Low-temperature Fischer-Tropsch Synthesis Research Articles

Tuning selectivity in low-temperature Fischer-Tropsch synthesis by applying gas recycle mode

While hydrocarbons production by Fischer-Tropsch synthesis (FTS) is widely recognized, commercial interest in FTS products is mainly constrained by oil prices. The FTS-derived fuels, although higher quality and greener, cannot currently compete with cheaper fossil fuels, motivating to shift the FTS products distribution to higher value-added chemicals, such as olefins-C5+. The high olefin selectivity in FTS over Co-based catalysts is usually ascribed to Co2C on the catalyst surface with its inherent deficiencies. This study demonstrates a novel approach to alter low-temperature FTS selectivity by applying off-gas recycling. At slow gas recycling rates, C19+ selectivity increases due to re-adsorption and re-incorporation into the growing chain of gaseous olefins from the off-gas. High-intensity gas recycling facilitates C5+ olefin vapors removal from the reactor by enhanced gas flow with their subsequent cut-off in the cold trap, thus reducing residence time of condensed olefins and probability of their secondary reactions.

An Overview of Low-Temperature Fischer–Tropsch Synthesis: Market Conditions, Raw Materials, Reactors, Scale-Up, Process Intensification, Mechanisms, and Outlook

An Overview of Low-Temperature Fischer–Tropsch Synthesis: Market Conditions, Raw Materials, Reactors, Scale-Up, Process Intensification, Mechanisms, and Outlook

Optimization of coal-to-liquid processes; A way forward towards carbon neutrality, high economic returns and effective resource utilization. Evidences from China

As the world's largest consumer of coal, China is committed to developing a carbon–neutral coal industry. For this purpose, upgrading the carbon emission-intensive coal-chemical industries, such as coal-to-liquids (CTL) is imperative. This study develops a technical–economic framework to model and test four promising CTL upgrading processes. First and second processes involve low-temperature Fischer-Tropsch (FT) synthesis practices with larger gasifiers and air-separating units than the current level. Third, the process combines olefin and fuel co-production practices that utilize low- and high-temperature FT synthesis processes. Finally, the process produces both electricity and fuel by sending the tail gas of the synthesis process to an integrated cycle. Aspen Plus® is used to simulate the chemical processes, and the financial cost accounting model of the American Association of Cost Engineers is utilized to estimate the financial costs accurately. The results show that the upgraded processes can achieve an energy efficiency of more than 48 %, which is 6 % higher than the existing coal-to-oil process. Additionally, the break-even point is 2 %–14.45 % lower than the actual process, reducing carbon emissions by 2.78 %–10.34 %. According to these findings, the upgrade can help China reach its carbon neutrality targets and significantly contribute to global climate change and sustainable development goals.

Effect of a High Thermal Capacitance Core–Shell Structure on Co-Ru/SiO2 Catalyst for Low Temperature Fischer–Tropsch Synthesis

Effect of a High Thermal Capacitance Core–Shell Structure on Co-Ru/SiO2 Catalyst for Low Temperature Fischer–Tropsch Synthesis

Cobalt Catalyzed Fischer-Tropsch Synthesis with O2-Containing Syngas

Provision of sustainable transportation fuels is required for the energetic transition. A new process is presented for the production of synthetic sulfur free maritime fuel. This fuel is produced by Co-catalyzed Fischer-Tropsch synthesis (FTS) using syngas based on a plasma technology that contains traces of O2. Gravimetric experiments and steady state measurements with a Co/Pt/Al2O3 catalyst at low temperature FTS conditions (10–30 bar, 180–230 °C) show that, with H2 present in the system, the catalyst remains active for FTS, and shows no influence on the distribution of C2+-hydrocarbons. O2 is only converted to H2O and CO2 in varying proportions (H2O: 70–80%, CO2: 20–30%), whereby a higher CO concentration increases the CO2 selectivity. This work may wield a new CO2 source for carbon-neutral fuels.

