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Thermotoga maritima is an anaerobic hyperthermophilic bacterium known for its high amounts of hydrogen (H2) production. In the current study, the kinetic modeling was applied on the engineered strains of T. maritima that surpassed the natural H2 production limit. The study generated a kinetic model explaining H2 overproduction and predicted a continuous fermentation system. A Leudking-Piret equation-based model predicted that H2 production by Tma200 (0.217 mol-H2 g−1-biomass) and Tma100 (0.147 mol-H2 g−1-biomass) were higher than wild type (0.096 mol-H2 g−1 -biomass) with reduced rates of maltose utilization. Sensitivity analysis confirmed satisfactory fitting of the experimental data. The slow growth rates of Tma200 (0.550 h−1) and Tma100 (0.495 h−1) are compared with the wild type (0.663 h−1). A higher maintenance energy along with growth and non-growth H2 coefficients corroborate the higher H2 productivity of the engineered strains. The modeled data established a continuous fermentation system for the sustainable H2 production.

Internal energy is associated with the microscopic and collective random motion of particles constituting the media. Energy of the collective random motion of particles is heat. Heat flows across the boundary of a system. Work is force times distance. Work can be totally converted into heat, but heat cannot be totally converted to work. Instead of internal energy, enthalpy is used in many fluid-flow systems. Only changes in internal energy and enthalpy can be calculated. This chapter mainly deals with the estimations of internal energy and enthalpy in various closed and open systems at steady state. Sensible and latent heats are discussed with examples. Heat of reaction is discussed and estimated by using the heat of formation. Heat of combustion with adiabatic flame temperature is discussed for estimating the heat released after burning a fuel. Measurement of heat change by using calorimeter are briefly discussed. Estimations of energy and temperature changes of air using the psychometric chart is briefly discussed. Heat transfer is also covered with some examples. The concept of exergy in fluid-flow systems is discussed briefly. There are 17 example problems in the text and 98 practice problems at the end of the chapter.

Accurate estimation of the cost is possible by using techno economic analysis in planning and operation of energy production and usage toward proper energy management and economics. Inaccurate assumptions, scale-down/scale-up problems, noncompetitive utility costs, and waste treatment may lead to failures in employing the actual trend in energy management and cost estimations with projections for upscale energy management operations. Risk analysis and sensitivity analysis help operate large energy system investments successfully. In a comprehensive feasibility analysis, techno economic analysis is being complemented with sustainability metrics to account current socioeconomics, socio-ecology, and eco-economics changes. Besides, ‘Circular Economy’ is incorporated into sustainability through the element of economics as it replaces conventional linear economy by increasing efficiency in energy management, recycling, and reducing emissions.

This chapter introduces basic definitions, properties and units, hence builds a vocabulary and infrastructure before discussing the concept of energy and its various aspects. For example, definitions of systems and properties with various units are essential to understand the change of states during energy conversions in various processes. The chapter also discusses saturated, and superheated steam tables, steady-flow, isothermal, and adiabatic processes.

Sustainability metrics, a cradle-to-gate life cycle assessment, and a technoeconomic evaluation are presented for an optimized entrained-flow coal oxy-combustion plant with carbon capture to produc...

Chemical looping combustion (CLC) has gained considerable ground in energy production due to its inherent carbon capture with a minimal energy penalty. The choice of metal oxide used as an oxygen carrier (OC) in CLC has a substantial weight on the overall efficiency of energy production as well as the ultimate cost per MW. While much work has gone into manufacturing synthetic OCs with high fuel conversions, harsh operating conditions and process limitations cause some unavoidable loss of the oxygen carrier. With low production costs and minimal conditioning required, natural ores have grown in interest as cheap alternative oxygen carriers. This work provides a substantial literature review of recent works studying the use of natural ores in CLC. Iron-based, manganese-based, copper-based and calcium based ores were found to be the main ores researched, along with mixtures of these ores and natural ores with minor additional compounds. Typical parameters have been collected for each study including; fuel conversion, stability, physical characteristics, and carbon capture efficiency. Natural ores are compared with purified metal oxides to highlight strengths and weaknesses of each ore and recommendations for future studies are made.

