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Final Report: Effects of Climate Change and Greenhouse Gas Mitigation Strategies on Air Quality

EPA Grant Number: R834284
Title: Effects of Climate Change and Greenhouse Gas Mitigation Strategies on Air Quality
Investigators: Brouwer, Jacob , Dabdub, Donald
Institution: University of California - Irvine
EPA Project Officer: Hahn, Intaek
Project Period: December 1, 2009 through November 30, 2012 (Extended to November 30, 2013)
Project Amount: $600,000
RFA: Adaptation for Future Air Quality Analysis and Decision Support Tools in Light of Global Change Impacts and Mitigation (2008) RFA Text |  Recipients Lists
Research Category: Climate Change , Air Quality and Air Toxics , Air

Objective:

Future efforts to mitigate climate change will include transitions to alternative technologies and fuels seeking reductions in greenhouse gas (GHG) emissions from U.S. energy sectors, including power generation and transportation. In addition, displacement of conventional energy strategies will impact emissions of pollutants directly influencing regional air quality (AQ) due to common generation processes and sources. The objective of this research is to quantify changes in pollutant emissions and the resulting regional AQ impacts in 2055 initiated by the implementation of alternative technologies and fuels targeting GHG emission reductions and the physical impacts of global climate change. Fundamentals central to the assessment include three quantitative analyses processes: (1) rigorous characterization of possible regional pollutant emission shifts resulting from technological perturbations associated with GHG mitigation, (2) determination of possible climate change impacts on regional AQ from physical effects, and (3) detailed regional AQ modeling to assess impacts on formation and fate of atmospheric chemical species of concern, including ozone (O3) and fine particulate matter (PM2.5). The ultimate goal of this work is to examine the physical effects of climate change on AQ and identify and characterize effective GHG mitigation strategies that can concurrently improve AQ.

Strategies to reduce GHG emissions in U.S. energy sectors can have positive and/or negative impacts on AQ. Shifts to alternative fuels and technologies can impact pollutant emissions quantitatively, spatially, temporally, and in composition, subsequently effecting concentrations of O3 and PM2.5. Some strategies will have clear GHG and AQ co-benefits (i.e. nuclear power, efficiency measures) in displacing traditional fossil fuels while others could reduce carbon emissions at the expense of increased atmospheric burdens of O3 and PM2.5 (i.e., CCS, ethanol). However, most strategies have a range of prospective AQ impacts varying in magnitude and controlled by characteristics of the utilized life cycle, e.g., fuel production pathways, complimentary technologies, conversion methods). Further, the formation and fate of secondary air pollutants is governed by complex, non-linear atmospheric processes. Thus, an in-depth understanding must be obtained regarding emissions from all life cycle stages of a technology or fuel followed by simulations of atmospheric chemistry and transport to properly evaluate AQ co-benefits of GHG mitigation strategies
 
To evaluate regional AQ impacts in 2055, emissions must be justifiably projected from current (2005) levels and spatially and temporally resolved to facilitate input into an advanced model of atmospheric chemistry and transport. Geographic regions selected for study include California (CA), an aggregate of five Northeastern U.S. states (NEUS), and Texas (TX) due to the regional nature of AQ coupled with significant differences in regional energy infrastructures (i.e., demands, utilized technologies and fuels). Baseline AQ is established in the year 2055 accounting for business-as-usual continuation of current technological, energy, and economic trends with a relative lack of GHG mitigation efforts via the output of a data-intensive, energy systems economic optimization model, the MARket ALlocation (MARKAL) model. Emissions are then grown to 2055 from current levels to reflect alterations to major sources projected in the Base Case and spatially and temporally resolved to account for direct perturbations using a widely accepted emissions processing tool, the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system. Finally, simulations of atmospheric processes are conducted using the Community Multi-scale Air Quality model (CMAQ) version 4.7, with the Carbon Bond 05 chemical mechanism to establish fully developed distributions of atmospheric concentrations of pollutants of interest, including ozone (O3) and fine particulate matter (PM2.5). In addition, AQ sensitivities to potential physical effects of global climate change are investigated.

