Ethanol Production Cost Research Articles

Explaining the experience curve: Cost reductions of Brazilian ethanol from sugarcane

Production costs of bio-ethanol from sugarcane in Brazil have declined continuously over the last three decades. The aims of this study are to determine underlying reasons behind these cost reductions, and to assess whether the experience curve concept can be used to describe the development of feedstock costs and industrial production costs. The analysis was performed using average national costs data, a number of prices (as a proxy for production costs) and data on annual Brazilian production volumes. Results show that the progress ratio (PR) for feedstock costs is 0.68 and 0.81 for industrial costs (excluding feedstock costs). The experience curve of total production costs results in a PR of 0.80. Cost breakdowns of sugarcane production show that all sub-processes contributed to the total, but that increasing yields have been the main driving force. Industrial costs mainly decreased because of increasing scales of the ethanol plants. Total production costs at present are approximately 340 US$/methanol3 (16 US$/GJ). Based on the experience curves for feedstock and industrial costs, total ethanol production costs in 2020 are estimated between US$ 200 and 260/m3 (9.4–12.2 US$/GJ). We conclude that using disaggregated experience curves for feedstock and industrial processing costs provide more insights into the factors that lowered costs in the past, and allow more accurate estimations for future cost developments.

The utilization of acid-tolerant bacteria on ethanol production from kitchen garbage

In order to achieve ethanol production from kitchen garbage under non-sterilized fermentation, the acid-tolerant Zymomonas mobilis named GZNS1 was selected and applied in the fermentation system. Ethanol production from kitchen garbage under non-sterilized fermentation with GZNS1 was proved to be feasible. The utilization of control strain and acid-tolerant strain under different conditions demonstrated that the sequence of ethanol yield was followed: sterilized garbage with control strain inoculated under pH of 6 (52 g/L) ≈ sterilized garbage with GZNS1 inoculated under pH of 4 (48 g/L) > non-sterilized garbage with GZNS1 inoculated under pH of 4 (46 g/L). Furthermore, the distillery waste during fermentation was adopted to recycle fermentation and acquired 50 g/L ethanol, higher than those adjusted with tap water. The utilization of acid-tolerant bacteria combing with the utilization of distillery waste associated with the process can increase ethanol production, save energy and reduce the cost of ethanol production.

Woody biomass availability for bioethanol conversion in Mississippi

Abstract This study evaluated woody biomass from logging residues, small-diameter trees, mill residues, and urban waste as a feedstock for cellulosic ethanol conversion in Mississippi. The focus on Mississippi was to assess in-state regional variations and provide specific information of biomass estimates for those facilities interested in locating in Mississippi. Supply and cost of four woody biomass sources were derived from Forest Inventory Analysis (FIA) information, a recent forest inventory conducted by the Mississippi Institute for Forest Inventory, and primary production costs. According to our analysis, about 4.0 million dry tons of woody biomass are available for production of up to 1.2 billion liters of ethanol each year in Mississippi. The feedstock consists of 69% logging residues, 21% small-diameter trees, 7% urban waste, and 3% mill residues. Of the total, 3.1 million dry tons (930 million liters of ethanol) can be produced for $34 dry ton−1 or less. Woody biomass from small-diameter trees is more expensive than other sources of biomass. Transportation costs accounted for the majority of total production costs. A sensitivity analysis indicates that the largest impacts in production costs of ethanol come from stumpage price of woody biomass and technological efficiency. These results provide a valuable decision support tool for resource managers and industries in identifying parameters that affect resource magnitude, type, and location of woody biomass feedstocks in Mississippi.

