We analyze the spatial and technological distribution of China’s overseas electric power investments around the world, and the pollution intensity of Chinese coal fired power plants relative to those held by non-Chinese entities. We find that Chinese firms hold approximately $115 billion USD in electric power assets globally, with an average of 73% ownership stake in a total capacity of 81 GW. Chinese power investments span the globe but are largely found in developing countries, particularly in Asia and Latin America. The vast majority of Chinese investment goes to coal (24.5 GW), gas (20.5 GW) and hydropower (18.1 GW), while the share of wind (7.2 GW) and solar (3.1 GW) is relatively small but may be rising. The energy mix of Chinese overseas investment is similar to the existing world portfolio. Within the coal sector, between 2011 and 2017, the majority of Chinese greenfield investment in coal used supercritical technologies (58 percent) while only 34 percent of non-Chinese coal plants built during this period were supercritical.
Well plugging, the main strategy for reducing methane emissions from millions of unplugged abandoned oil and gas (AOG) wells in the U.S. and abroad, is expensive and many wells remain unplugged. In addition, plugging does not necessarily reduce methane emissions and some categories of plugged wells are high emitters. We analyze strategies and costs of five options for reducing methane emissions from high-emitting AOG wells - those which are unplugged and plugged/vented gas wells. The five options are: plugging without gas venting, plugging with gas venting and flaring, plugging with gas venting and usage, gas flaring only, and gas capture/usage only. Average plugging costs ($37,000 per well) can be justified by the social cost of methane, which considers air quality, climate, and human/ecosystem impacts. Savings as measured by natural gas prices and alternative energy credits can offset low plugging costs (<$15,400 per well) but are not large enough to offset average plugging costs. Nonetheless, reducing methane emissions from AOG wells is a cost-effective strategy for addressing climate change that has comparable costs to some current greenhouse gas mitigation options and can produce co-benefits such as groundwater protection. Therefore, we recommend including the mitigation of AOG wells in climate and energy policies in the U.S., Canada, and other oil-and-gas-producing regions.
Since 1850 the concentration of atmospheric methane (CH4), a potent greenhouse gas, has more than doubled. Recent studies suggest that emission inventories may be missing sources and underestimating emissions. To investigate whether offshore oil and gas platforms leak CH4during normal operation, we measured CH4 mole fractions around eight oil and gas production platforms in the North Sea which were neither flaring gas nor offloading oil. We use the measurements from summer 2017, along with meteorological data, in a Gaussian plume model to estimate CH4 emissions from each platform. We find CH4 mole fractions of between 11 and 370 ppb above background concentrations downwind of the platforms measured, corresponding to a median CH4 emission of 6.8 g CH4 s−1 for each platform, with a range of 2.9 to 22.3 g CH4 s−1. When matched to production records, during our measurements individual platforms lost between 0.04 % and 1.4 % of gas produced with a median loss of 0.23 %. When the measured platforms are considered collectively (i.e. the sum of platforms' emission fluxes weighted by the sum of the platforms' production), we estimate the CH4 loss to be 0.19 % of gas production. These estimates are substantially higher than the emissions most recently reported to the National Atmospheric Emission Inventory (NAEI) for total CH4 loss from United Kingdom platforms in the North Sea. The NAEI reports CH4 losses from the offshore oil and gas platforms we measured to be 0.13 % of gas production, with most of their emissions coming from gas flaring and offshore oil loading, neither of which was taking place at the time of our measurements. All oil and gas platforms we observed were found to leak CH4 during normal operation, and much of this leakage has not been included in UK emission inventories. Further research is required to accurately determine total CH4 leakage from all offshore oil and gas operations and to properly include the leakage in national and international emission inventories.
