TJ
T. Jankovic
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23 records found
1
Journal article
(2026)
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Gijs J.A. Brouwer, Tamara Janković, John A. Posada, Adrie J.J. Straathof, Anton A. Kiss
This study advances the development of syngas fermentation by presenting the first industrial-scale process design for producing isopropanol (IPA) and acetone from steel mill off-gas, with a total production capacity of 46–50 ktonne per year. The process was rigorously developed in Aspen Plus, with a comprehensive techno-economic assessment and life-cycle analysis performed to evaluate the process performance. The developed process maximizes energy efficiency by utilizing the heat content of steel off-gas and implementing advanced heat pump systems. As a result, the process is thermally self-sufficient and can operate solely on renewable electricity. Efficient utilization of waste gases results in substantial reductions in global warming potential compared with petrochemical-based production (144–160% for IPA and 138–149% for acetone). The unit production cost of 0.58–0.74 $/kgIPA/Ac and potential profit margins of 49–65% testify to the cost-effectiveness of the developed process. These findings demonstrate the environmental and economic sustainability of syngas fermentation from steel mill off-gas, establishing it as a potentially viable alternative to conventional petrochemical processes. This technology may hold great potential in reducing environmental impacts and carbon emissions in industrial chemical production.
...
This study advances the development of syngas fermentation by presenting the first industrial-scale process design for producing isopropanol (IPA) and acetone from steel mill off-gas, with a total production capacity of 46–50 ktonne per year. The process was rigorously developed in Aspen Plus, with a comprehensive techno-economic assessment and life-cycle analysis performed to evaluate the process performance. The developed process maximizes energy efficiency by utilizing the heat content of steel off-gas and implementing advanced heat pump systems. As a result, the process is thermally self-sufficient and can operate solely on renewable electricity. Efficient utilization of waste gases results in substantial reductions in global warming potential compared with petrochemical-based production (144–160% for IPA and 138–149% for acetone). The unit production cost of 0.58–0.74 $/kgIPA/Ac and potential profit margins of 49–65% testify to the cost-effectiveness of the developed process. These findings demonstrate the environmental and economic sustainability of syngas fermentation from steel mill off-gas, establishing it as a potentially viable alternative to conventional petrochemical processes. This technology may hold great potential in reducing environmental impacts and carbon emissions in industrial chemical production.
Journal article
(2025)
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Mungyu Lee, Tamara Jankovic, Francisco Caparrós-Salvador, Ludovic Jourdin, Adrie J.J. Straathof
Carbon dioxide utilization is a key strategy for sustainable chemical production and climate change mitigation. Microbial electrosynthesis (MES) offers a promising approach to convert CO₂ into organic acids and multi‑carbon compounds, but its industrial application requires improved product recovery methods. In this study, we developed an integrated MES-sorption-distillation system for the recovery of pure hexanoic acid. Adsorption experiments identified conditions for C6-selective capture from C2–C6 carboxylate mixtures typically produced from MES. Subsequent desorption using CO₂ expanded methanol enriched hexanoic acid concentration by 13-fold compared to the aqueous feed, achieving 67 % recovery in a single pass, but 100 % overall, since recirculation of unrecovered carboxylates back to the MES reactor is proposed. This recirculation will enhance chain elongation, eliminate loss of unrecovered carboxylates, and reduce the need for external pH control during MES. Distillation of the desorbed mixture led to streams of pure products and reusable solvent, without losses. Notably, 87 % of the total energy demand for product formation is attributed to the MES stage, where electrical energy is directly supplied as electrons to drive microbial production. Thus, MES with the proposed recovery method enables pure hexanoic acid production with minimal losses of materials or energy and potentially allows the system to operate in a carbon-negative manner.
...
Carbon dioxide utilization is a key strategy for sustainable chemical production and climate change mitigation. Microbial electrosynthesis (MES) offers a promising approach to convert CO₂ into organic acids and multi‑carbon compounds, but its industrial application requires improved product recovery methods. In this study, we developed an integrated MES-sorption-distillation system for the recovery of pure hexanoic acid. Adsorption experiments identified conditions for C6-selective capture from C2–C6 carboxylate mixtures typically produced from MES. Subsequent desorption using CO₂ expanded methanol enriched hexanoic acid concentration by 13-fold compared to the aqueous feed, achieving 67 % recovery in a single pass, but 100 % overall, since recirculation of unrecovered carboxylates back to the MES reactor is proposed. This recirculation will enhance chain elongation, eliminate loss of unrecovered carboxylates, and reduce the need for external pH control during MES. Distillation of the desorbed mixture led to streams of pure products and reusable solvent, without losses. Notably, 87 % of the total energy demand for product formation is attributed to the MES stage, where electrical energy is directly supplied as electrons to drive microbial production. Thus, MES with the proposed recovery method enables pure hexanoic acid production with minimal losses of materials or energy and potentially allows the system to operate in a carbon-negative manner.
The butanediols (BDOs), 2,3-, 1,4- and 1,3-butanediol, are platform chemicals that are mainly produced from fossil hydrocarbons but may be obtained through fermentation. However, low product concentration, by-product formation and high boiling temperatures of BDOs hinder downstream processing and increase overall fermentation costs. This study increases the competitiveness of industrial biotechnology by designing a large-scale process (broth processing capacity of 160 ktonne/y) for the final purification of BDOs after fermentation (recovery >99 %). It includes an initial preconcentration step in a vacuum distillation column to remove most water and light impurities. The initial removal of most of the water and the use of a heat pump system allowed significant energy reduction. At the heart of the process is an integrated dividing-wall column that can efficiently purify BDO from the remaining light and heavy impurities. Moreover, a single process design was proven effective in purifying different BDOs to > 99.4 wt%. This was cost-effective (total purification costs of 0.208 – 0.243 $/kgBDO) and energy-efficient (with primary energy requirements of 1.854 – 2.176 kWthh/kgBDO). The proposed purification sequence can be used for each BDO type, which offers flexibility in developing sustainable bioprocesses for BDO production.
...
The butanediols (BDOs), 2,3-, 1,4- and 1,3-butanediol, are platform chemicals that are mainly produced from fossil hydrocarbons but may be obtained through fermentation. However, low product concentration, by-product formation and high boiling temperatures of BDOs hinder downstream processing and increase overall fermentation costs. This study increases the competitiveness of industrial biotechnology by designing a large-scale process (broth processing capacity of 160 ktonne/y) for the final purification of BDOs after fermentation (recovery >99 %). It includes an initial preconcentration step in a vacuum distillation column to remove most water and light impurities. The initial removal of most of the water and the use of a heat pump system allowed significant energy reduction. At the heart of the process is an integrated dividing-wall column that can efficiently purify BDO from the remaining light and heavy impurities. Moreover, a single process design was proven effective in purifying different BDOs to > 99.4 wt%. This was cost-effective (total purification costs of 0.208 – 0.243 $/kgBDO) and energy-efficient (with primary energy requirements of 1.854 – 2.176 kWthh/kgBDO). The proposed purification sequence can be used for each BDO type, which offers flexibility in developing sustainable bioprocesses for BDO production.
Fermentation can be used to obtain a wide variety of valuable high-boiling components. Among these components, microorganisms can produce aliphatic diols (e.g. propanediols, butanediols, etc.) in significant concentrations (e.g. 5–15 wt.%). Nonetheless, the high boiling points of these components, presence of microorganisms, and formation of by-products complicate recovery after fermentation. Hence, this perspective offers valuable insights into downstream processing options. A novel methodology was developed for recovering high-boiling components from dilute aqueous solutions, whereby both light and heavy impurities are present. The main steps in the proposed methodology are heat pump-assisted preconcentration and final purification in a dividing-wall column. These steps allow effective separation of high-purity product from water, light and heavy impurities. Furthermore, processes for recovery of 1,3-propanediol, 2,3-, 1,4- and 1,3-butanediol, designed according to the proposed methodology, were compared. Downstream processing performance is mainly determined by the product concentration in the fermentation broth, but is also influenced by the amount of impurities in the broth.
...
Fermentation can be used to obtain a wide variety of valuable high-boiling components. Among these components, microorganisms can produce aliphatic diols (e.g. propanediols, butanediols, etc.) in significant concentrations (e.g. 5–15 wt.%). Nonetheless, the high boiling points of these components, presence of microorganisms, and formation of by-products complicate recovery after fermentation. Hence, this perspective offers valuable insights into downstream processing options. A novel methodology was developed for recovering high-boiling components from dilute aqueous solutions, whereby both light and heavy impurities are present. The main steps in the proposed methodology are heat pump-assisted preconcentration and final purification in a dividing-wall column. These steps allow effective separation of high-purity product from water, light and heavy impurities. Furthermore, processes for recovery of 1,3-propanediol, 2,3-, 1,4- and 1,3-butanediol, designed according to the proposed methodology, were compared. Downstream processing performance is mainly determined by the product concentration in the fermentation broth, but is also influenced by the amount of impurities in the broth.
BACKGROUND
2-Phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEAc) are valuable aroma compounds with growing market demands. As an alternative to conventional petrochemical production, more valuable natural forms of these chemicals can be obtained by biotransformation. Low product concentrations, resulting from significant product toxicity to microorganisms, and high boiling points of products complicate recovery process. In situ product recovery by liquid–liquid extraction can be used to increase bioprocess yield and productivity. However, the subsequent purification of 2-PE and 2-PEAc is challenging as a consequence of the multiple phases, high-boiling temperatures of main products, occurrence of remaining substrate and byproducts, and presence of microorganisms.
RESULTS
The main goal of this original work is to improve the competitiveness of the biotechnological production of 2-PE by using in silico methods to develop an advanced industrial process for the final purification after centrifugation. An adaptable dividing-wall column was designed to remove 2-PE with 2-PEAc from organic phase or to esterify 2-PE to pure 2-PEAc. The production flexibility of the developed process allows adjustability to market demand. Additionally, recovery of co-produced ethanol from aqueous phase can increase the economic and environmental performance of the developed process. As confirmed by detailed techno-economic analysis, the proposed processes can cost-effectively (total recovery costs of 0.64–0.72 US$/kg2-PE/2-PEAc) and energy-efficiently (primary energy requirements of 1.83–2.05 kWthh/kg2-PE/2-PEAc) recovery of 2-PE or 2-PEAc after biotransformation.
