Criteria Air Pollutant Emissions Research Articles

Climate-based policies may increase life-cycle social costs of vehicle fleet operation

Sustainability guidelines and regulations in the United States often focus exclusively on carbon or petroleum reductions. Though some of these policies have resulted in substantial progress toward their goals, the effects of these efforts on other social and environmental externalities are often ignored. In this study, we examine the life-cycle air pollutant emissions for alternative fuel and vehicle purchase scenarios at a military installation near a typical urban area in the United States (U.S.). We find that scenarios which minimize petroleum use or greenhouse gas emissions do not concomitantly minimize criteria air pollutant emissions. We also employ social cost methodologies to quantify economic externalities due to climate change and health-related air pollutant impacts. Accounting for the social costs of climate change and air pollution from vehicle use reveals that criteria air pollutants may have a greater total impact than greenhouse gas emissions in locations similar to the urban area examined in this study. Use of first-generation biofuels, particularly corn grain ethanol, may reduce net petroleum use at the cost of increased total health impacts. More comprehensive policies may be needed to ensure that sustainability policies result in a net benefit to society.

Life-Cycle Assessment of Biodiesel Produced from Grease Trap Waste.

Grease trap waste (GTW) is a low-quality waste material with variable lipid content that is an untapped resource for producing biodiesel. Compared to conventional biodiesel feedstocks, GTW requires different and additional processing steps for biodiesel production due to its heterogeneous composition, high acidity, and high sulfur content. Life-cycle assessment (LCA) is used to quantify greenhouse gas emissions, fossil energy demand, and criteria air pollutant emissions for the GTW-biodiesel process, in which the sensitivity to lipid concentration in GTW is analyzed using Monte Carlo simulation. The life-cycle environmental performance of GTW-biodiesel is compared to that of current GTW disposal, the soybean-biodiesel process, and low-sulfur diesel (LSD). The disposal of the water and solid wastes produced from separating lipids from GTW has a high contribution to the environmental impacts; however, the impacts of these processed wastes are part of the current disposal practice for GTW and could be excluded with consequential LCA system boundaries. At lipid concentrations greater than 10%, most of the environmental metrics studied are lower than those of LSD and comparable to soybean biodiesel.

Comparing the sustainability of U.S. electricity options through multi-criteria decision analysis

Sustainable energy decision-making requires comparing energy options across a wide range of economic, environmental, social and technical implications. However, such comparisons based on quantitative data are currently limited at the national level. This is the first comparison of 13 currently operational renewable and non-renewable options for new US electricity generation using multi-criteria decision analysis with quantitative input values (minimum, nominal, and maximum) for 8 sustainability criteria (levelized cost of energy, life cycle greenhouse gas and criteria air pollutant emissions, land and water use, accident-related fatalities, jobs, and annual capacity factor) and 10 representative decision-maker preference scenarios. Results across several preference scenarios indicate that biopower and geothermal (flash and binary) currently score highest in sustainability for the US. Other renewable energy technologies generally offer substantial sustainability improvements over fossil fuel or nuclear technologies, and nuclear is preferable to fossil fuels in most scenarios. The relatively low ranking of natural gas combined cycle in most preference scenarios should encourage caution in adopting NGCC as a “bridge” to renewables. Although NGCC ranks high under economic and technical preference scenarios, renewables actually rank higher in both scenarios (hydro – economic; geothermal and biopower – technical).

Solar Photovoltaic Development in Australia—A Life Cycle Sustainability Assessment Study

Australia possesses the highest average solar radiation of any continent in the world, but solar energy in total contributes less than 1% to Australia’s primary energy consumption. This study intends to assess whether solar photovoltaic (PV) is really a sustainable option for Australia’s energy transition on the project level. A life cycle sustainability assessment (LCSA) was conducted on a 1.2 MW flat-roof mounted PV solar array called UQ Solar, and the results suggested UQ Solar performed well in environmental aspects, except for emissions of several criteria air pollutants. It was economically feasible only with the grant provided by the Queensland government and the levelized cost of electricity (LCOE) was more or less the same as the LCOE of offset electricity. However, its social performance was not as good as expected. Large-scale PV installations can be sustainable in Australia on several conditions. PV manufacturers should be more responsible for reducing the use of hazardous materials; end-of-life treatment should be taken good care of; government should truly support the deployment of large-scale PV installation by providing more incentives and infrastructures; substantial subsidies for fossil fuel power stations should phase out; more awareness and training activities should be organized to promote social acceptance.

