Criteria Air Pollutant Emissions Research Articles

Pathways to zero emissions in California’s heavy-duty transportation sector

California contributes 0.75% of global greenhouse gas (GHG) emissions and has a target of reaching economy-wide net zero emissions by 2045, requiring all sectors to rapidly reduce emissions. Nearly 8% of California’s GHG emissions are from the heavy-duty transportation sector. In this work, we simulate decarbonization strategies for the heavy-duty vehicle (HDV) fleet using detailed fleet turnover and air quality models to track evolution of the fleet, GHG and criteria air pollutant emissions, and resulting air quality and health impacts across sociodemographic groups. We assess the effectiveness of two types of policies: zero emission vehicle sales mandates, and accelerated retirement policies. For policies including early retirements, we estimate the cost of early retirements and the cost-effectiveness of each policy. We find even a policy mandating all HDV sales to be zero emission vehicles by 2025 would not achieve fleetwide zero emissions by 2045. For California to achieve its goal of carbon neutrality, early retirement policies are needed. We find that a combination of early retirement policies and zero emission vehicle sales mandates could reduce cumulative CO2 emissions by up to 64%. Furthermore, we find that decarbonization policies will significantly reduce air pollution-related mortality, and that Black, Latino, and low-income communities will benefit most. We find that policies targeting long-haul heavy-heavy duty trucks would have the greatest benefits and be most cost-effective.

Life-cycle analysis of battery metal recycling with lithium recovery from a spent lithium-ion battery

Demand for critical materials (nickel, cobalt, manganese [NCM], and lithium) for use in batteries is increasing rapidly due to the expansion of the battery-electric vehicles market. Battery metal recycling (BMR) is an important technology that can potentially realize environmental and economic benefits in cathode active material (LiNixMnyCozO2) production using recycled materials. While current major battery recycling technologies recover cathode materials (NCM) and other metals (steel, aluminum, copper, etc.) from the spent battery, the lithium (Li) recovery rate is less than 1% in the world. In this study, we analyze the environmental benefits of a BMR process that recovers lithium in the form of lithium hydroxide monohydrate (LiOH∙H2O) along with other cathode materials. Using life-cycle analysis (LCA), we evaluate the life-cycle greenhouse gas (GHG) emissions, criteria air pollutant emissions, and water consumption of the new BMR technology in terms of lithium hydroxide production and cathode active material production. The LCA results show that the life-cycle GHG emissions recycled LiOH are 37–72% lower than those of virgin LiOH production from Chilean brine and Australian ore, respectively. In addition, the life-cycle GHG emissions of NCM811 produced using the recycled materials are 40–48% lower compared to virgin cathode active material production. Furthermore, recovering lithium from the spent batteries reduces associated air pollutant emissions and water consumption relative to using the virgin materials or materials from other recycling technologies without LiOH recovery.

Emissions redistribution and environmental justice implications of California’s clean vehicle rebate project

Vehicle electrification is expected to reduce, in aggregate, emissions of greenhouse gases and criteria air pollutants. However, increased electricity generation to support new electric vehicles introduces possible redistribution of point-source emissions from mobile vehicles to electric generating units such that emissions may decrease in some locations and increase in others, with implications for equity. The potential for vehicle electrification to thereby shift the spatial distribution of air-pollution burdens has been previously noted, but analyses have yet to evaluate specific implemented climate policies. Here, we develop a model to analyze the implications of California’s Clean Vehicle Rebate Project (CVRP) for emissions of greenhouse gases and criteria air pollutants, both in aggregate and in their distribution. Analyzing rebates for 2010–2021, we find that the CVRP reduced aggregate statewide emissions of CO2, NOX, and SO2 and increased aggregate statewide emissions of primary PM2.5. Furthermore, changes in air pollution are not distributed equally: our results indicate that, as a result of the CVRP, net primary PM2.5, NOX, and SO2 emissions reductions disproportionately occur in Least Disadvantaged Communities, as compared to Disadvantaged Communities, with community disadvantage defined according to CalEnviroScreen 4.0 per California legislation. If the current spatial distribution of electric vehicle rebates remains unchanged, we project that these inequities will continue through the state’s legislative goal of 1.5 million zero-emission vehicles on California roadways by 2025, even with increased cleanliness of the electricity sources for new vehicles. Increased uptake of electric vehicles in communities facing the highest air pollution exposure, along with accelerated clean-energy generation, could ameliorate associated environmental inequities.