Understanding the reductions in US corn ethanol production costs: An experience curve approach

The US is currently the world's largest ethanol producer. An increasing percentage is used as transportation fuel, but debates continue on its costs competitiveness and energy balance. In this study, technological development of ethanol production and resulting cost reductions are investigated by using the experience curve approach, scrutinizing costs of dry grind ethanol production over the timeframe 1980–2005. Cost reductions are differentiated between feedstock (corn) production and industrial (ethanol) processing. Corn production costs in the US have declined by 62% over 30 years, down to 100$ 2005/tonne in 2005, while corn production volumes almost doubled since 1975. A progress ratio (PR) of 0.55 is calculated indicating a 45% cost decline over each doubling in cumulative production. Higher corn yields and increasing farm sizes are the most important drivers behind this cost decline. Industrial processing costs of ethanol have declined by 45% since 1983, to below 130$ 2005/m 3 in 2005 (excluding costs for corn and capital), equivalent to a PR of 0.87. Total ethanol production costs (including capital and net corn costs) have declined approximately 60% from 800$ 2005/m 3 in the early 1980s, to 300$ 2005/m 3 in 2005. Higher ethanol yields, lower energy use and the replacement of beverage alcohol-based production technologies have mostly contributed to this substantial cost decline. In addition, the average size of dry grind ethanol plants increased by 235% since 1990. For the future it is estimated that solely due to technological learning, production costs of ethanol may decline 28–44%, though this excludes effects of the current rising corn and fossil fuel costs. It is also concluded that experience curves are a valuable tool to describe both past and potential future cost reductions in US corn-based ethanol production.

Metabolic engineering of a thermophilic bacterium to produce ethanol at high yield

We report engineering Thermoanaerobacterium saccharolyticum, a thermophilic anaerobic bacterium that ferments xylan and biomass-derived sugars, to produce ethanol at high yield. Knockout of genes involved in organic acid formation (acetate kinase, phosphate acetyltransferase, and L-lactate dehydrogenase) resulted in a strain able to produce ethanol as the only detectable organic product and substantial changes in electron flow relative to the wild type. Ethanol formation in the engineered strain (ALK2) utilizes pyruvate:ferredoxin oxidoreductase with electrons transferred from ferredoxin to NAD(P), a pathway different from that in previously described microbes with a homoethanol fermentation. The homoethanologenic phenotype was stable for >150 generations in continuous culture. The growth rate of strain ALK2 was similar to the wild-type strain, with a reduction in cell yield proportional to the decreased ATP availability resulting from acetate kinase inactivation. Glucose and xylose are co-utilized and utilization of mannose and arabinose commences before glucose and xylose are exhausted. Using strain ALK2 in simultaneous hydrolysis and fermentation experiments at 50 degrees C allows a 2.5-fold reduction in cellulase loading compared with using Saccharomyces cerevisiae at 37 degrees C. The maximum ethanol titer produced by strain ALK2, 37 g/liter, is the highest reported thus far for a thermophilic anaerobe, although further improvements are desired and likely possible. Our results extend the frontier of metabolic engineering in thermophilic hosts, have the potential to significantly lower the cost of cellulosic ethanol production, and support the feasibility of further cost reductions through engineering a diversity of host organisms.

Dow and DOE to invest in biomass-toethanol process

Bio-ethanol has received considerable attention as a basic chemical and fuel additive. Bio-ethanol is presently produced from sugar/starch materials, but can also be produced from lignocellulosic biomass via hydrolysis-fermentation route or thermo-chemical route. In terms of thermo-chemical route, a few pilot plants ranging from 0.3 to 67 MW have been built and operated for alcohols synthesis. However, commercial success has not been found. In order to realize cost-competitive commercial ethanol production from lignocellulosic biomass through thermo-chemical pathway, a techno-economic analysis needs to be done. In this paper, a thermo-chemical process is designed, simulated and optimized mainly with ASPEN Plus. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost. Calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built around 200 MW. Cost-competitive ethanol production can be realized with efficient equipments, optimized operation, cost-effective syngas cleaning technology, inexpensive raw material with low pretreatment cost, high performance catalysts, off-gas and methanol recycling, optimal systematic configuration and heat integration, and high value byproduct.