Solid fuel consumption and associated emissions from residential use are highly uncertain due to a lack of reliable statistics. In this study, we estimate solid fuel consumption and emissions from the rural residential sector in China by using data collected from a new nationwide field survey. We conducted a field survey in 2010 which covered ∼17,000 rural residential households in 183 counties in China, to obtain data for solid fuel consumption and use patterns. We then developed a Generalized Additive Model (GAM) to establish the relationship between solid fuel consumption and heating degree days (HDD), income, coal production, coal price, and vegetation coverage, respectively. The GAM was used to estimate solid fuel consumption in rural households in China at the county level. We estimated that, in 2010, 179.8Tg of coal were consumed in Chinese rural households for heating and cooking, which is 62% higher than that reported in official energy statistics. We found that large quantities of rural residential coal consumption in the North China Plain were underreported in energy statistics. For instance, estimated coal consumption in rural households in Hebei (one of most polluted provinces in China) was 20.8Tg in 2010, which is twice as high as government statistics indicate. In contrast, modeled national total consumption of crop residues (used as fuels) we found to be ∼50% lower than reported data. Combining the underlying data from the survey, the GAM and emission factors from literature, we estimate emissions from China’s rural residential sector in 2010 to be: 3.3Tg PM2.5, 0.6Tg BC, 1.2Tg OC, 2.1Tg VOC, 2.3Tg SO2, 0.4Tg NOx, 43.6Tg CO and 727.2Tg CO2, contributing to 29%, 35%, 38% and 26% of national total PM2.5, BC, OC, and CO emissions respectively. This work reveals that current emission inventories in China likely underestimate emissions from coal combustion in rural residential households due to missing coal consumption in official statistics, especially for the heavily polluted North China Plain (NCP) region. Per capita income appears to be the driving factor that results in the difference between surveyed data and official data. Residents with high income prefer commercial energy and have a higher per capita fuel consumption than lower income residents. Therefore, rural residential coal combustion may contribute even more to regional air pollution than the large contributions previously identified.
Black carbon (BC) mitigation can reduce adverse environmental impacts on climate, air quality, human health, and water resource availability. To facilitate the identification of mitigation priorities, we use a state-of-thescience global chemistry-climate coupled model (AM3), with additional tagged BC tracers representing regional (East Asia, South Asia, Europe and North America) and sectoral (land transport, residential, industry) anthropogenic BC emissions to identify sources with the largest impacts on air quality, human health and glacial deposition. We find that within each tagged region, domestic emissions dominate BC surface concentrations and associated premature mortality (generally over 90%), as well as BC deposition on glaciers (∼40–95% across glaciers). BC emissions occurring within each tagged source region contribute roughly 1–2 orders of magnitude more to their domestic BC concentrations, premature mortality, and BC deposition on regional glaciers than that caused by the same quantity of BC emitted from foreign regions. At the sectoral level, the South Asian residential sector contributes ∼60% of BC associated premature mortality in South Asia and ∼40–60% of total BC deposited on southern Tibetan glaciers. Our findings imply that BC mitigation within a source region, particularly from East and South Asian residential sectors, will bring the largest reductions in BC associated air pollution, premature mortality, and glacial deposition.
Recent studies have reported methane (CH4) emissions from abandoned and active oil and gas infrastructure across the United States, where measured emissions show regional variability. To investigate similar phenomena in West Virginia, we measure and characterize emissions from abandoned and active conventional oil and gas wells. In addition, we reconcile divergent regional CH4 emissions estimates by comparing our West Virginia emissions estimates with those from other states in the United States. We find the CH4 emission factors from 112 plugged and 147 unplugged wells in West Virginia are 0.1 g CH4 h−1 and 3.2 g CH4 h−1, respectively. The highest emitting unplugged abandoned wells in WV are those most recently abandoned, with the mean emission of wells abandoned between 1993 and 2015 of 16 g CH4 h−1 compared to the mean of those abandoned before 1993 of 3 × 10−3 g CH4 h−1. Using field observations at a historic mining area as a proxy for state-wide drilling activity in the late 19th/early 20th century, we estimate the number of abandoned wells in WV at between 60,000 and 760,000 wells. Methane emission factors from active conventional wells were estimated at 138 g CH4 h−1. We did not find an emission pattern relating to age of wells or operator for active wells, however, the CH4 emission factor for active conventional wells was 7.5 times larger than the emission factor used by the EPA for conventional oil and gas wells. Our results suggest that well emission factors for active and abandoned wells can vary within the same geologic formation and may be affected by differences in state regulations. Therefore, accounting for state-level variations is critical for accuracy in greenhouse gas emissions inventories, which are used to guide emissions reduction strategies.
