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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Reaction rate and products for the reaction O/3P/ + H2CO

A study of reaction kinetics of O + H2CO in a discharge-flow system using mass spectrometric detection of reactants and products is presented. It was performed under both oxygen-atom-rich and formaldehyde-rich conditions over the 296 to 437 K range, showing that the global bimolecular rate constant is in agreement with other studies. This study differs from others in that the reaction products can be observed, and a substantial yield of a primary reaction product was measured with a mass spectral peak at m/e=44. This suggests that the global reaction rate probably consists of combination, as well as of simple abstraction. For the combination, one hypothesis is that triplet dioxymethylene is formed which polymerizes to triplet formic acid; the vibrationally excited triplet formic acid may decompose to form several sets of products, including HCO + OH and HCO2 + H.

Chang, J. S.↗
DOE OSTI2020

Implementation of the Glycolate Destruction Process with Sodium Permanganate in the Defense Waste Processing Facility (DWPF) - 20141

The Savannah River Site (SRS) seeks to replace formic acid with glycolic acid as a chemical reductant in the Defense Waste Processing Facility (DWPF), where borosilicate glass is mixed with high-level radioactive waste, melted at high temperatures, then poured into stainless steel canisters for safe storage. Prior research and development have demonstrated the feasibility and advantages of the new nitric-glycolic acid flowsheet over the current nitric-formic acid flowsheet to chemically adjust the radioactive sludge slurry waste in the Sludge Receipt and Adjustment Tank (SRAT) prior to vitrification. Use of glycolic acid reduces hydrogen and ammonia generation during the reduction process, thus reducing flammability hazards and purge requirements in the DWPF processing vessels. In addition, glycolic acid will support the new Salt Waste Processing Facility (SWPF) by allowing for receipt of higher volumes of waste due to reduction of flammable gases, increased boil-up rates in the vessels, and easing the processing of future sludge batches containing high levels of mercury. However, during DWPF operations, trace amounts of glycolate are anticipated to be entrained in the recycle stream and sent to the Concentration, Storage, and Transfer Facilities (CSTF) via the Recycle Collection Tank (RCT). The RCT receives condensate from the Slurry Mix Evaporator Condensate Tank (SMECT) and Off-gas Condensate Tank (OGCT) that may contain unreacted glycolate. A literature review found the potential for hydrogen generation due to thermolysis of glycolate in caustic CSTF conditions. Savannah River National Laboratory (SRNL) conducted several tests on simulant and radioactive waste from various tanks at SRS and confirmed that glycolate added to waste at concentrations of approximately 1000 mg/L and higher generates hydrogen through thermolysis. There are potential operating scenarios in the future where glycolate concentration could exceed 1000 mg/L in the 2H Evaporator Drop Tank, the highest accumulation point for DWPF organics received via recycle. These findings presented a need to develop another process to mitigate the impact of glycolic acid to the CSTF. Several DWPF compatible options were evaluated for their ability to destroy glycolate in the DWPF recycle stream under various processing conditions, thereby mitigating its introduction to the CSTF. Downselection testing identified sodium permanganate as the most promising and simplest option to oxidize glycolate. It has been demonstrated to be effective in various RCT simulant compositions, operating temperatures, oxidant addition rates, solution pH, and initial glycolate concentrations. A feasibility study identified existing tanks within the facility that could be used for receiving and storing the commercially available sodium permanganate, as well as feeding it to the RCT for processing. The use of existing equipment as well as the ability to purchase the pre-mixed chemical reduces implementation and operational complexity. The downstream impacts of the sodium permanganate reaction were also evaluated and demonstrated to have minimal impact on other chemical species present in the RCT and CSTF, as well as on the materials of construction of the RCT and CSTF vessels and associated piping and instrumentation. Future work is in progress to validate the glycolate destruction process with testing in actual radioactive RCT waste before implementation in DWPF. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1975

Photochemical synthesis of simple organic free radicals on simulated planetary surfaces - An ESR study