Alternative Transportation Fuels: Distribution Infrastructure for Hydrogen and Ethanol in Iowa

Ethanol and hydrogen are receiving considerable attention as alternative fuels for transportation. They are being promoted to reduce greenhouse gas emissions and improve U.S. energy independence. This paper analyzes pipeline, rail, and truck distribution options for alternative fuels using the state of Iowa as a test case. By completely switching to E85 (85% ethanol, 15% gasoline) in Iowa, local ethanol production could replace 80% of gasoline use. Likewise, hydrogen derived from steam methane reforming at 7 facilities could replace all gasoline usage in the state. At 2006 gasoline prices, vehicles fueled with E85 would have comparable or lower fuel costs. The costs of hydrogen at the pump for both gas and liquid delivery are higher than those for gasoline and the ethanol scenarios. There are strong economies of scale in distribution paths, so a major shift to alternative fuels is needed to achieve the most cost effective distribution methods modeled in this analysis. There is considerable uncertainty in the cost estimates, particularly for the production costs of cellulosic ethanol, feedstock costs for hydrogen production, and the future price of petroleum.

Effect of biomass species and plant size on cellulosic ethanol: A comparative process and economic analysis

Abstract The effects of five different biomass species and their chemical composition on the overall process efficiency and economic performance considering feedstock availability and feedstock costs to manufacture ethanol from lignocellulose were studied. First is a comparison of ethanol production and excess electricity generated between different biomass species. Results show that, at the same feedstock rate of 2000 Mg day −1 , aspen wood has larger ethanol production than switchgrass, hybrid poplar and corn stover, while the excess electricity generated is as follows in increasing order: aspen The effects of plant size analysis showed that the estimated feedstock delivered costs, ethanol production, excess electricity generated and solid and gaseous waste emissions all increase with plant size for the various biomass species. The ethanol production costs decrease with the increase in plant size with optimal plant sizes for corn stover in the range from 2000 dry Mg day −1 to 4000 dry Mg day −1 .

Recent process improvements for the ammonia fiber expansion (AFEX) process and resulting reductions in minimum ethanol selling price

The ammonia fiber expansion (AFEX) process has been shown to be an effective pretreatment for lignocellulosic biomass. Technological advances in AFEX have been made since previous cost estimates were developed for this process. Recent research has enabled lower overall ammonia requirements, reduced ammonia concentrations, and reduced enzyme loadings while still maintaining high conversions of glucan and xylan to monomeric sugars. A new ammonia recovery approach has also been developed. Capital and operating costs for the AFEX process, as part of an overall biorefining system producing fuel ethanol from biomass have been developed based on these new research results. These new cost estimates are presented and compared to previous estimates. Two biological processing options within the overall biorefinery are also compared, namely consolidated bioprocessing (CBP) and enzymatic hydrolysis followed by fermentation. Using updated parameters and ammonia recovery configurations, the cost of ethanol production utilizing AFEX is calculated. These calculations indicate that the minimum ethanol selling price (MESP) has been reduced from $1.41/gal to $0.81/gal.