Environmental life cycle assessment of olefins and by-product hydrogen from steam cracking of natural gas liquids, naphtha, and gas oil

Steam cracking is an energy-intensive process used to convert natural gas liquids, naphtha, and gas oil into ethylene and propylene, as well as other chemicals. It is the primary source of ethylene, one of the most important building blocks for the chemical and plastics industry. Steam cracking also co-produces hydrogen which is typically combusted with the tail gas onsite for process heat, but alternatively could be separated and sold as a by-product. This study provides a detailed life cycle inventory for the United States steam cracking industry based on publicly-available, facility-specific information; provides industry average results; and assesses variability across facilities, feedstocks, and technologies. This life cycle inventory provides the baseline needed for comparison of plastic alternatives designed to improve recyclability and reduce the environmental effects of plastics. Likewise, the environmental profile of by-product hydrogen from steam crackers is important for assessing its potential benefit in decarbonizing transportation and/or industry, considering the energy use for separation and compression, as well as the make-up fuel requirements. We present the cradle-to-gate results for all steam cracking products and find the life cycle GHG emissions for average U.S. ethylene and propylene are 1.13 kg CO2e per kilogram using a mass allocation, 1.05 kg CO2e for facilities that combust their hydrogen, and 1.30 kg CO2e for facilities that separate by-product hydrogen for use. With natural gas production and ethylene demand continuing at high levels in the United States, decarbonizing steam cracking would be an important step toward mitigating emissions from the chemical industry. Similarly, the benefit of using by-product hydrogen to decarbonize other processes is dependent on the relative benefit of the hydrogen application compared with the alternative energy source used for steam cracking process heat. Results are also reported for criteria air pollutant emissions, energy use, water use, and a series of life cycle impact potentials.

Life-Cycle Approach to Healthy Airport Terminal Buildings: Spatial-Temporal Analysis of Mitigation Strategies for Addressing the Pollutants that Affect Climate Change and Human Health

The potential environmental and human health impacts associated with constructing and operating terminal buildings is explored for commercial airports in the United States. Research objectives are to quantify: (1) baseline and mitigated greenhouse gas (GHG) and criteria air pollutant (CAP) emissions; (2) operational costs; and (3) climate change damages from terminal building construction and materials, operational energy consumption, water consumption and wastewater generation, and solid waste generation. An Excel-based decision-support tool, Airport Terminal Environmental Support Tool (ATEST), has been created to allow stakeholders to conduct preliminary assessments of current baseline and potential mitigated impacts. Emissions are quantified using a life-cycle approach that accounts for cradle-to-grave effects. Climate change and human health indicators are characterized using EPA’s Tool for Reduction and Assessment of Chemical Impact (TRACI) factors. ATEST is applied to multiple case study airports— Reno/Tahoe International (RNO), Pittsburgh International (PIT), Newark Liberty International (EWR), Seattle-Tacoma International (SEA), San Francisco International (SFO), and Hartsfield-Jackson Atlanta International (ATL)—to demonstrate its scalability and capability to assess varying spatial factors. Across all airports, electricity mix and construction are significant in determining GHG and CAP emissions, respectively. A sensitivity analysis of GHG emissions for the SFO case study reveals that the electricity mix, amount of electricity consumed within the terminal, terminal gross area, and amount of compostables in the solid waste stream have the most impact on increasing annual GHG emissions. ATEST represents a crucial first step in helping stakeholders to make decisions that will lead to healthier, more sustainable airport terminals.