Electron spin resonance (ESR) spectroscopy provided evidence for formation of hydroxyl radicals during ultraviolet photolysis (254 nm) at -170 C of H2O adsorbed on silica gel or of silica gel alone. The carboxyl radical was observed when CO or CO2 or a mixture of CO and CO2 adsorbed on silica gel at -170 C was irradiated. The ESR signals of these radicals slowly disappeared when the irradiated samples were warmed to room temperature. However, reirradiation of CO or CO2, or the mixture CO and CO2 on silica gel at room temperature then produced a new species, the carbon dioxide anion radical, which slowly decayed and was identical with that produced by direct photolysis of formic acid adsorbed on silica gel. The primary photochemical process may involve formation of hydrogen and hydroxyl radicals. Subsequent reactions of these radicals with adsorbed CO or CO2 or both yield carboxyl radicals, CO2H, the precursors of formic acid. These results confirm the formation of formic acid under simulated Martian conditions and provide a mechanistic basis for gauging the potential importance of gas-solid photochemistry for chemical evolution on other extraterrestrial bodies, on the primitive earth, and on dust grains in the interstellar medium.

Tseng, S.-S.↗
DOE OSTI2026

Improved Microalgal Carbon Utilization Efficiency via Integrated CO 2 Electro-Conversion to Formate and Microalgal Sequestration

This project developed a process to convert industrial carbon dioxide (CO 2 ) emissions into high-value, sustainable products through genetically engineered algae cultivation. While traditional microalgae cultivation depends on sparging CO 2 gas through water, this method is often inefficient because much of the gas escapes into the atmosphere before the algae can consume it. To overcome this challenge, the project designed an integrated system that first uses a CO 2 to formic acid electrolyzer to convert CO 2 into water-soluble formic acid/formate, then introduces formic acid/formate into the algae pond for cultivation, which allows the algae to access and utilize nearly all of the provided carbon, greatly increasing the efficiency of carbon utilization. The project team has successfully scaled up the CO 2 to formic acid electrolyzer from lab-scale to 1000 cm² and demonstrated industrially relevant current densities with the scaled-up electrolyzers using a CO 2 source that simulates industrial CO 2 waste.

42 ENGINEERING↗
DOE OSTI2022

Green synthesis of cellulose formate and its efficient conversion into 5-hydroxymethylfurfural

5-hydroxymethylfurfural (HMF) production from cellulose is a hot topic, while the rigidity of cellulose limits its efficient conversion into HMF. Cellulose formate has exhibited the great potential for HMF production but it’s synthesis via direct formylation of cellulose in formic acid is difficult. We reported a green synthetic route of cellulose formate and its efficient conversion into HMF. Ball milled cellulose formate (BCF) was synthesized via ball milling followed by formylation in formic acid at 80 °C for 0.5 h. The structure of BCF was thoroughly characterized and BCF was subsequently converted to HMF catalyzed by AlCl3 and HCl in dimethyl sulfoxide (DMSO)-H 2 O media. Results showed that ball milling of cellulose for 1–1.5 h efficiently deconstructed its crystallinity and degree of polymerization, boosting its further formylation and catalytic conversion. An overall 66.9% HMF yield from cellulose was achieved at 150 °C for 20 min using BCF derived from cellulose ball milled for 1.5 h as the substrate. BCF exhibits high reactivity toward HMF due to its excellent solubility and accessibility in DMSO-H 2 O media, and the release of formic acid in reaction further facilitates HMF production. BCF synthesized with different ball milling times shows different degrees of substitution of formyl groups, which could serve as an indicator and regulate the HMF production. The green synthesis of cellulose formate creates an efficient pathway for HMF production.

5-hydroxymethylfurfural↗
NASA NTRS1999

Hydrous pyrolysis of polycyclic aromatic hydrocarbons and implications for the origin of PAH in hydrothermal petroleum

