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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Representing cropping systems with the MEMS 2 ecosystem model

Abstract Croplands have been the focus of substantial investigation due to their considerable potential for sequestering carbon. Understanding the potential for soil organic carbon (SOC) sequestration and necessary management strategies will be enabled with accurate process‐based models. Accurately representing crop growth and agricultural practices will be critical for realistic SOC modeling. The MEMS 2 model incorporates a current understanding of SOC formation and stabilization, measurable SOC pools, and deep SOC dynamics and is seen as a highly promising tool to inform management intervention for SOC sequestration. Thus far, MEMS 2 has been developed to represent grasslands. In this study, we further developed MEMS 2 to model annual grain crops and common agricultural practices, such as irrigation, fertilization, harvesting, and tillage. Using four Ameriflux sites, we demonstrated an accurate simulation of crop growth and development. Model performance was strong for simulating aboveground biomass (index of agreement [d] range of 0.89–0.98) and green leaf area index (dfrom 0.90 to 0.96) across corn, soybean, and winter wheat. Good agreement with observations was also achieved for net ecosystem CO 2 exchange (dfrom 0.90 to 0.96), evapotranspiration (dfrom 0.91 to 0.94), and soil temperature (dof 0.96), while discrepancy with the available soil water content data remain (dfrom 0.14 to 0.81 at four depths to 100 cm). While we will continue model testing and improvement, MEMS 2 (version 2.14) has now demonstrated its ability to effectively simulate the growth of common grain crops and practices.

Agriculture↗
DOE OSTI2018

Ambient Electrosynthesis of Ammonia: Electrode Porosity and Composition Engineering

Ammonia, a key precursor for fertilizer production, convenient hydrogen carrier, and emerging clean fuel, plays a pivotal role in sustaining life on Earth. Currently, the main route for NH 3 synthesis is by the heterogeneous catalytic Haber–Bosch process (N 2 +3 H 2 →2 NH 3 ), which proceeds under extreme conditions of temperature and pressure with a very large carbon footprint. Herein we report that a pristine nitrogen–doped nanoporous graphitic carbon membrane (NCM) can electrochemically convert N 2 into NH 3 in an acidic aqueous solution under ambient conditions. The Faradaic efficiency and rate of production of NH 3 on the NCM electrode reach 5.2 % and 0.08 g m –2 h –1 , respectively. Functionalization of the NCM with Au nanoparticles dramatically enhances these performance metrics to 22 % and 0.36 gm –2 h –1 , respectively. In conclusion, as this system offers the potential to be scaled to industrial levels it is highly likely that it might displace the century-old Haber–Bosch process.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Quantum Anomalies in Condensed Matter

Quantum materials provide a fertile ground in which to test and realize unusual phenomena such as quantum anomalies predicted by quantum field theory. There are three important symmetries that are broken when classical field theory is moved into the quantum regime, the scale anomaly, the axial (chiral) anomaly, and the parity anomaly. Several potential device applications may be realized by the discovery of quantum anomalies in condensed matter, enabled by the new physics they embody, including ultra‐sensitive dark matter detectors, far infrared optical modulators, micro‐bolometric detectors, low‐dissipation ballistic transporters, terahertz‐based qubits, terahertz polarization state controls, passive magnetic field sensors, stable topological superconductors that host Majorana fermions, and qubits topologically protected against decoherence. In this perspective article, the definition of these quantum anomalies is laid out, how little is known in the context of condensed matter, and how quantum anomalies are predicted to manifest as anomalous electronic, thermal, and magnetic behavior in experiments on topological quantum materials, including Weyl and Dirac semimetals. Furthermore, the importance that mechanical strain and defects will play in modifying signatures of quantum anomalies is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Techno‐economic assessment of single‐stream feedstock logistics supply chain for corn stover and grain

Abstract The state‐of‐technology for corn stover harvest is a multi‐pass system that collects the stover after grain harvest. An alternative is a single‐stream system where the grain and stover are harvested as a bulk material co‐stored and preserved by anerobic fermentation, and finally, co‐transported to a biorefinery. In the present work, four single‐pass whole‐plant bulk systems were compared with a conventional multi‐pass bale system. The single‐stream systems consisted of the harvest of corn grain and a portion of the stover fraction. Four machine configurations were simulated. This work predicted that a multi‐pass bale system would result in a material cost of 111.80 $2021 Mg –1 stover DM delivered to the biorefinery gate. Alternatively, the lowest cost single‐stream system was the self‐propelled forage harvester (SPFH) configured with the whole‐plant header, which delivered feedstock for 74.76 $2021 Mg stover DM –1 . In addition to machine configuration, a sensitivity analysis was performed to understand important drivers of feedstock cost. These analyses revealed that feedstock cost increased with moisture content, fertilizer price, and biorefinery size, and decreased with harvest season length, crop yield, and grower participation. This work demonstrated that single‐stream systems could reduce corn stover feedstock costs in comparison with state‐of‐technology systems. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