Summary/Accomplishments (Outputs/Outcomes):

This research improves the understanding of how strategies can be developed to simultaneously address concerns regarding climate change and regional AQ with maximum effectiveness. First, we have assessed U.S. energy sectors, with an emphasis on power generation and transportation, for potential GHG and AQ impacts in the year 2055. Sectors and sources with high potential for impacts on O3 and PM2.5 are identified and assessed for potential mitigation strategy deployment. Second, we have evaluated the physical impacts of climate change on regional concentrations of O3 and PM.
 
· The transportation sector should be targeted with high priority for alternative technologies and fuels seeking GHG and pollutant emission reductions, with a particular focus on reducing precursor pollutants contributing to ground-level O3.
In order to evaluate impacts of regional energy systems development and identify emerging sources and sectors with high potential for AQ and GHG co-benefits, we have assessed the major U.S. energy sectors in 2055 for contributions to regional O3 and PM2.5 burdens. Figure 1 shows maximum 8-hr O3 difference plots for cases involving the removal of sector-wide emissions relative to baseline AQ. For all regions evaluated, removing transportation emissions contributes to the largest impacts on AQ, including reductions in ground-level O3. Impacts were significantly greater in magnitude (i.e. peak reductions 2 to 15 times) and spatial distribution than those from additional sectors. Additionally, transportation emissions contribute to the largest impacts on ambient PM2.5 concentrations in TX and CA. Further, areas of improvement are widespread and correspond to major urban populations and increased potential for human health benefits. Transportation sector results were consistent across all study areas despite significant regional variation in demands, technologies, and fuel; further indicating the importance to U.S. climate and AQ goals.

 

Figure 1 a
(a)
Figure 1 b
(b)
Figure 1 c
(c)
Figure 1 d
(d)
 
Figure 1: Impacts on maximum 8-hr O3 from the removal of emissions from the (a) Power, (b) Transportation, (c) Industrial, and (d) Commercial Sectors in the NEUS in 2055
· Maximizing AQ and GHG co-benefits from the power sector will be supported by high levels of nuclear power and renewables co-deployed with energy storage and smart grid technologies in tandem with aggressive energy efficiency and conservation strategies.
 
An initial first step to maximizing co-benefits should include aggressive pursuit of efficiency and conservation strategies. From solely an AQ and GHG standpoint alone, nuclear power should be expanded, particularly to offset current and/or future coal use in power generation and industrial sector activity. Additionally, renewable energy should also be pursued; however attention must be given to impacts from supporting technologies needed for optimal systems level operation, i.e., emissions from backup generators. In particular, some biopower energy strategies could yield dramatic GHG and AQ co-benefits if properly deployed. In contrast, carbon capture and storage technologies should be carefully deployed as the potential for emission cost and AQ worsening exists, particularly from large coal generators which currently represent the most cost effective deployment opportunity.
 
 
· Power generation sector GHG impacts are important in 2055; but AQ impacts require consideration of spatial characteristics for conclusions regarding significance to human health.
The power sector is responsible for the majority of regional GHG emissions in TX and is second to transportation in CA and the NEUS. Additionally, power generation emissions contribute significantly to regional O3 and PM2.5 concentrations, with impacts spatially characterized by plumes localized to major point sources (i.e., coal power plants in TX, gas-fired plants in CA) and extending downwind for a given meteorological episode. Impacts on PM2.5 are also significant, i.e., removing power emissions provides the largest reduction in the NEUS study region of any sector. However, sources of emissions, including generators comprising large point sources, can be located outside of population centers and the spatial specificity with which plumes impact communities must be evaluated in order to fully assess the importance of AQ impacts. Thus, GHG mitigation strategies are of particular importance for the power sector and large point sources should be considered a priority for both GHG and AQ improvements.
 
· The industrial sector should be considered with equivalent importance as power generation and transportation towards meeting future U.S. GHG and AQ goals.
Industrial sector activity contributes significantly to regional pollutant and GHG emissions in 2055 and resulting impacts on O3 and PM2.5 in all regions are comparable in scope and magnitude to those from power generation. Further, industrial sector sources contribute a non-trivial amount of GHG emissions to regional totals in 2055. Additionally, the current regulatory focus on reducing emissions from transportation and power generation will increase the relative importance of the industrial sector in future years. Thus, industrial source emissions should be considered with comparable importance in the development of GHG mitigation and AQ improvement planning that seeks to maximize co-benefits of energy sector emission reductions.
 