Polycyclic aromatic hydrocarbons (PAH) are found at high concentrations in thermally altered organic matter and hydrothermally generated petroleum from sediment-covered seafloor hydro-thermal systems. To better understand the factors controlling the occurrence of PAH in thermally altered environments, the reactivities of two PAH, phenanthrene and anthracene, were investigated in hydrothermal experiments. The compounds were heated with water at 330 degrees C in sealed reaction vessels for durations ranging from 1 to 17 days. Iron oxide and sulfide minerals, formic acid, or sodium for-mate were included in some experiments to vary conditions within the reaction vessel. Phenanthrene was unreactive both in water alone and in the presence of minerals for up to 17 days, while anthracene was partially hydrogenated (5-10%) to di- and tetrahydroanthracene. In the presence of 6-21 vol % formic acid, both phenanthrene and anthracene reacted extensively to form hydrogenated and minor methylated derivatives, with the degree of hydrogenation and methylation increasing with the amount of formic acid. Phenanthrene was slightly hydrogenated in sodium formate solutions. The hydrogenation reactions could be readily reversed; heating a mixture of polysaturated phenanthrenes resulted in extensive dehydrogenation (aromatization) after 3 days at 330 degrees C. While the experiments demonstrate that reaction pathways for the hydrogenation of PAH under hydrothermal conditions exist, the reactions apparently require higher concentrations of H2 than are typical of geologic settings. The experiments provide additional evidence that PAH may be generated in hydrothermal systems from progressive aromatization and dealkylation of biologically derived polycyclic precursors such as steroids and terpenoids. Furthermore, the results indicate that PAH initially present in sediments or formed within hydrothermal systems are resistant to further thermal degradation during hydrothermal alteration.

NASA Discipline Exobiology↗
DOE OSTI2023

Prolonged Stability of Pb-Catalyzed CO 2 Electroreduction to Methyl Formate in Acidic Methanol

Electrochemical CO 2 reduction from renewable energy is a promising route to mitigate greenhouse gas emissions from waste sources while generating value-added products. CO 2 electroreduction in methanol is particularly interesting due to the increased CO 2 solubility compared to water and the propensity to form methyl formate, a product absent in aqueous electrolysis. Here, four factors have been identified as critical to achieving prolonged high selectivity for methyl formate production on a Pb cathode in methanol: high pH near the electrode, low bulk pH, low water content, and regeneration of Pb 2+ sites. Increasing concentration of the formic acid product was observed to induce a selectivity shift towards hydrogen, which was mitigated by the in-situ conversion of the formic acid to methyl formate via an esterification reaction. Furthermore, co-electrolysis of CO 2 with dilute molecular oxygen (4% O 2 ) led to Pb catalyst repair through in-situ surface oxidation. Using CO 2 and dilute O 2 along with single-pass catholyte flow to maintain a low formic acid concentration, sustained high selectivity for methyl formate was attained at ~60% faradaic efficiency at -20 mA cm -2 for over 72 hours.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2010

Experimental Study of Abiotic Organic Synthesis at High Temperature and Pressure Conditions: Carbon Isotope and Mineral Surface Characterizations

Abiotic organic synthesis processes have been proposed as potential mechanisms for methane generation in subseafloor hydrothermal systems on Earth, and on other planets. To better understand the detailed reaction pathways and carbon isotope fractionations in this process under a wide range of physical and chemical conditions, hydrothermal experiments at high temperature (750 C) and pressure (0.55 GPa) were performed using piston cylinder apparatus. Formic acid was used as the source of CO2 and H2, and magnetite was the mineral catalyst. The chemical and carbon isotopic compositions of dissolved organic products were determined by GC-C-MS-IRMS, while organic intermediaries on the mineral catalyst were characterized by Pyrolysis-GC-MS. Among experimental products, dissolved CO2 was the dominant carbon species with a relative abundance of 88 mol%. Dissolved CH4 and C2H6 were also identified with a mole ratio of CH4 over C2H6 of 15:1. No dissolved CO was detected in the experiment, which might be attributable to the loss of H2 through the Au capsule used in the experiments at high temperature and pressure conditions and corresponding conversion of CO to CO2 by the water-gas shift reaction. Carbon isotope results showed that the 13C values of CH4 and C2H6 were -50.3% and -39.3% (V-PDB), respectively. CO2 derived from decarboxylation of formic acid had a (sigma)C-13 value of -19.2%, which was 3.2% heavier than its source, formic acid. The (sigma)C-13 difference between CO2 and CH4 was 31.1%, which was higher than the value of 9.4% calculated from theoretical isotopic equilibrium predictions at experimental conditions, suggesting the presence of a kinetic isotope effect. This number was also higher than the values (4.6 to 27.1%) observed in similar experiments previously performed at 400 C and 50 MPa with longer reaction times. CH4 is 11.0% less enriched in C-13 than C2H6. Alcohols were observed as carbon compounds on magnetite surfaces by Pyrolysis-GC-MS, which confirms the hypothesis regarding the reaction pathways of hydrothermal abiotic organic synthesis proposed by Fu et al. (2007, 2008). In this proposed pathway, hydroxymethylene (-CHOH) groups serve as organic intermediaries on mineral surfaces while dissolved H2 serves as a chain terminator/breaker to generate short chain hydrocarbons and oxygenated compounds. This pathway is different from the carbide polymerization theory of Fischer- Tropsch-type (FTT) synthesis in a gas phase. The observed increase of (sigma)C-13 values of C1 and C2 alkanes with carbon number in our hydrothermal experiments can be readily interpreted by hydroxymethylene pathway, and might be used to differentiate between hydroxymethylene and carbide polymerization pathways. Carbon isotope analysis of alcohols on mineral catalyst surfaces is under way to provide further constraints on formation of organic compounds by FTT in hydrothermal systems.

