Ethanol Production Cost Research Articles

Influence of feedstock selection on cellulosic ethanol production based on densified biomass with calcium hydroxide and regular steam pretreatment

Feedstock selection is a key factor affecting the process of cellulosic ethanol production. Densifying lignocellulosic biomass with chemicals (calcium hydroxide) followed by regular steam autoclave (DLCA(ch)) is an emerging and efficient pretreatment technology. In this study, different crop straws were selected as feedstock in a DLCA(ch) based process for cellulosic ethanol production, and their experimental and economic performances were evaluated. Both single crop straws and mixed crop straws were used and compared as feedstock for DLCA(ch) based biorefinery. Among single crop straws of corn stover, rice straw and wheat straw, wheat straw had the highest ethanol yield and the lowest feedstock cost, with a minimum ethanol selling price of 2.03 $/gal ethanol considering a 10 % internal rate of return and a 2000 tons crop straw per day biorefinery scale. When mixed crop straws were used as the feedstock, both feedstock cost and ethanol production cost were further reduced, and the minimum ethanol selling price was reduced to 2.02 $/gal ethanol. In addition, the use of mixed crop straws has great potential for large scale DLCA(ch) based process for cellulosic ethanol production.

Techno-enviro-economic analysis of second-generation bioethanol at plant-scale by different pre-treatments of biomass from palm oil waste

This study evaluates three pathways: supercritical water treatment (SCW), CO2-water (scCO2-H2O), and catalytic hydrothermal hydrolysis (CHH) to produce second-generation bioethanol using palm tree fronds (PTF) as feedstock. The analysis focuses on technical performances using process simulation with Aspen Plus™, environmental evaluation by applying a Life Cycle Assessment (LCA) framework and an economic analysis using the levelized cost. The results of the technical performances reveal CHH as the best pathway for bioethanol production, with the highest ethanol yield at 273 L/tonne dry PTF and a substantial NER of 2.2, outperforming SCW and scCO2-H2O. From an environmental evaluation, CHH reveals lower carbon footprints of 61 g CO2 per MJ. Economically, CHH is competitive, with an ethanol production cost of1.11 $/L, comparable to the enzymatic hydrolysis process. These findings provide the technical, environmental, and economic aspects of a promising route for lignocellulosic bioethanol production while suggesting pathways for further optimisation for future research.

Silencing ScGUX2 reduces xylan glucuronidation and improves biomass saccharification in sugarcane.

There is an increasing need for renewable energy sources to replace part of our fossil fuel-based economy and reduce greenhouse gas emission. Sugarcane bagasse is a prominent feedstock to produce cellulosic bioethanol, but strategies are still needed to improve the cost-effective exploitation of this potential energy source. In model plants, it has been shown that GUX genes are involved in cell wall hemicellulose decoration, adding glucuronic acid substitutions on the xylan backbone. Mutation of GUX genes increases enzyme access to cell wall polysaccharides, reducing biomass recalcitrance in Arabidopsis thaliana. Here, we characterized the sugarcane GUX genes and silenced GUX2 in commercial hybrid sugarcane. The transgenic lines had no penalty in development under greenhouse conditions. The sugarcane GUX1 and GUX2 enzymes generated different patterns of xylan glucuronidation, suggesting they may differently influence the molecular interaction of xylan with cellulose and lignin. Studies using biomass without chemical or steam pretreatment showed that the cell wall polysaccharides, particularly xylan, were less recalcitrant in sugarcane with GUX2 silenced than in WT plants. Our findings suggest that manipulation of GUX in sugarcane can reduce the costs of second-generation ethanol production and enhance the contribution of biofuels to lowering the emission of greenhouse gases.

