Research Update: The nitride route to ammonia fertilizers: decoupling food and fossil fuel

A new three-year project at Kansas State University, sponsored by the U.S. Department of Energy, Basic Energy Sciences (U.S. DOE Office of Science, Award No. DE-SC0016453, "Step Catalysis to Synthesize Fossil-Free Ammonia at Atmospheric Pressure"), with $598,866 pursues ammonia for fertilizers produced from renewable resources with a new simple and rugged process. The team of Principal Investigator Dr. Peter Pfromm (Chemical Engineering), and co-Principal Investigators Dr.'s Bin Liu (Chemical Engineering) and Viktor Chikan (Chemistry) and their graduate students are investigating forming metal nitrides from metal alloy nanoparticles to activate nitrogen from air, and then synthesizing ammonia in a second step, all at atmospheric pressure and moderate temperatures. The recent precipitous decline in the cost of renewable electricity allows the needed hydrogen to be made by electrolysis of water so that the entire process is essentially fossil fuel free, economically competitive with fossil fuel based ammonia, and proceeds under conditions that will allow down-scaling and operation on stranded or intermittent renewable electricity

Activating dinitrogen for chemical looping ammonia Synthesis: Mn nitride layer growth modeling

The earth-abundant transition metal manganese (Mn) has been shown to activate dinitrogen (N2) and store nitrogen (N) as nitride for subsequent chemical reaction, for example, to produce ammonia (NH3). Chemical looping ammonia synthesis (CLAS) is a practical way to use Mn nitride by contacting nitride with gaseous hydrogen (H2) to produce ammonia (NH3). Here, the dynamic process of N atoms penetrating into solid Mn has been investigated. Nitride layer growth was modeled to quantitate and predict the storage of activated N in Mn towards designing CLAS systems. The N diffusion coefficient (DN) and reaction rate constant K for the first-order nitridation reaction were estimated at 6.2 ± 5.5 × 10-11 m2/s and 4.1 ± 3.5 × 10-4 1/s, respectively, at atmospheric pressure and 700 °C. Assuming spherical particles of Mn with a diameter of < 10 μm, about 56.8 metric tons of Mn is sufficient to produce a metric ton of NH3 per day using CLAS

Rational design of metal nitride redox materials for solar-driven ammonia synthesis

Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water, and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700-1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared to no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia

Preview of a detailed techno-economic analysis of diesel from algae: economic feasibility under sustainability constraints requires sustained unrealistically high algae yields if public subsidies are absent.

A detailed economical analysis of producing algae-derived biodiesel via open-pond aquaculture has been performed and is in peer-review for publication. The results of the economical analysis confirm the critical limitation of economic feasibility by achievable and fundamentally plausible biomass yields

Sustainability of algae derived biodiesel: A mass balance approach

A rigorous chemical engineering mass balance/unit operations approach is applied here to bio-diesel from algae mass culture. An equivalent of 50,000,000 gallons per year (0.006002 m3/s) of petroleum-based Number 2 fuel oil (US, diesel for compression–ignition engines, about 0.1% of annual US consumption) from oleaginous algae is the target. Methyl algaeate and ethyl algaeate diesel can according to this analysis conceptually be produced largely in a technologically sustainable way albeit at a lower available diesel yield. About 11 square miles of algae ponds would be needed with optimistic assumptions of 50 g biomass yield per day and m2 pond area. CO2 to foster algae growth should be supplied from a sustainable source such as a biomass-based ethanol production. Reliance on fossil-based CO2 from power plants or fertilizer production renders algae diesel non-sustainable in the long term

Economic feasibility of algal biodiesel under alternative public policies

The motivation for this research was to determine the influence of public policies on economic feasibility of producing algal biodiesel in a system that produced all its energy needs internally. To achieve this, a steady-state mass balance/unit operation system was modeled first. Open raceway technology was assumed for the production of algal feedstock, and the residual biomass after oil extraction was assumed fermented to produce ethanol for the transesterification process. The project assumed the production of 50 million gallons of biodiesel per year and using about 14% of the diesel output to supplement internal energy requirements. It sold the remainder biodiesel and ethanol as pure biofuels to maximize the rents from the renewable fuel standards quota system. Assuming a peak daily yield of 500 kg algal biomass (dry basis)/ha, the results show that production of algal biodiesel under the foregoing constraints is only economically feasible with direct and indirect public policy intervention. For example, the renewable fuel standards' tracking RIN (Renewable fuel Identification Number) system provides a treasury-neutral value for biofuel producers as does the reinstatement of the renewable fuel tax credit. Additionally, the capital costs of an integrated system are such that some form of capital cost grant from the government would support the economic feasibility of the algal biodiesel production

Chemical Looping of Manganese to Synthesize Ammonia at Atmospheric Pressure: Sodium as Promoter