Influence of Gasoline Aromatic Content on Air Pollutant Emissions from Four-Stroke Motorcycles

A new four-stroke carburetor motorcycle engine without any engine adjustments was used to study the impact of fuel aromatic content on exhaust emissions of criteria air pollutants (CO, THC, and NOx). Three aromatic fuels were tested, containing 15, 25, and 50% (vol) aromatics mixed with gasoline. A commercial unleaded gasoline was also tested as a reference case (RF). The experimental data indicated that a lower aromatic content (25 and 15 vol%) in gasoline reduced the amounts of THC and NOx by more than 10% compared to the reference fuel (aromatic content 30 vol%). CO emissions, on the other hand, did not appear to be related to the aromatic content of gasoline. The excess air ratio (λ) values for the aromatic test fuels were lower than 1.0, i.e., under fuel-rich conditions, and CO emissions increased due to lack of oxygen. In contrast, high NOx emissions appeared in a near stoichiometric air-fuel ratio, and decreased as the fuel mixture approached lean or rich conditions. The results also showed that decreasing the aromatic content from 50 to 25 and 15 vol% in gasoline may result in a reduction of benzene emissions from the motorcycles without a catalyst converter. This study shows that decreasing the aromatic content in gasoline may reduce the emissions of THC, NOx, and benzene, but not CO, from four-stroke carburetor motorcycles.

An examination of historical air pollutant emissions from us petroleum refineries

Criteria and hazardous air pollutant emissions from petroleum refineries in the US have decreased over the last 20 yr despite increasing crude density, changes in sulfur concentrations, increasingly stringent product specifications, and overall increase of refinery production of major fuel types. Refinery emissions of criteria air pollutants have decreased as much as 80% from 1990 to 2010. Emissions of hazardous air pollutants and their associated toxicity hazard potential have decreased nearly 70%. Furthermore, the emissions are not correlated with changes in crude oil sulfur content or density. Trends in annual criteria and hazardous air pollutant emissions and in crude oil density and sulfur content are compared to assess potential relationships between crude quality and refinery emissions. The potential toxicity of hazardous air pollutant emissions is evaluated using USEPA‐derived toxicity criteria and then trended to demonstrate the overall reduction in toxicity hazard potential that has occurred. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 425‐432, 2013

Comparing Delay Minimization and Emissions Minimization in the Network Design Problem

Abstract: Traditionally, transportation road networks are designed for minimal congestion. Unfortunately, such approaches do not guarantee minimal vehicle emissions. To fill this apparent gap in network design research, an emissions network design problem and solution method is proposed in this article for the purposes of comparing to the traditional network design results. Three air pollutants are considered on two road networks. The model is formulated as a bi‐level optimization problem and a solution is approximated using a genetic algorithm. The influence of demand uncertainty is also incorporated into the model. Designing for minimal congestion tends to increase emissions of criteria air pollutants. However, not adding capacity to a road network also increases emissions of pollutants. Therefore, an optimization problem and solution method, such as the emissions network design problem and solution method presented here, is useful for identifying capacity additions that reduce vehicle emissions. It is also useful for understanding the tradeoffs between designing a network for minimal congestion versus minimal vehicle emissions.

Emission Reductions from Woody Biomass Waste for Energy as an Alternative to Open Burning

ABSTRACT Woody biomass waste is generated throughout California from forest management, hazardous fuel reduction, and agricultural operations. Open pile burning in the vicinity of generation is frequently the only economic disposal option. A framework is developed to quantify air emissions reductions for projects that alternatively utilize bio-mass waste as fuel for energy production. A demonstration project was conducted involving the grinding and 97-km one-way transport of 6096 bone-dry metric tons (BDT) of mixed conifer forest slash in the Sierra Nevada foothills for use as fuel in a biomass power cogeneration facility. Compared with the traditional open pile burning method of disposal for the forest harvest slash, utilization of the slash for fuel reduced particulate matter (PM) emissions by 98% (6 kg PM/BDT biomass), nitrogen oxides (NOx) by 54% (1.6 kg NOx/BDT), nonmethane volatile organics (NMOCs) by 99% (4.7 kg NMOCs/BDT), carbon monoxide (CO) by 97% (58 kg CO/BDT), and carbon dioxide equivalents (CO2e) by 17% (0.38 t CO2e/BDT).Emission contributions from biomass processing and transport operations are negligible. CO2e benefits are dependent on the emission characteristics of the displaced marginal electricity supply. Monetization of emissions reductions will assist with fuel sourcing activities and the conduct of biomass energy projects. IMPLICATIONS Economic considerations frequently dictate the disposal of woody biomass wastes by open burning. The alternative use for energy provides significant reduction in criteria air pollutant and greenhouse emissions. Valuing these reductions will improve the economic viability and increase the use of biomass for energy as well as assist with forest and agricultural management objectives.