Techno‐economic learning in biorefinery research; a meta‐level perspective of three exemplary cases

AbstractThe production of liquid fuels and chemicals from biomass is an essential part of establishing a bioeconomy. Numerous techno‐economic studies have been published on different pathways for processing biomass. To examine the progress made in this field, a meta‐analysis investigating three exemplary biobased products was conducted. Using recently published techno‐economic studies, the (average) unit production costs for biodiesel, cellulosic ethanol and kraft lignin were investigated. Findings in this study are based on an understanding of two phenomena: economies of scale and the learning effect. Economies of scale can be observed for each case, with kraft lignin extraction indicating the greatest cost advantages and the production of biodiesel the smallest. The investigation of potential learning effects revealed by the data yielded unexpected results: In two out of three cases, the calculated average unit production cost was observed to increase over time. These results contradict the expected influence of learning effects on calculated unit production costs as these did not decrease over time for a specific technology. A closer investigation of processing pathways and feedstocks shows that a diversification in research has occurred over the last three decades. Different driving forces of innovation related to the investigated products are also identified.

Evaluation of Saccharomyces cerevisiae Improved Strains Potential in the Bioethanol Production from Bagasse

Plant biomass can be utilized to produce bioethanol, because they are abundantly available in nature. The cost of ethanol production from lignocellulosic materials is relatively high with low yield. But this can be solved by strain improvement processes. This study is aimed at evaluate bioethanol production potential of improved strains of Saccharomyces cerevisiae developed through random mutagenesis. Bagasse was hydrolysed with 1% NaOH and 1.0M H2SO4 respectively for five days. The hydrolysed bagasse was saccharified using Aspergillus niger isolated from soil samples. Saccharomyces cerevisiae isolated from locally produced wines; sorghum (burukutu) oil palm wine (emu) and raphia palm wine (oguro) with the highest ethanol production (5.0g/ml) were used, and then treated with physical mutagen (ultraviolet light) and chemical mutagens (Acridine dye, Bromo acetaldehyde, dithiothreitol, Ketoconazole and Nitrous acid) respectively to develop mutant with high ethanol producing efficiency under varied operational parameters. Three mutant strains of Saccharomyces cerevisiae namely;- SUV, SCD and SCK produced higher volumes of ethanol (7.5 g/ml, 9.8 g/ml, 11.2 g/ml respectively). SCD and SCK were able to grow at 25% ethanol concentration indicating that they had higher ethanol tolerance ability than the other strains. The optimum temperature and pH for ethanol production by all the strains were 350C and 6.0 respectively. The improved strains of Saccharomyces cerevisiae developed through random mutation techniques had produced more ethanol from the bagasse than the wild-type.

Technoeconomic analysis of a fungal pretreatment-based cellulosic ethanol production

Cellulosic biomass shows great potential as feedstock for bioethanol production. Despite clear benefits in terms of greenhouse gas mitigation and bioproduct potential, the commercial production of cellulosic ethanol remains economically challenging at the current state of technology. This paper presents a technoeconomic analysis of a fungal pretreatment-based cellulosic ethanol plant with a processing capacity of 2000 tonnes of switchgrass per day. The production process model was designed and simulated using SuperPro Designer. The plant's ethanol yield, capital investment per unit capacity, and unit ethanol production cost were estimated to be 211.90 L/t of switchgrass, $ 3.60/L, and $ 1.44/L of ethanol, respectively. Fungal pretreatment was the major contributor (72%) to the total capital investment, mainly due to the large quantity of equipment required in the process. A positive net present value (NPV) was generated for the baseline model at ethanol selling price of $ 1.50/L, which increased by 5-fold for 80% glucose yield. Glucose yield was the most sensitive to NPV for all the process parameters evaluated.

