Pyruvate-derived dialkoxyalkanoates (DAOAs) were synthesized in good yield using a mild protocol. Combustion performance and physical properties of DAOAs compare favorably to other low-carbon diesel fuels.

Hyperboosting is a recently discovered phenomenon in which the research octane number (RON) of a blend is higher than both the neat blendstock and the neat fuel it was blended into. RON is a measure of a fuel's resistance to knock, and knock is a cause of engine inefficiency. Blends which exhibit hyperboosting are blends in which an overall improvement in engine efficiency may be expected. The first discovery of hyperboosting came from blending experiments in which prenol was blended into several different base fuels. Here, ignition delay time (IDT) measurements taken using a commercially available constant volume combustion chamber called the Advanced Fuel Ignition Delay Analyzer (AFIDA) are presented. The data show that some prenol blends have longer IDTs (lower reactivity) than either neat prenol or the base fuel, providing further evidence of hyperboosting. Additionally, more blending data is presented in which the base fuel is varied, which allows for a better understanding of hyperboosting sensitivity to chemical classes. The data indicate that aromatics may inhibit, and branched alkanes may enhance the magnitude of hyperboosting observed. Enthalpy of vaporization estimates are also given for several molecules which are blended into a 4-component surrogate. These estimates are derived from Equation of State simulations and reveal that there is no observable correlation between hyperboosting and enthalpy of vaporization. Blending data for molecules which share structural similarities with prenol are also presented. Structure property relationships are suggested, in which the double bond motif of prenol seems to play an important role in hyperboosting. This may help to understand hyperboosting and its underlying mechanism. Lastly, blending curves of surrogate blends with prenol experienced hyperboosting under lean (Homogeneous Charged Compression Ignition-HCCI) operating conditions, which validates that hyperboosting is not an artifact of the octane test methods, but inherent to the properties of prenol.

Combustion of liquid fossil fuels for transportation is a major source of carbon emissions only partially offset by the incumbent renewable alternatives-biodiesel, renewable diesel, and ethanol. New renewable ground transportation fuels derived from abundant sources of biomass, and utilizing carbon-efficient bioprocessing, are needed to further offset fossil fuel use. Low carbon intensity liquid fuels are especially required for medium- to heavy-duty engine architectures supporting the long-range transportation fleet. Realization of substantial carbon efficiency gains in renewable fuel production can be achieved by extending feedstocks beyond lipids, which are the primary bioderived source material for biodiesel and renewable diesel. Toward these ends, chemical upgrading of the high carbon yield, central metabolism-derived intermediates, glycolic acid, lactic acid, and 4-hydroxybutyrate with various fermentation-derived alcohols was accomplished using standard chemical transformations to provide a class of compounds that show promise as an alternative to petroleum diesel. Fuel property testing of these C-7-C-22 hydroxyalkanoate-derived compounds demonstrated improved cold temperature performance compared to biodiesel (cloud point temperatures < -SO degrees C) and improved derived cetane number (DCN) and sooting metrics compared to renewable diesel, providing the technical basis for a new high-performance renewable blendstock for decarbonization of heavy-duty transport.

