Realistic operation of two residential cordwood-fired outdoor hydronic heater appliances—Part 3: Optical properties of black and brown carbon emissions

ABSTRACT

Residential biomass combustion is a source of carbonaceous aerosol. Inefficient combustion, particularly of solid fuels produces large quantities of black and brown carbon (BC and BrC). These particle types are important as they have noted effects on climate forcing and human health. One method of measuring these quantities is by measurement of aerosol light-absorption and scattering, which can be performed using an aethalometer and nephelometer, respectively. These instruments are widely deployed in the study of ambient air and are frequently used in air quality modeling and source apportionment studies. In this study, we will describe (1) a method for measuring primary BC and BrC emissions from two residential log-fired wood hydronic heaters and (2) the BC and BrC emission from these devices over a wide range of operating conditions, such as cold-starts, warm-starts, four different levels of output ranging from 15% to 100% maximum rated output, and periods of repeated cycling. The range in flue-gas BC concentrations, measured using an aethalometer at the 880 nanometer (nm) wavelength, were between 5.09 × 10² and 2.24 × 10⁴ micrograms per cubic meter (µg/m³) while the scattering coefficient of the flue-gas, measured by a nephelometer at 880 nm, ranged between 2.20 × 10³ and 8.56 × 10⁵ inverse megameters (Mm⁻¹). The BrC concentrations, measured using the 370 nm wavelength of an aethalometer, were between 9.10 × 10¹ and 3.56 × 10⁴ µg/m³. The calculated Angstrom Absorption Exponent (AAE) of the flue-gas aerosol ranged between 1.54 and 3.63. Performing a comparison between the measured BC concentration and an external particulate matter (PM) concentration showed that overall BC makes up roughly a quarter of the PM emitted by either of the two appliances. Further for both appliances, the cold-start and the test phase immediately following it had the highest BC and BrC concentrations, the highest measured scattering coefficient, as well as a low AAE.

Implications: In this work we provide information on the black and brown carbon emissions from outdoor cordwood-fired hydronic heaters. Aethalometer based black carbon measurements are common in atmospheric science, but are uncommonly used in laboratory studies. This work helps to bridge that gap. This data helps to inform the work of modelers and policy makers interested in hydronic heaters and source apportioning biomass combustion emissions.

Acknowledgment

The authors would like to acknowledge that the New York State Department of Health and in particular Patricia Fritz and Nicole Vitillo, everyone at the Energy Conversion Group at Brookhaven National Laboratory (BNL) for organizing the experiments and operating the appliances, and Northeast States for Coordinated Air Use Management (NESCAUM) for developing the test method used in this study. Financial support from New York State Energy Research Development Authority (NYSERDA) has made this work possible. This research was funded through NYSERDA Agreement 63033.

Data availability

The data that support the findings of this study are available from the corresponding author, JL, upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the New York State Energy Research and Development Authority [63033].

Notes on contributors

Jake Lindberg

Jake Lindberg is a recent doctoral graduate at Stony Brook University in the Chemical and Molecular Engineering Department in Stony Brook, New York, USA and works closely with the Energy Conversion Group, at Brookhaven National Laboratory in Upton, New York, USA.

Marilyn Wurth

Marilyn Wurth is a research scientist at the New York State Department of Environmental Conservation, in the Emissions Measurement Research Group within the Division of Air Resources, Bureau of Mobile Sources & Technology Development in Albany, New York, USA.

Brian P. Frank

Brian P. Frank is the section chief of the Emissions Measurement Research Group at the New York State Department of Environmental Conservation, Division of Air Resources, Bureau of Mobile Sources & Technology Development in Albany, New York, USA.

Shida Tang

Shida Tang is a research scientist at the New York State Department of Environmental Conservation, in the Emissions Measurement Research Group within the Division of Air Resources, Bureau of Mobile Sources & Technology Development in Albany, New York, USA.

Gil LaDuke

Gil LaDuke is a research scientist at the New York State Department of Environmental Conservation, in the Emissions Measurement Research Group within the Division of Air Resources, Bureau of Mobile Sources & Technology Development in Albany, New York, USA.

Rebecca Trojanowski

Rebecca Trojanowski is a research scientist at Brookhaven National Laboratory, in the Interdisciplinary Science Department, Energy Conversion Group, in Upton, New York, USA, and is a doctoral candidate at Columbia University in the Department of Earth and Environmental Engineering, in New York, New York, USA.

Thomas Butcher

Thomas Butcher is a research scientist at Brookhaven National Laboratory and is the leader of the Energy Conversion Group within the Interdisciplinary Science Department, in Upton, New York, USA.

Devinder Mahajan

Devinder Mahajan is a research professor in the Department of Materials Science and Chemical Engineering at State University of New York at Stony Brook in Stony Brook, New York, USA.