Investigation of the use of wet ethanol in an HCCI engine using water injection and direct exhaust heat recovery

Wet ethanol is a renewable fuel that has great potential to reduce the energy cost of ethanol production and improve the life-cycle carbon footprint of ethanol. The use of wet ethanol in homogeneous charge compression ignition (HCCI) mode can achieve high efficiency with low emission levels. In this context, this study investigates the effects of water-in-ethanol concentration on the performance, emissions, and combustion characteristics of an HCCI engine using water injection and recirculation of all exhaust gasses from a diesel cylinder. Water injection was used to solve the problem that there is no direct method to adjust HCCI combustion. Results showed that water–ethanol blends with higher water content had lower heat release rates and combustion temperatures, which increased the combustion duration. The indicated efficiency deteriorated for ethanol–water blends with high water concentrations. However, the highest indicated efficiency was 39.3% for the blend with 20% water by vol. at 6.0 bar. CO and organic gas emissions tended to increase with late combustion and for blends with higher water content, reaching values of 78.0 and 68.2 g/kWh at 4.0 bar, respectively. On the other hand, the NOX emissions were low, reaching a maximum value of 0.93 g/kWh in the HCCI combustion.

Modification of cellulase with smart-green polymers to promote low-cost and cleaner production of cellulosic ethanol

Cellulosic ethanol produced using the enzymatic method is promising; however, developing an efficient and green cellulase hydrolysis system to cut the cost of cellulosic ethanol and promote cleaner biofuel production remains challenging. Herein, based on the fact that multiple hydrogen bond can be generated between poly (methyl acrylic acid-co-acrylic acid) and gelatin, cellulase was first covalently bonded to the copolymer and then mixed with gelatin, to endow the cellulase with ideal upper critical solution temperature (UCST). As a result, the affinity between cellulase and the substrate did not decrease significantly after the modification (the Km value of modified cellulase (4.62 g/L) was not significantly different from that of free cellulase (4.55 g/L)). The enzymes can be switched on-demand between free state (above 36 °C), enabling high hydrolysis reactivity for insoluble substrates such as paper or corn stalks, and fixed state (at 4 °C), facilitating enzymes separation and reuse (the modified cellulase still has 58.2% of its initial activity for 20 batches). Thus, the cost of cellulosic ethanol production could be significantly reduced in the precondition of high catalytic efficiency. Furthermore, the system presents nontoxic and biodegradable properties. The system can be completely degraded in soil after 7 days and the inhibition rate of the degraded products on luminescent bacteria was only 2%, which can promote cleaner cellulosic biofuel production.

Enhancing Biofuel Production Through Nanoparticle-assisted Fermentation: A Comparative Study

Nanoparticles have many applications in various fields, including biofuel technology, and rising demands for energy and increased harmful environmental impacts of fossil fuel have increasing interest towards biofuel as an alternative eco-friendly source of energy and ethanol blended petrol. The production of ethanol from agricultural waste (rice straw) and banana plant residue with biological approach is an important step toward energy sustainability and in minimizing greenhouse gases emissions. A promising approach, the use of nanoparticles to assist fermentation. The process enhances biofuel production by incorporation of nanoparticles in fermentation process. The purpose of this research paper is to explore the application of nanoparticle-assisted fermentation for enhanced biofuel production. This study explains the process of ethanol production by Saccharomyces cerevisiae in the presence of NiO and Fe3O4 nanoparticles. This study investigates the Comparative analysis of cost and yield production of ethanol production through the fermentation with and without Nanoparticles. The outcomes of this research offer valuable insights into how employing nanoparticles to assist fermentation can strengthen the process and potentially drive advancements in biofuel technologies.

Multifunctional landscapes for dedicated bioenergy crops lead to low-carbon market-competitive biofuels