Reactive Separations of CO/CO2 mixtures over Ru–Co Single Atom Alloys

Reactive separations of CO/CO2 mixtures are a promising pathway to lower the energy requirement of CO2 hydrogenation to chemicals and fuels, with applications in the U.S. Navy’s seawater-to-fuel process. With the CO/CO2 feedstock, a challenge is activating CO to produce heavier hydrocarbons while preventing CO2 methanation, requiring low-temperature Fischer-Tropsch synthesis (FTS) catalysts. In this work, we demonstrate that a Ru–Co single atom alloy (SAA) catalyst produces C5+ hydrocarbons at a rate of 11.7 μmol/s/g-cobalt (hexane basis) in a 50/50 CO/CO2 stream with ≤1% CO2 conversion. The reaction operates at a relatively low temperature (200 °C) and high gas hourly space velocity (GHSV: 84,000 mL/g/h) that is compatible with the upstream reverse water-gas shift reaction. Detailed experiments, catalyst characterizations, and density functional theory (DFT) calculations have been conducted to understand the active phase, the role of the Ru dopant, and catalyst restructuring that occurs at elevated temperatures (>200 °C). Ru dopants are found to promote the reduction of Co species, enabling catalytic activity for CO hydrogenation without pre-reduction, but may not enhance the FTS activity or desired C5+ hydrocarbon selectivity.

Fischer-Tropsch synthesis over lignin-derived cobalt-containing porous carbon fiber catalysts

Cobalt-containing lignin-based fibers were synthesized in one step by electrospinning of Alcell lignin solutions as carbon precursor, a low-cost and renewable co-product of the paper making industry. The lignin fibers were thermostabilized in air to avoid the fusion during the carbonization process between 500 and 800 °C to obtain cobalt-containing porous carbon submicron fibers. These carbon fibers catalysts were studied for the Low-Temperature Fischer-Tropsch synthesis. The lignin-derived fibers containing Co catalyst located on the overall carbon fiber surface (internal and external) heat-treated at 500 °C (Co@CF-500) showed the best catalytic performance after 70 h on stream, with 75% and 60% selectivity to C5+ at 220 °C and H2/CO ratios of 1 and 2, respectively, attributed to the high Co dispersion, optimal Co-particle size and better Co accessibility. Higher heat-treatment temperatures leaded to Co-containing carbon fibers with larger metallic cobalt nanoparticles encapsulated in graphitic-type carbon, which rendered them inaccessible for FTS.

Catalytic Performance of Alumina-Supported Cobalt Carbide Catalysts for Low-Temperature Fischer–Tropsch Synthesis

The determination of the catalyst’s active phase helps improve the catalytic performance of the Fischer–Tropsch (FT) synthesis. Different phases of cobalt, including cobalt oxide, carbide, and metal, exist during the reaction. The content of each phase can affect the catalytic performance and product distribution. In this study, a series of cobalt carbide catalysts were synthesized by exposure of Co/Al2O3 catalyst to CH4 at different temperatures from 300 °C to 800 °C. The physicochemical properties of the carbide catalysts (CoCx/Al2O3) were evaluated by different characterization methods. The catalytic performances of the catalysts were investigated in an autoclave reactor to determine the role of cobalt carbides on the CO conversion and product distribution during the reaction. XRD and XPS analysis confirmed the presence of Co2C in the prepared catalysts. The higher carbidation temperature resulted in the decomposition of methane into hydrogen and carbon, and the presence of graphitic carbon was confirmed by XRD, XPS, SEM, and Raman analysis. The Co2C also decomposed to metallic cobalt and carbon, and the content of cobalt carbide decreased at higher carbidation temperatures. Higher content of Co2C resulted in a lower CO conversion and higher selectivity to light alkanes, mainly methane. The higher carbidation temperature resulted in the decomposition of Co2C to metallic cobalt with higher activity in the FT reaction. The CO conversion increased by increasing the carbidation temperature from 300 °C to 800 °C, due to the higher content of metallic cobalt. In the presence of pure hydrogen, the Co2C could be converted mainly into hexagonal, close-packed (hcp) Co with higher activity for dissociative adsorption of CO, which resulted in higher catalyst activity and selectivity to heavier hydrocarbons.