CONCLUSION
The developed process enhances economic and environmental viability of biotechnological 2-PE production by reducing costs and energy requirements, while ensuring flexibility to adapt to market demands. ...
2-Phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEAc) are valuable aroma compounds with growing market demands. As an alternative to conventional petrochemical production, more valuable natural forms of these chemicals can be obtained by biotransformation. Low product concentrations, resulting from significant product toxicity to microorganisms, and high boiling points of products complicate recovery process. In situ product recovery by liquid–liquid extraction can be used to increase bioprocess yield and productivity. However, the subsequent purification of 2-PE and 2-PEAc is challenging as a consequence of the multiple phases, high-boiling temperatures of main products, occurrence of remaining substrate and byproducts, and presence of microorganisms.
RESULTS
The main goal of this original work is to improve the competitiveness of the biotechnological production of 2-PE by using in silico methods to develop an advanced industrial process for the final purification after centrifugation. An adaptable dividing-wall column was designed to remove 2-PE with 2-PEAc from organic phase or to esterify 2-PE to pure 2-PEAc. The production flexibility of the developed process allows adjustability to market demand. Additionally, recovery of co-produced ethanol from aqueous phase can increase the economic and environmental performance of the developed process. As confirmed by detailed techno-economic analysis, the proposed processes can cost-effectively (total recovery costs of 0.64–0.72 US$/kg2-PE/2-PEAc) and energy-efficiently (primary energy requirements of 1.83–2.05 kWthh/kg2-PE/2-PEAc) recovery of 2-PE or 2-PEAc after biotransformation.
CONCLUSION
The developed process enhances economic and environmental viability of biotechnological 2-PE production by reducing costs and energy requirements, while ensuring flexibility to adapt to market demands. ...
BACKGROUND
2-Phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEAc) are valuable aroma compounds with growing market demands. As an alternative to conventional petrochemical production, more valuable natural forms of these chemicals can be obtained by biotransformation. Low product concentrations, resulting from significant product toxicity to microorganisms, and high boiling points of products complicate recovery process. In situ product recovery by liquid–liquid extraction can be used to increase bioprocess yield and productivity. However, the subsequent purification of 2-PE and 2-PEAc is challenging as a consequence of the multiple phases, high-boiling temperatures of main products, occurrence of remaining substrate and byproducts, and presence of microorganisms.
RESULTS
The main goal of this original work is to improve the competitiveness of the biotechnological production of 2-PE by using in silico methods to develop an advanced industrial process for the final purification after centrifugation. An adaptable dividing-wall column was designed to remove 2-PE with 2-PEAc from organic phase or to esterify 2-PE to pure 2-PEAc. The production flexibility of the developed process allows adjustability to market demand. Additionally, recovery of co-produced ethanol from aqueous phase can increase the economic and environmental performance of the developed process. As confirmed by detailed techno-economic analysis, the proposed processes can cost-effectively (total recovery costs of 0.64–0.72 US$/kg2-PE/2-PEAc) and energy-efficiently (primary energy requirements of 1.83–2.05 kWthh/kg2-PE/2-PEAc) recovery of 2-PE or 2-PEAc after biotransformation.
CONCLUSION
The developed process enhances economic and environmental viability of biotechnological 2-PE production by reducing costs and energy requirements, while ensuring flexibility to adapt to market demands.
2-Phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEAc) are valuable aroma compounds with growing market demands. As an alternative to conventional petrochemical production, more valuable natural forms of these chemicals can be obtained by biotransformation. Low product concentrations, resulting from significant product toxicity to microorganisms, and high boiling points of products complicate recovery process. In situ product recovery by liquid–liquid extraction can be used to increase bioprocess yield and productivity. However, the subsequent purification of 2-PE and 2-PEAc is challenging as a consequence of the multiple phases, high-boiling temperatures of main products, occurrence of remaining substrate and byproducts, and presence of microorganisms.
RESULTS
The main goal of this original work is to improve the competitiveness of the biotechnological production of 2-PE by using in silico methods to develop an advanced industrial process for the final purification after centrifugation. An adaptable dividing-wall column was designed to remove 2-PE with 2-PEAc from organic phase or to esterify 2-PE to pure 2-PEAc. The production flexibility of the developed process allows adjustability to market demand. Additionally, recovery of co-produced ethanol from aqueous phase can increase the economic and environmental performance of the developed process. As confirmed by detailed techno-economic analysis, the proposed processes can cost-effectively (total recovery costs of 0.64–0.72 US$/kg2-PE/2-PEAc) and energy-efficiently (primary energy requirements of 1.83–2.05 kWthh/kg2-PE/2-PEAc) recovery of 2-PE or 2-PEAc after biotransformation.
CONCLUSION
The developed process enhances economic and environmental viability of biotechnological 2-PE production by reducing costs and energy requirements, while ensuring flexibility to adapt to market demands.
The rapid rise in global energy demands has accelerated the depletion of fossil fuel reserves, raising significant concerns about long-term energy security. Beyond resource exhaustion, this growing dependency on fossil fuels has contributed to severe environmental pollution and climate change, leading to strict environmental regulations. Consequently, extensive research efforts have been devoted to developing methods for producing a wide range of platform chemicals from renewable sources. In that respect, industrial biotechnology holds significant potential to replace fossil fuel-dependent production of various chemicals. Nonetheless, improvements in the fermentation and downstream processing are often necessary to enhance the competitiveness of large-scale bioprocesses. Significant research efforts have been put into genetic engineering to improve microorganisms’ performance and optimization of the fermentation process. However, downstream processing after fermentation has not been nearly as promptly addressed. A common limitation of the fermentation processes is the inhibition of microbial production by the products themselves which limits achievable product concentrations in the broth (often <10 wt%). Additionally, the formation of by-products and the presence of microorganisms complicate recovery process after fermentation. Consequently, downstream processing costs may significantly contribute to the total production costs (20-40% for the bulk biochemicals).
Process systems engineering is essential in developing competitive (bio)chemical processes, as it integrates process design and simulation in biotechnology. Hence, this thesis aims to advance industrial biotechnology by developing advanced, large-scale downstream processes for the recovery of fermentation products such as alcohols, diols, esters, carboxylic acids, and aromatic compounds. A systematic approach to downstream process development was undertaken through multiple case studies that were organized into chapters based on the characteristics of the primary product being recovered. Aspen Plus software was used as a computer aided process engineering tool for process design. Various process intensification techniques (e.g. dividing-wall column and reactive distillation), heat integration and heat pumping were studied to reduce energy requirements and decrease total process costs. The performance of the developed processes was assessed through economic analysis and the evaluation of key sustainability metrics, including energy requirements, greenhouse gas emissions, water consumption, water losses, and toxic materials and pollutants intensity.
Chapter 2 focuses on designing downstream processing strategies tailored for low-boiling alcohols produced through fermentation, including ethanol, isopropanol, isobutanol, and hexanol. Since these products are sufficiently volatile, the end-product inhibition can be mitigated by continuously removing the product from the broth using a distillation-based loop around the bioreactor. Heat pump-assisted vacuum distillation was demonstrated as an effective method for initial product recovery from the broth. Additionally, a novel pass-through distillation process was designed specifically for ethanol recovery. This innovative technique separates the evaporation and condensation parts of distillation by introducing an absorption-desorption loop between them. As a result, these operations can be conducted at different pressures, allowing the use of inexpensive cooling utilities while maintaining mild evaporation temperatures. Furthermore, a hybrid approach combining gas stripping with heat pump-assisted vacuum evaporation was developed for the recovery of isobutanol from fermentation broth. In all cases, the initial separation of the product from most of the broth under reduced pressure lowers the operational temperature, making it possible to reuse the remaining broth along with the microorganisms. This may improve fermentation performance by avoiding biomass loss, increasing substrate-to-product yield and reducing water requirements. Following this initial step, a preconcentration step using heat pump-assisted atmospheric distillation was carried out to remove most of the remaining water. The final purification method depended on the properties of the target product. Ethanol and isopropanol, which form homogeneous azeotropes with water, were purified using extractive distillation with ethylene glycol. In contrast, isobutanol and hexanol, which form heterogeneous azeotropes, were purified through a combination of simple distillation and liquid-liquid phase separation. Furthermore, a general methodology for recovering volatile alcohols from fermentation broths was developed and the performance of downstream processing was compared for the recovery of ethanol, isopropanol, isobutanol, and hexanol. Due to the higher hydrophobicity of longer-chain alcohols, their concentrations in the fermentation broth tend to be lower (e.g. 6.14 wt% for ethanol, 5.00 wt% for isopropanol, 1.61 wt% for isobutanol, and 0.24 wt% for hexanol). More dilute fermentation broths result in higher processing costs (0.08, 0.11, 0.16, and 0.53 $/kg, respectively) and increased energy requirements (0.96, 1.35, 2.02 and 3.07 kWthh/kg, respectively) of the downstream processing. Finally, it was concluded that the primary factor influencing downstream processing efficiency is the achievable product concentration in the fermentation broth, rather than the alcohol chain length.
Chapter 3 focuses on developing recovery processes for aliphatic diols that can be produced through fermentation, including 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol. Due to their high boiling points, simple distillation is unsuitable for separating these compounds from the fermentation broth. Instead, initial separation steps are required to remove biomass, as well as large organic and inorganic molecules. These initial steps result in a clarified, desalted solution, which then undergoes further treatment through preconcentration and final purification. Since these final two steps contribute significantly to overall purification costs due to their high energy requirements, this research focuses on enhancing them to improve the efficiency of downstream processing for aliphatic diols. The preconcentration step was designed to remove most of water along with some light impurities using a heat pump-assisted vacuum distillation. The final purification step, which separates high-purity diol from residual light and heavy impurities, was effectively carried out in a dividing wall column. Furthermore, a general methodology for recovering high boiling components from dilute aqueous solutions was developed. Recovery processes for 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol, designed according to this methodology, were compared. The performance of downstream processing was primarily determined by the product concentration in the fermentation broth, though the presence of impurities also played a significant role. Nonetheless, in all cases, the proposed methodology enabled the cost effective (total recovery costs of 0.29-0.70 $/kg) and energy-efficient (primary energy requirements of 1.35-2.01 kWthh/kg) recovery of valuable propanediol and butanediol from dilute aqueous solutions (7.0-10.0 wt%). Lastly, adaptable process design offers the possibility of using a single process configuration to produce various aliphatic diols depending on the market demand.