Switchgrass is a promising feedstock for cellulosic biorefineries, due to its ability to maintain comparatively high biomass yields across a wide range of soil and climatic conditions. However, there is an incomplete understanding of the economic and environmental tradeoffs associated with cultivating switchgrass on low-productivity land for conversion to biofuels. This study surveys prior literature and demonstrates a new integrated assessment framework, including agroecosystem, ecosystem services valuation, technoeconomic, and life-cycle assessment models, to quantify and contextualize the economic and environmental impacts of switchgrass cultivation on marginal land with downstream conversion to biofuels. Monetizing and incorporating the value of ecosystem services, such as improved water quality benefits from nitrate and sediment reductions, climate change mitigation benefits from CO2 emission reduction, and recreational and pollination benefits from increased biodiversity, the modeled multifunctional landscape reduces the ethanol production cost by 33.3–58.9 cents/l-gasoline-equivalent ($1.3–2.2/gge). Planting switchgrass in low productivity land improves soil health, resulting in the carbon footprint reduction credit of 12.8–20.2 gCO2e/MJ. For an improved switchgrass-to-ethanol conversion pathway with the maximum benefits from ecosystem services, the minimum ethanol selling price and carbon footprint of ethanol, respectively, could reach to 31 cents/l-gasoline-equivalent (47% reduction relative to average gasoline price) and 3 gCO2e/MJ (97% reduction relative to gasoline). This low carbon renewable ethanol leads to substantial State and/or Federal policy incentives (∼$1/l-gasoline-equivalent) providing a large benefit to biorefinery operators, farmers, and the public as a whole.

Technoeconomic Analysis of Ethanol Production from Corn Stover without Solid–Liquid Separation and Detoxification

Water and chemical overconsumption is one of the technical challenges for cellulosic ethanol production. To address this issue, a facile process, where Ca(OH)2-pretreated corn stover slurry is subjected to pH adjusting with H2SO4 for ethanol fermentation by C6 (scenario I) or C6/C5 (scenario II) yeast, is proposed. This study demonstrates its experimental feasibility for ethanol production without solid–liquid separation and detoxification, thus effectively reducing the consumption of water and chemicals. Technoeconomic analysis shows that total capital investment ranges from $127.86 million to $134.82 million with a production capacity of 90 Mt/h for 7920 h annually. Raw material (43.22–44.62%) and utility (35.49–37.23%) costs play important roles in annual operating costs. The pretreatment and fermentation section contributes $2.12/gal for scenario I and $1.61/gal for scenario II to the net unit production cost of ethanol. The ethanol minimum selling prices (MSP) of $4.01/gal for scenario I and $3.16/gal for scenario II are reached with an internal rate of return of 10%. Sensitivity analyses indicate that the costs of corn stover and water for cooling are the dominant elements affecting ethanol MSP.

Cellulosic Ethanol Production Using a Dual Functional Novel Yeast.

Reducing the cost of cellulosic ethanol production, especially for cellulose hydrolytic enzymes, is vital to growing a sustainable and efficient cellulosic ethanol industry and bio-based economy. Using an ethanologenic yeast able to produce hydrolytic enzymes, such as Clavispora NRRL Y-50464, is one solution. NRRL Y-50464 is fast-growing and robust, and tolerates inhibitory compounds 2-furaldehyde (furfural) and 5-hydroxymethyl-2-furaldehyde (HMF) associated with lignocellulose-to-fuel conversion. It produces three forms of β-glucosidase isozymes, BGL1, BGL2, and BGL3, and ferment cellobiose as the sole carbon source. These β-glucosidases exhibited desirable enzyme kinetic parameters and high levels of enzyme-specific activity toward cellobiose and many oligosaccharide substrates. They tolerate the product inhibition of glucose and ethanol, and are stable to temperature and pH conditions. These characteristics are desirable for more efficient cellulosic ethanol production by simultaneous saccharification and fermentation. NRRL Y-50464 provided the highest cellulosic ethanol titers and conversion rates at lower cellulase loadings, using either pure cellulose or agricultural residues, as so far reported in the literature. This review summarizes NRRL Y-50464 performance on cellulosic ethanol production from refined cellulose, rice straw, and corn stover processed in various ways, in the presence or absence of furfural and HMF. This dual functional yeast has potential to serve as a prototype for the development of next-generation biocatalysts. Perspectives on continued strain development and process engineering improvements for more efficient cellulosic ethanol production from lignocellulosic materials are also discussed.