Under the Paris Agreement, China committed to peak its carbon dioxide emissions on or before 2030. Substituting natural gas for coal may facilitate it meeting this commitment. However, three major challenges may obstruct progress towards desired climate benefits from natural gas. 1) A fundamental price dilemma disincentivizing a coal-to-gas end-use energy transition: low city-gate gas prices discourage an increase in gas supplies while high end-use gas prices impede an increase in gas demand. 2) Insufficient and constrained access to natural gas infrastructure hinders connections between gas supplies and end-users, and obstructs a balance in seasonal supply and demand. 3) Methane leakage from the natural gas industry compromises the direct greenhouse gas emission reductions from combustion. To address these challenges, government and industry must work together to facilitate natural gas market reform, increase investment in natural gas infrastructure, and control methane emissions.
Solar photovoltaic (PV) electricity generation can greatly reduce both air pollutant and greenhouse gas emissions compared to fossil fuel electricity generation. The Chinese government plans to greatly scale up solar PV installation between now and 2030. However, different PV development pathways will influence the range of air quality and climate benefits. Benefits depend on how much electricity generated from PV is integrated into power grids and the type of power plant displaced. Using a coal-intensive power sector projection as the base case, we estimate the climate, air quality, and related human health benefits of various 2030 PV deployment scenarios. We use the 2030 government goal of 400 GW installed capacity but vary the location of PV installation and the extent of inter-provincial PV electricity transmission. We find that deploying distributed PV in the east with inter-provincial transmission maximizes potential CO2 reductions and air quality-related health benefits (4.2% and 1.2% decrease in national total CO2 emissions and air pollution-related premature deaths compared to the base case, respectively). Deployment in the east with inter-provincial transmission results in the largest benefits because it maximizes displacement of the dirtiest coal-fired power plants and minimizes PV curtailment, which is more likely to occur without inter-provincial transmission. We further find that the maximum co-benefits achieved with deploying PV in the east and enabling inter-provincial transmission are robust under various maximum PV penetration levels in both provincial and regional grids. We find large potential benefits of policies that encourage distributed PV deployment and facilitate inter-provincial PV electricity transmission in China.
Electrification with decarbonized electricity is a central strategy for carbon mitigation. End-use electrification can also reduce air pollutant emissions from the demand sectors, which brings public health co-benefits. Here we focus on electrification strategies for China, a country committed to both reducing air pollution and peaking carbon emissions before 2030. Considering both coal-intensive and decarbonized power system scenarios for 2030, we assess the air quality, health and climate co-benefits of various end-use electrification scenarios for the vehicle and residential sectors relative to a non-electrified coal-intensive business-as-usual scenario (BAU). Based on an integrated assessment using the regional air pollution model WRF-Chem and epidemiological concentration–response relationships, we find that coal-intensive electrification (75% coal) does not reduce carbon emissions, but can bring significant air quality and health benefits (41,000–57,000 avoided deaths in China annually). In comparison, switching to a half decarbonized power supply (∼50% coal) for electrification of the transport and/or residential sectors leads to a 14–16% reduction in carbon emissions compared to BAU, as well as greater air quality and health co-benefits (55,000–69,000 avoided deaths in China annually) than coal intensive electrification. Furthermore, depending on which end-use sector is electrified, we find different regional distributions of air quality and health benefits. While electrifying the transport sector improves air quality throughout eastern China, electrifying the residential sector brings most benefits to the North China Plain region in winter where coal-based heating contributes substantially to air pollution.
Both energy production and consumption can simultaneously affect regional air quality, local water stress and the global climate. Identifying the air quality–carbon–water interactions due to both energy sources and end-uses is important for capturing potential co-benefits while avoiding unintended consequences when designing sustainable energy transition pathways. Here, we examine the air quality–carbon–water interdependencies of China’s six major natural gas sources and three end-use gasfor-coal substitution strategies in 2020. We find that replacing coal with gas sources other than coal-based synthetic natural gas (SNG) generally offers national air quality–carbon–water co-benefits. However, SNG achieves air quality benefits while increasing carbon emissions and water demand, particularly in regions that already suffer from high per capita carbon emissions and severe water scarcity. Depending on end-uses, non-SNG gas-for-coal substitution results in enormous variations in air quality, carbon and water improvements, with notable air quality–carbon synergies but air quality–water trade-offs. This indicates that more attention is needed to determine in which end-uses natural gas should be deployed to achieve the desired environmental improvements. Assessing air quality–carbon–water impacts across local, regional and global administrative levels is crucial for designing and balancing the co-benefits of sustainable energy development and deployment policies at all scales.