Chapter 4 discusses the development of recovery processes for various organic chemicals produced through different biotechnology-based processes, such as ethyl acetate, propionic acid, 2-phenylethanol, acetic acid, furfural, etc. While these processes differ due to the unique properties of each compound, they all rely on distillation as a primary recovery method. It was employed as the main separation technique to efficiently recover propionic, acetic, and succinic acids from dilute aqueous solutions. An adaptable dividing-wall column design was demonstrated to effectively recover propionic and acetic acids or perform esterification with methanol to recover methyl-propionate and methyl-acetate (total recovery costs of 0.40-0.47 $/kg). Distillation was also utilized as the primary technique in the recovery of ethyl acetate. Due to its high volatility, most of the ethyl acetate is separated in the fermenter off-gas. Consequently, product recovery was carried out from both the vapor and liquid phases, with an azeotropic dividing-wall column used effectively for final purification (total recovery costs of 0.61-1.09 $/kg). Furthermore, distillation-based downstream processing was effectively used for the solvent recovery and final purification of 2-phenylethanol after in-situ product recovery by liquid-liquid extraction. An adaptable azeotropic dividing-wall column was designed to recover high-purity 2-phenylethanol or perform esterification and recover 2-phenylethyl acetate (total recovery costs of 0.64-0.73 $/kg). Lastly, a sequence of distillation steps was developed to recover by-products (acetic acid, formic acid, furfural, 5-hydroxymethyl furfural) from the lignocellulosic biomass pretreatment process using liquid hot water (total recovery costs of 0.78 $/kg). This process could enhance the competitiveness of lignocellulosic biorefineries by enabling the valorization of additional products.
Furthermore, this thesis emphasizes the importance of advancing both upstream and downstream processes simultaneously to ensure the competitiveness and viability of entire bioprocesses. While the primary focus of this research is on recovery process development, it serves as an initial step toward achieving that broader goal. Chapter 5 highlights the significance of integrating upstream and downstream processes in bioprocess development. Isopropanol, along with acetone, and 2-phenylethanol, were selected as representative examples of low boiling and high-boiling biochemicals. Large-scale bioprocesses for their production were designed to showcase the practical application of integrated process design. Isopropanol and acetone were produced through gas fermentation, with different combinations of products (isopropanol and acetone together or separately) considered. Previously developed advanced recovery processes, including heat pump-assisted vacuum distillation, followed by heat pump-assisted atmospheric distillation and extractive distillation, were employed. Detailed techno-economic analysis and life cycle assessments demonstrated competitive economic performance (total production costs of 0.57-0.74 $/kg) and reduced environmental impacts compared to fossil fuel-based production (reduced global warming potential by 138-160%). 2-phenylethanol was produced de-novo through fermentation from glucose. Two different in-situ product recovery processes were compared: liquid-liquid extraction using oleyl alcohol and product adsorption. In both cases, distillation-based separations were used to effectively recover the solvent and obtain high-purity 2-phenylethanol. Additionally, a sensitivity analysis was conducted to examine the influence of 2-phenylethanol concentration on total production costs. This analysis revealed that minimal costs were achieved at a concentration of 1.5 g/L, with concentrations above 1 g/L not resulting in a significant reduction in costs due to increased fermentation costs. Regardless of the used in-situ recovery technique, the developed processes for producing 2-phenylethanol were found to be highly cost-effective (total production costs of 9.03-9.40 $/kg).
Summarizing, this thesis illustrates the significant impact that advancements in downstream processing can have on overall process performance. Specifically, it supports the development of novel advanced separation processes, based on process intensification principles, which have received relatively limited attention in industrial biotechnology. These innovations can play a decisive role in determining the feasibility of bioprocesses for industrial scale applications. Furthermore, the importance of incorporating downstream processing at the early stages of developing biotechnology-based processes is highlighted. The findings presented in this thesis have the potential to drive progress in industrial biotechnology and contribute to the successful commercialization of biotechnology-based products.
...
Process systems engineering is essential in developing competitive (bio)chemical processes, as it integrates process design and simulation in biotechnology. Hence, this thesis aims to advance industrial biotechnology by developing advanced, large-scale downstream processes for the recovery of fermentation products such as alcohols, diols, esters, carboxylic acids, and aromatic compounds. A systematic approach to downstream process development was undertaken through multiple case studies that were organized into chapters based on the characteristics of the primary product being recovered. Aspen Plus software was used as a computer aided process engineering tool for process design. Various process intensification techniques (e.g. dividing-wall column and reactive distillation), heat integration and heat pumping were studied to reduce energy requirements and decrease total process costs. The performance of the developed processes was assessed through economic analysis and the evaluation of key sustainability metrics, including energy requirements, greenhouse gas emissions, water consumption, water losses, and toxic materials and pollutants intensity.
Chapter 2 focuses on designing downstream processing strategies tailored for low-boiling alcohols produced through fermentation, including ethanol, isopropanol, isobutanol, and hexanol. Since these products are sufficiently volatile, the end-product inhibition can be mitigated by continuously removing the product from the broth using a distillation-based loop around the bioreactor. Heat pump-assisted vacuum distillation was demonstrated as an effective method for initial product recovery from the broth. Additionally, a novel pass-through distillation process was designed specifically for ethanol recovery. This innovative technique separates the evaporation and condensation parts of distillation by introducing an absorption-desorption loop between them. As a result, these operations can be conducted at different pressures, allowing the use of inexpensive cooling utilities while maintaining mild evaporation temperatures. Furthermore, a hybrid approach combining gas stripping with heat pump-assisted vacuum evaporation was developed for the recovery of isobutanol from fermentation broth. In all cases, the initial separation of the product from most of the broth under reduced pressure lowers the operational temperature, making it possible to reuse the remaining broth along with the microorganisms. This may improve fermentation performance by avoiding biomass loss, increasing substrate-to-product yield and reducing water requirements. Following this initial step, a preconcentration step using heat pump-assisted atmospheric distillation was carried out to remove most of the remaining water. The final purification method depended on the properties of the target product. Ethanol and isopropanol, which form homogeneous azeotropes with water, were purified using extractive distillation with ethylene glycol. In contrast, isobutanol and hexanol, which form heterogeneous azeotropes, were purified through a combination of simple distillation and liquid-liquid phase separation. Furthermore, a general methodology for recovering volatile alcohols from fermentation broths was developed and the performance of downstream processing was compared for the recovery of ethanol, isopropanol, isobutanol, and hexanol. Due to the higher hydrophobicity of longer-chain alcohols, their concentrations in the fermentation broth tend to be lower (e.g. 6.14 wt% for ethanol, 5.00 wt% for isopropanol, 1.61 wt% for isobutanol, and 0.24 wt% for hexanol). More dilute fermentation broths result in higher processing costs (0.08, 0.11, 0.16, and 0.53 $/kg, respectively) and increased energy requirements (0.96, 1.35, 2.02 and 3.07 kWthh/kg, respectively) of the downstream processing. Finally, it was concluded that the primary factor influencing downstream processing efficiency is the achievable product concentration in the fermentation broth, rather than the alcohol chain length.
Chapter 3 focuses on developing recovery processes for aliphatic diols that can be produced through fermentation, including 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol. Due to their high boiling points, simple distillation is unsuitable for separating these compounds from the fermentation broth. Instead, initial separation steps are required to remove biomass, as well as large organic and inorganic molecules. These initial steps result in a clarified, desalted solution, which then undergoes further treatment through preconcentration and final purification. Since these final two steps contribute significantly to overall purification costs due to their high energy requirements, this research focuses on enhancing them to improve the efficiency of downstream processing for aliphatic diols. The preconcentration step was designed to remove most of water along with some light impurities using a heat pump-assisted vacuum distillation. The final purification step, which separates high-purity diol from residual light and heavy impurities, was effectively carried out in a dividing wall column. Furthermore, a general methodology for recovering high boiling components from dilute aqueous solutions was developed. Recovery processes for 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol, designed according to this methodology, were compared. The performance of downstream processing was primarily determined by the product concentration in the fermentation broth, though the presence of impurities also played a significant role. Nonetheless, in all cases, the proposed methodology enabled the cost effective (total recovery costs of 0.29-0.70 $/kg) and energy-efficient (primary energy requirements of 1.35-2.01 kWthh/kg) recovery of valuable propanediol and butanediol from dilute aqueous solutions (7.0-10.0 wt%). Lastly, adaptable process design offers the possibility of using a single process configuration to produce various aliphatic diols depending on the market demand.
Chapter 4 discusses the development of recovery processes for various organic chemicals produced through different biotechnology-based processes, such as ethyl acetate, propionic acid, 2-phenylethanol, acetic acid, furfural, etc. While these processes differ due to the unique properties of each compound, they all rely on distillation as a primary recovery method. It was employed as the main separation technique to efficiently recover propionic, acetic, and succinic acids from dilute aqueous solutions. An adaptable dividing-wall column design was demonstrated to effectively recover propionic and acetic acids or perform esterification with methanol to recover methyl-propionate and methyl-acetate (total recovery costs of 0.40-0.47 $/kg). Distillation was also utilized as the primary technique in the recovery of ethyl acetate. Due to its high volatility, most of the ethyl acetate is separated in the fermenter off-gas. Consequently, product recovery was carried out from both the vapor and liquid phases, with an azeotropic dividing-wall column used effectively for final purification (total recovery costs of 0.61-1.09 $/kg). Furthermore, distillation-based downstream processing was effectively used for the solvent recovery and final purification of 2-phenylethanol after in-situ product recovery by liquid-liquid extraction. An adaptable azeotropic dividing-wall column was designed to recover high-purity 2-phenylethanol or perform esterification and recover 2-phenylethyl acetate (total recovery costs of 0.64-0.73 $/kg). Lastly, a sequence of distillation steps was developed to recover by-products (acetic acid, formic acid, furfural, 5-hydroxymethyl furfural) from the lignocellulosic biomass pretreatment process using liquid hot water (total recovery costs of 0.78 $/kg). This process could enhance the competitiveness of lignocellulosic biorefineries by enabling the valorization of additional products.
