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DOE OSTI2019

Sorghum: A Multipurpose Bioenergy Crop

Bioethanol and biodiesel produced from renewable energy sources are gaining importance in light of volatile fossil fuel prices, depleting oil reserves, and increasing greenhouse effects associated with the use of fossil fuels. Among several alternative renewable energy sources, energy derived from plant biomass is found to be promising and sustainable. Sorghum [Sorghum bicolor (L.) Moench] is a resilient dryland cereal crop with wide adaptation having high water, nutrient, and radiation use efficiencies. This crop is expected to enhance food, feed, fodder, and fuel security. Sweet sorghum is similar to grain sorghum but has the ability to accumulate sugars in the stalks with- out much reduction in grain production. Hence, it is used as a first-generation biofuel feedstock, where the grain and stalk sugars can be used for producing bioenergy, while energy sorghum or biomass sorghum is increasingly viewed as a potential feedstock for lignocellulosic biofuel production. Although the commercial use of sweet sorghum for bioethanol production has been demonstrated in China and India, the viability of large-scale lignocellulosic conversion of sorghum biomass to biofuels is yet to be demonstrated. Here, this chapter dwells on sorghum feedstock characteristics, biofuel production models, sustainability indicators, and commercialization.

09 BIOMASS FUELS↗

DOE OSTI2019

Do Phycosphere associated bacteria affect the growth and lipid production of Phaeodactylum tricornutum Bohlin?

Microalgae biofuels are a promising alternative to fossil fuel energy. However current microalgal biofuel production is inefficient making it more expensive than fossil fuels. To make microalgal biofuels a realistic alternative energy source, improvements are needed in the production of microalgae biomass. Phycosphere-associated bacteria are known to influence microalgae growth and metabolite production. Understanding these interactions could provide new methods for enhancing microalgae biomass and improving the efficiency of producing microalgae biofuels. Co-cultures of Phaeodactylum tricornutum Bohlin and single bacterial species were compared to determine what impact phycosphere-associated bacteria can have on microalgae. Growth rates, total lipid accumulation and fatty acid profiles for each co-culture were compared to an axenic culture of P. tricornutum to assess the impact of the bacterial association. Marinobacter 3-2 significantly increased the lipid accumulation of P. tricornutum during early exponential growth. Two bacterial strains, Algoriphagus ARW1R1 and Muricaud a ARW1Y1, significantly lowered the maximum growth rate and cell densities of P. tricornutum in early and late exponential growth. Lower cell densities in these co-cultures resulted in lower lipid accumulation. Our results suggest that co-culturing P. tricornutum with a phycosphere-associated bacterial species, Marinobacter 3-2, could help improve the efficiency of producing algal biomass and lipids.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

An Overview of Policies Influencing Air Pollution from the Electricity Sector in South Asia

The electricity sector is a substantial source of air pollution and associated health problems in South Asia and elsewhere. Fossil-fueled power plants emit a wide variety of harmful pollutants. Those with the greatest health impacts are particulate matter and ozone. Once released into the atmosphere, there is no practical way to remove air pollutants, which means that policies designed to improve air quality have to limit the pollutants before release. However, tackling such pollution is challenging because developing economies also need to provide electricity as a basic necessity for their citizens and as an engine of economic growth. This report provides examples of policies impacting air pollution from the fossil-fuel electricity sector in the South Asian countries of Afghanistan, Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka. Some of this information was difficult to locate, so this is not a comprehensive study, but rather an overview or "scan" of the sector that includes examples of (1) policies that directly regulate air quality by limiting emissions from specific point sources (by restricting operating hours, for instance), and (2) indirect policies that incentivize or disincentivize polluting activities, such as policies to encourage fuel switching, for example. The report shows (1) the great variation among the policy instruments used in each country, (2) that many countries, especially those that have a mismatch between seasonal demand and resource availability, could improve energy security and reduce air pollution through increased cross-border electricity trade, and (3) some countries have contradictory policies (promoting both coal and renewables, for instance).