Fu, Qi↗
NASA NTRS1999

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

Non-NASA Center↗
DOE OSTI2025

Microwave-assisted delignification for improved cellulose production

This study aims to develop microwave (MW) technologies to improve the paper pulping process, decreasing both chemical and thermal energy requirements. The overall objective is to explore an efficient process that aids in the delignification of paper pulp, reducing energy needs and chemical intensity. The experimental variables evaluated during the MW-assisted digestion process include formic acid concentration, time, temperature, digestion cycles, and the formic acid to paper ratio. This research investigates the potential of MW technology to create a more sustainable and efficient cellulose production method.

microwave heating↗
NASA NTRS1990

New observations of interstellar organic molecules

Discussed here are new observations of 3-carbon-containing interstellar molecules which play an important role in the chemistry of dense molecular clouds: protonated carbon dioxide, formic acid, and propynal. In 1984 a new oxide of carbon, C3O, was discovered in the interstellar medium (Matthews et al. 1984; Brown et al. 1985). Theoretical models suggest that C3O is produced by dissociative electron recombination with the ion H3C3O+. Although no laboratory data for the branching ratios of such a recombination exist, it seemed to us likely that additional products would include H2C3O. This molecule has more than one isomeric form, but one stable species is propynal (HC2CHO), which had been suggested as a possible interstellar molecule by Winnewisser (1973). In observations at the National Radio Astronomy Observatory 43 m telescope in Green Bank earlier this year, researchers detected a line in the cold cloud TMC-1 which they assign to the 2(0,2)-1(0,1) transition of propynal. The observed line agrees with the laboratory frequency to well within the experimental uncertainty a few parts in 10 to the 7th power. Researchers sought and failed to detect the corresponding 2(1,1)-1(1,0) line, which is understandable given the presence of both a and b components of the electric dipole moment in propynal. The b type transitions will drain population from energy levels with K(sub p) does not equal 0 into the K(sub p) equal 0 stack. If the researchers' assignment is correct, this is the first interstellar detection of propynal. Assuming typical rotational temperatures for TMC-1 and that the line is optically thin, the column density determined is about 5 times 10 to the 12th power cm to the -2nd power, or about three times that for C3O. Formic acid (HCOOH) was the first organic acid to be observed in the interstellar medium, in the Galactic center source Sgr B2. The only other interstellar detection has been recently made in the giant molecular cloud in Orion. As part of the same project that led to the detection of propynal, researchers sought formic acid in the nearby, cold dark clouds TMC-1 and L134N. It is seen only in L134N. This difference between the two clouds appears to be consistent with a model in which the oxygen/carbon ratio is higher in L134N. This would be consistent with the higher abundances for SO and SO2, observed in that cloud, and the higher abundances of many carbon-rich species in TMC-1 (Irvine et al. 1985).

