Synthetic Methanol/Fischer-Tropsch Fuel Production Capacity, Cost, and Carbon Intensity Utilizing CO2 from Industrial and Power Plants in the United States.

Captured CO2 is a potential feedstock to produce fuel/chemicals using renewable electricity as the energy source. We explored resource availability and synergies by region in the United States and conducted cost and environmental analysis to identify unique opportunities in each region to inform possible regional and national actions for carbon capture and utilization development. This study estimated production cost of synthetic methanol and Fischer-Tropsch (FT) fuels by using CO2 captured from the waste streams emitted from six industrial [ethanol, ammonia, natural gas (NG) processing, hydrogen, cement, and iron/steel production plants] and two power generation (coal and NG) processes across the United States. The results showed that a total of 1594 million metric ton per year of waste CO2 can be captured and converted into 85 and 319 billion gallons of FT fuels and methanol, respectively. FT fuels can potentially substitute for 36% of the total petroleum fuels used in the transportation sector in 2018. Technoeconomic analysis shows that the minimum selling prices for synthetic FT fuels and methanol are 1.8-2.8 times the price of petroleum fuel/chemicals, but the total CO2 reduction potential is 935-1777 MMT/year.

Life Cycle Analysis of Electrofuels: Fischer-Tropsch Fuel Production from Hydrogen and Corn Ethanol Byproduct CO2.

Electrofuels from renewable H2 and waste CO2 streams are of increasing interest because of their CO2 emissions reduction potentials compared to fossil counterparts. This study evaluated the well-to-wheel (WTW) greenhouse gas (GHG) emissions of Fischer-Tropsch (FT) fuels from various electrolytic H2 pathways and CO2 sources, using various process designs (i.e., with and without H2 recycle) and system boundaries. Two systems with different boundaries were considered: a stand-alone plant (with CO2 from any source) and an integrated plant with corn ethanol production (supplying CO2). The FT fuel synthesis process was modeled using Aspen Plus, which showed that 45% of the carbon in CO2 can be fixed in the FT fuel, with a fuel production energy efficiency of 58%. Using nuclear or solar/wind electricity, the stand-alone FT fuel production from various plant designs can reduce WTW GHG emissions by 90-108%, relative to petroleum fuels. When integrating the FT fuel production process with corn ethanol production, the WTW GHG emissions of FT fuels are 57-65% lower compared to petroleum counterparts. This study highlights the sensitivity of the carbon intensity of FT fuels to the system boundary selection (i.e., stand-alone vs integrated), which has different implications under various GHG emission credit frameworks.

A Mechanistic View of the Light-Induced Synthesis of Silver Nanoparticles Using Extracellular Polymeric Substances of Chlamydomonas reinhardtii.

In the current study, extracellular polymeric substances (EPS) of Chlamydomonas reinhardtii and photon energy biosynthetically converted Ag+ to silver nanoparticles (AgNPs). The reaction mechanism began with the non-photon-dependent adsorption of Ag+ to EPS biomolecules. An electron from the EPS biomolecules was then donated to reduce Ag+ to Ag0, while a simultaneous release of H+ acidified the reaction mixture. The acidification of the media and production rate of AgNPs increased with increasing light intensity, indicating the light-dependent nature of the AgNP synthesis process. In addition, the extent of Ag+ disappearance from the aqueous phase and the AgNP production rate were both dependent on the quantity of EPS in the reaction mixture, indicating Ag+ adsorption to EPS as an important step in AgNP production. Following the reaction, stabilization of the NPs took place as a function of EPS concentration. The shifts in the intensities and positions of the functional groups, detected by Fourier-transform infrared spectroscopy (FTIR), indicated the potential functional groups in the EPS that reduced Ag+, capped Ag0, and produced stable AgNPs. Based on these findings, a hypothetic three-step, EPS-mediated biosynthesis mechanism, which includes a light-independent adsorption of Ag+, a light-dependent reduction of Ag+ to Ag0, and an EPS concentration-dependent stabilization of Ag0 to AgNPs, has been proposed.

Individual and Combined Effects of Extracellular Polymeric Substances and Whole Cell Components of Chlamydomonas reinhardtii on Silver Nanoparticle Synthesis and Stability.

