Market penetration of biodiesel

This research examines in detail the technology and economics of substituting biodiesel for diesel #2. This endeavor examines three areas. First, the benefits of biodiesel are examined, and the technical problems of large-scale implementation. Second, the biodiesel production possibilities are examined for soybean oil, corn oil, tallow, and yellow grease, which are the largest sources of feedstocks for the United States. Examining in detail the production possibilities allows to identity the extent of technological change, production costs, byproducts, and greenhouse gas (GHG) emissions. Finally, a U.S. agricultural model, FASOMGHG was used to predict market penetration of biodiesel, given technological progress, variety of technologies and feedstocks, market interactions, energy prices, and carbon dioxide equivalent prices.FASOMGHG has several interesting results. First, diesel fuel prices have an expansionary impact on the biodiesel industry. The higher the diesel fuel prices, the more biodiesel is produced. However, given the most favorable circumstances, the maximum biodiesel market penetration is 9% in 2030 with a wholesale diesel price of $4 per gallon. Second, the two dominant sources of biodiesel are from corn and soybeans. Sources like tallow and yellow grease are more limited, because they are byproducts of other industries. Third, GHG prices have an expansionary impact on the biodiesel prices, because biodiesel is quite GHG efficient. Finally, U.S. government subsidies on biofuels have an expansionary impact on biodiesel production, and increase market penetration at least an additional 3%.     

Can increasing gasoline supply in the United States affect ethanol production in Brazil?

The increasing supply of non-conventional oil in the U.S. has changed the dynamics of crude oil market and the flow of oil products in the Atlantic Basin. The Gulf of Mexico (GoM) emerges as an exportation hub of oil products, contributing to a scenario in which gasoline prices tend to decline. Meanwhile, from 2010, the competitiveness of the Brazilian sugarcane ethanol has been ruptured by the country's gasoline price policy that had not followed international price parity. The political conjuncture of the U.S. incites high utilization rates of their refining system in the GoM. In this context the profitability of the ethanol business can be impacted in Brazil, by either the current policy of controlled domestic gasoline prices or a future scenario of declining gasoline international prices. Therefore, this study tests if this gasoline price scenario can compromise even more the competitiveness of the Brazilian ethanol. Particularly, for a scenario of falling prices, ethanol production in Brazil would be under strong pressure of gasoline supply coming from the U.S. This can impact Brazil's ethanol industry, whose development has been justified by climate change policies. In that sense, the paper also discusses the future opportunities and challenges for Brazil's ethanol industry.     

Reducing life cycle greenhouse gas emissions of corn ethanol by integrating biomass to produce heat and power at ethanol plants

A life-cycle assessment (LCA) of corn ethanol was conducted to determine the reduction in the life-cycle greenhouse gas (GHG) emissions for corn ethanol compared to gasoline by integrating biomass fuels to replace fossil fuels (natural gas and grid electricity) in a U.S. Midwest dry-grind corn ethanol plant producing 0.19 hm³ y⁻¹ of denatured ethanol. The biomass fuels studied are corn stover and ethanol co-products [dried distillers grains with solubles (DDGS), and syrup (solubles portion of DDGS)]. The biomass conversion technologies/systems considered are process heat (PH) only systems, combined heat and power (CHP) systems, and biomass integrated gasification combined cycle (BIGCC) systems. The life-cycle GHG emission reduction for corn ethanol compared to gasoline is 38.9% for PH with natural gas, 57.7% for PH with corn stover, 79.1% for CHP with corn stover, 78.2% for IGCC with natural gas, 119.0% for BIGCC with corn stover, and 111.4% for BIGCC with syrup and stover. These GHG emission estimates do not include indirect land use change effects. GHG emission reductions for CHP, IGCC, and BIGCC include power sent to the grid which replaces electricity from coal. BIGCC results in greater reductions in GHG emissions than IGCC with natural gas because biomass is substituted for fossil fuels. In addition, underground sequestration of CO₂ gas from the ethanol plant’s fermentation tank could further reduce the life-cycle GHG emission for corn ethanol by 32% compared to gasoline.     

