Carbon intensity of global crude oil trading and market policy implications

The energy mix transition has accelerated the need for more accurate emissions reporting throughout the petroleum supply chain. Despite increasing environmental regulations and pressure for emissions disclosure, the low resolution of existing carbon footprint assessment does not account for the complexity of crude oil trading. The lack of source crude traceability has led to poor visibility into the "well-to-refinery-entrance" carbon intensities at the level of granular pathways between producers and destination markets. Using high-fidelity datasets, optimization algorithms to facilitate supply chain traceability and bottom-up, physics-based emission estimators, we show that the variability in global "well-to-refinery-entrance" carbon intensities at the level of crude trade pathways is significant: 4.2-214.1 kg-CO2-equivalent/barrel with a volume-weighted average of 50.5 kg-CO2-equivalent/barrel. Coupled with oil supply forecasts under 1.5 °C scenarios up to 2050, this variability translates to additional CO2-equivalent savings of 1.5-6.1 Gigatons that could be realized solely by prioritizing low-carbon supply chain pathways without other capital-intensive mitigation measures.

Understanding variability in petroleum jet fuel life cycle greenhouse gas emissions to inform aviation decarbonization

A pressing challenge facing the aviation industry is to aggressively reduce greenhouse gas emissions in the face of increasing demand for aviation fuels. Climate goals such as carbon-neutral growth from 2020 onwards require continuous improvements in technology, operations, infrastructure, and most importantly, reductions in aviation fuel life cycle emissions. The Carbon Offsetting Scheme for International Aviation of the International Civil Aviation Organization provides a global market-based measure to group all possible emissions reduction measures into a joint program. Using a bottom-up, engineering-based modeling approach, this study provides the first estimates of life cycle greenhouse gas emissions from petroleum jet fuel on regional and global scales. Here we show that not all petroleum jet fuels are the same as the country-level life cycle emissions of petroleum jet fuels range from 81.1 to 94.8 gCO₂e MJ^-1, with a global volume-weighted average of 88.7 gCO₂e MJ^-1. These findings provide a high-resolution baseline against which sustainable aviation fuel and other emissions reduction opportunities can be prioritized to achieve greater emissions reductions faster.

Life Cycle GHG Perspective on U.S. Natural Gas Delivery Pathways

Recent emission measurement campaigns have improved our understanding of the total greenhouse gas (GHG) emissions across the natural gas supply chain, the individual components that contribute to these emissions, and how these emissions vary geographically. However, our current understanding of natural gas supply chain emissions does not account for the linkages between specific production basins and consumers. This work provides a detailed life cycle perspective on how GHG emissions vary according to where natural gas is produced and where it is delivered. This is accomplished by disaggregating transmission and distribution infrastructure into six regions, balancing natural gas supply and demand locations to infer the likely pathways between production and delivery, and incorporating new data on distribution meters. The average transmission distance for U.S. natural gas is 815 km but ranges from 45 to 3000 km across estimated production-to-delivery pairings. In terms of 100-year global warming potentials, the delivery of one megajoule (MJ) of natural gas to the Pacific region has the highest mean life cycle GHG emissions (13.0 g CO₂e/MJ) and the delivery of natural gas to the Northeast U.S. has the lowest mean life cycle GHG emissions (8.1 g CO₂e/MJ). The cradle-to-delivery scenarios developed in this work show that a national average does not adequately represent the upstream GHG emission intensity for natural gas from a specific basin or delivered to a specific consumer.

Comparative Life Cycle Evaluation of the Global Warming Potential (GWP) Impacts of Renewable Natural Gas Production Pathways

Renewable natural gas (RNG) sources are being considered in future energy strategy discussions as potential replacements for fossil natural gas (FNG). While today's supply of RNG resources is insufficient to meet U.S. demands, there is significant interest in its viability to supplement and decarbonize the natural gas supply. However, the studies compare the life cycle global warming potential (GWP) of various RNG production pathways are lacking and focus mostly on a singular pathway. This effort is an attempt to close this gap and provide a comparison between the life cycle GWP of three major RNG pathways and the FNG pathway. The three RNG pathways evaluated are anaerobic digestion (AD), thermal gasification (TG), and power-to-gas (P2G) using various feedstocks. The functional unit is 1 MJ of compressed RNG ready for injection into the natural gas transmission network. The results show that RNG production is not always carbon neutral or negative. Depending on the pathway, the GWP impact of RNG production can range from -229 to 27 g CO₂e/MJ compressed RNG, with AD of animal manure and AD of municipal solid waste being the least and the most impactful pathways, respectively, compared to the 10.1 g CO₂e/MJ impact for compressed FNG.

