Emission factors of fine particulate matter, organic and elemental carbon, carbon monoxide, and carbon dioxide for four solid fuels commonly used in residential heating by the U.S. Navajo Nation

ABSTRACT

Most homes in the Navajo Nation use wood as their primary heating fuel, often in combination with locally mined coal. Previous studies observed health effects linked to this solid-fuel use in several Navajo communities. Emission factors (EFs) for common fuels used by the Navajo have not been reported using a relevant stove type. In this study, two softwoods (ponderosa pine and Utah juniper) and two high-volatile bituminous coals (Black Mesa and Fruitland) were tested with an in-use residential conventional wood stove (homestove) using a modified American Society for Testing and Materials/U.S. Environmental Protection Agency (ASTM/EPA) protocol. Filter sampling quantified PM_2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) and organic (OC) and elemental (EC) carbon in the emissions. Real-time monitoring quantified carbon monoxide (CO), carbon dioxide (CO₂), and total suspended particles (TSP). EFs for these air pollutants were developed and normalized to both fuel mass and energy consumed. In general, coal had significantly higher mass EFs than wood for all pollutants studied. In particular, coal emitted, on average, 10 times more PM_2.5 than wood on a mass basis, and 2.4 times more on an energy basis. The EFs developed here were based on fuel types, stove design, and operating protocols relevant to the Navajo Nation, but they could be useful to other Native Nations with similar practices, such as the nearby Hopi Nation.

Implications: Indoor wood and coal combustion is an important contributor to public health burdens in the Navajo Nation. Currently, there exist no emission factors representative of Navajo homestoves, fuels, and practices. This study developed emission factors for PM_2.5, OC, EC, CO, and CO₂ using a representative Navajo homestove. These emission factors may be utilized in regional-, national-, and global-scale health and environmental models. Additionally, the protocols developed and results presented here may inform on-going stove design of the first EPA-certified wood and coal combination stove.

Acknowledgment

We thank the Mortenson Center for Engineering in Developing Communities for their assistance with facility funding. We are very grateful to Royce Brady and his family for providing the homestove and to Perry Charley and Dr. Donald Robinson for providing fuels used in this study.

Funding

This work was partially supported by the National Science Foundation (award 0946502), as well as the Discovery Learning Apprenticeship (DLA) and the Department of Civil, Environment, and Architectural Engineering’s Dissertation Completion Fellowship at the University of Colorado Boulder.

Supplemental data

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was partially supported by the National Science Foundation (award 0946502), as well as the Discovery Learning Apprenticeship (DLA) and the Department of Civil, Environment, and Architectural Engineering’s Dissertation Completion Fellowship at the University of Colorado Boulder.

Notes on contributors

Wyatt M. Champion

Wyatt M. Champion, Ph.D., is a graduate student, Lea Connors is an undergraduate student, and Lupita D. Montoya, Ph.D., is an assistant professor at the Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO, USA.