Furthermore, this thesis emphasizes the importance of advancing both upstream and downstream processes simultaneously to ensure the competitiveness and viability of entire bioprocesses. While the primary focus of this research is on recovery process development, it serves as an initial step toward achieving that broader goal. Chapter 5 highlights the significance of integrating upstream and downstream processes in bioprocess development. Isopropanol, along with acetone, and 2-phenylethanol, were selected as representative examples of low boiling and high-boiling biochemicals. Large-scale bioprocesses for their production were designed to showcase the practical application of integrated process design. Isopropanol and acetone were produced through gas fermentation, with different combinations of products (isopropanol and acetone together or separately) considered. Previously developed advanced recovery processes, including heat pump-assisted vacuum distillation, followed by heat pump-assisted atmospheric distillation and extractive distillation, were employed. Detailed techno-economic analysis and life cycle assessments demonstrated competitive economic performance (total production costs of 0.57-0.74 $/kg) and reduced environmental impacts compared to fossil fuel-based production (reduced global warming potential by 138-160%). 2-phenylethanol was produced de-novo through fermentation from glucose. Two different in-situ product recovery processes were compared: liquid-liquid extraction using oleyl alcohol and product adsorption. In both cases, distillation-based separations were used to effectively recover the solvent and obtain high-purity 2-phenylethanol. Additionally, a sensitivity analysis was conducted to examine the influence of 2-phenylethanol concentration on total production costs. This analysis revealed that minimal costs were achieved at a concentration of 1.5 g/L, with concentrations above 1 g/L not resulting in a significant reduction in costs due to increased fermentation costs. Regardless of the used in-situ recovery technique, the developed processes for producing 2-phenylethanol were found to be highly cost-effective (total production costs of 9.03-9.40 $/kg).
Summarizing, this thesis illustrates the significant impact that advancements in downstream processing can have on overall process performance. Specifically, it supports the development of novel advanced separation processes, based on process intensification principles, which have received relatively limited attention in industrial biotechnology. These innovations can play a decisive role in determining the feasibility of bioprocesses for industrial scale applications. Furthermore, the importance of incorporating downstream processing at the early stages of developing biotechnology-based processes is highlighted. The findings presented in this thesis have the potential to drive progress in industrial biotechnology and contribute to the successful commercialization of biotechnology-based products.
...
The rapid rise in global energy demands has accelerated the depletion of fossil fuel reserves, raising significant concerns about long-term energy security. Beyond resource exhaustion, this growing dependency on fossil fuels has contributed to severe environmental pollution and climate change, leading to strict environmental regulations. Consequently, extensive research efforts have been devoted to developing methods for producing a wide range of platform chemicals from renewable sources. In that respect, industrial biotechnology holds significant potential to replace fossil fuel-dependent production of various chemicals. Nonetheless, improvements in the fermentation and downstream processing are often necessary to enhance the competitiveness of large-scale bioprocesses. Significant research efforts have been put into genetic engineering to improve microorganisms’ performance and optimization of the fermentation process. However, downstream processing after fermentation has not been nearly as promptly addressed. A common limitation of the fermentation processes is the inhibition of microbial production by the products themselves which limits achievable product concentrations in the broth (often <10 wt%). Additionally, the formation of by-products and the presence of microorganisms complicate recovery process after fermentation. Consequently, downstream processing costs may significantly contribute to the total production costs (20-40% for the bulk biochemicals).
Process systems engineering is essential in developing competitive (bio)chemical processes, as it integrates process design and simulation in biotechnology. Hence, this thesis aims to advance industrial biotechnology by developing advanced, large-scale downstream processes for the recovery of fermentation products such as alcohols, diols, esters, carboxylic acids, and aromatic compounds. A systematic approach to downstream process development was undertaken through multiple case studies that were organized into chapters based on the characteristics of the primary product being recovered. Aspen Plus software was used as a computer aided process engineering tool for process design. Various process intensification techniques (e.g. dividing-wall column and reactive distillation), heat integration and heat pumping were studied to reduce energy requirements and decrease total process costs. The performance of the developed processes was assessed through economic analysis and the evaluation of key sustainability metrics, including energy requirements, greenhouse gas emissions, water consumption, water losses, and toxic materials and pollutants intensity.
Chapter 2 focuses on designing downstream processing strategies tailored for low-boiling alcohols produced through fermentation, including ethanol, isopropanol, isobutanol, and hexanol. Since these products are sufficiently volatile, the end-product inhibition can be mitigated by continuously removing the product from the broth using a distillation-based loop around the bioreactor. Heat pump-assisted vacuum distillation was demonstrated as an effective method for initial product recovery from the broth. Additionally, a novel pass-through distillation process was designed specifically for ethanol recovery. This innovative technique separates the evaporation and condensation parts of distillation by introducing an absorption-desorption loop between them. As a result, these operations can be conducted at different pressures, allowing the use of inexpensive cooling utilities while maintaining mild evaporation temperatures. Furthermore, a hybrid approach combining gas stripping with heat pump-assisted vacuum evaporation was developed for the recovery of isobutanol from fermentation broth. In all cases, the initial separation of the product from most of the broth under reduced pressure lowers the operational temperature, making it possible to reuse the remaining broth along with the microorganisms. This may improve fermentation performance by avoiding biomass loss, increasing substrate-to-product yield and reducing water requirements. Following this initial step, a preconcentration step using heat pump-assisted atmospheric distillation was carried out to remove most of the remaining water. The final purification method depended on the properties of the target product. Ethanol and isopropanol, which form homogeneous azeotropes with water, were purified using extractive distillation with ethylene glycol. In contrast, isobutanol and hexanol, which form heterogeneous azeotropes, were purified through a combination of simple distillation and liquid-liquid phase separation. Furthermore, a general methodology for recovering volatile alcohols from fermentation broths was developed and the performance of downstream processing was compared for the recovery of ethanol, isopropanol, isobutanol, and hexanol. Due to the higher hydrophobicity of longer-chain alcohols, their concentrations in the fermentation broth tend to be lower (e.g. 6.14 wt% for ethanol, 5.00 wt% for isopropanol, 1.61 wt% for isobutanol, and 0.24 wt% for hexanol). More dilute fermentation broths result in higher processing costs (0.08, 0.11, 0.16, and 0.53 $/kg, respectively) and increased energy requirements (0.96, 1.35, 2.02 and 3.07 kWthh/kg, respectively) of the downstream processing. Finally, it was concluded that the primary factor influencing downstream processing efficiency is the achievable product concentration in the fermentation broth, rather than the alcohol chain length.
Chapter 3 focuses on developing recovery processes for aliphatic diols that can be produced through fermentation, including 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol. Due to their high boiling points, simple distillation is unsuitable for separating these compounds from the fermentation broth. Instead, initial separation steps are required to remove biomass, as well as large organic and inorganic molecules. These initial steps result in a clarified, desalted solution, which then undergoes further treatment through preconcentration and final purification. Since these final two steps contribute significantly to overall purification costs due to their high energy requirements, this research focuses on enhancing them to improve the efficiency of downstream processing for aliphatic diols. The preconcentration step was designed to remove most of water along with some light impurities using a heat pump-assisted vacuum distillation. The final purification step, which separates high-purity diol from residual light and heavy impurities, was effectively carried out in a dividing wall column. Furthermore, a general methodology for recovering high boiling components from dilute aqueous solutions was developed. Recovery processes for 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol, designed according to this methodology, were compared. The performance of downstream processing was primarily determined by the product concentration in the fermentation broth, though the presence of impurities also played a significant role. Nonetheless, in all cases, the proposed methodology enabled the cost effective (total recovery costs of 0.29-0.70 $/kg) and energy-efficient (primary energy requirements of 1.35-2.01 kWthh/kg) recovery of valuable propanediol and butanediol from dilute aqueous solutions (7.0-10.0 wt%). Lastly, adaptable process design offers the possibility of using a single process configuration to produce various aliphatic diols depending on the market demand.
Chapter 4 discusses the development of recovery processes for various organic chemicals produced through different biotechnology-based processes, such as ethyl acetate, propionic acid, 2-phenylethanol, acetic acid, furfural, etc. While these processes differ due to the unique properties of each compound, they all rely on distillation as a primary recovery method. It was employed as the main separation technique to efficiently recover propionic, acetic, and succinic acids from dilute aqueous solutions. An adaptable dividing-wall column design was demonstrated to effectively recover propionic and acetic acids or perform esterification with methanol to recover methyl-propionate and methyl-acetate (total recovery costs of 0.40-0.47 $/kg). Distillation was also utilized as the primary technique in the recovery of ethyl acetate. Due to its high volatility, most of the ethyl acetate is separated in the fermenter off-gas. Consequently, product recovery was carried out from both the vapor and liquid phases, with an azeotropic dividing-wall column used effectively for final purification (total recovery costs of 0.61-1.09 $/kg). Furthermore, distillation-based downstream processing was effectively used for the solvent recovery and final purification of 2-phenylethanol after in-situ product recovery by liquid-liquid extraction. An adaptable azeotropic dividing-wall column was designed to recover high-purity 2-phenylethanol or perform esterification and recover 2-phenylethyl acetate (total recovery costs of 0.64-0.73 $/kg). Lastly, a sequence of distillation steps was developed to recover by-products (acetic acid, formic acid, furfural, 5-hydroxymethyl furfural) from the lignocellulosic biomass pretreatment process using liquid hot water (total recovery costs of 0.78 $/kg). This process could enhance the competitiveness of lignocellulosic biorefineries by enabling the valorization of additional products.
Furthermore, this thesis emphasizes the importance of advancing both upstream and downstream processes simultaneously to ensure the competitiveness and viability of entire bioprocesses. While the primary focus of this research is on recovery process development, it serves as an initial step toward achieving that broader goal. Chapter 5 highlights the significance of integrating upstream and downstream processes in bioprocess development. Isopropanol, along with acetone, and 2-phenylethanol, were selected as representative examples of low boiling and high-boiling biochemicals. Large-scale bioprocesses for their production were designed to showcase the practical application of integrated process design. Isopropanol and acetone were produced through gas fermentation, with different combinations of products (isopropanol and acetone together or separately) considered. Previously developed advanced recovery processes, including heat pump-assisted vacuum distillation, followed by heat pump-assisted atmospheric distillation and extractive distillation, were employed. Detailed techno-economic analysis and life cycle assessments demonstrated competitive economic performance (total production costs of 0.57-0.74 $/kg) and reduced environmental impacts compared to fossil fuel-based production (reduced global warming potential by 138-160%). 2-phenylethanol was produced de-novo through fermentation from glucose. Two different in-situ product recovery processes were compared: liquid-liquid extraction using oleyl alcohol and product adsorption. In both cases, distillation-based separations were used to effectively recover the solvent and obtain high-purity 2-phenylethanol. Additionally, a sensitivity analysis was conducted to examine the influence of 2-phenylethanol concentration on total production costs. This analysis revealed that minimal costs were achieved at a concentration of 1.5 g/L, with concentrations above 1 g/L not resulting in a significant reduction in costs due to increased fermentation costs. Regardless of the used in-situ recovery technique, the developed processes for producing 2-phenylethanol were found to be highly cost-effective (total production costs of 9.03-9.40 $/kg).