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2019

Tuning Sugarcane Bagasse Biochar into a Potential Carbon Black Substitute for Polyethylene Composites

One of the most used carbonaceous materials by industry are carbon blacks, which have technological applications in polymeric composites, coatings and paints, electric and electrochemical devices. One drawback is that they are produced from fossil fuels. Although biochars are also carbonaceous materials some disadvantages like their larger particles size, high ash content and highly oxygenated surface must be overcome to enable their use as substitute of carbon blacks in composites. Sugarcane bagasse biochar was used to produce carbonaceous materials to substitute carbon blacks. Milling of biochar decreased particle size from several hundreds of micrometers to 100–500 nm and narrowed its size distribution. Chemical leaching reduced the inorganic compounds and ash content by almost 20%. Great advance was achieved when biochar was thermally annealed in alcohol vapor atmosphere which resulted in biochar-based material with very low oxygenated carbon species at particles surface and turned them hydrophobic. Almost no C–O/C=O and O–C=O peaks components were observed at the X-ray photoelectron spectroscopy spectrum. Reactive thermal annealing of the biochar based additive was a key procedure to obtain polyethylene composites (5% loading) with mechanical, thermal and colorimetric properties very close to the ones prepared with the carbon black from fossil fuels.

36 MATERIALS SCIENCE↗

NASA NTRS2022

Source Decomposition of Eddy-Covariance CO 2 Flux Measurements for Evaluating a High-Resolution Urban CO 2 Emissions Inventory

We present the comparison of source-partitioned CO2 flux measurements with a high-resolution urban CO 2 emissions inventory (Hestia). Tower-based measurements of CO and 14 C are used to partition net CO 2 flux measurements into fossil and biogenic components. A flux footprint model is used to quantify spatial variation in flux measurements. We compare the daily cycle and spatial structure of Hestia and eddy-covariance derived fossil fuel CO 2 emissions on a seasonal basis. Hestia inventory emissions exceed the eddy-covariance measured emissions by 0.36 µ mol m −2 s −1 (3.2%) in the cold season and 0.62 µ mol m −2 s −1 (9.1%) in the warm season. The daily cycle of fluxes in both products matches closely, with correlations in the hourly mean fluxes of 0.86 (cold season) and 0.93 (warm season). The spatially averaged fluxes also agree in each season and a persistent spatial pattern in the differences during both seasons that may suggest a bias related to residential heating emissions. In addition, in the cold season, the magnitudes of average daytime biological uptake and nighttime respiration at this flux site are approximately 15% and 27% of the mean fossil fuel CO 2 emissions over the same time period, contradicting common assumptions of no significant biological CO 2 exchange in northern cities during winter. This work demonstrates the effectiveness of using trace gas ratios to adapt eddy-covariance flux measurements in urban environments for disaggregating anthropogenic CO 2 emissions and urban ecosystem fluxes at high spatial and temporal resolution.

eddy-covariance flux measurements↗

DOE OSTI2018

A study on tensile properties of Alloy 709 at various temperatures

In recent years, there have been several advancements in energy production from both fossil fuels and the alternate “clean” sources such as nuclear fission. These advancements are fueled by the need for more efficient systems that will optimize the use of the depleting fossil fuel reserves and shift the focus to cleaner sources of energy. The efficiency of any power generation cycle is dependent on the ability of the structural material to withstand increased peak operating temperatures. Advanced austenitic stainless steels have been in the focus as structural material for the next generation nuclear power plants, due to their strength, corrosion resistance, weldability and the wide range of temperatures at which the austenite phase is stable. Alloy 709, a recently developed advanced austenitic stainless steel, is being investigated in this paper. Here in this study, tensile tests were conducted on dog-bone samples of Alloy 709 in an in-situ scanning electron microscope (SEM) loading and heating stage, equipped with electron backscatter diffraction (EBSD), at various temperatures. The in-situ experiments indicated that the material primarily accommodated deformation by slip at lower temperatures. Void formation and coalescence at grain boundaries preceded slip at higher temperatures. Although crack initiation at all elevated temperatures was intergranular, the crack propagation through the material and the final fracture was transgranular ductile. Additionally, tensile tests were conducted on larger cylindrical samples at 550, 650 and 750 °C in air. The results of tests conducted in air and in-situ were found to be in agreement, at these temperatures.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Impact of solar panels on global climate