· In the absence of targeted elimination, coal power generation continues to dominate impacts on GHG and regional AQ, with nuclear power an optimal co-benefits mitigation strategy.
The use of coal for power generation in the TX and NEUS (CA includes very little coal) declines to 2055, largely as a result of an optimistic outlook for natural gas reserves in the Base Case. However, the remaining fraction of generation (i.e., 25% of TX generation) continues to emit a disproportionately large share of GHG and pollutants (i.e., 14% and 18% of total TX regional NOx and GHG emissions). It follows then that removing coal power plants yields large improvements in both GHG and regional AQ.
 
Two strategies were evaluated for co-benefit effectiveness due to similar power quality characteristic (i.e., base load), nuclear power and carbon capture and storage. Both were found to have high GHG mitigation attainment, however CCS slightly worsened AQ largely due to increase in NOx resulting from associated energy penalties. Figure 2 shows the difference in O3 and PM2.5 between the nuclear and CCS replacement cases in TX, including improvements for nuclear in some locations of 6 ppb peak O3 and over 2.0 24-h PM2.5 relative to CCS. Thus, nuclear generation represents an effective AQ and GHG co-benefit strategy in regions of the U.S. continuing to obtain sizable portions of electricity from coal.

 

Figure 2 a
(a)
Figure 2 b
(b)
 
Figure 2: Impacts on (a) Peak O3 and (b) 24-h average PM2.5 from replacement of coal power plants with nuclear power relative to the deployment of carbon capture and storage technologies
 
· Strategies to address light duty vehicle emission impacts in 2055 should prioritize GHG reductions and seek opportunities for deployment in urban locations.
The relative AQ impacts of LDVs decline from current levels, largely as a result of increased vehicle efficiencies fleet wide and, to a lesser degree, the modest deployment of electric vehicles. Removing LDV emissions in 2055 moderately reduces O3 and PM2.5 in study regions, i.e., peak O3 improvements of 2 to 6 ppb. Similarly, PM2.5 reductions are modest when viewed in the context of the enormous challenge and cost of complete fleet-wide emissions removal. This reflects the dramatic difference in pollutant emissions resulting from a regulatory focus on LDVs, e.g., an 85% reduction in fleet-wide NOx from current levels. However, AQ improvements generally occur in areas with dense populations, i.e., urban centers, and could have important health benefits. Additionally, GHG emissions from LDVs continue to be significant and represent a sector of importance for meeting climate change goals. Thus, strategies to mitigate LDV impacts can maximize co-benefits by focusing on deploying low carbon technologies and fuels, particularly in urban areas.

 

Figure 3 a
(a)
Figure 3 b
(b)
Figure 3 c
(c)
Figure 3 d
(d)
 
Figure 3: Impacts in CA on peak O3 from (a) LDV, (b) HDV, (c) Offroad, and (d) Marine and Rail Sources. **Scale normalized across cases
 
· In the Light Duty Vehicle (LDV) sector, hydrogen fuel cell vehicles and electric vehicles represent the paramount opportunity for achieving GHG and AQ co-benefits; however attainment will require the co-deployment of low emitting fueling pathways.
Our initial work on this project included an exhaustive review of reported literature regarding possible GHG mitigation strategies in the LDV sector, including the identification and assessment of alternative technologies and fuels for impacts on GHG emissions and regional burdens of O3 and PM2.5. Relative to current gasoline and diesel vehicles, HFCVs utilizing hydrogen produced from renewable pathways and BEVs operating on renewable or nuclear power achieve the largest reductions in GHGs and pollutant emissions. Additionally, even currently central fuel pathways (i.e., steam-methane reformation for H2, average regional power grid mixes) achieve significant co-benefits that can include reductions in regional O3 and PM2.5 levels. However, if high-emitting energy sources (i.e., coal, tar sands) are utilized in fuel production pathways, AQ and GHG co-benefits are significantly reduced for both strategies. Contrastingly, the use of ethanol could potentially worsen regional AQ and achieve minor GHG reductions or even increases if production pathways involving cereal crops are utilized.
 
