In-situ measurements of emissions and fuel loading of non-catalytic cordwood stoves in rural Oregon.

Abstract

Residential wood combustion is an important source of heat for millions of households, yet it represents the third largest source of PM_2.5 pollution in the United States. Development of cleaner-burning cordwood heating stove designs is necessary to reduce health and climate impacts from this important renewable energy source. Effective design requires an understanding of operation and performance of existing stoves in real-world settings. In this study, one uncertified stove, three EPA Phase I or II stoves, and three New Source Performance Standards (NSPS) stoves were sampled for 48 consecutive hours each in households in rural Oregon. The methodology included stack sampling of undiluted CO and CO₂ with a diluted sample train for cooling and condensation of PM and an optical sensor to apportion integrated gravimetric measurements of particle mass over time. A data-logging scale directly measured fuel loading mass and timing, enabling emissions mass calculations via both stack flow and carbon balance methods. Results across all stoves showed that together cold starts and reloads contribute 70% of total PM emissions. The measured period emission rate of PM over all stoves was 5.6 ± 2.2 g/hr, while the average emission factor of PM was 8.5 ± 3.0 g/kg. There was a statistically significant reduction of between 29.6-48.5% in the PM emission rate during all periods except burnout and a 40.6% increase in thermal efficiency of the NSPS stoves relative to the single uncertified stove during the fire period. Implications of this study include both a database of in-field emissions and efficiency performance measures and comparison of stove certification levels that are useful to wood stove designers and policymakers for optimizing air quality impacts of stove-user systems. In addition, the methods demonstrated here can be used by researchers to promote needed field monitoring capabilities at a lower cost and complexity.Result Detailed time-apportioned PM2.5 emissions data identified conditions leading to high emission rates such as startup, large loads, and operation of an uncertified stoveImplication Provides wood stove designers insights toward optimizing performance of future stove designs, and policy makers information about the impact of user and technology on air quality objectivesResult Demonstrated a new system of real-time emissions and fuel consumption monitoring equipment that enables time-resolved PM and direct fuel mass measurements to yield better insights and more robust data analysis.Implication This method can be used and/or modified by other researchers in this sector to promote much-needed field measurements at a lower cost and complexity than existing methods.