China needs to manage its coal-dominated power system to curb carbon emissions, as well as to address local environmental priorities such as air pollution and water stress. Here we examine three province-level scenarios for 2030 that represent various electricity demand and low-carbon infrastructure development pathways. For each scenario, we optimize coal power generation strategies to minimize the sum of national total coal power generation cost, inter-regional transmission cost and air pollution and water costs. We consider existing environmental regulations on coal power plants, as well as varying prices for air pollutant emissions and water to monetize the environmental costs. Comparing 2030 to 2015, we find lower CO2 emissions only in the scenarios with substantial renewable generation or low projected electricity demand. Meanwhile, in all three 2030 scenarios, we observe lower air pollution and water impacts than were recorded in 2015 when current regulations and prices for air pollutant emissions and water are imposed on coal power plants. Increasing the price of air pollutant emissions or water alone can lead to a tradeoff between these two objectives, mainly driven by differences between air pollution-oriented and water-oriented transmission system designs that influence where coal power plants will be built and retired.
To increase energy security and reduce emissions of air pollutants and CO2from coal use, China is attempting to duplicate the rapid development of shale gas that has taken place in the United States. This work builds a framework to estimate the lifecycle greenhouse gas (GHG) emissions from China’s shale gas system and compares them with GHG emissions from coal used in the power, residential, and industrial sectors. We find the mean lifecycle carbon footprint of shale gas is about 30–50% lower than that of coal in all sectors under both 20 year and 100 year global warming potentials (GWP20 and GWP100). However, primarily due to large uncertainties in methane leakage, the upper bound estimate of the lifecycle carbon footprint of shale gas in China could be approximately 15–60% higher than that of coal across sectors under GWP20. To ensure net GHG emission reductions when switching from coal to shale gas, we estimate the breakeven methane leakage rates to be approximately 6.0%, 7.7%, and 4.2% in the power, residential, and industrial sectors, respectively, under GWP20. We find shale gas in China has a good chance of delivering air quality and climate cobenefits, particularly when used in the residential sector, with proper methane leakage control.
Black carbon (BC) aerosol strongly absorbs solar radiation, which warms climate. However, accurate estimation of BC’s climate effect is limited by the uncertainties of its spatiotemporal distribution, especially over remote oceanic areas. The HIAPER Pole-to-Pole Observation (HIPPO) program from 2009 to 2011 intercepted multiple snapshots of BC profiles over Pacific in various seasons, and revealed a 2 to 5 times overestimate of BC by current global models. In this study, we compared the measurements from aircraft campaigns and satellites, and found a robust association between BC concentrations and satellite-retrieved CO, tropospheric NO2, and aerosol optical depth (AOD) (R2>0.8). This establishes a basis to construct a satellite-based column BC approximation (sBC*) over remote oceans. The inferred sBC* shows that Asian outflows in spring bring much more BC aerosols to the midPacific than those occurring in other seasons. In addition, inter-annual variability of sBC* is seen over the Northern Pacific, with abundances varying consistently with the springtime Pacific/North American (PNA) index. Our sBC* dataset infers a widespread overestimation of BC loadings and BC Direct Radiative Forcing by current models over North Pacific, which further suggests that large uncertainties exist on aerosol-climate interactions over other remote oceanic areas beyond Pacific.
Ground-level ozone (O3), harmful to most living things, is produced from both domestic and foreign emissions of anthropogenic precursors. Previous estimates of the linkage from distant sources rely on the sensitivity approach (i.e., modeling the change of ozone concentrations that result from modifying precursor emissions) as well as the tagging approach (i.e., tracking ozone produced from specific O3 precursors emitted from one region). Here, for the first time, we tag all O3 precursors (i.e., nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs)) from East Asia and explicitly track their physicochemical evolution without perturbing the nonlinear O3 chemistry. We show that, even in summer, when intercontinental influence on ozone has typically been found to be weakest, nearly 3 parts per billion by volume (ppbv) seasonal average surface O3 over North America can be attributed to East Asian anthropogenic emissions, compared with 0.7 ppbv using the sensitivity approach and 0.5 ppbv by tagging reactive nitrogen oxides. Considering the acute effects of O3 exposure, approximately 670 cardiovascular and 300 respiratory premature mortalities within North America could be attributed to East Asia. CO and longer-lived VOCs, largely overlooked in previous studies, extend the influence of regional ozone precursors emissions and, thus, greatly enhance O3 attribution to source region.
