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Despite potential advantages in spatial/temporal coverage compared to measurement studies, few modeling studies have been conducted of non-methane air pollutants associated with natural gas. The objective of this study was to model volatile organic compound (VOC) and criteria pollutants from natural gas production, considering multiple well pads under different terrain conditions, using the Texas Barnett Shale as a case study. Primary criteria pollutants from compressor engines (carbon monoxide, CO; nitrogen oxides, NOx; particulate matter, PM10; sulfur dioxide, SO2) were modeled using AERMOD, along with benzene as a VOC with potential worst health impacts, from condensate tanks, fugitive sources, and compressor engines. Modeling was conducted for level, moderate, and strong sloping terrain, with well pad densities of 1.4–1.9 well pads/km2, exemplifying common maximum densities in the Barnett Shale. In most cases, well pads were far enough away from each other that maxima at individual well pads were not influenced by other pads. When the same well pad arrangement and emission rates were modeled in different terrain types, strong sloping terrain gave the highest maximum concentrations. For the well pad arrangements and emission scenarios modeled, CO, NOx, PM10, and SO2 maximum concentrations were less than the 1-h National Ambient Air Quality Standards (NAAQS). Benzene concentrations, however, exceeded the 1-h effect screening level (ESL) for level and strong sloped terrain, and the annual ESL for all terrain types. The maximum benzene emissions modeled likely represent a reasonable worst-case for the Barnett Shale but underestimate emissions for areas with wetter gas.

The goal of this study was to conduct a comprehensive life cycle assessment (LCA) for large onshore wind turbines in the US, including all phases of the turbine’s life cycle separately (materials acquisition, manufacturing, transportation, installation, operation and maintenance, and end of life) and multiple impact categories (environmental, human health, resource consumption). Particular attention was given to make the installation and maintenance phases complete and transparent. The contribution of this study is that it is the first comprehensive LCA for large wind turbines in the US, where different transport distances (including overseas transport of turbine parts), truck emission standards, mixes of electricity sources, and waste disposal practices will affect impacts, compared to those conducted for other countries. It is also the first comprehensive LCA to examine separately all 6 phases of the turbine’s life cycle (in particular separating manufacturing from raw material acquisition/installation) and the first to evaluate turbine lifespan as a sensitivity parameter. The study was conducted for 200 Gamesa 2-MW wind turbines located near Abilene, Texas. SimaPro8 software was used for modeling, according to ISO 14040 standards. The manufacturing phase contributed the greatest overall impacts, which was consistent with other studies; hence, alternative methods of manufacturing should be explored to reduce impacts. Installation, transportation, maintenance, and raw materials acquisition ranked second through fifth, respectively. Consistent with other studies, end-of-life ranked last, which means that the disposal method (landfilling or combustion) for turbine parts which are not recycled makes little difference in terms of the overall turbine life cycle.

As cities strive for more sustainable transportation systems, many are considering renewable fuels for fleets. Biogas has several advantages as an alternative fuel. Composed primarily of methane, it can be cleaned for use in natural gas vehicles or burned in a turbine/engine to generate electricity for electric vehicles. Biogas can reduce air pollutant emissions from fleet vehicles; in addition, if wastes are used to produce the biogas in digesters, the problem of urban wastes is reduced. Many cities already have anaerobic digesters that convert sewage sludge at water resource recovery facilities (WRRFs) to biogas. Because of its abundance in landfilled waste (22%), food waste is of current critical concern to the US Environmental Protection Agency. Yard (flora) waste comprises an additional 7.8% of waste going to landfills. Both food and yard waste could be used to boost biogas production in WRRF digesters. One main question is: What WRRF locations with existing digesters are the best candidates to produce vehicle fuel from food/yard waste? In this paper, we present an optimization that balances trade-offs between food/yard waste transportation costs and capital/operating costs for expanding digesters. An example study is conducted for the City of Dallas, Texas.

Lignocellulose comprises a significant portion of municipal solid waste (MSW) - 40-70% in developed countries, including paper, wood, and yard waste. Cellulose and hemicellulose are often shielded by lignin, posing a barrier to waste decomposition and landfill gas generation. Unfortunately, lignin is resistant to microbial degradation under low-oxygen conditions that normally occur in MSW landfills. The bacterium strain TAV5, microaerophilic and member of phylum Verrucomicrobia, isolated from the hindgut of the Reticulitermes flavipes termite, the most widely distributed subterranean termite in North America. Its genome contains genes associated with methylotrophic competency which code for enzymes that structurally modify lignin. The overall goal of this research was to use TAV5 to modify lignin and boost methane production from MSW. Batch-scale reactors (125mL) were filled with paper, yard, or wood waste, and four ratios of mixed of waste. Reactors were seeded with different ratios of TAV5 to anaerobic digester (AD) microorganisms (representing landfill anaerobic microorganisms). Based on batch tests, optimal ratios of TAV5 to AD microorganisms were used to seed wastes (mixed, yard, and wood) in 6-gallon reactors. Addition of TAV5 increased methane production from mixed waste, yard waste, and wood, by 49%, 34%, and 297%, respectively. TAV5 decreased acid soluble lignin by 7-39%, depending on waste type. TAV5 grown under aerobic conditions and room temperature (not requiring a heated anaerobic chamber) was found to remain viable and increase methane production under low-level oxygen conditions (1-2%). This finding will potentially lessen costs for growing large volumes of it for seeding landfills.

Chemical components of airborne volatile organic compounds (VOCs) released from a wastewater treatment system of the tapioca industry were identified. Quantitative analysis of the concentrations and the emissions of each chemical were evaluated taking into consideration the difference in atmospheric turbulence over the surface of the wastewater during the day and the nighttime periods. The chamber experiments were performed on-site in order to reflect actual environmental characteristics of the study area. Chemical concentrations were analyzed following the U.S. EPA TO-15 Standard Method. Emissions of each compound were calculated using the box model scheme. It was found that acetaldehyde and acetone were two major compounds of released airborne VOCs from the wastewater treatment system of the tapioca industry. Due to its high organic content, the wastewater treatment facilities of this type of factory generally caused the odor problem to its surrounding communities. These data were then used to evaluate the success of implementing the Clean Development Mechanisms project in this industry. Reduction in the affected area from odor by improving the wastewater treatment system from opened lagoons which is the type of common practice in most of the tapioca factories in the developing countries to the modified covered lagoons was evaluated. These results supported the theory of the co-benefit of managing both local environmental problems and reduction of greenhouse gas emissions from the implementation of cleaner technology in the agro-industry. This methodology can be applied to reveal and quantify the success of other green efforts particularly in the agro-industry businesses.