In order to examine the impacts of transitioning to electricity as a LDV fuel in cases involving combinations of Battery Electric and Plug-in Hybrid Electric Vehicles were developed and evaluated for O3 and PM2.5. Cases involved various combinations of vehicle charging strategies, including the co-deployment of CCS in the power sector which could represent an outcome of high GHG mitigation at the cost of deleterious effects on AQ. In general, direct vehicle emission removal tend to dictate regional AQ impacts, with reductions generally having a higher magnitude and encompassing a greater area than any increases from power generators. However, the co-deployment of CCS with high penetrations of electric vehicles was shown to worsen O3 and PM2.5 significantly in areas localized to coal power plants (Figure 4) and such interactions should be considered for regions with significant coal generation.

 

Figure 4 a
(a)
Figure 4 b
(b)
 
Figure 4: Impacts on O3 for 30% battery electric and 30% plug-in hybrid electric 40 mile range vehicle deployment with charging demand met (a) without and (b) with the co-deployment of CCS
 
· The contribution to regional O3 and PM2.5 burdens from additional (non-light duty vehicle) transportation sub-sectors are extensive in 2055. In particular, emissions from offroad and marine sources should be targeted for emission reduction strategies.
We have examined the contributions to O3 and PM2.5 of various transportation sub-sectors (i.e., LDVs, HDVs, Offroad, Marine, Rail) and shown that mitigating impacts from non-LDVs will have high importance in 2055. In particular, emissions from marine vessels were associated with significant AQ impacts in all study regions, particularly in locations of major international shipping activity, i.e., Ports of L.A., Houston, and New York/New Jersey. Interestingly, ship emissions from inland waterways were also attributed with significant impacts, i.e., the Port of Pittsburgh. Additionally, offroad transportation sources were correlated with major contributions to O3 and PM2.5 levels, particularly downwind of major urban centers. Further, the importance of addressing emissions from all transportation sectors increases to 2055 due to the previously discussed evolution of the light duty vehicle sector.
 
· Addressing emissions from the Goods Movement sector is of high importance to AQ control strategies in 2055 and represents an important opportunity to achieve AQ and GHG co-benefits, particularly in urban regions supporting international shipping ports.
Our assessment of the impacts of various transportation sub-sectors demonstrated the importance of technologies utilized to transport goods (e.g., ships, heavy duty vehicles, offroad, rail) to regional AQ in 2055, including significant contributions to O3 and PM2.5 burdens in urban areas co-located with major shipping ports. Thus, we developed and evaluated scenarios accounting for emissions reduction strategies for relevant technologies in counties supporting high levels of goods transport. As can be seen, achieving a 25% reduction in activity corresponds to notable improvements in O3 and PM2.5, i.e., nearly 7 ppb and 4 μg/m3 in CA. The results demonstrate the importance of addressing the goods movement sector in future AQ control plans as well as the opportunity to achieve substantial GHG and AQ co-benefits from addressing emissions from associated technologies, including marine vessels.
 
· Targeted strategies to reduce the emissions from ocean going vessels can achieve significant reductions in CO2 in tandem with important improvements in regional O3 and PM2.5
Our work has demonstrated that in all regions the marine sector substantially impacts AQ in terms of both O3 and PM2.5. Using estimates from the International Maritime Organizations Second GHG study (IMO 2009) we find that maximum deployment of a wide range of efficiency improvement and emission reduction strategies significantly improves AQ in tandem with substantial CO2 reductions (i.e., the IMO reports up to 70% CO2 reductions). As can be seen in Figure 5 full deployment of strategies yields reductions in O3 that peak over 2 ppb in the NEUS and TX and impact large portions of both regions.
 

 

Figure 5 a
(a)
Figure 5 b
(b)
 
Figure 5: Impacts on max 8-hr O3 from advanced efficiency and pollutant control strategies for ships in (a) NEUS and (b) TX
 
· Petroleum-based transport fuel infrastructure contributes significantly to regional O3 and PM2.5 in 2055 and enhances the AQ benefits of transitioning to alternative transportation fuels
We found that emissions from the production, distribution, and storage of petroleum-based fuels contribute significantly to regional levels of O3 and PM2.5 in 2055 (Figure 6) and enhances the AQ benefits of transitioning to alternative transportation fuels. Further, areas most effected, e.g., localized to refineries adjacent to the Long Beach/ L.A. and Houston Ports, often coincide with communities currently experiencing serious deleterious health impacts from poor AQ. Thus, displacing petroleum refinery emissions represents an important opportunity to maximize the AQ benefits of alternative transportation technologies and fuels.
 