Irvine, W. M.↗
DOE OSTI2025

Effect of Ambient Organic Acids on the Water Structure at ${\rm TiO}_{2}$ Interfaces

A molecular-level understanding of the effects of ambient organic compounds on the wettability of titanium dioxide ( ${\rm TiO}_{2}$ ) surfaces is relevant to many of its energy-related and environmental applications. Herein, we focus on two common atmospheric carboxylic acids, formic and acetic acid, and characterize their adsorption/ desorption at the aqueous interfaces of anatase and rutile ${\rm TiO}_{2}$ using molecular dynamics with an ab initio deep neural network potential. Our simulations show that these acids prefer to be localized in the interfacial water layers close to the ${\rm TiO}_{2}$ surface where they are stabilized by the interaction/exchange of their acid proton with a surface oxygen, rather than chemisorb at the surface Ti sites by displacing the adsorbed water. Notably, these acids make the surface of anatase hydrophobic, whereas the larger fraction of adsorbed water dissociation can offset their effect on rutile. Furthermore, these results provide a picture where carboxylic acids control the wettability of ${\rm TiO}_{2}$ largely through acid-base chemistry at the interface rather than chemisorption on the oxide surface, a finding that can help improve the design of self-cleaning surfaces and photocatalytic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Cross-aldol condensation on missing linker sites of metal–organic framework UiO-66

Missing linkers induce coordinatively unsaturated Lewis acid-base pair sites in metal–organic frameworks such as UiO-66 (Zr). The Lewis acid-base pair is induced by replacing the benzene dicarboxylic acid linker with formic acid, which subsequently is thermally decomposed. The concentration of coordinatively unsaturated Zr 4+ cations was titrated with acetone. In parallel to their concentration, the catalytic activity increased while the selectivity for aldol condensation between furfural and acetone remained constant. The missing linkers generate a complex ensemble consisting of an (at least partly) accessible Zr 4+ cation surrounded by oxygen, catalyzing the cross-aldol condensation. As a result, density functional theory calculations, matching the experimental findings provide a more detailed understanding of the elementary steps during the condensation reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Solvent selection for biphasic extraction of 5-hydroxymethylfurfural via multiscale modeling and experiments

We introduce a comprehensive conceptual framework for selecting solvents for reactive extraction in biphasic organic-water systems and demonstrate it for the separation of HMF (5-hydroxylmethylfurfural), a platform chemical produced in the acid-catalyzed dehydration of hexoses. We first perform in silico screening of ~2500 solvents, from the ADFCRS-2018 database using the ADF COSMO-RS implementation, and classification, based on the solvent partition coefficient. We then determine experimentally the partition coefficients for HMF, fructose, and products of HMF rehydration (levulinic acid (LA), and formic acid (FA)), the mutual water-organic solvent solubilities, and the separation factors in >50 select solvents spanning multiple homologous series at room temperature and a typical reaction temperature with in situ sampling. We find that COSMO-RS is excellent for screening purposes (typical error in most cases within a factor of ~2). Increased temperatures lead to significant reduction in partitioning, and room temperature measurements are clearly inadequate for solvent selection. Upon down selecting classes of solvents based on separation performance, we perform experimental thermal stability and reaction compatibility studies of a small set of solvents at relevant reactive-extraction temperatures. We discover that many substituted phenols exhibit an order-of-magnitude increase in partitioning compared to conventional solvents due chiefly to hydrogen bond interactions and show the necessary stability but retain a significant fraction of water and LA, factors that need to be considered in technoeconomic analysis. In contrast, anilines, aldehydes, and acids are good to excellent regarding separation but incompatible with this specific reaction medium. Furthermore, this multifaceted framework can be extended to other biomass-derived products and processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1997