Emission factors for speciated volatile organic compounds (VOCs) from maize residue burning were determined in this study based on chamber experiments. Thirty-six VOC species were identified by Gas Chromatography/Mass Spectrometer (GC/MS). They were classified into six groups, including alkanes, alkenes, oxygenated VOCs, halogenated VOCs, aromatics and other. The emission factor for total VOCs was estimated as about 148 mg kg−1 dry mass burned. About 68.4% of the compounds were aromatics. Field samplings of maize residues were conducted to acquire the information of fuel characteristics including fuel loading, fraction of maize residues that were actually burned as well as proximate and elemental analysis of maize residues. The emission factors were then applied to estimate speciated VOC emissions from maize residue open burning at the provincial level in the upper-northern region of Thailand for the year 2014. Total burned area of maize covered an area of about 500,000 ha which was about 4.7% of the total area of upper-northern region of the country. It was found that total VOC emissions released during the burning season (January–April) was about 79.4 tons. Ethylbenzene, m,p-xylene, 1,2,4-trimethylbenzene, acetaldehyde and o-xylene were the major contributors, accounting for more than 65% of total speciated VOC emissions.

Global ethanol production generates almost 100 billion liters per year of a high-strength liquid waste called vinasse. One sustainable method of treating vinasse using environmental biotechnology is anaerobic digestion, which generates biogas that can be used as a renewable energy resource. Although a number of models have been developed for predicting biogas generation rates, no previous study has modeled liquid organic removal rates for vinasse treatment. The goal of this research was thus to develop models for predicting liquid-phase organic removal rates for anaerobic treatment of vinasse. 6-L laboratory-scale batch reactors were filled with vinasse of six different compositions and operated at three different mesophilic temperatures (30, 35, 40 °C). Biochemical and chemical oxygen demand (BOD and COD) were measured over time using Standard Methods 5210B and 5220C. Based on data collected, multiple linear regression equations (R2 = 0.79 and 0.94) were developed to predict first-order rate constants kBOD and kCOD as functions of temperature and vinasse composition (initial values of nitrogen, potassium, phosphorous, and sulfur). The first-order models developed require a small number of readily available input parameters. They apply to treatment of vinasse from ethanol produced from corn and milo; future work can test their applicability to ethanol produced from other feedstocks. The models can be used for sizing/design of reactors for anaerobic treatment of vinasse.

Road transports in the United States (U.S.) are heavily dependent on the production and consumption of fossil fuel. This high dependency on fossil fuels contributes significantly to carbon dioxide (CO2) emission, one of the leading Green House Gases (GHGs) responsible for global warming. Electrification of passenger vehicles could be an effective strategy to curb GHG emissions. Though Electric Vehicles (EVs) have zero tailpipe emissions, the power required to charge EV batteries may not necessarily come from carbon-free power plants. In this study, for a comprehensive comparison among EV, Plug-in Hybrid Electric Vehicle (PHEV), and Gasoline Vehicle (GV), we developed an agent-based simulation modeling framework for the entire energy pathway (Well-To-Wheel). As a case study, we estimated and compared CO2 emissions for different driving cycles for Texas utilizing 2018 electricity production mix data. Our simulation results revealed that for city driving cycles, EV performed environmentally better than GV and PHEV, but for highway driving cycles, EV underperformed compared to PHEV in all traffic conditions. For a combined driving cycle, PHEV performed better compared to EV and GV in moderate and low traffic conditions. Overall, according to the year 2018 energy mix data, PHEV is a better choice in Texas from an environmental perspective. Our sensitivity analysis showed that the environmental performance of an EV greatly depends on the percentage of renewable or clean energy in the overall grid electricity production mix. Our study will pave the way to conduct similar analyses for other states of the U.S, especially for the regions dependent highly on non-renewable energy sources. The research findings will help decision-makers design effective policies for EV and PHEV adoption to achieve maximum environmental benefits.

Municipal solid waste generation is increasing rapidly globally. Increasing storage of waste in landfills means increased production of liquid landfill leachate. Leachate contains organic and inorganic pollutants which must be treated to reduce its potential impact on surrounding water supplies. To design landfill leachate treatment, its chemical composition must be known; however, the composition of leachate can vary widely depending on waste composition. Measuring leachate constituents can be expensive and time consuming, and is not possible for a landfill under construction. A global model able to forecast leachate quality parameters based on a landfill’s waste composition, ambient temperature, and rainfall rate is critically needed. This research represents a first step in development of such a model. Laboratory data on leachate biochemical and chemical oxygen demand (BOD, COD) was collected as functions of waste composition (food, paper, yard, textile), temperature (70, 85, 100 °F), and rainfall rates (2, 6, 12 mm/day), according to a statistical experimental design. Multivariate Adaptive Regression Splines (MARS) models were developed for BOD and COD, with adjusted- R 2 of 0.92 and 0.95, respectively. This exploratory research demonstrated the usefulness of MARS in capturing complex relationships among waste composition, temperature, and rainfall rate in order to forecast leachate quality parameters over time.

Co-pyrolysis of the seaweed Sargassum and polystyrene was investigated as a potential source of renewable energy. Sargassum is a brown macroalgae, posing a large disposal problem for beaches worldwide, and polystyrene is the plastic least recycled in the U.S. Although macroalgae bio-oil cannot be directly used as a result of a high oxygen content and low heating value, co-pyrolysis of macroalgae with low-oxygen-content waste polystyrene can enhance oil quality. Pyrolysis of pure Sargassum was conducted to determine the temperature producing the highest percent oil (600 °C). Co-pyrolysis of four different mixture ratios of Sargassum and polystyrene (5, 15, 25, and 33% by weight) was then conducted at 600 °C. Feedstocks and pyrolysis products (liquid oil and water, gas phase, and solid phase) were characterized using elemental analysis, thermogravimetric analysis, gas chromatography, surface area and adsorption isotherm analysis, and nuclear magnetic resonance. Co-pyrolysis with polystyrene improved the qua...