Background Advanced spark ignition engines require high performance fuels with improved resistance to autoignition. Biologically derived olefinic alcohols have arisen as promising blendstock candidates due to favorable octane numbers and synergistic blending characteristics. However, production and downstream separation of these alcohols are limited by their intrinsic toxicity and high aqueous solubility, respectively. Bioproduction of carboxylate esters of alcohols can improve partitioning and reduce toxicity, but in practice has been limited to saturated esters with characteristically low octane sensitivity. If olefinic esters retain the synergistic blending characteristics of their alcohol counterparts, they could improve the bioblendstock combustion performance while also retaining the production advantages of the ester moiety. Results Optimization of Escherichia coli isoprenoid pathways has led to high titers of isoprenol and prenol, which are not only excellent standalone biofuel and blend candidates, but also novel targets for esterification. Here, a selection of olefinic esters enhanced blendstock performance according to their degree of unsaturation and branching. E. coli strains harboring optimized mevalonate pathways, thioester pathways, and heterologous alcohol acyltransferases (ATF1, ATF2, and SAAT) were engineered for the bioproduction of four novel olefinic esters. Although prenyl and isoprenyl lactate titers were limited to 1.48 ± 0.41 mg/L and 5.57 ± 1.36 mg/L, strains engineered for prenyl and isoprenyl acetate attained titers of 176.3 ± 16.0 mg/L and 3.08 ± 0.27 g/L, respectively. Furthermore, prenyl acetate (20% bRON = 125.8) and isoprenyl acetate (20% bRON = 108.4) exhibited blend properties comparable to ethanol and significantly better than any saturated ester. By further scaling cultures to a 2-L bioreactor under fed-batch conditions, 15.0 ± 0.9 g/L isoprenyl acetate was achieved on minimal medium. Metabolic engineering of acetate pathway flux further improved titer to attain an unprecedented 28.0 ± 1.0 g/L isoprenyl acetate, accounting for 75.7% theoretical yield from glucose. Conclusion Our study demonstrated novel bioproduction of four isoprenoid oxygenates for fuel blending. Our optimized E. coli production strain generated an unprecedented titer of isoprenyl acetate and when paired with its favorable blend properties, may enable rapid scale-up of olefinic alcohol esters for use as a fuel blend additive or as a precursor for longer-chain biofuels and biochemicals.

Decarbonizing the transportation sector is likely to require both electrification and increased incorporation of biofuels and/or bioblendstocks. While the social and environmental benefits of bioblendstocks are well understood, their real value for the fuel producers has not been established. This work considers prenol as a bioblendstock case study to identify sources of intrinsic value to fuel blenders by studying the properties of binary mixtures with gasoline components. The considered refinery blendstocks were samples of full range naphthas from the distillation, fluidized catalytic cracking, isomerization, alkylation, and reforming units. Octane numbers, Reid vapor pressure, distillation curves, and sulfur content were evaluated. Our results indicate the need for adjusting the formulation of the base fuel, depending on the interplay among the properties of the bioblendstock and those of the base fuel. Prenol increased research octane number (RON) and octane sensitivity (OS) of the base fuel, by up to 25 and 10 octane numbers, respectively. Additionally, 10 vol% prenol reduced RVP up to 2.2 psi, for the more volatile blendstock. Thus, considering prenol as a low volatility, RON/OS boosting bioblendstock, the composition of the preferred base fuel was proposed as containing reduced olefins and aromatics, and increase light fractions. The potential impact of this new gasoline formulation on refining processes and products gives rise to direct sources of value to the refiners, such as exporting products to the chemicals market, increasing the value of intermediate refinery streams, decreasing operating severity of certain refinery units, and broadening of the product suite.

The Salton Sea in the Imperial Valley of California is a threatened ecosystem. To address the challenges related to trace element accumulation and eutrophication, a 270 m long attached periphytic algae flow-way was deployed at the Alamo River Wetlands, a tributary of the Salton Sea. To assess opportunities for efficient generation of biomass from reclamation of run-off-derived nutrients, the quantities of available and biosorpbed nutrients, organics, and trace elements were monitored. Over the course of 2 years, persistent algal biomass production was achieved at an average ash-free biomass productivity of 5.8 +/- 2.7 g/m(2)/day for the full flow-way length. Overall, harvested biomass consisted of high ash (76.3 +/- 5.4%) and low lipid (1.1 +/- 1.0%) content, which are typical of periphytic algal biomass. Nitrogen removal rates of 530 +/- 190 mg N/m(2)/day, phosphorous removal rates of 14 +/- 6 mg P/m(2)/day, and 73 +/- 25% of BOD (Biological Oxygen Demand) removal rates were achieved. Furthermore, spatial variations of the biomass productivity along with nutrient removal rates were observed to have a decreasing trend over the length of the flow-way, while N and P contents of the biomass showed increasing trend, indicating variable nutrient utilization efficiency as an important factor for system scaling. Temperature and solar irradiation were found to be key environmental factors for biomass productivity and nutrient removal rates. However, stable uptake of nutrients, organics, and metals in the biomass, despite intermittent variation of the analyte concentrations in the source water, indicate the resilience of attached periphytic algae biomass production at dilute nutrient concentration regimes. Trace metal analysis of the water from the surrounding area revealed levels exceeding federal toxicity guidelines for Selenium and Copper. Significant bioaccumulation of these and other metals contaminants were also identified in the harvested biomass, including Nickel, Chromium, Cadmium and Lead. Together these findings demonstrate several potential value propositions for attached algae cultivation from agricultural runoff-impacted surface waters, including remediation of N/P nutrients, organics, and common toxic metals, concomitant with biomass production.