09 BIOMASS FUELS↗
DOE OSTI2018

Sugar yield and composition of tubers from Jerusalem Artichoke ( Helianthus tuberosus ) irrigated with saline waters

Abstract Currently, major biofuel crops are also food crops that demand fertile soils and good‐quality water. Jerusalem artichoke ( Helianthus tuberosus , Asteraceae) produces high tonnage of tubers that are rich in sugars, mainly in the form of inulin. In this study, plants of the cultivar “White Fuseau” grown under five salinity levels were evaluated for tuber yield. Results indicated that this cultivar is moderately salt‐tolerant if the goal is tuber production. Hydraulic pressings of the tubers produced juice that contained 15% (wet weight) or 55% (dry weight) free sugars, with 70% of these in the form of inulin and the rest as fructose, sucrose, and glucose. Importantly, salinity did not affect the total free sugar or inulin content of the tubers. Tubers were composed of about 12% dry washed bagasse (wet weight) or 44% (dry matter basis) and bagasse retained such high quantities of free sugars after pressing that washing was required for complete sugar recovery. Chemical composition analysis of tuber bagasse suggested that it had low lignin content (11–13 wt%), and its structural sugar composition was similar to chicory root bagasse. Because of the high hemicellulose and pectin content of the bagasse, adding xylanase and pectinase to cellulase substantially improved sugar yields from enzymatic hydrolysis compared to at the same protein loading as cellulase alone. In addition to the high total sugar yield of tuber, these first findings on the sugar and lignin content and enzymatic hydrolysis of tuber bagasse can lead to low‐cost production of ethanol for transportation fuels.

Bhagia, Samarthya↗
DOE OSTI2018

Morphogenic Regulator-Mediated Transformation of Maize Inbred B73

Maize B73 is a reference genome and has long been a major resource for genetics and molecular biology research. We have developed an efficient B73 transformation protocol by enabling somatic embryogenesis through differential co-expression of maize morphogenic regulators BBM and WUS2. We describe a successful protocol that utilizes Agrobacterium tumefaciens strain AGL1 harboring binary vector PHP78891 that comprises a BBM and WUS2 expression cassette as well as a green fluorescent protein (GFP) reporter cassette. The PHP78891 vector also contains, within the T-DNA region, a CRE/lox recombination system flanking the CRE/BBM/WUS2 co-expression cassette driven by the desiccation inducible RAB17 promoter that allows removal of the BBM/WUS2 cassette. Introduction and co-expression of BBM and WUS2 induced direct somatic embryogenesis (SE) in non-regenerable maize B73 from immature embryo explants. Removal of the CRE/BBM/WUS2 cassette is essential to allow regeneration to fertile plants. The GFP expression cassette outside the lox excision sites is retained in the transgenic plant genome, allowing subsequent phenotypic analysis of calli and regenerated transgenic events. This transformation system enables a selectable marker-free transformation process by taking advantage of BBM/WUS2-induced SE as a developmental selection system.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Screening and Discovery of Metal Compound Active Sites for Strong and Selective Adsorption of N 2 in Air

Photocatalytic nitrogen fixation has the potential to provide a greener route for producing nitrogen-based fertilizers under ambient conditions. Computational screening is a promising route to discover new materials for the nitrogen fixation process, but requires identifying “descriptors” that can be efficiently computed. In this work, we argue that selectivity toward the adsorption of molecular nitrogen and oxygen can act as a key descriptor. A catalyst that can selectively adsorb nitrogen and resist poisoning of oxygen and other molecules present in air has the potential to facilitate the nitrogen fixation process under ambient conditions. Here we provide a framework for active site screening based on multifidelity density functional theory (DFT) calculations for a range of metal oxides, oxyborides, and oxyphosphides. The screening methodology consists of initial low-fidelity fixed geometry calculations and a second screening in which more expensive geometry optimizations were performed. The approach identifies promising active sites on several TiO 2 polymorph surfaces and a VBO 4 surface, and the full nitrogen reduction pathway is studied with the BEEF-vdW and HSE06 functionals on two active sites. The findings suggest that metastable TiO 2 polymorphs may play a role in photocatalytic nitrogen fixation, and that VBO 4 may be an interesting material for further studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Electrocatalytic CN Coupling: Advances in Urea Synthesis and Opportunities for Alternative Products