Regardless of the harmful effects of burning fossil fuels on global climate1,2, other energy sources will become more important in the future because fossil fuels could run out by the early twenty-second century3 given the present rate of consumption4. This implies that sooner or later humanity will rely heavily on renewable energy sources. Here we model the effects of an idealized large-scale application of renewable energy on global and regional climate relative to a background climate of the representative concentration pathway 2.6 scenario (RCP2.6; ref. 5). We find that solar panels alone induce regional cooling by converting incoming solar energy to electricity in comparison to the climate without solar panels. The conversion of this electricity to heat, primarily in urban areas, increases regional and global temperatures which compensate the cooling effect. However, there are consequences involved with these processes that modulate the global atmospheric circulation, resulting in changes in regional precipitation.

Environmental Sciences & Ecology↗

DOE OSTI2015

Southward shift of the northern tropical belt from 1945 to 1980

Geology↗

DOE OSTI2025

Nannochloropsis oceanica IMET1 and its bacterial symbionts for carbon capture, utilization, and storage: biomass and calcium carbonate production under high pH and high alkalinity

ABSTRACT To combat the increasing levels of carbon dioxide (CO 2 ) released from the combustion of fossil fuels, microalgae have emerged as a promising strategy for biological carbon capture, utilization, and storage. This study used a marine microalgal strain, Nannochloropsis oceanica IMET1, which thrives in high CO 2 concentrations. A high-pH, high-alkalinity culture was designed for CO 2 capture through algal biomass production as well as permanent sequestration through calcium carbonate (CaCO 3 ) precipitation. This was accomplished by timed pH elevation and the addition of sodium bicarbonate to cultures of N. oceanica grown at lab scale (1 L) and pilot scale (500 L) with 10% and 5% CO 2 , respectively. Our data showed that 0.02 M NaHCO 3 promoted algal growth and that sparging cultures with ambient air after 12 days raised pH and created favorable CaCO 3 formation conditions. At the 1 L scale, we reached 1.52 g L −1 biomass after 12 days and an extra 9.3% CO 2 was captured in the form of CaCO 3 precipitates. At the 500 L pilot scale, an extra 60% CO 2 was captured (Day 40) with a maximum CO 2 capture rate of 63.2 g m −2 day −1 (Day 35). Bacterial communities associated with the microalgae were dominated by two novel Patescibacteria. Functional analysis revealed that genes for several plant growth-promotion traits (PGPTs) were enriched within this group. The microalgal-bacterial coculture system offers advantages for enhanced carbon mitigation through biomass production and simultaneous precipitation of recalcitrant CaCO 3 for long-term CO 2 storage. IMPORTANCE Capturing carbon dioxide (CO 2 ) released from fossil fuel combustion is of the utmost importance as the impacts of climate change continue to worsen. Microalgae can remove CO 2 through their natural photosynthetic pathways and are additionally able to convert CO 2 into a stable, recalcitrant form as calcium carbonate (CaCO 3 ). We demonstrate that microalgae-based carbon capture systems can be greatly improved with high pH and high alkalinity by providing optimal conditions for carbonate precipitation. Our results with the microalga, Nannochloropsis oceanica strain IMET1, show an extra 9.3% CO 2 captured as CaCO 3 at the 1 L scale and an extra 60% CO 2 captured at the 500 L (pilot) scale. Our optimized system provides a novel approach to capture CO 2 through two mechanisms: (i) as organic carbon within microalgal biomass and (ii) as inorganic carbon stored permanently in the form of CaCO 3.