Comparative environmental performance of lignocellulosic ethanol from different feedstocks

A renewable biofuel economy is projected as a pathway to decrease dependence on fossil fuels as well as to reduce greenhouse gases (GHG) emissions. Ethanol produced on large-scale from lignocellulosic raw materials is considered the most potential next generation automotive fuel. In this paper, a Life Cycle Assessment model was developed to evaluate the environmental implications of the production of ethanol from five lignocellulosic materials: alfalfa stems, poplar, Ethiopian mustard, flax shives and hemp hurds and its use in passenger cars. Two ethanol-based fuel applications, E10 (a mixture of 10% ethanol and 90% gasoline by volume) and E85 (85% ethanol and 15% gasoline by volume) were assessed and the results were compared to those of conventional gasoline (CG) in an equivalent car.The environmental performance was assessed in terms of fossil fuels requirements, global warming, photochemical oxidant formation, acidification and eutrophication by means of the Life Cycle Assessment (LCA) methodology in order to identify the best environmental friendly lignocellulosic source. The results show that, compared to CG, life cycle greenhouse gases emissions are lower for etanol blends, specifically up to 145% lower for E85-fueled car derived from Ethiopian mustard. This crop is also the best option in terms of eutrophying emissions regardless the ratio of ethanol in the blend. In the remaining impact categories, other feedstocks are considered beneficial, that is, poplar in the case of photochemical oxidants formation and flax shives for acidification. Concerning fossil fuels requirements, decreases up to 10% and 63% for E10 and E85 derived from hemp hurds and Ethiopian mustard, respectively, were obtained.According to the results, the study clearly demonstrates the importance of using low intensive energy and high biomass yield crops. LCA procedure helps to identify the key areas in the ethanol production life cycle where the researchers and technicians need to work to improve the environmental performance. Technological development could help in lowering both the environmental impact and the prices of the ethanol fuels.     

Life cycle assessment of flax shives derived second generation ethanol fueled automobiles in Spain

Biofuel use seems to have certain environmental, energy and socioeconomic advantages versus fossil fuel consumption. The substitution of fossil fuels with biofuels can be a useful tool to fulfil the Spanish and European policy in relation to mitigation of greenhouse gas (GHG) emissions and increase the security in energy supply. The continuous increase in energy consumption, dependence on energy and high petroleum prices has motivated increasing support for renewable energy promotion. In Spain (the third ethanol producer in Europe in 2007), ethanol from lignocellulosic feedstocks could be one of the most valuable and interesting possibilities for renewable transportation fuels due to the limited competition with food production and high net reduction of GHG emissions. This study is focused on flax shives, obtained as an agricultural co-product from flax crops dedicated to fibre production for specialty paper pulp manufacture as lignocellulosic biomass to produce second generation ethanol involving the use of cellulosic technology. The life cycle assessment (LCA) methodology was used to evaluate the environmental impacts of the production and use in a flexi fuel vehicle (FFV) of ethanol blends (10 and 85% in volume of ethanol with gasoline) versus conventional gasoline, throughout their whole life cycle in order to highlight the main sources of these impacts. The system boundaries include cultivation, extraction, processing and final use of fuels. Mass and economic allocation were considered to determine the effect on the results of different allocation approaches.The results of the study show that the allocation methods are essential for outcomes and decision-making. Using ethanol as transportation fuel could present better environmental performance than conventional gasoline in terms of global warming and fossil fuel consumption according to mass allocation. However, environmental credits could be achieved in terms of acidification, fossil fuel consumption and human toxicity according to economic allocation. Contributions to other impact categories such as eutrophication and photochemical oxidants formation were lower for conventional gasoline regardless of the allocation procedure selected. Agricultural activities related to feedstock production are notable contributors to the environmental performance. Thus, high yielding varieties, reduction of tillage activities and reduction in fertilization should help to reduce these impacts.     

Life cycle assessment and life cycle costing of bioethanol from sugarcane in Brazil

Brazil has always been the pioneer in the application of bioethanol as a main fuel for automobiles, hence environmental and economic analyses of the Brazilian ethanol industries are of crucial importance. This study presents a comparative life cycle assessment (LCA) on gasoline and ethanol as fuels, and with two types of blends of gasoline with bioethanol, all used in a midsize car. The focus is on a main application in Brazil, sugarcane based ethanol. The results of two cases are presented: base case—bioethanol production from sugarcane and electricity generation from bagasse; future case—bioethanol production from both sugarcane and bagasse and electricity generation from wastes. In both cases sugar is co-produced. The life cycles of fuels include gasoline production, agricultural production of sugarcane, ethanol production, sugar and electricity co-production, blending ethanol with gasoline to produce E10 (10% of ethanol) and E85 (85%), and finally the use of gasoline, E10, E85 and pure ethanol. Furthermore, a life cycle costing (LCC) was conducted to give an indication on fuel economy in both cases. The results show that in the base case less GHG is emitted; while the overall evaluation of these fuel options depends on the importance attached to different impacts. The future case is certainly more economically attractive, which has been the driving force for development in the ethanol industry in Brazil. Nevertheless, the outcomes depend very much on the assumed price for crude oil. In LCC a steady-state cost model was used and only the production cost was taken into account. In the real market the prices of fuels are very much dependent on the taxes and subsidies. Technological development can help in lowering both the environmental impact and the prices of the ethanol fuels.     