Summarizing, this thesis illustrates the significant impact that advancements in downstream processing can have on overall process performance. Specifically, it supports the development of novel advanced separation processes, based on process intensification principles, which have received relatively limited attention in industrial biotechnology. These innovations can play a decisive role in determining the feasibility of bioprocesses for industrial scale applications. Furthermore, the importance of incorporating downstream processing at the early stages of developing biotechnology-based processes is highlighted. The findings presented in this thesis have the potential to drive progress in industrial biotechnology and contribute to the successful commercialization of biotechnology-based products.
Process systems engineering is essential in developing competitive (bio)chemical processes, as it integrates process design and simulation in biotechnology. Hence, this thesis aims to advance industrial biotechnology by developing advanced, large-scale downstream processes for the recovery of fermentation products such as alcohols, diols, esters, carboxylic acids, and aromatic compounds. A systematic approach to downstream process development was undertaken through multiple case studies that were organized into chapters based on the characteristics of the primary product being recovered. Aspen Plus software was used as a computer aided process engineering tool for process design. Various process intensification techniques (e.g. dividing-wall column and reactive distillation), heat integration and heat pumping were studied to reduce energy requirements and decrease total process costs. The performance of the developed processes was assessed through economic analysis and the evaluation of key sustainability metrics, including energy requirements, greenhouse gas emissions, water consumption, water losses, and toxic materials and pollutants intensity.
Chapter 2 focuses on designing downstream processing strategies tailored for low-boiling alcohols produced through fermentation, including ethanol, isopropanol, isobutanol, and hexanol. Since these products are sufficiently volatile, the end-product inhibition can be mitigated by continuously removing the product from the broth using a distillation-based loop around the bioreactor. Heat pump-assisted vacuum distillation was demonstrated as an effective method for initial product recovery from the broth. Additionally, a novel pass-through distillation process was designed specifically for ethanol recovery. This innovative technique separates the evaporation and condensation parts of distillation by introducing an absorption-desorption loop between them. As a result, these operations can be conducted at different pressures, allowing the use of inexpensive cooling utilities while maintaining mild evaporation temperatures. Furthermore, a hybrid approach combining gas stripping with heat pump-assisted vacuum evaporation was developed for the recovery of isobutanol from fermentation broth. In all cases, the initial separation of the product from most of the broth under reduced pressure lowers the operational temperature, making it possible to reuse the remaining broth along with the microorganisms. This may improve fermentation performance by avoiding biomass loss, increasing substrate-to-product yield and reducing water requirements. Following this initial step, a preconcentration step using heat pump-assisted atmospheric distillation was carried out to remove most of the remaining water. The final purification method depended on the properties of the target product. Ethanol and isopropanol, which form homogeneous azeotropes with water, were purified using extractive distillation with ethylene glycol. In contrast, isobutanol and hexanol, which form heterogeneous azeotropes, were purified through a combination of simple distillation and liquid-liquid phase separation. Furthermore, a general methodology for recovering volatile alcohols from fermentation broths was developed and the performance of downstream processing was compared for the recovery of ethanol, isopropanol, isobutanol, and hexanol. Due to the higher hydrophobicity of longer-chain alcohols, their concentrations in the fermentation broth tend to be lower (e.g. 6.14 wt% for ethanol, 5.00 wt% for isopropanol, 1.61 wt% for isobutanol, and 0.24 wt% for hexanol). More dilute fermentation broths result in higher processing costs (0.08, 0.11, 0.16, and 0.53 $/kg, respectively) and increased energy requirements (0.96, 1.35, 2.02 and 3.07 kWthh/kg, respectively) of the downstream processing. Finally, it was concluded that the primary factor influencing downstream processing efficiency is the achievable product concentration in the fermentation broth, rather than the alcohol chain length.
Chapter 3 focuses on developing recovery processes for aliphatic diols that can be produced through fermentation, including 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol. Due to their high boiling points, simple distillation is unsuitable for separating these compounds from the fermentation broth. Instead, initial separation steps are required to remove biomass, as well as large organic and inorganic molecules. These initial steps result in a clarified, desalted solution, which then undergoes further treatment through preconcentration and final purification. Since these final two steps contribute significantly to overall purification costs due to their high energy requirements, this research focuses on enhancing them to improve the efficiency of downstream processing for aliphatic diols. The preconcentration step was designed to remove most of water along with some light impurities using a heat pump-assisted vacuum distillation. The final purification step, which separates high-purity diol from residual light and heavy impurities, was effectively carried out in a dividing wall column. Furthermore, a general methodology for recovering high boiling components from dilute aqueous solutions was developed. Recovery processes for 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, and 1,3-butanediol, designed according to this methodology, were compared. The performance of downstream processing was primarily determined by the product concentration in the fermentation broth, though the presence of impurities also played a significant role. Nonetheless, in all cases, the proposed methodology enabled the cost effective (total recovery costs of 0.29-0.70 $/kg) and energy-efficient (primary energy requirements of 1.35-2.01 kWthh/kg) recovery of valuable propanediol and butanediol from dilute aqueous solutions (7.0-10.0 wt%). Lastly, adaptable process design offers the possibility of using a single process configuration to produce various aliphatic diols depending on the market demand.
Chapter 4 discusses the development of recovery processes for various organic chemicals produced through different biotechnology-based processes, such as ethyl acetate, propionic acid, 2-phenylethanol, acetic acid, furfural, etc. While these processes differ due to the unique properties of each compound, they all rely on distillation as a primary recovery method. It was employed as the main separation technique to efficiently recover propionic, acetic, and succinic acids from dilute aqueous solutions. An adaptable dividing-wall column design was demonstrated to effectively recover propionic and acetic acids or perform esterification with methanol to recover methyl-propionate and methyl-acetate (total recovery costs of 0.40-0.47 $/kg). Distillation was also utilized as the primary technique in the recovery of ethyl acetate. Due to its high volatility, most of the ethyl acetate is separated in the fermenter off-gas. Consequently, product recovery was carried out from both the vapor and liquid phases, with an azeotropic dividing-wall column used effectively for final purification (total recovery costs of 0.61-1.09 $/kg). Furthermore, distillation-based downstream processing was effectively used for the solvent recovery and final purification of 2-phenylethanol after in-situ product recovery by liquid-liquid extraction. An adaptable azeotropic dividing-wall column was designed to recover high-purity 2-phenylethanol or perform esterification and recover 2-phenylethyl acetate (total recovery costs of 0.64-0.73 $/kg). Lastly, a sequence of distillation steps was developed to recover by-products (acetic acid, formic acid, furfural, 5-hydroxymethyl furfural) from the lignocellulosic biomass pretreatment process using liquid hot water (total recovery costs of 0.78 $/kg). This process could enhance the competitiveness of lignocellulosic biorefineries by enabling the valorization of additional products.
Furthermore, this thesis emphasizes the importance of advancing both upstream and downstream processes simultaneously to ensure the competitiveness and viability of entire bioprocesses. While the primary focus of this research is on recovery process development, it serves as an initial step toward achieving that broader goal. Chapter 5 highlights the significance of integrating upstream and downstream processes in bioprocess development. Isopropanol, along with acetone, and 2-phenylethanol, were selected as representative examples of low boiling and high-boiling biochemicals. Large-scale bioprocesses for their production were designed to showcase the practical application of integrated process design. Isopropanol and acetone were produced through gas fermentation, with different combinations of products (isopropanol and acetone together or separately) considered. Previously developed advanced recovery processes, including heat pump-assisted vacuum distillation, followed by heat pump-assisted atmospheric distillation and extractive distillation, were employed. Detailed techno-economic analysis and life cycle assessments demonstrated competitive economic performance (total production costs of 0.57-0.74 $/kg) and reduced environmental impacts compared to fossil fuel-based production (reduced global warming potential by 138-160%). 2-phenylethanol was produced de-novo through fermentation from glucose. Two different in-situ product recovery processes were compared: liquid-liquid extraction using oleyl alcohol and product adsorption. In both cases, distillation-based separations were used to effectively recover the solvent and obtain high-purity 2-phenylethanol. Additionally, a sensitivity analysis was conducted to examine the influence of 2-phenylethanol concentration on total production costs. This analysis revealed that minimal costs were achieved at a concentration of 1.5 g/L, with concentrations above 1 g/L not resulting in a significant reduction in costs due to increased fermentation costs. Regardless of the used in-situ recovery technique, the developed processes for producing 2-phenylethanol were found to be highly cost-effective (total production costs of 9.03-9.40 $/kg).
Summarizing, this thesis illustrates the significant impact that advancements in downstream processing can have on overall process performance. Specifically, it supports the development of novel advanced separation processes, based on process intensification principles, which have received relatively limited attention in industrial biotechnology. These innovations can play a decisive role in determining the feasibility of bioprocesses for industrial scale applications. Furthermore, the importance of incorporating downstream processing at the early stages of developing biotechnology-based processes is highlighted. The findings presented in this thesis have the potential to drive progress in industrial biotechnology and contribute to the successful commercialization of biotechnology-based products.