High-protein algae bioproduct system boundaries for environmental sustainability risk analysis.

Fusel alcohol mixtures containing ethanol, isobutanol, isopentanol, and 2-phenylethanol have been shown to be a promising means to maximize renewable fuel yield from various biomass feedstocks and waste streams. We hypothesized that use of these fusel alcohol mixtures as a blending agent with gasoline can significantly lower the greenhouse gas emissions from the light-duty fleet. Since the composition of fusel alcohol mixtures derived from fermentation is dependent on a variety of factors such as biocatalyst selection and feedstock composition, multi-objective optimization was performed to identify optimal fusel alcohol blends in gasoline that simultaneously maximize thermodynamic efficiency gain and energy density. Pareto front analysis combined with fuel property predictions and a Merit Score-based metric led to prediction of optimal fusel alcohol-gasoline blends over a range of blending volumes. The optimal fusel blends were analyzed based on a Net Fuel Economy Improvement Potential metric for volumetric blending in a gasoline base fuel. The results demonstrate that various fusel alcohol blends provide the ability to maximize efficiency improvement while minimizing increases to blending vapor pressure and decreases to energy density compared to an ethanol-only bioblendstock. Fusel blends exhibit predicted Net Fuel Economy Improvement Potential comparable to neat ethanol when blended with gasoline in all scenarios, with increased improvement over ethanol at moderate to high bio-blendstock blending levels. The optimal fusel blend that was identified was a mixture of 90% v/v isobutanol and 10% v/v 2-phenylethanol, blended at 45% v/v with gasoline, yielding a predicted 4.67% increase in Net Fuel Economy Improvement Potential. These findings suggest that incorporation of fusel alcohols as a gasoline bioblendstock can improve both fuel performance and the net fuel yield of the bioethanol industry.

Reducing the impacts of medium- and heavy-duty (MD/HD) ground transportation can be enabled by fuel-engine combinations that use lower compression ignition liquid fuels and reduce criteria pollutant emissions. Fuels and blendstocks combined with advanced engine technologies could reduce the cost of ownership and the emission of pollutants, including soot, nitrogen oxides (NOx) and greenhouse gases (GHGs), from MD/HD vehicles. This report describes the evaluation and screening of MD/HD mixing-controlled compression ignition (MCCI) biofuel candidates for further development and commercialization. The report is aimed at 1) biofuel researchers looking to better understand options to reduce criteria pollutant and GHG emissions while maintaining efficiency and meeting requirements for engine operability and 2) engine researchers who want to evaluate biofuels that meet diesel fuel properties for their impact on conventional and advanced diesel combustion strategies.

The purpose of this study is to determine the potential for an attached algae flow-way system to efficiently produce algal biomass in estuarine surface waters by utilizing dilute non-point source nutrients from local urban, industrial, and agricultural discharges into the Upper Laguna Madre, Corpus Christi, Texas. The study was conducted over the course of two years to establish seasonal base-line biomass productivity and composition for bioproducts applications, and to identify key environmental factors and flow-way cohorts impacting biomass production. For the entire cultivation period, continuous ash free biomass production at 4 to 10 g/m(2)/day (corresponding to nutrient recovery at 300 to 500 mg of nitrogen/m(2)/day and 15 to 30 mg of phosphorus/m(2)/day) was successfully achieved without system restart. Upon start-up, a latency period was observed which indicates roles for species succession from relatively low productivity, high ash content pioneer periphytic culture composed primarily of benthic diatoms from the source waters to higher productivity, reduced ash content, and more resilient culture mainly composed of filamentous chlorophyta, Ulva lactuca. Principal Component Analysis (PCA) was used to identify environmental factors driving biomass production, and machine learning (ML) models were constructed to assess the predictive capability of the data set for system performance using the local multi-season environmental variations. Environmental datasets were segregated for ML training, validation, and testing using three methods: regression tree, ensemble regression, and Gaussian process regression (GPR). The predicted ash-free biomass productivity using ML models resulted in root-squared-mean errors (RSME) from 1.78 to 1.86 g/m(2)/day, and R 2 values from 0.67 to 0.75 using different methods. The greatest contributor to net productivity was total solar irradiation, followed by air temperature, salinity, and pH. The results of the study should be useful as a decision-making tool to application of attached algae flow-ways for biomass production while preventing algal blooms in the environment. (C) 2021 Published by Elsevier Ltd.