Applying life-cycle assessment to low carbon fuel standards—How allocation choices influence carbon intensity for renewable transportation fuels

The Energy Independence and Security Act (EISA) of 2007 requires life-cycle assessment (LCA) for quantifying greenhouse gas emissions (GHGs) from expanded U.S. biofuel production. To qualify under the Renewable Fuel Standard, cellulosic ethanol and new corn ethanol must demonstrate 60% and 20% lower emissions than petroleum fuels, respectively. A combined corn-grain and corn-stover ethanol system could potentially satisfy a major portion of renewable fuel production goals. This work examines multiple LCA allocation procedures for a hypothetical system producing ethanol from both corn grain and corn stover. Allocation choice is known to strongly influence GHG emission results for corn-ethanol. Stover-derived ethanol production further complicates allocation practices because additional products result from the same corn production system. This study measures the carbon intensity of ethanol fuels against EISA limits using multiple allocation approaches. Allocation decisions are shown to be paramount. Under varying approaches, carbon intensity for corn ethanol was 36–79% that of gasoline, while carbon intensity for stover-derived ethanol was −10% to 44% that of gasoline. Producing corn-stover ethanol dramatically reduced carbon intensity for corn-grain ethanol, because substantially more ethanol is produced with only minor increases in emissions. Regulatory considerations for applying LCA are discussed.     

Environmental life cycle assessment of lignocellulosic conversion to ethanol: A review

Bioenergy from lignocellulosic biomass offers the potential to provide a significant source of clean, low carbon and secure energy. In recent years, a number of studies have been carried out to assess the environmental performance of lignocellulosic ethanol fuel. However, the complexity of biofuel systems generates significantly different results due to the differences in input data, methodologies applied, and local geographical conditions. Moreover, much attention has been placed on assessing climate change potential and energy consumption. This study draws on 53 published life cycle assessment of the lignocellulosic ethanol. More than half of the articles reviewed focus on assessing greenhouse gas (GHG) emission or fossil energy consumption or combination of both. All studies but two reviewed conclude that there is a reduction of GHG emission when using lignocellulosic ethanol in comparison to fossil fuel reference system. However, different studies have reported different sources contributing to GHG emission: some reports majority of GHG emissions come from biomass cultivation stage; others argue significant GHG emissions from ethanol conversion process. All articles suggest a reduction of fossil consumption in all cases of ethanol fuel. Contrary results for the impact of acidification and eutrophication potential from lignocellulosic ethanol are also observed—some reports less impact in comparison to conventional gasoline whiles others report significant increase of acidification and eutrophication potential by ethanol production. Studies also show water consumption varies significantly depending on biomass types, irrigation requirement, and regional irrigation practices; with different findings on whether agricultural practices or ethanol conversion being the main sources for water consumption. Contrary findings on emissions contributing to ecotocixity and human health have also been reported with some being favourable while others not. Results from the literature also suggest strong dependency of LCA results on system boundary, functional unit, data quality and allocation methods chosen.     

Economic and policy implications of public support for ethanol production in California's San Joaquin Valley

The US Environmental Protection Agency requires that only oxygenated gasoline may be sold in regions that are not in compliance with national air quality standards. Several non-attainment regions are located in California, and most of the gasoline sold there is oxygenated with methyl tertiary butyl ether (MTBE). California is planning to discontinue the use of MTBE in gasoline by January 2004. This policy will generate greater demand for ethanol, which is the leading substitute for MTBE. Most of the ethanol required in California will be imported from other states, unless California develops an ethanol production industry. The costs of producing ethanol in California may exceed the benefits, unless substantial value is attributed to non-market, public goods, such as maintaining agriculture and reducing unemployment in rural areas. We examine the firm-level economics of using corn and other agricultural products to produce ethanol in California, and the potential regional economic impacts of building and operating an ethanol plant. The cost of production is greater than the current price of ethanol for all of the feedstocks we consider. Production generates economic activity, but at current prices for inputs and outputs, substantial subsidies will be required to encourage firms to produce ethanol in California.     