Sustainable Isopropanol, Acetone or Mixed Production from Steel Mill Offgas
Modelling and Assessment of Syngas Fermentation at Different Titers and Yields
Journal article
(2025)
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Tamara Janković, Tobias Fecker, Jean Marc Daran, Adrie J.J. Straathof, Anton A. Kiss
BACKGROUND: 2-Phenylethanol (2PE) is a valuable aroma component that can be obtained through de-novo fermentation from glucose. However, its toxicity at very low concentrations (<2.5 g L−1) limits the fermentation titer, rate and yield. To address these limitations, in-situ product removal has been explored, leading to a recent scale-up to pilot scale. Nonetheless, an industrial scale has yet to be achieved. RESULTS: This original research pioneers conceptual development of two large-scale (2 ktonne2PE/y) production processes for 2PE via de-novo fermentation from glucose. Liquid–liquid extraction with oleyl alcohol and adsorption by hydrophobic resins followed by ethanol desorption, were alternatives considered for in-situ 2PE removal. For either design, solvent recovery and final purification were performed using advanced distillation techniques, including a heat pump-assisted distillation and a dividing-wall column. A fermentation titer of approximately 1.5 g2PE/Lbroth minimized production costs by achieving balance between upstream and downstream processing costs. This resulted in a cost-effective 2PE production for both designs of the recovery process (9.03–9.40 $/kg2PE). Sensitivity analysis revealed that glucose, oleyl alcohol, and ethanol costs strongly impact total production costs. CONCLUSION: This novel study provides a comprehensive and scalable process framework for the large-scale production of 2PE through de-novo fermentation. Integrating in-situ product removal and energy-efficient purification strategies, it marks a significant step forward in industrial biotechnology.
...
BACKGROUND: 2-Phenylethanol (2PE) is a valuable aroma component that can be obtained through de-novo fermentation from glucose. However, its toxicity at very low concentrations (<2.5 g L−1) limits the fermentation titer, rate and yield. To address these limitations, in-situ product removal has been explored, leading to a recent scale-up to pilot scale. Nonetheless, an industrial scale has yet to be achieved. RESULTS: This original research pioneers conceptual development of two large-scale (2 ktonne2PE/y) production processes for 2PE via de-novo fermentation from glucose. Liquid–liquid extraction with oleyl alcohol and adsorption by hydrophobic resins followed by ethanol desorption, were alternatives considered for in-situ 2PE removal. For either design, solvent recovery and final purification were performed using advanced distillation techniques, including a heat pump-assisted distillation and a dividing-wall column. A fermentation titer of approximately 1.5 g2PE/Lbroth minimized production costs by achieving balance between upstream and downstream processing costs. This resulted in a cost-effective 2PE production for both designs of the recovery process (9.03–9.40 $/kg2PE). Sensitivity analysis revealed that glucose, oleyl alcohol, and ethanol costs strongly impact total production costs. CONCLUSION: This novel study provides a comprehensive and scalable process framework for the large-scale production of 2PE through de-novo fermentation. Integrating in-situ product removal and energy-efficient purification strategies, it marks a significant step forward in industrial biotechnology.
Green Industrial Scale Plant Design for Syngas Fermentation to Isopropyl Alcohol and Acetone
Economic and Environmental Sustainability Assessment
Conference paper
(2025)
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G.J.A. Brouwer, T. Jankovic, Adrie J.J. Straathof, A.A. Kiss, John A. Posada
Steel mill off gas fermentation presents a promising green alternative to petrochemical isopropyl alcohol (isopropanol, IPA) and acetone production while potentially reducing greenhouse gas emissions. A pilot-scale study stated negative global warming potential (GWP) at 85% gas conversion and 90% product selectivity. However, industrial-scale plant design including detailed techno-economic assessment (TEA) and life cycle assessment (LCA) remain undescribed. Therefore , this study modelled a heat-integrated 47.5 kton/ year gas fermentation process to IPA and acetone, based on pilot-scale data. The downstream processing was designed using vacuum distillation and heat-pump integrated (extractive) distillation to purify the 50 gproduct/ L broth with bi-omass and acetate as byproducts, to obtain 41.8 kton/ year of 99.6 wt. % IPA and 5.64 kton/ year of 99.0 wt. % acetone. Notably, no steam is consumed and 2.6 MWh of electricity is generated by utilising the energy from the steel mill off gas. The estimated unit production cost (UPC; 0.57 /kgproduct)issignificantlybelowmarketprices(1.65/ kgIPA and 1.45 $/ kgacetone). Moreover, the cradle-to-gate LCA gave GWPs of-1.42 kgCO2-eq/ kgIPA and-1.25 kgCO2-eq/ kgacetone, mainly due to avoided steel mill emissions. Other environmental impacts studied were also lower than for petrochemical production. Only the freshwater use is higher (70 L/ kgIPA and 62 L/ kgacetone) compared to petrochemical production (16 L/ kgIPA and 28 L/ kgacetone). Future research should study the impact of IPA and acetone selectivity and titer on the economic and environmental sustainability of steel mill off gas fermentation to IPA and acetone.
...
Steel mill off gas fermentation presents a promising green alternative to petrochemical isopropyl alcohol (isopropanol, IPA) and acetone production while potentially reducing greenhouse gas emissions. A pilot-scale study stated negative global warming potential (GWP) at 85% gas conversion and 90% product selectivity. However, industrial-scale plant design including detailed techno-economic assessment (TEA) and life cycle assessment (LCA) remain undescribed. Therefore , this study modelled a heat-integrated 47.5 kton/ year gas fermentation process to IPA and acetone, based on pilot-scale data. The downstream processing was designed using vacuum distillation and heat-pump integrated (extractive) distillation to purify the 50 gproduct/ L broth with bi-omass and acetate as byproducts, to obtain 41.8 kton/ year of 99.6 wt. % IPA and 5.64 kton/ year of 99.0 wt. % acetone. Notably, no steam is consumed and 2.6 MWh of electricity is generated by utilising the energy from the steel mill off gas. The estimated unit production cost (UPC; 0.57 /kgproduct)issignificantlybelowmarketprices(1.65/ kgIPA and 1.45 $/ kgacetone). Moreover, the cradle-to-gate LCA gave GWPs of-1.42 kgCO2-eq/ kgIPA and-1.25 kgCO2-eq/ kgacetone, mainly due to avoided steel mill emissions. Other environmental impacts studied were also lower than for petrochemical production. Only the freshwater use is higher (70 L/ kgIPA and 62 L/ kgacetone) compared to petrochemical production (16 L/ kgIPA and 28 L/ kgacetone). Future research should study the impact of IPA and acetone selectivity and titer on the economic and environmental sustainability of steel mill off gas fermentation to IPA and acetone.
Many fermentation products inhibit their own microbial production, which complicates industrial-scale fermentation development for these products. When a product is volatile, this inhibition can be circumvented by removing product during fermentation through evaporation in a loop around the bioreactor. Microbes can survive this loop if its temperature is reduced using vacuum. Then, regrowing of microbes is not required. From a separation efficiency viewpoint, the evaporation loop should not use a single equilibrium stage, but a multistage vacuum distillation column. Such in situ product removal (ISPR) by vacuum distillation has hardly been recognized as an option, however. Costs for this product removal with subsequent purification are modest, even when product titers are low. A prerequisite is the use of advanced energy integration and heat pumping methods.
...
Many fermentation products inhibit their own microbial production, which complicates industrial-scale fermentation development for these products. When a product is volatile, this inhibition can be circumvented by removing product during fermentation through evaporation in a loop around the bioreactor. Microbes can survive this loop if its temperature is reduced using vacuum. Then, regrowing of microbes is not required. From a separation efficiency viewpoint, the evaporation loop should not use a single equilibrium stage, but a multistage vacuum distillation column. Such in situ product removal (ISPR) by vacuum distillation has hardly been recognized as an option, however. Costs for this product removal with subsequent purification are modest, even when product titers are low. A prerequisite is the use of advanced energy integration and heat pumping methods.
Ethyl acetate is a platform chemical conventionally obtained through fossil fuel routes, but more recently its production by fermentation from carbohydrates has been scaled up to a pilot scale. Yet, the complexity of downstream processing (low product concentrations in liquid broth and in off-gas, azeotrope formation, and the presence of microorganisms) may complicate industrial application. This original theoretical study is the first to develop advanced downstream processing, based on process intensification principles, for large-scale recovery (~10 kton/year) of ethyl acetate after fermentation. To minimize product losses, ethyl acetate is separated from both the liquid broth and off-gas. The final purification is performed in a highly integrated azeotropic dividing-wall column. The economic and sustainability analysis shows that using refrigeration for initial product separation from the gas phase is more cost-effective (~0.61 $/kg) and less energy-intensive (2.20–2.40 kWthh/kg) than compression combined with high-pressure condensation using chilled water (1.09 $/kg and 9.98 kWthh/kg).
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Ethyl acetate is a platform chemical conventionally obtained through fossil fuel routes, but more recently its production by fermentation from carbohydrates has been scaled up to a pilot scale. Yet, the complexity of downstream processing (low product concentrations in liquid broth and in off-gas, azeotrope formation, and the presence of microorganisms) may complicate industrial application. This original theoretical study is the first to develop advanced downstream processing, based on process intensification principles, for large-scale recovery (~10 kton/year) of ethyl acetate after fermentation. To minimize product losses, ethyl acetate is separated from both the liquid broth and off-gas. The final purification is performed in a highly integrated azeotropic dividing-wall column. The economic and sustainability analysis shows that using refrigeration for initial product separation from the gas phase is more cost-effective (~0.61 $/kg) and less energy-intensive (2.20–2.40 kWthh/kg) than compression combined with high-pressure condensation using chilled water (1.09 $/kg and 9.98 kWthh/kg).
PDO (1,3-propanediol) is a platform chemical that is obtained by petrochemical routes and by fermentation. The latter needs relatively complex downstream processing after fermentation, due to the modest concentration of the high-boiling product, and the presence of microorganisms and many impurities in the fermentation medium. This novel research proposes an original large-scale (production capacity of 23 – 32 ktonne/y) process for the final purification of PDO and dominant by-products, from the fermentation of glucose or glycerol. Following the initial microfiltration, diafiltration, ultrafiltration and ion exchange steps, heat pump-assisted vacuum distillation was implemented to remove most of the water from the broth. Afterwards, an advanced highly-integrated dividing-wall column was designed to allow the final purification of PDO (product purity > 99.9 wt%) from light and heavy by-products. Fermentation by-products that are present in significant amounts can also be recovered and valorized. Overall, the developed final purification processes demonstrate cost-effectiveness (0.150 – 0.274 $/kg) and energy-efficiency (1.258 – 3.175 kWthh/kg) which contributes to the competitiveness of the overall downstream processing (0.256 – 0.384 $/kg and 1.487 – 3.496 kWthh/kg).