Evaluating the climate benefits of CO2-enhanced oil recovery using life cycle analysis

This study uses life cycle analysis (LCA) to evaluate the greenhouse gas (GHG) performance of carbon dioxide (CO2) enhanced oil recovery (EOR) systems. A detailed gate-to-gate LCA model of EOR was developed and incorporated into a cradle-to-grave boundary with a functional unit of 1 MJ of combusted gasoline. The cradle-to-grave model includes two sources of CO2: natural domes and anthropogenic (fossil power equipped with carbon capture). A critical parameter is the crude recovery ratio, which describes how much crude is recovered for a fixed amount of purchased CO2. When CO2 is sourced from a natural dome, increasing the crude recovery ratio decreases emissions, the opposite is true for anthropogenic CO2. When the CO2 is sourced from a power plant, the electricity coproduct is assumed to displace existing power. With anthropogenic CO2, increasing the crude recovery ratio reduces the amount of CO2 required, thereby reducing the amount of power displaced and the corresponding credit. Only the anthropogenic EOR cases result in emissions lower than conventionally produced crude. This is not specific to EOR, rather the fact that carbon-intensive electricity is being displaced with captured electricity, and the fuel produced from that system receives a credit for this displacement.

Puccinia acroptili on Russian Knapweed in Colorado, Montana, and Wyoming

Acroptilon repens (L.) DC. (Russian knapweed) is a long-lived perennial weed from central Asia that is widely distributed in the western United States (U.S.). Recently, accessions of a rust disease were collected from Colorado (CO), Montana (MT), and Wyoming (WY) for comparison with Eurasian isolates. U.S. accessions had two-celled teliospores with slight constrictions in the middle and urediniospores with three germ pores ± equatorial in location. Urediniospores were (state, width × length, [n = 100]): CO, 16.4 to 25.7 × 19.2 to 27.0 μm; MT, 18.4 to 23.1 × 17.4 to 24.6 μm; and WY, 18.0 to 26.2 × 20.2 to 26.7 μm. These were similar to those of 16.6 to 25.7 × 21.2 to 28.0 μm from two New Mexican (NM) herbarium specimens (BPI Nos. 1107952 and 1110177) (1). Teliospores measured 19.9 to 27.7 × 29.8 to 47.4 μm, 17.4 to 26.0 × 32.4 to 44.2 μm, 16.5 to 27.5 × 29.4 to 45.7 μm, and 18.7 to 27.6 × 31.0 to 46.4 μm for CO, MT, WY, and NM accessions, respectively. These rust isolates have been identified as Puccinia acroptili Syd. on the basis of host plant record and spore morphology (2). To our knowledge, this is the first record of P. acroptili in CO, MT, and WY. Besides NM, P. acroptili has been reported in North America from California, British Columbia, and Saskatchewan. References: (1) M. E. Palm and S. G. Vesper. Plant Dis. 75:1075, 1991. (2) D. B. O. Savile. Can. J. Bot. 48:1567, 1970.

First Report of Leaf Spot Caused by a Cercosporella sp. on Acroptilon repens in the United States