Regional Emissions Analysis of Light-Duty Battery Electric Vehicles

Light-duty battery electric vehicles (BEVs) can reduce both greenhouse gas (GHG) and criteria air pollutant (CAPs) emissions, when compared to gasoline vehicles. However, research has found that while today’s BEVs typically reduce GHGs, they can increase certain CAPs, though with significant regional variability based on the electric grid mix. In addition, the environmental performance of electric and gasoline vehicles is not static, as key factors driving emissions have undergone significant changes recently and are expected to continue to evolve. In this study, we perform a cradle-to-grave life cycle analysis using state-level generation mix and vehicle operation emission data. We generated state-level emission factors using a projection from 2020 to 2050 for three light-duty vehicle types. We found that BEVs currently provide GHG benefits in nearly every state, with the median state’s benefit being between approximately 50% to 60% lower than gasoline counterparts. However, gasoline vehicles currently have lower total NOx, urban NOx, total PM2.5, and urban PM2.5 in 33%; 15%; 70%; and 10% of states, respectively. BEV emissions will decrease in 2050 due to a cleaner grid, but the relative benefits when compared to gasoline vehicles do not change significantly, as gasoline vehicles are also improving over this time.

A physics-informed data reconciliation framework for real-time electricity and emissions tracking

To encourage and guide decarbonization efforts, better tools are needed to monitor real-time CO2 and criteria air pollutant emissions from electricity consumption, production, imports, and exports. Using real-time data from the electricity system is especially challenging for quantitative applications requiring high quality and physically consistent data. Until now, time-intensive, ad-hoc and manual data verification and cleaning strategies have been used to prepare the data for quantitative analysis. As an alternative to existing techniques, here we provide a physics-informed framework to greatly accelerate and automate data processing to enable internally consistent electric system consumption, production, import, and export data in near real-time. A key component of this framework is an optimization program to minimize the data adjustments required to satisfy energy conservation equations. The effectiveness of this method is demonstrated by applying it to the continental United States electricity network. The resulting publicly-available data set, which provides in near-real time, hourly updates on electricity generation, consumption, imports, exports and associated emissions, is the first of this nature.

Biofuel Options for Marine Applications: Technoeconomic and Life-Cycle Analyses.

This study performed technoeconomic and life-cycle analyses to assess the economic feasibility and emission benefits and tradeoffs of various biofuel production pathways as an alternative to conventional marine fuels. We analyzed production pathways for (1) Fischer-Tropsch diesel from biomass and cofeeding biomass with natural gas or coal, (2) renewable diesel via hydroprocessed esters and fatty acids from yellow grease and cofeeding yellow grease with heavy oil, and (3) bio-oil via fast pyrolysis of low-ash woody feedstock. We also developed a new version of the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) marine fuel module for the estimation of life-cycle greenhouse gas (GHG) and criteria air pollutant (CAP) emissions of conventional and biobased marine fuels. The alternative fuels considered have a minimum fuel selling price between 2.36 and 4.58 $/heavy fuel oil gallon equivalent (HFOGE), and all exhibit improved life-cycle GHG emissions compared to heavy fuel oil (HFO), with reductions ranging from 40 to 93%. The alternative fuels also exhibit reductions in sulfur oxides and particulate matter emissions. Additionally, when compared with marine gas oil and liquified natural gas, they perform favorably across most emission categories except for cases where carbon and sulfur emissions are increased by the cofed fossil feedstocks. The pyrolysis bio-oil offers the most promising marginal CO2 abatement cost at less than $100/tonne CO2e for HFO prices >$1.09/HFOGE followed by Fischer-Tropsch diesel from biomass and natural gas pathways, which fall below $100/tonne CO2e for HFO prices >$2.25/HFOGE. Pathways that cofeed fossil feedstocks with biomass do not perform as well for marginal CO2 abatement cost, particularly at low HFO prices. This study indicates that biofuels could be a cost-effective means of reducing GHG, sulfur oxide, and particulate matter emissions from the maritime shipping industry and that cofeeding biomass with natural gas could be a practical approach to smooth a transition to biofuels by reducing alternative fuel costs while still lowering GHG emissions, although marginal CO2 abatement costs are less favorable for the fossil cofeed pathways.

Well-to-Wheels Analysis of Zero-Emission Plug-In Battery Electric Vehicle Technology for Medium- and Heavy-Duty Trucks.