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PDO (1,3-propanediol) is a platform chemical that is obtained by petrochemical routes and by fermentation. The latter needs relatively complex downstream processing after fermentation, due to the modest concentration of the high-boiling product, and the presence of microorganisms and many impurities in the fermentation medium. This novel research proposes an original large-scale (production capacity of 23 – 32 ktonne/y) process for the final purification of PDO and dominant by-products, from the fermentation of glucose or glycerol. Following the initial microfiltration, diafiltration, ultrafiltration and ion exchange steps, heat pump-assisted vacuum distillation was implemented to remove most of the water from the broth. Afterwards, an advanced highly-integrated dividing-wall column was designed to allow the final purification of PDO (product purity > 99.9 wt%) from light and heavy by-products. Fermentation by-products that are present in significant amounts can also be recovered and valorized. Overall, the developed final purification processes demonstrate cost-effectiveness (0.150 – 0.274 $/kg) and energy-efficiency (1.258 – 3.175 kWthh/kg) which contributes to the competitiveness of the overall downstream processing (0.256 – 0.384 $/kg and 1.487 – 3.496 kWthh/kg).
Even though industrial biotechnology is successfully used for the production of some chemicals, for many other chemicals it is not yet competitive with conventional petrochemical production. Usually, fermentation as well as downstream processing requires improvement. Downstream processing has to deal with low product concentrations, microorganisms, impurities and thermodynamic constraints (e.g., azeotropes), which often makes it very challenging and expensive, especially on a large scale. However, downstream processing of biochemicals has not attracted as much attention as upstream fermentation processes. In that context, this perspective paper offers a lightly referenced scholarly opinion about the downstream processing performance of different bioalcohols after fermentation. Due to the stronger toxicity effects on microbes, the achievable concentrations of monohydric aliphatic alcohols in the fermentation broth decrease with the increasing chain length. Specifically, the concentrations used here are 6.14, 5.00, 1.61 and 0.24 wt% of ethanol, isopropanol, isobutanol and hexanol, respectively. More dilute fermentation broths lead to more complex recovery processes. According to our previous work, the total purification costs increase from 0.080 USD kg−1 for ethanol, 0.109 USD kg−1 for isopropanol and 0.161 USD kg−1 for isobutanol to 0.529 USD kg−1 for hexanol. A similar trend is noticeable for the energy usage (0.960, 1.348, 2.018 and 3.069 kWthh kg−1, respectively) and the related CO2 emissions (0.164, 0.221, 0.449 and 0.555 kgCO2 kg−1, respectively). This work shows that advanced separation and purification based on process intensification principles are crucial for overall efficient production processes. The achievable product concentration in the fermentation broth – and not so much the alcohol chain length – has the biggest influence on the performance of downstream processing. Therefore, simultaneous development of both upstream and downstream processing is necessary to ensure the competitiveness and viability of industrial fermentation processes. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).
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Even though industrial biotechnology is successfully used for the production of some chemicals, for many other chemicals it is not yet competitive with conventional petrochemical production. Usually, fermentation as well as downstream processing requires improvement. Downstream processing has to deal with low product concentrations, microorganisms, impurities and thermodynamic constraints (e.g., azeotropes), which often makes it very challenging and expensive, especially on a large scale. However, downstream processing of biochemicals has not attracted as much attention as upstream fermentation processes. In that context, this perspective paper offers a lightly referenced scholarly opinion about the downstream processing performance of different bioalcohols after fermentation. Due to the stronger toxicity effects on microbes, the achievable concentrations of monohydric aliphatic alcohols in the fermentation broth decrease with the increasing chain length. Specifically, the concentrations used here are 6.14, 5.00, 1.61 and 0.24 wt% of ethanol, isopropanol, isobutanol and hexanol, respectively. More dilute fermentation broths lead to more complex recovery processes. According to our previous work, the total purification costs increase from 0.080 USD kg−1 for ethanol, 0.109 USD kg−1 for isopropanol and 0.161 USD kg−1 for isobutanol to 0.529 USD kg−1 for hexanol. A similar trend is noticeable for the energy usage (0.960, 1.348, 2.018 and 3.069 kWthh kg−1, respectively) and the related CO2 emissions (0.164, 0.221, 0.449 and 0.555 kgCO2 kg−1, respectively). This work shows that advanced separation and purification based on process intensification principles are crucial for overall efficient production processes. The achievable product concentration in the fermentation broth – and not so much the alcohol chain length – has the biggest influence on the performance of downstream processing. Therefore, simultaneous development of both upstream and downstream processing is necessary to ensure the competitiveness and viability of industrial fermentation processes. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).
Propionic acid is a valuable platform chemical that is usually produced via fossil routes. As these are energy-intensive and eco-unfriendly processes, fermentative production of propionic acid is becoming more attractive. However, the complex downstream processing (due to low achievable product concentrations, high water content, presence of by-products and thermodynamic constraints), presents a potential barrier to scale-up this technology. This original research proposes a novel intensified large-scale (production capacity of ∼ 20 ktonne/y) process for the final recovery of propionic acid after the initial biomass and counterion removal. Vacuum distillation steps ensure the recovery of a high-purity succinic acid product (>99.9 wt%) and a water stream that may be recycled to the fermentation to reduce the fresh water requirements. The main unit that follows is a highly integrated heat pump-assisted dividing-wall column (DWC), which allows the effective separation of propionic (>99.9 wt%) and acetic acid (99.4 wt%) products. Alternatively, it can serve as a reactive DWC that performs the esterification and separation of methyl propionate (99.8 wt%), methyl acetate (91.0 wt%) as higher added value products, and water by-product. If needed, extractive distillation can be implemented additionally to recover methyl acetate at higher purity (99.9 wt%). Overall, both options are proven to be economically interesting (recovery costs of 0.399 – 0.469 $/kg considering the product price of 1.349 – 1.802 $/kg) and environmentally attractive (3.206 – 3.678 kWthh/kg).
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Propionic acid is a valuable platform chemical that is usually produced via fossil routes. As these are energy-intensive and eco-unfriendly processes, fermentative production of propionic acid is becoming more attractive. However, the complex downstream processing (due to low achievable product concentrations, high water content, presence of by-products and thermodynamic constraints), presents a potential barrier to scale-up this technology. This original research proposes a novel intensified large-scale (production capacity of ∼ 20 ktonne/y) process for the final recovery of propionic acid after the initial biomass and counterion removal. Vacuum distillation steps ensure the recovery of a high-purity succinic acid product (>99.9 wt%) and a water stream that may be recycled to the fermentation to reduce the fresh water requirements. The main unit that follows is a highly integrated heat pump-assisted dividing-wall column (DWC), which allows the effective separation of propionic (>99.9 wt%) and acetic acid (99.4 wt%) products. Alternatively, it can serve as a reactive DWC that performs the esterification and separation of methyl propionate (99.8 wt%), methyl acetate (91.0 wt%) as higher added value products, and water by-product. If needed, extractive distillation can be implemented additionally to recover methyl acetate at higher purity (99.9 wt%). Overall, both options are proven to be economically interesting (recovery costs of 0.399 – 0.469 $/kg considering the product price of 1.349 – 1.802 $/kg) and environmentally attractive (3.206 – 3.678 kWthh/kg).
Isobutanol is a highly attractive renewable alternative to conventional fossil fuels, with superior fuel properties as compared to ethanol and 1-butanol. Even though the isobutanol production by fermentation has significant potential, complex downstream processing is limiting the wide-spreading of this technology. Accordingly, this original research significantly contributes to the advancement in industrial biofuel production by developing two eco-efficient downstream processes for the industrial-scale recovery of isobutanol (production capacity 50 ktonneIBUT/y), from a highly dilute fermentation broth (>98 wt% water). Vacuum distillation and a novel hybrid combination of gas stripping and vacuum evaporation were coupled with atmospheric azeotropic distillation to recover over 99.9 % of isobutanol as a high-purity product (100 wt%). Advanced heat pumping and heat integration techniques were further implemented to allow the complete electrification of these recovery processes. Furthermore, implementation of these techniques significantly decreased total annual costs (0.131–0.161 $/kgIBUT), reduced energy requirements (0.488–0.807 kWeh/kgIBUT) and lowered CO2 emissions (0.303–0.449 kgCO2/kgIBUT), resulting in highly competitive purification processes. In addition to efficiently recovering isobutanol, the designed downstream processes provide the potential to enhance the fermentation process by recycling all present microorganisms and reducing water demand. Therefore, the results of this original research substantially contribute to the advancement in industrial biotechnology and the wide-spreading of biofuel production.
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Isobutanol is a highly attractive renewable alternative to conventional fossil fuels, with superior fuel properties as compared to ethanol and 1-butanol. Even though the isobutanol production by fermentation has significant potential, complex downstream processing is limiting the wide-spreading of this technology. Accordingly, this original research significantly contributes to the advancement in industrial biofuel production by developing two eco-efficient downstream processes for the industrial-scale recovery of isobutanol (production capacity 50 ktonneIBUT/y), from a highly dilute fermentation broth (>98 wt% water). Vacuum distillation and a novel hybrid combination of gas stripping and vacuum evaporation were coupled with atmospheric azeotropic distillation to recover over 99.9 % of isobutanol as a high-purity product (100 wt%). Advanced heat pumping and heat integration techniques were further implemented to allow the complete electrification of these recovery processes. Furthermore, implementation of these techniques significantly decreased total annual costs (0.131–0.161 $/kgIBUT), reduced energy requirements (0.488–0.807 kWeh/kgIBUT) and lowered CO2 emissions (0.303–0.449 kgCO2/kgIBUT), resulting in highly competitive purification processes. In addition to efficiently recovering isobutanol, the designed downstream processes provide the potential to enhance the fermentation process by recycling all present microorganisms and reducing water demand. Therefore, the results of this original research substantially contribute to the advancement in industrial biotechnology and the wide-spreading of biofuel production.