Urea is an essential fertilizer produced through the industrial synthesis of ammonia (NH 3 ) via the Haber–Bosch process, which contributes ≈1.2% of global annual CO 2 emissions. Electrocatalytic urea synthesis under ambient conditions via CN coupling from CO 2 and nitrogen species such as nitrate (NO 3 − ), nitrite (NO 2 − ), nitric oxide (NO), and nitrogen gas (N 2 ) has gained interest as a more sustainable route. However, challenges remain due to the unclear reaction pathways for urea formation, competing reactions, and the complexity of the resulting product matrix. This review highlights recent advances in catalyst design, urea quantification, and intermediate identification in the CN coupling reaction for electrocatalytic urea synthesis. Furthermore, this review explores future prospects for industrial CN coupling, considering potential nitrogen and carbon sources and examining alternative CN coupling products, such as amides and amines.

Chemistry↗
DOE OSTI2018

The role of environmental driving factors in historical and projected carbon dynamics of wetland ecosystems in Alaska

Abstract Wetlands are critical terrestrial ecosystems in Alaska, covering ~177,000 km 2 , an area greater than all the wetlands in the remainder of the United States. To assess the relative influence of changing climate, atmospheric carbon dioxide (CO 2 ) concentration, and fire regime on carbon balance in wetland ecosystems of Alaska, a modeling framework that incorporates a fire disturbance model and two biogeochemical models was used. Spatially explicit simulations were conducted at 1‐km resolution for the historical period (1950–2009) and future projection period (2010–2099). Simulations estimated that wetland ecosystems of Alaska lost 175 Tg carbon (C) in the historical period. Ecosystem C storage in 2009 was 5,556 Tg, with 89% of the C stored in soils. The estimated loss of C as CO 2 and biogenic methane (CH 4 ) emissions resulted in wetlands of Alaska increasing the greenhouse gas forcing of climate warming. Simulations for the projection period were conducted for six climate change scenarios constructed from two climate models forced under three CO 2 emission scenarios. Ecosystem C storage averaged among climate scenarios increased 3.94 Tg C/yr by 2099, with variability among the simulations ranging from 2.02 to 4.42 Tg C/yr. These increases were driven primarily by increases in net primary production (NPP) that were greater than losses from increased decomposition and fire. The NPP increase was driven by CO 2 fertilization (~5% per 100 parts per million by volume increase) and by increases in air temperature (~1% per °C increase). Increases in air temperature were estimated to be the primary cause for a projected 47.7% mean increase in biogenic CH 4 emissions among the simulations (~15% per °C increase). Ecosystem CO 2 sequestration offset the increase in CH 4 emissions during the 21st century to decrease the greenhouse gas forcing of climate warming. However, beyond 2100, we expect that this forcing will ultimately increase as wetland ecosystems transition from being a sink to a source of atmospheric CO 2 because of (1) decreasing sensitivity of NPP to increasing atmospheric CO 2 , (2) increasing availability of soil C for decomposition as permafrost thaws, and (3) continued positive sensitivity of biogenic CH 4 emissions to increases in soil temperature.

Lyu, Zhou↗
DOE OSTI2019

Ringed seal demography in a changing climate

Abstract Climate change is affecting species’ distributions and abundances worldwide. Baseline population estimates, against which future observations may be compared, are necessary if we are to detect ecological change. Arctic sea ice ecosystems are changing rapidly and we lack baseline population estimates for many ice‐associated species. Provided we can detect them, changes in Arctic marine ecosystems may be signaled by changes in indicator species such as ringed seals ( Pusa hispida ). Ringed seal monitoring has provided estimates of survival and fertility rates, but these have not been used for population‐level inference. Using matrix population models, we synthesized existing demographic parameters to obtain estimates of historical ringed seal population growth and structure in Amundsen Gulf and Prince Albert Sound, Canada. We then formalized existing hypotheses about the effects of emerging environmental stressors (i.e., earlier spring ice breakup and reduced snow depth) on ringed seal pup survival. Coupling the demographic model to ice and snow forecasts available from the Coupled Model Intercomparison Project resulted in projections of ringed seal population size and structure up to the year 2100. These projections showed median declines in population size ranging from 50% to 99%. Corresponding to these projected declines were substantial changes in population structure, with increasing proportions of ringed seal pups and adults and declining proportions of juveniles. We explored if currently collected, harvest‐based data could be used to detect the projected changes in population stage structure. Our model suggests that at a present sample size of 100 seals per year, the projected changes in stage structure would only be reliably detected by mid‐century, even for the most extreme climate models. This modeling process revealed inconsistencies in existing estimates of ringed seal demographic rates. Mathematical population models such as these can contribute both to understanding past population trends as well as predicting future ones, both of which are necessary if we are to detect and interpret future observations.