The fresh water microalga Chlamydomonas reinhardtii bioreduced Ag⁺ to silver nanoparticles (AgNPs) via three biosynthetic routes in a process that could be a more sustainable alternative to conventionally produced AgNPs. The AgNPs were synthesized in either the presence of whole cell cultures, an exopolysaccharide (EPS)-containing cell culture supernatant, or living cells that had been separated from the EPS-containing supernatant and then washed before being suspended again in fresh media. While AgNPs were produced by all three methods, the washed cultures had no supernatant-derived EPS and produced only unstable AgNPs, thus the supernatant-EPS was shown to be necessary to cap and stabilize the biogenic AgNPs. TEM images showed stable AgNPs were mostly spherical and showed a bimodal size distribution about the size ranges of 3.0 ± 1.3 nm and 19.2 ± 5.0 nm for whole cultures and 3.5 ± 0.6 nm and 17.4 ± 2.6 nm for EPS only. Moreover, selected area electron diffraction pattern of these AgNPs confirmed their polycrystalline nature. FTIR of the as-produced AgNPs identified polysaccharides, polyphenols and proteins were responsible for the observed differences in the AgNP stability, size and shape. Additionally, Raman spectroscopy indicated carboxylate and amine groups were bound to the AgNP surface.

Evaluating microwave-synthesized silver nanoparticles from silver nitrate with life cycle assessment techniques.

Silver Nanoparticles (AgNPs) are well known for applications in electronics and as antimicrobial agents because of their unique optical, electrical, cytotoxic and thermal properties. These nanoparticles can be synthesized via a wide variety of techniques; however, they require the use of hazardous solvents which have very high environmental impacts. Nanoscience researchers have attempted novel synthesis routes that reduce resource requirements and use benign chemicals, while maintaining control over their unique properties. The present study evaluates the potential environmental impacts of one such benign method using Life Cycle Assessment (LCA) techniques which are used to assess the environmental impacts of a product's life through all the stages from raw material extraction to disposal/ recycling. This research evaluates AgNPs which were synthesized using glucose as the reducing agent and food grade corn starch as the stabilizing agent in a microwave-assisted reaction system. GaBi 6.0 software was used to carry out the Life Cycle Impact Assessment on a declared unit of 1 kg of 3.0 ±â€¯1.2 nm diameter AgNPs. The results indicate that the impacts are predominantly on acidification (AP), human health particulate air (HHAP) and human toxicity non-cancer (HTNCP) potentials. These impacts are mainly from the production of silver metal and electricity used. The starch and glucose used to produce AgNPs of 3.0 ±â€¯1.2 nm is shown to have negligible environmental impacts and is therefore considered to be environmentally benign.

High conversion synthesis of <10 nm starch-stabilized silver nanoparticles using microwave technology.

A microwave reaction to convert 99 ± 1% of Ag+ to silver nanoparticles (AgNPs) of size <10 nm within 4.5 min with a specific production rate and energy input of 5.75 mg AgNP L-1 min-1 and 5.45 W mL-1 reaction volume was developed. The glucose reduced and food grade starch stabilized particles remained colloidally stable with less than a 4% change in the surface plasmon resonance band at 425-430 nm at t > 300 days. TEM determined the size of AgNPs, while TEM-EDS and XRD verified elemental composition. The conversion was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and thermal gravimetric analysis (TGA). Additionally, the required silver to starch input mass ratio, 1.0:1.3, to produce colloidally stabilized AgNPs is significantly reduced compared to previous studies. The antibacterial activity of freshly prepared AgNPs and AgNPs aged >300 days was demonstrated against E. coli as determined by agar diffusion assays. This result, corroborated by spectrophotometric and TEM measurements, indicates long-term colloidal stability of the product. Thus, this study sustainably produced antibacterial AgNPs from minimal inputs. In the broader context, the current work has quantified a sustainable platform technology to produce sphere-like inorganic nanoparticles with antimicrobial properties.

Biosynthetic Conversion of Ag⁺ to highly Stable Ag° Nanoparticles by Wild Type and Cell Wall Deficient Strains of Chlamydomonas reinhardtii.

In the current study, two different strains of the green, freshwater microalga Chlamydomonas reinhardtii bioreduced Ag⁺ to silver nanoparticles (AgNPs), which have applications in biosensors, biomaterials, and therapeutic and diagnostic tools. The bioreduction takes place in cell cultures of C. reinhardtii at ambient temperature and atmospheric pressure, thus eliminating the need for specialized equipment, harmful reducing agents or the generation of toxic byproducts. In addition to the visual changes in the cell culture, the production of AgNPs was confirmed by the characteristic surface plasmon resonance (SPR) band in the range of 415⁻425 nm using UV-Vis spectrophotometry and further evolution of the SPR peaks were studied by comparing the peak intensity at maximum absorbance over time. X-ray diffraction (XRD) determined that the NPs were Ag°. Micrographs from transmission electron microscopy (TEM) revealed that 97 ± 2% AgNPs were <10 nm in diameter. Ag⁺ to AgNP conversion was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The AgNPs were stable over time in the cell culture media, acetone, NaCl and reagent alcohol solutions. This was verified by a negligible change in the features of the SPR band after t > 300 days of storage at 4 °C.