Isopropanol-butanol-ethanol (IBE) fermentation is a superior biofuel production technology as compared to acetone-butanol-ethanol (ABE) fermentation due to the better fuel properties of the obtained products. However, low product concentrations, thermodynamic constraints and the presence of microorganisms lead to complex downstream processing that limits the competitiveness of this biofuel production method. Thus, this original research proposes a novel thermally self-sufficient and eco-efficient downstream process for industrial-scale recovery after IBE fermentation (74 ktonne/y capacity), from a highly dilute broth (>97 wt% water). Gas stripping and heat pump-assisted vacuum evaporation were implemented to separate valuable products from most of the broth. Furthermore, an advanced highly integrated heat pump-assisted azeotropic dividing-wall column was designed to recover high-purity (99 wt%) butanol biofuel and isopropanol – ethanol fuel supplement (89 wt%). The proposed purification process recovers over 99 % of biofuel products in a cost-effective (0.130 $/kgIBE) and energy-efficient way (0.673 kWeh/kgIBE) while allowing full recycle of biomass and most of the separated water. Besides improving yield by continuously recovering the inhibitory products, fermentation can be further enhanced by avoiding biomass loss and reducing water requirements. Lastly, the implemented energy-saving techniques ensure complete electrification of the proposed IBE recovery process. Therefore, the original results of this research study significantly contribute to the development of sustainable biofuel production processes.
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Isopropanol-butanol-ethanol (IBE) fermentation is a superior biofuel production technology as compared to acetone-butanol-ethanol (ABE) fermentation due to the better fuel properties of the obtained products. However, low product concentrations, thermodynamic constraints and the presence of microorganisms lead to complex downstream processing that limits the competitiveness of this biofuel production method. Thus, this original research proposes a novel thermally self-sufficient and eco-efficient downstream process for industrial-scale recovery after IBE fermentation (74 ktonne/y capacity), from a highly dilute broth (>97 wt% water). Gas stripping and heat pump-assisted vacuum evaporation were implemented to separate valuable products from most of the broth. Furthermore, an advanced highly integrated heat pump-assisted azeotropic dividing-wall column was designed to recover high-purity (99 wt%) butanol biofuel and isopropanol – ethanol fuel supplement (89 wt%). The proposed purification process recovers over 99 % of biofuel products in a cost-effective (0.130 $/kgIBE) and energy-efficient way (0.673 kWeh/kgIBE) while allowing full recycle of biomass and most of the separated water. Besides improving yield by continuously recovering the inhibitory products, fermentation can be further enhanced by avoiding biomass loss and reducing water requirements. Lastly, the implemented energy-saving techniques ensure complete electrification of the proposed IBE recovery process. Therefore, the original results of this research study significantly contribute to the development of sustainable biofuel production processes.
Pass-through distillation (PTD) is a novel separation technology that can effectively overcome challenges related to using vacuum distillation in bio-based processes (defined temperature limit for evaporation that might result in very low condensation temperature). This method allows evaporation and condensation to be performed at different pressures by decoupling them using an absorption-desorption loop with an electrolyte absorption fluid. This original paper presents a process design for large-scale bioethanol recovery from fermentation broth (production capacity ~100 ktonne/y) by PTD. The flexibility of the novel PTD technology is expanded by combining it with heat pumps (PTD-HP) and multi-effect distillation (PTD-MED). Total cost and energy requirements for the recovery of high-purity bioethanol (99.8 wt%) are respectively 0.122 $/kgEtOH and 1.723 kWthh/kgEtOH for PTD-HP, and 0.131 $/kgEtOH and 1.834 kWthh/kgEtOH for PTD-MED, proving the effectiveness of the newly designed recovery processes for concurrent alcohol recovery and fermentation.
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Pass-through distillation (PTD) is a novel separation technology that can effectively overcome challenges related to using vacuum distillation in bio-based processes (defined temperature limit for evaporation that might result in very low condensation temperature). This method allows evaporation and condensation to be performed at different pressures by decoupling them using an absorption-desorption loop with an electrolyte absorption fluid. This original paper presents a process design for large-scale bioethanol recovery from fermentation broth (production capacity ~100 ktonne/y) by PTD. The flexibility of the novel PTD technology is expanded by combining it with heat pumps (PTD-HP) and multi-effect distillation (PTD-MED). Total cost and energy requirements for the recovery of high-purity bioethanol (99.8 wt%) are respectively 0.122 $/kgEtOH and 1.723 kWthh/kgEtOH for PTD-HP, and 0.131 $/kgEtOH and 1.834 kWthh/kgEtOH for PTD-MED, proving the effectiveness of the newly designed recovery processes for concurrent alcohol recovery and fermentation.
Distillation is the most used separation technology at industrial-scale, but using distillation in bio-based processes (e.g. fermentation processes to produce bioethanol) is quite challenging when mild temperatures are needed to keep the microbes alive. Vacuum distillation can be used to perform evaporation at low temperatures, but setting a low distillation pressure fixes also the condensation temperature to very low values that may require expensive refrigeration. Pass-through distillation (PTD) is an emerging hybrid separation technology that effectively combines distillation with absorption in a sorption-assisted distillation process that decouples the evaporation and condensation steps. This is achieved by inserting between the evaporation and condensation steps an absorption-desorption loop that passes through the component to be separated and allows the use of different pressures and types of heating and cooling utilities. This paper is the first to present the process design and rigorous simulation (implemented in Aspen Plus) of a new pass-through distillation process for bioethanol (∼100 ktonne/y plant capacity), proving its effectiveness in concurrent alcohol recovery and fermentation (CARAF). Combining PTD with heat pumps leads to low recovery costs of 0.122 $/kgEtOH and energy requirements of only 1.723 kWthh/kgEtOH. Alternatively, combining PTD with multi-effect distillation resulted in 0.131 $/kgEtOH recovery costs and 1.834 kWthh/kgEtOH energy intensity.
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Distillation is the most used separation technology at industrial-scale, but using distillation in bio-based processes (e.g. fermentation processes to produce bioethanol) is quite challenging when mild temperatures are needed to keep the microbes alive. Vacuum distillation can be used to perform evaporation at low temperatures, but setting a low distillation pressure fixes also the condensation temperature to very low values that may require expensive refrigeration. Pass-through distillation (PTD) is an emerging hybrid separation technology that effectively combines distillation with absorption in a sorption-assisted distillation process that decouples the evaporation and condensation steps. This is achieved by inserting between the evaporation and condensation steps an absorption-desorption loop that passes through the component to be separated and allows the use of different pressures and types of heating and cooling utilities. This paper is the first to present the process design and rigorous simulation (implemented in Aspen Plus) of a new pass-through distillation process for bioethanol (∼100 ktonne/y plant capacity), proving its effectiveness in concurrent alcohol recovery and fermentation (CARAF). Combining PTD with heat pumps leads to low recovery costs of 0.122 $/kgEtOH and energy requirements of only 1.723 kWthh/kgEtOH. Alternatively, combining PTD with multi-effect distillation resulted in 0.131 $/kgEtOH recovery costs and 1.834 kWthh/kgEtOH energy intensity.
Lignocellulosic biomass potentially represents a great feedstock for biofuel production, but its’ pretreatment needs to be enhanced in order to make biorefineries competitive with fossil fuel based alternatives. One way to make biorefineries more economically viable is to recover and valorize all generated by-products during the biomass pretreatment step. The main goal of this original research is to design an optimal process for recovering valuable by-products after hot-liquid water pretreatment of poplar biomass. Rigorous models for all operations included in the recovery process are developed using Aspen Plus as a CAPE tool. An optimal downstream processing sequence, consisting of multiple distillation steps, is designed to recover several valuable components, such as acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF).
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Lignocellulosic biomass potentially represents a great feedstock for biofuel production, but its’ pretreatment needs to be enhanced in order to make biorefineries competitive with fossil fuel based alternatives. One way to make biorefineries more economically viable is to recover and valorize all generated by-products during the biomass pretreatment step. The main goal of this original research is to design an optimal process for recovering valuable by-products after hot-liquid water pretreatment of poplar biomass. Rigorous models for all operations included in the recovery process are developed using Aspen Plus as a CAPE tool. An optimal downstream processing sequence, consisting of multiple distillation steps, is designed to recover several valuable components, such as acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF).
Turning waste into value
Eco-efficient recovery of by-products from biomass pretreatment in lignocellulosic biorefineries
This original research contributes to enhancing the viability of biorefineries through recovering valuable by-products from the liquid remaining after the biomass pretreatment by hot liquid water. A novel downstream processing method is developed for the recovery of acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF) by enhanced distillation. The major challenge in this research is the processing of the highly diluted initial solution (>96 wt% water) and the thermodynamic limitations owing to possible formation of several azeotropes. This new process recovers 78.7% of the acetic acid (99.8 wt%), while the rest of it is recycled back to the biomass pretreatment step together with most of the separated water from the initial solution. Over 99.5% of formic acid, furfural and HMF is also recovered, at purities of 74.7, 98.0 and 100 wt%, respectively. Vapor recompression and heat integration are implemented to decrease the energy use. The results demonstrate a 77.4% decrease in total annual costs (from $3.44 to 0.78/kgproduct), a 75.0% reduction in minimum average selling price (from $3.50 to 0.87/kgproduct), an 81.1% reduction in energy requirements (from 77.41 to 14.66 kWthh/kgproduct) and an up to 99.7% decrease in CO2 emissions (from 11.17 to 0.03 kgCO2/kgproduct).
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This original research contributes to enhancing the viability of biorefineries through recovering valuable by-products from the liquid remaining after the biomass pretreatment by hot liquid water. A novel downstream processing method is developed for the recovery of acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF) by enhanced distillation. The major challenge in this research is the processing of the highly diluted initial solution (>96 wt% water) and the thermodynamic limitations owing to possible formation of several azeotropes. This new process recovers 78.7% of the acetic acid (99.8 wt%), while the rest of it is recycled back to the biomass pretreatment step together with most of the separated water from the initial solution. Over 99.5% of formic acid, furfural and HMF is also recovered, at purities of 74.7, 98.0 and 100 wt%, respectively. Vapor recompression and heat integration are implemented to decrease the energy use. The results demonstrate a 77.4% decrease in total annual costs (from $3.44 to 0.78/kgproduct), a 75.0% reduction in minimum average selling price (from $3.50 to 0.87/kgproduct), an 81.1% reduction in energy requirements (from 77.41 to 14.66 kWthh/kgproduct) and an up to 99.7% decrease in CO2 emissions (from 11.17 to 0.03 kgCO2/kgproduct).