Sugarcane energy use: The Cuban case

Abstract This paper examines the history, methods, costs, and future prospects of Cuba's attempts to develop the energy potential of sugarcane. An overview of the main factors affecting the current sugarcane agro-industry in Cuba is provided, along with an analysis of why, despite attempts by the Cuban government to revive the country's sugarcane agro-industry, the industry continues to decline. The prevailing conditions and degree of modernization in Cuban sugar factories are evaluated. The sugar-agro industry's main production bottlenecks are studied. The fall in sugarcane yield from 57.5 ton/ha in 1991 to 22.4 ton/ha in 2005 and its relation to land use is explained. The socio-economic impact of the sugarcane agro-industry's downsizing is assessed. The governmental and quasi-governmental entities in charge of sugarcane energy use development and the country's legal framework are analyzed. The Cuban sugarcane agro-industry's opportunities in the growing international biofuels and bioenergy market are evaluated. To situate Cuba within the global bioenergy market, international best practices relating to the production and commercialization of biofuels are examined to determine the degree to which these experiences can be transferred to Cuba. The analysis of the Cuba sugar industry's biofuel potential is based on a comparative technical–economic assessment of three possible production scenarios: (1) the current situation, where only sugar is produced; (2) simultaneous production of sugar–anhydrous ethanol; and (3) production of sugar–ethanol and simultaneous generation of surplus electricity exported to a public grid. Some of the key assumptions underlying these analyses are as follows: Ethanol production and operation costs for a 7000 ton/day-sugar mill are estimated to be 0.25 and 0.23 USD/l, respectively. The influence of gasoline prices on sugar–ethanol production is also assessed. The kWh production and operation costs starting from sugarcane bagasse are estimated at 0.06 and 0.04 USD, respectively. Cuba's potential sugarcane cogeneration capacity is estimated to be 9006 GWh/year. Investment–profit analyses are offered for two scenarios: annexing a 300,000 l/day distillery to a sugar mill, and enlarging the cogeneration capacity of a 7000 ton/day mill. Added production cost/added-value analysis was carried out. The main environmental issues associated with sugarcane-based fuel production are also analyzed.

Adsorption of Water and Ethanol by Biomaterials

To develop cost-effective biomaterials for efficient ethanol concentration from an ethanol-water mixture through adsorption is crucial to reduce the production cost of ethanol. In the present work, barley straw demonstrated the higher water uptake and the higher molar ratio of water to ethanol uptake compared to the wheat straw and crab shells. Important factors affecting water adsorption including particle size of barley straw, water concentration and contact time were examined. The water adsorption isotherm was well simulated by Toth equation. The results showed that the barley straw is a potential biomaterial for removing water from ethanol-water mixtures.

Cellulosic biomass feedstocks and logistics for ethanol production

AbstractThe economic competitiveness of cellulosic ethanol production is highly dependent on feedstock cost, which constitutes 35–50% of the total ethanol production cost, depending on various geographical factors and the types of systems used for harvesting, collecting, preprocessing, transporting, and handling the material. Consequently, as the deployment of cellulosic ethanol biorefineries approaches, feedstock cost and availability are the driving factors that influence pioneer biorefinery locations and will largely control the rate at which this industry grows. Initial scenarios were postulated to develop a pioneer dry feedstock supply system design case as a demonstration of the current state of technology. Based on this pioneer design, advanced scenarios were developed to determine key cost barriers, needed supply system improvements, and technology advancements to achieve government and private sector cost targets. Analysis of the pioneer supply system resulted in a delivered feedstock cost to the throat of the pretreatment reactor of $37.00 per dry tonne (2002 $). Pioneer supply systems will start by using current infrastructure and technologies and be individually designed for biorefineries using specific feedstock types and varieties based on local geographic conditions. As the industry develops and cost barriers are addressed, the supply systems will incorporate advanced technologies that will eliminate downstream diversity and provide a uniform, tailored feedstock for multiple biorefineries located in different regions. Published in 2007 by John Wiley & Sons, Ltd.

Energy considerations for a SSF-based softwood ethanol plant

Ethanol can be produced from softwood by steam pretreatment followed by simultaneous saccharification and fermentation (SSF). However, the final ethanol concentration in the SSF step is usually rather low (around 4 wt%) and as a result the energy demand in the downstream processing will be high. In an effort to reduce the energy consumption various alternatives for the downstream processing part of the process were evaluated from a technical-economic standpoint. With experimental data as a basis, the whole process was modelled using the commercial flowsheeting program Aspen Plus. The results were used in the subsequent economic evaluation, which was performed using Icarus process evaluator. A base case configuration, consisting of three thermally coupled distillation columns and multiple-effect evaporation was established. For a feed containing 3.5% ethanol (w/w) to the distillation step, the overall process demand for steam was estimated to be 19.0 MJ/L ethanol and the ethanol production cost 4.14 SEK/L (0.591 USD/L). Different alternatives were considered, such as integration of a stripper with the evaporation step, increasing the number of evaporation effects and the application of mechanical vapour recompression to the evaporation step. Replacement of evaporation with anaerobic digestion was also considered. Among these alternatives, evaporation using mechanical vapour recompression and the anaerobic digester alternative both resulted in significantly lower energy demand than the base case, 10.2 and 9.8 MJ/L, respectively, and productions costs of 3.82 (0.546 USD/L) and 3.84 SEK/L (0.549 USD/L).

