Characterization of biofuel emission profiles from in-use field tests and laboratory tests

YANJU CHEN (1), Tami C. Bond (1), Christoph A. Roden(1, 2), Nordica MacCarty (3)

(1) Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL (2) Now at SPEC Inc, Boulder, CO (3) Aprovecho Research, Creswell, OR

     Abstract Number: 391
     Last modified: May 11, 2010

Abstract
Carbonaceous aerosols are important to atmospheric chemistry and aerosol radiative effects because of their prevalence in both urban areas and continental flow. Globally, around 20% of primary carbonaceous aerosols are produced from biofuel combustion (biomass used for heating or cooking). However, emissions from biofuel combustion are large uncertainties in current models. Emission factors and aerosol properties applied in the models are usually taken from controlled laboratory tests, in which cooking stoves are operated based on prescribed operating conditions. These may not reproduce the variability of realistic in-use conditions, which in turn leads to variability in emission quantities and properties.

Our premise is that biofuel combustion is a sum of sequential combustion events, and that events can be classified into broad types by using real-time measurements. Relevant emission characteristics include optical variables (single scattering albedo, absorption Angstrom exponent), CO/CO2 ratio and estimates of instantaneous emission factors. High-frequency events are identified using frequency plots and cluster analysis was also employed to group events based on properties.

We present quantitative differences between three types of cookstoves (traditional, improved without chimney, and improved with chimney). High-emitting events are responsible for large fractions of particulate matter and smaller fractions of carbon monoxide. These high-emitting events are not present in controlled laboratory tests, explaining why laboratory tests produce much lower emission factors than in-field results. Laboratory evaluations of stove improvements should ensure that the modifications can reduce high-emitting events.