The overall goal was to determine an optimum pre-treatment condition for carbon nanotubes (CNTs) to facilitate air pollutant adsorption. Various combinations of heat and chemical pre-treatment were explored, and toluene was tested as an example hazardous air pollutant adsorbate. Specific objectives were (1) to characterize raw and pre-treated single-wall (SW) and multi-wall (MW) CNTs and compare their physical/chemical properties to commercially available granular activated carbon (GAC), (2) to determine the adsorption capacities for toluene onto pre-treated CNTs vs. GAC. CNTs were purified via heat-treatment at 400 °C in steam, followed by nitric acid treatment (3N, 5N, 11N, 16N) for 3-12 h to create openings to facilitate adsorption onto interior CNT sites. For SWNT, Raman spectroscopy showed that acid treatment removed impurities up to a point, but amorphous carbon reformed with 10h-6N acid treatment. Surface area of SWNTs with 3 h-3N acid treatment (1347 m(2)/g) was higher than the raw sample (1136 m(2)/g), and their toluene maximum adsorption capacity was comparable to GAC. When bed effluent reached 10% of inlet concentration (breakthrough indicating time for bed cleaning), SWNTs had adsorbed 240 mg/g of toluene, compared to 150 mg/g for GAC. Physical/chemical analyses showed no substantial difference for pre-treated vs. raw MWNTs.

As methane constitutes about 50% of landfill biogas, reduction of methane emissions from municipal solid waste (MSW) landfills results in climate change mitigation. As such, it is important for a landfill lifetime model to properly reflect the manner in which biogas is managed. The goal of this research is to compare landfill biogas management in a conventional landfill with a bioreactor landfill during a 100-year time horizon. This comparison concentrates on the greenhouse gas (GHG) emissions balances and electricity generation potential from recovered biogas using reciprocating internal combustion engines (RICE), which leads to avoiding GHG emissions due to fossil fuel displacement. The results estimated that the total amount of GHG emissions released to atmosphere, including fugitive methane emissions and the avoided effect of electrical energy production, was 668 and 803 kg carbon dioxide (CO2) equivalents (CO2E) per metric ton (t) of landfilled MSW for the conventional and the bioreactor landfill, respectively. This study underscores the importance of installing an aggressive gas collection system early for bioreactor landfills, and for investigating methods of improving gas collection efficiency during active landfilling.

Accurately estimating landfill methane emissions is important for quantifying a landfill's greenhouse gas emissions and power generation potential. Current models, including LandGEM and IPCC, often greatly simplify treatment of factors like rainfall and ambient temperature, which can substantially impact gas production. The newly developed Capturing Landfill Emissions for Energy Needs (CLEEN) model aims to improve landfill methane generation estimates, but still require inputs that are fairly easy to obtain: waste composition, annual rainfall, and ambient temperature. To develop the model, methane generation was measured from 27 laboratory scale landfill reactors, with varying waste compositions (ranging from 0% to 100%); average rainfall rates of 2, 6, and 12 mm/day; and temperatures of 20, 30, and 37°C, according to a statistical experimental design. Refuse components considered were the major biodegradable wastes, food, paper, yard/wood, and textile, as well as inert inorganic waste. Based on the data collected, a multiple linear regression equation (R(2)=0.75) was developed to predict first-order methane generation rate constant values k as functions of waste composition, annual rainfall, and temperature. Because, laboratory methane generation rates exceed field rates, a second scale-up regression equation for k was developed using actual gas-recovery data from 11 landfills in high-income countries with conventional operation. The Capturing Landfill Emissions for Energy Needs (CLEEN) model was developed by incorporating both regression equations into the first-order decay based model for estimating methane generation rates from landfills. CLEEN model values were compared to actual field data from 6 US landfills, and to estimates from LandGEM and IPCC. For 4 of the 6 cases, CLEEN model estimates were the closest to actual.

In 2015, fly ash utilization rates were 70% for China, 62% for India, and 50% for the US. This leaves substantial potential for increased utilization. This article summarizes available literature concerning physical and chemical and geotechnical properties of fly ash which affect its options for re-use. Fly ashes are broadly classified worldwide into two chemical types for their industrial applications, mostly in cement industries, namely class C and class F. Class C fly ash, with its higher levels of calcium oxide, generally has self-cementing properties. In terms of global fly ash composition, fly ash from India on average contains higher levels of silicon dioxide than that from the US and China. In terms of particle size, studies report that fly ash more often is poorly graded than well-graded; fly ash from India in particular tends to be poorly graded. Optimum moisture content (OMC) values for fly ashes vary from 11 to 53%, and maximum dry density values range from 1.01 to 1.78 g/cm3. Country-specific trends in terms of fly ash OMC and maximum dry density values are not readily apparent. Fly ash tends to be non-plastic, meaning it will not swell if used as a foundation material for structures. Reported fly ash shrinkage limits range from 38 to 65. Permeability of pure fly ash generally varies from 10−4 to 10-7 cm/sec, and angle of friction varies from 25° to 40°. Keywords: Fly ash, Geotechnical, Chemical, Physical, Coal combustion byproducts, Coal combustion residuals

Aquatic biomass, especially algae, is a promising renewable energy resource, owing to its high growth rate, high oil content, and lack of competition with land needed for food crops. Both micro- and macroalgae can be converted to liquid fuel through pyrolysis; however, the high oxygen content of the oil results in a low calorific value. Co-pyrolysis of biomass with synthetic polymers can improve oil quantity and quality: the polymers are petroleum products, contain less oxygen, and provide a comparable high heating value to conventional fossil fuels. Polystyrene is a particularly attractive synthetic polymer, because it has the lowest recycling rate of the major categories of plastic. This article provides background concerning thermal conversion of biomass/organic waste to energy, focusing on pyrolysis. Advantages of algae and polystyrene as pyrolysis feedstocks are discussed, and previous pyrolysis studies of macroalgae and polystyrene, as well as co-pyrolysis studies of biomass and plastics, are reviewed.

Approximately 1.5 billion tires are produced globally each year with 300 million in the USA, which will all eventually become waste tires. Waste tires are excellent candidates for recovery of energy, as well as solid, liquid, and gaseous by-products, via pyrolysis: made predominantly from the petroleum product rubber, they have a high heating value, as well as high volatile content and medium sulfur content. This paper reviews previous research on tire pyrolysis, and in particular identifies factors affecting yield and product composition. Properties of produced oil, gases, and char are summarized, and future research studies are recommended.

The traditional strategy for ground-level ozone control is to apply emission reductions across the board throughout certain time periods and locations. In this paper, we study various mixed integer linear programming (MILP) models that seek to select targeted control strategies for the Dallas Fort-Worth (DFW) region to reduce emissions, in order to achieve the State Implementation Plan (SIP) requirements with minimum cost. Statistics and optimization methods are used to determine a potential set of cost-effective control strategies for reducing ozone. These targeted control strategies are specified for different types of emission sources in various time periods and locations. Three MILP models, a static model, a sequential model, and a dynamic model, are studied in this research. These different MILP models allow decision makers to study how the targeted control strategies change under different circumstances. Meanwhile, two types of auxiliary variables are considered as supplemental control strategies in the optimization if the current set of control strategies is unable to reduce ozone to comply with the 8-h ozone standard. Results from the different models can provide decision makers with information concerning how the effectiveness of the control strategies varies with daily emission patterns and meteorology.