Low-Temperature Processing of Wheat for Bioethanol Production: Part I. Studies on the Use of Commercial Enzymes

The uncertainty of fossil fuel reserves, volatility of oil prices, and increasing release of carbon dioxide and other pollutants into the environment have led to a growing interest in the production of fuel ethanol. Research on bioethanol production has focused on all phases of the process, from raw materials to by-product recovery, and is directed toward improving the efficiency of fermentation and reducing the cost of ethanol production. However, there is still great scope for developing an efficient and inexpensive production process for bioethanol. This article describes a production process for bioethanol using wheat as a feedstock. This process was developed following analysis of mashing parameters such as wheat inclusion rate, pH, temperature, and exogenous enzyme choice. Further work showed that cooking the wheat was not required and that the process of backsetting benefited fermentation. These results have allowed the development of a proposed low-cost production process that will be of use in Northern Europe.

Ethanol Production: Energy and Economic Issues Related to U.S. and Brazilian Sugarcane

This analysis employs the most recent scientific data for the U.S. and for Brazil sugarcane production and the fermentation/distillation. These two countries were selected because they are the two largest countries in the world producing ethanol. All current fossil energy inputs used in the entire process of producing ethanol from sugarcane were included to determine the entire energy cost for ethanol production. Additional costs to consumers, including federal and state subsidies, plus costs of environmental pollution and/or degradation associated with the entire production system are discussed. The economic and the broad human food supply issues are evaluated. In addition, other studies are compared.

Ethanolic fermentation of hydrolysates from ammonia fiber expansion (AFEX) treated corn stover and distillers grain without detoxification and external nutrient supplementation

External nutrient supplementation and detoxification of hydrolysate significantly increase the production cost of cellulosic ethanol. In this study, we investigated the feasibility of fermenting cellulosic hydrolysates without washing, detoxification or external nutrient supplementation using ethanologens Escherichia coli KO11 and the adapted strain ML01 at low initial cell density (16 mg dry weight/L). The cellulosic hydrolysates were derived from enzymatically digested ammonia fiber expansion (AFEX)-treated corn stover and dry distiller's grain and solubles (DDGS) at high solids loading (18% by weight). The adaptation was achieved through selective evolution of KO11 on hydrolysate from AFEX-treated corn stover. All cellulosic hydrolysates tested (36-52 g/L glucose) were fermentable. Regardless of strains, metabolic ethanol yields were near the theoretical limit (0.51 g ethanol/g consumed sugar). Volumetric ethanol productivity of 1.2 g/h/L was achieved in fermentation on DDGS hydrolysate and DDGS improved the fermentability of hydrolysate from corn stover. However, enzymatic hydrolysis and xylose utilization during fermentation were the bottlenecks for ethanol production from corn stover at these experimental conditions. In conclusion, fermentation under the baseline conditions was feasible. Utilization of nutrient-rich feedstocks such as DDGS in fermentation can replace expensive media supplementation.

Screening for sugar and ethanol processing characteristics from anatomical fractions of wheat stover