 

Figure 6 a
(a)
Figure 6 b
(b)
 
Figure 6: Impacts on (a) Peak O3 and (b) 24-h PM2.5 from emissions associated with petroleum fuel production in CA
 
· AQ sensitivity to long-term changes due to climate and background concentrations reiterates the need for climate change penalties in the assessment of air pollution control strategies.
Our results demonstrate that if climate change is not mitigated, further emission control strategies will have to be devised in order to offset the additional burden that climate change penalties will pose on regional AQ. The impacts of increasing temperatures over the entire US are shown in Figure 7. Increases in ozone due to 2 oC increase in temperature are in the order of 6-10 ppb in main metropolitan areas of the US. Additionally, the effect of amassed ammonia emissions due to increasing temperatures on PM2.5 concentration was shown that an increase of 10% in ammonia emissions caused by an increase of 2 oC could lead to increases of up to 1-3 g/m3 in PM2.5 concentrations. Further, the effects of a 4 oC increase could increase ammonia emissions by 27% yielding increases in PM2.5 on the order of 4 μg/m3. This level of sensitivity is of great concern, as it is comparable to the contribution of transportation and power generation in the study regions and supports the need for evaluating “climate change penalty” for future air pollution strategies.

 

Figure 7 a
(a)
Figure 7 b
(b)
 
Figure 7: Changes in pollutant concentrations due to an increase of 2 oC in temperature: (a) impact on peak 8-hour O3, (b) impact on 24-hour PM2.5 average
 

 

Conclusions:

 The transportation sector should be targeted with high priority for alternative technologies and fuels seeking GHG and pollutant emission reductions, with a particular focus on reducing precursor pollutants contributing to ground-level O3.

 Maximizing AQ and GHG co-benefits from the power sector will be supported by high levels of nuclear power and renewables co-deployed with energy storage and smart grid technologies in tandem with aggressive energy efficiency and conservation strategies.

 Power generation sector GHG impacts are important in 2055; but AQ impacts require consideration of spatial characteristics for conclusions regarding significance to human health.

 The industrial sector should be considered with equivalent importance as power generation and transportation towards meeting future U.S. GHG and AQ goals.

 In the absence of targeted elimination, coal power generation continues to dominate impacts on GHG and regional AQ, with nuclear power an optimal co-benefits mitigation strategy.

Strategies to address light duty vehicle emission impacts in 2055 should prioritize GHG reductions and seek opportunities for deployment in urban locations.

 In the Light Duty Vehicle (LDV) sector, hydrogen fuel cell vehicles and electric vehicles represent the paramount opportunity for achieving GHG and AQ co-benefits; however attainment will require the co-deployment of low emitting fueling pathways.

The contribution to regional O3 and PM2.5 burdens from additional (non-light duty vehicle) transportation sub-sectors are extensive in 2055. In particular, emissions from offroad and marine sources should be targeted for emission reduction strategies.

 Addressing emissions from the Goods Movement sector is of high importance to AQ control strategies in 2055 and represents an important opportunity to achieve AQ and GHG co-benefits, particularly in urban regions supporting international shipping ports.

 Targeted strategies to reduce the emissions from ocean going vessels can achieve significant reductions in CO2 in tandem with important improvements in regional O3 and PM2.5

Petroleum-based transport fuel infrastructure contributes significantly to regional O3 and PM2.5 in 2055 and enhances the AQ benefits of transitioning to alternative transportation fuels

AQ sensitivity to long-term changes due to climate and background concentrations reiterates the need for climate change penalties in the assessment of air pollution control strategies.

 


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Journal Article Mac Kinnon M, Shaffer B, Carreras-Sospedra M, Dabdub D, Samuelsen GS, Brouwer J. Air quality impacts of fuel cell electric hydrogen vehicles with high levels of renewable power generation. International Journal of Hydrogen Energy 2016;41(38):16592-16603. R834284 (Final)
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    • Supplemental Keywords:

    RFA, Air, climate change, Air Pollution Effects, Atmosphere, air quality modeling

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