Production of natural gas from shale formations is bringing drilling and production operations to regions of the United States that have seen little or no similar activity in the past, which has generated considerable interest in potential environmental impacts. This study focused on the Barnett Shale Fort Worth Basin in Texas, which saw the number of gas-producing wells grow from 726 in 2001 to 15,870 in 2011. This study aimed to measure fence line concentrations of methane and hydrogen sulfide at natural gas production sites (wells, liquid storage tanks, and associated equipment) in the four core counties of the Barnett Shale (Denton, Johnson, Tarrant, and Wise). A mobile measurement survey was conducted in the vicinity of 4788 wells near 401 lease sites, representing 35% of gas production volume, 31% of wells, and 38% of condensate production volume in the four-county core area. Methane and hydrogen sulfide concentrations were measured using a Picarro G2204 cavity ring-down spectrometer (CRDS). Since the research team did not have access to lease site interiors, measurements were made by driving on roads on the exterior of the lease sites. Over 150 hr of data were collected from March to July 2012. During two sets of drive-by measurements, it was found that 66 sites (16.5%) had methane concentrations >3 parts per million (ppm) just beyond the fence line. Thirty-two lease sites (8.0%) had hydrogen sulfide concentrations >4.7 parts per billion (ppb) (odor recognition threshold) just beyond the fence line. Measured concentrations generally did not correlate well with site characteristics (natural gas production volume, number of wells, or condensate production). t tests showed that for two counties, methane concentrations for dry sites were higher than those for wet sites. Follow-up study is recommended to provide more information at sites identified with high levels of methane and hydrogen sulfide. Implications:Information regarding air emissions from shale gas production is important given the recent increase in number of wells in various regions in the United States. Methane, the primary natural gas constituent, is a greenhouse gas; hydrogen sulfide, which can be present in gas condensate, is an odor-causing compound. This study surveyed wells representing one-third of the natural gas production volume in the Texas Barnett Shale and identified the percent of sites that warrant further study due to their fence line methane and hydrogen sulfide concentrations.

Information regarding air emissions from shale gas extraction and production is critically important given production is occurring in highly urbanized areas across the United States. Objectives of this exploratory study were to collect ambient air samples in residential areas within 61 m (200 feet) of shale gas extraction/production and determine whether a "fingerprint" of chemicals can be associated with shale gas activity. Statistical analyses correlating fingerprint chemicals with methane, equipment, and processes of extraction/production were performed. Ambient air sampling in residential areas of shale gas extraction and production was conducted at six counties in the Dallas/Fort Worth (DFW) Metroplex from 2008 to 2010. The 39 locations tested were identified by clients that requested monitoring. Seven sites were sampled on 2 days (typically months later in another season), and two sites were sampled on 3 days, resulting in 50 sets of monitoring data. Twenty-four-hour passive samples were collected using summa canisters. Gas chromatography/mass spectrometer analysis was used to identify organic compounds present. Methane was present in concentrations above laboratory detection limits in 49 out of 50 sampling data sets. Most of the areas investigated had atmospheric methane concentrations considerably higher than reported urban background concentrations (1.8-2.0 ppm(v)). Other chemical constituents were found to be correlated with presence of methane. A principal components analysis (PCA) identified multivariate patterns of concentrations that potentially constitute signatures of emissions from different phases of operation at natural gas sites. The first factor identified through the PCA proved most informative. Extreme negative values were strongly and statistically associated with the presence of compressors at sample sites. The seven chemicals strongly associated with this factor (o-xylene, ethylbenzene, 1,2,4-trimethylbenzene, m- and p-xylene, 1,3,5-trimethylbenzene, toluene, and benzene) thus constitute a potential fingerprint of emissions associated with compression.Information regarding air emissions from shale gas development and production is critically important given production is now occurring in highly urbanized areas across the United States. Methane, the primary shale gas constituent, contributes substantially to climate change; other natural gas constituents are known to have adverse health effects. This study goes beyond previous Barnett Shale field studies by encompassing a wider variety of production equipment (wells, tanks, compressors, and separators) and a wider geographical region. The principal components analysis, unique to this study, provides valuable information regarding the ability to anticipate associated shale gas chemical constituents.

Surface coating facilities are major sources of volatile organic compounds (VOCs) in urban areas. These VOCs can contribute to ground-level ozone formation, and many are hazardous air pollutants (HAPs), including xylene, ethylbenzene, and toluene. This project was conducted in order to provide information for updating the Texas Commission on Environmental Quality (TCEQ), USA, permit by rule for Surface Coating Facilities. Project objectives were: 1) To develop a database of information regarding surface coating facilities in Texas; 2) To estimate maximum emission rates for various VOC species from surface coating facilities in Texas; 3) To conduct dispersion modeling to estimate off-site impacts from surface coating facilities. The database was developed using 286 TCEQ permit files authorizing surface coating facilities in Texas during 2006 and 2007. The database was designed to include information important for estimating emission rates, and for using as inputs to the dispersion model. Hourly and annual emissions of volatile organic compounds (VOCs), particulate matter (PM), and exempt solvents (ES) were calculated for each permitted entity/ company in the database, according to equations given by TCEQ. Dispersion modeling was then conducted for 3 facility configurations (worst-case stack height, good practice stack height, and fugitive emissions), for urban and rural dispersion parameters, for 8-hour and 24-hour operating scenarios, and for 1-hour, 24-hour, and annual averaging times, for a total of 36 scenarios. The highest modeled concentrations were for the worst-case stack height, rural dispersion parameters, 24-hour operation scenario, and 1-hour averaging time. 108 specific chemical species, which are components of surface coatings, were identified as candidates for further health impacts review.

Biodiesel has generated increased interest recently as an alternative to petroleum-derived diesel. Due to its high oxygen content, biodiesel typically burns more completely than petroleum diesel, and thus has lower emissions of hydrocarbons (HC), carbon monoxide (CO), and particulate matter (PM). However, biodiesel may increase or decrease nitrogen oxide (NOx) and carbon dioxide (CO2) emissions, depending on biodiesel feedstock, engine type, and test cycle. The purpose of this study was to compare emissions from 20% blends of biodiesel made from 4 feedstocks (soybean oil, canola oil, waste cooking oil, and animal fat) with emissions from ultra low sulfur diesel (ULSD). Emissions of NOx and CO2 were made under real-world driving conditions using a Horiba On-Board Measurement System OBS-1300 on a highway route and arterial route; emissions of NOx, CO2, HC, CO, and PM were measured in a controlled setting using a chassis dynamometer with Urban Dynamometer Drive Schedule. Dynamometer test results showed statistically significant lower emissions of HC, CO, and PM from all B20 blends compared to ULSD. For CO2, both on-road testing (arterial, highway, and idling) and dynamometer testing showed no statistically significant difference in emissions among the B20 blends and ULSD. For NOx, dynamometer testing showed only B20 from soybean oil to have statistically significant higher emissions. This is generally consistent with the on-road testing, which showed no statistically significant difference in NOx emissions between ULSD and the B20 blends.