In this work we investigate two renewably based alternative fuels; methanol and dimethyl ether. The ultimate feedstocks for production are wind-based electrolytic hydrogen and carbon dioxide captured from an ethanol fermentation process. Dimethyl ether production was modeled in ASPEN Plus using a previously simulated methanol production facility. The facilities use 18.6 metric tons (mt) of H2 and 138.4 mt CO2 per day. Methanol is produced at a rate 96.7 mt/day (99.5 wt%) and dimethyl ether is produced at a rate of 68.5 mt/day (99.6 wt%). A full comparative life-cycle assessment (cradle-to-grave) of both fuels was conducted to investigate their feasibility and sustainability. Renewable methanol and dimethyl ether results were independently compared and this renewable process was also compared to conventional production routes. Results show that production of dimethyl ether impacts the environment more than methanol production. However the combustion of methanol fuel evens out many of the emissions metrics compared to dimethyl ether. The largest environmental impact was found to be related to the fuel production stage for both fuels. Both biofuels were shown to be comparable to biomass-based gasification fuel production routes. Methanol and dimethyl ether from CO2 hydrogenation were shown outperform conventional petroleum based fuels, reducing greenhouse gas emissions 82–86%, minimizing other criteria pollutants (SOx, NOx, etc.) and reducing fossil fuel depletion by 82–91%. The inclusion of environmental impacts in feasibility analyses is of great importance in order to improve sustainable living practices. The results found here highlight the favorable feasibility of renewably produced methanol and dimethyl ether as alternative fuels.

This study is for the technoeconomic analysis of an integral facility consisting of wind energy-based electrolytic hydrogen production, bioethanol-based carbon dioxide capture and compression, and direct methanol synthesis. ASPEN Plus was used to simulate the facility producing 97.01 mt (metric tons) methanol/day using 138.37 mt CO 2 /day and 18.56 mt H 2 /day. A discounted cash flow diagram for the integral facility is used for the economic analysis at various hydrogen production costs and methanol selling prices. The feasibility analysis is based on a multi-criteria decision matrix consisting of economic and sustainability indicators comparing renewable and non-renewable methanol productions. The overall energy efficiency for the renewable methanol is around 58%. Fixation of carbon reduces the CO 2 equivalent emission by around −1.05 CO 2 e/kg methanol. The electrolytic hydrogen production cost is the largest contributor to the economics of the integral facility. The feasibility analysis based on multi-criteria shows that renewable methanol production may be feasible.

Despite years of concerted research efforts, an industrial-scale technology has yet to emerge for production and conversion of algal biomass into biofuels and bioproducts. The objective of this review is to explore the ways of possible integration of biology, ecology and engineering for sustainable large algal cultivation and biofuel production systems. Beside the costs of nutrients, such as nitrogen and phosphorous, and fresh water, upstream technologies which are not ready for commercialization both impede economic feasibility and conflict with the ecological benefits in the sector. Focusing mainly on the engineering side of chemical conversion of algae to biodiesel has also become obstacle. However, to reduce the costs, one potential strategy has been progressing steadily to synergistically link algal aquaculture to the governmentally mandated reduction of nitrogen and phosphorous concentrations in municipal wastewater. Recent research also supports the suppositions of scalability and cost reduction. Noticeably, less is known of the economic impact of conversion of the whole algae-based biorefinery sector with additional biochemical and thermochemical processes and integration with ecological constraints. This review finds that a biorefinery approach with integrated biology, ecology, and engineering could lead to a feasible algal-based technology for variety of biofuels and bioproducts.