Reimer, Jody R.↗
DOE OSTI2022

The climate change mitigation potential of annual grasslands under future climates

Abstract Composted manure and green waste amendments have been shown to increase net carbon (C) sequestration in rangeland soils and have been proposed as a means to help lower atmospheric CO 2 concentrations. However, the effect of climate change on soil organic C (SOC) stocks and greenhouse gas emissions in rangelands is not well understood, and the viability of climate change mitigation strategies under future conditions is even less certain. We used a process‐based biogeochemical model (DayCent) at a daily time step to explore the long‐term effects of potential future climate changes on C and greenhouse gas dynamics in annual grassland ecosystems. We then used the model to explore how the same ecosystems might respond to climate change following compost amendments to soils and determined the long‐term viability of net SOC sequestration under changing climates. We simulated net primary productivity (NPP), SOC, and greenhouse gas fluxes across seven California annual grasslands with and without compost amendments. We drove the DayCent simulations with field data and with site‐specific daily climate data from two Earth system models (CanESM2 and HadGEM‐ES) and two representative concentration pathways (RCP4.5 and RCP8.5) through 2100. NPP and SOC stocks in unamended and amended ecosystems were surprisingly insensitive to projected climate changes. A one‐time amendment of compost to rangeland acted as a slow‐release organic fertilizer and increased NPP by up to 390–814 kg C ha −1 year −1 across sites. The amendment effect on NPP was not sensitive to Earth system model or emissions scenario and endured through the end of the century. Net SOC sequestration amounted to 1.96 ± 0.02 Mg C ha −1 relative to unamended soils at the maximum amendment effect. Averaged across sites and scenarios, SOC sequestration peaked 22 ± 1 years after amendment and declined but remained positive throughout the century. Though compost stimulated nitrous oxide (N 2 O) emissions, the cumulative net emissions (in CO 2 equivalents) due to compost were far less than the amount of SOC sequestered. Compost amendments resulted in a net climate benefit of 69.6 ± 0.5 Tg CO 2 e 20 ± 1 years after amendment if applied to similar ecosystems across the state, amounting to 39% of California's rangeland. These results suggest that the biogeochemical benefits of a single amendment of compost to rangelands in California are insensitive to climate change and could contribute to decadal‐scale climate change mitigation goals alongside emissions reductions.

Mayer, Allegra↗
DOE OSTI2018

Litter chemistry influences decomposition through activity of specific microbial functional guilds

Abstract Niche differentiation among species is a key mechanism by which biodiversity may be linked to ecosystem function. We tested a set of widely invoked hypotheses about the extent of niche differentiation in one of the most diverse communities on Earth, decomposer microorganisms, by measuring their response to changes in three abundant litter resources: lignin, cellulose, and nitrogen (N). To do this, we used the model system Arabidopsis thaliana to manipulate lignin, cellulose, and N availability and then used high‐throughput sequencing to measure the response of microbial communities during decay. Resequencing the decomposer communities after incubation of decomposed litter with pure substrates showed that groups of species had unique substrate use profiles, such that species organized into functional “guilds” of decomposers that were associated with individual litter chemicals. Low concentrations of lignin, cellulose, or N in the litter caused unique shifts in decomposer community composition after 1 yr of decay. Low cellulose plants had low levels of fungi in all decomposer guilds, low lignin plants had high levels of fungi in all decomposer guilds, and low N plants had low levels of fungi in decomposer guilds associated with sucrose and lignin. The relative abundance of decomposer guilds correlated with the total loss of individual litter chemicals during litter decay in the field. In addition, N fertilization shifted decomposer communities during both the early and later stages of decay to those dominated by decomposers in the cellulose guild. Our results contrast the assumption that major carbon (C) and N degradation mechanisms are uniform across whole decomposer communities and instead suggest that decomposition arises from complementarity among groups of metabolically distinct taxa.