The dairy biorefinery: Integrating treatment process for Tunisian cheese whey valorization

In order to set up a cost-efficient biorefinery in a Tunisian dairy industry, the production unit effluents are recovered. The main objective is to develop an optimum method for the production of bioethanol from whey. An energy analysis as well as environmental and economic analyses are performed for a bioethanol production plant. Four production scenarios are examined in order to determine the most provident as well as the less polluting ones. The process and cost models were developed using SuperPro Designer software which a simulation program that is able to estimate both process and economic parameters. This software uses energy and mass balances. The model can be used to assess the efficiency, the resources consumption, the profitability and the environmental impact of each scenario. The results demonstrate that the third scenario, in which a reverse osmosis procedure is added to concentrate the whey, a continuous stoichiometric reaction procedure is integrated to model the biotransformation in the fermenter and where streams are added in order to recycle the biomass, produces the highest amount of bioethanol with 1.65 MT/year but the second one (where no streams were added) is the most profitable one with revenues as high as 570 000 $/year. The corresponding cost of ethanol production is 0.271 US $ ethanol per liter. The net present value (NPV) and the return on investment (ROI) of each scenario are positive. Such result indicates that all these investments could be undertaken in order to find an eco-friendly issue for the dairy industry effluents. Cheese whey could serve as an alternative raw material for producing ethanol.

Lowering whole cost for sugarcane‐based ethanol production by engineered Zymomonas mobilis

AbstractLowering cost will prompt the sustainable development of sugarcane‐based ethanol industry. In this work, we developed a low‐cost process for ethanol production from sugarcane by a genetically engineered Zymomonas mobilis. Fermentation media were first optimized, resulting in a 15.54% increase in ethanol fermentation efficiency as compared to control media. To further reduce the byproduct levan formation, a levansucrase‐encoding gene of Z. mobilis, sacB, was deleted through the type I‐F CRISPR‐Cas system, which resulted in a further elevation of both ethanol conversion ratio and productivity comparing with the starting strain ZMS912 (87.50% vs. 76.77%, 1.95 g/L/h vs. 1.71 g/L/h). Moreover, we conducted fed‐batch fermentation for ethanol production using sugarcane juice in 5 L bioreactors and employing the optimized media and engineered strain. The results showed that maximum ethanol titer of 81.59 g/L and productivity of 5.83 g/L/h were achieved. Finally, preliminary techno‐economic assessment demonstrated that our efforts to modify media and strain could reduce the processing cost of ethanol production from sugarcane juice, which provides the feasibility for economic ethanol production in the future.

Process layout evaluation in the production of ethanol fuel

Due to depletion of petroleum reserves and environmental impact of fossil fuels, an alternative solution is introduced in form of ethanol fuels. Ethanol fuels have promising potential in the transport sector and in the generation of electricity. In addition, very few researches highlighted the production electricity cost of ethanol fuel for the transportation sector. Therefore, this study will focuses on finding the effective process layout in the production of ethanol fuel. The first main objective of this research is to simulate the layout of ethanol fuel plant using DELMIA QUEST software. The second objective is to determine the most efficient process layout in the production of ethanol fuel. The layout of ethanol fuel plant was simulated and the most efficient layout in terms of ethanol production was suggested from the simulation. At the end of this research, the efficient process layout is highlighted between the dry mill and wet mill process layout. It was found that dry mill layout offers lower electricity cost for ethanol production.

Effects of Water Ratio in Hydrous Ethanol on the Combustion and Emissions of a Hydrous Ethanol/Gasoline Combined Injection Engine under Different Excess Air Ratios.