The objective of this research was development of a statistical model for estimating vehicle tailpipe emissions of carbon dioxide (CO2). Forty hours of second-by-second emissions data (144,000 data points) were collected using an On-Board emissions measurement System (Horiba OBS-1300) installed in a 2007 Dodge Charger car. Data were collected for two roadway types, arterial and highway, around Arlington, Texas, and two different time periods, off peak and peak (both a.m. and p.m.). Multiple linear regression and SAS software were used to build emission models from the data, using predictor variables of velocity, acceleration and an interaction term. The arterial model explained 61% of the variability in the emissions; the highway model explained 27%. The arterial model in particular represents a reasonably good compromise between accuracy and ease of use. The arterial model could be coupled with velocity and acceleration profiles obtained from a micro-scale traffic simulation model, such as CORSIM, or from field data from an instrumented vehicle, to estimate percent emission reductions associated with local changes in traffic system operation or management.

The global demand for water transmission and service pipelines is expected to more than double between 2012 and 2022. This study compared the carbon footprint of the two most common materials used for large-diameter water transmission pipelines, steel pipe (SP) and prestressed concrete cylinder pipe (PCCP). A planned water transmission pipeline in Texas was used as a case study. Four life-cycle phases for each material were considered: material production and pipeline fabrication, pipe transportation to the job site, pipe installation in the trench, and operation of the pipeline. In each phase, the energy consumed and the CO2-equivalent emissions were quantified. It was found that pipe manufacturing consumed a large amount of energy, and thus contributed more than 90% of life cycle carbon emissions for both kinds of pipe. Steel pipe had 64% larger CO2-eq emissions from manufacturing compared to PCCP. For the transportation phase, PCCP consumed more fuel due to its heavy weight, and therefore had larger CO2-eq emissions. Fuel consumption by construction equipment for installation of pipe was found to be similar for steel pipe and PCCP. Overall, steel had a 32% larger footprint due to greater energy used during manufacturing. Implications: This study compared the carbon footprint of two large-diameter water transmission pipeline materials, steel and prestressed concrete cylinder, considering four life-cycle phases for each. The study provides information that project managers can incorporate into their decision-making process concerning pipeline materials. It also provides information concerning the most important phases of the pipeline life cycle to target for emission reductions.

To increase U.S. petroleum energy independence, the University of Texas at Arlington (UT Arlington) has developed a direct coal liquefaction process which uses a hydrogenated solvent and a proprietary catalyst to convert lignite coal to crude oil. This sweet crude can be refined to form JP-8 military jet fuel, as well as other end products like gasoline and diesel. This paper presents an analysis of air pollutants resulting from using UT Arlington's liquefaction process to produce crude and then JP-8, compared with 2 alternative processes: conventional crude extraction and refining (CCER), and the Fischer-Tropsch process. For each of the 3 processes, air pollutant emissions through production of JP-8 fuel were considered, including emissions from upstream extraction/ production, transportation, and conversion/refining. Air pollutants from the direct liquefaction process were measured using a LandTEC GEM2000 Plus, Draeger color detector tubes, OhioLumex RA-915 Light Hg Analyzer, and SRI 8610 gas chromatograph with thermal conductivity detector. According to the screening analysis presented here, producing jet fuel from UT Arlington crude results in lower levels of pollutants compared to international conventional crude extraction/refining. Compared to US domestic CCER, the UTA process emits lower levels of CO2-e, NO(x), and Hg, and higher levels of CO and SO2. Emissions from the UT Arlington process for producing JP-8 are estimated to be lower than for the Fischer-Tropsch process for all pollutants, with the exception of CO2-e, which were high for the UT Arlington process due to nitrous oxide emissions from crude refining. When comparing emissions from conventional lignite combustion to produce electricity, versus UT Arlington coal liquefaction to make JP-8 and subsequent JP-8 transport, emissions from the UT Arlington process are estimated to be lower for all air pollutants, per MJ of power delivered to the end user.The United States currently imports two-thirds of its crude oil, leaving its transportation system especially vulnerable to disruptions in international crude supplies. At current use rates, U.S. coal reserves (262 billion short tons, including 23 billion short tons lignite) would last 236 years. Accordingly, the University of Texas at Arlington (UT Arlington) has developed a process that converts lignite to crude oil, at about half the cost of regular crude. According to the screening analysis presented here, producing jet fuel from UT Arlington crude generates lower levels of pollutants compared to international conventional crude extraction/refining (CCER).

To increase U.S. petroleum energy-independence, the University of Texas at Arlington (UT Arlington) has developed a coal liquefaction process that uses a hydrogenated solvent and a proprietary catalyst to convert lignite coal to crude oil. This paper reports on part of the environmental evaluation of the liquefaction process: the evaluation of the solid residual from liquefying the coal, called inertinite, as a potential adsorbent for air and water purification. Inertinite samples derived from Arkansas and Texas lignite coals were used as test samples. In the activated carbon creation process, inertinite samples were heated in a tube furnace (Lindberg, Type 55035, Arlington, UT) at temperatures ranging between 300 and 850 degrees C for time spans of 60, 90, and 120 min, using steam and carbon dioxide as oxidizing gases. Activated inertinite samples were then characterized by ultra-high-purity nitrogen adsorption isotherms at 77 K using a high-speed surface area and pore size analyzer (Quantachrome, Nova 2200e, Kingsville, TX). Surface area and total pore volume were determined using the Brunauer Emmet, and Teller method, for the inertinite samples, as well as for four commercially available activated carbons (gas-phase adsorbents Calgon Fluepac-B and BPL 4 x 6; liquid-phase adsorbents Filtrasorb 200 and Carbsorb 30). In addition, adsorption isotherms were developed for inertinite and the two commercially available gas-phase carbons, using methyl ethyl ketone (MEK) as an example compound. Adsorption capacity was measured gravimetrically with a symmetric vapor sorption analyzer (VTI, Inc., Model SGA-100, Kingsville, TX). Also, liquid-phase adsorption experiments were conducted using methyl orange as an example organic compound. The study showed that using inertinite from coal can be beneficially reused as an adsorbent for air or water pollution control, although its surface area and adsorption capacity are not as high as those for commercially available activated carbons.The United States currently imports two-thirds of its crude oil, leaving its transportation system especially vulnerable to disruptions in international crude supplies. UT Arlington has developed a liquefaction process that converts coal, abundant in the United States, to crude oil. This work demonstrated that the undissolvable solid coal residual from the liquefaction process, called inertinite, can be converted to an activated carbon adsorbent. Although its surface area and adsorption capacity are not as high as those for commercially available carbons, the inertinite source material would be available at no cost, and its beneficial reuse would avoid the need for disposal.