Conventional diesel medium- and heavy-duty vehicles (MHDVs) create large amount of air emissions. With the advancement in technology and reduction in the cost of batteries, plug-in battery electric vehicles (BEVs) are increasingly attractive options for improving energy efficiency and reducing air emissions of MHDVs. In this paper, we compared the well-to-wheels (WTW) greenhouse gases (GHGs) and criteria air pollutant emissions of MHD BEVs with their conventional diesel counterparts across weight classes and vocations. We expanded the Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET) model to conduct the WTW analysis of MHDVs. The fuel economy for a wide range of MHDV weight classes and vocations, over various driving cycles, was evaluated using a high-fidelity vehicle dynamic simulation software (Autonomie). The environmental impacts of MHD BEVs are sensitive to the source of electricity used to recharge their batteries. The WTW results show that MHD BEVs significantly improve environmental sustainability of MHDVs by providing deep reductions in WTW GHGs, nitrogen oxides, volatile organic compounds, and carbon monoxide emissions, compared to conventional diesel counterparts. Increasing shares of renewable and natural gas technologies in future national and regional electricity generation are expected to reduce WTW particulate matters and sulfur oxide emissions for further improvement of the environmental performance of MHD BEVs.

Well-to-wheels emissions, costs, and feedstock potentials for light-duty hydrogen fuel cell vehicles in China in 2017 and 2030

Hydrogen has the potential to contribute to a clean, secure, and affordable energy future. It can provide distributed energy storage for intermittent renewable energy resources and support hydrogen-based transportation. This study reports well-to-wheels greenhouse gas (GHG) and criteria air pollutant emissions and levelized cost of driving (LCD) for light-duty fuel cell vehicles (FCVs) in China in 2017 and 2030, powered with hydrogen from renewable and conventional sources. All FCV pathways, except electrolysis using grid electricity or liquefied hydrogen pathways, have GHG, volatile organic compounds (VOCs), nitrogen oxides (NOX), fine particulate matter (PM2.5), and sulfur dioxide (SO2) emissions lower than, or comparable to, gasoline vehicles. Electricity sources strongly influence the environmental impacts for electrolysis-based hydrogen pathways. For FCV GHG, NOX, PM2.5, and SO2 emissions to be lower than gasoline vehicles, the share of coal-fired electricity used in hydrogen production must be less than 50%, 58%, 20%, and 34%, respectively; the share of coal in electricity generation in China was ~65% in 2017 and is projected to be ~50% in 2030. A case study shows that additional electricity is required to supplement wind curtailment to achieve higher hydrogen production volumes thus lowering production cost. Assuming decreased costs for both hydrogen production and FCVs in 2030, the LCD for wind-electrolysis FCV pathway (~$0.31/km) could approach that for gasoline (~$0.29/km) and battery electric vehicles (~$0.30/km). Wind and solar curtailment were 27.7 TWh and 5.5 TWh in 2018 and could be used to produce hydrogen for 4.9 million FCVs.

What are the best combinations of fuel-vehicle technologies to mitigate climate change and air pollution effects across the United States?

The transportation sector is the largest contributor to CO2 emissions and a major source of criteria air pollutants in the United States. The impact of climate change and that of air pollution differ in space and time, but spatially-explicit, systematic evaluations of the effectiveness of alternative fuels and advanced vehicle technologies in mitigating both climate change and air pollution are lacking. In this work, we estimate the life cycle monetized damages due to greenhouse gas emissions and criteria air pollutant emissions for different types of passenger-moving vehicles in the United States. We find substantial spatial variability in the monetized damages for all fuel-vehicle technologies studied. None of the fuel-vehicle technologies leads simultaneously to the lowest climate change damages and the lowest air pollution damages across all U.S. counties. Instead, the fuel-vehicle technology that best mitigates climate change in one region is different from that for the best air quality (i.e. the trade-off between decarbonization and air pollution mitigation). For example, for the state of Pennsylvania, battery-electric cars lead to the lowest population-weighted-average climate change damages (a climate change damage of 0.87 cent/mile and an air pollution damage of 1.71 cent/mile). In contrast, gasoline hybrid-electric cars lead to the lowest population-weighted-average air pollution damages (a climate change damage of 0.92 cent/mile and an air pollution damage of 0.77 cent/mile). Vehicle electrification has great potential to reduce climate change damages but may increase air pollution damages substantially in regions with high shares of coal-fired power plants compared to conventional vehicles. However, clean electricity grid could help battery electric vehicles to achieve low damages in both climate change and air pollution.