Intensification of high-flux Fischer-Tropsch synthesis with axial gradient Co-loading FeCrAl monolith catalysts

FeCrAl monolith catalysts are suitable for high-flux low-temperature Fischer-Tropsch synthesis (LT-FTS) due to their high thermal conductivity and low pressure drop at high gas hourly space velocity (GHSV). In this study, the reaction and thermal performance of the catalysts with increasing Co-loading (MCINC) and decreasing Co-loading (MCDEC) at different GHSV were studied by experiment and numerical simulation. The results showed that the reaction performance of MCDEC was slightly better than that of MCINC at 28000 h−1, while the thermal performance of MCDEC was much better than MCINC. The reason was explained by the heat transfer mechanism. The dominant heat transfer mode turned to the axial convective heat transfer at 28000 h−1. The powerful axial convective heat transfer improved the transfer of the reaction heat toward the outlet and decreased the temperature of MCDEC. Conversely, it exacerbated the heat accumulation near the outlet of MCINC. Therefore, MCDEC was more suitable than MCINC for the better thermal management of high-flux LT-FTS. These results demonstrated that designing the axial gradient of Co-loading according to the GHSV is a promising approach for the thermal intensification in LT-FTS.

Effects of Potassium Loading over Iron–Silica Interaction, Phase Evolution and Catalytic Behavior of Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

Potassium (K) promoter and its loading contents were shown to have remarkable effects on the Fe–O–Si interaction of precipitated Fe/Cu/K/SiO2 catalysts for low-temperature Fischer-Tropsch synthesis (FTS). With the increase in K content from 2.3% (100 g Fe based) up to 7% in the calcined precursors, Fe–O–Si interaction was weakened, as reflected by ATR/FTIR, H2-TPR and XPS investigations. XRD results confirmed that the diffraction peak intensity from (510) facet of χ-Fe5C2 phase strengthened with increasing K loading, which indicates the crystallite size of χ-Fe5C2 increased with the increase in K contents either during the syngas reduction/carburization procedure or after FTS reaction. H2-TPH results indicated that more reactive surface carbon (alpha-carbon) was obtained over the higher K samples pre-carburized by syngas. Raman spectra illustrated that a greater proportion of graphitic carbon was accumulated over the surface of spent samples with higher K loading. At the same time, ATR-FTIR, XRD and Mössbauer spectra (MES) characterization results showed that a relatively higher level of bulk phase Fayalite (Fe2SiO4) species was observed discernibly in the lowest K loading sample (2.3 K%) in this work. The catalytic evaluation results showed that the CO conversion, CO2 selectivity and O/P (C2–C4) ratio increased progressively with the increasing K loading, whereas a monotonic decline in both CO conversion and O/P (C2–C4) ratio was observed on the highest K loading sample during c.a. 280 h of TOS.

Highly Efficient ZIF-67-Derived PtCo Alloy–CN Interface for Low-Temperature Aqueous-Phase Fischer–Tropsch Synthesis

Designing new materials for selective Fischer–Tropsch synthesis (FTS) is an elegant way to enhance local feedstock utilization like biomass and waste. In this approach, we have designed a thermally and chemically stable bimetallic PtCo/NC hybrid nanocomposite catalyst derived from a zeolitic imidazolate framework (ZIF-67, which contains cobalt as a metal center) through carbonization for low-temperature (413–473 K) aqueous-phase Fischer–Tropsch synthesis (AFTS). The selectivity of the desired range of hydrocarbons is adjusted using a highly dispersed PtCo bimetallic alloy, which facilitates extraordinary reduction of a metal oxide to active species by the synergic effect under the AFTS reaction conditions. The ZIF-derived catalyst tested in this study exhibited the highest activity to date for very low temperatures (433 K) in aqueous-phase Fischer–Tropsch synthesis with CO conversion rates between 0.61 and 1.20 molCO·molCo–1·h–1. Insights of the remarkable catalyst activity were examined by in situ X-ray photoelectron spectroscopy (XPS) studies corroborated by density functional theory (DFT) calculation. The bimetallic Co3Pt (111) surface was found to be highly active for the C–C coupling reaction between surface-adsorbed C and CO, forming a CCO intermediate with a very low activation barrier (Ea = 0.37 eV), in comparison to the C–C coupling activation barrier obtained over the Co (111) surface (Ea = 0.87 eV). This unique approach and observations create a new path for developing next-generation advanced catalyst systems and processes for selective low-temperature FTS.