Life Cycle Emissions and Cost of Producing Electricity from Coal, Natural Gas, and Wood Pellets in Ontario, Canada

The use of coal is responsible for (1)/(5) of global greenhouse gas (GHG) emissions. Substitution of coal with biomass fuels is one of a limited set of near-term options to significantly reduce these emissions. We investigate, on a life cycle basis, 100% wood pellet firing and cofiring with coal in two coal generating stations (GS) in Ontario, Canada. GHG and criteria air pollutant emissions are compared with current coal and hypothetical natural gas combined cycle (NGCC) facilities. 100% pellet utilization provides the greatest GHG benefit on a kilowatt-hour basis, reducing emissions by 91% and 78% relative to coal and NGCC systems, respectively. Compared to coal, using 100% pellets reduces NO(x) emissions by 40-47% and SO(x) emissions by 76-81%. At $160/metric ton of pellets and $7/GJ natural gas, either cofiring or NGCC provides the most cost-effective GHG mitigation ($70 and $47/metric ton of CO2 equivalent, respectively). The differences in coal price, electricity generation cost, and emissions at the two GS are responsible for the different options being preferred. A sensitivity analysis on fuel costs reveals considerable overlap in results for all options. A lower pellet price ($100/metric ton) results in a mitigation cost of $34/metric ton of CO2 equivalent for 10% cofiring at one of the GS. The study results suggest that biomass utilization in coal GS should be considered for its potential to cost-effectively mitigate GHGs from coal-based electricity in the near term.

Comparison of Exhaust Emissions Resulting from Cold- and Hot-Start Motorcycle Driving Modes

This study investigated the emissions of criteria air pollutants (carbon monoxide [CO], hydrocarbons [HCs], and oxides of nitrogen [NOx]) from motorcycle exhaust at cold- and hot-start driving cycles on a chassis dynamometer. Seven four-stroke carburetors and two fuel-injection motorcycles were tested. As expected, the emission factors (g/km) of CO and HCs increased during cold-start driving. The ratio of emission factors (g/km) for cold- and hot-start driving cycles ranged from 1.1–1.5 (for CO) to 1.2–2.8 (for HCs). However, the difference of NOx emissions between the cold- and hot-start cycles was not pronounced. Further, the cold-/hot-start ratios of CO and HCs from 50-cm3 motorcycles were higher than those of 100- and 125-cm3 motorcycles; however, the carbon dioxide (CO2) emission was the lowest for the four-stroke motorcycles. High engine temperature and poor combustion efficiency of smaller cylinder-capacity motorcycles may contribute a significant amount of exhaust emission. Additionally, the fuel-base emission factor (g/L-fuel) ratios were low compared with the distance-base emission factor (g/km) in cold- and hot-start driving. This indicates that the effect of catalyst efficiency was greater than the effect of fuel combustion in the tested motorcycles. A comparison of emission ratios of motorcycles and passenger cars shows that the warm-up may be more important for cars, especially under low-temperature conditions. However, the motorcycle contributes a large proportion of CO and HC emissions in many Asian counties. The difference between cold- and hot-start emissions may affect inventory accuracy, especially in HC emissions. For those tropical or subtropical countries in which motorcycles are one of the dominant air pollution sources, optimizing the engine combustion efficiency and developing new catalyst technology of motorcycles at cold-start conditions are the key issues to be improved.

Effects of ethanol-blended gasoline on air pollutant emissions from motorcycle

The effect of ethanol–gasoline blends on criteria air pollutant emissions was investigated in a four-stroke motorcycle. The ethanol was blended with unleaded gasoline in four percentages (3, 10, 15, and 20% v/v) and controlled at a constant research octane number, RON (95), to accurately represent commercial gasoline. CO, THC, and NOx emissions were evaluated using the Economic Commission for Europe cycle on the chassis dynamometers. The results of the ethanol–gasoline blends were compared to those of commercial unleaded gasoline with methyl tert-butyl ether as the oxygenated additive. In general, the exhaust CO and NOx emissions decreased with increasing oxygen content in fuels. In contrast, ethanol added in the gasoline did not reduce the THC emissions for a constant RON gasoline. The 15% ethanol blend had the highest emission reductions relative to the reference fuel. The high ethanol–gasoline blend ratio (20%) resulted in a less emission reduction than those of low ratio blends (< 15%). This may be attributed to the changes in the combustion conditions in the carburetor engine with 20% ethanol addition. Furthermore, the influence of ethanol–gasoline blends on the reduction of exhaust emissions was observed at different driving modes, especially at 15 km/h cruising speed for CO and THC and acceleration stages for NOx.