This paper presents a decision-making framework (DMF) for selecting ozone control strategies based on reductions of precursor emissions that are targeted by time and location. Conventional across-the-board reductions are uniform throughout the region and throughout the day. The DMF is comprised of four phases: (1) Initialization, (2) Experimental Design and Data Mining, (3) Metamodeling, and (4) Optimization. This paper details the first three and presents an example for selecting strategies in the optimization phase. Specifically, to enable an efficient optimization phase, metamodels for maximum 8-h averaged ozone are employed to represent the output from an advanced photochemical model, such as CAMx. The process for each phase is presented for a Dallas Fort Worth (DFW) 2009 future emission scenario, based on a 10-day meteorological episode from August 13–22, 1999. Over 600 emission variables were identified in three source categories viz. point, area (includes non-road) and line (on-road). The DFW application demonstrates how control measures can be efficiently explored in a targeted manner instead of using the conventional “trial and error” approach.

Selective catalytic reduction (SCR) is an emissions control technique that primarily reduces harmful emissions of oxides of nitrogen (NOx). To maintain SCR performance, catalyst layers maybe added, removed, or replaced to improve NOx reduction efficiency. To make these changes, power plants must be temporarily shut down, and SCR maintenance during scheduled power plant outages can be very expensive. Consequently, developing a fleet-wide SCR management plans that are both efficient at reducing NOx and limiting operating costs would be extremely desirable. We propose an SCR management framework that finds an optimal SCR management plan that minimizes NOx emissions using integer programming. The SCR management tool consists of two main modules—the SCR schedule generation module and the SCR optimization module. Furthermore, the SCR management framework addresses decision making from the fleet-wide perspective as well as a single plant as opposed to only a single plant, which is currently commercially available. We demonstrate the effectiveness of the tool and provide a tradeoff between NOx reduction and operating cost using Pareto optimal efficient frontiers.

In this paper, an intelligent decision-making framework (DMF) is developed to help decision makers identify cost-effective ozone control policies. High concentrations of ozone at the ground level continue to be a serious problem in numerous U.S. cities. Our DMF searches for dynamic and targeted control policies that require a lower total reduction of emissions than current control strategies based on the “trial and error” approach typically employed by state government decision makers. Our DMF utilizes a rigorous stochastic dynamic programming (SDP) formulation and incorporates an atmospheric chemistry module to model how ozone concentrations change over time. Within the atmospheric chemistry module, methods from design and analysis of computer experiments are employed to create SDP state transition equation metamodels, and critical dimensionality reduction is conducted to reduce the state-space dimension in solving our SDP problem. Results are presented from a prototype DMF for the Atlanta metropolitan region.

Over the past few decades, there has been growing emphasis on sustainable development and a growing need to train students to think sustainably in preparation for their careers as practicing engineers. Thinking sustainably requires the consideration of not only environmental impacts but also societal and economic impacts. Thus, teaching future engineers to think sustainably requires a multifaceted, multipronged approach. To that end, a team of faculty from the Departments of Civil, Industrial, and Mechanical Engineering at the University of Texas at Arlington acquired funding from the National Science Foundation to implement a project entitled “Engineering Sustainable Engineers.” The project was designed to infuse undergraduate curricula in the three departments with sustainability, which was augmented by incorporating sustainability emphasis into other aspects of the undergraduate experience. Key program elements were (1) learning modules developed for courses across all levels of matriculation w...

According to EPA estimates, U.S. transportation sources emit 56% of nitrogen oxides, 89% of carbon monoxide, and 45% of volatile organic compounds. Air pollution from mobile sources has increased in recent years, due to increased numbers of vehicles on the road and miles traveled per vehicle. Historically, however, air pollution control courses have focused on stationary sources like utilities; mobile sources have been addressed only briefly. A number of universities are now recognizing this and are offering entire classes in Transportation and Air Quality/Environment. Objectives of this study were: (1) to conduct a survey of Transportation and Air Quality courses offered nationwide, and gather information concerning topics covered and perspectives; (2) to provide information to educators wishing to introduce a Transportation and Air Quality course. The survey was conducted using information from the Association of Environmental Science and Engineering Professors, internet searches, and e-mails to faculty...

The two primary factors influencing ambient air pollutant concentrations are emission rate and dispersion rate. Gaussian dispersion modeling studies for odors, and often other air pollutants, vary dispersion rates using hourly meteorological data. However, emission rates are typically held constant, based on one measured value. Using constant emission rates can be especially inaccurate for open liquid area sources, like wastewater treatment plant units, which have greater emissions during warmer weather, when volatilization and biological activity increase. If emission rates for a wastewater odor study are measured on a cooler day and input directly into a dispersion model as constant values, odor impact will likely be underestimated. Unfortunately, because of project schedules, not all emissions sampling from open liquid area sources can be conducted under worst-case summertime conditions. To address this problem, this paper presents a method of varying emission rates based on temperature and time of the day to predict worst-case emissions. Emissions are varied as a linear function of temperature, according to Henry's law, and a tenth order polynomial function of time. Equation coefficients are developed for a specific area source using concentration and temperature measurements, captured over a multiday period using a data-logging monitor. As a test case, time/temperature concentration correlation coefficients were estimated from field measurements of hydrogen sulfide (H2S) at the Rowlett Creek Wastewater Treatment Plant in Garland, TX. The correlations were then used to scale a flux chamber emission rate measurement according to hourly readings of time and temperature, to create an hourly emission rate file for input to the dispersion model ISCST3. ISCST3 was then used to predict hourly atmospheric concentrations of H2S. With emission rates varying hourly, ISCST3 predicted 384 acres of odor impact, compared with 103 acres for constant emissions. Because field sampling had been conducted on relatively cool days (85-90 degrees F), the constant emission rate underestimated odor impact significantly (by 73%).