Modeling net effects of transit operations on vehicle miles traveled, fuel consumption, carbon dioxide, and criteria air pollutant emissions in a mid-size US metro area: findings from Salt Lake City, UT

The Utah Transit Authority (UTA) serves Utah’s Wasatch Front, a rapidly growing conurbation with a current population of ∼1.8 M people. UTA uses an electronic fare collection (EFC) system that requires riders to tap on as they enter a bus or train and tap off as they exit, as well as an automated passenger counter (APC) system that counts interruptions of infrared beams across vehicle doorways as riders board and alight. We analyzed EFC and APC data for 2016, along with service schedules and routes from General Transit Feed Specification (GTFS) data, to estimate the impact of UTA on the air quality in its service region by accounting for vehicle miles traveled, gasoline gallons equivalent of fuel consumed, and multiple pollutant species emitted. Buses, light rail, and commuter rail were found to collectively offset approximately 1.5% of the onroad emissions from the counties served by UTA due to transit use replacing single passenger vehicle use. These offsets are not homogeneous; ridership drops significantly (∼20%–50% depending on the mode) during the summer months as some of the largest users are educational institutions with noticeable seasonal cycles. Low transit use during the weekend negates some of the air quality benefits as buses and trains travel at lower capacity. Central routes, particularly during peak travel hours provide noticeable congestion, fuel consumption, and pollutant emissions reduction due to trips taken by transit replacing personal vehicles but off-peak, and non-central routes, show lower benefits. Because the light rail is electric, its local air quality benefits are significant due to the electricity being produced primarily outside the airshed. Upgrading the bus fleet to 2010 model, and newer, diesel and compressed natural gas (CNG) buses, as well as modeling an envisioned change to Tier 3 locomotives for the commuter rail system, was found to significantly reduce regional nitrogen oxides (NOx), fine particulate matter (PM2.5), and sulfur oxides (SOx) emissions.

Criteria Air Pollutant and Greenhouse Gases Emissions from U.S. Refineries Allocated to Refinery Products.

Using Greenhouse Gas Reporting Program data (GHGRP) and National Emissions Inventory data from 2014, we investigate U.S. refinery greenhouse gas (GHG) emissions (CO2, CH4, and N2O) and criteria air pollutant (CAP) emissions (VOC, CO, NO x, SO2, PM10, and PM2.5). The study derives (1) combustion emission factors (EFs) of refinery fuels (e.g., refinery catalyst coke and refinery combined gas), (2) U.S. refinery GHG emissions and CAP emissions per crude throughput at the national and regional levels, and (3) GHG and CAP emissions attributable to U.S. refinery products. The latter two emissions were further itemized by source: combustion emission, process emission, and facility-wide emission. We estimated U.S. refinery product GHG and CAP emissions via energy allocation at the refinery process unit level. The unit energy demand and unit flow information were adopted from the Petroleum Refinery Life Cycle Inventory Model (PRELIM version 1.1) by fitting individual U.S. refineries. This study fills an important information gap because it (1) evaluates refinery CAP emissions along with GHG emissions and (2) provides CAP and GHG emissions not only for refinery main products (gasoline, diesel, jet fuel, etc.) but also for refinery secondary products (asphalt, lubricant, wax, light olefins, etc.).

Criteria Air Pollutants and Greenhouse Gas Emissions from Hydrogen Production in U.S. Steam Methane Reforming Facilities.

The global and U.S. domestic effort to develop a clean energy economy and curb environmental pollution incentivizes the use of hydrogen as a transportation fuel, owing to its zero tailpipe pollutant emissions and high fuel efficiency in fuel cell electric vehicles (FCEVs). However, the hydrogen production process is not emissions free. Conventional hydrogen production via steam methane reforming (SMR) is energy intensive, coproduces carbon dioxide, and emits air pollutants. Thus, it is necessary to quantify the environmental impacts of SMR hydrogen production alongside the use-phase of FCEVs. This study fills the information gap, analyzing the greenhouse gas (GHG) and criteria air pollutant (CAP) emissions associated with hydrogen production in U.S. SMR facilities by compiling and matching the facility-reported GHG and CAP emissions data with facilities' hydrogen production data. The actual amounts of hydrogen produced at U.S. SMR facilities are often confidential. Thus, we have developed four approaches to estimate the hydrogen production amounts. The resultant GHG and CAP emissions per MJ of hydrogen produced in individual facilities were aggregated to develop emission values for both a national median and a California state median. This study also investigates the breakdown of facility emissions into combustion emissions and noncombustion emissions.