Ethanol is usually combined with gasoline to manufacture ethanol–gasoline with excellent combustion characteristics. However, extracting water from hydrous ethanol to manufacture anhydrous ethanol consumed much energy, which increases the production cost of ethanol–gasoline. Many researchers have studied the combustion and emissions of hydrous ethanol–gasoline to explore the application of hydrous ethanol–gasoline as the fuel for spark-ignition engines. Most previous studies changed the hydrous ethanol ratio with fixed purity in hydrous ethanol–gasoline to study the effects of hydrous ethanol. Different from previous studies, this paper studied the effects of water ratio (Wr) in hydrous ethanol on the combustion and emissions of a hydrous ethanol/gasoline combined injection engine under different excess air ratio (λ) values. The ratios of ethanol and gasoline keep constant, while the purity of hydrous ethanol changes during the research. The experiment adopted the combined injection mode with hydrous ethanol direct injection plus gasoline port injection; the direct injection ratio was 20%. The experiment set three λ (0.9, 1, and 1.2) and five Wrs (0, 5, 10, 15, and 20%). The test engine’s speed was 1500 rpm, and the intake manifold absolute pressure was 48 kPa. Results showed that water inhibited combustion, prolonged CA 0-10 and CA 10-90, reduced Pmax and Tmax, and delayed APmax; larger λ made the deterioration on combustion more obvious, and the smaller λ had a larger tolerance to water. Water could increase torque and improve emissions, but different parameters corresponded to different optimal Wrs. For torque, the optimal Wr was 5%. For HC emissions, the optimal Wr was 0%; for CO emissions, the optimal value was 5%; and for NOx emissions, the best value was 20%. The best Wr was 10% for particle number (PN) emissions. Under the optimal Wr condition, when λ values were 0.9, 1, and 1.2, compared with pure gasoline, the torque increased by 7.5, 5.54, and 5.31%; HC emissions decreased by 21.37, 23.43, and 26.58%; NOx emissions decreased by 4.26, 11.47, and 12.55%; CO emissions decreased by 17.51, 34.56, −50%; and the total PN emissions decreased by 87.64, 89.64, and 76.07%.

Process design and techno-economic analysis of 2′-fucosyllactose enriched distiller’s dried grains with solubles production in dry grind ethanol process using genetically engineered Saccharomyces cerevisiae

2′-fucosyllactose (2′-FL) has been linked positively with piglet gut health. Genetically engineered Saccharomyces cerevisiae strains producing 2′-FL can be used in the dry grind process to enrich Distiller’s dried grains with solubles (DDGS) with 2′-FL and supplement swine diets with 2′-FL. The objectives of our study were to modify dry grind ethanol process for 2′-FL enriched DDGS production and evaluate the techno-economic feasibility of the process. Concentrations of 19.8 g 2′-FL/kg dry DDGS were achieved in the dry grind process using engineered strain without negatively affecting the ethanol yield. Process models for conventional and modified dry grind processes producing 2′-FL enriched DDGS (1150 MT corn/day capacity) were developed using SuperPro Designer. Capital and ethanol production costs for modified dry grind processes were higher than the conventional process. The internal rate of return for the modified processes was higher than the conventional process for $300/MT 2′-FL enriched DDGS selling price.

Emerging Synergies on the Co-treatment of Spent Coffee Grounds and Brewer’s Spent Grains for Ethanol Production

Purpose Given that the depletion of fossil fuels is an important issue that should be tackled urgently, alternative routes are being sought for biofuels production. This paper, under this context, studied the potential synergies of co-treatment of two kinds of agro-waste (brewers’ spent grains, BSG and spent coffee grounds, SCG) towards the direction of biodiesel and bioethanol production, alleviating at the same time their treatment and management issues. Methods The technical feasibility of oil extraction and ethanol production was studied and optimized in both laboratory and bench scale. A treatment train including alkaline pretreatment of SCG and dilute acid pretreatment of BSG, neutralization of the solutions by mixing them, enzymatic saccharification and ethanolic fermentation led to the production of bioethanol. Results The co-treatment of BSG and SCG proved beneficial and optimum experimental conditions were defined by setting the bioethanol production cost as optimization parameter. The lowest ethanol production cost (3.9€/kg) was observed for scenario 4 (SCG/BSG mixture, chemical pretreatment (0.5 N, 5 h), enzymatic hydrolysis (400 µL/g cellulose, 16 h)) and scenario 5 (SCG/BSG mixture, chemical pretreatment (0.5 N, 5 h), enzymatic hydrolysis (800 µL/g cellulose, 5 h)). Further upscaling of the process verified the technical feasibility of process units leading to a further increase of ethanol yield and thus a decrease in the production cost. Conclusions Conclusively, it was demonstrated that the recovery and extraction of the oil content of BSG and SCG and the achievement of high ethanol yields is technically feasible. Within this context, an integrated biorefinery was presented, making evident that these substrates could reverse the eminent energy crisis via biofuels production. Graphic Abstract