Public education campaigns, to be successful, must repeat simple, consistent messages over time, using various sources and media. During the 2000, 2001, and 2002 ozone seasons, the North Central Texas Council of Governments (NCTCOG) employed a four-pronged, multimedia approach to educate the public about air quality in the Dallas/Fort Worth (DFW) region. The four-pronged approach included several varied information sources:• The new Air Pollution Watch/Warning system based on public health and designed using standard meteorological terminology with notices delivered via e-mail, over the radio, during TV weather forecasts, and on electronic road signs.• A revamped Web page, including information about current air quality, ozone exceedances, clean air public meetings, and how to “Do Your Share for Cleaner Air”.• A PowerPoint presentation used to explain the basics of ozone air pollution, the new Air Pollution Watch/Warning system, and the new Dallas/Fort Worth Clean Air Plan to a variety of constituencies, including the media, scientific/technical/academic groups, elected officials, and community/civic organizations.• Newsletter updates, published in the Environmental Resources Department's InsidER (with a circulation of around 1500), to educate and keep the public up-to-date about various air quality issues.This paper provides details about the four-pronged approach, and how it incorporates principles of successful public education campaigns. Keywords: Air quality, Dallas, Education, Fort Worth, Ozone, Texas

In designing a photocatalytic oxidation (PCO) system for a given air pollution source, destruction rates for volatile organic compounds (VOCs) are required. The objective of this research was to develop a systematic method of predicting PCO rate constants by correlating rate constants with physical-chemical characteristics of compounds. Accordingly, reaction rate constants were determined for destruction of volatile organics over a titanium dioxide (TiO2 ) catalyst in a continuous mixed-batch reactor. It was found that PCO rate constants for alkanes and alkenes vary linearly with gas-phase ionization potential (IP) and with gas-phase hydroxyl radical reaction rate constant. The correlations allow rates of destruction of compounds not tested in this research to be predicted based on physical-chemical characteristics.

According to the U.S. Environmental Protection Agency (EPA), in 2010 mobile sources in the U.S. contributed 58% of carbon monoxide (CO), 56% of nitrogen oxide (NOx), and 33% of Volatile Organic Compounds (VOCs). Onroad sources also emit a variety of air toxics, including benzene, toluene, and xylenes. The case study presented here determines a safe roadway buffer width to protect human health from nitrogen dioxide (NO2) exposure along an arterial in Grand Prairie, Texas. NO2 health effects include eye, nose, throat, and lung irritation; cough; shortness of breath; tiredness and nausea. In the Dallas Fort Worth region, where Grand Prairie is located, on-road vehicles contribute about half of NOx emissions. Vehicle NOx emission rates along Great Southwest Parkway were measured using a Horiba 1300 OBS onboard emission measurement system, to determine a maximum g/mile emission factor for the corridor. Hourly DFW meteorological data for a 5-year period was processed using CAL3QHCR to determine the 10 worst-case hourly meteorological combinations. The maximum emission factor and worst-case meteorological conditions were input into the line source dispersion model CALRoads View to determine worst-case NO2 concentrations at 5- m intervals away from the roadway. CALRoads View output was post-processed in Arc View GIS to plot concentrations at receptor locations. Worst-case concentrations were compared to the 1-hour NO2 National Ambient Air Quality Standard (100 ppb). For the current Great Southwest traffic volume, it was found that the standard would not be exceeded. Additional CALRoads View runs were conducted to determine how much the traffic volume could increase, and still avoid exceedances outside a 20-foot buffer width, which is a common setback distance in residential areas. It was determined that the traffic volume could increase by a factor of 10 and still protect human health from NO2 impacts, using a 20-foot buffer.

As global population increases and developing countries industrialize, energy demand around the world is increasing markedly. World energy consumption is expected to increase by 50% to 180,000 GWh/year by 2020 (Fernando et al., 2006), due primarily to increases in demand from rapidly growing Asian countries such as China and India (Khanal, 2008). According to the Intergovernmental Panel on Climate Change (IPCC, 2007), fossil fuel combustion already contributes 57% of emissions that cause global warming. Thus, to address future energy needs sustainably, renewable sources of energy must be developed as alternatives to fossil fuels. To aid in developing such renewable energy alternatives, environmental scientists and engineers should consider anaerobic processes for waste treatment as alternatives to aerobic processes. When aerobic processes are used for waste treatment, the low energy compounds carbon dioxide and water are formed; much energy is lost to air – about 20 times as much as with an anaerobic process (Deublein and Steinhauser, 2008). Anaerobic processes produce products of high energy like methane. Methane can be captured and burned as an energy source, and used to power gas-burning appliances or internal combustion engines, or to generate electricity. Anaerobic processes have been applied for decades in developed countries for wastewater treatment plant sludge stabilization. In recent years, considerable interest has developed in use of anaerobic treatment for a variety of other applications, due to the potential to generate renewable energy. Methane from anaerobic processes is being increasingly utilized as an alternative energy source in developed countries, via large projects that extract methane from landfills or wastewater treatment plants. Smaller plants, on the scale of an individual household or village, can also be a particularly important energy source in rural sectors of developing countries; transportation costs in these locations may limit use of fossil fuels, and lack of cheap and adequate energy hampers rural development. When generated from biomass, especially at a small scale, methane is often called biogas (FAO, 1984; Deublein and Steinhauser, 2008). In addition to providing a renewable source of energy, anaerobic processes provide some of the simplest and most practical methods for minimizing public health hazards from human and animal wastes – pathogens are destroyed or greatly reduced. Anaerobic processes have been proven for treatment of a variety of organic wastes: solid wastes at landfills, industrial wastewater, human excrement and sludges at wastewater treatment plants, human excrement in rural areas, animal manure, agricultural wastes, and forestry wastes. The

Titanium dioxide (TiO(2)) is a preferred catalyst for photocatalytic oxidation of many air pollutants. In an effort to enhance its photocatalytic activity, TiO(2) was modified by pulsed plasma treatment. In this work, TiO(2) nanoparticles, coated on a glass plate, were treated with a plasma discharge of hexafluoropropylene oxide (HFPO) gas. By appropriate adjustment of discharge conditions, it was discovered that the TiO(2) particles can be either directly fluorinated (Ti-F) or coated with thin perfluorocarbon films (C-F). Specifically, under relatively high power input, the plasma deposition process favored direct surface fluorination. The extent of Ti-F formation increased with increasing power input. In contrast, at lower average power inputs, perfluorocarbon films are deposited on the surface of the TiO(2) particles. The plasma surface modified TiO(2) nanoparticles were subsequently employed as catalysts in the photocatalytic oxidation of m-xylene in air, as carried out inside a batch reactor with closed loop constant gas circulation. Both types of modified TiO(2) were significantly more catalytically active than that of the unmodified particles. For example, the rate constant of m-xylene degradation was increased from 0.012 min(-1) with untreated TiO(2) to 0.074 min(-1) with fluorinated TiO(2). Although it is not possible to provide unequivocal reasons for this increased photocatalytic activity, it is noted that the plasma surface treatment converted the TiO(2) from hydrophilic to highly hydrophobic, which would provide more facile catalyst adsorption of the xylene from the flowing air. Also, based on literature reports, the use of fluorinated TiO(2) reduces electron-hole recombination rates, thus increasing the photocatalytic activity.