20 FOSSIL-FUELED POWER PLANTS↗

DOE OSTI2018

Fuel Cell Backup Power System for Grid-Service and Micro-Grid in Telecommunication Applications

This paper presents the feasibility and economics of using fuel cell backup power systems in telecommunication cell towers to provide grid services (e.g., ancillary services, demand response). The fuel cells are able to provide power for the cell tower during emergency conditions. This study evaluates the strategic integration of clean, efficient, and reliable fuel cell systems with the grid for improved economic benefits. The backup systems have potential as enhanced capability through information exchanges with the power grid to add value as grid services that depend on location and time. The economic analysis has been focused on the potential revenue for distributed telecommunications fuel cell backup units to provide value-added power supply. This paper shows case studies on current fuel cell backup power locations and regional grid service programs. The grid service benefits and system configurations for different operation modes provide opportunities for expanding backup fuel cell applications responsive to grid needs. The objective of this work primarily focuses on how fuel cells can become a significant part of the telecom backup power to reduce system costs, environmental impact, and dependence on fossil fuels, while ensuring continuity of indispensable service for mobile users. The study identifies the approaches on the fuel cell application through nano/microgrids for an extensive network of fuel cells as distributed energy resources. The possibilities of various application scenarios extend the fuel cell technologies and microgrid for reliable power supply.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2017

A review on technological options of waste to energy for effective management of municipal solid waste

Highlights: • The current status, options and challenges of WTE techniques were analysed. • Incineration is the most widely used WTE technology in the developed countries. • Landfilling is the most common practice of MSWM in developing countries. • Approximately 50 million tonnes of methane is emitted annually from landfills. • WTE will ensure both the energy security and environmental protection. - Abstract: Approximately one-fourth population across the world rely on traditional fuels (kerosene, natural gas, biomass residue, firewood, coal, animal dung, etc.) for domestic use despite significant socioeconomic and technological development. Fossil fuel reserves are being exploited at a very fast rate to meet the increasing energy demands, so there is a need to find alternative sources of energy before all the fossil fuel reserves are depleted. Waste to energy (WTE) can be considered as a potential alternative source of energy, which is economically viable and environmentally sustainable. The present study reviewed the current global scenario of WTE technological options (incineration, pyrolysis, gasification, anaerobic digestion, and landfilling with gas recovery) for effective energy recovery and the challenges faced by developed and developing countries. This review will provide a framework for evaluating WTE technological options based on case studies of developed and developing countries. Unsanitary landfilling is the most commonly practiced waste disposal option in the developing countries. However, developed countries have realised the potential of WTE technologies for effective municipal solid waste management (MSWM). This review will help the policy makers and the implementing authorities involved in MSWM to understand the current status, challenges and barriers for effective management of municipal solid waste. This review concluded WTE as a potential renewable source of energy, which will partly meet the energy demand and ensure effective MSWM.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2024

Sustainable Aviation Fuel from High-Strength Wastewater via Membrane-Assisted Volatile Fatty Acid Production: Experimental Evaluation, Techno-economic, and Life-Cycle Analyses

To reduce emissions from combustion of fossil fuels, sustainable aviation fuels (SAFs) have the potential to decarbonize the aviation sector. Redirecting wastes from conventional waste management practices and using them as cost-effective feedstocks for low-carbon fuels can reduce emissions from both waste disposal and fuel combustion. One approach is to upgrade wet wastes to SAF precursors, such as volatile fatty acids (VFAs). Here, in this study, novel membrane-assisted arrested methanogenesis was developed to convert high-strength wastewater to VFAs. Based on experimental results of VFA production, techno-economic and life-cycle analyses were conducted to estimate the potential economic and environmental benefits of SAF production from high-strength wastewater via VFAs. By evaluating three proposed scenarios for VFA production, a minimum production cost of VFA is achieved at $\$$0.60/kg VFA at a wastewater flow rate of 1100 MT/d. For the corresponding VFA-derived SAF, the estimated minimum fuel selling price is $\$$4.64/gasoline gallon equivalent. The life-cycle analysis shows that up to a 71% reduction in greenhouse gas emissions can be achieved relative to its fossil-counterpart along with lower water and fossil-fuel consumption.