When carbohydrates are fermented by the hyperthermophilic anaerobe Thermotoga maritima, molecular hydrogen (H2) is formed in strict proportion to substrate availability. Excretion of the organic acids acetate and lactate provide an additional sink for removal of excess reductant. However, mechanisms controlling energy management of these metabolic pathways are largely unexplored. To investigate this topic, transient gene inactivation was used to block lactate production as a strategy to produce spontaneous mutant cell lines that overproduced H2 through mutation of unpredicted genetic targets. Single-crossover homologous chromosomal recombination was used to disrupt lactate dehydrogenase (encoded by ldh) with a truncated ldh fused to a kanamycin resistance cassette expressed from a native P groESL promoter. Passage of the unstable recombinant resulted in loss of the genetic marker and recovery of evolved cell lines, including strain Tma200. Relative to the wild type, and considering the mass balance of fermentation substrate and products, Tma200 grew more slowly, produced H2 at levels above the physiologic limit, and simultaneously consumed less maltose while oxidizing it more efficiently. Whole-genome resequencing indicated that the ABC maltose transporter subunit, encoded by malK3, had undergone repeated mutation, and high-temperature anaerobic [14C]maltose transport assays demonstrated that the rate of maltose transport was reduced. Transfer of the malK3 mutation into a clean genetic background also conferred increased H2 production, confirming that the mutant allele was sufficient for increased H2 synthesis. These data indicate that a reduced rate of maltose uptake was accompanied by an increase in H2 production, changing fermentation efficiency and shifting energy management.IMPORTANCE Biorenewable energy sources are of growing interest to mitigate climate change, but like other commodities with nominal value, require innovation to maximize yields. Energetic considerations constrain production of many biofuels, such as molecular hydrogen (H2) because of the competing needs for cell mass synthesis and metabolite formation. Here we describe cell lines of the extremophile Thermotoga maritima that exceed the physiologic limits for H2 formation arising from genetic changes in fermentative metabolism. These cell lines were produced using a novel method called transient gene inactivation combined with adaptive laboratory evolution. Genome resequencing revealed unexpected changes in a maltose transport protein. Reduced rates of sugar uptake were accompanied by lower rates of growth and enhanced productivity of H2.

Algae are often promoted as feedstock organisms to produce a sustainable petroleum fossil fuel alternative. However, to induce lipid accumulation most often requires a severe stress that is difficult to induce in large batch cultures. The objective of this study is to analyze and mathematically model heat stress on growth, chlorophyll content, triacylglyceride, and starch synthesis in algae. We initially screened 30 algal species for the most pronounced induction of lipid droplets from heat stress using confocal microscopy and mass spectroscopy techniques. One species, Coccomyxa subellipsoidea C169, was selected and subjected to further biochemical analyses using a jacketed bioreactor amended with 1% CO2 at 25°C, 30°C, 32°C, 33°C, 34°C, 35°C, and 36°C. Lipid and starch accumulation was less extreme than N stress. Growth was reduced above 25°C, but heat stress induced lipid droplet synthesis was negatively correlated with growth only past a demonstrated threshold temperature above 32°C. The optimal temperature for lipid accumulation was 35°C, which led to 6% of dry weight triglyceride content and a 72% reduction from optimal growth after 5 days. Fatty acid influx rates into triglycerides and 15N labeling of amino acids and proteins indicate that heat stress is mechanistically distinct from N stress. Thus, this study lends support to a novel hypothesis that lipid droplet triglycerides result from a redistribution of carbon flux as fatty acids to neutral storage lipids over membrane or other lipids.

This study presents energy conservation as an important part of controlling energy efficiency and climate change. It discusses energy conserving measures in power production, in compressor work, in furnaces and boilers, in heating and cooling of houses, as well as in lighting and driving. Two industrial case studies based on thermodynamic analysis (TA) are presented; one is on process heat integration in a crude oil refinery to conserve energy, while the second is on the exergy analysis of the back-end separation of an ethylene plant. The analyses and the case studies show that there is considerable potential in energy conservation in the industrial sector, transportation sector, as well as in the home heating and cooling sector.