Harmful algal blooms (HABs) affect fresh and saltwater bodies around the world, causing a variety of damages to the surrounding communities. The primary driver of HABs is nutrient pollution. One novel HAB mitigation solution is to employ large-scale attached algal growth systems that consume nutrients from the water and prevent downstream nutrient accumulation and large scale HAB events. The feasibility of technology deployment is dependent on the economic viability. A model was created to estimate HAB-related economic damages, with or without non-point source nutrient reduction solutions, using Lake Erie as a case study. In the model, HAB severity is predicted based on nutrient loads and is tied to economic indicators to estimate the HAB-related economic losses. Results show that on average, Lake Erie communities lose $142 M (+/- $29 M) year-1 from HABs without mitigation technology. Use of attached algal systems show an average net savings ranging between $29-42 M year-1 from HAB mitigation depending on the system configuration. Attached algal systems show greater positive cash flows when compared to farm-based best management practices, thus warranting additional testing and consideration as a potential HAB mitigation strategy. Additional considerations included stochastic uncertainty and increasing dissolved reactive phosphorus concentrations, which increased the effectiveness of attached algal systems. (c) 2021 The Authors. Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

the above eight land use categories. It is envisaged that a Year 2 CCBNEP project will model the loadings of these pollutants based on variable conditions (e.g., wet/dry year, large/small storm) for watersheds and subwatersheds within the study area. The report includes a comprehensive geographic analysis of the contribution of NPS pollutants to the CCBNEP study area and an analysis of probable causes.

We demonstrated production of a superior performance biodiesel referred to here as fatty acid fusel alcohol esters (FAFE) - by reacting fusel alcohols (isobutanol, 3-methyl-1-butanol, and (S)-(-)-2-methyl-1-butanol) with oil (glyceryl trioleate) using lipase from Aspergillus oryzae. Reaction conditions corresponding to a molar ratio of 5:1 (fusel alcohols to oil), enzyme loading of 2% w/w, reaction temperature of 35 degrees C, shaking speed of 250 rpm, and reaction time of 24 h achieved > 97% conversion to FAFE. Further, FAFE obtained from reacting a fusel alcohol mixture with corn oil were evaluated for use as a fuel for diesel engines. FAFE mixtures showed superior combustion and cold-flow properties, with the derived cetane numbers up to 4.8 points higher, cloud points up to -6 degrees C lower, and the heat of combustion up to 2.1% higher than the corresponding FAME samples, depending on the fusel mixture used. This represents a significant improvement for all three metrics, which are typically anti-correlated. FAFE provides a new opportunity for expanded usage of biodiesel by addressing feedstock limitations, fuel performance, and low temperature tolerance.

In the last 20 years, biodiesel consumption in the United States has rapidly increased to similar to 2 billion gallons per year as a renewable supplement to fossil fuel. However, further expansion of biodiesel use is currently limited in part by poor cold weather performance, which prevents year-round blending and necessitates blend walls <= 5% v/v. In order to provide a diesel fuel blendstock with improved cold weather performance (cloud point, pour point, and cold filter plug point), while at the same time maintaining other required fuel performance specifications, several biodiesel redox analogues were synthesized and tested. The best performing candidate fuels from this class showed improvement in the derived cetane number (29.3% shorter ignition delay), lower heating value (+4.7 MJ/kg), relative sooting tendency (-7.4 YSI/MJ), and cloud point (15 degrees C lower) when compared to a B100 biodiesel composed of an identical fatty acid profile. It was observed as a general trend that the reduced form of biodiesel, fatty alkyl ethers (FAEs), shows performance improvements in all fuel property metrics. The suite of improved properties provided by FAEs gives biodiesel producers the opportunity to diversify their portfolio of products derived from lipid and alcohol feedstocks to include long-chain alkyl ethers, a biodiesel alternative with particular applicability for winter weather conditions across the US.