Robust simulation-optimization framework for synthesis and design of natural gas downstream Incorporating renewable hydrogen network under uncertainty

Many intrinsic uncertainties are part of natural gas downstream synthesis, design, and operation. This work extends the earlier developed deterministic model to account for new decision variables, unit operations, and uncertainty in the network. The uncertainty includes the feedstock composition and flowrate, utility requirements, by-products, and final product market price. The proposed two-stage stochastic model includes new major processing units (helium recovery units), hydrogen production via renewable technologies (biomass gasification, water electrolysis), and operating modes. The stochastic formulation simultaneously considers uncertainty in 12 different model parameters. The model's first stage aims to find the optimal network's design variables, such as processing units, technologies, and operating modes common to all scenarios. The second stage is concerned with deriving operational variables, for example, the network's overall inlet feedstock flowrates, individual units' inlet flowrates, and units' capacity. Outcomes obtained for a range of uncertain material/energy feedstock and products/by-products market prices result in higher expected operating profits than the equivalent deterministic model. The analysis's key takeaways show that the most prevailing network consists of two syngas technologies: (1) auto-thermal reforming to feed a low-temperature Fischer Tropsch synthesis unit and (2) steam methane reforming for hydrogen production. Additionally, renewable hydrogen is produced via electrolysis and biomass gasification. There is an improvement of 2.22% in the objective function value using the stochastic approach instead of the deterministic.

Mass transfer modeling and sensitivity study of low-temperature Fischer-Tropsch synthesis

An industrial-scale Fischer–Tropsch (FT) slurry bubble column reactor (SBCR) was theoretically investigated, emphasizing the mass transfer between the gas and slurry phases. In this endeavor, three different driving forces for mass transfer (the impetus behind the motion of species mass) were proposed: one based on Henry’s law and two based on rigorous phase equilibrium. The mass transfer model based on Henry’s law relies on the solvent, which here was specified as a paraffin with carbon chain length in the range of 16–36. The conversion level was found to increase with increasing carbon chain length. On the other hand, the mass transfer models based on phase equilibrium do not require identifying a solvent, which is advantageous for the Fischer–Tropsch synthesis (FTS) where the large number of compounds render the solvent a vague and ambiguous concept. Here, the phase equilibrium was computed with the Peng–Robinson (PR) and the perturbed-chain statistical associating fluid theory (PC-SAFT) equations of state (EoSs); however, the proposed concept is generic and easily extended to other EoSs and activity coefficient-based models. With all three mass transfer formulations, the conversion level increased with increasing pressure and decreased with increasing temperature. Furthermore, increasing the catalyst loading did not increase the conversion level, whereas increasing the mass transfer coefficient did increase the conversion level. It was concluded that the reactor operates in the mass transfer limited regime rather than the kinetically limited regime. The mass transfer model based on Henry’s law was the least computationally expensive to evaluate, followed by the PR and PC-SAFT EoSs in increasing order; however, the mass transfer models based on the PR and PC-SAFT EoSs are capable of predicting the thermodynamic spontaneity of forming additional phases, which Henry’s law is incapable of.

The “Innovation Liquid Energy” (ger. “Innovation Flüssige Energie” - IFE) Project: Development of a 1MW Power-to-Liquid Plant Based on Co-SOC Electrolysis and Fischer-Tropsch Synthesis

The European climate protection program adopted in 2018 targets for a reduction in greenhouse gas emissions from the current 20% to 40% (compared to 1990) by 2030 ([1]), together with a simultaneous increase in the share of energy from renewable sources from the current 20% to 32%. In the transport sector, an increase in the share of renewable fuels from the current 10% to 14% is aimed for, with a maximum of 7% of this being Generation 1 fuels. Therefore, additional solutions such as power-to-liquid (PtL) fuels are needed to generate an immediate impact on existing fleets in order to achieve European and global CO2 emission targets in mobility.The overall objective of the IFE (Innovation Liquid Energy) project is the development and realization of a Power-to-Liquid plant with a combined water and carbon dioxide high-temperature electrolysis (Co-SOEC) and a Fischer Tropsch synthesis for the production of synthetic fuel. By coupling these two processes in a way which enables heat integration, an increase of the overall electrical efficiency to 55% is to be achieved. The overall plant with a nominal electrolyser power of around 1 MW will constitute of several parts. Carbon dioxide is extracted from industrial waste gas or from a biogas/biomass plant and fed into the electrolyser process. There, a synthesis gas of hydrogen and carbon monoxide is produced based on an innovative Co-SOEC unit with an efficiency higher than 80%. In the next process stage, the syngas is fed into a low-temperature Fischer-Tropsch synthesis, where syncrude is produced with predominantly liquid and paraffinic products. The estimated output of Fischer-Tropsch products is around 500.000 L diesel-equivalent. The diesel fraction is targeted to meet the required quality of the EN15940 standard for alternative paraffinic diesel fuel.The present work shows the status of the project and how specific challenges such as the reuse of the tail gas, the reuse of the aqueous product fraction and heat integration are addressed. Thereby a focus on the development of the co-SOEC unit and the optimization of the overall process towards highest efficiencies is being laid. Furthermore a techno-economic view on the potential cost of Fischer-Tropsch products is given, where, dependent on the electricity cost and full-load operating hours of the plant, FT-diesel costs in the range of 1-3 € seem reasonable (without tax and margin).[1] The European parliament and the council of the European Union:DIRECTIVE (EU) 2018/2001, (L 328/82), Brüssel, 2018 https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018L2001&from=EN

