lignocellulose is enzymatic hydrolysis, which produces fermentable sugars from carbohydrates present in the corn stover in the form of cellulose and hemicellulose. A pretreatment step is crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars, and later ethanol. This study has investigated steam pretreatment of corn stover, with and without sulphuric acid as catalyst, and examined the effect of residence time (5–10 min) and temperature (190–210°C) on glucose and xylose recovery. The pretreatment conditions with and without dilute acid that gave the highest glucose yield were then used in subsequent experiments. Materials pretreated at the optimal conditions were subjected to simultaneous saccharification and fermentation (SSF) to produce ethanol, and remaining organic compounds were used to produce biogas by anaerobic digestion (AD). Results The highest glucose yield achieved was 86%, obtained after pretreatment at 210°C for 10 minutes in the absence of catalyst, followed by enzymatic hydrolysis. The highest yield using sulphuric acid, 78%, was achieved using pretreatment at 200°C for 10 minutes. These two pretreatment conditions were investigated using two different process configurations. The highest ethanol and methane yields were obtained from the material pretreated in the presence of sulphuric acid. The slurry in this case was split into a solid fraction and a liquid fraction, where the solid fraction was used to produce ethanol and the liquid fraction to produce biogas. The total energy recovery in this case was 86% of the enthalpy of combustion energy in corn stover. Conclusions The highest yield, comprising ethanol, methane and solids, was achieved using pretreatment in the presence of sulphuric acid followed by a process configuration in which the slurry from the pretreatment was divided into a solid fraction and a liquid fraction. The solid fraction was subjected to SSF, while the liquid fraction, together with the filtered residual from SSF, was used in AD. Using sulphuric acid in AD did not inhibit the reaction, which may be due to the low concentration of sulphuric acid used. In contrast, a pretreatment step without sulphuric acid resulted not only in higher concentrations of inhibitors, which affected the ethanol yield, but also in lower methane production.
Ammonia disinfection of corn grains intended for ethanol fermentation
Magdalena Broda,W?odzimierz Grajek
Acta Scientiarum Polonorum : Technologia Alimentaria , 2009,
Abstract: Background. Bacterial contamination is an ongoing problem for commercial bioethanol plants. It concerns factories using grain and also other raw materials for ethanol fermentation. Bacteria compete with precious yeasts for sugar substrates and micronutrients, secrete lactic and acetic acids, which are toxic for yeast and this competition leads to significant decrease of bioethanol productivity. For this study, bacterial contamination of corn grain was examined. Then the grain was treated by ammonia solution to reduce microbial pollution and after that the microbiological purity of grain was tested one more time. Disinfected and non-disinfected corn grains were ground and fermentation process was performed. Microbiological purity of this process and ethanol yield was checked out. Material and methods. The grain was disinfected by ammonia solution for two weeks. Then the grain was milled and used as a raw material for the ethanol fermentation. The fermentation process was carried out in 500-ml Erlenmeyer flasks. Samples were withdrawn for analysis at 0, 24, 48, 72 hrs. The number of total viable bacteria, lactic acid bacteria, acetic acid bacteria, anaerobic bacteria and the quantity of yeasts and moulds were signified by plate method. Results. Ammonia solution effectively reduces bacterial contamination of corn grain. Mash from grain disinfected by ammonia contains less undesirable microorganisms than mash from crude grain. Moreover, ethanol yield from disinfected grain is at the highest level. Conclusions. The ammonia solution proved to be a good disinfection agent for grain used as a raw material for bioethanol fermentation process.
Catalytic conversion of ethanol on H-Y zeolite  [PDF]
?egar Nedeljko,Penavin-?kundri? Jelena,?kundri? Branko,Petrovi? Rada
Hemijska Industrija , 2005, DOI: 10.2298/hemind0510267c
Abstract: The catalytic activity of the H-form of synthetic zeolite NaY was examined in this study. The catalytic activity was determined according to the rate of ethanol conversion in a gas phase in the static system. In the conversion of ethanol on synthetic NaY zeolite at 585, 595, and 610 K, on which the reaction develops at an optimal rate, ethene and diethyl ether are evolved in approximately the same quantity. After transforming the NaY zeolite into the H-form, its catalytic activity was extremely increases so, the reaction develops at a significantly lower temperature with a very large increase in the reaction rate. The distribution of the products also changes, so that at lower temperatures diethyl ether is elvolved in most cases, and the development of ethene is favored at higher ones, and after a certain period of time there is almost complete conversion of ethanol into ethene. The increase in catalytic activity, as well as the change of selectivity of conversion of ethanol on the H-form of zeolite, is the result of removing Na+ cations in the NaY zeolite, so that more acidic catalyst is obtained which contains a number of acidic catalytically active centers, as well as a more powerful one compared to the original NaY zeolite.
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