Toward co-optimization of renewable fuel blend production and combustion in ultra-high efficiency SI engines

The shift from fossil to renewable fuels presents an opportunity to tailor a fuel’s molecular structure and composition to the needs of advanced internal combustion engine concepts, while simultaneously aiming for economic and sustainable fuel production. We have recently proposed a method for computer-aided design of tailor-made fuels that integrates aspects of both product and production pathway design. The present paper sets out to sequentially combine that method with experimental investigation on a single cylinder research engine and model-based early-stage process evaluation to create, validate, and benchmark a rationally designed multi-component biofuel for highly boosted spark-ignition engines. To this end, the computer-aided design approach is applied to a network of possible fuel components and their production pathways. The resulting optimal four-component fuel EBCC (50 mol% ethanol, 21 mol% 2-butanone, 15 mol% cyclopentane, and 14 mol% cyclopentanone) is analyzed with regard to combustion performance and estimated fuel production cost. Variations of both the indicated mean effective pressure and the relative air/fuel ratio were performed on an engine equipped with a compression ratio of 14.7. EBCC achieves indicated efficiencies that are significantly higher than those of RON 102 gasoline fuel and comparable to those of pure 2-butanone, an extremely knock-resistant fuel identified in a previous round of model-based fuel design. Furthermore, a strong reduction in engine-out soot emissions is observed compared to RON 102 gasoline. Early-stage process evaluation shows EBCC to have lower estimated fuel production costs than 2-butanone. Production costs of pure ethanol, however, are estimated to be even lower, mainly due to lower plant investment costs and a synthesis pathway that does not require hydrogen. The paper concludes with a brief perspective on further integration of the proposed sequential approach with the goal of co-optimizing the production and combustion of renewable fuel blends.

Techno-economic assessment of bioethanol production from lignocellulose by consortium-based consolidated bioprocessing at industrial scale

Lignocellulose-based biofuels are of major importance to mitigate the impact of international traffic and transport on climate change while sustaining agricultural land for food supply. Highly integrated systems like consolidated bioprocessing (CBP), where enzyme production, enzymatic hydrolysis and fermentation of the released sugars are carried out in one reactor, offer the highest potential to save costs and to make lignocellulose-based biofuels economically competitive. The work described here showed that CBP based on a microbial consortium operated at full-scale (2000 t/d) saves up to 27.5 % of the total ethanol production costs compared to conventional ethanol production from lignocellulose in individual process steps. The cost savings are mainly achieved through lower CAPEX due to less apparatus requirements because of the integrated process, as well as through lower OPEX since no glucose is needed for enzyme production. A comparison with literature estimations of cost savings of CBP based on genetically modified microorganisms results in approximately the same range. As a result of a detailed sensitivity analysis, scale and yield were identified as the main cost-pushers from a process point of view, whereas the price level of the plant location has the highest impact on the investment conditions. In the EU, CBP yields enough margin for profitable production and the possibility to decentralize biomass valorization, whereas in the world’s largest ethanol market, the U.S, profitable production of lignocellulosic ethanol can only be achieved by CBP combined with other cost saving techniques, such as utilization of cost-free waste feedstocks, since ethanol has undergone a considerable price slump.