Performance comparison between washcoated and packed-bed monolithic reactors for the low-temperature Fischer-Tropsch synthesis

Washcoating and packing of Co-Re catalyst particles have been employed as structuring methods of parallel channel monoliths used in the low-temperature Fischer-Tropsch synthesis (FTS). These methods were compared with regard to catalyst hold-up, heat transfer properties and pressure drop. Reactors output was assessed in terms of CO conversion, CH4 selectivity and productivity of C5+ hydrocarbons. Washcoating led to much lower pressure drops, but also resulted in considerably lower catalyst inventory. As for the reactors performance (volumetric and per catalyst mass C5+ productivities), the washcoated monoliths were more effective than the packed-bed ones. This has been attributed to their more favorable hydrodynamic behavior that facilitates the drainage of the reaction products (liquids and waxes) through the central hollow of the channels thus reducing the extra-pellet diffusional limitations. For both catalyst configurations, it has been found that the productivity of C5+ per catalyst mass unit increases as the characteristic diffusion length increases within the range of values considered in this study (below 150 µm). This indicates that a moderate level of internal mass transport restrictions is beneficial for the low-temperature FTS, which has been explained in terms of the effects of diffusional limitations on the H2/CO molar ratio, and that of this ratio on the FTS kinetics. The possible influence of thermal effects on these results has been numerically and experimentally discarded.

Development of a kinetic model for low temperature Fischer-Tropsch synthesis

A challenge to the simulation of the Fischer–Tropsch reaction system is the lack of reliable kinetic models which correctly account for the deviations from ideal polymerisation behaviour. The current trend in literature is to attribute these deviations to kinetic effects only. This ignores that the reactions in Fischer–Tropsch synthesis contain many aspects of an equilibrium-controlled process. This arises since the rate of chain growth is much faster than the rate of monomer formation from CO. Consequently, the production distribution and the observed trends in reaction behaviour can be described by thermodynamics. A model has been developed to describe the reaction kinetics wherein each rate expression for n-paraffin and 1-olefin formation is expressed as equilibrium-limited. This arises because of the linear variation of the ideal gas Gibbs free energy of formation with carbon number. It was therefore shown that the high methane yield, low ethene yield and the decrease in olefin-to-paraffin ratio with carbon number could effectively be captured in a light weight and tractable manner. The model preserves the polymerisation character of reaction and has been extended to include products of carbon number up to C81. The equilibrium basis of the model also successfully describes the dominant trends in the product distribution as a function of CO conversion, temperature and pressure.

Fischer–Tropsch Synthesis in the Presence of Catalysts Based on Unmodified Iron Ores

The use of commercial magnetite-type iron ore and of ferriferous quartzite type ore as catalysts for low-temperature Fischer–Tropsch synthesis is described. According to the results of chemical analysis, the ores mainly contained iron magnetite, carbon, and also baddeleyite (ZrO2 + HfO2) and hatchettolite (Ta2O5 + Nb2O5 + U3O8). The ore samples with the highest iron content (48–59%) and the lowest sulfur content (0.1% and less) showed activity in the Fischer–Tropsch synthesis without additional modification in the commercial form. The yield of liquid products in the synthesis performed on the most active samples of ore catalysts exceeded 100 g m–3 at the СО conversion of approximately 60%. The ore activity in the Fischer–Tropsch synthesis may be associated with the fact that these natural mineral formations contain oxides exerting a promoting effect when using the ores as catalysts.

Experimental Determination of H2 and CO Diffusion Coefficients in a Wax Mixture Confined in a Porous Titania Catalyst Support.