Greenhouse gas impacts of ethanol from Iowa corn: Life cycle assessment versus system wide approach

Life cycle assessment (LCA) is the standard approach used to evaluate the greenhouse gas (GHG) benefits of biofuels. However, the need for the appropriate use of LCA in policy contexts is highlighted by recent findings that corn-based ethanol may actually increase GHG emissions. This is in contrary to most existing LCA results. LCA estimates can vary across studies due to heterogeneities in inputs and production technology. Whether marginal or average impacts are considered can matter as well. Most important of all, LCA is product-centered. The determination of the impact of biofuels expansion requires a system wide approach (SWA) that accounts for impacts on all affected products and processes.This paper presents both LCA and SWA for ethanol based on Iowa corn. LCA was conducted in several different ways. Growing corn in rotation with soybean generates 35% less GHG emissions than growing corn after corn. Based on average corn production, ethanol's GHG benefits were lower in 2007 than in 2006 because of an increase in continuous corn in 2007. When only additional corn was considered, ethanol emitted about 22% less GHGs than gasoline. SWA was applied to two simple cases. Using 2006 as a baseline and 2007 as a scenario, corn ethanol's benefits were about 20% of the emissions of gasoline. If geographical limits are expanded beyond Iowa, then corn ethanol could generate more GHG emissions than gasoline. These results highlight the importance of boundary definition for both LCA and SWA.     

Fuel ethanol production from sugarcane and corn: Comparative analysis for a Colombian case

The Colombian government has defined the use of bioethanol as a gasoline enhancer to reduce greenhouse gases, gasoline imports, and to boost the rural economy. To meet the projected fuel ethanol demand needed to oxygenate the gasoline in the whole country, the construction of about five additional ethanol production plants is required. For this, a comparative analysis of the technological options using different feedstocks should be performed. In this work, a comparison of the economical and environmental performance of the ethanol production process from sugarcane and corn under Colombian conditions has been carried out. Net present value and total output rate of potential environmental impact were used as the economical and environmental indicators, respectively. Through the integration of these indicators into one index by using the analytical hierarchy process (AHP) approach, sugarcane ethanol process was determined as the best choice for Colombian ethanol production facilities. AHP scores obtained in this study for sugarcane and corn ethanol were 0.571 and 0.429, respectively. However, starchy crops like corn, cassava or potatoes used as feedstock for ethanol production could potentially cause a higher impact on the rural communities and boost their economies if social matters are considered.     

Lignocellulosic biomass for bioethanol production: Current perspectives,potential issues and future prospects

During the most recent decades increased interest in fuel from biomass in the United States and worldwide has emerged each time petroleum derived gasoline registered well publicized spikes in price. The willingness of the U.S. government to face the issues of more heavily high-priced foreign oil and climate change has led to more investment on plant-derived sustainable biofuel sources. Biomass derived from corn has become one of the primary feedstocks for bioethanol production for the past several years in the U.S. However, the argument of whether to use food as biofuel has led to a search for alternative non-food sources. Consequently, industrial research efforts have become more focused on low-cost large-scale processes for lignocellulosic feedstocks originating mainly from agricultural and forest residues along with herbaceous materials and municipal wastes. Although cellulosic-derived biofuel is a promising technology, there are some obstacles that interfere with bioconversion processes reaching optimal performance associated with minimal capital investment. This review summarizes current approaches on lignocellulosic-derived biofuel bioconversion and provides an overview on the major steps involved in cellulosic-based bioethanol processes and potential issues challenging these operations. Possible solutions and recoveries that could improve bioprocessing are also addressed. This includes the development of genetically engineered strains and emerging pretreatment technologies that might be more efficient and economically feasible. Future prospects toward achieving better biofuel operational performance via systems approaches such as risk and life cycle assessment modeling are also discussed.     

Biomass availability for lignocellulosic ethanol production

The ethanol industry in North America uses starch derived from corn as its primary feedstock. In order to better understand the geographical distribution of advanced ethanol production, potential sources of lignocellulosic biomass for the process are considered. It is shown that the corn-producing regions of North America already support significant amounts of ethanol production, and that few unexploited sources of corn remain for the industry to utilize. Accessing other sources of sugar, including other types of biomass such as lignocellulosic materials, will become necessary for the industry as it expands, quite apart from the need to meet government mandates. The ability of bioconversion and thermochemical conversion to generate biofuels from lignocellulosic biomass is reviewed. The availability of lignocellulosic residues from agricultural and forestry operations is described, and the potential biofuel production associated with these residues is described. A residue-based process could greatly extend the potential of the ethanol industry to become a substantial contributor to the fuel and energy requirements of North America. It is estimated that ethanol production from residues could provide up to 13.7% of Canada’s 2009 transportation fuel demand, and up to 5.2% of the United States’ 2010 fuel demand. Utilizing lignocellulosic biomass will extend the geographic range of the biofuel industry, and increase the stability and security of this sector by reducing the impact of localized disruptions in supply. Development of a residue-based industry will help create the technologies needed to process energy crops as North America moves towards greater transportation fuel independence.     