The Affordable Clean Energy rule and the impact of emissions rebound on carbon dioxide and criteria air pollutant emissions

The Affordable Clean Energy (ACE) rule, the US Environmental Protection Agency’s (EPA) proposed replacement of the Clean Power Plan (CPP), targets heat rate improvements (HRIs) at individual coal plants in the US. Due to greater plant efficiency, such HRIs could lead to increased generation and emissions, known as an emissions rebound effect. The EPA Regulatory Impact Analysis for the ACE and other analyses to date have not quantified the magnitude and extent of an emissions rebound. We analyze the estimated emissions rebound of carbon dioxide (CO2) and criteria pollutants sulfur dioxide (SO2) and nitrogen oxides (NOX), using results from the EPA’s power sector model, under the ACE in 2030 at model coal plants and at the state and national levels compared to both no policy and the CPP. We decompose emissions changes under a central illustrative ACE scenario and find evidence of a state-level rebound effect. Although the ACE reduces the emissions intensity of coal plants, it is expected to increase the number of operating coal plants and amount of coal-fired electricity generation, with 28% of model plants showing higher CO2 emissions in 2030 compared to no policy. As a result, the ACE only modestly reduces national power sector CO2 emissions and increases CO2 emissions by up to 8.7% in 18 states plus the District of Columbia in 2030 compared to no policy. We also find that the ACE increases SO2 and NOX emissions in 19 states and 20 states plus DC, respectively, in 2030 compared to no policy, with implications for air quality and public health. We compare our findings to other model years, additional EPA ACE scenarios, and other modeling results for similar policies, finding similar outcomes. Our results demonstrate the importance of considering the emissions rebound effect and its effect on sub-national emissions outcomes in evaluating the ACE and similar policies targeting HRIs.

Criteria air pollutants from cement production in Nigeria

AbstractThis study aims at determining the impact of uncontrolled criteria air pollutants on air quality. The research estimates the emissions of criteria air pollutants from existing and proposed cement production facilities using the emission factor approach. The emissions from the existing plants for particulate matter (PM), sulfur dioxide (SO2), oxides of nitrogen (NOx), carbon dioxide (CO2), and lead ranged between 0.031 and 354,240 tons per annum; 9.07 and 31,953.6 tons per annum; 5.04 and 17,750 tons per annum; 0.173 and 621.12 tons per annum; and 0.033 and 354.72 tons per annum; respectively, while estimated values for proposed plants for PM, SO2, NOx, CO, and lead ranged between 1.2 and 134,995.2 tons per annum; 35.52 and 13,497.6 tons per annum; 19.728 and 7,497 tons per annum, 0.67 and 264 tons per annum; and 0.096 and 148.80 tons per annum; respectively. PM emissions had the highest values, while values for SO2, NOx, CO, and Pb followed in decreasing order. Consistent use of emission control systems and substitution of kiln fuels with alternative fuels can help reduce the impact of cement production on air quality.

Direct hydrogen fuel cell electric vehicle cost analysis: System and high-volume manufacturing description, validation, and outlook

Direct hydrogen fuel cell electric vehicles (FCEVs) produce only water as a byproduct, thereby eliminating tailpipe carbon and criteria air pollutant emissions associated with internal combustion engine vehicles (ICEVs). However, in order to achieve economic parity with ICEVs, technological challenges must be overcome to lower system cost. The U.S. Department of Energy (DOE) monitors estimated fuel cell (FC) system cost and tracks progress towards milestones by techno-economic analysis based on demonstrated laboratory technologies for a next-generation 80 kWnet automotive FC stack for light-duty vehicles. The findings of the 2017 automotive FC system cost analysis are summarized, including the baseline system characteristics and specifications and the results of Design for Manufacture and Assembly (DFMA®) analysis of system manufacturing across a range of annual production rates. The highest volume predictions, for 100,000 and 500,000 units per year, result in a total system cost of $50/kWnet and $45/kWnet, respectively. The assumptions and methodology of the DFMA® analysis of the 2017 baseline FC system were validated by comparison with the FC system in the commercially available Toyota Mirai. One prospective pathway for decreasing system cost to $30/kWnet needed for cost competitiveness with ICEVs is outlined.