The ability to measure and predict molecular diffusion coefficients in multicomponent mixtures is not only of fundamental scientific interest but also of significant relevance in understanding how catalytic processes proceed. In the present work, the direct measurement of the molecular diffusion of H2 and CO gas-phase species diffusing in n-alkane mixtures using pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) methods is reported. The work is of direct relevance to Fischer-Tropsch (FT) catalysis, with the measurements being made of the gas-wax system with the wax in both the bulk liquid state and when confined within a titania catalyst support, at temperatures and pressures typical of low-temperature FT synthesis. Molecular diffusion coefficients of H2 and CO within wax-saturated porous titania in the range (1.00-2.43) × 10-8 and (6.44-8.50) × 10-9 m2 s-1, respectively, were measured in the temperature range of 140-240 and 200-240 °C for H2 and CO, respectively, at a pressure of 40 bar. The wax mixture was typical of a wax produced during FT catalysis and had a molar average carbon number of 36. It is shown that the hydrogen diffusion coefficient within this wax mixture is consistent, to within experimental error, with the hydrogen diffusion coefficient measured in pure single-component n-hexatriacontane (n-C36) wax; this result held with the waxes in the bulk liquid state and when confined within the porous titania. The tortuosity of the porous titania was also measured using PFG NMR and found to be 1.77; this value is independent of temperature. The ability of existing correlations to predict these experimentally determined data was then critically evaluated. Although the Wilke-Chang correlation was found to underestimate the molecular diffusion coefficients of both H2 and CO diffusing in the wax in both the bulk state and when confined within the porous titania, parameterized correlations based on the rough hard sphere model, having accounted for the experimentally determined tortuosity factor, predicted the H2 and CO diffusion within bulk and confined wax to within 3%.

Diffusion-dependent upgrading of hydrocarbons synthesized by Co/zeolite bifunctional Fischer–Tropsch catalysts

The design of efficient zeolite-supported Co catalysts is essential for the further development of the one-step production of liquid fuels via the low-temperature Fischer–Tropsch synthesis (FTS). Herein, Co/zeolite catalysts were prepared from zeolites SSZ-13, ZSM-22, ZSM-11, ZSM-5, Mordenite, and Y. Their textural and acidic properties, Co dispersion, and internal diffusion behaviors were comprehensively analyzed, along with their FTS product mixtures. Counterintuitively, the degree of isomerization and hydrocarbon decomposition did not correlate with the acidic properties of the zeolite support. Instead, catalysts with high characteristic diffusivity delivered product mixtures with high degree of isomerization and decomposition, suggesting that the access of paraffinic hydrocarbons to the internal acid sites of the zeolite determines the upgrading performance of the bifunctional Co/zeolite catalyst in the low-temperature FTS reaction. Hence, the present findings support upcoming efforts on the design of new and effective FTS catalysts.

Techno-economic prospects for producing Fischer-Tropsch jet fuel and electricity from lignite and woody biomass with CO2 capture for EOR

This study explores the prospective techno-economic performance of facilities that produce low- and net-negative-carbon liquid transportation fuels and electricity with CO2 capture for enhanced oil recovery. The lignite and biomass-to-jet fuel process is based on KBR’s TRIG gasifier, Rectisol (for sulfur removal and CO2 capture), fixed-bed low temperature Fischer-Tropsch synthesis of liquid fuels, and Brayton/Rankine combined cycles to convert synthesis/refining off-gases and waste heat to electricity. This work leverages a recent, highly-detailed assessment of a prospective first-of-a-kind (FOAK) demonstration facility to develop highly detailed Aspen Plus process simulations for nine prospective Nth-of-a-kind (NOAK) plant equipment configurations. Component-level capital costs from the FOAK study are scaled and adjusted to reflective prospective learning-by-doing to estimate capital costs for the NOAK designs. NOAK plant economic performance is found to be largely insensitive to variations in plant configurations and electricity output fraction, but biomass input fraction significantly affects profitability. Facilities that consume only carbon–neutral biomass, with no lignite co-feed, have significantly net-negative carbon emissions and the most favorable prospective economics when carbon emissions are priced. For these facilities, the crude oil price required for plant economic viability falls rapidly from $100/bbl as carbon emission prices increase above $120/tonne CO2eq. In general, plants that co-fire lignite with biomass are less profitable (than 100% biomass plants) due to their higher net greenhouse gas emissions.