Economic challenges for the future relevance of biofuels in transport in EU countries

The discussion on the promotion of biofuels is ambiguous: on the one hand benefits like reduction of greenhouse gas emissions and increase of energy supply security are expected, on the other hand low effectiveness with respect to reducing greenhouse gas emissions and high costs are being criticized. The core objective of this paper is to investigate the market prospects of biofuels for transport in the EU in a dynamic framework till 2030. The major results of this analysis are: (i) Under current policy conditions – mainly exemption of excise taxes – the economic prospects of 1st generation biofuels in Europe are rather promising; the major problems of 1st generation biofuels are lack of available land for feedstocks and the modest ecological performance; (ii) Large expectations are currently put into advanced 2nd generation biofuels production from lignocellulosic materials. With respect to the future costs development of 2nd generation biofuels, currently it can only be stated that in a favourable case by 2030 they will be close to the costs of 1st generation biofuels. However, because of the increasing prices for fossil gasoline and diesel in all international scenarios – given remaining tax exemptions – biofuels will become competitive already in the next few years.     

Comparison of fixed versus variable biofuels incentives

We evaluated several variants of a variable biofuel subsidy and compared them with the fixed subsidy and Renewable Fuel Standard using two different modeling approaches. First we used a partial equilibrium model encompassing crude oil, gasoline, ethanol, corn, and ethanol by-products. Second, we used a stochastic simulation model of a prototypical ethanol plant. From the partial equilibrium analysis, it appears the variable subsidy provides a safety net for ethanol producers when oil prices are low; yet, it does not put undue pressure on corn prices when oil prices are high. At high oil prices, the level of ethanol production is driven by market forces. From the plant level stochastic analysis, essentially the same conclusions are reached. As with the fixed subsidy, the variable subsidy can increase the net present value (NPV) sufficiently to encourage investment, but with lower risk for the producer, lower probability of a loss from the investment, and often lower expected cost to government. Finally, in the US, the ethanol industry is up against a blending limit called the blend wall. If the blending wall remains in place and no way around it is found, it does not matter much what other policy options are used.     

A comparative life cycle assessment of bio‐ and conventional fuels in a Canadian province

In this paper, a comprehensive study on corn‐based ethanol in a Canadian context is conducted, which uses the most reliable and up to date data, considers realistic assumptions, and applies sound methodology to provide a basis for developing future scenarios for corn‐based ethanol and compared the results with the conventional fuel, such as gasoline. It is estimated that the net energy value (NEV), defined as the energy content of a liter of ethanol minus the total energy use to produce a liter of ethanol, is 9.6 MJ L^?1 (LHV), when co‐products energy credits are not considered. In addition, a comparison of life cycle energy use for corn‐based ethanol and gasoline reveals that the life cycle energy use to produce a liter of ethanol is considerably less than the life cycle energy use to produce a liter of gasoline. Furthermore, a comparison of life cycle greenhouse gas (GHG) emissions for corn‐based ethanol and gasoline reveals that the life cycle GHG emissions released per liter of ethanol produced is an order of magnitude lesser than the life cycle GHG emissions released per liter of gasoline produced, when GHG emissions displaced by ethanol co‐products are considered in the estimation. Finally, a comparison of our results in terms of net fossil fuel input, net fossil fuel ratio and GHG emissions is carried out with the results obtained from the ERG biofuel analysis meta‐model (EBAMM) to reflect both Canadian and US perspectives. Copyright © 2010 John Wiley & Sons, Ltd.     