Estimation of gaseous criteria air pollutants from road transport system in Lagos metropolis of Nigeria

AbstractAmbient air pollution by vehicular emissions is underestimated, especially in the major cities of Nigeria. The buildup of the emissions in the atmosphere is a major health concern. This study estimated the emissions of gaseous criteria air pollutants (CAPs) from the road transport system in the Lagos metropolis from the year 2004 to 2007. The study also determined the ground‐level concentrations of these pollutants for the years under review. Estimation of the emission rates of all types of vehicles was performed using an emission factor approach, while the ground‐level concentrations of the CAPs were determined using the Industrial Source Complex Short Term 3 view model. The results showed that the mean concentrations of carbon monoxide in the ambient air were 26,741.12, 31,675.95, 54,515.48, and 72,388.09 micrograms per cubic meter (μg/m3) for years 2004, 2005, 2006, and 2007, respectively, while the estimated concentrations for oxides of nitrogen were 1,377.91 μg/m3 for year 2004, and 1,620.76, 2,897.33, and 3,839.68 μg/m3, respectively, for the years 2005, 2006, and 2007. The estimated concentrations of sulfur dioxide during the study period were 51,354.16, 57,244.76, 113,083.26, and 136,332.01 μg/m3 for 2004, 2005, 2006, and 2007, respectively. For volatile organic compounds, the estimated concentrations were 3,839.68, 6,839.65, 7,067.62, and 8,431.35 μg/m3 for years 2004, 2005, 2006, and 2007, respectively. The results also show that the maximum ground‐level concentrations were highest along the roadside, and the average CAPs concentrations and cumulative exposure concentrations that were estimated throughout the study period are a major health concern, as these concentrations are several times higher than international limits.

Paper Burning and Associated Pollution Problems in Higher Educational Institutions of Ethiopia; The Need and Potential for Recycling

Higher educational institutions use large amount of paper for students’ assessment each year. As recycling is one of the best options for efficient material utilization and waste management, the potential in higher education institutions was assessed taking Kotebe Metropolitan University (KMU) and Ethiopian Civil Service University (ECSU) as sampling site. The aim was to evaluate the human health and environmental consequences of storing and burning assessment paper there by turning the cause of the damage to sustainable utilization through proposing recycling. Accordingly, the potential criteria air pollutant emissions while burning assessment papers, heavy metal concentrations in the ash of the burned paper and macro-nutrients were determined using Aero-Qual series 300 in open burning at KMU, and Atomic Absorption Spectrophotometer at JIJE Analytical Testing Service Laboratory, respectively. It was found that the average emissions for CO (119.67 ppm), CO2 (1700 ppm), SO2 (038 ppm), VOCs (3749 ppm) and NOx (0.10 ppm) were recorded. The concentration of CO, SO2 and NOx were significantly higher than the guidelines recommended by WHO and other international organizations. The paired sample t-test between white paper and the printed one showed significant difference (p<0.05) on the parameters CO2 and NOx. Similarly, the heavy metal analysis result indicated that Cd (0.47 mg/kg), and Pb (0.48 mg/l) were detected from the ash of printed paper. Moreover, the average pH and macro-nutrients (NPK values) of the printed paper were 9.07, 0.83%, 40.88 ppm and 83.68 ppm respectively. About 35, 000 ream of paper is burnt in each of the institutions per year, and 69% of the respondents (instructors) were volunteered and were ready, to provide assessment paper for recycling which shows that there exist considerable potential for paper recycling in HEIs. Therefore, the researchers need to recommend that paper recycling should be taken as an integrated system of the activities in HEIs.

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.