Affordable synthetic ammonia (NH3) enables the production of nearly half of the food we eat and is emerging as a renewable energy carrier. Sodium-promoted chemical looping NH3 synthesis at atmospheric pressure using manganese (Mn) is here demonstrated. The looping process may be advantageous when inexpensive renewable hydrogen from electrolysis is available. Avoiding the high pressure of the Haber-Bosch process by chemical looping using earth-abundant materials may reduce capital cost, facilitate intermittent operation, and allow operation in geographic areas where infrastructure is less sophisticated. At this early stage, the data suggest that 0.28 m3 of a 50 % porosity solid Mn bed may suffice to produce 100 kg NH3 per day by chemical looping, with abundant opportunities for improvement

Enantioselective Transesterification by Candida antarctica Lipase B Immobilized on Fumed Silica

Enzymatic catalysis to produce molecules such as perfumes, flavors, and fragrances has the advantage of allowing the products to be labeled “natural” for marketing in the U.S., in addition to the exquisite selectivity and stereoselectivity of enzymes that can be an advantage over chemical catalysis. Enzymatic catalysis in organic solvents is attractive if solubility issues of reactants or products, or thermodynamic issues (water as a product in esterification) complicate or prevent aqueous enzymatic catalysis. Immobilization of the enzyme on a solid support can address the generally poor solubility of enzymes in most solvents. We have recently reported on a novel immobilization method for Candida antarctica Lipase B on fumed silica to improve the enzymatic activity in hexane. This research is extended here to study the enantioselective transesterification of (RS)-1-phenylethanol with vinyl acetate. The maximum catalytic activity for this preparation exceeded the activity (on an equal enzyme amount basis) of the commercial Novozyme 435® significantly. The steady-state conversion for (R)-1-phenylethanol was about 75% as confirmed via forward and reverse reaction. The catalytic activity steeply increases with increasing nominal surface coverage of the support until a maximum is reached at a nominal surface coverage of 230%. We hypothesize that the physical state of the enzyme molecules at a low surface coverage is dominated in this case by detrimental strong enzyme-substrate interactions. Enzyme-enzyme interactions may stabilize the active form of the enzyme as surface coverage increases while diffusion limitations reduce the apparent catalytic performance again at multi-layer coverage. The temperature-, solvent-, and long-term stability for CALB/fumed silica preparations showed that these preparations can tolerate temperatures up to 70°C, continuous exposure to solvents, and long term storage

Solar thermochemical production of ammonia from water, air and sunlight: Thermodynamic and economic analyses

Ammonia is an important input into agriculture and is used widely as base chemical for the chemical industry. It has recently been proposed as a sustainable transportation fuel and convenient one-way hydrogen carrier. Employing typical meteorological data for Palmdale, CA, solar energy is considered here as an inexpensive and renewable energy alternative in the synthesis of NH3 at ambient pressure and without natural gas. Thermodynamic process analysis shows that a molybdenum-based solar thermochemical NH3 production cycle, conducted at or below 1500 K, combined with solar thermochemical H2 production from water may operate at a net-efficiency ranging from 23 to 30% (lower heating value of NH3 relative to the total energy input). Net present value optimization indicates ecologically and economically sustainable NH3 synthesis at above about 160 tons NH3 per day, dependent primarily on heliostat costs (varied between 90 and 164 dollars/m2), NH3 yields (ranging from 13.9 mol% to stoichiometric conversion of fixed and reduced nitrogen to NH3), and the NH3 sales price. Economically feasible production at an optimum plant capacity near 900 tons NH3 per day is shown at relative conservative technical assumptions and at a reasonable NH3 sales price of about 534 ± 28 dollars per ton NH3

Bio-butanol vs. bio-ethanol: A technical and economic assessment for corn and switchgrass fermented by yeast or Clostridium acetobutylicum

Fermentation-derived butanol is a possible alternative to ethanol as a fungible biomass-based liquid transportation fuel. We compare the fermentation-based production of n-butanol vs. ethanol from corn or switchgrass through the liquid fuel yield in terms of the lower heating value (LHV). Industrial scale data on fermentation to n-butanol (ABE fermentation) or ethanol (yeast) establishes a baseline at this time, and puts recent advances in fermentation to butanol in perspective. A dynamic simulation demonstrates the technical, economic and policy implications. The energy yield of n-butanol is about half that of ethanol from corn or switchgrass using current ABE technology. This is a serious disadvantage for n-butanol since feedstock costs are a significant portion of the fuel price. Low yield increases n-butanol's life-cycle greenhouse gas emission for the same amount of LHV compared to ethanol. A given fermenter volume can produce only about one quarter of the LHV as n-butanol per unit time compared to ethanol. This increases capital costs. The sometimes touted advantage of n-butanol being more compatible with existing pipelines is, according to our techno-economic simulations insufficient to alter the conclusion because of the capital costs to connect plants via pipeline