Bhatnagar, Jennifer M.↗
DOE OSTI2017

Soil-mediated effects of global change on plant communities depend on plant growth form

Understanding why species respond to climate change is critical for forecasting invasions, diversity, and productivity of communities. Although researchers often predict species’ distributions and productivity based on direct physiological responses to environments, theory suggests that striking shifts in community composition could arise if global change alters indirect feedbacks mediated by resources, mutualists, or antagonists. To test whether global change influences plant communities via soil–mediated feedbacks, we grew model communities in soils collected from a seven–year field manipulation of CO 2 , warming, and invasion. We evaluated mechanisms underlying variation in the model communities by comparing species’ growth in equivalent soil histories with, and without, experimentally reduced soil biota (via sterilization) and nutrient limitation (via fertilization). We show that grasses performed consistently across all soil history scenarios and that soil biota limited grasses more than nutrients. In contrast, forbs were differentially sensitive to soil history scenarios, with the magnitude and direction of responses to soil biota and nutrients dependent upon plant species and global change scenario. The asymmetry in importance of soil history for grasses and forbs is likely explained by differences in life history strategy. We conclude that accounting for species’ growth strategies will improve predictions of species sensitivity to altered soil feedbacks in future climates.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Land use intensification in the humid tropics increased both alpha and beta diversity of soil bacteria

Anthropogenic pressures on tropical forests are rapidly intensifying, but our understanding of their implications for biological diversity is still very limited, especially with regard to soil biota, and in particular soil bacterial communities. Here we evaluated bacterial community composition and diversity across a gradient of land use intensity in the eastern Amazon from undisturbed primary forest, through primary forests varyingly disturbed by fire, regenerating secondary forest, pasture, and mechanized agriculture. Soil bacteria were assessed by paired-end Illumina sequencing of 16S rRNA gene fragments (V4 region). The resulting sequences were clustered into operational taxonomic units (OTU) at a 97% similarity threshold. Land use intensification increased the observed bacterial diversity (both OTU richness and community heterogeneity across space) and this effect was strongly associated with changes in soil pH. Moreover, land use intensification and subsequent changes in soil fertility, especially pH, altered the bacterial community composition, with pastures and areas of mechanized agriculture displaying the most contrasting communities in relation to undisturbed primary forest. Together, these results indicate that tropical forest conversion impacts soil bacteria not through loss of diversity, as previously thought, but mainly by imposing marked shifts on bacterial community composition, with unknown yet potentially important implications for ecological functions and services performed by these communities.

16S rRNA gene↗
DOE OSTI2017

Biological soil crusts: diminutive communities of potential global importance

Biological soil crusts (biocrusts) are widespread, diverse communities of cyanobacteria, fungi, lichens, and mosses living on soil surfaces, primarily in drylands. Biocrusts can locally govern primary production, soil fertility, hydrology, and surface energy balance, with considerable variation in these functions across alternate community states. Further, these communities have been implicated in Earth system functioning via potential influences on global biogeochemistry and climate. Biocrusts are easily destroyed by disturbances and appear to be exceptionally vulnerable to warming temperatures and altered precipitation inputs, signaling possible losses of dryland functions with global change. Despite these concerns, we lack sufficient spatiotemporal data on biocrust function, cover, and community structure to confidently assess their ecological roles across the extensive dryland biome. Here, we present the case for cross-scale research and restoration efforts coupled with remote-sensing and modeling approaches that improve our collective understanding of biocrust responses to global change and the ecological roles of these diminutive communities at global scales.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Photon to plate: A holistic view of photosynthetic and anthropogenic energy fluxes

Modern agriculture couples photosynthetic energy with human-applied energy supplements (e.g., fertilizers, labor, cultivation) to feed a growing population. These energy supplements usually come from fossil fuels, presenting an opportunity to decrease fossil fuel required per calorie by improving photosynthetic efficiency. To quantify how improving photosynthetic efficiency would decrease the supplemental energy needed per calorie, we present a “photon to plate” life cycle analysis of energy flows (photosynthetic and human-applied) needed to produce fresh-cut fries. Our results show that photosynthetic inefficiencies require ~80 times the energy used to cultivate, harvest, transport and prepare fries for consumption and that improvements to photosynthesis could reduce the energy applied by humans per calorie by almost 40%. This study highlights the magnitude of energy used during photosynthesis and the potential for photosynthetic improvements to increase agricultural sustainability.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

The Bear Brook Watershed in Maine: Multi-Decadal Whole-Watershed Experimental Acidification

The Bear Brook Watershed in Maine (BBWM) is a long-term research site established to study the response of forest ecosystem function to environmental disturbances of chronic acidic deposition and ecosystem nitrogen enrichment. Starting in 1989, the West Bear (treated) watershed received bimonthly applications of ammonium sulfate [(NH4)2SO4] fertilizer from above the canopy, whereas East Bear (reference) received ambient deposition. The treatments were stopped in 2016, marking the beginning of the recovery phase. Research at the site has focused on soils, streams, and vegetation. Here, we describe data collected over three decades at the BBWM—input and stream output nutrient fluxes, quantitative soil pits and soil chemistry, and soil temperature and moisture.

Patel, Kaizad F.↗