09 BIOMASS FUELS↗

DOE OSTI2015

CO 2 hydrogenation to formate and methanol as an alternative to photo- and electrochemical CO 2 reduction

In this study, carbon dioxide is one of the end products of combustion, and is not a benign component of the atmosphere. The concentration of CO 2 in the atmosphere has reached unprecedented levels and continues to increase owing to an escalating rate of fossil fuel combustion, causing concern about climate change and rising sea levels. In view of the inevitable depletion of fossil fuels, a possible solution to this problem is the recycling of carbon dioxide, possibly captured at its point of generation, to fuels. Researchers in this field are using solar energy for CO 2 activation and utilization in several ways: (i) so-called artificial photosynthesis using photo-induced electrons; (ii) bulk electrolysis of a CO 2 saturated solution using electricity produced by photovoltaics; (iii) CO 2 hydrogenation using solar-produced H 2 ; and (iv) the thermochemical reaction of metal oxides at extremely high temperature reached by solar collectors. Since the thermodynamics of CO 2 at high temperature (> 1000 ºC) are quite different from those near room temperature, only chemistry below 200 ºC is discussed in this review.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Absorbing Aerosols Workshop, January 20-21, 2016

A workshop was held at DOE Headquarters on January 20-21, 2016 during which experts within and outside DOE were brought together to identify knowledge gaps in modeling and measurement of the contribution of absorbing aerosols (AA) to radiative forcing. Absorbing aerosols refer to those aerosols that absorb light, whereby they both reduce the amount of sunlight reaching the surface (direct effect) and heat their surroundings. By doing so, they modify the vertical distribution of heat in the atmosphere and affect atmospheric thermodynamics and stability, possibly hastening cloud drop evaporation, and thereby affecting cloud amount, formation, dissipation and, ultimately, precipitation. Deposition of AA on snow and ice reduces surface albedo leading to accelerated melt. The most abundant AA type is black carbon (BC), which results from combustion of fossil fuel and biofuel. The other key AA types are brown carbon (BrC), which also results from combustion of fossil fuel and biofuel, and dust (crustal material). Each of these sources may result from, and be strongly influenced by, anthropogenic activities. The properties and amounts of AA depend upon various factors, primarily fuel source and burn conditions (e.g., internal combustion engine, flaming or smoldering wildfire), vegetation type (in the case of BC and BrC), and in the case of dust, soil type and ground cover (i.e., vegetation, snow, etc.). After emission, AA undergo chemical processing in the atmosphere that affects their physical and chemical properties. Thus, attribution of sources of AA, and understanding processes AA undergo during their atmospheric lifetimes, are necessary to understand how they will behave in a changing climate.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Radically Engineered Modular Air Separation System with Tailored Oxygen Sorbents

The commercial energy sector relies heavily on fossil fuel conversion, and in the process releases a significant amount of CO 2 . A promising technology to utilize fossil fuels with relatively affordable CO 2 capture is gasification. However, it requires a pure oxygen stream. The current state of the art method to produce oxygen is cryogenic air separation, which supercools air to a liquid, and then using distillation columns to separate the components. While this method has been thoroughly studied, it only has a 25% efficiency from a second law standpoint and therefore requires a significant amount of energy (and associated emissions) for oxygen production. This, then, lowers the incentive for carbon capture within a plant, so alternative methods need to be investigated. One potential method, chemical looping air separation (CLAS), is a promising method to replace state of the art oxygen generation technologies. CLAS utilizes a cyclic redox scheme with an oxygen sorbent to create pure oxygen streams. This approach typically utilizes a dual reactor scheme where the oxygen deficient sorbent enters the first reactor and is subjected to high oxygen partial pressures to re-oxidize the sorbent. Then the sorbent is sent to the reducing reactor, where it is subjected to low oxygen partial pressure (steam or vacuum) to releases oxygen. The overarching objective of this project was to discover the principles for rational design and optimization of oxygen sorbents and process design to ensure the process is a viable replacement for cryogenic air separation, especially in the context of modular gasification systems. This was done through development, characterization, testing, and analyses of (a) high temperature mixed composite oxides; (b) low temperature doped perovskite oxides (A1 x A2 1-x B1 y B2 1-y O 3 ); (c) scale up synthesis and testing of the optimized sorbent particles; (d) process design and analyses of the CLAS system in the context of modular gasification applications.