In August 2005, leaf spots were observed on a sample of Acroptilon repens (L.) DC. (Russian knapweed [RK]) collected at the Charles M. Russell National Wildlife Refuge in Montana. Symptoms included circular to subcircular brown spots, 1 to 18 mm in diameter, with indefinite margins that sometimes had a thin, purple-to-rose border. Leaves placed in moist chambers developed conidiophores and conidia within 48 h. Stroma were subcuticular, pale yellowish; conidiophores were hyaline, zero to two septate, thin walled, smooth, unbranched, 31 to 91 × 2.8 to 5.6 μm; and conidia were solitary or in secondary short chains, ovoid to subclavate, 13 to 52 × 3.2 to 6.8 μm, zero to three septate, hyaline, and thin walled. Conidial scars and hyla were umbronate, somewhat thickened, refractive, and not darkened. In three tests, 50 RK plants spray inoculated with 10⁶ conidia/ml developed symptoms similar to those on the sample and the fungus was reisolated each time. Fungal identification, Cercosporella acroptili (Bremer) U. Braun, was based on morphology (1) and comparisons with the type specimen and a Turkish isolate (FDWSRU 98-001). ITS 1 and 2 sequences (GenBank Accession No. 779164) also were identical to a known isolate of C. acroptili. A specimen (BPI No. 871029) has been submitted to the USDA-ARS-SBML. RK is a major weed pest in the western United States and has been target of biological control research in recent years. Reference: (1) U. Braun. A Monograph of Cercosporella, Ramularia, and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 1. IHW-Verlage, Eching-by-Munich, 1995.

Water content and water structure in CT and MR signal changes: possible influence in detection of early stroke

Recent work by the authors and others has shown that MR imaging is more sensitive than CT in the detection of acute stroke. To separate the effects of water content and water structure on MR signal intensity, we undertook two sets of experiments that used simple model systems: gelatin gels with increasing water content and hardened hens' eggs. CT and MR were performed on both systems. On CT there was a direct linear relationship between CT attenuation (Hounsfield units) and the specific gravity of the gelatin gels, and an inverse relationship with water content. There was only a minimal change in the specific gravity of egg samples with hardening and, as expected on CT, no change in linear attenuation accompanying hardening. On MR there was a linear relationship between water content in gelatin gels and spin-lattice (T1) relaxation time (r = .92, p less than .01) and spin-spin (T2) relaxation time (r = .91, p less than .05). However, these changes were insufficient to explain the changes of signal intensity that occur in the brain with infarction. The simple cellular system with hens' eggs demonstrated that shortening of T1 and T2 accompanied egg hardening with minimal change in water content; the shift of water from bulk water to a bound or structured form was probably the basis of this phenomenon. We found that water structure and not merely water content is a significant mechanism underlying relaxation time changes and signal intensity changes in acute stroke.

A clinical laboratory program to improve performance of resident physicians

In summary residents entering our program lacked many basic clinical laboratory skills. Without an organized curriculum in this area, residents make marginal or no gains in competence. A clinical laboratory program which is accessible and clinically relevant does influence residents' knowledge and skills. Whether supervised performance of tests or didactic teaching was responsible for improved test results in our residents remains to be determined. This is important to determine because of the financial restraints of most programs and the demands already present on most residents' time.

The mode of action alginic acid compound in the reduction of gastroesophageal reflux

This study was designed to evaluate quantitatively the mode of action of alginic acid compound (AAC) in the treatment of patients with symptomatic gastroesophageal reflux. Gastroesophageal scintigraphy using an orall administered Tc-99m sulfur colloid solution was used to demonstrate that AAC decreased significantly the gastroesophageal reflux index from (9.9 +/- 1.3) % to (6.5 +/- 0.8) % (p less than 0.05). No alteration of lower esophageal sphincter pressure was observed. After ACC was suitably labeled with Sr-87m, a dual-nuclide scintigraphic technique was used to show that most (greater than 75%) of the AAC was located in the upper half of the stomach in both normal subjects and patients with gastroesophageal reflux. In those subjects in whom reflux did occur after treatment with AAC, the Sr-87m-AAC refluxed into the esophagus preferentially compared with the liquid containing Tc-99m sulfur colloid. These findings suggest that AAC dimishes gastroesophageal reflux by means of its foaming, floating, and viscous properties.

Computer-assisted analysis of chromosomal abnormalities: detection of a deletion in aniridia-Wilms' tumor syndrome

A chromosome translocation, t(8p + ; 11q -), in a patient with aniridia and Wilms' tumor, appeared balanced by standard techniques, including trypsin banding. Computer analysis of optical microscope scanning profiles of chromosome pairs 8 and 11 revealed an interstitial deletion of the short arm of 8. Computer analysis coupled to the new banding techniques provides greater resolution for the detection of subtle chromosomal variations not recognized by banding methods alone.