Computer-aided design of a proton pump

The use of transmembrane proton gradients in energy transduction is an almost universal feature of life on earth. These proton gradients are established and maintained by specialized assemblies of proteins which actively pump protons across membranes. One broad class of proton pumps uses captured light energy to drive the proton pumping. Our goal is to elucidate the minimum structural requirements of a light-driven proton-pump. There are two basic components to a simple light-driven proton pump: a source of photo-generated protons and a "gate-keeper" which prevents these protons from reattaching themselves to their source. A wide variety of molecules in the membrane, even as simple as polycyclic aromatic hydrocarbons, are capable of releasing protons when illuminated. Our work is therefore focused on the design of the "gate-keeper." Our initial model involves a pair of proton acceptors, coupled to each other by a transient water bridge, and supported in the membrane by a small bundle of peptide helices. Upon illumination, the proton source transfers its proton to the:- first acceptor of the gate-keeper. While the reverse reaction is highly probable, all that is needed to ensure irreversibility is a nonvanishing probability that the proton will be transferred to the second acceptor across a transient water bridge. Back transfer of the proton to the first acceptor, and thence to the proton source, is impeded by the free energy required to move the proton uphill towards the. proton source and by the disruption of the transient water bridge. As a prototypical water-bridged proton transfer system, we are studying the transfer of a proton across a water bridge from a formic acid to a formate anion. With a pK(sub alpha), of 3.7. formic acid is a good model for the acidic amino acids glutamate and aspartate which are good candidates for gate-keeper proton acceptors. Simulations of proton transfer reactions in a membrane are complicated by the quantum mechanical nature of the process breaking and forming chemical bonds.

New, Michael H.↗
DOE OSTI2020

A Review of the Use of Immobilized Ionic Liquids in the Electrochemical Conversion of CO2

This paper is a review on the application of imidazolium-based ionic liquids tethered to polymer backbones in the electrochemical conversion of CO2 to carbon monoxide and formic acid. These tethered ionic liquids have been incorporated into novel anion ion exchange membranes for CO2 electrolysis, as well as for ionomers that have been incorporated into the cathode catalyst layer, providing a co-catalyst for the reduction reaction. In using these tethered ionic liquids in the cathode catalyst composition, the cell operating current increased by a factor of two or more. The Faradaic efficiencies also increased by 20–30%. This paper provides a review of the literature, in addition to providing some new experimental results from Dioxide Materials, in the electrochemical conversion of CO2 to CO and formic acid.

09 BIOMASS FUELS↗
DOE OSTI2020

Electrocatalysts, and fuel cells containing them

Provided are electrocatalysts, fuel cells, methods of making fuel cells, and methods of generating an electric current, each featuring a platinum (Pt)-containing substrate in contact with an aqueous solution comprising Pb2+. Electrocatalysts of the invention are formed via underpotential deposition (UPD) when a trace amount of Pb2+ is present in the electrolyte of a half anodic cell for oxidizing formic acid using Pt as the anode. Surprisingly, the UPD process dramatically enhances the activity of formic acid oxidation, at least as much as 10-fold compared with palladium (Pd) black. In an embodiment, the electrocatalyst comprises a Pt-containing substrate, a submonolayer of lead (Pb) adsorbed onto the Pt-containing substrate, and an aqueous solution comprising Pb2+, wherein the concentration of Pb2+ in the aqueous solution is 10 to 500 μm.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2025

Zero-Carbon Biofuels: An Optimized Two-Stage System for High Productivity Conversion of CO2 to Liquid Fuels

In MIT’s Zero-Carbon Biofuels work, under ARPAe’s EcoSynBio funding, we capitalized on our previously developed technology of the oleaginous yeast, Yarrowia lipolytica, engineered to produce high titer biodiesel-like lipids and alkanes, and set out to reduce or eliminate CO 2 generation during lipid production. We set out to do this by both engineering Y. lipolytica with the necessary enzymes to allow the generation of reducing equivalents from H 2 , formic acid, or methanol, and, in parallel, installing the non-oxidative glycolysis (NOG) pathway. The goal was that combination of these two would enable stoichiometric conversion of glucose and acetate to biodiesel products. Furthermore, our ARPAe Electrofuels funded research, yielded a very innovative two-stage system where gases comprising CO 2 and H 2 are used for the production of liquid fuels. Acetate is produced from CO 2 and H 2 , via acetogenic fermentation, in the first stage as the intermediary product, then fed to Y. lipolytica in the second stage, for conversion to lipids and alkanes. To increase the commercial competitiveness of the two-stage system, by improvement to the overall productivity, we recently showed that synergistic substrate co-feeding drastically enhances CO 2 fixation rates and set out to explore additional co-substrate pairs, including methanol and formic acid, in order to maximize acetate productivity. Finally, given the attractiveness as a biofuel, we also set out to attempt an important increase in the production of alkanes over lipids in Yarrowia.

10 SYNTHETIC FUELS↗