Propylene and butylene are highly reactive volatile organic compounds (HRVOCs) in terms of ground-level ozone formation. This study examined the effectiveness of biofiltration in removing propylene and butylene as separate compounds. Specific objectives were (1) to measure maximum removal efficiencies for propylene and butylene and the corresponding microbial acclimation times, which will be useful in the design of future biofilters for removal of these compounds; (2) to compare removal efficiencies of propylene and butylene for different ratios of compost/hard wood-chip media; and (3) to identify the microorganisms responsible for propylene and butylene degradation. Two laboratory-scale polyvinyl chloride biofilter columns were filled with 28 in. of biofilter media (compost/wood-chip mixtures of 80:20 and 50:50 ratios). Close to 100% removal efficiency was obtained for propylene for inlet concentrations ranging from 2.9 x 10(4) to 6.3 x 10(4) parts per million (ppm) (232-602 g/m3-hr) and for butylene for inlet concentrations ranging from 91 to 643 ppm (1.7-13.6 g/m3-hr). The microbial acclimation period to attain 100% removal efficiency was 12-13 weeks for both compounds. The lack of similar microbial species in the fresh and used media likely accounts for the long acclimation time required. Both ratios of compost/wood chips (80:20 and 50:50) gave similar results. During the testing, media pH increased slightly from 7.1 to 7.5-7.7. None of the species in the used media that treated butylene were the same as those in the used media that treated propylene, indicating that different microbes are adept at degrading the two compounds.

The poster will include results from first semester implementation of the sustainability learning modules, the biodiesel refinery multidisciplinary senior design project, and Quality Sustainable Engineering Internship Checklist.

Statistical analyses of time-series or spatial data have been widely used to investigate the behavior of ambient air pollutants. Because air pollution data are generally collected in a wide area of interest over a relatively long period, such analyses should take into account both spatial and temporal characteristics. The objective of this study is 2-fold: (1) to identify an efficient way to characterize the spatial variations of fine particulate matter (PM2.5) concentrations based solely upon their temporal patterns, and (2) to analyze the temporal and seasonal patterns of PM2.5 concentrations in spatially homogenous regions. This study used 24-hr average PM2.5 concentrations measured every third day during a period between 2001 and 2005 at 522 monitoring sites in the continental United States. A k-means clustering algorithm using the correlation distance was used to investigate the similarity in patterns between temporal profiles observed at the monitoring sites. A k-means clustering analysis produced six clusters of sites with distinct temporal patterns that were able to identify and characterize spatially homogeneous regions of the United States. The study also presents a rotated principal component analysis (RPCA) that has been used for characterizing spatial patterns of air pollution and discusses the difference between the clustering algorithm and RPCA.

Two competing meteorological factors influence atmospheric concentrations of pollutants from open liquid area sources such as wastewater treatment plant units: temperature and stability. High temperatures in summer produce greater emissions from liquid area sources because of increased compound volatility; however, these emissions tend to disperse more readily because of frequent occurrence of unstable conditions. An opposite scenario occurs in winter, with lesser emissions due to lower temperatures, but also frequently less dispersion, due to stable atmospheric conditions. The primary objective of this modeling study was thus to determine whether higher atmospheric concentrations from open liquid area sources occur more frequently in summer, when emissions are greater but so is dispersion, or in winter, when emissions are lesser but so is dispersion. The study utilized a rectangular clarifier emitting hydrogen sulfide as a sample open liquid area source. Dispersion modeling runs were conducted using ISCST3 and AERMOD, encompassing 5 yr of hourly meteorological data divided by season. Emission rates were varied hourly on the basis of a curve-fit developed from previously collected field data. Model output for each season was used to determine (1) maximum 2-min average concentrations, (2) the number of odor events (2-min average concentrations greater than odor detection thresholds), and (3) areas of impact. On the basis of these 3 types of output, it was found that the worst-case odors were associated with summer, considering impacts of meteorology upon both emissions and dispersion. Not accounting for the impact of meteorology on emissions (using a constant worst-case emission rate) caused concentrations to be overpredicted compared with a variable emission rate case. The highest concentrations occurred during stability classes D, E, and F, as anticipated. A comparison of ISCST3 and AERMOD found that for the area source modeled, ISCST3 predicted higher concentrations and more odor events for all seasons.

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S), methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor control processes is activated carbon adsorption; however, very few studies have been conducted on COS adsorption. COS is not only an odor causing compound but is also listed in the Clean Air Act as a hazardous air pollutant. Objectives of this study were to determine the following: (1) the adsorption capacity of 3 different carbons for COS removal; (2) the impact of relative humidity (RH) on COS adsorption; (3) the extent of competitive adsorption of COS in the presence of H2S; and (4) whether ammonia injection would increase COS adsorption capacity. Vapor phase react (VPR; reactivated), BPL (bituminous coal-based), and Centaur (physically modified to enhance H2S adsorption) carbons manufactured by Calgon Carbon Corp. were tested in three laboratory-scale columns, 6 in. in depth and 1 in. in diameter. Inlet COS concentrations varied from 35 to 49 ppmv (86-120 mg/m3). RHs of 17%, 30%, 50%, and 90% were tested. For competitive adsorption studies, H2S was tested at 60 ppmv, with COS at 30 ppmv. COS, RH, H2S, and ammonia concentrations were measured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corp. 1000 series portable analyzer, and Drager Accuro ammonia sensor, respectively. It was found that the adsorption capacity of Centaur carbon for COS was higher than the other two carbons, regardless of RH. As humidity increased, the percentage of decrease in adsorption capacity of Centaur carbon, however, was greater than the other two carbons. The carbon adsorption capacity for COS decreased in proportion to the percentage of H2S in the gas stream. More adsorption sites appear to be available to H2S, a smaller molecule. Ammonia, which has been found to increase H2S adsorption capacity, did not increase the capacity for COS.