Estimation of thermal properties, diffusion properties, or chemical-reaction rates from transient data requires that a model is available that is physically meaningful and suitably precise. The model must also produce numerical values rapidly enough to accommodate iterative regression, inverse methods, or other estimation procedures during which the model is evaluated again and again. Applications that motivate the present work include process control of microreactors, measurement of diffusion properties in microfuel cells, and measurement of reaction kinetics in biological systems. This study introduces a solution method for nonisothermal reaction-diffusion (RD) problems that provides numerical results at high precision and low computation time, especially for calculations of a repetitive nature. Here, the coupled heat and mass balance equations are solved by treating the coupling terms as source terms, so that the solution for concentration and temperature may be cast as integral equations using Green’s functions (GF). This new method requires far fewer discretization elements in space and time than fully numeric methods at comparable accuracy. The method is validated by comparison with a benchmark heat transfer solution and a commercial code. Results are presented for a first-order chemical reaction that represents synthesis of vinyl chloride. Copyright This work was supported by the University of Nebraska Foundation through the Global Faculty Associates program.

This chapter highlights some recent developments in the biofuel production processes using various types of biomass feedstock. Biomass resources are mainly divided into four types: first, second, and third generations; and wastes. All these types of biomass can be converted to alcohols, biogas, biooil, biodiesel, food/feed, and bioproducts by using biochemical, thermochemical, and hydrothermal processes. The main conversion processes, including fermentation, transesterification, gasification, and Fischer–Tropsch (F–T) synthesis, along with economics and safety of biofuel production are analyzed and discussed. Because of the diversity of biomass and conversion processes, the biofuel supply chain is associated with economic, environmental, and societal effects and hence can promote sustainable development.

Summary This study presents the assessment of energy and environmental sustainability metrics for a crude oil refinery consisting of three distillation columns. The assessments of the current operation and the retrofits for possible improvements are suggested by the thermodynamic analysis and energy analyzer. The main objective is to explore the scope of reducing the thermal energy consumption and CO2 emissions for a more sustainable refinery operation. Thermodynamic analysis is carried out by using the thermal analysis capability of ‘column targeting tool’ to address the ‘energy intensity metrics’ and the ‘energy analyzer’ to design and improve the performance of the heat exchanger network system for process heat integration. Environmental pollution impact metrics are estimated from the ‘carbon tracking’ options with a selected CO2 emission data source of US-EPA-Rule-E9-5711 and using crude oil as a primary fuel source for the hot utilities. The results indicate that column targeting tool, energy analyzer, and carbon tracking can estimate the energy and environmental sustainability metrics of an existing design and determine the scope of considerable improvements for reducing the costs of thermal energy required and emissions of carbon dioxide in a crude oil refinery operation. Copyright © 2015 John Wiley & Sons, Ltd.

Taurine (2-aminoethanesulfonic acid) is an amino acid-like compound widely distributed in animals and an essential nutrient in some species. Targeted metabolomics of marine and fresh water microalgae combined with medium supplementation identified biosynthetic pathway intermediates and necessary catalytic activities. Genomic analysis was then used to predict the first taurine biosynthetic pathway in these organisms. MRM-based electrospray ionization (ESI) LC–MS/MS analysis demonstrated that taurine is synthesized using a carbon backbone from l -serine combined with sulfur derived from sulfate. Metabolite analysis showed a non-uniform pattern in levels of pathway intermediates that were both species and supplement-dependent. While increased culture salinity raised taurine levels modestly in marine alga, taurine levels were strongly induced in a fresh water species implicating taurine as an organic osmolyte. Conservation of the synthetic pathway in algae and metazoans together with a pattern of intermittent distribution in other lineages suggests that it arose early in eukaryotic evolution. Elevated levels of cell-associated taurine in algae could offer a new and biorenewable source of this unusual bioactive compound.