Air Pollution Science & Technology

TABLE OF CONTENTS

Air Quality Impacts of Heavy Duty Trucks
Measuring Black Carbon Emissions
Anaerobic Digestion of Municipal Solid Waste-to-Energy
Black and Brown Carbon
Black Carbon Trends

Understanding Air Quality Impacts of Heavy-Duty Trucks

Measuring the effects of particle filters and selective catalytic reduction

Heavy-duty vehicles play a vital role in the transport of freight. To minimize the air-quality impacts associated with freight movement, the Environmental Protection Agency (EPA) sets increasingly stringent emission standards for new heavy-duty trucks. California has accelerated adoption of after-treatment emission reduction technologies — namely diesel particle filters and selective catalytic reduction — through regulations that apply to trucks operating at ports and intermodal freight-handling facilities and trucks and buses operating throughout the state.

With support from the California Air Resources Board and the Bay Area Air Quality Management District, Berkeley Lab Senior Scientist Tom Kirchstetter — also an associate professor at UC Berkeley — is leading research to measure the effects of particle filters and selective catalytic reduction on in-use heavy-duty diesel truck emissions of gaseous and particulate pollutants. UC Berkeley Graduate Student Chelsea Preble recently published observations of reductions in black carbon and nitrogen oxide emissions but increases in nitrogen dioxide emissions associated with increasing use of these technologies. Prior research has tracked emissions over time from cars and trucks, including the emission impacts of changes to fuel composition. A related study quantified black carbon emission rates from passenger locomotive engines in California and their carbon footprint.

Measuring Black Carbon Emissions

Black carbon emissions from fossil and biomass fuel combustion pose a health concern to urban and rural communities in developed and developing regions. Black carbon emissions also absorb sunlight in the atmosphere and when deposited on snow and ice, and contribute to climate change with a radiative forcing on par with methane.

The spatial distribution of black carbon in the atmosphere is heterogeneous, which makes it difficult to assess personal exposures and climate impacts. Professor Kirchstetter's research group is in the midst of an effort to fill some key missing pieces. These include the development of a very small and low-cost black carbon sensor (pictured above) and the creation of a first-of-its kind community black carbon air quality network. Leading this work with Kirchstetter are graduate students Julien Caubel and Chelsea Preble and UCB's research specialist Troy Cados.

Partnering with the West Oakland Environmental Indicators Project (WOEIP), the Environmental Defense Fund, and with support of the Bay Area Air Quality Management District, the UC Berkeley research team is leading a study of the spatial and temporal patterns of black carbon air pollution in West Oakland. The study — called the 100 x 100 West Oakland Community Air Quality Study — aims to establish and operate a network of 100 black carbon sensors for 100 days. The goal is to provide a better understanding of how black carbon from diesel engines and other sources vary within the residential community, and with distance from freeways and commercial corridors. The study provides an opportunity to evaluate the benefits of a network of air pollution sensors dispersed within a community over the traditional approach of monitoring air pollution at centrally located sites.

Related research includes a pilot project that measured vertical profiles of black carbon in the troposphere using a balloon-borne platform (preliminary findings), the first thermal spectral-optical analysis method (1), and an evaluation of the loading artifact that affects black carbon measurements made with aethalometers.

Anaerobic Digestion of Municipal Solid Waste-to-Energy

UC Berkeley and Lawrence Berkeley National Lab, supported by the California Energy Commission, are partnering with the Zero Waste Energy Development Company (ZWEDC) to better quantify the emissions benefits and policy and economic barriers to converting organic municipal solid waste to energy. ZWEDC operates the world's largest anaerobic digestion facility in the world. Diversion of waste for the anaerobic production of biogas reduces landfill methane emissions (which comprise 20% of California's anthropogenic methane inventory), supports municipal "zero-waste" goals, and helps California build its renewable energy portfolio.

The research team is quantifying emissions of greenhouse gases, odorous compounds, and other air pollutants associated with anaerobic digestion, conversion of biogas to electricity, and composting processes; conducting life-cycle cost, energy and greenhouse gas assessments to enable maximum economic and environmental performance of waste-to-energy facilities; and evaluating policy and economic barriers that inhibit scale-up and additional net energy export.

Black and Brown Carbon

Sunlight absorbing aerosols produced from fossil and biomass burning perturb earth's radiation balance with space. Several studies of absorption selectivity (the dependence of absorption on wavelength) have demonstrated that primary organic aerosol (POA) produced from biomass burning — including wildfires over southern Africa, residential fireplaces, and biomass cookstoves — is a significant contributor to aerosol absorption of sunlight in the atmosphere (1, 2, 3, 4).

On the earth's surface, black carbon continues to interact with sunlight. Professor Kirchstetter and former Ernest Orlando Lawrence Postdoctoral Fellow, Odelle Hadley, conducted a laboratory study of home-made sooty snow and characterized the albedo reduction as a function of black carbon contamination level and snow grain size (summary and publication).

Related research conducted at Berkeley Lab on the loss of solar reflectance of roofs led to a method for accelerated soiling of roofing products that mimics reflectance loss due to natural exposure (1, 2) and a 2016 R&D 100 Award in 2016 for the "Cool Roof Time Machine." Check out Berkeley Lab's Heat Island Group website for more information about this and other cool projects.

Black Carbon Trends

Long-term pollutant concentration trends can be useful for evaluating air quality effects of emission controls and historical transitions in energy sources. A recent study employed archival records of coefficient of haze (COH), a now-retired measure of light-absorbing particulate matter, to re-construct historical black carbon concentrations at urban locations in the United States. Estimated BC concentrations in ten states stretching from the East to West Coast decreased markedly between 1965 and 1980: 5-fold in Illinois, Ohio, and Virginia, 4-fold in Missouri, and 2.5-fold in Pennsylvania. Over the period from the mid-1960s to the early 2000s, annual average black carbon concentrations in New Jersey and California decreased from 13 to 2 µg m³ and 4 to 1 µg m³ , respectively, despite concurrent increases in fossil fuel consumption from 1.6 to 2.1 EJ in New Jersey and 4.2 to 6.4 EJ in California. New Jersey's greater reliance on black carbon-producing heavy fuel oils and coal in the 1960s and early 1970s and subsequent transition to cleaner fuels explains why the decrease was larger in New Jersey than California. Over the period of study, declining concentrations of black carbon, a potent and shortlived climate warming pollutant, contrast increasing fossil fuel CO₂ emissions in the U.S.