China is the world's top carbon emitter and suffers from severe air pollution. We examine near-term air quality and CO2 co-benefits of various current sector-based policies in China. Using a 2015 base case, we evaluate the potential benefits of four sectoral mitigation strategies. All scenarios include a 20% increase in conventional air pollution controls as well as the following sector-specific fuel switching or technology upgrade strategies. Power sector (POW): 80% replacement of small coal power plants with larger more efficient ones; Industry sector (IND): 10% improvement in energy efficiency; Transport sector (TRA): replacement of high emitters with average vehicle fleet emissions; and Residential sector (RES): replacement of 20% of coal-based stoves with stoves using liquefied petroleum gas (LPG). Conducting an integrated assessment using the regional air pollution model WRFChem, we find that the IND scenario reduces national air-pollution-related deaths the most of the four scenarios examined (27,000, 24,000, 13,000 and 23,000 deaths reduced annually in IND, POW, TRA and RES, respectively). In addition, the IND scenario reduces CO2 emissions more than 8 times as much as any other scenario (440, 53, 0 and 52 Mt CO2 reduced in IND, POW, TRA and RES, respectively). We also examine the benefits of an industrial efficiency improvement of just 5%. We find the resulting air quality and health benefits are still among the largest of the sectoral scenarios, while the carbon mitigation benefits remain more than 3 times larger than any other scenario. Our analysis hence highlights the importance of even modest industrial energy efficiency improvements and air pollution control technology upgrades for air quality, health and climate benefits in China.
China is the world’s top carbon emitter and suffers from severe air pollution. It has recently made commitments to improve air quality and to peak its CO2 emissions by 2030. We examine one strategy that can potentially address both issues—utilizing long-distance electricity transmission to bring renewable power to the polluted eastern provinces. Based on an integrated assessment using state-of-the-science atmospheric modeling and recent epidemiological evidence, we find that transmitting a hybrid of renewable (60%) and coal power (40%) (Hybrid-by-wire) reduces 16% more national air-pollution-associated deaths and decreases three times more carbon emissions than transmitting only coal-based electricity. Moreover, although we find that transmitting coal power (Coal-by-Wire, CbW) is slightly more effective at reducing air pollution impacts than replacing old coal power plants with newer cleaner ones in the east (Coal-by-Rail, CbR) (CbW achieves a 6% greater reduction in national total air-pollution-related mortalities than CbR), both coal scenarios have approximately the same carbon emissions. We thus demonstrate that coordinating transmission planning with renewable energy deployment is critical to maximize both local air quality benefits and global climate benefits.
Facing severe air pollution and growing dependence on natural gas imports, the Chinese government plans to increase coal-based synthetic natural gas (SNG) production. Although displacement of coal with SNG benefits air quality, it increases CO2 emissions. Due to variations in air pollutant and CO2 emission factors and energy efficiencies across sectors, coal replacement with SNG results in varying degrees of air quality benefits and climate penalties. We estimate air quality, human health, and climate impacts of SNG substitution strategies in 2020. Using all production of SNG in the residential sector results in an annual decrease of ∼32,000 (20,000 to 41,000) outdoor-air-pollutionassociated premature deaths, with ranges determined by the low and high estimates of the health risks. If changes in indoor/household air pollution were also included, the decrease would be far larger. SNG deployment in the residential sector results in nearly 10 and 60 times greater reduction in premature mortality than if it is deployed in the industrial or power sectors, respectively. Due to inefficiencies in current household coal use, utilization of SNG in the residential sector results in only 20 to 30% of the carbon penalty compared with using it in the industrial or power sectors. Even if carbon capture and storage is used in SNG production with today’s technology, SNG emits 22 to 40% more CO2 than the same amount of conventional gas. Among the SNG deployment strategies we evaluate, allocating currently planned SNG to households provides the largest air quality and health benefits with the smallest carbon penalties
Solar photovoltaic (PV) electricity generation is expanding rapidly in China, with total capacity projected to be 400 GW by 2030. However, severe aerosol pollution over China reduces solar radiation reaching the surface. We estimate the aerosol impact on solar PV electricity generation at the provincial and regional grid levels in China. Our approach is to examine the 12-year (2003–2014) average reduction in point-of-array irradiance (POAI) caused by aerosols in the atmosphere. We apply satellite-derived surface irradiance data from the NASA Clouds and the Earth’s Radiant Energy System (CERES) with a PV performance model (PVLIB-Python) to calculate the impact of aerosols and clouds on POAI. Our findings reveal that aerosols over northern and eastern China, the most polluted regions, reduce annual average POAI by up to 1.5 kWh/m2 per day relative to pollution-free conditions, a decrease of up to 35%. Annual average reductions of POAI over both northern and eastern China are about 20–25%. We also evaluate the seasonal variability of the impact and find that aerosols in this region are as important as clouds in winter. Furthermore, we find that aerosols decrease electricity output of tracking PV systems more than those with fixed arrays: over eastern China, POAI is reduced by 21% for fixed systems at optimal angle and 34% for two-axis tracking systems. We conclude that PV system performance in northern and eastern China will benefit from improvements in air quality and will facilitate that improvement by providing emission-free electricity.