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2024

Life Cycle Greenhouse Gas Emissions of Coal-Biomass Co-Firing Power Plants with Carbon Capture and Storage

The United States has set a target to achieve the net-zero economy by 2050. Bioenergy with Carbon Capture and Sequestration (BECCS) is one of the promising negative-emission routes in the mitigation portfolio to help meet this goal. Coal-biomass co-firing with carbon capture and storage (CCS) is a key BECCS technology to realize the carbon mitigation at fossil-fuel power plants. The mitigation potential of co-firing option is affected by numerous critical factors, such as biomass properties, co-firing level, and carbon capture rate. The objectives of the study are to characterize and estimate the life cycle greenhouse gas (GHG) emissions and performance of coal-biomass co-firing power plants with CCS, determine the breakeven co-firing level at power plants necessary to achieve net-zero life cycle emissions, and quantify the variabilities and uncertainties in life cycle emissions. The scope of the life cycle assessment includes the fuel supply, combustion-based power generation, and CO2 transport and storage. A fuel-based life cycle module is developed and embedded in the Integrated Environmental Control Model (IECM), a fossil-fuel power plant modeling tool. This study then applies the enhanced IECM to conduct the process-based life cycle assessment for an array of biomass co-firing scenarios. Deterministic analysis indicates that reaching net-zero life cycle emissions in a biomass co-firing plant without CCS deployment is challenging. Combining biomass co-firing and CCS deployment can significantly lower the overall life cycle emissions of power plants. Net-zero life cycle emissions can be achieved with a 20 wt.% co-firing level and 90% CCS when the Powder River Basin coal is co-fired with energy crops or forestry residues. However, the breakeven co-firing level for net-zero emissions depend on the selected fuel properties. Fuel supply and plant operation are the critical stages influencing the life cycle emissions of power plants with 90% CCS. Deployment of deep CCS beyond 90% CO2 capture can remarkably reduce operational emissions and the breakeven co-firing level. With 99% CCS, the breakeven co-firing rate can be reduced to 12% on average. These findings highlight the trade-offs between technical performance and environmental impact of biomass co-firing at coal-fired power plants and emphasize the role of deep CCS in achieving a net-zero emissions future.

Wu, Wanying↗

DOE OSTI2025

Updated Natural Gas Pathways in R&D GREET 2024 Rev.1

Natural gas (NG) is a relatively low-cost fossil fuel with vast infrastructure in the United States (U.S.) making it easier to transport and store compared to other fossil fuels such as coal and petroleum. In 2023, the U.S. consumed 32.5 trillion cubic feet or 33.6 Quad Btu of NG, accounting for 36% of the nation’s total primary energy consumption. NG is commonly used for electricity generation, industrial applications, commercial and residential activities and transportation purposes, as shown in Figure 1. This widespread reliance on NG underscores the need to assess its full environmental impact, requiring careful analysis of the entire supply chain from production (i.e., recovery, gathering and boosting [G&B], and processing of raw gas) to final delivery to end users (e.g., via pipelines).

03 NATURAL GAS↗

NASA NTRS1978

Hydrogen turbine power conversion system assessment

A three part technical study was conducted whereby parametric technical and economic feasibility data were developed on several power conversion systems suitable for the generation of central station electric power through the combustion of hydrogen and the use of the resulting heat energy in turbogenerator equipment. The study assessed potential applications of hydrogen-fueled power conversion systems and identified the three most promising candidates: (1) Ericsson Cycle, (2) gas turbine, and (3) direct steam injection system for fossil fuel as well as nuclear powerplants. A technical and economic evaluation was performed on the three systems from which the direct injection system (fossil fuel only) was selected for a preliminary conceptual design of an integrated hydrogen-fired power conversion system.

Wright, D. E.↗