Land use change in a biofuels hotspot: The case of Iowa, USA

This study looks at the land use impact of the biofuels expansion on both the intensive and extensive margin, and its environmental consequences. We link economic, geographical and environmental models by using spatially explicit common units of analysis and use remote sensing crop cover maps and digitized soils data as inputs. Land use changes are predicted via economic analysis of crop rotation choice and tillage under alternative crop prices, and the Environmental Policy Integrated Climate (EPIC) model is used to predict corresponding environmental impacts. The study focuses on Iowa, which is the leading biofuels hotspot in the U.S. due to intensive corn production and the high concentration of ethanol plants that comprise 28% of total U.S. production. We consider the impact of the biofuels industry both on current cropland and on land in the Conservation Reserve Program (CRP), a land set-aside program. We find that substantial shifts in rotations favoring continuous corn rotations are likely if high corn prices are sustained. This is consistent with larger scale analyses which show a shift of the current soybean production out of the Corn Belt. We find that sediment losses increase substantially on the intensive margin, while nitrogen losses increase less. Returning CRP land into production has a vastly disproportionate environmental impact, as non-cropped land shows much higher negative marginal environmental effects when brought back to row crop production. This illustrates the importance of differentiating between the intensive and extensive margin when assessing the expansion of biofuel production.     

Progress in bioethanol processing

Production of ethanol (bioethanol) from biomass is one way to reduce both consumption of crude oil and environmental pollution. Bioethanol is appropriate for the mixed fuel in the gasoline engine because of its high octane number, and its low cetane number and high heat of vaporization impede self-ignition in the diesel engine. So, ignition improver, glow-plug, surface ignition, and pilot injection are applied to promote self-ignition by using diesel-bioethanol-blended fuel. Disadvantages of bioethanol include its lower energy density than gasoline, its corrosiveness, low flame luminosity, lower vapor pressure (making cold starts difficult), miscibility with water, and toxicity to ecosystems. Bioethanol can be produced from cellulosic feedstocks. One major problem with bioethanol production is the availability of raw materials for the production. The availability of feedstocks for bioethanol can vary considerably from season to season and depends on geographic locations. Lignocellulosic biomass is the most promising feedstock considering its great availability and low cost, but the large-scale commercial production of fuel bioethanol from lignocellulosic materials has still not been implemented. Conversion technologies for producing bioethanol from cellulosic biomass resources such as forest materials, agricultural residues and urban wastes are under development and have not yet been demonstrated commercially. For designing fuel bioethanol production processes, assessment of utilization of different feedstocks (i.e. sucrose containing, starchy materials, lignocellulosic biomass) is required considering the big share of raw materials in bioethanol costs. In this work a review of the biological and thermochemical methods that could be used to produce bioethanol is made and an analysis of its global production trends is carried out.     

How to improve the economy of bioethanol production in Serbia

Bioethanol accounts for the majority of biofuel use worldwide, either as a fuel or a gasoline enhancer. In Serbia, the industrial production of bioethanol still relies on conventional feedstocks containing starch and sugar such as corn, wheat and molasses. In order to improve the economy of bioethanol production and to avoid the competition of the feedstock utilization for food and energy, several production approaches based on crop selection, process integration and waste utilization were considered in this paper. Particular attention was put on utilization of non conventional crops such as triticale and damaged crops not appropriate for food consumption. Potential of lignocellulosic biomass for the production of second generation ethanol in Serbia was also considered as well as the utilization of stillage as a main by-product. The investigated approaches can significantly improve the economy of bioethanol production and contribute to solve serious environmental problems.     

Energy and greenhouse gas emission effects of corn and cellulosic ethanol with technology improvements and land use changes

Use of ethanol as a transportation fuel in the United States has grown from 76 dam³ in 1980 to over 40.1 hm³ in 2009 — and virtually all of it has been produced from corn. It has been debated whether using corn ethanol results in any energy and greenhouse gas benefits. This issue has been especially critical in the past several years, when indirect effects, such as indirect land use changes, associated with U.S. corn ethanol production are considered in evaluation. In the past three years, modeling of direct and indirect land use changes related to the production of corn ethanol has advanced significantly. Meanwhile, technology improvements in key stages of the ethanol life cycle (such as corn farming and ethanol production) have been made. With updated simulation results of direct and indirect land use changes and observed technology improvements in the past several years, we conducted a life-cycle analysis of ethanol and show that at present and in the near future, using corn ethanol reduces greenhouse gas emission by more than 20%, relative to those of petroleum gasoline. On the other hand, second-generation ethanol could achieve much higher reductions in greenhouse gas emissions. In a broader sense, sound evaluation of U.S. biofuel policies should account for both unanticipated consequences and technology potentials. We maintain that the usefulness of such evaluations is to provide insight into how to prevent unanticipated consequences and how to promote efficient technologies with policy intervention.