Abstract Due to concerns with stover collection systems, soil sustainability, and processing costs to produce ethanol, there are opportunities to investigate the optimal plant fractions to collect. Wheat stover fractions were separated by hand and analyzed for glucan, xylan, acid-soluble lignin, acid-insoluble lignin, and ash composition. Internodes had the highest glucan content (38.2% zero percent moisture basis) and the other fractions varied between 29.9% and 33.4%. The stover fractions were pretreated with either 0%, 0.4%, or 0.8% NaOH for 2 h at room temperature, washed, autoclaved, and saccharified. In addition, acid pretreated samples underwent simultaneous saccharification and fermentation (SSF) to ethanol. In general, the acid and alkaline pretreatments produced similar trends with leaves requiring very little pretreatment to achieve high conversion rates (greater than 80%). Chaff responded very well to pretreatment and high conversion efficiencies resulted when pretreated under alkaline or acidic conditions. Nodes and internodes were more recalcitrant than the other anatomical fractions. Pretreatment with 0.8% sulfuric acid (0.24 g sulfuric acid/g biomass) did not result in a significantly higher conversion of glucan to ethanol as the native material. Pretreatment with 0.8% NaOH (0.06 g NaOH/g biomass) at room temperature for 2 h resulted in high conversion efficiencies for all plant fractions, greater than 73% of the available glucan. These differences in pretreatment susceptibilities suggest that a biomass collection system that removes specific portions of wheat stover could result in significant differences in ethanol production costs.

Process Design and Optimization of Novel Wheat‐Based Continuous Bioethanol Production System

A novel design of a wheat-based biorefinery for bioethanol production, including wheat milling, gluten extraction as byproduct, fungal submerged fermentation for enzyme production, starch hydrolysis, fungal biomass autolysis for nutrient regeneration, yeast fermentation with recycling integrated with a pervaporation membrane for ethanol concentration, and fuel-grade ethanol purification by pressure swing distillation (PSD), was optimized in continuous mode using the equation-based software General Algebraic Modelling System (GAMS). The novel wheat biorefining strategy could result in a production cost within the range of dollars 0.96-0.50 gal(-1) ethanol (dollars 0.25-0.13 L(-1) ethanol) when the production capacity of the plant is within the range of 10-33.5 million gal y(-1) (37.85-126.8 million L y(-1)). The production of value-added byproducts (e.g., bran-rich pearlings, gluten, pure yeast cells) was identified as a crucial factor for improving the economics of fuel ethanol production from wheat. Integration of yeast fermentation with pervaporation membrane could result in the concentration of ethanol in the fermentation outlet stream (up to 40 mol %). The application of a PSD system that consisted of a low-pressure and a high-pressure column and employing heat integration between the high- and low-pressure columns resulted in reduced operating cost (up to 44%) for fuel-grade ethanol production.

Studies on cellulosic ethanol production for sustainable supply of liquid fuel in China

As the biggest developing country, China faces a serious challenge in satisfying its need for huge amounts of energy resources, especially for liquid fuel. The Chinese government has recently started a bioethanol project, and has produced about 1 million tons of ethanol fuel from corn and wheat in 2005. As it has the largest population in the world and limited lands for food production, cellulosic ethanol would be a more suitable choice for China. Many research projects in China on biodegradation and biotransformation of lignocellulosics have been carried out. Furthermore, understanding the biodegradation mechanism of lignocellulosics and developing practical processes for ethanol production have been ongoing. After more than 30 years of research, several pilot scale facilities have been set up, and lots of experience has been acquired. However, the calculated production cost of cellulosic ethanol is still higher than that of corn ethanol. To overcome this problem, the biorefinery conception has been introduced into research on lignocellulosics transformation. A corncob biorefinery process has been developed in Shandong University. By combining the cellulase and ethanol production with a xylose-related products production, the total production cost can be reduced. A scale of 50,000-ton/year cellulosic ethanol biorefinery is being planned to be built at Yucheng.

Biofuels for transport in developing countries: socioeconomic considerations

The manufacture of biofuels for use in transportation can be commercially viable in developing countries. However, the conditions under which this can occur without long-term government support are likely to be limited. In the near term, ethanol production from sugarcane offers the best chance of commercial viability, with Brazil demonstrating that it can produce ethanol competitively with gasoline. This article discusses some of the underlying conditions needed for other developing countries to benefit from the Brazilian experience and move down the ethanol production cost curve. Where a domestic biofuel program requires sustained government support, the article considers possible justifications for government interventions in biofuel manufacture, including rural development, externalities, and energy source diversification.