Life cycle optimization of ownership costs and emissions reduction in US vehicle retirement decisions

Vehicle scrappage programs have emerged in the US to address the challenge of regional fleets that contain older, often inefficient vehicles with higher emissions and lower fuel economy. These programs provide an incentive for removal of old vehicles from the road before their economic lifetimes have been exhausted. Scrappage programs operate on the assumption that newer vehicles will offer more efficient, less polluting alternatives to older vehicles. Little attention, however, has been given to the additional energy and emissions burdens associated with the manufacture of the replacement vehicles. This paper considers the optimal intervals for vehicle replacement over a 36-year period that minimize life cycle economic and emissions burdens. Comparisons are made between the optimal product replacement intervals based on explicit private costs, estimated pollution damage costs, carbon dioxide emissions, energy use, and criteria air pollutant emissions. The results show that private costs of vehicle ownership favor long replacement intervals (in the range of 17–19 years), while short replacement intervals support minimization of criteria air pollutants such as CO (3–6 year intervals), NO x (5–7 year intervals), and NMHC (6–9 year intervals). Longer ownership periods (18 year intervals), however, provide minimum life cycle CO 2 emissions and energy use. When damage cost factors are used to estimate the external costs of pollution to society, intermediate replacement intervals (10–14 year) are favored.

Modeling the Benefits of Power Plant Emission Controls in Massachusetts

Older fossil-fueled power plants provide a significant portion of emissions of criteria air pollutants in the United States, in part because these facilities are not required to meet the same emission standards as new sources under the Clean Air Act. Pending regulations for older power plants need information about any potential public health benefits of emission reductions, which can be estimated by combining emissions information, dispersion modeling, and epidemiologic evidence. In this article, we develop an analytical modeling framework that can evaluate health benefits of emission controls, and we apply our model to two power plants in Massachusetts. Using the CALPUFF atmospheric dispersion model, we estimate that use of Best Available Control Technology (BACT) for NOx and SO2 would lead to maximum annual average secondary particulate matter (PM) concentration reductions of 0.2 μg/m3. When we combine concentration reductions with current health evidence, our central estimate is that the secondary PM reductions from these two power plants would avert 70 deaths per year in a population of 33 million individuals. Although benefit estimates could differ substantially with different interpretations of the health literature, parametric perturbations within CALPUFF and other simple model changes have relatively small impacts from an aggregate risk perspective. While further analysis would be required to reduce uncertainties and expand on our analytical model, our framework can help decision-makers evaluate the magnitude and distribution of benefits under different control scenarios.

Total Energy Cycle Energy Use and Emissions of Electric Vehicles

A total energy cycle analysis (TECA) of electric vehicles (EVs) was recently completed. The EV energy cycle includes production and transport of fuels used in power plants to generate electricity, electricity generation required to charge EV batteries, EV operation, and vehicle and battery manufacture. The key assumptions and results of the EVTECA are summarized. The total energy requirements of EVs are estimated to be 24 to 35 percent lower than those of the conventional, gasoline-fueled vehicles that they replace, whereas the reductions in total oil use are even greater: 55 to 85 percent. Greenhouse gas (GHG) emissions are 24 to 37 percent lower with EVs. EVs reduce total emissions of several criteria air pollutants [volatile organic compounds (VOCs), carbon monoxide (CO), and nitrogen oxides] but increase total emissions of others [sulfur oxide (SOx), total suspended particulates, and lead] over the total energy cycle. Regional emissions except possibly those of SOx are generally reduced with EVs. The limitations of the EVTECA are discussed, and its results are compared with those of other evaluations of EVs. In general, many of the results (particularly the results for oil use, GHGs, VOCs, CO, SOx, and lead) of the analysis are consistent with those of other evaluations.

An evaluation of integrated climate protection policies for the US

This paper presents and discusses an integrated set of policies designed to reduce carbon emissions in the US. This policy package also aims to promote environmental quality, particularly by reducing emissions of criteria air pollutants, to reduce US dependence on imported oil, and to induce technological innovation and diffusion in energy production and consumption. The policy package analyzed is found to reduce economy-wide carbon emissions by 10% relative to 1990 levels in 2010, and by 45% relative to 1990 levels in 2030. Emissions of criteria pollutants are also significantly reduced, as are petroleum imports by the US. Moreover, the policy package yields net savings for the US, equal to $19 billion on an annual levelized basis through 2010, and results in 800,000 additional jobs nationwide by 2010. While the overall findings from the policy package analysis are robust, the results should be taken as indicative, rather than precisely predictive, owing to uncertainties in future costs, prices, technology performance and consumer behavior.