Climate change can influence fine particulate matter concentrations (PM2.5) through changes in air pollution meteorology. Knowledge of the extent to which climate change can exacerbate or alleviate air pollution in the future is needed for robust climate and air pollution policy decision-making. To examine the influence of climate on PM2.5, we use the Geophysical Fluid Dynamics Laboratory Coupled Model version 3 (GFDL CM3), a fully-coupled chemistry-climate model, combined with future emissions and concentrations provided by the four Representative Concentration Pathways (RCPs). For each of the RCPs, we conduct future simulations in which emissions of aerosols and their precursors are held at 2005 levels while other climate forcing agents evolve in time, such that only climate (and thus meteorology) can influence PM2.5 surface concentrations. We find a small increase in global, annual mean PM2.5 of about 0.21 μg m−3 (5%) for RCP8.5, a scenario with maximum warming. Changes in global mean PM2.5 are at a maximum in the fall and are mainly controlled by sulfate followed by organic aerosol with minimal influence of black carbon. RCP2.6 is the only scenario that projects a decrease in global PM2.5 with future climate changes, albeit only by −0.06 μg m−3 (1.5%) by the end of the 21st century. Regional and local changes in PM2.5 are larger, reaching upwards of 2 μg m−3 for polluted (eastern China) and dusty (western Africa) locations on an annually averaged basis in RCP8.5. Using multiple linear regression, we find that future PM2.5 concentrations are most sensitive to local temperature, followed by surface wind and precipitation. PM2.5 concentrations are robustly positively associated with temperature, while negatively related with precipitation and wind speed. Present-day (2006–2015) modeled sensitivities of PM2.5 to meteorological variables are evaluated against observations and found to agree reasonably well with observed sensitivities (within 10–50% over the eastern United States for several variables), although the modeled PM2.5 is less sensitive to precipitation than in the observations due to weaker convective scavenging. We conclude that the hypothesized “climate penalty” of future increases in PM2.5 is relatively minor on a global scale compared to the influence of emissions on PM2.5concentrations.
As part of the 12th Five-Year Plan, the Chinese government has developed air pollution prevention and control plans for key regions with a focus on the power, transport, and industrial sectors. Here, we investigate the contribution of residential emissions to regional air pollution in highly polluted eastern China during the heating season, and find that dramatic improvements in air quality would also result from reduction in residential emissions. We use the Weather Research and Forecasting model coupled with Chemistry to evaluate potential residential emission controls in Beijing and in the Beijing, Tianjin, and Hebei (BTH) region. In January and February 2010, relative to the base case, eliminating residential emissions in Beijing reduced daily average surface PM2.5 (particulate mater with aerodynamic diameter equal or smaller than 2.5 micrometer) concentrations by 14 ± 7 μg·m−3 (22 ± 6% of a baseline concentration of 67 ± 41 μg·m−3 ; mean ± SD). Eliminating residential emissions in the BTH region reduced concentrations by 28 ± 19 μg·m−3 (40 ± 9% of 67 ± 41 μg·m−3 ), 44 ± 27 μg·m−3 (43 ± 10% of 99 ± 54 μg·m−3 ), and 25 ± 14 μg·m−3 (35 ± 8% of 70 ± 35 μg·m−3 ) in Beijing, Tianjin, and Hebei provinces, respectively. Annually, elimination of residential sources in the BTH region reduced emissions of primary PM2.5 by 32%, compared with 5%, 6%, and 58% achieved by eliminating emissions from the transportation, power, and industry sectors, respectively. We also find air quality in Beijing would benefit substantially from reductions in residential emissions from regional controls in Tianjin and Hebei, indicating the value of policies at the regional level.